Economizer injection in a reciprocating compressor

Abstract

A compressor includes a cylinder block having a first bore and a cylinder head overlapping the cylinder block. The cylinder head has a second bore aligned with the first bore. The second bore is separated into a plurality of distinct regions including a suction region and an economizer region. A plurality of valves includes a suction valve selectively operable to fluidly couple the suction region and the first bore, and an economizer valve selectively operable to fluidly couple the economizer region and the first bore.

What is claimed is: 
     
         1 . A method of operating a reciprocating compressor comprising:
 drawing a first flow of refrigerant into a cylinder of the reciprocating compressor via a suction valve;   moving a piston within the cylinder to increase a pressure within the cylinder;   drawing a second flow of refrigerant into the cylinder of the reciprocating compressor via an economizer valve;   moving the piston to further increase the pressure within the cylinder; and   discharging a mixture of the first flow of refrigerant and the second flow of refrigerant from the cylinder via a discharge valve.   
     
     
         2 . The method of  claim 1 , wherein the economizer valve and the discharge valve are closed during the drawing the first flow of refrigerant into the cylinder. 
     
     
         3 . The method of  claim 1 , wherein the suction valve and the discharge valve are closed during the drawing the second flow of refrigerant into the cylinder. 
     
     
         4 . The method of  claim 1 , further comprising determining when the piston is at a desired position within a cycle of movement, the desired position being associated with operation of the economizer valve. 
     
     
         5 . The method of  claim 4 , wherein determining when the piston is at the desired position within the cycle of movement further comprises:
 determining if the pressure within the cylinder is equal to or greater than a predetermined threshold of an economizer pressure; and   determining a direction of movement of the piston within the cylinder.   
     
     
         6 . The method of  claim 5 , wherein determining the direction of movement of the piston within the cylinder further comprises determining a rate of change of the pressure within the cylinder. 
     
     
         7 . A method of operating an economizer valve associated with a cylinder of a reciprocating compressor, the method comprising:
 measuring a pressure within the cylinder;   determining if the pressure within the cylinder is equal to or greater than a predetermined threshold of an economizer pressure; and   determining a direction of movement of a piston within the cylinder in response to determining that the pressure within the equal to or greater than the predetermined threshold of the economizer pressure.   
     
     
         8 . The method of  claim 7 , further comprising opening the economizer valve when the direction of movement of the piston is upwardly. 
     
     
         9 . The method of  claim 7 , wherein determining the direction of movement of the piston within the cylinder further comprises determining a rate of change of the pressure within the cylinder. 
     
     
         10 . The method of  claim 9 , wherein the direction of movement of the piston is upwardly when the rate of change of the pressure within the cylinder is positive. 
     
     
         11 . The method of  claim 7 , wherein determining if the pressure within the cylinder is equal to or greater than the predetermined threshold of the economizer pressure further comprises:
 measuring the economizer pressure; and   comparing the pressure within the cylinder with the economizer pressure.   
     
     
         12 . The method of  claim 7 , further comprising maintaining the economizer valve in a closed position if the pressure within the cylinder is less than the predetermined threshold of the economizer pressure.