Abstract
A direct drive servovalve has some inherent benefits over its conventional counterparts, but also has better reliability and output power. However, due to the rigid connection between the spool and the motor, which takes the place of interstage drive-by fluid, the spool oscillation is a long-standing unsolved problem. In order to study the oscillation mechanism and the influencing factors, a double-circuit direct drive servovalve was numerically simulated. An oil return valve cavity was concentrated on as the main flow domain and was used to analyze the fluid flow characteristics. Local cavitation fraction and surface average cavitation fraction were defined to evaluate the cavitation situation. The periodic growth process of bubbles in the valve cavity was obtained. The numerical results show that bubbles in the oil return valve cavity changes, although the occurrence, evolution, and collapse stages were certain. The intensity of pressure pulsation caused by bubble variation is highly related to the bubbles causing the cavitation, which suggests a workable way to inhibit the spool oscillation.
Highlights
The electro-hydraulic system has many advantages, including, but not limited to, a compact structure, high power density, fast response and a large rigidity
Constant boundaries applied to the flow domain tend to visualize the cavitation from generation and evolution to collapse with a relatively certain regularity
The results prove the relevance of the pressure and the cavitation
Summary
The electro-hydraulic system has many advantages, including, but not limited to, a compact structure, high power density, fast response and a large rigidity. Direct drive servovalves are a promising alternative They adopt a linear or rotary motor to move the spool instead of a pilot stage. The direct drive scheme avoids interstage fluid power transmission but introduces touch interaction. It usually transmits power by the mechanical connector between the motor and the spool [8]. A double-circuit valve serves as a control component in the double surface actuation system in aircraft. It often employs a long and thin link to push or pull the spool. Spool oscillation is a long-standing unsolved problem, which can be associated with long link stiffness, fluid-solid coupling or self-excitation [9,10]
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