Abstract
The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area. However, the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate, resulting in special cavitation phenomenon on the spherical port plate pair. In order to study cavitation characteristics of spherical port plate pair, a dynamic CFD model of the piston pump including turbulence model, cavitation model and fluid compressibility is established. A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh, which makes up for the lack of research on the meshing of the spherical oil film. In this paper, using CFD simulation tools, from the perspectives of pressure field, velocity field and gas volume fraction change, a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out. The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point. The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface. These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair. The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate, but also cause strong impact and denudation on the lower surface of the cylinder body. Finally, the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.
Highlights
In hydraulic system, cavitation is one of the main reasons that cause mechanical vibration, noise, and deterioration of the reliability and durability of pumps and valves [1,2,3,4,5]
The data at the point point 2 (P2) can be collected in real-time, the trajectory of P2 is expressed as follows: xP2 = R0 × cos((2π n/60) × time + φ0), yP2 = R0 × sin((2π n/60) × time + φ0), zP2 = 0.021, where R0 is the distance from the point P2 to the origin, n is the rotor speed, φ0 is the initial phase, and zP2 is the vertical height from the original center
In order to elaborate evolution mechanism of cavitation erosion in detail, under the condition that the inlet/outlet mass flow error is less than 0.5%, the hydrodynamic parameters at each observation point and cross section are analyzed, such as fluid velocity and velocity vector diagram, gas volume fraction (GVF), gas volume fraction cloud image, and pressure field
Summary
Cavitation is one of the main reasons that cause mechanical vibration, noise, and deterioration of the reliability and durability of pumps and valves [1,2,3,4,5]. In order to study the cavitation phenomenon of flow field under the condition of using spherical valve plate/ cylinder block pair, the hydrodynamic hybrid simulation model of a piston pump with spherical valve plate/cylinder block pair is established firstly by using UDF surface modeling technology, which solves the problem that it is difficult to model the fluid domain of micron-level large curvature spherical oil film. The evolution process with cylinder angular displacement of triangular groove jet pressure, velocity and gas volume fraction cloud image is analyzed in detail. By combining the cloud image evolution process with the velocity vector direction and the change of gas volume fraction at the reference points, the simulation results and the experimental results are compared to verify the cavitation damage mechanism of the flow distribution plate and the bottom of the cylinder. The original cavitation model proposed by Singhal et al [31] describes the steam distribution as shown in Eq (8):
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