PRESSURE CALCULATION IN A COMPRESSOR CYLINDER BY A MODIFIED NEW HELMHOLTZ MODELLING

Abstract Pressure pulsation has a critical importance in the design of refrigerant compressor since it affects the performance by increasing over-compression loss, and it acts as a noise and vibration source. For the numerical analysis of pressure pulsation, quasi-steady flow equation has been used because of its easy manipulation derived from the pressure difference. By considering the dynamic effects of fluid, a new Helmholtz resonator model was also proposed on the basis of the continuity and the momentum equations, which consists of necks and cavities in flow manifolds. In this paper, a modified new Helmholtz resonator is introduced to include the gas inertia effect due to the volume decrease in the cavity. Comparisons between this modified new Helmholtz calculations and experimental results show that it is necessary to include the gas inertia effect in predicting pressure over-shooting phenomena at an instant of valve opening state and this modified new Helmholtz model can describe the over-compression phenomena in the compressor cylinder, a phenomenon which hinders a noise source identification of compressor.