Compressor surge sensor

Abstract

The disclosure of this invention relates to means for detecting compressor surge by sensing the pressure downstream of the compressor of a turbine type power plant for rapidly opening the compressor bleeds and holding the bleeds open for brief interval after surge disappears. The sensed pressure is admitted to one side of the diaphragm through a laminar flow restrictor for obtaining a lag time constant which increases as pressure decreases.

I claim: 
     
       1. A surge control system for opening a bleed valve of the compressor section of a turbine type power plant so as to prevent or eliminate surge therein comprising means for sensing the pressure at the compressor for producing a signal whenever a predetermined transitory drop in said pressure occurs, an actuator connected to said bleed valve for opening and closing said bleed valve, control means including a servo valve and servo fluid responsive to said signal for controlling said actuator to position it to an open position, a relatively unrestricted flow line for leading said servo fluid .[.to.]. .Iadd.from .Iaddend.said servo valve to position it from a normally closed bleed valve condition to an opened bleed valve condition, said servo valve movable to overtravel null condition when said servo valve is in the opened bleed valve condition, a restricted flow line for conducting said servo fluid .[.from.]. .Iadd.to .Iaddend.said servo valve to position it to its normally closed bleed valve condition, said restricted flow line and overtravel being dimensioned so as to permit said bleed valves to remain open over a predetermined amount of time subsequent to said transition drop in pressure returns to substantially its original value, and said unrestricted flow line being sized to position said servo valve in the opened bleed valve condition at a relatively rapid rate. 
     
     
       2. A surge control system as claimed in claim 1 wherein said sensing means includes a fluid reaction means having opposing surfaces subjected to the pressure in the compressor, and a laminar flow restriction disposed between one of said reaction surfaces and the compressor. 
     
     
       3. A surge control system as claimed in claim 2 wherein said reaction means is a diaphragm. 
     
     
       4. A surge control system as claimed in claim 3 including a check valve disposed in said unrestricted flow line to prevent servo fluid flowing out of said servo valve to pass therethrough. 
     
     
       5. A surge control system as claimed in claim 4 including a flapper valve controlled by said diaphragm for porting and bleeding fluid to and from said servo valve. 
     
     
       6. A surge control system as claimed in claim 1 wherein said pressure is the pressure at the discharge end of the compressor. 
     
     
       7. A surge controller for an engine comprising in combination, means for sensing surge condition in said engine by detecting the rate at which the pressure where surge is occurring drops for producing a signal, means for subsiding the surge condition by adjusting the airflow through said engine, an actuator connected to said means, metering means having a null position for controlling said actuator by the application of fluid pressure, a controller responsive to said signal having a restricted and unrestricted flow line porting and bleeding fluid to and from a reaction surface for positioning said metering means from its null position, said unrestricted flow line being sized to port fluid at a rate to rapidly position said actuator to rapidly effect the flow in said engine and position said metering means to overtravel the null position, and said restricted flow line shunting said unrestricted flow line to reduce the rate in which said metering means returns to its null position, the extent of overtravel and the dimension of said restricted flow line being selected to assure that surge subsides prior to reaching said null position. 
     
     
       8. A surge controller as claimed in claim 7 wherein said sensing means includes a diaphragm having one face exposed to unrestricted communication to the engine and the opposing face exposed to restricted communication to said engine. 
     
     
       9. A surge controller as claimed in claim 8 wherein said restricted communication includes a laminar flow restrictor.