Robust flow parameter model for component-level dynamic turbine system control

• US 8,668,434 B2
• Filed: 09/02/2009
• Issued: 03/11/2014
• Est. Priority Date: 09/02/2009
• Status: Active Grant

• Current Assignee: Rtx Corporation
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: Karpman, Boris, Meisner, Richard P., Roadinger, Thomas J.
• Primary Examiner(s): Wiehe, Nathaniel
• Assistant Examiner(s): BROWN, ADAM WAYNE
• Application Number:
  US12/552,711
• Publication Number:
  US 20110052370A1
• Time in Patent Office: 1,651 Days
• Field of Search: 415/17, 415/26, 415/160, 700/28, 700/29
• US Class Current: 415/7
• CPC Class Codes: F01D 21/003 Arrangements for testing or measuring for measuring vibrations G01H
• CPC Class Codes: F02C 9/16 Control of working fluid flow F02C9/48 takes precedence; control of air-intake flow F02C7/057
• CPC Class Codes: F04D 27/0261 by varying driving speed
• CPC Class Codes: F05D 2270/101 Compressor surge or stall
• CPC Class Codes: G05D 7/0635 by action on throttling means G05D7/0688, G05D7/0694 take precedence
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A system comprises an apparatus, an actuator and a processor. The apparatus defines a flow path through an aperture, the aperture defines a pressure drop along the flow path, and the actuator regulates fluid flow across the pressure drop. The processor comprises a flow module, a comparator, an estimator and a control law. The flow module maps a flow curve relating a flow parameter to a pressure ratio, and defines a solution point located on the flow curve and a focus point located off the flow curve. The comparator generates an error as a function of a slope defined between the focus and solution points. The estimator moves the solution point along the flow curve, such that the error is minimized. The control law directs the actuator to position the control element, such that the flow parameter describes the fluid flow and the pressure ratio describes the pressure drop.

Claims

1. A system comprising:

an apparatus defining a flow path through an aperture, the aperture defining a pressure drop along the flow path;

an actuator for regulating fluid flow across the pressure drop by positioning a control element in the apparatus; and

a processor for controlling the actuator, the processor comprising;

an open loop module modeling at least one flow parameter relationship relating a flow parameter and a pressure ratio to a slope of a solution line from a focal point to a solution point on a flow curve, and configured to generate an error in the flow parameter or the pressure ratio as a function of the slope;

an estimator configured to minimize the error by varying slope, and thereby varying the solution point; and

a control law configured to direct the actuator based on estimated feedback that is a function of the slope.

2. The system of claim 1, wherein the open loop module generates the error by comparing the flow parameter to a constrained value determined by evaluating the flow curve at the solution point.

3. The system of claim 1, wherein the open loop module generates the error by comparing the pressure ratio to a constrained value determined by evaluating the flow curve at the solution point.

4. The system of claim 1, wherein the control law directs the actuator to position the control element under a condition of low fluid flow, such that a slope of the flow curve approaches zero at the solution point.

5. The system of claim 1, wherein the control law directs the actuator to position the control element under a condition of choked fluid flow, such that an inverse slope of the flow curve approaches zero at the solution point.

6. The system of claim 1, wherein the apparatus comprises a turbofan engine including a compressor, a combustor, a turbine, a fan and a bypass duct, and wherein the control law further directs the actuator to position the control element based on a thrust demand for the turbofan engine.

7. The system of claim 6, wherein the aperture comprises a variable-area nozzle positioned in the bypass duct, and wherein the control law directs the actuator to regulate fluid flow through the bypass duct by opening or closing the variable-area nozzle, such that the system controls a bypass ratio while the turbofan meets the thrust demand.

8. The system of claim 6, further comprising a thermodynamic module for modeling heat transfer from the fluid flow to the compressor, and wherein the control law directs the actuator to regulate fluid flow through the aperture by controlling fuel flow to the combustor based on the heat transfer to the compressor, such that the system controls a compressor stall margin while the turbofan meets the thrust demand.

9. The system of claim 6, further comprising a clearance module for modeling clearance in the turbine, and wherein the control law directs the actuator to regulate cooling fluid flow onto the turbine based on the clearance, such that the system controls the clearance while the turbofan satisfies the thrust demand.

10. A method comprising:

defining a fluid flow having a pressure drop across an aperture;

mapping a flow curve relating the fluid flow to the pressure drop;

defining a slope based on a solution point located on the flow curve and a focus point located off the flow curve;

generating a constraint by evaluating the flow curve at the solution point, based on the slope;

generating an error by comparing the fluid flow to the constraint;

estimating the slope by moving the solution state along the flow curve, such that the error is minimized; and

regulating the fluid flow based on a feedback that is a function of the slope, such that the fluid flow and the pressure drop are related by the flow curve at the solution point.

11. The method of claim 10, wherein generating the constraint comprises evaluating the fluid flow at the solution point, and wherein generating the error comprises comparing the fluid flow to the constraint.

12. The method of claim 10, wherein generating the constraint comprises evaluating the pressure drop at the solution point, and wherein generating the error comprises comparing the pressure drop to the constraint.

13. The method of claim 10, wherein defining the fluid flow comprises defining a working fluid flow through a variable area nozzle, and wherein regulating the fluid flow comprises opening or closing the variable area nozzle in order to change the pressure drop.

14. The method of claim 10, wherein defining the fluid flow comprises defining airflow through a compressor, and wherein regulating the fluid flow comprises adjusting a rotational speed of the compressor to control a stall margin of the compressor.

15. The method of claim 14, wherein adjusting the rotational speed of the compressor comprises adjusting the rotational speed based on thermal transport from the airflow to the compressor, such that the stall margin is controlled based on the thermal transport.

16. The method of claim 10, wherein defining the fluid flow comprises defining a cooling fluid flow onto a turbine, and wherein regulating the fluid flow comprises regulating the cooling fluid flow to control clearance in the turbine.

17. A turbine engine comprising:

a compressor, a combustor and a turbine defining a serial flow path for working fluid flow;

an actuator for regulating the working fluid flow by generating a pressure drop along the serial flow path;

a processor for controlling the actuator, the processor comprising;

a flow curve relating a flow parameter describing the working fluid flow to a pressure ratio describing the pressure drop;

an open loop module modeling at least one flow parameter relationship relating a flow parameter and a pressure ratio to a slope of a solution line from a focal point off the flow curve to a solution point on the flow curve, and configured to generate an error in the flow parameter or the pressure ratio as a function of the slope;

an estimator for estimating the slope by moving the solution point along the flow curve, such that the error is minimized; and

a control law for directing the actuator to regulate the working fluid flow based on a feedback that is a function of the slope, such that the flow parameter describes the working fluid flow at the at the solution point.

18. The turbine engine of claim 17, wherein the comparator generates the error by comparing the working fluid flow to a constraint defined by evaluating the flow curve at the solution point.

19. The turbine engine of claim 18, wherein a slope of the flow curve tends to diverge, such that the control law directs the actuator to regulate the working fluid flow in a choked flow condition.

20. The turbine engine of claim 18, wherein the actuator generates the pressure drop by adjusting a variable area nozzle positioned along the serial flow path.