HYDROGEN AUTOIGNITION AND COMBUSTION IN SUPERSONIC-FLOW AT LOW EQUIVALENCE RATIO

A supersonic high-enthalpy tunnel developed at CNPM-CNR to test hydrog en autoignition and combustion under simulated night conditions in the high supersonic-low hypersonic range is capable of sustaining superso nic combustion for 10-30 ms, the flow 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 thermofluid-dynamic field inside the tunnel a s a function of the upstream stagnation conditions, An efficient-mixin g discrete-hole cross-stream injector was adopted, which also allowed hydrogen preheating, The equivalence ratio was limited to values less than or equal to 0.15 to keep the airstream supersonic in the constant cross-sectional portion of the tunnel, Autoignition delay data were o btained (0.1-1 ms) and correlated with the local static temperature, T he results agree with experimental and theoretical literature data ava ilable for cold hydrogen, A strong effect of fuel temperature was obse rved, suggesting that a meaningful database for scramjet applications should always include, if appropriate, fuel preheating, Overall reacti on times were also evaluated for different fuel temperatures, whose re markable influence was confirmed.