Visualization of flow phenomena in hydraulic throttle valves of plastics

Using elements made of plastics in hydraulic drives and controls encounters problems, for example related to strength. However, the advantage of solutions with plastics manifests itself, among others in possibility of shaping hydraulic elements in accordance with the assumed requirements. The use of additive manufacturing techniques allows us to make plastic parts with shapes that are unattainable for steel parts. The authors have attempted to determine the influence of the shape of the closing element on the phenomena of flow through the throttling gap in the hydraulic throttle valve. They chose three poppets of different shapes and carried out flow simulations using CFD. They compared simulation results in the form of flow velocity field in the valve chamber with observations obtained with the Particle Image Velocimetry (PIV) technique. In visualization tests, a throttle valve made of transparent materials and markers in a form of air bubbles were used. The tests confirmed the possibility of using air bubbles as markers of the PIV method at low pressure. The presented conclusions indicate the need for further modification of the shape of the closing element as well as of the design of the valve body.