Simultaneous Shock-Tube Wall-Heat-Flux and Temperature Measurements by Atomic Layer Thermopiles

This study focuses on the validation of other static calibration methods and dynamic evaluation of atomic layer thermopile (ALTP) sensors in a shock tube environment. Flush-mounted ALTPs are exposed to a traveling shock wave at the end wall and side wall of a shock tube. For the measurements, the heat flux at the end wall is directly determined by an ALTP sensor and is compared with analytical end-wall solutions. The analytical heat-flux progression is derived from estimations for post-reflected-shock conditions based on pressure data and one-dimensional computations. The experimental data compare well with the time-invariant, analytically determined heat-flux progression for both low- and high-pressure conditions. As part of these shock tube experiments, a dynamic heat-flux and temperature analysis of the sensor is also conducted at the side wall and end wall of the shock tube. To enable this, a newly developed methodology for direct and simultaneous measurement of heat-flux density and temperature in ALTPs is used. Based on this approach, the dynamic response of both heat flux and temperature is investigated: the ALTP heat-flux response on the side wall compares well with laser-based dynamic calibration results, whereas the response of the end-wall sensor significantly underestimates the optically predicted response times. For the first time, the dynamic response of ALTP temperature data could be investigated in short-duration shock tube experiments and compared with coaxial thermocouple readings.