| In recent years,a lot of new technologies have been applied to diesel engine.The strengthening degree of diesel engine is higher than ever,which makes the mechanical load and heat load of diesel engine increase continuously.As one of the core components of diesel engine,piston bears very high heat load,so it is necessary to take cooling measures for piston.In this paper,based on the visualization experiment,the flow pattern of the fluid in the piston inner cooling cavity of high power diesel engine is studied,and the motion law of the fluid under oscillating cooling situation is revealed.The main contents and corresponding conclusions are as follows:A piston oscillating cooling test-bed named ZD270 was designed and built,which is similar to a single cylinder diesel engine.According to the measuring and controlling requirements of the test-bed,the corresponding functions were developed on STM32 single chip microcomputer and esp-8266 module.Based on the u C/OS-III real-time operating system,the tasks of ADC reading,pulse period measurement,camera triggering by angle and serial port sending were completed.The data are collected and sent to the upper computer through WLAN,and the high-speed camera is triggered according to the command of the upper computer by the crankshaft angle.The communication software is developed by Lab VIEW on the upper computer to display and save the data.The images are processed by MATLAB.The boundary of oil chamber is extracted based on Canny operator,and all images are calibrated to the coordinate system of oil chamber.The gas phase and liquid phase are divided by Labelme.According to the boundary between gas phase and liquid phase,the area of gas phase is calculated by Image Pro Plus,and the central point of whole gas phase is calculated.Based on SIFT algorithm,the feature points of the image are extracted,and the similarity of the image sequence is calculated according to the matching of the feature points,which is used to measure the intensity of the gas-liquid oscillating flow.According to all kinds of information extracted from the images,the influence of motor speed and oil inlet pressure on the distribution of gas-liquid phase is analyzed.The change of filling rate of outer oil cavity under different working conditions is studied,and the situation of gas phase breaking and polymerization is analyzed.The law of gas-liquid phase motion of oscillating motion is summarized,and the influence of motor speed and inlet pressure on the flow intensity between gas and liquid is studied,which makes inner cooling oil cavity structure optimized better. |
