Gasdynamic quantities within an underexpanded free jet were measured nonintrusively using a rapid-tuning, CW ring dye laser. A nitrogen jet was seeded with 0.5 % NO in N2, and the conditions were controlled such that a barrel shock formed. The frequency-doubled output of the dye laser was used to spectrally resolve rotational lines in the NO gamma band near 225 nm. With the rapid-tuning capabilitiy, these rotational spectra were acquired at a repetition rate of 4 kHz. Spatial resolution was afforded by monitoring the induced fluorescence via a lens and photomultiplier tube. Modeling the spectrally-resolved features with Voigt profiles permitted simultaneous measurements of NO velocity, rotational temperature, and pressure. Expansion of the jet was assumed to be isentropic, and agreement between measured and expected values was tyically better than 10 % over most of the Mach-number range encounted. At high Mach numbers, the measured rotational temperatures systematically departed from the isentropic temperature distribution. Such a measured departure could be ascribed to the onset of a non-Boltzmann distribution of NO rotational states.
CW dye laser technique for simultaneous, spatially-resolved measurements of temperature, pressure, and velocity of no in an underexpanded free jet
Farbwellenlasertechnik für nachgebildete, räumlich getrennte Messungen der Temperatur, des Druckes und der Geschwindigkeit von Stickstoff in einem Freistrahl
AIAA-Papers ; 1-15
1992
15 Seiten, 11 Bilder, 23 Quellen
Aufsatz (Konferenz)
Englisch