Analysis of a pneumatic probe for measuring exhaust-gas temperatures with some preliminary experimental results

Scadron, Marvin D.

A pneumatic probe based on continuity of mass flow through restrictions separated by a cooling chamber was constructed to measure gas temperature at and beyond the limit of thermocouples. This probe consisted of a subsonic flat-plate orifice for the first restriction and a sonic-flow converging-diverging nozzle for the second restriction. The effect of variation in gas constants on the calibration of the probe at temperatures up to 2000 R and Mach numbers up to 0.8 is described. Agreement to better than 30 R between pneumatic probe indication and the indication of a rake of radiation-shielded thermocouples indicates that extrapolation of the calibration to higher temperatures is possible with fair accuracy.

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