Abstract
A supersonic high-enthalpy tunnel developed at CNPM – CNR to test hydrogen autoignition and combustion under simulated ight conditions in the high supersonic – low hypersonic range is capable of sustaining supersonic combustion for 10 – 30 ms, the ow residence time being about 1 ms. A simple but effective procedure for data analysis based on detailed static and total pressure measurements provides information on the one-dimensional quasisteady thermo uid-dynamic eld inside the tunnel as a function of the upstream stagnation conditions. An ef cient-mixing discrete-hole cross-stream injector was adopted, which also allowed hydrogen preheating. The equivalence ratio was limited to values #0.15 to keep the airstream supersonic in the constant cross-sectional portion of the tunnel. Autoignition delay data were obtained (0.1 – 1 ms) and correlated with the local static temperature. The results agree with experimental and theoretical literature data available for cold hydrogen. A strong effect of fuel temperature was observed, suggesting that a meaningful database for scramjet applications should always include, if appropriate, fuel preheating. Overall reaction times were also evaluated for different fuel temperatures, whose remarkable in uence was con rmed.
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