STALL WARNING SYSTEM FOR A GAS TURBINE ENGINE

• US 3,867,717 A
• Filed: 04/25/1973
• Issued: 02/18/1975
• Est. Priority Date: 04/25/1973
• Status: Expired due to Term

• Current Assignee: John Theodore Moehring, Virgil Willis Lawson
• Original Assignee: John Theodore Moehring, Virgil Willis Lawson
• Inventors: Moehring, John Theodore, Lawson, Virgil Willis
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Myers, Randall P.
• Application Number:
  US05/354,303
• Time in Patent Office: 664 Days
• Field of Search: 340/27R,27SS,27NA 73/116,117.3 60/39.28R,39.29R 235/150.2,150.21
• US Class Current: 340/626
• CPC Class Codes: F04D 27/001 Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring

Abstract

A stall warning system for a gas turbine engine precludes the possibility of an erroneous indication of compressor stall by simultaneously monitoring the air pressure at the discharge end of the engine compressor together with the temperature of the turbine section of the engine. Initiation of the stall warning signal is made contingent upon the simultaneous receipt of signals indicative of both an abnormally low compressor discharge pressure and an abnormally high turbine temperature. In this manner an erroneous indication of compressor stall, as may occur during normal operation of the engine when the compressor discharge pressure is low, may be positively precluded.

Claims

1. A stall warning system for a gas turbine engine of the type having a compressor, combustor, turbine and exhaust duct in serial flow relation comprises:

means for detecting pressure in at least one location along the compressor inlet and outlet flowpaths thus providing a signal indicative of the detected pressure;

first comparator means for receiving the detected compressor pressure signal and comparing the detected signal with a reference signal to provide an output signal representative of an abnormal decrease in compressor pressure;

means for detecting a temperature representative of turbine temperature thus providing a signal indicative of the detected temperature;

second comparator means for receiving the detected temperature signal and comparing the detected signal with a reference signal to provide an output signal representative of an abnormal increase in turbine temperature; and

gate means for providing an output signal indicative of engine stall upon receipt of both a signal from the first comparator means representative of an abnormal decrease in compressor pressure and a signal from the second comparator means representative of an abnormal increase in detected temperature thereby precluding the possibility of a false stall signal occurring during normal operation of the engine.

2. The stall warning system of claim 1 wherein:

the means for detecting compressor pressure includes a first conduit terminating in a pressure pickup inlet stationed within the compressor annular inlet and a second conduit terminating in a pressure pickup inlet suitably disposed at the discharge side of the compressor; and

the first comparator means includes a computer means for receiving the compressor inlet and discharge pressure from the detecting means and calculating the ratio of compressor discharge pressure to compressor inlet pressure Providing an output signal indicative of the compressor pressure ratio;

a reference generator for providing an output signal indicative of the minimum compressor pressure ratio during normal compressor operation, and a first summing means for combining the reference generator pressure ratio signal with the computed pressure ratio signal to provide an output signal, the polarity of which is indicative of an actual compressor pressure ratio which has fallen below the minimum compressor ratio for normal operation.

3. The stall warning system of claim 2 wherein:

the second comparator means includes a reference generator for providing an output signal indicative of the maximum turbine temperature during normal engine operation, and a second summing means for combining the reference generator temperature signal with the detected temperature to provide an output signal, the polarity of which is indicative of an actual turbine temperature which has risen above the maximum turbine temperature for normal engine operation.

4. The stall warning system of claim 3 wherein:

the gate means includes a latching circuit which receives the signal from the first summing means and latches an output control voltage when the signal from the first summing means is of the polarity indicative of an actual pressure ratio which has fallen below the minimum pressure ratio during normal compressor operation, and a switch which transmits a signal indicative of compressor stall upon both latching of the output control voltage by the latching circuit and upon receipt from the second summing means of a signal having a polarity indicative of a turbine temperature which has risen above the maximum turbine temperature for normal engine operation.

5. The stall warning system of claim 4 including a feedback conduit which operates to unlatch the output control voltage from the switch and thereby open the switch when the actual turbine temperature decreases below the maximum turbine temperature for normal engine operation.

6. The stall warning system of claim 3 wherein there is further provided a latching circuit for receipt of the stall warning signal from the gate means in order to maintain the stall warning signal for a time period after either the turbine temperature decreases below the reference temperature, or the pressure ratio increases above the reference ratio.

7. The stall warning system of claim 6 wherein there is further provided a system selector means whereby the stall signal may be selectively applied to provide a visual warning or initiate compressor stall correcting action.

8. The stall warning system of claim 2 wherein:

the second comparator means includes a differentiator for receiving the turbine temperature from the detecting means for differentiation thereof, so as to provide an output signal representative of the rate of change of turbine temperature, a reference generator for providing an output signal indicative of the maximum rate of change for turbine temperature during normal engine operation, and a second summing means for combining the reference generator temperature rate signal with the computed temperature rate signal to provide an output signal, the polarity of which is indicative of an actual rate of increase in turbine temperature which exceeds the maximum rate of change for turbine temperature during normal engine operation.

9. The stall warning system of claim 8 wherein:

the gate means includes;

a first latching circuit which receives the signal from the first summing means and latches an output control voltage when the signal from the first summing means is of the polarity indicative of an actual pressure ratio which decreases below the minimum pressure ratio during normal compressor operation, a switch which transmits a signal indicative of compressor stall upon both latching of the output control voltage by the latching circuit and upon receipt from the second summing means of a signal having a polarity indicative of a rate of turbine temperaTure increase which has risen above the maximum rate of turbine temperature increase for normal engine operation, and a second latching circuit which maintains the stall signal until the actual turbine temperature decreases below an established safe limit.

10. The stall warning system of claim 9 including a feedback conduit which operates to unlatch the second latching circuit when the actual turbine temperature decreases below the maximum turbine temperature for normal engine operation.

11. The stall warning system of claim 8 wherein there is further provided a latching circuit for receipt of the stall warning signal from the gate means in order to maintain the stall warning signal for a time period after either the rate of turbine temperature increase decreases below the reference rate or the pressure ratio increases above the reference ratio.

12. The stall warning system of claim 11 wherein there is further provided a system selector means whereby the stall signal may be selectively applied to provide a visual warning or initiate compressor stall correcting action.

13. The stall warning system of claim 1 wherein:

the means for detecting compressor pressure includes a conduit terminating in a pressure pickup inlet suitably disposed at the discharge side of the compressor; and

the first comparator means includes a differentiator for receiving the compressor discharge pressure from the detecting means for differentiation thereof, so as to provide an output signal representative of the rate of change of compressor discharge pressure, a reference generator for providing an output signal indicative of the maximum rate of change for compressor discharge pressure during normal compressor operation, and a first summing means for combining the reference generator pressure rate signal with the computed pressure rate signal to provide an output signal, the polarity of which is indicative of an actual rate of decrease in compressor discharge pressure which exceeds the maximum rate of change for compressor discharge pressure during normal compressor operation.

14. The stall warning system of claim 13 wherein:

the second comparator means includes a reference generator for providing an output signal indicative of the maximum turbine temperature during normal engine operation, and a second summing means for combining the reference generator temperature signal with the detected temperature to provide an output signal, the polarity of which is indicative of an actual turbine temperature which has risen above the maximum turbine temperature for normal engine operation.

15. The stall warning system of claim 14 wherein:

the gate means includes a latching circuit means which receives the signal from the first summing means and latches an output control voltage when the signal from the first summing means is of the polarity indicative of an actual rate of decrease of compressor discharge pressure which exceeds the maximum rate of decrease of compressor discharge pressure during normal compressor operation, and a switch which transmits a signal indicative of compressor stall upon both latching of the output control voltage by the latching circuit and upon receipt from the second summing means of a signal having a polarity indicative of a turbine temperature which has risen above the maximum turbine temperature for normal engine operation.

16. The stall warning system of claim 15 including a feedback conduit which operates to unlatch the output control voltage from the switch and thereby open the switch when the actual turbine temperature decreases below the maximum turbine temperature for normal engine operation.

17. The stall warning system of claim 14 wherein there is further provided a timed hold means which receives the signal from the first summing means and maintains presence of the signal at the gate means and a latching circuit for receipt of the stall warning signal from the gate means in order to maintain the stall warning signal for a time peRiod after either the rate of pressure decrease decays below the reference rate or the turbine temperature decreases below the reference temperature.

18. The stall warning system of claim 17 wherein there is further provided a system selector means whereby the stall signal may be selectively applied to provide a visual warning or initiate compressor stall correcting action.

19. The stall warning system of claim 13 wherein:

the second comparator means includes a differentiator for receiving the turbine temperature from the detecting means for differentiation thereof, so as to provide an output signal representative of the rate of change of turbine temperature, a reference generator for providing an output signal indicative of the maximum rate of change for turbine temperature during normal engine operation, and a second summing means for combining the reference generator temperature rate signal with the computed temperature rate signal to provide an output signal, the polarity of which is indicative of an actual rate of increase in turbine temperature which exceeds the maximum rate of change for turbine temperature during normal engine operation.

20. The stall warning system of claim 19 wherein the gate means includes a first latching circuit which receives the signal from the first summing means and lataches an output control voltage when the signal from the first summing means is of the polarity indicative of an actual rate of decrease of compressor discharge pressure which exceeds the maximum rate of decrease of compressor discharge pressuring during normal compressor operation, and a switch which transmits a signal indicative of compressor stall upon both latching of the output control voltage by the latching circuit and upon receipt from the second summing means of a signal having a polarity indicative of an actual rate of turbine temperature change which exceeds the maximum rate of temperature change for normal operation and a second latching circuit which maintains the stall signal until the actual turbine temperature decreases below an established safe limit.

21. The stall warning system of claim 20 including a feedback conduit which operates to unlatch the second latching circuit when the actual turbine temperature decreases below the maximum turbine temperature for normal operation.

22. The stall warning system of claim 19 wherein there is further provided a timed hold means which receives the signal from the first summing means and maintains presence of the signal at the gate means and a latching circuit for receipt of the stall warning signal from the gate means in order to maintain the stall warning signal for a time period after either the rate of pressure decrease decays below reference rate of pressure change or the rate of turbine increase decreases below the reference rate of turbine change.

23. The stall warning system of claim 22 wherein there is further provided a system selector whereby the stall signal may be selectively applied to provide a visual warning or initiate compressor stall correcting action.