Time-of-flight diode-laser velocimeter using a locally seeded atomic absorber: Application in a pulse detonation engine
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A diode-laser velocimeter based on atomic absorption spectroscopy has been developed and applied to a pulse detonation engine (PDE). The velocimeter uses a salt-coated sting to seed an atomic absorber at any desired location and a single, fixed-wavelength diode laser to monitor the absorber's presence downstream of the sting. Salt particles stripped from the sting tend to form distinct "clouds" of the atomic absorber rather than a uniform absorber stream. Gas velocity is inferred by measuring the time of flight of these clouds over a known distance. The properties of the salt coating can, in principle, be adjusted to tailor the velocimeter to a variety of flows and optimize its time response. In a PDE operating on C2H4 / O2, CsCl salt was seeded from a 150 \(\mu \)m diameter sting, and the D2 transition of atomic Cs near 852 nm was probed. Gas velocity histories, spanning 0-1000 m/s over a duration of \(\sim \) 6 ms, were recorded in the PDE and used to validate detonation models. Images obtained using an array of stings in a PDE are presented to demonstrate the potential for multidimensional velocimetry and to provide insight into the physics of the salt seeding.
Keywords:Velocimetry Cesium Absorption Pulse detonation engine
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