Test Method Of Flow Field In Hydrodynamic Torque Converter Based On Particle Image Velocimetry

The external performances of the hydrodynamic torque converter depend on its internal flow field structure, and the internal flow is a complex three-dimensional viscous unstable turbulent flow. Currently, studies on the internal flow field of the hydrodynamic torque converter are based on CFD numerical simulation, however, there are some errors in the numerical simulation, it is necessary to use the experimental methods to understand the real flow situations inside the hydrodynamic torque converter. Not only can the test measures for the flow field of the hydrodynamic torque converter help improve their blades and runner structure, and then enhance the performances of the torque converter, but also can be used to guide the CFD numerical simulation, and then verify its accuracy. Therefore, the research on test method of flow field in hydrodynamic torque converter based on particle image velocimetry has important practical significance and applied value. Based on the particle image velocimetry, this paper studied on test methods of the hydrodynamic torque converter flow field. The main research work and conclusions are as follows:1. PIV test and flow image collection of hydrodynamic torque converterThe principle of the torque converter particle image velocimetry was introduced. PIV is a full flow field velocimetry technique, its application within the internal flow filed measurement of the hydrodynamic torque converter can objectively reflect the real situations of the internal flow field of the hydrodynamic, it has high accuracies and reliabilities. PIV flow image acquisition method of hydrodynamic torque converter was researched, the technology roadmap of the hydrodynamic PIV flow field test was developed. Firstly, the transparent prototype of the hydrodynamic torque converter was produced by the 1:1 ratio, then the test platform was set up and debugged, and finally the test experiments of the hydrodynamic torque converter flow field were performed to collect flow images. According to the technology roadmap developed, flow filed particle images of the pump and turbine were collected respectively when YJ220 hydrodynamic torque converter was at i=0, i=0.3, i=0.5 and i=0.7.2. Research on PIV flow image influencing factors of hydrodynamic torque converterThe hydrodynamic torque converter PIV test platform mainly consists of the test prototype, mechanical section, optical section and the image collection part, some key factors of these have great influences on the collection effects of the flow images. The influences the test prototype, lighting, image collection system, tracer particles and the impeller speed have on the image acquisition results was analyzed, which has guiding significances for choosing the appropriate test parameters, improving test precisions and accuracies. The test prototype should try to improve its transparency and reduce the reflective sheet of the prototype by adjusting the angle of incidence of the light source; lighting should choose the laser which has the higher brightness and directionality, and the thickness of the sheet of light should be about 1mm by designing the appropriate optical path. The lens focal length, aperture, angle of view, depth of field and the resolution, exposure time and frame rate of CCD camera need to be chose according to the test site conditions in the image collection system. The following behaviors, scattering nature, spread uniformity and concentration of tracer particles also have important influences on the test effects. We should try to choose the tracer particles which have good following behaviors and scattering nature, and make sure the spread uniformity and concentration are right. This paper chose aluminum whose diameter is 5～10μm as tracer particles and medium particle concentration (there are 4-8 particles in each query window). The increasing of impeller speed impacts the correlation of particle images, and reduces the effective area of the flow field. In this condition, we should increase the camera frame rate to shorten the time interval between two consecutive frame images.3. Method research on flow image processing and flow parameter extraction of hydrodynamic torque converterThe method research on flow image processing and flow parameter extraction of hydrodynamic torque converter was done. The image was calibrated using the outer calibration method calibrated by the calibration plate, and then the calibration scale was got as 0.2143mm/pixel. Then, the research on particle image preprocessing method was done, Graying, brightness enhancement, contrast enhancement and Laplace filtering were applied to further enhance image signal-to-noise ratio. FFT and three-point Gaussian fitting used to optimize the cross-correlation algorithm based on the gray distribution function, the velocity field and vorticity field distribution graphs of the pumps and turbines were acquired when the application example of YJ220 hydrodynamic torque converter is at i=0, i=0.3, i=0.5 and i=0.7 respectively, and the results were analyzed. The research results showed that test method of flow field in hydrodynamic torque converter based on particle image velocimetry of this paper had higher test accuracy compared with the existing test method in the domestic and overseas.