Optically Powered Hydraulic Pilot Valve using Piezoelectric Multilayer Actuator

Abstract A normally-closed 2/2 hydraulic pilot valve has been developed for a power- by-light system which is being applied in aerospace fuelling systems and oil-well applications. This system offers unique advantages such as good immunity from electromagnetic interference, intrinsic safety, and low attenuation for long distance. The valve employs a piezoelectric multilayer bender actuator (Pz29) with an elastomer blocking plate and a nozzle as the valve mechanism. The valve system is operated by 86 mW optical power which is transmitted via a multimode optical fibre (core diameter 62.5 μm) from a laser diode light source. The optical power is converted to electrical power by a photovoltaic cell, to drive the pilot valve, which requires, 8 mW electrical power to operate. The valve output flow- rate of 28 cm3/s has been achieved at an operating pressure of 1000 kPa, which is adequate for the applications. However, the maximum operating pressure up to 2000 kPa has already been tested. For the valve dynamic response, 18 ms average opening time and 1.5 seconds controllable smooth shut-off time have been observed. There was no valve operation failure during vibration testing up to 196 m/s2. The pilot valve is now used to operate an aircraft refuelling valve system that provides aviation fuel flow-rate up to 680 l/min. It can also be used for other hazardous environments and noisy applications.