Time Response Calibration of Ultra-Fast Temperature Sensitive Paints for the Application in High Temperature Hypersonic Flows

Abstract

Ultra-fast measurements (acquisition rates of 1MHz) of time varying surface temperatures using temperature sensitive paints, TSPs, is a very promising but also challenging technique to obtain experimental heat flux distributions in hot hypersonic impulse facilities. The demand on experimental data of heat flux distributiosn in hot hypersonic ground based testing facilities [1] drives the development of the classical TSP techniques towards ultra-fast applications. A main advantage over classical measurement techniques used over the last five decades [2], such as thermocouple or thin film gauge measurements is that spatially highly resolved data can be obtained with TSP. Additionally a reduction of the huge preparation times of wind tunnel models (generally required due to the integration of a large number of temperature gauges) is possible. However, compared to the application of TSP in low speed flows or in continuously running ground based test facilities, the utilization of the TSP technique in impulse facilities results in a number of new specific requirements and challengs not completely resolved so far. Therefore, this paper will present a calibration setup to determine the response time of thin thermal active layers which are constructed from TSP solutions. A high power laser system is used to generate a Gaussian laser spot on a TSP have a duration of a few ns only. A complete TSP system is used to measure the time response function (temperature decay). The decay functions can be used to characterize the response time of the TSP used and its dependence on the thickness of the TSP layer. The experimental results will be presented and on the basis of the analysis, conclusions that can be drawn with respect to the applicability in hot hypersonic hypersonic impulse facilities will be discussed.