A supersonic high-enthalpy tunnel developed at CNPM-CNR to test hydrogen autoignition and combustion under simulated flight conditions in the high supersonic - low hypersonic range is capable of sustaining supersonic 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 as a function of the upstream stagnation conditions. An efficient-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 influence was confirmed.
Hydrogen autoignition and combustion in supersonic flow at low equivalence ratio
G Riva;G Daminelli;
1997
Abstract
A supersonic high-enthalpy tunnel developed at CNPM-CNR to test hydrogen autoignition and combustion under simulated flight conditions in the high supersonic - low hypersonic range is capable of sustaining supersonic 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 as a function of the upstream stagnation conditions. An efficient-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 influence was confirmed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
