In hydraulic power systems with water hydraulic valves, cavitation is more likely to happen than in an oil hydraulic system. A two-step throttle, which consists of two ori ces, is an effective way to avoid or reduce cavitation damage. In this research, experiments are conducted to investigate the ow-pressure and cavitation characteristics of throttles of different shapes. The working medium is tap water. A new indicator is introduced to detect cavitation inception, namely that a particular low-frequency component of the outlet pressure uctuation of valve appears and grows rapidly when cavitation occurs. From the experimental results, it can be concluded that the two-step throttle has different features to a single-step throttle.

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