Gas turbine engine having a multi-variable closed loop controller for regulating tip clearance

Patent metadata

Field	Value
Publication number	US-9255492-B2
Application number	US-201213682122-A
Country	US
Kind code	B2
Filing date	Nov 20, 2012
Priority date	Dec 14, 2011
Publication date	Feb 9, 2016
Grant date	Feb 9, 2016

Abstract

A gas turbine engine has, in flow series, a compressor section, a combustor, and a turbine section. The gas turbine engine further has a system (i) for cooling the turbine section and (ii) for providing tip clearance control between turbine blades of the turbine section and a plurality of circumferentially distributed segments which form an annular shroud surrounding the outer tips of the turbine blades. The system includes a turbine section cooling sub-system which diverts a first cooling air flow received from the compressor section to a heat exchanger and then to the turbine section to cool components thereof. The first cooling air flow by-passes the combustor and is cooled in the heat exchanger. The turbine section cooling subsystem has a first valve arrangement which regulates the first cooling air flow. The system further includes a tip clearance control sub-system which supplies a second cooling air flow to an engine case to which the segments are mounted. The second cooling air flow regulates thermal expansion of the case and thereby controls the clearance between the segments and the outer tips. The tip clearance control sub-system has a second valve arrangement which regulates the second cooling air flow. The system further includes a closed-loop controller which issues first and second demand signals to respectively the first and the second valve arrangements. Each of the first and second demand signals are determined on the basis of: (i) a value of the first demand signal at a previous time step, and a measurement or estimate of turbine section component temperature, and (ii) a value of the second demand signal at a previous time step, and a measurement or estimate of tip clearance.

First claim

The invention claimed is:

1. A gas turbine engine having, in flow series, a compressor section, a combustor, and a turbine section, and further having a system (i) for cooling the turbine section and (ii) for providing tip clearance control between turbine blades of the turbine section and circumferentially distributed segments which form an annular shroud surrounding outer tips of the turbine blades, the system including:
a turbine section cooling sub-system which diverts a first cooling air flow received from the compressor section to a heat exchanger and then to the turbine section to cool components thereof, the first cooling air flow by-passing the combustor and being cooled in the heat exchanger, and the turbine section cooling sub-system having a first valve arrangement which regulates the first cooling air flow;
a tip clearance control sub-system which supplies a second cooling air flow to an engine case to which the circumferentially distributed segments are mounted, the second cooling air flow regulating thermal expansion of the engine case and thereby controlling a tip clearance between the circumferentially distributed segments and the outer tips of the turbine blades, and the tip clearance control sub-system having a second valve arrangement which regulates the second cooling air flow;
and a closed-loop controller configured to issue first and second demand signals to respectively the first and the second valve arrangements, each of the first and second demand signals being determined on the basis of: (i) a value of the first demand signal at at least one previous time step, and a measurement or estimate of a turbine section component temperature, and (ii) a value of the second demand signal at at least one previous time step, and a measurement or estimate of tip clearance.

2. The gas turbine engine according to claim 1 , wherein the closed-loop controller includes (a) a control unit which calculates each of the first and the second demand signals from a plurality of error variables received by the control unit, from the value of the first demand signal at the at least one previous time step, and from the value of the second demand signal at the at least one previous time step, (b) an observer unit which measures or estimates the turbine section component temperature, measures or estimates the tip clearance, and provides observer variables based on the measurements or estimates, and (c) a comparator unit which compares the observer variables with corresponding target variables to determine the error variables, which are then issued to the control unit.

3. The gas turbine engine according to claim 2 , wherein one of the observer variables provided by the observer unit is a measurement or estimate of the turbine section component temperature, and a corresponding target variable is a target turbine section component temperature.

4. The gas turbine engine according to claim 2 , wherein one of the observer variables provided by the observer unit is a measurement or estimate of the tip clearance, and a corresponding target variable is a target tip clearance.

5. The gas turbine engine according to claims 2 , wherein the observer unit includes a turbine section component temperature model and/or a tip clearance model, and the observer variables determined by the observer unit include a plurality of engine state variables, the corresponding target control values being target engine state variables.

6. The gas turbine engine according to claim 1 , wherein the first valve arrangement includes one or more switched vortex valves.

7. The gas turbine engine according to claim 1 , wherein the heat exchanger is located in a bypass air stream of the gas turbine engine.

8. The gas turbine engine according to claim 1 , wherein the closed-loop controller is configured to issue the first and second demand signals to respectively the first and the second valve arrangements, each of the first and second demand signals being determined on the basis of: (i) the value of the first demand signal at a first time step, and the measurement or estimate of the turbine section component temperature, and (ii) the value of the second demand signal at the first time step, and the measurement or estimate of tip clearance.

9. A method of operating a gas turbine engine having, in flow series, a compressor section, a combustor, and a turbine section, the method including the steps of:
diverting a first cooling air flow received from the compressor section to a heat exchanger and then to the turbine section to cool components thereof, the first cooling air flow by-passing the combustor and being cooled in the heat exchanger;
supplying a second cooling air flow to an engine case to which circumferentially distributed segments are mounted, the circumferentially distributed segments forming an annular shroud around outer tips of turbine blades of the turbine section, and the second cooling air flow regulating thermal expansion of the engine case and thereby controlling a tip clearance between the circumferentially distributed segments and the outer tips;
and issuing first and second demand signals to respectively first and second valve arrangements, the first valve arrangement regulating the first cooling air flow and the second valve arrangement regulating the second cooling air flow, each of the first and second demand signals being determined on the basis of: (i) a value of the first demand signal at at least one previous time step, and a measurement or estimate of turbine section component temperature, and (ii) a value of the second demand signal at at least one previous time step, and a measurement or estimate of tip clearance.

10. The method according to claim 9 , wherein the issuing step includes the sub-steps of:
measuring or estimating the turbine section component temperature,
measuring or estimating the tip clearance,
providing observer variables based on the measurements or estimates,
comparing the observer variables with corresponding target variables to determine a plurality of error variables,
calculating each of the first and the second demand signals from the error variables, from the value of the first demand signal at the at least one previous time step, and from the value of the second demand signal at the at least one previous time step, and
issuing the first and second demand signals to respectively the first and second valve arrangements.

Assignees

• Rolls Royce Plc

Inventors

• Bacic Marko

Classifications

• F01D25/14

  Casings modified therefor (double casings F01D25/26) · CPC title

• F02C9/18

  by bleeding, bypassing or acting on variable working fluid interconnections between turbines or compressors or their stages {(F02C3/113 takes precedence)} · CPC title

• F05D2270/303

  Temperature · CPC title

• F02C6/08

  the gas being bled from the gas-turbine compressor · CPC title

• F05D2260/205

  Cooling fluid recirculation, i.e. after cooling one or more components is the cooling fluid recovered and used elsewhere for other purposes · CPC title