| The hydraulic brake system is an important structure of automobile.It has the function of exerting braking force on auto wheels,which gives brake force to automobile in order to slow down or stop automobile.The hydraulic brake system can control braking velocity so as to keep vehicle stable and protect the car,then the traffic accidents can be reduced.With the influence of the external environment,the brake oil that in hydraulic pipeline can easily become gas-liquid two-phase flow.But the gas-liquid two-phase flow has effect on the operating of the hydraulic brake system,which damage the device.As a consequence,the hydraulic braking system gradually out of control,even cause accidents.However,there were seldom research on the gas-liquid twophase flow in hydraulic pipeline both domestic and overseas,so this article did a great deal of research on the gas-liquid two-phase flow in hydraulic pipeline.This article adopted a method to identify the gas-liquid two-phase flow patterns in hydraulic pipeline,which based on digital image processing technology and cluster analysis.In addition,some researches also have done to calculate the void friction of brake oil when it was gas-liquid two-phase flow.Some results have been achieved and shown as below:(1)An experimental system of automobile hydraulic brake system was designed and set up.The pictures of gas-liquid two-phase flow patterns were taken by this experiment system,from which four kinds of typical flow patterns were found,they are: bubble flow,plug flow,slug flow and annular flow.(2)A method that suitable for the identification of the gas-liquid two-phase flow patterns in automobile hydraulic brake system was adopted.This method included two subsets,in the first subset pictures of flow patterns were processed by the image processing technology,and these pictures were identified by cluster analysis in the second subset.In the first subset,the feature parameters of flow patterns images were extracted by methods basing on gray level co-occurrence matrix,two-dimensional wavelet transform and Zernike moments.The study found that these methods have a good effect on extracting the feature parameters of the flow patterns images,the feature parameters are highly discriminable,which good for further processing.Moreover,these methods will provide a new way of processing the flow patterns images.In the second subset,three types of cluster analysis were used to identify the images of flow patterns,which include hierarchical cluster analysis,K-means cluster analysis and fuzzy c-means clustering analysis.The characteristic parameters of flow patterns images were the original data of cluster analysis.The total correct identification rate of every cluster analysis was high,which up to 95.625%,98% and 97%,besides,the identification rate of the single flow pattern closed to 100%.So it can be concluded that the method have outstanding effect to identify the flow patterns of gas-liquid two-phase flow in the automobile hydraulic pipeline.(3)A new way that based on the digital image processing technology was used to calculate the void friction of brake oil in automobile brake pipeline.This method focused on the bubble flow,during the processing,some skills were used in sequences including image filtering,contrast adjustment,image segmentation,edge detection,image padding,image tagging and so on.After the processing,the characteristic parameters of bubble flow images could be extracted as the essential condtions to construct mathematics model with the void friction,then the void friction of braking oil could be calculated by the mathematics model.Finally,the variation law of void friction of braking oil,vehicle speed and braking force can be analyzed that the vehicle speed is proportional to the braking force,and the braking force increased with the improvement of the vehicle speed,so the void friction of the brake oil in braking pipeline changed with the increasing of the vehicle speed.Besides that the variation trend of the void friction decreasing when the vehicle speed increasing and it shocked in stages.The results give a new theoretical foundation to the research of automobile hydraulic braking system and a new path to research the gas-liquid two-phase flow. |
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