Studies Of New Method Of Heat Flux Testing Of The Optical Window In Imaging-guiding

In the studies of aerodynamic heating and thermal protection of the supersonic and hypersonic vehicle, the heat flux is one of the important measurement parameters. After decades of development, the heat sensor testing methods and heat map technology are already used to measure the heat flux. This article was firstly put forward a new method for measuring surface heat flux of the optical window, which is a new technique based on Background Oriented Schlieren. BOS is a measurement technique for flow visualization, it used for the principle that refrection will occurs when the light throughs a field of variable refractive index. By using the cross-correlation algorithm of digital images the deflection displacement of light can be analyzed and calculated.The critical idea of the new method of BOS-HF system proposed in this paper firstly, is to construct a quantitative relationship between the displacement of BOS background image and the surface heat flux of the optical window. So the surface heat flux of optical window can be measured by the mean of non-contact and high-precision measurements. Theoretical priciple of the new method of BOS-HF system is demonstrated rigorously. The result of the study indicates that the new method of BOS-HF system is feasible.A series of experiments were conducted about the model of optical window whose cross-sectional dimension is 120mm×200mm and it has a thickness of 15 mm, and another model is the 2-dimentional optical hood. Schlieren technique and the BOS-HF testing technique were used to study the experiment of optical window. But for the 2-dimentional optical hood, not only the BOS-HF testing technique was used, but also heat-sensor measurement system was used. a comparative analysis of the experimental results shows that, the BOS-HF testing new method which could be applied for the heat flux measurements of model surface is feasible and it has a good prospect.