A new concept of heat-flux probe for the Scirocco Plasma Wind Tunnel

Abstract

Within the project "Calibration Heat Flux Probe", planned and developed within the program "Cibapark" by CIRA, a probe for stagnation point heat flux measurements, based on a "slug sensor" has been designed and realized. Such a sensor, particularly useful for high heat flux measurements arising in atmospherical re-entry conditions, offers great advantages compared with traditional alternatives (Gardon gage) such as low cost and prolonged durability. The sensor is made up of a metallic cylinder (slug) positioned in the probe's surface but physically separated by a thermal insulating material; the sensor's back face is equipped with a thermocouple. During the exposure to the heat flux, after a short transition period, temperature starts to grow linearly with time; by the slope of the curve and the knowledge of the thermo-phisical properties of the material (density and specific heat) the heat flux can be determined. The paper deals with the design, realization and test of this sensor for a test in the Scirocco plasma wind tunnel. Moreover, the heat flux evaluated by means of the thermocouple measurement has been also evaluated by means of a thermographic temperature measurement, and this method gave the same results. Nomenclature q & = local heat flux M = mass of the slug c = specific heat T = Temperature A = area of the front surface of the slug k = thermal conductivity ρ = density ∆T mp = necessary temperature difference to reach the melting point ∆t mp = necessary time difference to reach the melting point r b = radius of the basis of the flat face R eq = equivalent radius in terms of heat flux 1 Ph.D in Aerospace, Lab. Head,