Image Analysis Investigations On Structures And Velocity Field Of Liquid Jets In A Supersonic Crossflow

Hypersonic vehicle in the offensive and defensive system is with advantages of flexible,rapid response,difficult to guard against,etc.So,there is a huge military value and potential economic value.Development of hypersonic vehicle largely depends on the technological level of scramjet engine.Because of the fast speed of flow in scramjet combustor,only millisecond the fuel stays in scramjet combustor.If we want to increase the combustion efficiency to the greatest extent,it is necessary to master the changes of the parameters in the fuel atomization process.In this paper,the author researches structures and velocity field of liquid jet atomization in a supersonic crossflow by means of image analysis.It mainly includes the outline analysis,density distribution of jet and velocity filed analysis.At first,this paper introduces the supersonic flow technology and measuring methods,according to the mechanism of liquid jets in a supersonic crossflow proposing measurement requirements,and then summarizes the image analysis in the application of supersonic flow measurement.This paper proposes three-step approach to extract outline,which are image enhancement,image segmentation and edge extraction.Based on different image features,this paper enhances four-group jet images in spatial or frequency domain.Then,segmenting images based on the image enhanced,where using guided filtering on one-group images gets a better result.Finally,compares the results of different extraction methods,coming to a conclusion that extraction with Canny is better than direct extraction smoothness.On density distribution,this paper takes images correction before computing grayscale distribution.Due to different exposure between two frames and uneven distribution of laser energy,it's necessary to correct images to erase uneven illumination.This paper using linear fitting correction and histogram specification,eliminates uneven illumination effect between the two frames basically.Finally,obtains relative relationship of fluid density from distribution of gray.PIV and optical flow are useful methods of flow velocity measurement.In this paper,the author summarizes the common flow velocity measuring method,writing programs to estimate flow velocity based on simulation frames.At the same time,this paper analyses the application of physical constraints in image Velocimetry,estimating velocity with simulation frames,analyzing deviation of results.Finally,this paper estimates jet flow frame with different methods,and analyze results qualitative.This paper using image analysis method processes fluid atomization according to different mission requirements,getting the results in conformity with mission requirements,what has far-reaching significance on investigation of jet atomization.