A new measurement by using a catalytic reaction on a platinum wire was conducted spatially to evaluate a mixing condition in a supersonic flow field. A spatial mixing field was created by a transverse hydrogen jet injected into a cold supersonic cross flow (Mach 1.81) through a wedge shaped injector. The half-vertical angles of 8 or 18 were chosen as that of the wedge shaped injector. These results were compared with that of a circular injector case. The results showed that this method could evaluate a spatial mixing condition. The results also clarified that a jet plume in the cases of wedge injectors penetrated higher than that of the circular injector case and separate from the lower wall when going downstream. To observe jet/supersonic flow interaction, Schlieren visualization and oil flow visualization were carried out. It was shown that the extent of the separation region around the 8 wedge injector was the smallest among those injectors. Pitot pressure measurements were also conducted. These indicated that a wedge injector scheme was more beneficial than that of a circular injector for the supersonic combustion and combustor wall cooling.

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An experiment was carried out to confirm the validity of time series evaluation of supersonic mixing conditions by using the catalytic reaction on a platinum wire. Gaseous hydrogen was injected parallel to a supersonic freestream (M 1 % 1:81) from a slit injector, located at a backward-facing step. The time series condition of supersonic mixing was evaluated using a W-type probe with a platinum wire and a reference (nickel) wire. The evaluation was done by simultaneously measuring each electric power supplied by each electric circuit keeping the temperature of the wire constant. Electric power supplied to the Pt wire depended on the catalytic heat release rate (giving hydrogen concentration) and flow convection. Meanwhile electric power supplied to the Ni wire depended on flow convection. The results show that the correlation coefficient between these electric powers increased as mixing developed. Investigations were also conducted for the cases of helium, air, and no secondary injectant to compare with the hydrogen-injectant case. The results indicate that this evaluation method can measure the time-series behavior of the air-hydrogen supersonic mixing layer or coherent motion of turbulence.

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