Study Of Laser Interference Paticle Imaging And Information Extraction Method

With the rapid development of the defense industry and aerospace technology,the demand for aerospace of high-performance engine to improve its maximum thrust and thrust-weight ratio is increasingly urgent.The particle size and its distribution after atomization have important influence on the performance of the engine.At present,the interferometric particle imaging(IPI)technology as a more effective and real-time measurement method for large-scale and polydisperse spray field,has become one of the most effective means of atomization particle detection,the measurement accuracy depends on the accuracy of image information extraction.The interferometric particle imaging technique irradiates a laser sheet into the particle spray field and uses a high-speed CCD camera to capture the scattered light image of the particles on the defocused surface of the imaging lens.The 0-order reflected light and the 1-order refracted light of the particle will produce interference fringes on the CCD camera,and the size of the particle can be measured by analyzing the interfering image.On the basis of the existing interferometric particle imaging measurement methods,this paper have proposed a particle interference image processing algorithm based on Morphological-Hough transform and Fourier transform.From the point of view of particle identification,the effect of information extraction is improved so as to improve the measurement accuracy.The optical path model of interferometric particle imaging measurement is established,and the influence of model parameters on interferometric particle imaging measurement results is simulated and analyzed.The feasibility of the information extraction algorithm is verified.The main contents of this paper are as follows:1.According to the principle of interferometric particle imaging measurement,the influence of the key parameters of geometrical optics model on measurement results is studied.By using the Mie scattering theory and the Debye series expansion model,the scattering characteristics of the scattered light intensity with the scattering angle are calculated,and the relation between the scattering light intensity and the particle diameter is investigated.The optical path model of interferometric particle imaging measurement technique is analyzed.Based on the geometrical optics approximation model(GOM),the formula for calculating the particle size in this technique is derived by using phase difference method and Young's interference method.The effects of incident light wavelength,scattering angle,refractive index and collector angle on the measurement results are analyzed.2.The particle center position and frequency information are extracted from the particle image of the particle field.Firstly,an interference fringe pattern recognition algorithm based on Morphological-Hough transform and a fringe frequency extraction algorithm based on Fourier transform are proposed,the improved particle interference fringe pattern recognition algorithm is used to realize the accurate identification of overlapping particles,and then to improve the particle measurement accuracy.Secondly,the basic circle and interference fringes by simulation and analysis using the two algorithms,and the correct center coordinates and fringe frequencies are obtained.Finally,the interfering particle images in different concentration particle fields are simulated by computer,and the particle fields with 10,30 and 50 particles in the field of view can be fully identified.3.An interferometric particle imaging measurement optical path is constructed,and the particle diameter of the polystyrene standard particle field with a diameter of 24?m is measured at a scattering angle of 68.96°,and the absolute error of measurement is 0.4?m.Using the CCD camera particle size measurement and the interferometric particle imaging measurement method,the atomization field of 400 m centrifugal nozzle under different pressure is measured,and the measurement results were evaluated by particle size distribution and SMD value.At three different pressure values,the two methods were used to measure the particle size at the same location,the particle size distribution and SMD value were compared and analyzed.At the same pressure,the particle size distributions obtained by the two methods are in good agreement.The difference between the corresponding SMD values is less than 2.4?m.