A FAST-RESPONSE HIGH-SPATIAL-RESOLUTION TOTAL TEMPERATURE PROBE USINGA PULSED HEATING TECHNIQUE

This paper discusses the operation of a fast-response total temperatur e probe based on transient thin film heat flux gage technology. The pr obe utilizes two thin film gages located close to the stagnation point of a hemispherically blunted fused quartz cylinder. Development of th e present total temperature probe was motivated by the need for a fast -response device with a high spatial resolution. The diameter of the p robe was 2.8 min and the two films were separated by a distance of les s than 1 mm. Measurement of the flow total temperature requires the fi lms to operate at different temperatures. In the present work, the tem perature difference was generated using a current praise (approximatel y 70 mA with a duration of around 1 s) to heat one of the thin film re sistance gages. With this technique, temperature differences between t he hot and cold films of around 120 K were achieved. The interpretatio n of the transient surface temperature measurements is discussed and t he validity and utility of the technique are demonstrated with referen ce to total temperature and convective heat transfer coefficient measu rements in a compressible free jet. The results demonstrate that accur ate total temperature and convective hear transfer coefficient measure ments with high spatial and temporal resolution can be obtained with t he present device.