Influence of Cylinder Bore Volume on Pressure Pulsations in a Hermetic Reciprocating Compressor

Suction pressure pulsations created when the suction valve opens are caused by unsteady mass flow through the valve exciting acoustic resonances in the suction plenum. These pressure pulsations influence valve dynamics, compressor performance and compressor noise. This paper will show the importance of including the cylinder bore volume in the flow path analysis in order to accurately calculate pressure pulsations. Pressure pulsations will be calculated using Finite Element Method (FEM) calculated impedance transfer matrix method in a quasi-static solution. The method models the impedance of the suction plenum flow path including cylinder bore volume using a static geometry condition just after the suction valve opens. The interaction between the suction plenum, suction valve port geometry, and cylinder bore volume influence acoustic resonances in this system. These resonances cause pressure pulsations that effect valve dynamics. This paper uncouples the dynamics of the suction valve from the pressure pulsation modeling. This was done to specifically look at pressure pulsation created due to refrigerant volume flow through the suction valve and suction plenum acoustic resonances without valve dynamics influencing pressure pulsation. The paper then compares simulated suction plenum pressure pulsations when the valve opens to measured pressure pulsation in a reciprocating residential HVAC compressor with good agreement