STALL PROTECTOR SYSTEM FOR A GAS TURBINE ENGINE

• US 3,852,958 A
• Filed: 09/28/1973
• Issued: 12/10/1974
• Est. Priority Date: 09/28/1973
• Status: Expired due to Term

• Current Assignee: Max Martin Adams, Vernon Robert Duncan
• Original Assignee: Max Martin Adams, Vernon Robert Duncan
• Inventors: Adams, Max Martin, Duncan, Vernon Robert
• Primary Examiner(s): Croyle, Carlton R.
• Assistant Examiner(s): Garrett, Robert E.
• Application Number:
  US05/401,650
• Time in Patent Office: 438 Days
• Field of Search: 60/39.28R,39.28T,39.29 340/27SS 73/116
• US Class Current: 60/39.281
• CPC Class Codes: F02C 9/32 characterised by throttling of fuel F02C9/38 takes precedence
• CPC Class Codes: F04D 27/0207 by bleeding, bypassing or recycling fluids influencing the boundary layer by an uncontrolled bleeding of the working fluid F04D29/681

Abstract

A stall protector system is provided for a gas turbine engine wherein the compressor pressure is measured, differentiated, and compared with a reference indicative of the maximum rate at which the compressor pressure decreases during normal operation. When the actual rate of decrease of compressor pressure exceeds the reference rate, then the signal is integrated and compared with a second reference indicative of the minimum change in compressor pressure before a stall occurs. If the second reference is exceeded, the fuel flow to the combustor is automatically restricted.

Claims

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

means for measuring compressor pressure and providing an electrical output signal corresponding to the actual compressor pressure measured;

a differentiator for differentiating the output signal from the measuring means and providing an output signal indicative of the rate of change of compressor pressure;

a slope detector for comparing the rate of change of compressor pressure with a reference rate signal indicative of the maximum rate at which the compressor pressure may be expected to decrease during normal operation;

an integrator for providing a time integration of the compressor pressure rate when the actual rate of decrease of compressor pressure exceeds the reference rate;

a pressure detector for comparing the actual change in compressor pressure from the integrator with a second reference signal corresponding to the minimum change in compressor pressure indicative of a compressor stall; and

means for regulating the flow of fuel to the combustor when the actual change in compressor pressure exceeds the second reference signal.

2. The stall protector system of claim 1 wherein the means for regulating the flow of fuel to the combustor includes:

a silicon controlled rectifier connected to fire upon receipt of a signal from the pressure detector indicative of an actual change in compressor pressure which exceeds the second reference signal;

a relay in series connection with the silicon controlled rectifier so as to be energized upon firing of the silicon controlled rectifier wherein the relay includes at least one contact which opens upon energization of the relay; and

a solenoid controlled valve for interrupting the flow of fuel to the combustor upon opening of the relay contacts.

3. The stall protector of claim 2 wheRein:

there is further included a diode, a zener diode, and a resistor in series connection between the pressure detector and the gate of the silicon controlled rectifier, together with a second resistor interconnecting the gate and cathode of the silicon controlled rectifier, wherein the zener diode has a sufficient voltage differential to allow the flow of current through the second resistor only when the output signal from the pressure detector goes substantially above zero volts.

4. The stall protector of claim 1 wherein:

the slope detector includes an operational amplifier, one input of which is serially connected to receive the output from the differentiator through a series resistor with the other input connected to receive the first reference rate signal through a second series resistor from a reference network of resistors connected between a voltage supply wherein the output of the operational amplifier is directed through a third series resistor and a series diode with the anode side of the diode connecting back to the input of the slope detector through a parallel resistor, and the integrator includes a second operational amplifier in parallel connection with a feedback diode and a feedback capacitor such that if the rate of decrease of the compressor pressure is less than the reference rate signal, the output signal from the slope detector will assume a negative polarity and the output signal from the integrator will remain latched at a predetermined voltage through the first diode and feedback diode, while if the rate of decrease of compressor pressure exceeds the reference rate signal then the output signal from the slope detector will switch to a positive polarity causing the second operational amplifier to integrate in a given direction wherein the actual rate of integration is determined by the feedback capacitor and parallel resistor together with the magnitude of the output signal from the differentiator.

5. The stall protection system of claim 4 including:

an amplifier and inverter circuit in series connection between the differentiator and slope detector wherein the amplifier and inverter circuit include a third operational amplifier together with a feedback resistor and a second feedback capacitor connected in parallel arrangement, with one input to the third operational amplifier connected to zero volts through a fourth series resistor; and

an amplifier in series connection between the pressure measuring means and differentiator wherein the second amplifier includes a fourth operational amplifier, together with a second feedback resistor; and

a fifth series resistor in serial connection between the amplifier and differentiator.

6. The stall protector of claim 5 wherein:

the differentiator includes a capacitor, and the first feedback resistor and second feedback capacitor operate in conjunction with the fifth series resistor and differentiator capacitor to provide a double lag break filter at approximately 190 radians.

7. The stall protector of claim 1 wherein the pressure detector includes:

an operational amplifier, one input of which is connected to receive the output from the integrator through a series resistor together with the second reference signal through a second series resistor from a reference network of resistors connected between a voltage supply wherein the output from the pressure detector is directed to the gate of a silicon controlled rectifier within the fuel flow regulating means.

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

a pressure transducer for measuring compressor discharge pressure and providing an electrical output signal correlating to the actual compressor discharge pressure measured;

a differentiator including a capacitor for differentiating the output signal from the pressure transducer and providing an output signal indicative of the rate of change Of compressor pressure;

a slope detector having an operational amplifier, one input of which receives the output from the differentiator for comparison with a reference rate signal applied to the other input wherein the reference rate signal is indicative of the maximum rate at which the compressor discharge pressure may be expected to decrease during deceleration and the output of the operational amplifier is directed through a series diode, the anode side of which connects back to the input of the slope detector through a parallel resistor;

an integrator having a second operational amplifier in parallel connection with a feedback diode and a feedback capacitor such that if the rate of decrease of compressor discharge pressure is less than the reference rate signal, the output from the slope detector remains at a predetermined polarity latching the output signal of the integrator through the series diode and feedback diode, while if the rate of decrease of compressor discharge pressure exceeds the reference rate signal, then the output signal from the slope detector will switch to an opposite polarity, causing the second operational amplifier to integrate in a given direction;

a pressure detector having a third operational amplifier, one input of which is connected to receive the output from the integrator together with a second reference signal corresponding to the minimum change in compressor discharge pressure indicative of a compressor stall such that when the output from the integrator exceeds the second reference signal, there is a switch in the polarity of the output signal from the pressure detector; and

means for regulating the flow of fuel to the combustor when there is a switch in the polarity of the output signal from the pressure detector due to the output from the integrator exceeding the second reference signal.

9. The stall protector system of claim 8 wherein the means for regulating the flow of fuel to the combustor includes:

a silicon controlled rectifier connected to fire upon an increase in the level of the output signal from the pressure detector; and

a relay in series connection with the silicon controlled rectifier so as to be energized upon firing of the silicon controlled rectifier wherein the relay includes at least one contact which switches upon energization of the relay for controlling a valve which regulates the flow of fuel to the combustor.

10. The stall protector system of claim 9 including:

an amplifier and inverter circuit in series connection between the differentiator and slope detector wherein the amplifier and inverter circuit include a fourth operational amplifier together with a feedback resistor and a second feedback capacitor connected in parallel arrangement, and an amplifier in series connection between the pressure transducer and differentiator wherein the second amplifier includes a fifth operational amplifier together with a third feedback capacitor.