Fast Valve for Starting Hypersonic Wind Tunnels

ABSTRACT: A valve is needed to operate the Air Forces Ludwieg wind tunnel.The valve must open full bore without obstructions to avoid shedding vortices that would disturb experiments in the downstream Mach 6 flow field.Safes design uses the Geneva mechanism and a weight-optimized ball valve to open in 33 msec.The Geneva mechanisms input sector accelerates to a high speed before engaging the output sector to turn the ball a precise number of degrees and hold it in position.The input sector disengages from the ball and decelerates afterward.Safe has developed a detailed dynamic simulation of the valves motion to demonstrate that the opening time can be achieved with practical selections for hydraulic fluid pressures, piston areas, and other operating variables.The ball mass is validated with structural analysis showing acceptable stress when holding against the full stored air pressure.An innovative seal prevents leakage past the valve while avoiding wear during operation.The technical approach includes the required tests of a manufactured prototype.Safes team has an expert in valve design with prior experience developing fast acting valves.The commercialization strategy is flexible and has been used to commercialize past SBIR technology.; BENEFIT: The benefit of the fast-acting valve is its ability to maximize the time that can be devoted to experiments in a clean and steady field of Mach 6 flow.It can be used repeatedly for a design life of 50,000 cycles with a quick turnaround time between tests.The Air Force will be able to conduct more experiments within a given test period, where each experiment uses more of the available 200 msec test time.Aside from operating Ludwieg tube wind tunnels, the valve may find other applications where fast action is needed; for example, to rapidly dump liquid sodium coolant into a nuclear reactor for emergency shutdown, where the extra milliseconds of response time may be beneficial to safety.The valve might also aid wind blast testing, such as at NAVAIRs facility which simulates the effects of the wind on a person in an ejection seat during a high speed (600 knots equivalent air speed) aircraft ejection.The speed of items ejected from gas guns, such as carcasses for aircraft bird strike testing, depends on the opening speed of the valve. Fast closing valves (the inverse of the design to be developed here) are used in explosion containment systems in many industries.