Methodology for High-Accuracy Infrared Calibration in Environments with Through-Wall Heat Flux
Methodology for High-Accuracy Infrared Calibration in Environments with Through-Wall Heat Flux
复制标题
穿墙热通量环境中的高精度红外校准方法
DOI：
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
T. Povey
中科院分区：
文献类型：
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作者：
Mathias Michaud;Francesco Ornano;N. Chowdhury;T. Povey
本文介绍了一种在壁面热流和表面温度不均匀的环境中进行红外光谱精确定标的新方法。在涡轮机研究环境中，传统的现场红外校准方法依赖于嵌入表面的热电偶或使用粘结层粘合到表面。对文献的回顾指出，由于胶粘剂基材和涂料对热电偶测量的温度的影响而引起的校准中的不确定度，即在非绝热条件下(即穿壁热流)，测量的温度偏离真实的表面温度。
我们系统地研究了热电偶温度对典型的实验室红外校准装置中的安装条件的敏感性，以及在现实的穿壁热流条件下的敏感性。提出了一种新的标定技术，通过减小热电偶测量结果与红外摄像机观测到的外壁温度之间的差异，提高了标定精度。该新技术还具有另外的优点，即通过提供具有更大温度均匀度的区域，特别是在具有显著的下伏表面温度变化的环境中，减少与在红外图像中选择适当像素相关的不确定性。新方法被实验证明，并与在发动机高度代表性条件下运行的重度气膜冷却喷嘴导叶组件上的更传统的测量技术进行了比较。实验结果表明，该方法能显著提高穿壁热流和表面温度不均匀环境下红外原位定标的测量精度。
This paper describes a new method for accurate in situ infrared (IR) calibration in environments with significant through-wall heat flux and surface temperature non-uniformity. In the context of turbine research environments, conventional approaches for in situ IR calibrations rely on thermocouples embedded in the surface or bonded to the surface using an adhesive layer. A review of the literature points to lack of emphasis on the uncertainty in the calibration arising from the effect of the adhesive substrate and paint on the temperature measured by the thermocouple, namely that under diabatic conditions (i.e. with through-wall heat flux) the measured temperature deviates from the true surface temperature.
We present a systematic study of the sensitivity of the thermocouple temperature to installation conditions seen in typical laboratory IR calibration arrangements, and under realistic conditions of through-wall heat flux. A new technique is proposed that improves the calibration accuracy by reducing the difference between the thermocouple measurement and the external wall temperature seen by the infrared camera. The new technique has the additional advantage of reducing the uncertainty associated with selecting an appropriate pixel in the IR image, by providing a region with greater temperature uniformity especially in environments with significant underlying lateral surface temperature variation. The new approach is experimentally demonstrated and compared to more conventional measurement techniques on a heavily film-cooled nozzle guide vane assembly operated at highly engine-representative conditions. The proposed technique is demonstrated to significantly improve the measurement accuracy for IR in situ calibrations in environment with through-wall heat flux and surface temperature non-uniformity.