Evaluation of an uncooled focal plane array thermal imaging camera for effusion cooling research.

摘要

This research was aimed at assessing the usefulness of a low-cost, uncooled, ferroelectric-detector infrared camera for effusion cooling research. The thermal imager operated in the 7--14 mum waveband, had a 320 x 240 pixel focal plane array and was converted from an AC-type to opaque-type chopper design. A detailed temperature map was made of a matte-black flat plate, in the region downstream (--2D to +26D ) of two single cylindrical jets with injection angles of alpha = 30° and 90° and L/D ratios of 6. Imaging took place through a zinc sulphide window. The sampling rate was up to 20 frames per second and 50 frames were averaged prior to analysis to reduce random noise error. Calibration was made specific to each image. Many of the camera's peculiarities were addressed and compensating techniques were developed. A cold flow image subtraction technique was used successfully to reduce the effects of reflection, detector array variability, and plate surface inconsistency. Computer imaging software and calibration were used to convert the 8-bit thermal imager output to temperature and cooling effectiveness plots. It was shown statistically and in practice that this method of infrared sensing provided a detailed temperature map with an uncertainty estimate as small as +/-0.9°C. The thermal imaging system developed compared favourably with previous experimental work involving infrared temperature measurements. With this technique would be possible to conduct film cooling and effusion cooling effectiveness studies with immediately visible results and a high degree of accuracy and resolution.