Analysis On Acoustic And Aerodynamic Performance Of Special-shaped Split-stream Rushing Exhaust Muffler Unit

The exhaust noise of diesel engine is the most serious,and installing the exhaust muffler is the most direct and effective method to reduce the exhaust noise of diesel engine.The exhaust muffler uses the resistant muffler more often.The most important parameter affecting its performance is the airflow speed in the muffler.For example,the regeneration noise of the muffler is approximately proportional to the airflow velocity in six times,while the exhaust pressure loss is proportional to the square of the flow rate.The research group proposed the principle of split-stream rushing to reduce the airflow velocity,so as to improve the comprehensive performance of the muffler.Based on the previous research of the research group,the acoustic and aerodynamic performance of the special-shaped split-stream rushing exhaust muffler unit were studied,and the work done and the conclusions obtained are as follows:With the CG25 single-cylinder diesel engine as the prototype,Three different ratios of axial ratio(1,1.3,1.6),two opening directions(elliptical long axis or short axis)(a total of 13 muffler units,Where a circular muffler unit is regarded as an oval muffler unit with a axis ratio of 1)of the transmission loss curve within 1-3000 Hz,Observing its noise elimination characteristics at different frequencies,the transmission loss curve trend is essentially the same,The mean value was taken for comparison,We conclude that the narrower the distance between the inner and outer cavity at the opening,the higher the mean insertion loss;At the same time,the aerodynamic performance of 13 muffler units was simulated and calculated,Taking the mean of pressure loss,The aerodynamic performance is further analyzed with the help of the velocity cloud map.The results show that the transition arc between the inlet tube and the cone-shaped split-stream tube can effectively reduce the pressure loss;the narrow distance between the inner and outer cavity walls can cause the pressure loss to rise;When the airflow pressure at the opening is too small and the hedge distance is relatively far,the airflow is dispersed to the sides and the effect of deceleration by hedging the airflow is worse,the air velocity of the inner cavity is larger,the vortex area moves more sharply,the vortex dissipation increases,and the partial pressure loss rises;When the distance between the inner and outer cavity at the opening is too narrow,it can lead to a sharp increase in pressure loss.Finally,the oval muffler unit with the best acoustic performance,the oval muffler unit with the best comprehensive performance and the circular muffler unit were selected to process the actual product,the pressure loss of the three mufflers was also compared and analyzed through the bench text,the insertion loss of the three mufflers was compared and studied through the real car test,and the feasibility of the oval deformation was proved on the split-stream rushing exhaust muffler structure.