Single-Shot H(2) Cars Spectroscopy of Propellant Ignition and Combustion under Pressure

摘要

A single-shot H(2) CARS spectrometer was developed, and experimental considerations for accurate thermometry were examined. The spectrometer is capable of synchronization with external events such as laser-initiated propellant ignition or ballistic compression, given an inherent delay time of 250 microseconds and a predetermined diagnostic time window approaching 1 second. Additional capability to operate in a double Q-switched mode (two diagnostic probes 60 to 90 microseconds apart) has been demonstrated, with inherent delay time of 190 microseconds. Application to static samples of H(2) and to an H(2)/0(2) flame reveal unreferrence errors approaching 10% or more in temperature determination, and indicate the necessity for simultaneous standardization in accurate thermometry. Intensity determination in an unreferrenced fashion reveals fluctuations of 30%, with contributions from YAG and dye laser intensity and phase fluctuations. Q-branch lines from the first vibrational state (beta = 1) of hydrogen were observed for the first time in the H(2)/0(2) flame using this apparatus. Facilities have been established with which to perform single-shot H(2) CARS diagnostics on propellant ignition and flame under pressure. Preliminary experiments indicate the choice of background gas, flow rates through the pressure cell, YAG laser fluence, and dye laser spectral width are critical factors in the development of a working protocol. CARS spectra of nitrogen product gas pellant flame have been observed.