Strömungsinteraktionen, Kinematik und Verschleiß fluidgesteuerter Pumpenventile

Fluid driven valves are an essential component of reciprocating displacement pumps. Although pump valves are quite small and low-cost, process stability and quality depend highly on their reliability. Being in direct contact to the conveying fluid and exposed to strong mechanical stresses, fluid driven valves are the parts of reciprocating pumps with the highest failure rate. Furthermore, the valves affect the volumetric efficiency factor of the pump. They produce additional pressure losses and induce pressure pulsations due to the valve opening oscillations. The aim of this thesis is to characterise and understand the valve kinematics, as well as the interactions with the surrounding fluid and to gain comprehensive theoretical insight. The experimental findings are combined with numerical results from computational fluid and structure dynamics (CFD and FEM) to obtain calculation and design guidelines. Moreover, long time wear experiments are carried out to identify the main wear mechanisms and to evaluate their damaging potential. To understand the valve kinematics, a test rig was set up. The reciprocating pump is equipped with a multitude of pressure resistant windows granting a good view of the valve motion at real operating conditions. By means of a high-speed camera the valve motion is recorded synchronously to the pressure. With the help of computational fluid dynamic simulations of the pump, which take the fluid driven valves and the motion of the displacement body into account, many effects can be explained, the phenomena during the opening phase of the valve in particular. It became apparent that after the opening oscillations are damped out, the valve body follows the given flow rate in good accordance. This discovery made it possible to optimize the process of designing valves by using simplified quasi-stationary flow simulation models. The mechanical loads including the reflection of the in an aslant way closing valve bodies were calculated utilising computational structure analysis. The results presented in this work represent a scientific base to understanding the fluid-driven valve movement, the flow interactions and the different reasons why valves get worn. Based on the experimental and numerical findings, practical guidelines for the design of fluid-driven valves were developed to supplement the experience-based development process and to improve the design certainty.