The influence of line and fluid parameters on pressure ripple in hydraulic transmissions

Abstract

Fluid borne noise sources in realistic hydraulic circuits can be affected by many geometric line details and the changing properties of working fluid. These phenomena need to be better understood and quantified for achieving inherent quietness through computationally designed hydraulic circuits. This paper uses one-dimensional finite element based modeling strategies to predict pressure waves generation and propagation in a realistic novel hydraulic hybrid transmission and compares simulations to measured data. The model is improved progressively with configurations that consider variable diameter, duct materials, and the presence of curvature of the lines. The modeling technique is composed of a one-dimensional method-of-characteristics solver bounded by two flow sources—lumped parameter axial piston units. Diameter and duct material were discretized into a grid along the length of the line. The effect of variation in the speed of sound was considered at each element of the one-dimensional grid. The differences between isothermal and adiabatic properties for the working fluid are also considered. The impact of aeration is also studied. A covariance algorithm is used in order to determine the aeration of the working fluid.