Anticipation logic for a surge control valve utilized with load compressor

Abstract

A load compressor includes an air inlet and an outlet, and a surge control valve positioned on the outlet. The surge control valve serves to selectively pass air to a downstream use, or to be dumped to atmosphere. A control for the compressor and the surge control valve is also included. The control is provided with a variable indicative of the operation of the load compressor, the variable being indicative of a movement to transient operation of the compressor. The control is provided with a low surge control limit for steady state operation. The control is also provided with a higher surge control limit, and switches to use of the higher surge control limit if the variable being monitored is seen to change beyond a particular threshold. The low and higher surge control limits are utilized to control the opening of the surge control valve. An aircraft air supply system and a method are also disclosed.

1 . A compressor system comprising:
 a compressor having an air inlet and an outlet, a surge control valve positioned on said outlet, said surge control valve serving to selectively pass air to a downstream use, or to be dumped; and   a control for said compressor and said surge control valve provided with a variable indicative of movement of said compressor to transient operation, said control further being provided with a low surge control limit, and said control being provided with a higher surge control limit, said control switching to use of said higher surge control limit if the variable being monitored is seen to change beyond a particular threshold, and said low and higher surge control limits being utilized to control the opening of said surge control valve.   
     
     
         2 . The compressor system as set forth in  claim 1 , wherein said compressor is a load compressor in an auxiliary power unit. 
     
     
         3 . The compressor system as set forth in  claim 1 , wherein said variable is a dynamic head pressure of said compressor. 
     
     
         4 . The compressor system as set forth in  claim 3 , wherein said dynamic head pressure is inversely proportional to a discharge pressure of said compressor. 
     
     
         5 . The compressor system as set forth in  claim 1 , wherein said change in said variable must occur in consecutive readings of said variable before said control moves to said higher surge control limit. 
     
     
         6 . The compressor system as set forth in  claim 1 , wherein said control moves back to said low surge control limit once the change in the variable no longer exceeds the threshold. 
     
     
         7 . The compressor system as set forth in  claim 1 , wherein said change in said variable is negative, and must be lower than a predetermined threshold for said control to switch to said higher surge control limit. 
     
     
         8 . The compressor system as set forth in  claim 1 , wherein said surge control valve also incorporates a bleed valve, with said bleed valve controlling the flow to the downstream use. 
     
     
         9 . The compressor system as set forth in  claim 8 , wherein said bleed valve and said surge control valve are incorporated into a single valve. 
     
     
         10 . The compressor system as set forth in  claim 8 , wherein said bleed valve and said surge control valve are two separate valves. 
     
     
         11 . An aircraft air supply system including:
 an auxiliary power unit powering a load compressor, said load compressor delivering air to a use on an aircraft;   said load compressor having an air inlet and an outlet, a surge control valve positioned on said outlet, said surge control valve serving to selectively pass air to the use, or to be dumped; and   a control for said load compressor and said surge control valve provided with a variable indicative of a movement of said compressor to transient operation, said control further being provided with a low surge control limit, and said control being provided with a higher surge control limit, said control switching to use of said higher surge control limit if the variable being monitored is seen to change beyond a particular threshold, and said low and higher surge control limits being utilized to control the opening of said surge control valve.   
     
     
         12 . The aircraft air supply system as set forth in  claim 11 , wherein said variable is a dynamic head pressure of said load compressor. 
     
     
         13 . The aircraft air supply system as set forth in  claim 12 , wherein said dynamic head pressure is inversely proportional to a discharge pressure of said load compressor. 
     
     
         14 . The aircraft air supply system as set forth in  claim 11 , wherein said change in said variable must occur in consecutive readings of said variable before said control moves to said higher surge control limit. 
     
     
         15 . The aircraft air supply system as set forth in  claim 11 , wherein said control moves back to said lower surge control limit once the change in the variable no longer exceeds the threshold. 
     
     
         16 . The aircraft air supply system as set forth in  claim 11 , wherein said change in said variable is negative, and must be lower than a predetermined threshold for said control to switch to said higher surge control limit. 
     
     
         17 . The aircraft air supply system as set forth in  claim 11 , wherein said use on the aircraft includes both a passenger cabin air supply, and the supply of air to a main gas turbine engine on the aircraft. 
     
     
         18 . The aircraft air supply system as set forth in  claim 11 , wherein said surge control valve also incorporates a bleed valve, with said bleed valve controlling the flow to the downstream use. 
     
     
         19 . The aircraft air supply system as set forth in  claim 18 , wherein said bleed valve and said surge control valve are incorporated into a single valve. 
     
     
         20 . The aircraft air supply system as set forth in  claim 18 , wherein said bleed valve and said surge control valve are two separate valves. 
     
     
         21 . A method of operating a load compressor comprising:
 controlling a surge control valve by providing a variable indicative of movement of a compressor to transient operation, said control further being provided with a low surge control limit, and said control being provided with a higher surge control limit, said control switching to use of said higher surge control limit if the variable being monitored is seen to change beyond a particular threshold, and one of said low and higher surge control limits being used to open said surge control valve when said one of the low and higher surge control limit is exceeded.