Novel Design of an Orifice Control Element

An orifice element is commonly used in liquid rocket engine test facilities either as a flow metering device, a damper for acoustic resonance, or to provide a large reduction in pressure over a very small distance in the piping system. The orifice as a device is largely effective in stepping down pressure; however, it is also susceptible to a wake-vortex instability that generates pressure fluctuations that propagate downstream and interact with other elements of the test facility, resulting in structural vibrations. Exacerbating the situation in cryogenic test facilities is the possibility of the formation of vapor clouds when the pressure in the wake falls below the vapor pressure, leading to cavitation. Cavitation has the potential for highamplitude fluctuations that can cause catastrophic damage to a facility.