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In this study, heat-flux measurement system using co-axial
thermocouples and thin film gauges was constructed. Instantaneous
changes of flow properties behind the incident shock in a shock
tube were used to detect the response characteristics of the temperature
sensors. The response time of co-axial gauge at the stagnation point is
about 10msec. Because the surface quality of sensors may change due to
the severe environment in shock tunnel, calibration of sensor on site is
very important. The hypersonic aero-thermodynamic problems on a sharp
cone-cylinder model were studied in which thermal gauges were installed
on the model surface to measure the heat flux. Tests were conducted in
Mach 6.8 flow in a shock tunnel.
The free stream properties in the test section of the shock tunnel were
measured with Pitot probe and stagnation temperature probe. Experimental
results showed good repeatability and accurate control of initial
condition can be achieved. Based on the Pitot pressure results, the useful
test time is about 9.5 ms, and the free stream Mach number is less than
theoretical isentropic value due to the growth of boundary layer thickness.
The mass flux and momentum flux were calculated based on the pitot pressure
and stagnation heat flux (pt2 ,q.sph) via Fay-Riddell relation. The results
of heat flux measurements at the model surface show that the heat flux
concentrates in the vicinity of the stagnation point which agrees well with
the estimation using Eckert*s reference temperature. The measurement and
calibration systems constructed have showed high performance on both accuracy
and frequency response.
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