| With the development of social,cars have gradually become the main means of transport,which is easy to increase traffic accidents.Nowadays,people pay more attention to the performance of the vehicle’s safety,especially to the safety of the vehicle configuration ABS(Anti-lock Braking System).Automobile ABS is an essential configuration of almost every car.And the quality of the ABS brake fluid is in relationship to the automobile braking efficiency.In some cases the ABS brake fluid is easy to produce gas-liquid two phase flow phenomenon,which will influence the propagation characteristics of the pressure wave,thus will affect automobile brake system security.This article mainly researches and analyses the characteristic of pressure wave of gas-liquid two phase flow in Automobile ABS brake fluid.(1)There are many causes to make the brake fluid produce bubbles,including the temperature of environmental,braking process to generate heat,absorbent,dissolved air,wave born bubbles and so on.The consequences of gas-liquid two phase flow in brake fluid are: the brake fluid pressure waves delays and attenuation phenomenon,thus leading to a lack of automotive brake force and delay.Then use the visualization device to carry out verification about bubbles form on bake disc at different speed in brake lines.(2)The experiment on a santana 3000 type ABS experimental bench,collect the brake pressure data under different brake disk rotational speed,brake pipe length and braking time.Research and analysis the brake fluid gas liquid two phase flow phenomenon on the impact of brake pressure,under different working conditions.(3)Using the principle of cross-correlation to calculate the velocity of brake pressure data from different brake disc rotating speed of 300r/min,400r/min and500r/min.Before brake fluid exhausts,the pressure wave velocity is between72.2m/s~162.5m/s.After brake fluid exhausts,the pressure wave velocity is between755.8m/s~1181.8m/s.And under the same condition,the faster the brake disc runs,the less bubble produces,and the wave velocity of the brake fluid pressure wave is faster too.Visualization research shows: when the speed of brake disc is becoming faster,it can bring out less bubbles which size is of several tens of microns in brakepipe and less impact on the brake pressure waves,therefore,the brake pressure wave velocity is faster.(4)The HHT principle is used to deal with the noise of data,which aquired from the conditions of different rotating speed of brake disc,different brake pipe length and different braking time.Then use the imf component of characteristic vector and energy spectrum to analysis the brake pressure attenuation degree.Study concluded that under the same conditions,the slower the speed of brake disc is,the longer the length of the brake lines are,the longer the braking time is,the more air bubbles it has in the brake fluid,the more obvious the fluctuations of imf components of the braking pressure signal and energy points sparse in the low frequency,the energy loss is large,the degree of attenuation of the brake fluid pressure waves is also evident. |
