Compressor and controller with altitude compensation

Abstract

A fluid compression system includes a gaseous fluid compressor having a fluid inlet and a compressed fluid discharge, a prime mover coupled to the gaseous fluid compressor in driving relation, and a demand sensor positioned to measure a compressor demand and output a demand signal. An engine control unit is coupled to the prime mover and is operable to measure prime mover speed and prime mover power output. The engine control unit sets a variable maximum rated speed that maintains the engine power below a predetermined limit. A compressor controller unit is arranged to receive the demand signal and vary an operating speed based in part upon the demand signal. The operating speed is limited to the maximum rated speed set by the engine control unit.

What is claimed is: 
     
         1 . A fluid compression system comprising:
 a gaseous fluid compressor having a fluid inlet and a compressed fluid discharge;   a prime mover coupled to the gaseous fluid compressor in driving relation;   a demand sensor positioned to measure a compressor demand and output a demand signal;   an engine control unit coupled to the prime mover and operable to measure prime mover speed and prime mover power output, the engine control unit setting a variable maximum rated speed that maintains the engine power below a predetermined limit;   a compressor controller unit arranged to receive the demand signal and vary an operating speed based in part upon the demand signal, the operating speed being limited to the maximum rated speed set by the engine control unit.   
     
     
         2 . The fluid compression system of  claim 1 , wherein the prime mover is an internal combustion engine. 
     
     
         3 . The fluid compression system of  claim 1 , wherein the prime mover is a diesel engine. 
     
     
         4 . The fluid compression system of  claim 1 , wherein the gaseous fluid compressor is a positive-displacement compressor. 
     
     
         5 . The fluid compression system of  claim 1 , wherein the gaseous fluid compressor is a rotary screw compressor. 
     
     
         6 . The fluid compression system of  claim 1 , further comprising a receiver tank coupled to the compressed fluid discharge, and wherein the demand sensor includes a receiver tank pressure sensor that senses a pressure within the receiver tank. 
     
     
         7 . The fluid compression system of  claim 1 , wherein the engine control unit and the compressor control unit are combined into a single system control unit. 
     
     
         8 . An air compression system comprising:
 an air compressor including an ambient air inlet and a compressed air discharge;   an engine coupled to the air compressor and operable to drive the air compressor to produce a flow of compressed air;   a receiver tank coupled to the compressed air discharge to receive the flow of compressed air and to maintain a volume of pressurized air;   a demand sensor positioned to measure a pressure of the receiver tank and operable to generate a first signal related to the pressure of the receiver tank;   an engine control unit coupled to the engine to operate the engine at a desired operating speed in response to a control signal and operable to measure engine speed and engine power to calculate a maximum engine speed at which the engine power is at a preset maximum value;   a compressor control unit operable to generate the control signal to vary the desired operating speed in response to the first signal, the desired operating speed being limited to the maximum engine speed calculated by the engine control unit.   
     
     
         9 . The air compression system of  claim 8 , wherein the engine is a diesel engine. 
     
     
         10 . The air compression system of  claim 8 , wherein the compressor is a positive-displacement air compressor. 
     
     
         11 . The air compression system of  claim 8 , wherein the compressor is a screw compressor. 
     
     
         12 . The air compression system of  claim 8 , wherein the engine control unit and the compressor control unit are combined into a single system control unit. 
     
     
         13 . A method of controlling a gas compressor system, the method comprising:
 setting a maximum engine speed at a factory preset maximum engine speed, the factory preset maximum engine speed corresponding to a maximum desired engine power output at a first atmospheric pressure;   coupling the engine to a compressor such that the engine operates at an operating speed to drive the compressor at a speed that is proportional to the operating speed;   delivering a flow of compressed gas in response to operation of the compressor;   sensing an actual power output of the engine at the operating speed;   changing the maximum engine speed to a new maximum engine speed based on the sensed actual engine power output at the operating speed to maintain the engine output at or below the maximum desired engine output;   sensing a compressed gas demand;   varying the operating speed of the engine in response to the sensed compressed gas demand; and   limiting the operating speed to the new maximum engine speed.   
     
     
         14 . The method of  claim 13 , wherein the actual power output of the engine varies in response to speed and the atmospheric pressure that is different than the first atmospheric pressure.