U.S. patent application number 13/027293 was filed with the patent office on 2011-06-09 for altitude compensation system for controlling smoke emissions from a naturally aspirated railroad locomotive.
Invention is credited to Neil Xavier Blythe, Bryan Thomas Jett, Ajith Kumar, Mikhail Meltser.
Application Number | 20110132225 13/027293 |
Document ID | / |
Family ID | 39714436 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110132225 |
Kind Code |
A1 |
Meltser; Mikhail ; et
al. |
June 9, 2011 |
ALTITUDE COMPENSATION SYSTEM FOR CONTROLLING SMOKE EMISSIONS FROM A
NATURALLY ASPIRATED RAILROAD LOCOMOTIVE
Abstract
A railroad locomotive includes a naturally-aspirated
reciprocating internal combustion engine, and a traction generator
driven by the engine. A throttle position sensor produces a signal
corresponding to the throttle position selected by the locomotive's
operator. A load regulator receives a speed signal derived from the
throttle position signal and outputs an excitation signal for the
traction generator which is modified by a controller in response to
air availability so that engine speed and load are controlled
independently of the selected throttle position, so as to limit the
exhaust smoke output of the engine.
Inventors: |
Meltser; Mikhail; (US)
; Jett; Bryan Thomas; (US) ; Blythe; Neil
Xavier; (US) ; Kumar; Ajith; (US) |
Family ID: |
39714436 |
Appl. No.: |
13/027293 |
Filed: |
February 15, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11678211 |
Feb 23, 2007 |
|
|
|
13027293 |
|
|
|
|
Current U.S.
Class: |
105/62.1 |
Current CPC
Class: |
F02D 41/021 20130101;
F02D 29/06 20130101; F02B 3/06 20130101; F02D 29/02 20130101; F02D
2200/0414 20130101; F02B 2075/027 20130101; F02B 2075/025 20130101;
F02D 11/106 20130101; F02D 41/0205 20130101; B61C 5/02 20130101;
F02D 2200/703 20130101; B61C 17/04 20130101 |
Class at
Publication: |
105/62.1 |
International
Class: |
B61C 5/00 20060101
B61C005/00 |
Claims
1. A rail vehicle, comprising: a naturally-aspirated, reciprocating
internal combustion engine normally operated at a plurality of
predetermined throttle positions corresponding to discrete engine
speed and load points; a traction generator driven by said engine;
a throttle position sensor for generating a throttle position
signal corresponding to the throttle position selected by an
operator; a load regulator for receiving a speed signal derived
from said throttle position signal, with the load regulator
outputting an excitation signal for said traction generator; and a
controller for receiving at least said throttle position signal,
said excitation signal, and an air availability signal, with said
controller modifying said throttle position signal and said
excitation signal in response to at least the value of said air
availability signal, so that engine speed and load are controlled
independently, based upon the selected throttle position, whereby
the exhaust smoke output of the engine will be mitigated.
2. A rail vehicle according to claim 1, wherein said engine
comprises a four-stroke cycle diesel engine.
3. A rail vehicle according to claim 1, wherein said engine
comprises a blower-scavenged, two-stroke cycle diesel engine.
4. A rail vehicle according to claim 1, further comprising an
engine governor for controlling both said load regulator and a fuel
supply system for said engine, with said governor controlling the
amount of fuel being supplied to the engine in response to the
modified throttle position signal and the modified excitation
signal.
5. A rail vehicle according to claim 1, wherein said air
availability signal corresponds to ambient barometric pressure.
6. A rail vehicle according to claim 1, wherein said engine
comprises a blower scavenged two-stroke cycle engine and said air
availability signal corresponds to air pressure within an airbox
located within said engine.
7. A rail vehicle, comprising: a naturally-aspirated, reciprocating
internal combustion engine normally operated at a plurality of
predetermined throttle positions corresponding to discrete engine
speeds and air/fuel ratios; a traction generator driven by said
engine; a throttle position sensor for generating a throttle
position signal corresponding to the throttle position selected by
an operator; a load regulator for receiving said speed signal and
for outputting an excitation signal for said traction generator;
and a controller for receiving at least said throttle position
signal, said excitation signal, and an air availability signal,
with said controller modifying said throttle position signal and
said excitation signal in response to a decrease in air
availability, so that engine speed and air fuel ratio are
controlled independently of the selected throttle position, whereby
the air/fuel ratio, and corresponding smoke output of the engine,
may be reduced.
8. A rail vehicle, comprising: a naturally-aspirated, reciprocating
internal combustion engine normally operated at a plurality of
predetermined throttle positions corresponding to discrete engine
speeds and air/fuel ratios; a throttle position sensor for
generating a throttle position signal corresponding to the throttle
position selected by an operator; and a controller for receiving at
least said throttle position signal and a signal indicative of air
availability, with said controller acting to reduce an air/fuel
ratio of the engine in operation, below an air/fuel ratio
associated with the throttle position selected by the operator,
when the air availability decreases below a threshold value.
9. A method for modifying the air/fuel ratio control of a naturally
aspirated reciprocating internal combustion engine powering a
fraction generator in a rail vehicle having a manually settable
throttle with a plurality of positions corresponding to
predetermined engine speeds and engine loads, so as to control
smoke caused by varying air availability, comprising: providing a
single control module having an air availability sensing device and
a throttle position monitor; determining, by the control module, a
desired engine speed and desired load, drawn from said
predetermined engine speeds and loads, based upon the throttle
setting and sensed air availability; modifying, by the control
module, a main generator excitation signal in response to the
desired load; and transmitting the modified excitation signal to
the traction generator to control the engine load, while
controlling the engine speed to the desired engine speed.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/678,211 filed on Feb. 23, 2007.
FIELD OF THE INVENTION
[0002] The present invention relates to a system for controlling
smoke emissions from a a naturally aspirated locomotive by
controlling the locomotive's air/fuel ratio and output in response
to operation at barometric pressures characteristic of varying
altitudes.
DISCLOSURE INFORMATION
[0003] Naturally aspirated railroad locomotives typically are
powered by compression ignition "diesel" engines. Such engines may
be either four-stroke cycle or two-stroke cycle engines.
Four-stroke naturally aspirated engines have no charge air booster
such as a turbocharger or a supercharger. Two-stroke cycle diesel
engines used in railroad locomotives are typically scavenged with a
positive displacement blower such as a Roots-type blower.
Notwithstanding the use of blower scavenging, such engines
typically operate in a manner similar to naturally aspirated
engines because the Roots blower or other type of positive
displacement blower merely serves to force exhaust gases from the
engine's cylinders at a pressure only slightly above atmospheric
pressure, with the result that the airbox supplying the engine
cylinders or intake manifold operates very closely to ambient air
pressure.
[0004] Naturally aspirated railroad locomotives are, of course,
subject to operation at altitude, and at higher altitudes, say
above 2500 feet, operation may be characterized by production of
excessive exhaust smoke. This smoke results from the lack of oxygen
at higher altitudes.
[0005] Naturally aspirated locomotives are usually calibrated so
that the engine powering the locomotive operates at one of eight
throttle positions ("notches") characteristic of different engine
speeds and loads. Accordingly, each notch is usually calibrated at
a different air/fuel ratio, with notch 1, the lowest engine speed
having the leanest air/fuel ratio or highest numerical air/fuel
ratio, and notch 8 characterized by the highest engine speed and
the richest, or lowest numerical air/fuel ratio. It is easily seen
that if a naturally aspirated locomotive is operated at high
altitude at the higher notches, e.g., 6, 7 and 8, smoking may occur
due to the richer fuel calibration at the higher notches, coupled
with lack of oxygen availability.
[0006] It would be desirable to control air/fuel ratio with minimal
modification to the engine operating system commonly used on
naturally aspirated locomotives, so as to reduce the production of
smoke when the engine is operated at higher altitudes.
SUMMARY OF THE INVENTION
[0007] According to an aspect of the present invention, a railroad
locomotive includes a naturally-aspirated reciprocating internal
combustion engine normally operated at a plurality of predetermined
throttle positions corresponding to a discrete engine speed and
load points. A traction generator is driven by the engine. A
throttle position sensor generates a throttle position signal
corresponding to the throttle position selected by the locomotive's
operator. A load regulator receives a speed signal derived from the
throttle position signal and outputs an excitation signal for the
traction generator. A controller receives at least the throttle
position signal, the excitation signal, and an air availability
signal, with the controller modifying the throttle position signal
and the excitation signal in response to at least a value of the
air availability signal, so that engine speed and load are
controlled independently, based upon the selected throttle
position, whereby exhaust smoke output of the engine will be
mitigated.
[0008] According to another aspect of the present invention, the
engine incorporated in a railroad locomotive may be either a
four-stroke cycle diesel engine, or a blower-scavenged two-stroke
cycle diesel engine. In either case, an engine governor controls
both the load regulator and a fuel supply system for the engine,
with the governor controlling the amount of fuel being supplied to
the engine in response to the modified throttle position signal and
the modified excitation signal.
[0009] According to an aspect of the present invention, the
controller may optionally receive an ambient air temperature signal
in addition to throttle position signal, excitation signal, and the
air availability signal.
[0010] In general, according to another aspect of the present
invention, the air availability signal corresponds to ambient
barometric pressure.
[0011] According to another aspect of the present invention, the
throttle positions correspond to predetermined engine speeds and
air/fuel ratios, with the controller modifying the throttle
position signal and the excitation signal so that the engine is
operated at a greater engine speed and higher air/fuel ratio than
the engine speed and air/fuel ratio normally associated with a
given throttle position if the locomotive is operated at an air
availability less than a predetermined air availability.
[0012] According to another aspect of the present invention, a
method for controlling the air/fuel ratio of a naturally-aspirated
reciprocating fuel injected internal combustion engine powering a
traction generator in a railroad locomotive having a throttle with
discrete, predetermined, operator-selectable throttle positions
corresponding to predetermined engine speeds and loads includes
monitoring the selected throttle position at which the locomotive
is being operated, while determining air availability. If air
availability decreases below an air availability threshold, the
engine will be operated at a speed greater than the speed
corresponding to the selected throttle position, while the quantity
of fuel injected per stroke is reduced, so that the power of the
engine is maintained in accordance with the selected throttle
position, while increasing the air/fuel ratio so as to mitigate the
amount of exhaust smoke produced by the engine. In essence, the
power output of the engine will be pushed downward to the power
output at a lower notch setting in some cases, thus establishing
that the engine speed and load are controlled independently, based
upon the selected throttle position.
[0013] According to another aspect of the present invention, smoke
output of the engine is reduced by controlling engine speed and
air/fuel ratio independently of the selected throttle positions,
such that the air/fuel ratio may be moved to a more fuel-lean
position than would otherwise be the case with fixed throttle notch
positions corresponding to fixed engine speed and fixed load.
[0014] According to another aspect of the present invention, a
method for modifying the air/fuel ratio control of a naturally
aspirated reciprocating internal combustion engine powering a
traction generator in a railroad locomotive having a manually
settable throttle with a plurality of positions corresponding to
predetermined engine speeds and engine loads, so as to control
smoke caused by varying air availability, includes providing a
single control module having an air availability sensing device and
a throttle position monitor, and determining a desired engine speed
and desired load, based upon the throttle setting and sensed air
availability. The controller will modify a main generator
excitation signal in response to the desired load and transmit the
modified excitation signal to the traction generator to control the
engine load, while controlling the engine speed to the desired
engine speed.
[0015] It is an advantage of a method and system according to the
present invention that excessive smoke emissions of a naturally
aspirated railroad locomotive may be controlled without the need
for costly aftertreatment devices.
[0016] It is yet another advantage of the present invention that
smoke emissions may be controlled without the need for costly
retrofitting of modified fuel injection hardware.
[0017] It is yet another advantage of a method and system according
to the present invention that smoke emissions may be limited
without causing deration while operating at low to moderate
altitudes and at lower to moderate throttle settings.
[0018] Other advantages, as well as features of the present
invention, will become apparent to the reader of this
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a perspective view of a railroad locomotive having
an engine control system according to the present invention.
[0020] FIG. 2 is a schematic representation of a portion of a
control system according to the present invention.
[0021] FIG. 3 is a plot showing discrete combined engine air/fuel
ratio and speed operating points which are adjusted according to an
aspect of the present invention.
[0022] FIG. 4 is a table showing the result of engine control
adjustments according to an aspect of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] As shown in FIG. 1, railroad locomotive 10 has a naturally
aspirated reciprocating internal combustion engine 14, which may
comprise either a four-stroke cycle diesel engine, or a
blower-scavenged two-stroke cycle diesel engine, or other type of
reciprocating internal combustion engine suitable for use with the
present invention. Thus, as used herein, the term "naturally
aspirated" refers to either a four-stroke cycle engine without any
type of charge air booster, or a two-stroke cycle engine using
blower scavenging.
[0024] Engine 14 drives a traction generator 18, which provides
electrical power for operating locomotive 10. As used herein, the
term "generator" means a rotating electrical machine which may be
constituted as either a generator or an alternator.
[0025] FIG. 2 illustrates a control system in which the operator of
the locomotive positions a throttle, typically, at one of eight
notches. The throttle's position is read by throttle position
sensor 22, which outputs a signal to throttle response circuit 26.
In turn, throttle response circuit 26 outputs a notch reference
signal to a controller 50. Throttle response circuit 26 also feeds
a signal to rate control module 30, which allows the output from
throttle response circuit 26 to be ramped up and sent to wheel slip
module 34. The purpose of wheel slip module 34 is to modify the
output of rate control module 30 in the event that wheel slip is
sensed. In general, throttle response circuit 26, rate control
module 30, and wheel slip module 34 are components commonly used in
known railroad locomotives.
[0026] The output of wheel slip module 34 is sent as a modified
throttle or speed signal, to controller 50 and also to load
regulator 46, which is a potentiometer controlled by engine speed
governor 38. Governor 38 also controls fuel injectors 42 to
maintain engine speed at the specified notch setting. The output of
load regulator 46 is an excitation signal which is sent to
generator 18. This excitation signal determines the load imposed by
generator 18 upon engine 14.
[0027] Controller 50 receives the output of load regulator 46 and
modifies the excitation signal in response to at least the value of
the barometric pressure signal from sensor 54. Controller 50 also
may receive inputs from ambient air temperature and humidity
sensors, which are included in a bundle of sensors, 56. Controller
50 may be constituted as either a microprocessor based controller,
or an analog controller, or a relay logic panel, or other type of
controller known to those skilled in the art of machine and engine
control and suggested by this disclosure.
[0028] As shown in FIG. 3, naturally aspirated railroad locomotives
are typically operated at a variety of throttle notches, and for
one particular locomotive, notches 5 through 8 are shown. Each
notch corresponds to a defined engine speed. Additionally, notice
from curve 60 that each notch is characterized by different
air/fuel ratio, with the most fuel rich ratio being at notch 8 and
the most fuel lean ratio being at notch 5. Notches 1-4 (not shown)
would have correspondingly lower air/fuel ratios and lower engine
output. This follows usual practice, because the highest engine
speed and lowest practicable air/fuel ratio give the greatest power
output. Thus, curve 60 of FIG. 3 depicts preset air/fuel ratio as a
function of notch (engine speed).
[0029] FIG. 4 is a table showing the result of engine control
adjustments according to the present invention. Controller 50
monitors air availability, as well as the selected throttle
position at which locomotive 10 is being operated. Air availability
may be measured as by measuring ambient barometric pressure with
sensor 54, or by measuring or determining a surrogate for
barometric pressure, through the use of sensors 56. Such surrogates
include pressure within an engine inlet manifold, engine crankcase,
or the temperature of a fan-cooled device. Other surrogates for air
availability include calculated availability from global position
sensing, measured ambient oxygen concentration, and even a reading
from a manual switch indicating high altitude operation. Yet other
surrogates include measured smoke opacity and normalized exhaust
temperature.
[0030] Regardless of the method used to determine air availability,
controller 50 will act to reduce air/fuel ratio when air
availability decreases below a threshold value. Throttle setting,
or position, is used as a first input to the table of FIG. 4. At
notches N5 and N6, engine speed is increased to the next highest
notch speed, namely notches N6 and N7, respectively. This speed
increase is produced when controller 50 sends a signal to governor
38 to cause governor 38 to increase the speed of engine 14,
notwithstanding that the notch requested by the locomotive operator
remains at N5, or N6, as the case may be. Operating engine 14 at an
increased speed makes more air available for combustion per unit of
time, which permits power output to be maintained with less smoke
at lower notch settings because controller 50 adjusts the output of
load regulator 46, so that the load imposed by traction generator
18 upon engine 14 is reduced, which has the effect of increasing
the air/fuel ratio and decreasing smoke emissions.
[0031] The table of FIG. 4 includes two altitude, or air
availability stages. Stage 1 corresponds to a first air
availability threshold, for example, 2500 ft., but less than a
second air availability threshold, say 4500 ft. Stage 2 corresponds
to altitudes greater than 4500 ft. Those skilled in the art will
appreciate in view of this disclosure that these threshold
altitudes, or air availabilities will vary for different
locomotives.
[0032] At throttle setting N5 of FIG. 4, output is limited to N5
for both Stage 1 and Stage 2. This output is achieved at an engine
speed of N6. At throttle setting N6, output of N6 is achieved at an
engine speed of N7, again for both stages. Deration is not needed
for notches N5 and N6 because these notches require only moderate
power output. Unlike the case with throttle settings at notches N5
and N6, when the throttle is set at notch N7, and with the speed at
N8, output is maintained at N7 for Stage 1, but the lower air
availability at Stage 2 requires duration to output N6, so as to
limit smoke production. At throttle setting N8, deration becomes
more severe, because at Stage 1, output is limited to N7, and at
Stage 2, output is limited to N6.
[0033] FIG. 4 demonstrates that the present system controls engine
speed and load essentially independently of notch position at
certain operating conditions.
[0034] As noted above, a number of surrogates may be employed to
substitute for an unvarnished barometric pressure signal. In
essence barometric pressure is a measure of air or, more
importantly, oxygen availability. In turn, air availability is a
surrogate for oxygen availability. Air availability may be
determined by a number of methods including: measuring pressure
within an inlet manifold associated with said engine; by measuring
pressure within a crankcase associated with the engine; by
measuring output pressure of a cooling system blower located within
the locomotive; by global position sensing and associated lookup of
altitude; by measuring the temperature of the exhaust of the engine
and ambient temperature; by measuring ambient oxygen concentration;
by measuring of exhaust smoke opacity, or by means of a manually
activated high-altitude switch.
[0035] According to another aspect of the present invention a
railroad locomotive may be modified to operate according to the
present invention by providing a single unit control module
incorporating air availability sensing and throttle position
monitoring. The control module will determine a desired engine
speed and desired load, drawn from the population of predetermined
speeds and loads, as shown in FIG. 4, based upon the throttle
setting and sensed air availability. The main generator excitation
signal will be modified in response to the desired load, and the
modified excitation signal will be transmitted to the traction
generator to control the engine load, while controlling the engine
speed to the desired engine speed.
[0036] Although the present invention has been described in
connection with particular embodiments thereof, it is to be
understood that various modifications, alterations, and adaptations
may be made by those skilled in the art without departing from the
spirit and scope of the invention set forth in the following
claims.
* * * * *