Qualification of heat flux sensors in high enthalpy flows

Abstract

Comparative heat flux measurements were performed in the hypersonic high enthalpy flow field of the arc heated facility L2K. Three different sensors were compared: two cold wall heat flux sensors, a heat flux microsensor and a transient probe, and one hot wall heat flux sensor, which is made of tile material and is applicable at surface temperatures up to 1500 K. Tests were carried out in both, stagnation point and flat plate configuration at two flow conditions with different specific enthalpies. For the stagnation point tests the influence of model and sensor geometry was excluded by integrating the sensors into a flat faced cylinder with a diameter of 100 mm. In flat plate configuration the sensors were embedded in an insulation material to avoid heat conduction to the water-cooled model holder. Furthermore, flat plate testing was used to investigate the sensors' sensitivity to extraneous radiation, which emanates from the reservoir of high enthalpy facilities or hot surfaces of re-entry vehicles. The results confirm that extraneous radiation has an influence on the measurement and has to be considered in the evaluation of measured data.