Computational study of poppet valves on flow fields

Abstract

Valves are critical components in a fluid flow network. Based on the type of fluid used, valves may suffer unforeseen wear and tear that might lead to an inadvertent failure. Major work in this thesis is focused on high pressure water valves that are used for descaling purposes. Controlling fluid flow at high pressures is not only challenging but also becomes time-wise critical. Failure of one such high pressure un-loader valves was studied first for the feasibility of my thesis work. A reverse flow operation was set in one such valve due to piping constraints established by industrial requirements. Experience and data recording showed that the premature failures of such valves by BOC Water Hydraulics were seen in months which lasted for years in standard operation. Computer simulation was being utilized to understand the fluid phenomena at such high pressures. The highly energized fluid from the descaling pump sets off a static pressure of 4300 psi at the valve inlet. It is responsible for continuous fluid flow rate of up to 208 gpm when the valve becomes fully open. Computational Fluid Dynamics (CFD) approaches are widely being utilized for fluid research in design optimizations. A Standard Turbulence model was used to understand the fluid flow variables using velocity/pressure contours for several possible valve opening positions. A very low pressure developed below the poppet seat of the valve suggests the onset of cavitation zones which may lead to leakage. Leakage at such a descaling pressure further accounts for cavitation and may which ultimately affect valve's overall performance resulting in cartridge replacement. Using CFD, the poppet valve assembly was modeled and simulated using ANSYS Fluent, commercially available CFD software. Low pressure below the atmospheric gage pressure in the valve body is found to be responsible for the initial onset of cavitation.