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Woodward’s LQ25T liquid fuel metering valve is designed for use on industrial and aeroderivative gas turbine engines in the 6000 kW to 42 000 kW output power range. The valve is a twoway flow control valve utilizing a throttling type delta P regulator. This allows the valve to control pressure drop across the metering port without bypassing fuel, making it ideal for centrifugal or other pressure source type fuel pumping systems. The assembly provides a reliable, costeffective interface between electronic engine control systems and gas turbines used in power generation, mechanical drive and marine applications. The LQ25T valve utilizes corrosion-resistant, shear-type metering components that are positioned by a high-torque actuator to assure extended operation in all types of liquid fuel service. The LQ25T valve is compatible with diesel fuels, JP series, naphthas, kerosenes, gasolines, and other distillates conforming to nationally or internationally recognized standards for utility, marine and aviation gas turbine service.
Precise flow control is achieved by the use of a rotary plate valve integral with an electric actuator and a non-contacting position sensor. The use of rare earth permanent magnets in a highly efficient electromagnetic circuit minimizes package size. The integral brushless dc actuator and valve design eliminates the backlash associated with geared motors and avoids the resolution and cycle oscillation problems incurred with stepping motors. Each valve requires a remote electronic interface unit (the LQ driver, supplied separately) which accepts a 4 to 20 mA position command signal and operates with an 18 to 32 Vdc power supply. This controller also provides a 4 to 20 mA output proportional to the actual valve position.
The LQ25T rotary plate valve achieves a self-cleaning, shear-type metering action. The valve metering sleeve is integral with the actuator rotor, resulting in fuel metering with a single moving part. Optimal flow versus input signal characteristics are achieved on each valve by precision EDM manufacturing of the valve metering port. The LQ25T valve can achieve flow turn down ratios in excess of 100 to 1.
The GS/LQ valve driver (supplied separately) performs the following functions:
The GS/LQ driver may be located up to 100 meters from the valve assembly to avoid exposure to hazardous atmospheres and harsh environments.
Liquid fuel flow control is achieved by a combination of accurately scheduling the metering valve port area and regulating the differential pressure across the metering port. Factors such as fuel properties (specific gravity, viscosity, etc.), as well as fuel pressure and temperature all play a part in determining the accuracy of flow metering. The LQ25T valve is designed so that the effect of these factors on flow metering is minimized as much as possible. The inclusion of the throttling regulator allows the LQ25T valve to be used with centrifugal or other pressure source type fuel pumps.
Product Specification 40179