Experimental Investigations on Stagnation Point Heat Transfer in the Arc Heated Facility LBK.

Abstract

Comparative tests were performed on a SiC-sample in the stagnation point configuration of LBK using different pyrometer configurations to demonstrate improved performance of LBK concerning the measurement of surface temperatures with a good accuracy. A pyrometer with miniature optics integrated into the sample holder was successfully qualified for the measurement of the rear surface temperature of the sample. Good agreement was achieved in measured temperatures using both spectral and two- color pyrometers. The data on rear surface temperature showed that heat losses from the sample to the sample holder were only a few percent of the total heat flux rate into the sample. Hot wall heat flux rates were determined from the measured surface temperature for radiative equilibrium conditions. In order to provide useful data for the validation of numerical codes, detailed analysisses concerning the flow field properties and sample surface parameters were performed at two test conditions. Gas parameters of the free stream were computed using a quasi one-dimensional code with thermal equilibrium and chemical non-equilibrium models. Gas properties behind the shock and cold wall heat flux rates were calculated under the assumption of a frozen chemistry over the shock and a fully catalytic wall. Measured cold wall heat transfer by means of a transient heat flux probe was compared with computed heat fluxes to a flat faced cylinder and a sphere of a catalytic material.