Abstract
The paper presents a numerical simulation and analysis of the flow inside a poppet valve. First, the single-phase (liquid) flow is investigated, and an original model is introduced for quantitatively describing the vortex flow. Since an atmospheric outlet pressure produces large negative absolute pressure regions, a two-phase (cavitating) flow analysis is also performed. Both pressure and density distributions inside the cavity are presented, and a comparison with the liquid flow results is performed. It is found that if one defines the cavity radius such that up to this radius the pressure is no larger than the vaporization pressure, then both liquid and cavitating flow models predict the cavity extent. The current effort is based on the application of the recently developed full cavitation model that utilizes the modified Rayleigh-Plesset equations for bubble dynamics.
Highlights
In hydraulic power systems, cavitation most frequently occurs in system valves, pumps, and actuators
Large differences in pressure are a frequent cause of small-scale cavitation in chambers of four-way spool valves, while highfrequency motion of a valve-controlled actuator can lead to large-scale cavitation in the cylinder
The flow inside the poppet valve is a complex process that is strongly dependent on the details of the valve geometry, the fluid properties, and the operating conditions
Summary
Cavitation most frequently occurs in system valves, pumps, and actuators. Process control valves on the other hand are used for precise control of the fluid flow rate due to the linear or equal percentage characteristics These type of valves usually have small clearances between the plug and the seat. Despite these differences, many of the flow phenomena in the hydraulic valve such as recirculation and jet separation and reattachment occur in the process control valve. Velocity vector field in section plane shows the large recirculation region confirming the very strong nature of the helical vortex flow in this poppet valve geometry (Figure 2). As shown in our previous work [18], the cavitation region is relatively large in a poppet valve chamber; we expect a significant change of the flow field compared with the single-phase flow. We examine the differences between single-phase and two-phase models in terms of the flow rate and streamline pattern
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