An Axisymmetric Temperature Field Reconstruction Method Based on the Fan-Shaped Light Path Background Oriented Schlieren Method

As a condition monitoring parameter, the temperature field has a wide range of applications in the field of combustion measurement. As an effective method for noncontact measurement of axisymmetric temperature fields, the traditional background oriented schlieren (BOS) method has a problem of inaccurate calculation of light deflection angles due to the near-optical axis assumption. In this article, the Fan-shaped light path background oriented schlieren (FLBOS) method is introduced into the calculation of the light deflection angle to achieve an accurate reconstruction of the axisymmetric temperature field. First, the offset created by the background scatter across the nonuniform temperature field is measured visually which is used to solve for the light deflection angle based on this offset in the fan light path model. Then the distribution of the spatial refractive index field is solved by the Abel inversion method, which in turn gives the distribution of the spatial temperature field. Finally, the method is verified by simulated experiments on the accuracy and validity of the FLBOS. The experimental results show that the temperature field reconstruction error using FLBOS is decreased by 2.5 percent compared to the conventional BOS and it is applicable to the measurement of a wide range of temperature fields.