Research On Measurement Of Temperature Field Distribution Based On Schlieren Method

In this paper,the measuring principle and method of schlieren quantitative measurement technology are mainly introduced.Meanwhile,application of this technology in the field of flame combustion and temperature measurement is discussed in detail.This paper also analyses the difficulties and key points of schlieren technology in quantitative measurement.A novel quantitative measurement method is proposed to reconstruct the temperature field of the flame,and the study of the temperature field generated by alcohol lamp flame is discussed in this paper.In order to reconstruct the field of temperature,the traditional schlieren quantitative measurement method is combined with the Abel inversion and the calibration schlieren method.An uncomplicated method for quantitative measurement of temperature field is designed,and the difficulty of the method is to obtain the deflection angle when the light passes through the nonuniform temperature field.Focusing on this problem,a calibration curve is made by using the calibration schlieren method to draw the relationship between the angle of light deflection and the gray value of the schlieren image.The deflection angle of light can be obtained by the calibration curve.Then the refractive index distribution on a certain section is acquired by using the Abel inversion.According to Gladstone-Dale's law and gas state equation,the distribution of temperature field on the section is calculated.Finally,the temperature values measured by the schlieren system are compared with the measured values of the thermocouple,and the distribution of temperature field is in agreement with the actual distribution.An experimental device for schlieren temperature measurement is designed.The light source of schlieren system is optimized by increasing the lens to improve the uniformity of thelight source.At the same time,the main lens in the schlieren system has been designed aimed at eliminating the spherical aberration and dispersion and improving the spatial resolution of the main lens.A transmission schlieren system was built on the optical platform to measure the axisymmetric temperature field produced by the alcohol lamp.And the measurement results of the schlieren system are compared with the measured values of the thermocouple.The experimental results show that when the room temperature is 20℃,the relative error of the schlieren quantitative measurement technology is less than 5%,and the experimental results meet the requirement.The research content of this paper provides a certain reference value for the quantitative measurement of flow field.