Development of an Automated Calibration System for Pressure and Temperature Sensitive Paints

摘要

Global surface measurements using pressure or temperature sensitive paints in wind tunnel testingrequires some prior knowledge of the paint performance characteristics. Paint formulations can varyfrom one test to another or test conditions can change, resulting in a need to calibrate the paint in acontrolled environment usually before the test is completed. While the most common technique ofcalibrating the paints is by the in-situ method, where pressure taps on the model are used, there may betests where this is not possible. Laboratory or a priori calibrations must then be performed on the paint.At the NASA Langley Research Center, a pressure and temperature controlled test chamber has beenbuilt to calibrate the paints over a temperature range of –150°C to 100°C and a pressure range from nearvacuum to as high as 150 psi. In order to simplify the data acquisition during the calibration, the processwas automated such that the operator can input the desired temperature and pressure test points and thenlet the system run without operator intervention. Included in the capability is an enclosed light booth,that allows other tests to be conducted in the laboratory without interfering with the calibration process.All components of the system, including the image acquisition camera are controlled using in-housedeveloped software. A description of the system hardware, software, and overall operation will beprovided. Some examples of pressure and temperature sensitive paint calibrations will also be given.The calibration system has become an integral part of the pressure and temperature sensitive paintresearch effort at the NASA Langley Research Center.