Two-spool turboshaft engine control system and method

• US 8,459,038 B1
• Filed: 02/09/2012
• Issued: 06/11/2013
• Est. Priority Date: 02/09/2012
• Status: Active Grant

• Current Assignee: Williams International Company LLC
• Original Assignee: Williams International Company LLC
• Inventors: Williams, Gregg, Thompson, Robert S. Jr., Lickfold, Ray D.
• Primary Examiner(s): Wongwian, Phutthiwat
• Application Number:
  US13/369,783
• Time in Patent Office: 488 Days
• Field of Search: 60/391.62, 60/391.63, 607/72, 607/73, 607/76, 607/84, 607/85, 607/92
• US Class Current: 60/772
• CPC Class Codes: F02C 3/107 with two or more rotors connected by power transmission
• CPC Class Codes: F02C 9/28 Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed F02C9/30 - F02C9/38, F02C9/44 take precedence
• CPC Class Codes: F02K 3/025 the by-pass flow being at least partly used to create an independent thrust component
• CPC Class Codes: F02K 3/04 the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type
• CPC Class Codes: F05D 2270/05 to affect the output of the engine
• CPC Class Codes: F05D 2270/101 Compressor surge or stall
• CPC Class Codes: F05D 2270/301 Pressure
• CPC Class Codes: F05D 2270/303 Temperature
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A load applied to a low pressure spool of a two-spool turboshaft engine is controlled responsive to inlet pressure and temperature so as to regulate a relationship between the rotational speeds of the low and high pressure spools of the two-spool turboshaft engine so as to provide for operating the low pressure compressor attached to the low pressure spool with sufficient surge margin.

Claims

1. A method of controlling a two-spool turboshaft engine, comprising controlling a controllable load operatively coupled to a low-pressure compressor of the two-spool turboshaft engine so as to provide for maintaining a predefined relationship between a rotational speed of said low-pressure compressor of said two-spool turboshaft engine and a rotational speed of a high-pressure compressor of said two-spool turboshaft engine such that the rotational speeds of the low pressure-compressor and the high-pressure compressor are mutually dependent, wherein the operation of controlling said controllable load is responsive to at least one of a rotational speed signal of said low-pressure compressor or a rotational speed signal of said high-pressure compressor, said low-pressure compressor of said two-spool turboshaft engine is operatively coupled by a corresponding low-pressure spool to a low-pressure turbine of said two-spool turboshaft engine, and said high-pressure compressor of said two-spool turboshaft engine is operatively coupled by a corresponding high-pressure spool to a high-pressure turbine of said two-spool turboshaft engine.

2. A method of controlling a two-spool turboshaft engine as recited in claim 1, wherein the operation of maintaining said relationship between said rotational speed of said low-pressure compressor and said rotational speed of said high-pressure compressor comprises maintaining a relationship between a corrected rotational speed of said low-pressure compressor and a corrected rotational speed of said high-pressure compressor.

3. A method of controlling a two-spool turboshaft engine as recited in claim 2, wherein said corrected rotational speed of said low-pressure compressor is responsive to N₁/√

{square root over (θ

)}, wherein N₁ is said rotational speed of said low-pressure compressor and θ

is responsive to a ratio of a measured temperature at an inlet to said low-pressure compressor divided by a standard temperature, and said corrected rotational speed of said high-pressure compressor is responsive to N₂/√

{square root over (θ

)}, wherein N₂ is said rotational speed of said high-pressure compressor.

4. A method of controlling a two-spool turboshaft engine as recited in claim 1, wherein the operation of controlling said controllable load is further responsive to an inlet temperature of said low-pressure compressor and an inlet pressure of said low-pressure compressor.

5. A method of controlling a two-spool turboshaft engine as recited in claim 1, wherein the operation of controlling said controllable load is further responsive to a value of Reynolds Number Index at an inlet of said low-pressure compressor, said Reynolds Number Index is given by

6. A method of controlling a two-spool turboshaft engine as recited in claim 1, wherein said controllable load comprises a controllable-pitch propeller or a controllable-pitch fan.

7. A method of controlling a two-spool turboshaft engine as recited in claim 6, wherein said controllable load comprises a variable-pitch propeller operatively coupled to said low-pressure spool through a gear system.

8. A method of controlling a two-spool turboshaft engine as recited in claim 1, wherein the operation of controlling said controllable load comprises:

a. receiving a first measurement responsive to said rotational speed of said low-pressure compressor, wherein said rotational speed signal of said low-pressure compressor is responsive to said first measurement;

b. receiving a second measurement responsive to an inlet temperature of said low-pressure compressor;

c. receiving a third measurement responsive to an inlet pressure of said low-pressure compressor;

d. responsive to said first, second and third measurements, determining a target rotational speed measure representative of a target rotational speed of said high-pressure compressor;

e. receiving a fourth measurement responsive to said rotational speed of said high-pressure compressor, wherein said rotational speed signal of said high-pressure compressor is responsive to said fourth measurement; and

f. controlling said controllable load responsive to both said target rotational speed measure and to said fourth measurement, or to one or more measures responsive thereto, so as to either increase, decrease, or maintain a load level of said controllable load so as to urge said rotational speed of said high-pressure compressor towards said target rotational speed measure.

9. A method of controlling a two-spool turboshaft engine as recited in claim 8, wherein the operation of determining said target rotational speed measure comprises:

a. determining a nominal corrected rotational speed target for said high-pressure compressor responsive to said first and second measurements;

b. determining a speed correction factor responsive to said second and third measurements; and

c. determining said target rotational speed measure of said high-pressure compressor responsive to said nominal corrected rotational speed target, said speed correction factor, and said second measurement.

10. A method of controlling a two-spool turboshaft engine as recited in claim 9, wherein the operation of determining said target rotational speed measure of said high-pressure compressor comprises:

a. determining a target corrected rotational speed of said high-pressure compressor responsive to a product of said nominal corrected rotational speed target and said speed correction factor; and

b. determining said target rotational speed measure responsive to said target corrected rotational speed of said high-pressure compressor multipled by √

{square root over (θ

)}, wherein θ

is responsive to said second measurement, or to a measure responsive thereto, divided by a standard temperature.

11. A method of controlling a two-spool turboshaft engine as recited in claim 9, wherein the operation of determining said speed correction factor comprises:

a. determining a value of a Reynolds Number Index responsive to said second and third measurements; and

b. determining said speed correction factor by evaluating a speed correction factor function with respect to Reynolds Number Index at said value of said Reynolds Number Index, wherein said speed correction factor function is derived from data for said two-spool turboshaft engine at a nominal rotational speed of said low-pressure compressor.

12. A method of controlling a two-spool turboshaft engine as recited in claim 11, wherein said value of said Reynolds Number Index is given by

13. A method of controlling a two-spool turboshaft engine as recited in claim 9, wherein the operation of determining said nominal corrected rotational speed target comprises:

a. determining a corrected rotational speed of said low-pressure compressor responsive to said first and second measurements;

b. determining said nominal corrected rotational speed target by evaluating a nominal corrected rotational speed target function as a function of corrected rotational speed of said low-pressure compressor at said corrected rotational speed of said low-pressure compressor, wherein said nominal corrected rotational speed target function is derived from data for said two-spool turboshaft engine at a nominal condition of said inlet temperature and said inlet pressure of said low-pressure compressor.

14. A method of controlling a two-spool turboshaft engine as recited in claim 1, wherein the operation of controlling said controllable load comprises:

a. receiving a first measurement responsive to said rotational speed of said high-pressure compressor, wherein said rotational speed signal of said high-pressure compressor is responsive to said first measurement;

b. receiving a second measurement responsive to an inlet temperature of said low-pressure compressor;

c. receiving a third measurement responsive to an inlet pressure of said low-pressure compressor;

d. responsive to said first, second and third measurements, determining a target rotational speed measure representative of a target rotational speed of said low-pressure compressor;

e. receiving a fourth measurement responsive to said rotational speed of said low-pressure compressor, wherein said rotational speed signal of said low-pressure compressor is responsive to said fourth measurement; and

f. controlling said controllable load responsive to both said target rotational speed measure and to said fourth measurement, or to one or more measures responsive thereto, so as to either increase, decrease, or maintain a load level of said controllable load so as to urge said rotational speed of said low-pressure compressor towards said target rotational speed measure.

15. A method of controlling a two-spool turboshaft engine as recited in claim 14, wherein the operation of determining said target rotational speed measure comprises:

a. determining a nominal corrected rotational speed target for said low-pressure compressor responsive to said first and second measurements;

b. determining a speed correction factor responsive to said second and third measurements; and

c. determining said target rotational speed measure of said low-pressure compressor responsive to said nominal corrected rotational speed target, said speed correction factor, and said second measurement.

16. A method of controlling a two-spool turboshaft engine as recited in claim 15, wherein the operation of determining said target rotational speed measure of said low-pressure compressor comprises:

a. determining a target corrected rotational speed of said low-pressure compressor responsive to a product of said nominal corrected rotational speed target and said speed correction factor; and

b. determining said target rotational speed measure responsive to said target corrected rotational speed of said high-pressure compressor multiplied by √

{square root over (θ

)}, wherein θ

is responsive to said second measurement, or to a measure responsive thereto, divided by a standard temperature.

17. A method of controlling a two-spool turboshaft engine as recited in claim 15, wherein the operation of determining said speed correction factor comprises:

a. determining a value of a Reynolds Number Index responsive to said second and third measurements; and

b. determining said speed correction factor by evaluating a speed correction factor function with respect to Reynolds Number Index at said value of said Reynolds Number Index, wherein said speed correction factor function is derived from data for said two-spool turboshaft engine at a nominal rotational speed of said high-pressure compressor.

18. A method of controlling a two-spool turboshaft engine as recited in claim 17, wherein said value of said Reynolds Number Index is given by

19. A method of controlling a two-spool turboshaft engine as recited in claim 15, wherein the operation of determining said nominal corrected rotational speed target comprises:

a. determining a corrected rotational speed of said high-pressure compressor responsive to said first and second measurements; and

b. determining said nominal corrected rotational speed target by evaluating a nominal corrected rotational speed target function as a function of corrected rotational speed of said high-pressure compressor at said corrected rotational speed of said high-pressure compressor, wherein said nominal corrected rotational speed target function is derived from data for said two-spool turboshaft engine at a nominal condition of said inlet temperature and said inlet pressure of said high-pressure compressor.

20. A two-spool turboshaft engine control system, comprising:

a. a first rotational speed sensor input, wherein said first rotational speed sensor input provides for receiving a first speed signal indicative of a measure of rotational speed of a low-pressure compressor of a two-spool turboshaft engine;

b. a second rotational speed sensor input, wherein said second rotational speed sensor input provides for receiving a second speed signal indicative of a measure of rotational speed of a high-pressure compressor of said two-spool turboshaft engine;

c. a temperature sensor input, wherein said temperature sensor input provides for receiving a temperature signal indicative of a measure of inlet temperature of said low-pressure compressor of said two-spool turboshaft engine;

d. a pressure sensor input, wherein said pressure sensor input provides for receiving a pressure signal indicative of a measure of inlet pressure of said low-pressure compressor of said two-spool turboshaft engine;

e. a load control output, wherein said load control output provides for outputting a load control signal to a controllable load operatively coupled to a low-pressure spool of said two-spool turboshaft engine that drives said low-pressure compressor;

f. a controller, wherein said controller provides for controlling said controllable load so as to control an amount of torque applied thereby to said low-pressure spool of said two-spool turboshaft engine, and

g. the operation of controlling said controllable load provides for regulating one of a corrected rotational speed of said low-pressure compressor or a corrected rotational speed of said high-pressure compressor of said two-spool turboshaft engine, responsive to the other of said corrected rotational speed of said high-pressure compressor or said corrected rotational speed of said low-pressure compressor, and further responsive to said temperature signal and to said pressure signal.

21. A two-spool turboshaft engine control system as recited in claim 20, wherein said two-spool turboshaft engine is incorporated in a two-spool turboprop engine of an associated aircraft propulsion system, said controllable load comprises a variable-pitch propeller assembly operatively coupled to said low-pressure spool through a gear system, and the operation of controlling said controllable load comprises controlling a pitch of said variable-pitch propeller assembly so as to provide for regulating one of said corrected rotational speed of said low-pressure compressor or said corrected rotational speed of said high-pressure compressor, responsive to the other of said corrected rotational speed of said high-pressure compressor or said corrected rotational speed of said low-pressure compressor.

22. A method of providing for controlling a two-spool turboshaft engine, comprising:

for at least a nominal combination of inlet air temperature and inlet air pressure conditions;

a. simulating the two-spool turboshaft engine at an associated power or air flow condition level of said two-spool turboshaft engine of a plurality of power or air flow condition levels;

b. at each power or air flow condition level;

i. finding a simulated torque acting on a low-pressure spool of said two-spool turboshaft engine so that a resulting simulated surge margin of a low-pressure compressor of said two-spool turboshaft engine meets or exceeds a threshold, wherein said low-pressure compressor is operatively coupled to said low-pressure spool; and

ii. storing resulting corrected speeds of said low-pressure compressor and a high-pressure compressor of said two-spool turboshaft engine at said simulated torque for said power or air flow condition level;

c. repeating steps b for a range of power or air flow condition levels associated with an operating range of said two-spool turboshaft engine;

d. determining a relationship between said corrected speeds of said low-pressure compressor and said high-pressure compressor over said range of power or air flow condition levels using data stored in step b.ii; and

e. for at least one corrected speed of either said low-pressure compressor or said high-pressure compressor;

i. for each combination of said inlet air temperature and said inlet air pressure conditions, of a plurality of combinations of said inlet air temperature and said inlet air pressure conditions;

a). finding said simulated torque acting on said low-pressure spool of said two-spool turboshaft engine so that a resulting said simulated surge margin of said low-pressure compressor of said two-spool turboshaft engine meets or exceeds said threshold; and

b). storing said corrected speeds of said low-pressure compressor and said high-pressure compressor at said simulated torque for said combination of said inlet air temperature and said inlet air pressure conditions;

ii. determining a modification of said relationship between said corrected speeds of said low-pressure compressor and said high-pressure compressor over said range of power or air flow condition levels responsive to said combination of said inlet air temperature and said inlet air pressure conditions, from said corrected speeds of said low-pressure compressor and said high-pressure compressor at said simulated torque for said plurality of combinations of said inlet air temperature and said inlet air pressure conditions of steps e.i; and

iii. storing said relationship and said modification of said relationship on a non-transitory computer readable medium for use by a control system for controlling said two-spool turboshaft engine.

23. A two-spool turboshaft aircraft engine, comprising:

a. an inlet;

b. at least one low-pressure compressor;

c. at least one high-pressure compressor;

d. at least one combustion chamber;

e. at least one high-pressure turbine;

f. at least one low-pressure turbine;

g. a controllable load operatively coupled to at least one of said at least one low-pressure compressor, said at least one low-pressure turbine, or an associated low-pressure spool associated with said at least one low-pressure compressor and said at least one low-pressure turbine; and

h. a speed control system that provides for controlling said controllable load so as to provide for regulating one of a rotational speed of said at least one low-pressure compressor or a rotational speed of said at least one high-pressure compressor, responsive to the other of said rotational speed of said at least one high-pressure compressor or said rotational speed of said at least one low-pressure compressor, wherein each of said at least one low-pressure compressor, said at least one high-pressure compressor, said at least one high-pressure turbine and said at least one low-pressure turbine are configured to rotate about a common longitudinal axis of the two-spool turboshaft aircraft engine, said at least one low-pressure compressor provides for compressing air received from said inlet and provides for outputting said air to said at least one high-pressure compressor, said at least one high-pressure compressor provides for compressing said air received from said at least one low-pressure compressor and outputting said air to said at least one combustion chamber, said at least one combustion chamber provides for combusting a mixture of fuel and said air so as to generate resulting exhaust gases, said at least one high-pressure turbine provides for generating a torque on a high-pressure spool operatively coupled to said at least one high-pressure compressor so as to cause said at least one high-pressure compressor to rotate about said longitudinal axis of said two-spool turboshaft aircraft engine, said at least one low-pressure turbine provides for generating a torque on said low-pressure spool operatively coupled to said at least one low-pressure compressor so as to cause said at least one low-pressure compressor to rotate about said longitudinal axis of said two-spool turboshaft aircraft engine, and when installed in an aircraft, said at least one low-pressure compressor is forward of said at least one high-pressure compressor, said at least one high-pressure compressor is forward of said at least one high-pressure turbine, and said at least one high-pressure turbine is forward of said at least one low-pressure turbine.

24. A two-spool turboshaft aircraft engine as recited in claim 23, wherein said inlet is located forward of said at least one low-pressure compressor.

25. A two-spool turboshaft aircraft engine as recited in claim 23, wherein said at least one low-pressure compressor and said at least one low-pressure turbine are connected to or a part of said low-pressure spool so that said at least one low-pressure compressor, said at least one low-pressure turbine, and said low-pressure spool all rotate in unison.

26. A two-spool turboshaft aircraft engine as recited in claim 23, wherein said controllable load comprises a variable-pitch propeller.

27. A two-spool turboshaft aircraft engine as recited in claim 26, wherein said variable-pitch propeller is located forward of said at least one low-pressure compressor.

28. A two-spool turboshaft aircraft engine as recited in claim 26, wherein said variable-pitch propeller is located aft of said at least one low-pressure turbine.

29. A two-spool turboshaft aircraft engine as recited in claim 23, wherein said controllable load comprises a variable-pitch fan.

30. A two-spool turboshaft aircraft engine as recited in claim 23, wherein said controllable load comprises either a variable-pitch propeller or a variable-pitch fan operatively coupled through a gear system to said at least one of said at least one low-pressure compressor, said at least one low-pressure turbine, or said associated low-pressure spool associated with said at least one low-pressure compressor and said at least one low-pressure turbine.