Comparing FEM Transfer Matrix Simulated Compressor Plenum Pressure Pulsations to Measured Pressure Pulsations and to CFD Results

摘要

Improving efficiency of positive displacement compressors requires improving current computer compressorrnsimulations to better model compressor behavior. This paper will specifically look at increasing fidelity of the 1Drnthermodynamic compressor simulation program by incorporating suction and discharge pulsations due to complexrnsuction and discharge three dimensional (3D) plenum geometry. This method allows for quick pressure pulsationrnanalysis and enables the design engineer to make changes early in the compressor development cycle. FiniternElement Method (FEM) full harmonic analysis is used to calculate suction or discharge plenum’s impedancerntransfer functions in the frequency domain. The impedance transfer functions are normalized to the FEM conditionsrnand normalized impedance transfer functions are used to model all compressor operating speeds and operatingrnconditions. The normalized impedance transfer functions are independent of mass flow, compressor speed, valverndynamics, sonic velocity, refrigerant density, refrigerant, bore size and stroke size which allow the 1D compressorrnsimulation program to change any of these variables without have to solve for a new FEM impedance transferrnfunction. We have also worked on a new way to include damping and phase shift between mass flow and pressurernpulsations that better agrees with experimental and Computational Fluid Dynamics (CFD) results. Since some ofrnthis method is novel or may extend beyond the limits of linear acoustic analysis, it requires good agreement torncompressor test results and to CFD results. The main part of the paper will show good agreement betweenrnsimulated pressure pulsations to suction and discharge test results in a reciprocating compressor. The paper willrnalso show our latest improvements in pulsation modeling to obtain better agreement to CFD results than the originalrncomparison in Bilal et al.( 2010).