Appropriate liquid fuel and purge air check valves can provide 95% operational availability and reliability, a number far better than the typical 35 to 40% for most dual fuel applications.
The liquid fuel check valve is the first component which should be addressed when seeking to improve fuel system reliability. Two key characteristics of the liquid fuel check valve design should be passive dampening and active cooling. These features address the most common failure modes which have been seen over the past couple of decades. JASC’s liquid fuel check valve uses an active Helmoltz resonator for stability control.
Active cooling is the next key characteristic which is required for a liquid fuel check valve design. Keeping the valve internals below the threshold which allows the formation of coke ensures that an ANSI Class 6 seal is maintained in the checked and reverse flow direction from hot gas path inspection to hot gas path inspection. The absence of coke formation in check valves also enhances the ability to start the turbine on liquid fuel and to transfer back and forth between fuels because the check valves are able to maintain the same crack pressures. JASC’s water-cooled liquid fuel check valve has a water jacket added to the standard liquid fuel valve design to eliminate coking on valve internals.
The purge air check valve is the second component which should be addressed. The design should be contamination tolerant, chatter resistant and provide an ANSI Class 6 seal in the reverse flow direction. Given the low force margin which is required for opening the valve (less than 1 PSI) the check valve design should incorporate a knife edge seat to improve its tolerance to contamination. JASC’s purge air check valves are designed with minimal surface area at the seal to limit contamination impact.
As gas turbine engine designs have a wide variety of configurations for the liquid fuel, purge air and water injection systems, we recommend that you contact JASC for details on how this hardware can be used to benefit your specific application.