The estimation of the pressure pulsation damping coefficient of a nozzle

The attenuation of pressure pulsation in volumetric compressor manifolds is a result of three factors: anti-resonance, viscosity and vorticity. Two main methods are considered as the standard approach for the estimation of the element influence on pressure pulsations: a one-dimensional real time-space domain solution and a distributed acoustic impedance model (Helmholtz) approach solved in a complex domain. In both cases, only two types of pressure attenuation may be estimated: resonance characteristics and linear viscosity damping. In this paper, the assessment of pulsation damping caused by 3D vorticity effects is analysed. This effect is especially important while analysing the attenuation of the pressure pulsations of different nozzle shapes. A theoretical analysis based on the impulse flow 3D simulation is shown and compared to the classical solutions where 3D effects are neglected. The comparison shows that one-dimensional viscous damping estimation methods are insufficient. Using an impulse induced flow 3D simulation, the estimation of a given nozzle's damping characteristics may be obtained more accurately. Experimental evaluation of the proposed method is also presented. This method may also be applied for other manifold elements.