U.S. patent application number 10/781767 was filed with the patent office on 2004-08-19 for engine emission analyzer.
This patent application is currently assigned to Oasis Emission Consultants Inc.. Invention is credited to Knott, Christopher Norman, Knott, Norman Sydney.
Application Number | 20040159142 10/781767 |
Document ID | / |
Family ID | 32044809 |
Filed Date | 2004-08-19 |
United States Patent
Application |
20040159142 |
Kind Code |
A1 |
Knott, Christopher Norman ;
et al. |
August 19, 2004 |
Engine emission analyzer
Abstract
A method for analyzing the exhaust emissions of large industrial
engines that: produces emission information in real time and
permits the generation of test results immediately after an
emission test is conducted, is disclosed. The method includes the
real time calculation of exhaust volumetric flow rate from fuel gas
flowrate and the use of real time intake manifold conditions to
determine engine load from an engine load curve. A portable
apparatus for performing the method, comprising a programmed
computer, data collection buffer, computer readable database and
display device is also disclosed.
Inventors: |
Knott, Christopher Norman;
(Rock Springs, WY) ; Knott, Norman Sydney;
(Creston, CA) |
Correspondence
Address: |
BARRIGAR INTELLECTUAL PROPERTY GROUP
290 - 1675 DOUGLAS STREET
VICTORIA
BC
V8W 2G5
CA
|
Assignee: |
Oasis Emission Consultants
Inc.
Calgary
CA
|
Family ID: |
32044809 |
Appl. No.: |
10/781767 |
Filed: |
February 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10781767 |
Feb 20, 2004 |
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10057379 |
Nov 20, 2001 |
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6721649 |
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60249436 |
Nov 20, 2000 |
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Current U.S.
Class: |
73/23.32 ;
702/24 |
Current CPC
Class: |
G01M 15/102
20130101 |
Class at
Publication: |
073/023.32 ;
702/024 |
International
Class: |
G06G 007/70; G01N
007/00 |
Claims
What is claimed is:
1. A method for determining the emission rate of a selected test
gas emitted in the exhaust gas of a gas-fueled engine, the method
comprising the steps of: (A) measuring the relative concentration
of a test gas in the exhaust gas; (B) measuring each of fuel-gas
flowrate, fuel-gas temperature and fuel-gas pressure; (C) computing
a volumetric flowrate of the exhaust gas from the fuel-gas
flowrate, temperature and pressure measurements; and (D) computing
a test gas emission rate from the calculated volumetric flowrate of
the exhaust gas and measurement of relative concentration of the
test gas; wherein steps C and D, are performed in real time by a
suitably-programmed digital computer.
2. The method of claim 1, further comprising the step of sending
the computed test gas emission rate to a display device.
3. The method of claim 1, wherein the steps of the method are
repeated at a selected time interval a selected number of times so
as to calculate a series of test gas emission test data.
4. The method of claim 3, further comprising the step of sending
the measurements to a computer-readable database for subsequent
preparation of a formal emission report.
5. The method of claim 1, further comprising the steps of: (A)
obtaining from a computer-readable database: (i) a measurement of
the ambient pressure; (ii) an instantaneous compressibility factor
for the fuel gas; (iii) a gross calorific value for the fuel gas;
and (iv) a dry fuel F factor for the fuel gas; and (B) measuring
the relative concentration of O.sub.2 in the exhaust gas; wherein,
the step of computing a volumetric flowrate of the exhaust gas from
the fuel-gas flowrate, temperature and pressure measurements,
includes using the measurements of ambient pressure; instantaneous
compressibility factor for the fuel gas; gross calorific value for
the fuel gas; dry fuel F factor for the fuel gas; and relative
concentration of O.sub.2 in the exhaust gas, to calculate the
volumetric flowrate of the exhaust gas.
6. The method of claim 1, further comprising the step of obtaining
a fuel-gas flowrate measurement conversion factor; and wherein the
step of computing a volumetric flowrate of the exhaust gas from the
fuel-gas flowrate, temperature and pressure measurements, includes
using the fuel-gas flowrate measurement conversion factor to
calculate the volumetric flowrate of the exhaust gas.
7. The method of claim 1 for use with an engine having an intake
manifold, the method further comprising the steps of: (A) measuring
in real time each of intake manifold temperature and intake
manifold pressure; (B) determining the engine load from the
measurements of intake manifold temperature and intake manifold
pressure, and an engine load curve; and (C) calculating in real
time an emission rate per engine load using the computed test gas
emission rate and the engine load.
8. The method of claim 7, further comprising the steps of: (A)
obtaining engine data from a computer-readable database; and (B)
selecting an appropriate engine load curve from a plurality of
engine load curves based on the engine data.
9. A method for determining the emission rate of a selected test
gas emitted in the exhaust gas of a gas-fueled engine, the method
comprising the steps of: (A) obtaining: (i) a measurement of the
ambient pressure; (ii) an instantaneous compressibility factor for
the fuel gas; (iii) a gross calorific value for the fuel gas; and
(iv) a dry fuel F factor for the fuel gas; (B) receiving real-time
measurements of the: (i) relative concentration of the test gas in
the exhaust gas; (ii) relative concentration of O.sub.2 in the
exhaust gas; (iii) flow rate of the fuel gas; (iv) temperature of
the fuel gas; and (v) pressure of the fuel gas; (C) calculating in
real time a dry volumetric flow rate of the fuel gas from the flow
rate of the fuel gas, the fuel-gas temperature, the fuel-gas
pressure, the ambient pressure and the instantaneous
compressibility factor of the fuel gas; (D) calculating in real
time the volumetric flow rate of the exhaust gas from the dry
volumetric flow rate of the fuel gas, the dry fuel F factor, the
gross calorific value of the fuel gas and the relative
concentration of O.sub.2 in the exhaust gas; (E) calculating in
real time the emission rate of the test gas from the relative
concentration of the test gas in the exhaust gas and the volumetric
flow rate of the exhaust gas; and (F) sending, in real time, the
calculated emission rate of the test gas to a display device;
wherein the steps are performed by a suitably-programmed digital
computer.
10. The method of claim 9, wherein the computer obtains the
measurement of ambient pressure; instantaneous compressibility
factor for the fuel gas; gross calorific value for the fuel gas;
and dry fuel F factor for the fuel gas, from a computer-readable
database.
11. The method of claim 10, wherein the computer receives the
measurements of relative concentration of the test gas in the
exhaust gas; relative concentration of O.sub.2 in the exhaust gas;
flowrate of the fuel gas; temperature of the fuel gas; and pressure
of the fuel gas, from a data collection buffer that collects the
relative concentrations of the test gas and O.sub.2 from a gas
analyzer; collects the flow rate of the fuel gas from a fuel gas
flowmeter; collects the fuel gas temperature from a temperature
sensor located proximate to the fuel gas flowmeter; collects the
fuel gas pressure from a pressure sensor located proximate to the
fuel gas flowmeter; formats this collected data into a form
suitable for the computer; and sends this formatted data to the
computer.
12. A method for determining the emission rate of a selected test
gas emitted in the exhaust gas of a gas-fueled engine having an
intake manifold, the method comprising the steps of: (A) measuring
the relative concentration of the test gas in the exhaust gas; (B)
measuring each of fuel-gas flowrate, fuel-gas temperature and
fuel-gas pressure; (C) measuring each of intake manifold
temperature and intake manifold pressure; (D) calculating a
volumetric flowrate of the exhaust gas using the measurements of
the fuel-gas flowrate, temperature and pressure; (E) calculating a
test gas emission rate using the calculated volumetric flowrate of
the exhaust gas and the measurement of the relative concentration
of the test gas; (F) determining engine load from a load curve
using the intake manifold temperature and intake manifold pressure
measurements; and (G) calculating an emission rate per engine load
using the calculated emission rate of the test gas and the engine
load; wherein steps D, E, F and G, are performed in real time by a
suitably-programmed digital computer.
13. The method of claim 12, further comprising the steps of: (A)
obtaining engine data from a computer-readable database; and (B)
selecting an appropriate engine load curve from a plurality of
engine load curves based on the engine data.
Description
RELATED APPLICATION
[0001] This application is a continuation of pending U.S. patent
application Ser. No. 10/057,379, filed 20 Nov. 2001, which claims
the benefit of U.S. Provisional Patent Application No. 60/249,436,
filed 20 Nov. 2000.
FIELD OF THE INVENTION
[0002] This invention relates to methods and portable apparatus for
testing engine exhaust, particularly the exhaust from large
industrial engines.
BACKGROUND OF THE INVENTION
[0003] Large, industrial engines are used for a variety of
purposes, including: to generate electrical power; to drive pumps;
and to drive compressors for the compression of natural gas in
pipelines. In use, these engines emit a variety of gases, including
carbon monoxide ("CO"), carbon dioxide ("CO.sub.2") and
nitrogen/oxygen compounds ("NO" and "NO.sub.2"). Concern about the
environmental effect of the exhaust from these engines has resulted
in widespread regulation of the operation of these engines, and
particularly regulation of exhaust emissions. In many countries,
these engines may not be operated without a permit granted by the
relevant regulatory body.
[0004] Typically, such permits set out maximum emission limits for
specified gases. The permit for a particular engine may merely set
out a maximum emission rate for each specified gas or it may
specify a maximum emission rate for each specified gas at a
specified engine load. To ensure that the engine complies with the
permitted emission rate, such permits also typically require that
the engine emissions be monitored using a specified testing
protocol. The permit may require that the emissions be monitored
continuously, but, more commonly, such permits require that the
engine be tested periodically, such as every year.
[0005] The test protocols for periodic engine emission testing
typically require that a series of tests of set duration be
conducted. As well, the test protocols typically specify pre-test
and post-test calibration procedures for the gas sensors used to
measure the concentration of the test gases. Typically, when an
industrial engine is tested for compliance with the permitted
emission rate, neither the emission rates of the test gases nor the
engine load can be easily measured directly. Rather, the test
protocols provide for a variety of different measurements to be
taken so as to enable the testers to estimate the emission rates of
the test gases and the engine load.
[0006] It is difficult to measure the weight per unit time of a
given regulated effluent gas (test gas) directly, so it is
conventional to measure the concentration of the test gas in the
exhaust and the volume of the exhaust gas and from those
measurements compute the rate of emission of the test gas in pounds
per hour (lbs/hr) or other designated units of measurement. In
simple terms, the emission rate of a test gas is determined by:
measuring the concentration of the test gas, typically in parts per
million; determining or at least estimating the exhaust gas
volumetric flow (that is, the rate of exhaust gas emission as
indicated by a unit of volume over a unit of time); and using these
two numbers to estimate the emission rate of the test gas.
[0007] It is, however, further difficult to accurately directly
measure the volumetric flow of the hot, turbulent exhaust gas.
Therefore, conventionally, the exhaust gas volumetric flow is also
estimated. For an engine powered by natural gas, the exhaust gas
volumetric flow can be estimated from: the volumetric flow of the
fuel gas; a fuel factor constant; and the concentration of oxygen
(O.sub.2) in the exhaust gas. The volumetric flow of the fuel gas
can be measured directly with a flowmeter, but it must be corrected
for temperature and pressure to be of use in estimating the exhaust
gas volumetric flow. The fuel factor constant is determined from
the concentrations of the constituent compounds of the fuel gas. In
simple terms, the exhaust gas volumetric flow is estimated by
determining the corrected volume of fuel gas and calculating, on
the basis of the fuel gas composition, what the volume will be
after combustion, with a correction for the concentration of
O.sub.2 in the exhaust gas.
[0008] As well, using previously known procedures and conventional
portable apparatus for engine emission testing, the engine load is
usually estimated from the work done by whatever equipment the
engine is driving. For example, if the engine is driving a
compressor, the work done by the compressor may be determined by
measuring the pressure and volumetric flow of gas upstream of the
compressor, and the pressure of the gas downstream of the
compressor. Such measurements can be used to determine the work
done by the compressor, but, due to power losses in the compressor,
and in the linkage between the engine and the compressor, they may
not be an accurate indicator of the engine load. Depending on these
power losses, the actual engine load may be up to 12% greater than
the engine load estimated by this method, resulting in errors in
the emission test results. While some tolerance for such errors can
be taken into account when the regulatory authority sets emission
standards, it would be preferable to obtain more accurate
measurements of engine load.
[0009] The concentrations of the test gases can be measured
directly with any of a variety of commercially available gas
analyzers, including electrochemical, non-dispersive infrared and
chemiluminescence gas analyzers. Typically, these gas analyzers
contain sensors (also referred to in the trade as "cells") for
measuring the concentration (in parts per million) of the gases
specified in the engine permit (usually CO, CO.sub.2, NO and
NO.sub.2.) As well, the gas analyzers typically also measure the
concentration of O.sub.2. In the known procedures for analyzing
engine emissions, the O.sub.2 measurements are used as indicators
of whether the engine is running in a rich or lean combustion
state.
[0010] The sensors may be cross-sensitive in that their accuracy
may be affected by the presence of non-target gases (referred to as
"interfering gases"). Cross-sensitivity is also referred to as the
interference response. A sensor's cross-sensitivity to a particular
interference gas is tested by exposing the sensor and a sensor
targeted to the interference gas, to a test gas containing the
interference gas but not containing the target gas of the sensor
being tested for cross-sensitivity. For example, a NO.sub.2
sensor's cross-sensitivity to NO would be tested for by exposing
the NO.sub.2 sensor and a NO sensor to a test gas containing NO but
not containing NO.sub.2. Any response by the NO.sub.2 sensor to the
test gas would be due to cross-sensitivity. Cross-sensitivity may
be quantified by comparing the interference response of the sensor
being tested (the NO.sub.2 sensor in the example) with the response
of the interference-gas-targeted sensor (the NO sensor in the
example).
[0011] The measurements from the gas sensors may not be stable, in
that they may have a tendency to drift over time when the sensor is
exposed to a gas with a constant concentration of the relevant test
gas. This quality of the sensors is referred to as stability or
sensor drift, the two terms implying opposite characteristics.
Sensor drift may be evaluated by exposing the sensor to a
calibration gas and noting how the sensor measurements vary over
time. The extent of sensor drift is often stated as the maximum
absolute percentage deviation from an average measurement recorded
shortly after the measured response time of the sensor.
[0012] Further, the accuracy of the measurements from a sensor may
not be consistent over a range of concentrations, particularly when
the sensor is subject to rapidly changing concentrations of the
test gas. This quality of a sensor is referred to as degree of
linearity of the sensor, or simply "linearity". Linearity is tested
by first exposing a sensor to at least two gases having different
concentration of the test gas, one after the other, and observing
the response of the sensor over time to the different
concentrations of the test gas.
[0013] The test protocols typically require that the sensors be
calibrated within a specified period before and after the relevant
test. The test protocols typically require that the sensors be
tested for calibration error and cross-sensitivity before and after
each test run. The calibration error test results may be used to
correct the sensor's measurements, or if they fall outside of the
required parameters, they may be cause to reject the results from
the test run as unreliable, and possibly to indicate the need to
replace the sensor.
[0014] The testing procedure typically involves transporting a gas
analyzer to the engine location; connecting it to the exhaust
stream; running the required tests and recording the test data;
disconnecting the gas analyzer; removing it from the test location;
and processing the data to generate the test results at some later
date.
[0015] The conventional delay in processing the test data means
that it is not known whether the engine has met the required
emission standards until the testing is complete and the data can
be processed, which typically does not occur until after the
testing equipment has been removed from the engine site. If it
turns out from the later data processing that an engine has failed
a test, it is typically necessary to re-transport the testing
apparatus to the test site and reinstall the testing equipment in
order to rerun the test. In some cases, tuning the engine might
make the difference between meeting the permit requirements and
failing the test. However, various previously known testing
procedures do not provide feedback of data on the engine emissions
in real time, and therefore offer no guidance with respect to
tuning the engine.
[0016] For an engine powered by natural gas, the data required to
determine the emission rates of the test gases at a certain engine
load include: the concentration of the test gases in the engine
exhaust; the concentration of O.sub.2 in the exhaust; the fuel gas
volumetric flow; the fuel gas temperature; the fuel gas pressure;
and the engine load. The concentrations of the specified test gases
are recorded electronically. However, with the known procedures for
performing emission testing, the fuel gas volumetric flow, the fuel
gas pressure; the fuel gas temperature, and the engine load are
merely written down by the person conducting the test. Typically,
this handwritten information is later manually entered into a
computer database or spreadsheet for processing with other
information recorded during the test. It is clear that errors can
occur both at the initial note-taking and later when the
information is subsequently entered into the computer.
[0017] What is needed is a portable engine emission analyzer that:
produces engine emission information in real time; permits the
generation of a test report immediately after an emission test is
conducted; reduces the risk of operator error; and is used in
combination with a more accurate source of engine load
information.
BRIEF SUMMARY OF THE INVENTION
[0018] In ordinary engineering parlance, and in this specification,
"in real time" means data and actions on data occur or are
available in real time, or are so time-correlated to the sequence
of physical events to which the data relate so as to provide the
same benefit, for all practical purposes, as if they had occurred
or were available simultaneously with the physical events to which
they relate.
[0019] The method of emissions testing and determination of the
present invention differs from most conventional prior methods in
that it comprises a method of testing a engine and analyzing the
exhaust emissions of the engine and making the necessary
computations to determine the emission rate of a specified test gas
or test gases in real time. Most conventional prior methods are
incapable of providing real-time results but instead require a
delay between the measurement stage of the method and at least part
of the computation stage of the method.
[0020] The preferred method of analyzing the exhaust emissions of
gas-fuelled engines in real time according to the invention is
capable of providing a relatively accurate determination of the
emission rate for the test gas (to the extent that the sensors used
are reliable and that the test equipment is accurately
calibrated).
[0021] In one aspect of the invention, suitable for use for
determining the amount of a specified test gas in the exhaust of an
engine powered by natural gas fuel or other gaseous fuel, the
method includes the steps of:
[0022] (a) measuring the flowrate, temperature and pressure of the
fuel gas;
[0023] (b) measuring the relative concentration of the test gas in
the engine exhaust;
[0024] (c) computing a volumetric flowrate of the exhaust gas from
the measurement data representing the flowrate, temperature and
pressure of the fuel gas;
[0025] (d) computing an emission rate (conventionally expressed in
the units lbs/hr) of the test gas from the exhaust gas volumetric
flowrate data and the data representing the relative concentration
of the test gas;
[0026] (e) determining or measuring the engine load at which steps
(a) and (b) occur, and computing an emission rate per engine load
(conventionally expressed in the units lbs/BHP-hr) from the
computed emission rate and engine load;
[0027] (f) optionally, recording or displaying the calculated test
gas emission rate; and
[0028] (g) optionally performing further calculations and
tabulations of the gas emission rate data, e.g. comparing the
calculated test gas emission rate to the maximum permitted emission
rate and, if the calculated emission rate is greater than the
permitted emission rate, displaying a warning or alarm or record or
display of this result.
[0029] In the foregoing summary, and in this specification
generally, the step of "measuring" may be a composite step
involving measurement of one or more given parameters and then
performing a calculation on it to derive an estimated value for the
parameter whose value is sought. In other words, measured values
include estimated values where direct measurement of a parameter is
difficult. Further, in the above summary, and in this specification
generally, the step of "computing" or "calculating" includes
providing as an interim or final output the results of the
computation in digital data format. Further, the step of
"measuring" is to be taken as including, as necessary, the
conversion of any analog measurement data to digital format. All of
the foregoing computation steps may be performed in real time by a
programmed computer and may be repeated a pre-selected number of
times at pre-selected time intervals.
[0030] As discussed above, the method normally includes the step of
determining the engine load (typically expressed in BHP) so that an
emission rate per engine load (typically lbs/BHP-hr) may be
calculated and recorded or displayed as required. However, in some
cases this step may not be necessary. For example, if the maximum
emission levels in a permit are not in terms of emission rate per
engine load, there may be no need to determine the engine load or
compute the emission rate per engine load.
[0031] Preferably, the step of determining the engine load
comprises correlating in real time engine data, including intake
manifold temperature and pressure, and the engine RPM (usually
manually entered as an input into the programmed computer) with a
load curve for the engine. A load curve appropriate to a particular
engine is typically prepared by, and obtained from, the
manufacturer of the engine. A load curve is typically specific to a
particular model, but a load curve may instead be specific to a
particular conformation (e.g. turbo-charged or naturally aspirated)
of a particular model, or to a particular conformation of a
particular model under particular operating conditions (e.g.
intercooler water temperature or manifold temperature). Correlating
the engine data to the load curve involves: selecting the
appropriate load curve, which entails comparing some of the known
engine data with the load curve selection criteria; and then using
the load curve data and additional engine data to calculate the
engine load. Preferably, discrete values not found on the engine
manufacturer's load curve are calculated using Newton's Method of
Interpolation. Preferably the data from each load curve is
incorporated into a computer routine (sometimes referred to in the
trade as a "function") along with Newton's Method of Interpolation,
such that the programmed computer may "call the function", that is,
provide a particular routine with values for the required variables
and instruct the routine to calculate the engine load.
[0032] Alternatively, the engine load may be approximated by
correlating the engine RPM with the engine manufacturer's
RPM-engine load specifications (preferably stored in the
computer-readable database).
[0033] In another aspect of the invention, an engine emission
analyzer comprises a programmed computer connected to: a data
collection buffer, a computer-readable database and a display
device. The data collection buffer is configured to connect to, and
receive data from: a gas analyzer for sensing the relative
concentration of the specified test gas or gases and O.sub.2; an
intake manifold temperature sensor; an intake manifold pressure
sensor; a fuel gas flowmeter; a fuel gas pressure sensor; and a
fuel gas temperature sensor. The data buffer is configured to:
accept the sensed data (some in analog and some in digital form),
digitize the analog data, organize the data into batches that can
be recognized by the programmed computer, and send the batches to
the programmed computer. The computer-readable database is for
storing data used in performing the engine emission analysis,
including: the specifications of the engine being tested; the
maximum emission limits for each of the test gases (pollutants)
specified in the relevant permit; the testing parameters; and
various calculation factors. The display device is preferably a
display screen, but may be a printer or any other suitable means
for indicating, recording or storing test results for the benefit
of the user. The programmed computer is programmed to receive
batches of data from the data buffer; to call up and receive data
from the database as required; to perform the engine emission
analysis calculations; and to send data representing computed
emission rates and other relevant data to the display device.
[0034] Preferably, the data collection buffer is configured to
connect to, and receive data from, a second gas analyzer and two
exhaust temperature sensors, so that the apparatus may also be used
to test the effectiveness of in-line catalyst elements (catalytic
converter) for treating exhaust. In such use, the data collection
buffer is connected to an upstream gas analyzer that draws exhaust
gas from upstream of the catalytic converter, an upstream
temperature sensor that senses the exhaust temperature upstream of
the catalytic converter; a downstream gas analyzer that draws in
exhaust gas from downstream of the catalytic converter; and a
downstream temperature sensor that senses the exhaust temperature
downstream of the catalytic converter. The data collection buffer
digitizes this data, organizes it into batches that can be
recognized by the programmed computer, and sends the batches to the
programmed computer. The programmed computer calculates the
differences between the upstream and downstream levels of the
relevant test gas or gases; calculates the difference between the
upstream temperature and the temperature necessary to stimulate the
desired chemical reaction between the catalyst and the exhaust gas;
calculates the difference between the upstream and downstream
temperature of the exhaust gas (an indicator of the extent to which
the desired catalyzed reaction, which is exothermic, is occurring);
and sends the calculated results to the display device in real
time.
[0035] Preferably, the programmed computer is programmed to
calculate, in real time, and send to the display device,
brake-specific fuel consumption (BSFC) for use as a guide to engine
tuning. The BSFC, typically expressed as rate of fuel consumption
per engine load, is an indication of engine efficiency, with a
lower BSFC indicating greater efficiency than a higher BSFC. In use
for tuning an engine, the programmed computer calculates BSFC from
the measurements of intake manifold pressure and temperature, and
fuel-gas flow, pressure and temperature, and sends the digitized
result to the display device or other suitable recording
device.
[0036] The various features of novelty that characterize the
invention are pointed out with more particularity in the appended
claims. For a better understanding of the invention, its operating
advantages and specific objects attained by its use, reference
should be made to the accompanying drawings and descriptive matter
in which there are illustrated and described preferred embodiments
of the invention.
SUMMARY OF THE DRAWINGS
[0037] FIG. 1 is a schematic block diagram of the engine emission
analyzer connected to an engine, in accordance with the principles
of the present invention.
[0038] FIG. 2 is a schematic block diagram of the data collection
buffer of FIG. 1.
[0039] FIG. 3 is a flow chart of steps performed by the data
collection buffer of FIG. 2 in receiving, organizing and sending
data.
[0040] FIG. 4 is a schematic block diagram of the engine emission
analyzer of FIG. 1 configured for evaluating the effectiveness of a
catalytic converter.
[0041] FIG. 5 is a schematic block diagram of the engine emission
analyzer of FIG. 1 configured for determining the brake specific
fuel consumption of the engine being tested, for the purpose of
optimizing engine performance.
[0042] FIG. 6 is a flowchart showing initial steps of a preferred
implementation of a method according to the invention, preferably
using WinStack.TM. software that is suitable for use in performing
computations according to the method of the invention.
[0043] FIG. 7 is a flowchart showing steps of the Emission
Source/Compliance test mode of use of the WinStack.TM. software, in
accordance with a preferred implementation of a method according to
the invention.
[0044] FIG. 8 is a flowchart showing fuel measurement and fuel
factor calculation steps of the Source test mode of use of the
WinStack.TM. software, in accordance with a preferred
implementation of a method according to the invention.
[0045] FIG. 9 is a flowchart showing fuel measurement and fuel
factor calculation steps of the Compliance test mode of the use of
the WinStack.TM. software, in accordance with a preferred
implementation of a method according to the invention.
[0046] FIG. 10 is a flowchart showing engine load approximation
steps of the use of the WinStack.TM. software, in accordance with a
preferred implementation of a method according to the
invention.
[0047] FIG. 11 is a flowchart showing calibration error test steps
of the use of the WinStack.TM. software, in accordance with a
preferred implementation of a method according to the
invention.
[0048] FIG. 12 is a flowchart showing Catalyst Efficiency mode
steps of the use of the WinStack.TM. software, in accordance with a
preferred implementation of a method according to the
invention.
[0049] FIG. 13 is a flowchart showing Engine Optimization mode
steps of the use of the WinStack.TM. software, in accordance with a
preferred implementation of a method according to the
invention.
[0050] FIG. 14 is a generalized flowchart showing the steps of an
emission test (as opposed to the preliminary inputting of data and
calibration of sensors) performed with the use of a preferred
method according to the invention.
DESCRIPTION OF A SPECIFIC EMBODIMENT
[0051] FIG. 1 shows a conventional industrial, gas-fuelled engine
(20) and a preferred embodiment of the engine emission analyzer
(22) according to the invention. The engine includes: a fuel gas
inlet (24) for coupling to a fuel gas line (30); intake manifold
(26); and exhaust stack (28). The fuel gas line (30) provides fuel
gas to the engine (20). The working parts of the engine (20) are of
no interest for the purposes of the description of the invention
and are omitted from the drawing in the interest of simplicity.
[0052] The engine emission analyzer (22), includes a data
collection buffer (52); a programmed computer (54) incorporating a
display device (typically a video monitor) (not shown) and a
computer readable database (not shown). The engine emission
analyzer (22) is connected to a printer (56); a gas analyzer (40);
a fuel gas flowmeter (42); a fuel gas pressure sensor (44); a fuel
gas temperature sensor (46); an intake manifold pressure sensor
(48); and an intake manifold temperature sensor (50). The meter and
sensors are selected for suitability in measuring selected
parameters associated with an industrial gas-fuelled engine. The
data collection buffer (52) is connected by suitable communication
links (58) to the gas analyzer (40); the fuel gas flowmeter (42);
the fuel gas pressure sensor (44); the fuel gas pressure sensor
(44); the intake manifold pressure sensor (48); the intake manifold
temperature sensor (50); and the programmed computer (54). The
programmed computer (54) is connected by suitable communication
link (58) to the printer (56).
[0053] In a preferred embodiment, the gas analyzer (40) is an
electrochemical five-gas analyzer, such as the ECOM SG PLUST.TM.,
manufactured by ECOM America. It will be clear to those skilled in
the art of exhaust gas analysis that alternative gas analyzers,
such as non-dispersive infrared gas analyzers and chemiluminescence
gas analyzers, may also or instead be used. The gas analyzer (40)
contains sensors (not shown), also referred to as cells, for
measuring the concentrations of CO, NO, NO.sub.2 and O.sub.2. These
sensors are typically capable of measuring concentrations of the
relevant test gases as small as a few parts per million. The
measurements from NO cells are affected by changes in temperature,
so the gas analyzer (40) also includes a NO cell temperature sensor
(e.g., a thermocouple) (not shown).
[0054] In the embodiment shown in FIG. 1, the gas analyzer (40) is
a typical extractive type, in that it draws gas from the exhaust
stack (28) via an internal vacuum pump (not shown). Also typically,
the exhaust gas flows from the exhaust stack (28) through a heated
sample line (70) (to prevent condensation) to a sample conditioner
(72). The sample conditioner (72) dries the exhaust gas with a
desiccant and then heats it to avoid condensation. The heated
exhaust gas then enters the gas analyzer (40) where it is
immediately cooled below the dew point by an internal cooler (not
shown). This process is the usual method of extracting exhaust gas
when using an extractive-type gas analyzer and is intended to
ensure that the exhaust gas analyzed by the gas analyzer (40) is
dry.
[0055] The fuel gas flowmeter (42) is any suitable selected
commercially available turbine-type meter, such as the 7400 Series
(TM) turbine meter manufactured by Barton Instruments Systems Ltd.
The fuel gas flowmeter (42) is positioned within a rigid pipe,
referred to as a meter run (74). Typically, the manufacturer's
specifications require that the turbine meter be installed at least
10 pipe diameters downstream and 5 pipe diameters upstream of any
flow disturbances such as elbows or sudden expansions. In use, a
turbine-type flowmeter emits a voltage-pulse output, with the pulse
rate proportional to the velocity of the fuel flow. A numeric value
provided by the flowmeter manufacturer, referred to as the
"K-factor", is used as a conversion factor to convert the frequency
of the pulsed output to a volumetric flow rate.
[0056] The fuel gas pressure sensor (44) is any suitable selected
commercially available pressure transducer, such as the PT-400
model (TM), manufactured by SRP Controls. The fuel gas pressure
sensor (44) is usually positioned in the meter run (74) proximate
to the fuel gas flowmeter (42). Typically, the fuel gas pressure
sensor (44) emits a fluctuating current output (typically in the
range 4-20 mA) with the current being proportional to the fuel gas
pressure.
[0057] The fuel gas temperature sensor (46) is any suitable
selected commercially available thermocouple, such as the type
"J".TM. thermocouple manufactured by Alltemp Sensors. The fuel gas
temperature sensor (46) is usually positioned in the meter run (74)
proximate to the fuel flowmeter. Typically, the fuel gas
temperature sensor (46) emits a fluctuating voltage output with the
voltage being proportional to the fuel gas temperature.
[0058] As shown in FIG. 1, the meter run (74) is connected to the
fuel gas line
[0059] so that the fuel gas can be diverted to pass through the
meter run (74). The meter run (74) is typically connected to the
fuel gas line with flexible high-pressure, Teflon.TM.-lined hose.
When the fuel gas bypass valves (76) are open and the fuel gas
block valve (78) is closed, the fuel gas flows through the meter
run (74) en route to the fuel gas inlet (24). Once the fuel gas
bypass valves (76), fuel gas block valve (78) and associated
T-junctions (tees) are installed in the fuel gas line (30), the
meter run (74) may be installed and removed without stopping the
engine (20). The meter run (74) is generally installed downstream
of conventional fuel gas scrubbers (not shown) so that the fuel gas
is dry when the temperature, pressure and flow measurements are
made.
[0060] The intake manifold pressure sensor (48) is any suitable
selected commercially available pressure transducer, such as the
PT-400 model.TM., manufactured by SRP Controls. The intake manifold
pressure sensor (48) is installed where it can sense the pressure
within the intake manifold (26). Typically, the intake manifold
pressure sensor (48) emits a fluctuating current output (4-20 mA)
with the current being proportional to the intake manifold
pressure.
[0061] The intake manifold temperature sensor (50) is preferably
any suitable selected commercially available thermocouple, such as
the type "J".TM. thermocouple manufactured by Alltemp Sensors. The
intake manifold temperature sensor (50) is installed where it can
sense the temperature of the gases within the intake manifold (26).
Typically, the intake manifold temperature sensor (50) emits a
fluctuating voltage output with the voltage being proportional to
the intake manifold temperature.
[0062] As shown in FIG. 2, the data collection buffer (52)
includes: a microprocessor (90) with internal Flash EPROM (not
shown) and Static RAM (not shown); a UART (91); two thermocouple
amplifiers (92); two current-to-voltage precision resistor circuits
(94); a pulse signal amplifier (96); a pulse counter (97); an
analog to digital converter (98); a gas analyzer serial port (100);
a programmed computer serial port (102); two temperature sensor
communication ports (104); and two pressure sensor communication
ports (106).
[0063] An example of a suitable microprocessor is model number
MC68HC16Z1 manufactured by Motorola. For ease of understanding, the
pulse counter (97) and analog to digital converter (98) are shown
as components separate from the microprocessor in FIG. 2. However,
one pulse counter input and eight analog-to-digital converter
inputs are integral parts of the Motorola MC68HC16Z1
microprocessor.
[0064] The Flash EPROM is an electrically programmable read-only
memory device wherein a program can be read into the memory and
then made permanent by sending a higher than normal voltage (the
"flash" voltage) to the device. Such Flash EPROMs are well known in
the art and are readily commercially available. An example of a
suitable Flash EPROM is model number AT49F001 manufactured by
Atmel. It will be clear to those skilled in the computer art that
other memory storage devices could be used.
[0065] The Static RAM is a form of random access memory device.
Such Static RAMs are well known in the art and are commercially
available. An example of a suitable static Ram is model number
AS7C1026 manufactured by Alliance Semiconductors. It will be clear
to those skilled in the art that other random access memory devices
could be used instead.
[0066] The UART (91) is a universal, asynchronous
receiver/transmitter which controls communication between the
microprocessor (90) and the serial ports. Such devices are well
known in the art and are commercially available. An example of a
suitable UART is model number TL16C5541FN manufactured by Texas
Instruments.
[0067] The thermocouple amplifiers (92) amplify the signals from
the intake manifold temperature sensor (50) and the fuel gas
temperature sensor (46). In a preferred embodiment, the
thermocouple amplifiers (92) amplify the signal from the
temperature sensors so that each 10 mV of the amplified signal
corresponds to 1 degree Celsius. Such thermocouple amplifiers (92)
are well known in the art and are commercially available. An
example of a suitable thermocouple amplifier is the "Monolithic
Thermocouple Amplifier with Cold Junction Compensation", model
number AD594 version `C.`, manufactured by Analog Devices Inc.
[0068] The current-to-voltage precision resistor circuits (94)
convert the electric current fluctuations in the signals received
from the intake manifold pressure sensor (48), and the fuel gas
pressure sensor (44), into voltage fluctuations. In a preferred
embodiment, the voltage precision resistor circuits (94) convert a
4 to 20 mA amperage fluctuation into a 0.4 to 2 V voltage
fluctuation. Such current-to-voltage precision resistor circuits
(94) are well known in the electrical art and are readily
commercially available.
[0069] The pulse signal amplifier (96) conditions the voltage pulse
signals from the fuel gas flowmeter (42). Typically each voltage
pulse generated by a turbine-type flowmeter is a sine wave. The
pulse signal amplifier (96) converts the sine waves of the voltage
pulses into square waves, which conversion facilitates counting the
pulses. The pulse signal amplifier (96) conditions the voltage
pulse signals by over amplifying the sine waves and squaring off
the resulting peaks and valleys. Such pulse signal amplifiers (96)
are well known in the art and are readily commercially available.
The signal from some flow meters is preamplified by the flowmeter
device, in which case the pulse signal amplifier (96) may not be
necessary.
[0070] The pulse counter (97) counts the voltage pulses it receives
and produces digital data representing the pulse count. The pulse
count data is sent to the microprocessor (90). Such pulse counters
(97) are well known in the art and are readily commercially
available.
[0071] The analog-to-digital converter (98) receives: the amplified
signals from the intake manifold temperature sensor (50) and the
fuel gas temperature sensor (46); the converted signals from the
intake manifold pressure sensor (48) and the fuel gas pressure
sensor (44); and the conditioned signal from the fuel gas flowmeter
(42), all of which code data by way of absolute voltage or voltage
differentials. The analog-to-digital converter (98) converts these
analog voltages into digital data interpretable by the
microprocessor (90) and the programmed computer (54).
[0072] In a preferred embodiment, the gas analyzer (40) produces
digital signals interpretable by the microprocessor (90) and the
programmed computer (54). The gas analyzer (40) sends the data
collection buffer (52) data strings, containing data from the
sensors, one after another. Each data string has an identifier
which indicates the beginning of the data string or the end of the
data string. For example, the Ecom SG PLUS.TM. gas analyzer uses
two characters comprised of bit sequences, hexadecimal `00` and
hexadecimal `F0`, to identify the beginning of the data strings
which it produces. Each data string is of a set length. The data
strings are comprised of several fields, each of set size and set
order within the data string. Each field has an identifier which
distinguishes it from the other fields in a particular data string,
but which is the same for that particular field in the other data
strings. The data from each particular sensor in the gas analyzer
are contained in the same particular field in every data string.
For example the data from the NO sensor might be contained in the
fourth field in the data strings. The fourth field could be
identified by counting bits from the identifier which indicates the
beginning of the data string and by recognizing the fourth fields
distinguishing identifier. This identification could be confirmed
by counting the bits or characters comprising the data identified
as the fourth field.
[0073] When power is applied to the data collection buffer (52),
the microprocessor (90) starts and runs a program stored in the
Flash EPROM (108). As shown in FIG. 3, the program instructs the
microprocessor (90) to receive data from the gas analyzer serial
port (110). Each bit sequence received is compared with the bit
sequence known to indicate the beginning or end of a data string.
This process continues until two sequential input bit sequences
match the special bit sequences which signify the start or end of a
data string. This sequence of bit sequences, confirmed by counting
the bits in the assumed data string, and checking the field
identifiers in the data, are used by the microprocessor (90) to
verify that a valid data string has been received. The bit
sequences identifying the beginning or end of the data string are
used as a reference point, and the required data are extracted from
the data string using the known field length and order. In a
preferred embodiment using the Ecom SG PLUS TM gas analyzer, the
microprocessor (90) compares a received character to "00"
hexadecimal (112). If the received character is "00" hexadecimal,
the microprocessor (90) compares the next character to "F0"
hexadecimal (114). If the next character is "FO" hexadecimal then
the microprocessor (90) counts the characters (115) in the data
string and reviews the string for the proper field identifiers
(116).
[0074] Once the relevant gas analyzer data have been extracted from
the data string, the data are stored in the SRAM (118) and the
microprocessor (90) stops receiving data from the gas analyzer
serial port (100). The microprocessor (90) then retrieves data
representing the measurements from the fuel gas flowmeter (42);
fuel gas pressure sensor (44); fuel gas temperature sensor (46);
intake manifold pressure sensor (48); and the intake manifold
temperature sensor (50). The microprocessor (90) then stores these
data in SRAM. The microprocessor (90) then formats the gas analyzer
and other sensor data and sends the data to the programmed computer
(122). The microprocessor (90) then resumes receiving data from the
gas analyzer serial port (110) and the cycle is repeated
continually.
[0075] In use, the programmed computer (54) receives digitized data
from the data collection buffer (52), including data representing
the following: measurements of the concentrations of NO, NO.sub.2
CO, CO.sub.2 and O.sub.2; measurements of the NO cell temperature;
measurements of the intake manifold pressure; measurements of the
intake manifold temperature; measurements of the fuel gas
volumetric flow rate; measurements of the fuel gas temperature; and
measurements of the fuel gas pressure.
[0076] In one embodiment of the invention, the person conducting
the test measures the ambient air pressure and the ambient
temperature and enters these measurements into the programmed
computer (54). It will be clear to those skilled in the art that
suitable thermometers and barometers (not shown) can be connected
to the programmed computer (54) by suitable communication link so
as to transmit the ambient temperature and pressure data
continuously to the programmed computer (54).
[0077] The programmed computer (54) has associated with it a
computer-readable database (not shown). Typically, the database is
a component of the computing device incorporating the programmed
computer, but the database may also be a peripheral device
connected to the programmed computer; a remote database accessed
via a long-distance communication means such as the Internet; or a
combination of these, in that different parts of the data used by
the programmed computer in determining emission rates may be in
different databases. For simplicity, this description refers to one
database though it is understood that more than one database may be
used.
[0078] The following data are stored in the database so as to be
accessible to the programmed computer (54) during a test:
[0079] a) the specifications of the engine to be tested, including
typically: the model number, compression ratio, timing, carburetor
setting (e.g. lean), engine displacement, intercooler water
temperature (if appropriate), rated BHP, and rated BSFC;
[0080] b) the maximum emission limits for each of the pollutants
specified in the relevant permit, typically in gms/BHP hour,
tons/yr and lbs/hr;
[0081] c) the selected testing parameters, typically the time
interval between readings, the number of readings and the emission
rate units;
[0082] d) various calculation factors, including the ambient
pressure, ambient temperature, the K-factor for the fuel gas
flowmeter (42), the molar weight of the fuel gas, and the dry fuel
F factor, gross calorific value, critical temperature and critical
pressure of the fuel gas.
[0083] The engine specifications are typically obtained from the
engine manufacturer and the engine operator, and typically are
manually input by the person conducting the test. The emission
limits are typically manually input when the engine is first tested
and thereafter the related data are stored in a database record
associated with the relevant engine and permit. The testing
parameters are either selected by the user and manually input, or
are set by a testing protocol associated with the relevant permit,
in which case they may be stored in a database record associated
with the protocol or permit.
[0084] As set out above, the ambient pressure and ambient
temperature are typically manually input into the programmed
computer (54) which stores the ambient pressure and ambient
temperature in the database. The K-factor is either provided by the
manufacturer fuel gas flowmeter (42) based on the manufacturer's
initial calibration of the fuel gas flowmeter (42) or is manually
input by the person performing the test to reflect a subsequent
recalibration of the fuel gas flowmeter (42).
[0085] The molar weight, dry fuel F factor, gross calorific value,
critical temperature and critical pressure of the fuel gas are
calculated from an ultimate analysis of the fuel gas, typically
obtained from the engine operator. Typically, the calculations are
performed by the programmed computer (54) which then stores the
results in the database. The dry fuel F factor (F.sub.d) is
calculated (per EPA 60 CFR 40, Method 19, Eqn. 19-13) as
follows:
F.sub.d=10E6[(3.64*%H)+(1.53*%C)+(0.57 *%S)+(0.14
*%N)-(0.46*%O)]/GCV.sub.- W Eqn 4
[0086] Where: % H=Weight Percentage Of Hydrogen From Ultimate
Analysis.
[0087] % C=Weight Percentage Of Carbon From Ultimate Analysis.
[0088] % S=Weight Percentage Of Sulfur From Ultimate Analysis.
[0089] % N=Weight Percentage Of Nitrogen From Ultimate
Analysis.
[0090] % O=Weight Percentage Of Oxygen From Ultimate Analysis.
[0091] The gross calorific value (GCV.sub.W) of the fuel gas is
calculated (per GPSA Standard 2172-72) as follows: 1 GCVw = x n H n
1 - ( x n b n ) 2 . Eqn . 1
[0092] Where: X.sub.n=Mole fraction of each component
[0093] H.sub.n=Gas Heating Value of each component.
[0094] b.sub.n=Summation Factor of each component
[0095] The critical temperature T.sub.C and critical pressure
P.sub.C of the fuel gas are calculated as follows:
P.sub.C=.SIGMA.P.sub.Cn*x.sub.n T.sub.C=.SIGMA.T.sub.Cn*X.sub.n Eqn
2
[0096] Where: P.sub.cn=Critical Pressure of each component.
[0097] T.sub.cn=Critical Temperature of each component.
[0098] x.sub.n=Mole fraction of each component.
[0099] The programmed computer (54) typically also performs
pre-test and post-test calculations related to the pre-test and
post-test calibration of the sensors, to determine interference
response and correction for sensor drift for the sensors. These
calculations include:
[0100] 1. CO Interference Response calculated (per CTM030 Method,
Section 6.3.1) as follows:
I.sub.co=[(R.sub.co-no/C.sub.nog*C.sub.nos/C.sub.cos)+(R.sub.co-no2/C.sub.-
no2g*C.sub.no2s/C.sub.cos)]*100 Eqn 8
[0101] Where: I.sub.co=CO interference response (%).
[0102] R.sub.co-no=CO response to NO span gas (ppm CO).
[0103] C.sub.nog=concentration of NO span gas (ppm NO).
[0104] C.sub.nos=concentration of NO in stack gas (ppm NO).
[0105] C.sub.cos=concentration of CO in stack gas (ppm CO).
[0106] R.sub.co-no2=CO response to NO.sub.2 span gas (ppm CO).
[0107] C.sub.no2g=concentration of NO.sub.2 span gas (ppm NO2).
[0108] C.sub.no2s=concentration of NO.sub.2 in stack gas (ppm
NO2).
[0109] 2. NO Interference Response calculated (per CTMO30 Method,
Section 6.3.2) as follows:
I.sub.no=(R.sub.no-no2/C.sub.no2g)*(C.sub.no2s/C.sub.noxs)*100 Eqn
9
[0110] Where: I.sub.no.dbd.NO interference response (%).
[0111] R.sub.no-no2=NO response to NO.sub.2 span gas (ppm NO).
[0112] C.sub.no2g=concentration of NO.sub.2 span gas (ppm
NO.sub.2).
[0113] C.sub.no2s=concentration of NO.sub.2 in stack gas (ppm
NO.sub.2).
[0114] C.sub.noxs=concentration of NOx in stack gas (ppm NOx).
[0115] 3. Concentration Correction For Sensor Drift calculated (per
CTMO30 Method, Section 8.1) as follows:
C.sub.GAS=(C.sub.R-C.sub.O)*C.sub.MA/(C.sub.M-C.sub.O) Eqn 10
[0116] Where: C.sub.GAS=corrected flue gas concentration (ppm).
[0117] C.sub.R=flue gas concentration indicated by gas analyzer
(ppm).
[0118] C.sub.O=average of initial and final zero checks (ppm).
[0119] C.sub.M=average of initial and final span checks (ppm).
[0120] C.sub.MA=actual concentration of span gas (ppm).
[0121] As shown in FIG. 14, when the actual emission test (as
opposed to the preliminary inputting of data and calibration of the
sensors) commences, the programmed computer (54) performs the step
of INITIALIZE VARIABLES AND COUNTER, which involves initializing
(or clearing) the relevant variables and setting a counter
(referred to as RECORD) to 0 (350). The programmed computer (54)
then performs the step of RETRIEVE INFORMATION FROM DATABASE (352),
which entails retrieving the engine specifications, emission
limits, testing parameters (including the number of readings,
referred to as NUM_READ) and calculation factors from the
database).
[0122] The programmed computer (54) then starts the TIMER (354) and
instructs the TIMER (354) to commence execution of the steps
starting with INCREMENT RECORD (356). The TIMER will thereafter
periodically commence execution of the steps starting with
INCREMENT RECORD (356) at the predetermined time interval between
readings (a setting previously obtained from the database) until
the TIMER receives instructions to halt.
[0123] The step of INCREMENT RECORD (356) entails adding 1 to the
RECORD counter.
[0124] The programmed computer (54) then performs the step of
COLLECT RAW DATA (358), which entails collecting from the data
collection buffer (52): the gas analyzer data (typically the sensed
relative concentrations of O.sub.2, CO, NO, NO.sub.2 and CO.sub.2,
and the NO cell temperature); the intake manifold temperature and
pressure; the fuel gas temperature and pressure; and the frequency
of pulse counts from the fuel gas flowmeter (42).
[0125] The programmed computer then performs the step of CALCULATE
FUEL GAS COMPRESSIBILITY (360) which entails calculating the Fuel
Gas Compressibility Factor (per GPSA Method, Section 16, Using
Standing & Kantz Compressibility Curves). The sensed pressure
(P.sub.act) is divided by the critical pressure of the fuel gas
(P.sub.c) (previously calculated and obtained from the database) to
determine the reduced (corrected) pressure of fuel gas P.sub.r. The
sensed temperature of the fuel gas (T.sub.act) is divided by the
critical temperature of the fuel gas (T.sub.C)) (previously
calculated and obtained from the database) to determine the reduced
(corrected) temperature of fuel gas (T.sub.r). 2 P r = P act P C T
r = T act T C Eqn 3
[0126] Where: P.sub.r=Reduced Pressure of fuel gas.
[0127] T.sub.r=Reduced Temperature of fuel gas.
[0128] P.sub.C=Critical Pressure of fuel gas.
[0129] T.sub.C=Critical Temperature of fuel gas.
[0130] The reduced pressure and temperature are correlated with the
Standing & Kantz compressibility curves using an internal
software subroutine to produce the actual compressibility
factor.
[0131] Although not generally required by EPA methodologies, the
programmed computer calculates the compressibility factor of the
fuel gas each time it performs the calculations (pursuant to the
user's instructions regarding the number of emission analyses to be
performed in a particular test and the time interval between each
analysis), to provide a corrected volumetric flow rate.
[0132] The programmed computer (54) then performs the step of
CALCULATE FUEL FLOW (362), which entails calculating the dry
volumetric flow rate of the fuel gas corrected for standard
conditions and compressibility (DCSFM.sub.fuel) as follows: 3 DSCFM
fuel = 60 * f * [ ( 528 / ( 460 + T fuel ) ) * ( P amb + P fuel ) /
29.92 ] z * K Eqn 5
[0133] Where: f=Frequency Of Pulses Generated By Turbine Meter.
[0134] Tfuel=Sensed Temperature Of Fuel Gas.
[0135] Pamb=Ambient Pressure.
[0136] Pfuel=Sensed Pressure Of Fuel Gas.
[0137] z=Compressibility Factor Of Fuel Gas.
[0138] K=Pulse Conversion Factor Provided By Turbine Meter
Manufacturer
[0139] The programmed computer (54) then performs the step of
CALCULATE EXHAUST FLOW (364), which entails calculating the dry
effluent volumetric flow rate (per an extension of EPA 40 CFR 60
Method 19) as follows: 4 Q sd = F d * HIR * 20.9 20.9 - % O 2 Eqn
6
[0140] Where: Qsd=Dry Effluent Volumetric Flowrate.
[0141] Fd=Dry Fuel F Factor.
[0142] HIR=Heat Input Rate (Fuel Heat Content (GCV.sub.W)*Fuel
Usage Rate (DSCFMfuel))
[0143] O2=Oxygen Content Of Effluent Gas (Used For Excess Air
Correction).
[0144] The programmed computer (54) then (or possibly before any or
all of steps 360, 362 and 364, or, alternatively, concurrently with
any or all of steps 360, 362 and 364) performs the step of
CALCULATE ENGINE HORESPOWER (366), by one of three possible
alternative methods, previously selected by the person performing
the test, as follows:
[0145] 1. By correlating engine data, typically the values of
intake manifold pressure, intake manifold temperature, engine model
and engine RPM with the engine manufacturer's load curve. Discrete
values not found on the engine manufacturer's load curve are
calculated using Newton's Method of Interpolation. The data from
each load curve are incorporated into a computer routine (referred
to as a function) along with Newton's Method of Interpolation, such
that the programmed computer may "call the function", that is,
provide a particular routine with values for the required variables
and instruct the routine to calculate the engine load.
[0146] 2. By using the engine manufacturer's brake specific fuel
consumption (BSFC) (previously obtained from the database) as
follows:
BHP=HIR/BSFC Eqn 11
[0147] Where: HIR=Heat Input Rate (BTU/hr)(Fuel Heat Content
(GCV.sub.W)*Fuel Usage Rate (DSCFMfuel))
[0148] BSFC=Brake Specific Fuel Consumption Published By Engine
Manufacturer (BTU/BHP-hr).
[0149] 3. By correlating the engine RPM with the engine
manufacturer's specifications. If this method is selected, then,
since the RPM does not vary during the test, the engine load
determined by this method remains constant throughout the test and
need not be determined for each iteration of the test steps. The
engine load is merely retrieved from the database, held in the
programmed computer's (54) local memory and assigned as the result
of the CALCULATE ENGINE HORESPOWER (366) step.
[0150] The programmed computer (54) then performs the step of
CALCULATE EMISSION RATE (368) which entails calculating the
emission rate (per CARB 100 Method) of each of the relevant
pollutants, as follows:
ERP=1.56E-7*PPM*Q.sub.sd*MW Eqn 7
[0151] Where: ERP=Emission Rate Of Pollutant (lbs/hr).
[0152] PPM=Concentration Of Pollutant.
[0153] Qsd=Dry Effluent Volumetric Flowrate.
[0154] MW=Molar Weight Of Pollutant.
[0155] The CALCULATE EMISSION RATE (368) step yields units of
lbs/hr. The molar weight of each pollutant is a constant. The molar
weight of each pollutant may be stored in the database or,
preferably, may be incorporated in the program of the programmed
computer.
[0156] The programmed computer (54) then performs the step of CHECK
EMISSION RATE UNIT (370), which entails: checking if the preferred
emission rate unit (either previously obtained from the database or
entered by the user during the test) is lbs/hr; and, if the
preferred unit is not lbs/hr, converting the emission rate to the
preferred unit or dividing the emission rate by the engine load to
obtain gr/BHP-hr or gr/KW-hr, if such is preferred.
[0157] The programmed computer (54) then performs the step of
POPULATE TAB PAGES (372), which entails adding the raw and
calculated data to various tab pages viewable on a display screen
(not shown) associated with the programmed computer (54) to enable
the user to view the data in real time. Alternatively, or
concurrently, the programmed computer could send the data to a
printer so as to continuously print the data during the test.
[0158] The programmed computer (54) then performs the step of
COMPARE TO PERMIT LEVELS (374), which entails comparing the
calculated emission rate of each pollutant with the maximum
permitted emission rate (previously obtained from the database),
and, if the calculated emission rate for a pollutant is above the
maximum permitted emission rate, notifying the user of this,
preferably by an indication on the display screen or alternatively
by generating an audible alarm. Preferably the programmed computer
(54) also notifies the user, in a similar though distinguishable
manner, when a calculated emission rate is 90% or more of the
maximum permitted emission rate.
[0159] The programmed computer (54) then performs the step of
COMPARE RECORD TO NUM_READ (376), which entails comparing the
RECORD counter to the preferred number of readings (NUM_READ)
(previously obtained from the database). If RECORD is less than
NUM_READ then the TIMER is permitted to continue commencing
execution of the steps commencing with INCREMENT RECORD (356). If
RECORD is equal to NUM_READ then the TIMER is halted.
[0160] The programmed computer (54) then performs the step of SAVE
RAW DATA (378), which entails saving the raw data to the database
for subsequent preparation of a formal emission report.
[0161] As shown in FIG. 4, another embodiment of the engine
emission analyzer (22), comprising two gas analyzers and two
exhaust stack temperature sensors, is useful for testing the
effectiveness of catalytic converters (130) in reducing pollution.
Catalytic converters (130) are often installed in-line in the
exhaust stack (28). In use, exhaust gas enters the catalytic
convertor chamber (132) and passes through a catalyst element (134)
of either ceramic or metallic composition. An exothermic chemical
reaction occurs through the catalyst element (134) which reduces
the levels of NO, NO.sub.2 CO and CO.sub.2, and increases the
downstream exhaust temperature. The catalytic convertor (130) may
not function at peak reduction efficiency due to a number of
reasons, such as: an incorrect air/fuel ratio setting; masking of
the catalyst element (134) with sulphated ash from the engine
lubricating oil; an exhaust temperature that is too low; or partial
destruction of the catalyst element (134) due to an engine
backfire. It is often desirable to be able to test the efficiency
of the catalytic converter (130).
[0162] For the purpose of testing the efficiency of a catalytic
converter (130), it is useful to simultaneously measure the
concentrations of the test gases, and the temperature of the
exhaust gas, upstream and downstream of the catalytic converter
(130). A preferred embodiment utilizes two gas analyzers (40), an
upstream gas analyzer (136), which draws exhaust gas from upstream
of the catalytic converter (130) and a downstream gas analyzer
(138) which draws exhaust gas from downstream of the catalytic
converter (130). As well, it is useful to obtain temperature
measurements upstream and downstream of the catalytic converter
(130). A preferred embodiment utilizes two temperature sensors: an
upstream temperature sensor (140) which sense the exhaust
temperature upstream of the catalytic converter (130) and a
downstream temperature sensor (142) which senses the exhaust
temperature downstream of the catalytic converter (142).
[0163] In one embodiment, suitable for testing catalytic converters
(130), the data collection buffer (52) includes a second gas
analyzer serial port (100) as shown in FIG. 2. The data collection
buffer (52) uses the same procedure to recognize and extract data
from each of the upstream gas analyzer (136) and the downstream gas
analyzer (138), as it uses when only one gas analyzer (40) is
present. When the data collection buffer (52) is connected to two
gas analyzers for the purpose of testing a catalytic converter
(130), the microprocessor (90) repeatedly extracts data from the
gas analyzers one after the other (typically, first the upstream
gas analyzer (136) and then the downstream gas analyzer (138)) and
stores the data in the SRAM. Once the microprocessor (90) has
retrieved and stored the data from both gas analyzers, the
microprocessor (90) stops receiving data from the gas analyzer
serial ports (100). The microprocessor (90) then retrieves the data
representing measurements from the upstream temperature sensor
(140) and the downstream temperature sensor (142). The
microprocessor (90) then stores these data in SRAM. The
microprocessor (90) then formats the gas analyzer and other sensor
data and sends the data to the programmed computer (122). The
microprocessor (90) then resumes receiving data from one of the gas
analyzer serial ports (110) and the cycle is repeated.
[0164] One measure of an engine's efficiency is its brake specific
fuel consumption (BSFC) rating. The BSFC indicates an engines rate
of fuel consumption per unit of engine load. A lower BSFC indicates
that an engine is more fuel efficient than an engine with a higher
BSFC. The BSFC is typically calculated by dividing the fuel
consumption rate by an approximated engine load. A feature of a
preferred embodiment of the engine emission analyzer is that it
determines in real time the fuel usage rate and the engine load as
part of the engine emission analysis. In one embodiment the
invention calculates and displays the engine BSFC in real time,
which helps a user tune an engine (20) in an attempt to reduce the
BSFC.
[0165] During an emission test in which the engine load is being
approximated on the basis of intake manifold pressure and
temperature, the programmed computer (54) is receiving the data
necessary to approximate the BSFC, and can be programmed to
approximate the BSFC as part of the emission test. Alternatively,
as shown in FIG. 5, only those sensors making the measurements
necessary for calculating the BSFC need be connected to the engine,
being: an intake manifold pressure sensor (48); an intake manifold
temperature sensor (50); a fuel gas flowmeter (42); a fuel gas
temperature sensor (46); and a fuel gas pressure sensor (44).
[0166] In a preferred embodiment of the invention, the programmed
computer has a display screen and runs a program, WinStack.TM.,
created by the inventors, which incorporates the relevant testing
protocol and uses the emission limits from the relevant permit to
ensure that the test results comply with the permit requirements
and the test protocol. WinStack.TM. is a Windows.TM. based system
containing executable files and incorporating a 32 bit Sybase
database platform. WinStack.TM. will run on Windows.TM. 32 bit
platforms, such as Windows 95.TM. & Windows 98.TM., but
WinStack.TM. hasn't been certified on Windows .sub.2000.TM. or
Windows NT.TM.. WinStack.TM. requires a computer having at least a
Pentium.TM. 133 MHz processor and 32 Mb of RAM, and with an SVGA
type monitor. WinStack.TM. requires at least 50 Mb of hard disk
space in order to operate correctly.
[0167] As shown in FIG. 6, after WinStack.TM. is started and
entered (148), it performs system diagnostic checks (150).
[0168] Engine emission test protocols typically specify that each
gas sensor be calibrated using a gas, referred to as the span gas,
with a known concentration of the gas that the sensor is designed
to detect, that is, the target gas. The test protocols also
typically specify that the concentration of the target gas in the
span gas used in the calibration checks must be within a set range.
The bounds of this range are defined in terms of the concentration
of the target gas in the actual exhaust being tested. For example,
the upper range of the allowable span gas concentration is roughly
three times the concentration of the target gas in the exhaust
stream. Conventionally, the person conducting the test obtains the
concentrations of the target gases with un-calibrated sensors and
uses the un-calibrated sensed concentrations of the target gases as
guides to the selection of appropriate span gases. Typically, the
person testing the exhaust has several span gas bottles with
different concentrations of target gases to choose from.
[0169] The system diagnostic checks (150) performed by WinStack.TM.
include checking the measurements being received from the CO, NO,
NO.sub.2 and O.sub.2 sensors for the purpose of determining an
appropriate span gas for the calibration of the sensors.
WinStack.TM. calculates an approved span gas range for each
sensor.
[0170] WinStack.TM. then prompts the user to select a test mode
(152), either: Emission Source/Compliance (154); Catalyst
Efficiency (156) or Engine Optimization (158).
[0171] "Source" and "compliance" are terms used by regulators to
distinguish different test criteria. A source test generally has a
more rigorous test protocol than a compliance test. A permit for a
particular engine might specify that a compliance test be conducted
every six months and a source test every four years.
[0172] The Catalyst Efficiency test mode (156) is used to test the
effectiveness of catalytic converters. The Engine Optimization test
mode (158) is used to approximate the BSFC for the purpose of
tuning an engine.
[0173] As shown in FIG. 7, when the user selects the Emission
Source/Compliance test mode (154), the user is prompted to enter
the relevant permit information data, or select the permit
information data from the WinStack.TM. database if the permit
information data have been previously entered into the computer
(160). The permit information data stored by the WinStack.TM.
database include the state or province in or for which the permit
has been issued, the date upon which the most recent previous test
was performed, the permitted emission levels and units, and the
maximum permitted time between each source or compliance test.
WinStack.TM. compares this data with the measured emission levels
during the test and indicates any breach of the permit
requirements. WinStack.TM. also notifies the user of any upcoming
emission tests, based on the permit number, the state or province,
and the time since the last test.
[0174] WinStack.TM. then prompts the user to enter, into the
appropriate fields, the following data: the facility location, the
relevant environmental board; the gas analyzer serial number; the
facility operator; and an identifier for the person performing the
emission test (162). The user then indicates whether a Source or
Compliance test will be performed (164). The user then enters the
ambient conditions at the test site (166). The ambient conditions
are the ambient barometric pressure and ambient temperature which
are measured by any suitable means.
[0175] WinStack.TM. then prompts the user to select a method for
determining the fuel gas volumetric flow (168).
[0176] If the user selected a Source test in a previous step (169),
then WinStack.TM. will require real-time fuel gas volumetric flow,
fuel gas temperature and fuel gas pressure measurements. Therefore,
for a Source test, it is necessary to divert the fuel gas through a
fuel metering system. As shown in FIG. 8, WinStack.TM. prompts the
user to indicate the model of flowmeter being used to measure the
fuel gas volumetric flow and to either enter a K-factor or edit the
K-factor displayed by WinStack.TM. based on the most recent
calibration of the flowmeter (170). WinStack.TM. then prompts the
user to enter a recent fuel gas composition (172). WinStack.TM.
then permits the user to either: enter the gross calorific value
and the molecular weight of the fuel, typically from a fuel gas
composition sheet; or enter the various mole fractions of the
components of the fuel gas (obtained from an earlier analysis of
the fuel gas) (174) in which case WinStack.TM. will calculate gross
calorific value and the molecular weight of the fuel. WinStack.TM.
then calculates the mass percentages of Carbon, Oxygen, Sulfur,
Nitrogen, Hydrogen, the pseudo critical properties and the fuel F
Factor (176). All data calculated and recorded during this step is
saved to the WinStack.TM. database for later retrieval and report
generation.
[0177] As shown in FIG. 9, if a compliance test was selected in a
previous step (177), then WinStack.TM. prompts the user to enter a
static value for the fuel volumetric flow rate, generally based on
a measurement from a flowmeter or a similar estimation. The
volumetric flow rate must be corrected for temperature and
pressure. WinStack.TM. permits the user to enter either an actual
fuel flow rate (178) as directly measured by the relevant metering
device; or an already corrected fuel flow rate (180). If the user
elects to enter a corrected flow rate, the user simply types in the
corrected volumetric flow rate. If the user elects to enter an
actual flow rate, then the user must enter the fuel flow, pressure
and temperature (182). WinStack.TM. then converts the actual flow
to a corrected flow based on the entered temperature and pressure.
The user then selects (183) between entering a generic fuel F
factor (184) or having WinStack.TM. calculate the fuel F factor
based on the fuel gas composition. If the user enters a generic
fuel F factor (184), WinStack.TM. estimates a generic value for the
gross calorific value of the fuel (1000 Btu/cf). If the user elects
to calculate the fuel F factor based on the fuel gas composition,
then the user enters the fuel gas composition data (186). The user
may then select for the programmed computer to calculate the fuel
parameters or the user may enter the parameters from a gas
analysis, if they are available (188). WinStack.TM. then calculates
the parameters required by EPA method 19 (190).
[0178] As shown in FIG. 7, for both the Compliance and Source test
modes, the user is then prompted to set the total number of
measurements recorded during each test and the time interval
between each reading (200).
[0179] WinStack.TM. then prompts the user to select the relevant
engine model for the test (202). WinStack.TM. lists engine models
based on the manufacturer, aspiration (natural or turbo-charged)
and combustion (rich burn or lean burn).
[0180] Depending on the selected engine model, WinStack.TM. then
permits the user to select from three methods for approximating the
engine load (204). Load can be approximated based on the manifold
conditions (208), the manufacturer's rated brake specific fuel
consumption (BSFC, typically in BTU/BHP-hr) (214), or the
manufacturer's rated engine load for specified engine RPM
(226).
[0181] As shown in FIG. 10, if the user elects to approximate the
engine load from manifold conditions (208) in data acquisition
mode, WinStack.TM. waits for the chosen delay period and then
accepts engine manifold pressure and temperature readings (210).
Then WinStack.TM. correlates the measured intake manifold
temperature and pressure with the engine manufacturer's load curves
(which relate intake manifold pressure and temperature with engine
load) and corrects for ambient temperature and barometric pressure
(already entered by the user) per the manufacturer's guidelines
(211). WinStack.TM. uses Newton's Interpolation Method to
approximate the engine load at temperature and pressure
measurements that do not fall at the discrete points defined by the
load curve representations. The user may tune the engine (212).
WinStack.TM. repeatedly accepts intake manifold temperature and
pressure measurements and repeats the above calculations based on
the number of measurements selected by the user (213).
[0182] As shown in FIG. 10, if the user elects to approximate the
engine load with the manufacturer's brake specific fuel consumption
(BSFC) (214), in data acquisition mode, WinStack.TM. waits for the
chosen delay period and then accepts fuel flow, fuel temperature
and fuel pressure measurements (216). WinStack.TM. then calculates
the heat input rate from the corrected fuel volumetric flow rate
and the gross calorific value of the fuel (218). WinStack.TM. then
approximates the engine load (typically BHP) based on the heat
input rate (typically Btu/hr) and the manufacturer's published BSFC
values (typically Btu/BHP-hr) (220). The user may tune the engine
(222). WinStack.TM. repeatedly accepts fuel flow, fuel temperature
and fuel pressure measurements and repeats the above calculations
based on the number of measurements selected by the user (224).
[0183] As shown in FIG. 10, if the user elects to approximate the
engine load from the manufacturer's engine load for specified
engine RPM ratings (226), then the user enters the engine RPM. In
data acquisition mode, WinStack.TM. waits for the chosen delay
period and then selects and retrieves a rated load from the
manufacturer's engine load in the database, corresponding to the
entered RPM (230). WinStack.TM. repeats the above approximation
based on the number of measurements selected by the user (232).
[0184] As shown in FIG. 7, WinStack.TM. then checks for blank
entries or erroneous inputs, and displays the previously entered
testing parameters (240), so as to permit the user to adjust or
correct any values through a `Preferences` section of the menu.
Once the user confirms via the computer program interface that the
entries are satisfactory, WinStack.TM. goes into the data
acquisition mode.
[0185] WinStack.TM. then displays all the data channels coming from
the data collection buffer (242). The display is configured so as
to make a viewer aware of any unexpected inputs (ie: inputs that
are not within the expected channel ranges) (244), so as to permit
the user to remedy a faulty sensor, or correct a situation where a
sensor has not been installed or connected properly.
[0186] As shown in FIG. 7, when the user is satisfied that all
sensors are reading correctly, the user instructs WinStack.TM. to
commence the pre-test calibration error phase (246). WinStack.TM.
requires the user to follow standard United States Environmental
Protection Agency ("EPA") procedures to ensure that the gas
analyzer correctly reads the gas concentration levels for NO,
NO.sub.2, CO & O2. The sensors in the gas analyzer are also
calibrated after the emission test.
[0187] FIG. 11 shows the calibration error procedure used for both
the pre-test calibration error phase and the post-test calibration
error phase.
[0188] The individual gas sensors in the gas analyzer are each
tested by exposing them to a gas, referred to as a span gas or
calibration gas, containing a known concentration of the gas which
each is designed to detect. The testing of each gas sensor involves
two phases: the zero to span phase; and the span to zero phase. In
the zero to span phase, the gas sensor is exposed to ambient air
and then to the span gas. In the span to zero phase, the sensor is
exposed to the span gas and then to the ambient air.
[0189] The user first selects one of the gas sensors to test (250).
The user connects the appropriate span gas cylinder to the gas
analyzer and then performs a zero to span analysis (252). During
the zero to span analysis, WinStack.TM. compares the actual data
received from the gas analyzer, with the known span gas
concentration, typically stamped on the calibration gas cylinder.
The time it takes a gas sensor to respond to 95% of the step change
from zero to span or span to zero, is referred to as the response
time of the gas sensor. After the gas sensor has sensed 95% of the
step change from zero to span, WinStack.TM. will compare the gas
sensor measurements to the known concentration of the target gas in
the span gas to determine if the gas sensor measurement is within
the EPA tolerance (254). If the reading is not within the EPA
tolerance, WinStack.TM. will require the user to conduct another
zero to span test of the sensor (264).
[0190] Once the sensor has passed the zero to span test,
WinStack.TM. requires the user to perform a span to zero test on
the sensor (256). The user must disconnect the gas analyzer from
the span gas cylinder, allowing the analyzer to sample ambient air,
which is the zero reference. After the gas sensor has sensed 95% of
the step change from span to zero, WinStack.TM. will compare the
gas sensor measurements to the known concentration of the target
gas in the ambient air to determine if the gas sensor measurement
is within the EPA tolerance (258). If the reading is not within the
EPA tolerance, WinStack.TM. will require the user to re-test the
sensor (including the zero to span test). If the reading is within
the required EPA tolerance, WinStack.TM. saves all the raw data for
both the span to zero and zero to span tests to the database (260).
The user then conducts the same tests of the remaining sensors.
WinStack.TM. checks that all the sensors have been tested (262).
Once all the sensors have passed the pre-calibration error test,
the user proceeds to the testing phase.
[0191] When the testing phase is entered, WinStack.TM. prompts the
user to select either line or bar graph format for real-time
graphical display purposes. WinStack.TM. then prompts the user to
select between two modes: "Tune Engine" and "Start Test". The "Tune
Engine" option allows the user to view all real-time levels (engine
emission, engine load, engine exhaust and fuel consumption levels)
without saving any data to the database. The purpose of this mode
is to provide an opportunity to the user to tune or adjust the
engine to be compliant with the permit emission limits. The "Start
Test" option allows the user to view all levels, and records all
raw data to the database for eventual report generation. Prior to
initiating the "Start Test" mode, most users will generally have
already made an attempt to tune the engine to meet the compliance
requirements of the permit.
[0192] The only significant difference between the "Tune Engine"
and "Start Test" modes is that in the "Start Test" mode all raw
data is saved to the database, whereas in the "Tune Engine" mode no
data is saved to the database. The description that follows refers
to the "Start Test" mode, but it also applies to the "Tune Engine"
mode.
[0193] As shown in FIG. 7, in the "Start Test" mode, raw data is
obtained from the data collection at the time intervals previously
stipulated by the user (270). The raw data is forwarded to
WinStack.TM. from the data collection buffer in a specific format
and sequence. The data is transferred to the computer memory for
analysis and plotting (271). This raw data is converted to standard
engineering units by WinStack.TM..
[0194] Depending on the load approximation method previously
selected by the user [28], WinStack.TM. approximates the engine
load using: pressure and temperature measurements (engine manifold
method); corrected fuel flow measurements (engine BSFC method); or
the manufacturer's rated load. WinStack.TM. calculates the
real-time fuel gas compressibility with a subroutine that uses the
Standing and Kantz compressibility curve approximation method
utilizing calculated pseudo critical gas properties and the
measured fuel gas temperature and pressure. Persons skilled in the
art of petroleum engineering will be familiar with the Standing and
Kantz method.
[0195] WinStack.TM. calculates the exhaust flow rate based on the
type of testing that was previously selected by the user. If the
user selected a Source test, WinStack.TM. takes the actual fuel
flow and corrects it for pressure, temperature and compressibility
to arrive at a corrected fuel flow. This value, coupled with other
previously calculated values (ie: the Fuel F factor, the Gross
Calorific Value etc.) is then used to calculate the real-time
exhaust flowrate If the user selected a Compliance test,
WinStack.TM. uses the previously entered static value for the fuel
flow.
[0196] WinStack.TM. calculates the emission levels based on the
user selected engineering unit, the measured concentration levels,
and the exhaust flow calculation. WinStack.TM. calculates the
engine fuel consumption and the engine BSFC in real-time, based on
the fuel gas volumetric flow measurement and the engine load
approximation. WinStack.TM. presents the user with: real-time
emission levels, the engineering units of which may be changed at
any time through a menu selection; a corrected fuel flow
measurement; an approximated engine load; a calculated exhaust
flow; the engine brake specific fuel consumption (BSFC); and all
raw data readings on individualized windows-style tab pages. The
user may make adjustments to the engine and view resultant levels
in real-time (272). WinStack.TM. repeats the data collection based
on the number of readings selected by the user. (273). Then the
post-calibration error check is performed (274), using the same
procedure as the pre-calibration error check (FIG. 11).
WinStack.TM. notifies the user if any sensors fail the post-test
calibration check (275). Once the test is complete, all raw data is
saved to the database to allow report generation at a time of the
user's choosing.
[0197] As shown in FIG. 4, when the user wishes to use the Catalyst
Efficiency test mode, two gas analyzers are used: an upstream gas
analyzer (136), which draws exhaust gas from upstream of the
catalyst element (134) and a downstream gas analyzer (138) which
draws exhaust gas from downstream of the catalyst element (134). As
well, two temperature sensors are used: an upstream temperature
sensor (140) which sense the exhaust temperature upstream of the
catalyst element (134) and a downstream temperature sensor (138)
which senses the exhaust temperature downstream of the catalyst
element (134).
[0198] As shown in FIG. 12, when the user selects the Catalyst
Efficiency test mode, WinStack.TM. prompts the user to enter, into
the appropriate fields, the following data: the facility location,
the relevant environmental board; the gas analyzer serial number;
the facility operator; an identifier for the person performing the
emission test; the ambient conditions at the test site; and whether
a Source or Compliance test will be performed (280). The ambient
conditions are the ambient barometric pressure and ambient
temperature, which are measured by any suitable means.
[0199] WinStack.TM. then requires the user to select an engine
model to test (282). WinStack.TM. lists engine models based on the
manufacturer, aspiration (natural or turbo-charged) and the
combustion (rich burn or lean burn). WinStack.TM. then permits the
user to set the total number of readings to be recorded during a
test, and the time interval between each reading (284).
[0200] WinStack.TM. then displays the previously entered data;
checks for blank fields or erroneous inputs and notifies the user
if there is an error in the input data; and permits the user to
adjust or correct any values through the `Preferences` section of
the menu (286). The test data and ambient condition data are saved
to the WinStack.TM. database for later retrieval and report
generation. Once the user indicates that the user is satisfied with
the entries, WinStack.TM. goes into the data acquisition mode.
[0201] WinStack.TM. then displays all the data channels coming from
the data collection buffer (288). The display is configured so as
to make a viewer aware of any unexpected inputs (ie: inputs that
are not within the expected channel ranges) (290), so as to permit
the user to remedy a faulty sensor, or correct a situation where a
sensor has not been installed or connected properly.
[0202] When the user is satisfied that all sensors are reading
correctly, the user then instructs WinStack.TM. to commence the
pre-test calibration error phase. In the Catalyst Efficiency test
mode, WinStack.TM. goes through the same pre-test calibration error
test as it does in the Emission Source/Compliance test mode, except
that the calibration error tests are performed on two gas analyzers
(292, 294, 296 and 298).
[0203] Once the user is satisfied with the pre-test calibration
error tests, the user instructs WinStack.TM. to commence testing.
WinStack.TM. waits for the chosen delay period and then accepts
measurements from the data collection buffer (300). WinStack.TM.
transfers the sensed data to the computer memory for analysis and
plotting (302). WinStack.TM. calculates and displays, in real time,
any difference in the upstream and downstream levels of NO,
NO.sub.2 CO the CO.sub.2. WinStack.TM. compares the upstream
temperature to the temperature necessary to stimulate the desired
chemical reaction between the catalyst element and the exhaust gas.
WinStack.TM. also displays the temperature differential between the
upstream and downstream exhaust gas, which is an indicator of the
extent to which the desired exothermic reaction is occurring. The
user may tune the engine if required (304). WinStack.TM. repeats
the data acquisition and processing steps for the previously
entered test duration (306), providing real time feedback for any
tuning or adjustments made by the user.
[0204] As shown in FIG. 13, when the user selects the Engine
Optimization test mode, WinStack.TM. prompts the user to enter,
into the appropriate fields, the following data: the facility
location, the relevant environmental board; the gas analyzer serial
number; the facility operator; and an identifier for the person
performing the emission test (310). Then the user enters the
ambient conditions at the test site (312), being the ambient
barometric pressure and ambient temperature, which are measured by
any suitable means.
[0205] WinStack.TM. then prompts the user to select an engine model
to test (314). WinStack.TM. lists engine models based on the
manufacturer, aspiration (natural or turbo-charged) and the
combustion (rich burn or lean burn). WinStack.TM. will present the
user with a set of load curves that pertain to the engine model
selected. The user selects the curve that most closely matches
current field conditions (316).
[0206] To approximate the engine load, WinStack.TM. correlates the
measured intake manifold temperature and pressure with the engine
manufacturer's load curves (which relate intake manifold pressure
and temperature with engine load) and corrects for ambient
temperature and barometric pressure (already entered by the user)
per the manufacturer's guidelines. WinStack.TM. uses Newton's
Interpolation Method to approximate the engine load at temperature
and pressure measurements that do not fall at the discrete points
defined by the load curve representations.
[0207] In order to approximate the engine brake specific fuel
consumption (BSFC), WinStack.TM. must obtain a corrected fuel flow
rate. WinStack.TM. prompts the user to validate the model of flow
meter that will be used to measure the fuel and enter a K-factor
based on the most recent calibration of the flow meter [45]. The
user then enters a recent fuel gas composition (318). WinStack.TM.
can calculate the gross calorific value and the molecular weight of
the fuel based on the fuel gas composition, or have the user
directly enter these parameters from a fuel gas composition sheet.
WinStack.TM. then calculates the pseudo critical properties of the
fuel gas (320), which are required for the fuel gas compressibility
calculation. WinStack.TM. then permits the user to set the total
number of readings to be recorded during a test, and the time
interval between each reading (322). WinStack.TM. then displays the
previously entered data (324), and permits the user to adjust or
correct any values through the `Preferences` section of the menu.
Once the user indicates that the user is satisfied with the
entries, all data calculated and recorded during this step is saved
to the WinStack.TM. database for later retrieval and report
generation; and WinStack.TM. goes into the data acquisition
mode.
[0208] WinStack.TM. then displays all the data channels coming from
the data collection buffer (326). The display is configured so as
to make a viewer aware of any unexpected inputs (ie: inputs that
are not within the expected channel ranges) (328), so as to permit
the user to remedy a faulty sensor, or correct a situation where a
sensor has not been installed or connected properly.
[0209] WinStack.TM. then prompts the user to select either line or
bar graph format for real-time graphical display purposes. When the
user instructs WinStack.TM. to start the test, WinStack.TM. waits
for the chosen delay period and then accepts raw data from the data
collection buffer at the time interval previously stipulated by the
user (330). WinStack.TM. transfers the data to the computer memory
for analysis and plotting (332). WinStack.TM. calculates an
approximated brake specific fuel consumption (BSFC) from the
approximated engine load determined from the intake manifold
pressure and temperature measurements; the corrected fuel gas flow;
and the gross calorific value of the fuel. WinStack.TM. displays
the real-time BSFC, corrected fuel flow measurement, and
approximated engine load, on individualized windows-style tab
pages. The user may make adjustments to the engine (334) and view
the effects in real-time. WinStack.TM. repeats the data collection
based on the number of readings selected by the user (336). Once
the test is complete, all the raw data is saved to the database to
allow report generation at a later date.
[0210] The foregoing is a description of a preferred embodiment of
the invention which is given here by way of example. The invention
is not to be taken as limited to any of the specific features as
described, but comprehends all such variations thereof as come
within the scope of the appended claims.
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