Cavitation an cavitation ersosion in poppet valves

Research Task/Objectives

Poppet valves are widespread in process technology, where safety and reliability with a wide range of media is essential. High flow velocities inside the valve gap cause local pressure drops that will - in combination with unfavourable operating conditions and/or the use of process media with a low boiling pressure - lead to significant vapour cavitation. The vapour bubbles implode in areas of rising pressure. If this process occurs near the component’s walls, cavitation erosion may be the consequence, depending on the collapse intensity. The objective of the research project is the development of a methodology capable to predict location and intensity of cavitation erosion. To do so, damage indicators of the cavitating flow have to be defined.

Approach/Results

The first step is the visual examination of the cavitating flow using shadowgraph imaging. A typical poppet valve is modified to enable optical and sensory  accessibility. This preliminary examination allows the definition of suitable states of cavitation that are afterwards analysed during long-term tests of cavitation  erosion. The exchangeable design of the valve model allows the analysis of the compromised valve parts after each test. A comparison of the patterns of damage allows the subsequent evaluation of the cavitation aggressiveness at different operation states. Using numerical investigations, local flow parameters are being identified that allow the prediction of cavitation erosion.

The presented research activities are part of a cooperation with the company Bürkert Werke GmbH. The authors would like to thank this company for the funding and support.