Gas compressor

Abstract

A reciprocating gas compressor in which a piston ( 3 ) reciprocates within a compression chamber ( 1 ) in order to compress gas. Water is injected through nozzle ( 6, 7 ) into the compression chamber to cool the gas during compression. A source of pressurised liquid ( 13 ) is arranged to accelerate liquid through the nozzle ( 6, 7 ). At least one duct ( 14, 17, 19 ) connects the pressurised source ( 13 ) to the nozzles ( 6, 7 ). The dimensions of the duct ( 14, 17, 19 ) are sized to define the inertia of the liquid to control the acceleration of the mass flow through the nozzles during compression such that the cooling capacity of the liquid in the compression chamber increases as the pressure therein approaches its final value.

1 . A gas compressor comprising a compression chamber to contain gas to be compressed, a compression piston to compress the gas by movement of the compression piston in the compression chamber, valve means for allowing compressed gas to be drawn from the compression chamber, an atomiser for spraying liquid into the compression chamber to absorb heat from the gas during compression, a pressurised source of liquid and a duct arranged to feed liquid from the pressurised source to the atomiser, wherein the source is arranged to accelerate the liquid through the atomiser into the compression chamber and the dimensions of the duct are sized to define an inertia of the liquid therein to control the rate of acceleration of the mass flow through the atomiser during compression such that the flow rate of liquid into the compression chamber is substantially reduced when the pressure difference between the source and the compression chamber is high and substantially enhanced when the pressure difference between the source and the compression chamber is low.  
     
     
         2 . A gas compressor according to  claim 1 , wherein a valve is provided to control the timing of the flow through the atomiser.  
     
     
         3 . A gas compressor according to  claim 1  or  2 , wherein the dimensions of the duct are sized to define the inertia such that the mass flow increases through the nozzle in a period of at least 30°, preferably at least 45° and more preferably at least 60° of crank angle of a nominal crank shaft driving the piston.  
     
     
         4 . A gas compressor according to any one of  claims 1  to  3 , wherein the pressurised source comprises a reservoir of liquid pressurised by compressed gas.  
     
     
         5 . A gas compressor according to  claim 4 , further comprising means arranged to feed compressed gas from the compression chamber to pressurise the liquid in the reservoir.  
     
     
         6 . A gas compressor according to  claim 4  or  claim 5 , wherein the reservoir is an accumulator, and further comprising a separator upstream of the accumulator which receives gas and liquid from the compression chamber, means to feed the liquid in the separator to the accumulator, and a cooler to cool the liquid being fed from the separator to the accumulator.  
     
     
         7 . A gas compressor according to any preceding claim comprising a further duct arranged to feed liquid from the reservoir to the atomiser.  
     
     
         8 . A gas compressor according to  claim 6 , wherein the dimensions of the further duct are sized to define an inertia of liquid therein different to the inertia defined by the dimensions of the duct.  
     
     
         9 . A gas compressor according to any preceding claim, comprising a further atomiser for spraying liquid into the compression chamber, the flow through the further atomiser being controlled by a further valve.  
     
     
         10 . A gas compressor according to  claim 9 , wherein a branch duct connects the duct with the further duct.  
     
     
         11 . A gas compressor according to  claim 10 , wherein a third valve is provided in one of the ducts upstream of the location where the branch duct joins the duct, while the valve and further valve are downstream of the branch duct.  
     
     
         12 . A method of controlling the temperature of gas in a gas compressor during compression, the gas compressor comprising a compression chamber to contain gas to be compressed, a compression piston to compress the gas by movement of the compression piston in the compression chamber, a pressurised source of liquid and a duct arranged to feed liquid from the pressurised source to the compression chamber, the method comprising the steps of spraying liquid into the compression chamber by allowing the source to accelerate liquid through the duct and controlling the rate of acceleration of the mass flow into the compression chamber during compression by sizing the duct to define an inertia of liquid therein such that the flow rate of liquid into the compression chamber is substantially reduced when the pressure difference between the source and the compression chamber is high and substantially enhanced when the pressure difference between the source and the compression chamber is low.  
     
     
         13 . A gas compressor comprising a compression chamber to contain gas to be compressed, a compression piston to compress the gas by movement of the compression piston in the compression chamber, valve means for allowing compressed gas to be drawn from the compression chamber, an atomiser for spraying liquid into the compression chamber to absorb heat from the gas during compression, a pressurised source of liquid and a duct arranged to feed liquid from the pressurised source to the atomiser, wherein the source is arranged to accelerate the liquid through the atomiser into the compression chamber and the dimensions of the duct are sized to define an inertia of the liquid therein to control the rate of acceleration of the mass flow through the atomiser during compression such that liquid can be injected into the compression chamber when the pressure in the compression chamber is greater than the pressure of the source.  
     
     
         14 . A gas compressor according to  claim 13 , wherein the inertia is such that the period during which liquid is injected while the pressure in the compression chamber is greater than the pressure of the source is at least 5°, preferably at least 10° and more preferably at least 15° of crank angle of a nominal crank shaft driving the piston.  
     
     
         15 . A method of controlling the temperature of gas in a gas compressor during compression, the gas compressor comprising a compression chamber to contain gas to be compressed, a compression piston to compress the gas by movement of the compression piston in the compression chamber, a pressurised source of liquid and a duct arranged to feed liquid from the pressurised source to the compression chamber, the method comprising the steps of spraying liquid into the compression chamber by allowing the source to accelerate liquid through the duct and controlling the rate of acceleration of the mass flow into the compression chamber during compression by sizing the duct to define an inertia of liquid therein such that liquid is injected into the compression chamber when the pressure in the compression chamber is greater than the pressure of the source.  
     
     
         16 . A method according to  claim 15 , wherein the inertia is such that the period during which liquid is injected while the pressure in the compression chamber is greater than the pressure of the source is at least 5°, preferably at least 10° and more preferably at least 15° of crank angle of a nominal crank shaft driving the piston.