An accurate temperature field reconstruction method based on multi-physics decoupling with schlieren imaging

Abstract

Abstract The tail jet field’s temperature distribution of aircraft engines is of great significance to reflect the combustion efficiency and the formation mechanism of pollutants. The traditional temperature sensor measurement method has a series of shortcomings such as single point measurement, destruction of the flow field and poor spatial and temporal resolution, so it is not suitable for the application scenarios of the tail jet temperature field measurement. Schlieren method, as a visual measurement technology of flow field, is an effective method for real-time measurement of flow field parameters, with the characteristics of large measuring range, fast response speed and simple testing equipment. In order to improve the accuracy of the traditional schlieren method, this paper presents a temperature field distribution reconstruction method by decoupling flow velocity and density field, considering the influence of flow field velocity, density and other factors on temperature field. Firstly, the light deflection angle of the schlieren image is obtained by the change of brightness and darkness in the picture, and then the density distribution of the flow field is obtained indirectly. Then, through the schlieren images of continuous frames, the flow velocity distribution is obtained by using the optical flow velocity measurement algorithm. After that, the obtained density and velocity information can be used to calculate the pressure distribution of the flow field. Finally, the temperature distribution of the flow field can be obtained by using the obtained flow velocity, density and pressure information through the numerical calculation of the energy equation. The experimental results show that the maximum deviation of this method is about 5% compared with that of thermocouple measurement. Therefore, the method proposed in this paper can accurately reconstruct the temperature distribution of high temperature and high speed flow field, and effectively expand the application range of schlieren method in the quantitative measurement of flow field.