Application of Infrared Thermography in an Expansion Tunnel

This work aims to investigate the viability of implementing infrared thermography to measure the surface temperature of test models in the X2 expansion tunnel at the University of Queensland, Australia. Infrared thermography is an attractive temperature measurement technique for small facilities with high enthalpy and high pressure flows due to the limitation on the spatial resolution of surface mounted instrumentation and the damage seen by these types of sensors. Intense shock layer radiation between the target and the sensor precludes the standard implementation of infrared thermography as used in other facilities. An approach of resistive model pre-heating and band pass filtering is employed to raise the signal from the model surface and exclude the majority of the flow radiation and therefore increase the ratio of target to flow radiation that is seen by the infrared detector. This methodology was employed to take measurements of two flow conditions, however, large sources of additional radiation, postulated to be from flow contamination from facility hardware, precluded the use of the technique with the high enthalpy condition used in this work. The low enthalpy condition also showed this additional radiation, however, the surface temperature of the target was able to be successfully measured using the proposed technique. The limitations and issues involved in the implementation of the technique in this work were identified and solutions and improvements are suggested for future work.