U.S. patent application number 12/151168 was filed with the patent office on 2009-12-31 for torque-based sensor and control method for varying gas-liquid fractions of fluids for turbomachines.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Sergio Boris, Ciro Cerretelli, Michael Bernhard Schmitz, Christof Martin Sihler.
Application Number | 20090324382 12/151168 |
Document ID | / |
Family ID | 41447682 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090324382 |
Kind Code |
A1 |
Schmitz; Michael Bernhard ;
et al. |
December 31, 2009 |
Torque-based sensor and control method for varying gas-liquid
fractions of fluids for turbomachines
Abstract
A torque-based sensor and control method for detecting varying
gas-liquid fractions of a fluid entering a turbomachine that
operates a fluid of varying liquid phases and compositions and
using information about the actual gas-liquid fraction to set a
control algorithm so that it can change the torque and therefore
the rotation speed of the turbomachine to operate at safer
conditions or conditions with higher efficiency or higher power
output.
Inventors: |
Schmitz; Michael Bernhard;
(Freising, DE) ; Boris; Sergio; (San Donato
Milanese, IT) ; Cerretelli; Ciro; (Muenchen, DE)
; Sihler; Christof Martin; (Hallbergnoos, DE) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
SCHENECTADY
NY
|
Family ID: |
41447682 |
Appl. No.: |
12/151168 |
Filed: |
May 5, 2008 |
Current U.S.
Class: |
415/1 ;
415/17 |
Current CPC
Class: |
F04D 27/0261 20130101;
F04D 27/001 20130101 |
Class at
Publication: |
415/1 ;
415/17 |
International
Class: |
F01D 17/08 20060101
F01D017/08 |
Claims
1. A method of controlling a rotating flow machine, the method
comprising: measuring an inlet temperature of the rotating flow
machine and predicting an outlet temperature of the rotating flow
machine therefrom; measuring rotating flow machine shaft torque and
determining mass flow changes at an inlet to the rotating flow
machine therefrom; and controlling rotational speed or torque of
the rotating flow machine shaft in response to the predicted outlet
temperature and the mass flow changes into the rotating flow
machine such that the rotating machine achieves desired operating
conditions in association with changes in gas-volume-fraction at
the inlet to the rotating flow machine.
2. The method according to claim 1, wherein controlling rotational
speed or torque of the rotating flow machine shaft in response to
the predicted outlet temperature and the mass flow changes into the
rotating flow machine comprises inputting the predicted outlet
temperature information and the mass flow change information into a
fluidmechanical algorithmic model configured to generate the
desired operating conditions.
3. The method according to claim 1, wherein the desired operating
conditions are selected from rotating flow machine shaft torque and
rotating flow machine shaft speed.
4. The method according to claim 1, wherein the rotating flow
machine is selected from compressors, turbines, multiphase rotary
pumps, and aircraft engines under rain conditions.
5. The method according to claim 1, further comprising performing
an initial calibration event to determine the actual operating
point of the rotating flow machine, prior to measuring the inlet
temperature and the rotating flow machine shaft torque, and prior
to controlling rotational speed or torque of the rotating flow
machine shaft.
6. A rotating flow machine control system comprising: a flow
machine having a rotational shaft; a torque sensor configured to
measure rotational shaft torque associated with the flow machine;
an algorithmic software configured to determine mass flow changes
at an inlet to the rotating flow machine in response to the
measured rotational shaft torque; a temperature sensor configured
to measure fluidic temperature at an inlet to the flow machine; a
temperature sensor configured to measure fluidic temperature at an
outlet to the flow machine; and a feedback control loop configured
to control rotational shaft speed or rotational shaft torque of the
flow machine in response to the mass flow changes, the fluidic
temperature at the flow machine inlet, and the fluidic temperature
at the flow machine outlet, such that the rotating machine achieves
desired operating conditions in association with changes in
gas-volume-fraction at the inlet to the rotating flow machine.
7. The rotating flow machine control system according to claim 6,
wherein the rotating flow machine is selected from compressors,
turbines, multiphase rotary pumps, and aircraft engines under rain
conditions.
8. The rotating flow machine control system according to claim 6,
wherein the torque sensor is configured to measure and generate
torque information within one rotational cycle of the rotating flow
machine.
9. The rotating flow machine control system according to claim 6,
wherein the torque sensor is at least partially integrated into the
rotational shaft.
10. The rotating flow machine control system according to claim 6,
wherein the torques sensor is based on a magnetically encoded
rotational shaft or magnetically encoded parts attached to the
rotational shaft.
11. The rotating flow machine control system according to claim 6,
wherein the algorithmic software comprises a fluidmechanical model
of the rotating flow machine running under multiphase
conditions.
12. The rotating flow machine control system according to claim 6,
wherein the desired operating conditions are selected from rotating
flow machine shaft torque and rotating flow machine shaft
speed.
13. A rotating flow machine control system comprising: a flow
machine having a rotational shaft; a torque sensor configured to
measure rotational shaft torque associated with the flow machine;
an algorithmic software configured to determine mass flow changes
at an inlet to the rotating flow machine in response to the
measured rotational shaft torque; a fluidic bypass actuator; and a
controller configured to control rotational shaft torque of the
flow machine via causing the fluidic bypass actuator to vary the
amount of fluid entering the inlet to the flow machine in real-time
in response to the mass flow changes, such that the rotating
machine achieves desired operating conditions in association with
changes in gas-volume-fraction at the inlet to the rotating flow
machine.
14. The rotating flow machine control system according to claim 13,
wherein the rotating flow machine is selected from compressors,
turbines, multiphase rotary pumps, and aircraft engines under rain
conditions.
15. The rotating flow machine control system according to claim 13,
wherein the torque sensor comprises a magnetic sensor based on
magnetic encoding of the rotational shaft or parts attached to the
rotational shaft.
16. The rotating flow machine control system according to claim 13,
wherein the torque sensor is at least partially integrated into the
rotational shaft.
17. The rotating flow machine control system according to claim 13,
wherein the algorithmic software comprises a fluidmechanical model
of the rotating flow machine running under multiphase
conditions.
18. A method of controlling a rotating flow machine, the method
comprising: measuring rotating flow machine shaft torque and
determining gas-volume-fraction (GVF) changes at an inlet to the
rotating flow machine therefrom; and controlling rotational speed
or torque of the rotating flow machine shaft in response to the GVF
changes into the rotating flow machine such that the rotating
machine achieves a desired operating point.
19. The method according to claim 18, further comprising measuring
an inlet temperature of the rotating flow machine and predicting an
outlet temperature of the rotating flow machine therefrom.
20. The method according to claim 19, further comprising inputting
the predicted outlet temperature information and the GVF
information into a fluidmechanical algorithmic model configured to
generate the desired operating point.
Description
BACKGROUND
[0001] The invention relates generally to torque sensing and
control systems and methods, and more specifically to a
torque-based sensor and method for controlling machine speed or
torque characteristics in response to varying gas-liquid fractions
of fluids for a rotating flow machine.
[0002] Incoming fluid in many turbomachinery applications is
comprised of two or more components such as water and air, or
methane, water and sand. These incoming fluid compositions can vary
significantly over time. In most cases, the gas-volume-fraction
(GVF) is significantly larger than the liquid/solid-volume
fraction. The gas-mass-fraction and the liquid-mass-fraction
however, can be equally large. Small changes in volume fraction of
one or the other phase can result in significant changes on the
incoming overall mass to the turbomachine. This means that the
shaft torque changes significantly due to the changes in gas-volume
fraction.
[0003] Control of turbomachine operating conditions in some
applications typically includes direct measurements of fluids
comprised of multiple species that are difficult to ascertain,
especially under dynamic conditions. Therefore, only temperatures
are determined at some representative points on the casing of a
turbomachine. The operating conditions are then adjusted according
to calibration data obtained during tests. Fluid mechanical models
are sometimes used to assist this calibration approach.
[0004] Other turbomachine control techniques employ venture nozzles
and dual-energy fraction meters based on nuclear detection
technology to assist in adjustment of turbomachine operating
conditions. An external device comprising a multiphase flow meter
is required to be calibrated to the drive-motor-compressor train
including the inlet pipeline conditions when using the above
described techniques.
[0005] It would be both advantageous and beneficial to provide a
device that is able to quantify directly the impact of changing GVF
on a turbomachine compressor such that the quantified information
can be used to counteract disadvantageous turbomachine behavior
associated with centrifugal compressors employed in the oil and gas
industry. It would be further advantageous if the device could be
just as easily applied to many types of rotating flow machines such
as steam turbine, multiphase rotating pumps, and aircraft engines
under rain conditions to quantify directly the impact of changing
GVF on the respective rotating flow machine(s).
BRIEF DESCRIPTION
[0006] Briefly, in accordance with one embodiment, a method of
controlling a rotating flow machine comprises:
[0007] measuring an inlet temperature of the rotating flow machine
and predicting an outlet temperature of the rotating flow machine
therefrom;
[0008] measuring rotating flow machine shaft torque and determining
mass flow changes at an inlet to the rotating flow machine
therefrom; and
[0009] controlling rotational speed or torque of the rotating flow
machine shaft in response to the predicted outlet temperature and
the mass flow changes into the rotating flow machine such that the
rotating machine achieves desired operating conditions in
association with changes in gas-volume-fraction at the inlet to the
rotating flow machine.
[0010] According to another embodiment, a rotating flow machine
control system comprises:
[0011] a flow machine having a rotational shaft;
[0012] a torque sensor configured to measure rotational shaft
torque associated with the flow machine;
[0013] an algorithmic software configured to determine mass flow
changes at an inlet to the rotating flow machine in response to the
measured rotational shaft torque;
[0014] a temperature sensor configured to measure fluidic
temperature at an inlet to the flow machine;
[0015] a temperature sensor configured to measure fluidic
temperature at an outlet to the flow machine; and
[0016] a feedback control loop configured to control rotational
shaft speed or rotational shaft torque of the flow machine in
response to the mass flow changes, the fluidic temperature at the
flow machine inlet, and the fluidic temperature at the flow machine
outlet, such that the rotating machine achieves desired operating
conditions in association with changes in gas-volume-fraction at
the inlet to the rotating flow machine.
[0017] According to yet another embodiment, a rotating flow machine
control system comprises:
[0018] a flow machine having a rotational shaft;
[0019] a torque sensor configured to measure rotational shaft
torque associated with the flow machine;
[0020] an algorithmic software configured to determine mass flow
changes at an inlet to the rotating flow machine in response to the
measured rotational shaft torque;
[0021] a fluidic bypass actuator; and
[0022] a controller configured to control rotational shaft torque
of the flow machine via causing the fluidic bypass actuator to vary
the amount of fluid entering the inlet to the flow machine in
real-time in response to the mass flow changes, such that the
rotating machine achieves desired operating conditions in
association with changes in gas-volume-fraction at the inlet to the
rotating flow machine.
[0023] According to still another aspect of the invention, a method
of controlling a rotating flow machine comprises:
[0024] measuring rotating flow machine shaft torque and determining
gas-volume-fraction (GVF) changes at an inlet to the rotating flow
machine therefrom; and
[0025] controlling rotational speed or torque of the rotating flow
machine shaft in response to the GVF changes into the rotating flow
machine such that the rotating machine achieves a desired operating
point.
DRAWINGS
[0026] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0027] FIG. 1 illustrates a rotating flow machine control system
according to one embodiment of the invention; and
[0028] FIG. 2 illustrates a rotating flow machine control system
according to another embodiment of the invention.
[0029] While the above-identified drawing figures set forth
particular embodiments, other embodiments of the present invention
are also contemplated, as noted in the discussion. In all cases,
this disclosure presents illustrated embodiments of the present
invention by way of representation and not limitation. Numerous
other modifications and embodiments can be devised by those skilled
in the art which fall within the scope and spirit of the principles
of this invention.
DETAILED DESCRIPTION
[0030] The torque of a rotating flow machine shaft such as a
turbomachine shaft depends on the overall mass flow through the
turbomachine and the specific enthalpy change through the machine.
This can be described by the change in temperature for cases in
which the fluid composition is known. In those cases, the
measurements at the inlet and outlet of the turbomachine are
relatively easy to obtain and are sufficient to determine the
operating point of the turbomachine. The operating point of an
electrical motor-driven compressor can easily be controlled by
changing the rotational speed of the compressor. Undesired
operating points, such as points close to or beyond the surge/stall
limit of a compressor, can be avoided by changing the speed of
revolution such as described below with reference to FIG. 1 or by
bypassing parts of the fluid such as described below with reference
to FIG. 2. Incoming and outgoing flow properties are not easily
determined however, when multiphase flows are involved in the
process.
[0031] The present inventors recognized that changes in the shaft
torque itself can be used to determine the operating point, i.e.
incoming changes in mass flow, provided that the principle fluid
components do not change over periods of the order of the speed of
revolution of the turbomachine, but only to the composition of the
fluid, i.e. GVF. The changes in mass flow in this instance are
related only to the changes of the fluid composition.
[0032] The exit temperature of the liquid compressed or expanded in
a turbomachine is also a function of the GVF. Changes in the GVF at
the inlet however, will be detected as changes in the exit
temperature associated with larger time scales than the changes in
mass flow caused by changes in the GVF. The latter can be detected
almost instantaneously via a torque sensor; while changes in the
exit temperature are on the order of the convection time of a
particle that travels through the flow channel of a
turbomachine.
[0033] This feature was recognized by the present inventors to
provide a flow machine control system 10 described below with
reference to FIG. 1. A fluid mechanical model is used to predict
the temperature of the fluid composition exiting the turbomachine,
including consideration of condensation or evaporation. This
predicted temperature, together with the measured torque/GVF, is
then used to determine the direction of change of rotation, i.e.
speed-up or slow-down.
[0034] The actual exit temperature is then measured at the
operating point, and is used together with the model based
predictions to iterate the operating point and close an iteration
loop. The minimum sensor information requirements therefore include
temperatures at the inlet and exit of the compressor, as well as
the rotational speed. Mass flow at an initial point in time, i.e. a
dry gas calibration point, is only required since the technique
described herein detects changes in the mass flow.
[0035] Looking now at FIG. 1, a rotating flow machine control
system 10 is illustrated according to one embodiment of the
invention. The rotating flow machine control system 10 includes a
compressor 12; although the principles described herein are equally
applicable to any type of rotating flow machine such as, without
limitation, a turbomachine, i.e. steam turbine, multiphase rotary
pumps, and aircraft engines under rain conditions.
[0036] Compressor 12 is driven by a suitable drive motor 14. A
power control module 16 includes algorithmic software 18 described
in further detail below, and is configured to control the
rotational speed and/or torque characteristics of the drive motor
14.
[0037] A torque sensor 20 is configured to measure the torque on
the motor/compressor shaft 22, while temperature sensors 24, 26 at
the respective compressor fluidic input and output ports 28, 30 are
each configured to measure its corresponding fluidic
temperature.
[0038] The algorithmic software 18 is configured to determine mass
flow changes at the inlet 28 to the compressor 12 in response to
the measured rotational shaft torque.
[0039] A feedback control loop 32 is configured to control the
rotational shaft 22 speed or rotational shaft 22 torque of the flow
machine 12 in response to the mass flow changes determined via the
algorithmic software 18, the fluidic temperature at the flow
machine inlet 28, and the fluidic temperature at the flow machine
outlet 30, such that the rotating machine/compressor 12 achieves
desired operating conditions in association with changes in
gas-volume-fraction at the inlet to the rotating flow machine
12.
[0040] In summary explanation, torque sensing and control methods
detect varying gas-liquid fractions of a fluid entering a rotating
flow machine 12 that operates with a fluid having variable liquid
phases and compositions. A changing liquid composition results in a
respective changing torque on the rotating shaft 22 of the rotating
flow machine 12. The measured shaft torque is then used to detect
the gas-liquid fraction; and this information is fed to a control
algorithm 18 that controls the operating point of the rotating flow
machine 12.
[0041] Setting the control algorithm 18 so that it can change the
torque and therefore the rotational speed of the rotating flow
machine 12 in response to information about the actual gas-liquid
fraction is desirable to achieve safer operating conditions or
conditions with higher efficiency or higher power output under
varying liquid compositions that otherwise result in varying torque
on the rotating shaft 22 of the rotating flow machine 12, leading
eventually to damages to the rotating flow machine 12 under
unwanted operating conditions sometimes close or beyond the stall
or surge limit(s).
[0042] The rotating flow machine control system 10 is therefore
based on high-speed torque acquisition that is used to determine
the gas volume fraction at the rotating flow machine inlet 28.
Moreover, the sensed signal from the torque sensor 20 is fed into a
power control module 16 feedback control loop 32 to determine an
improved operating point for the rotating flow machine 12 that
better suits the needs of the new fluid composition.
[0043] FIG. 2 illustrates a rotating flow machine control system 50
according to another embodiment of the invention. The rotating flow
machine control system 50 includes a compressor 12; although the
principles described herein are equally applicable to any type of
rotating flow machine such as, without limitation, a turbomachine,
i.e. steam turbine, multiphase rotary pumps, and aircraft engines
under rain conditions.
[0044] Compressor 12 is driven by a suitable drive motor 14. A
controller 52 includes algorithmic software 54 described in further
detail below, and is configured in combination with a shaft torque
sensor 20 to control a fluid bypass actuator 56 in response to the
rotational shaft 22 torque of the compressor 12.
[0045] The algorithmic software 54 is configured to determine mass
flow changes at the inlet 28 to the compressor 12 in response to
the measured rotational shaft torque. This information is then used
to control the amount of fluid flowing through the compressor inlet
28 in real-time via a fluid bypass actuator 56, such that the
rotating machine/compressor 12 achieves desired operating
conditions in association with changes in gas-volume-fraction at
the inlet 28 to the rotating flow machine 12. Although described in
terms of a variable speed rotating machine, this technique applies
equally well to fixed speed rotating machines.
[0046] Modern torque sensors based on magnetic shaft encoding can
achieve a measurement repeatability of 99.99% and a signal
bandwidth up to 30 kHz if all primary and secondary sensor design
requirements are fulfilled, requiring an optimized design for each
type of application. Considering and integrating the optimized
sensor design during the design stage of the rotating flow machine
control system 10 enables detection of even very small changes in
volume fraction of one or the other phase in a reliable manner,
allowing this information to be employed in advanced performance
control circuits such as described herein.
[0047] A flow machine control system such as described herein with
reference to the Figures can be configured, without limitation, for
use with a variable speed motor to drive a compressor or for use
with a variable speed energy generator to drive a turbine (or with
fixed speed machines). The control system in each instance provides
for fast reaction times suitable for changing mass flow, shaft
speed and/or torque.
[0048] A fast reacting torque sensor for turbomachinery operated at
10,000 rpm requires a reaction within 6 msec, which equates to one
rotational cycle. State of the art shaft encoded torque sensors
have signal bandwidths up to 30 kHz, as stated above, meaning that
they can detect events on a 30 microsecond time scale. Such sensors
however may be limited in use as an input for control circuits
since they may also be sensitive to electromagnetic or other
disturbances.
[0049] Using the output of a torque sensing system in association
with fast acting controls in one embodiment requires a special
sensor design, especially if real-time behavior of the sensed
signal is needed, i.e. improving the signal quality by filtering or
standard signal processing methods cannot be applied. This sensor
design according to one embodiment requires shielding of the
magnetic field sensing coils against external electromagnetic
disturbances. The magnetic field sensing coils, for example, must
be positioned inside of a metallic tube (alternatively a
cylindrical metallic cover around the shaft). In addition, multiple
magnetic field sensor pairs according to one embodiment must be
positioned around the shaft 22. They can be used to exclude that
lateral movements of the shaft or external fields that impact the
measurement result, e.g. in performing differential measurements,
comparing and summarizing the relevant field components from
different positions around the shaft, so that only true torque is
measured at all times.
[0050] Alternatively, an integration based shaft power or torque
measurement method could be used to generate a more reliable input
signal for the control algorithm. Such a method may employ a number
of magnetically encoded regions, induction coils and integration
sections configured to provide a required time resolution for
specific applications, e.g. 1 ms. Air core induction coils can be
employed in a solution that allows their application in a much
higher temperature range than permanent magnetic field sensing
solutions.
[0051] In further summary explanation, a torque-based sensor and
control method have been described for rotational flow control
machines such as a turbomachine that operates on varying gas-liquid
fractions of fluids. According to one aspect, a calibration event
is provided at the beginning of the process. A feedback loop is
provided that feeds the turbomachine shaft torque information back
to a turbomachine control system. Temperature sensors are provided
at an inlet and exit of the turbomachine. A torque sensor is
provided that measures the rotational speed of the turbomachine.
Known information about the liquid components, i.e. gas-type,
liquid-type is provided. A fluidmechanical model of the
turbomachine running under multiphase conditions is provided in
which changes in GVF cause a change in overall mass flow.
Turbomachine exit temperature(s) and pressure(s) are predicted
based on the measured speed and inlet temperature(s). A new
operating point is predicted via the fluidmechanical model; and if
this operating point is unwanted, the rotational speed or a bypass
mechanism or other installed means to influence the operating point
of the turbomachine can be used to change the actual operating
point. A continuous monitoring of the changes in the inlet and exit
quantities then allows a stable settling of a new operating
point.
[0052] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. It is, therefore, to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the
invention.
* * * * *