Research On The Structure Resistance Characteristics Of Resistant Exhaust Muffler

The acoustic performance and aerodynamic performance of the resistant muffler are mutually restricted,and the passability of high-frequency sound waves and low-frequency sound waves is different.The passability of high-frequency sound waves in lower frequency bands is worse,and high-frequency failure is prone to occur for mufflers.Phenomenon,so how to balance the contradiction when designing the muffler is of great significance;in the actual use process of the muffler,the actual effect is often worse than the theoretical effect.This is because the muffler itself produces aerodynamic noise and structural radiation noise.The internal structure of the muffler is complex and the overall sound attenuation has been increased.However,with the increase of airflow speed,the aerodynamic noise and structural radiation noise generated by the muffler also increase rapidly.The muffler itself may also become a new noise source,so explore the difference of the muffler The relationship between the acoustic performance and aerodynamic performance of the structure and the aerodynamic noise generated by the structure has a certain guiding effect on engineering practice.First of all,this paper gives the muffler principle of different muffler units under different theories,and carries out the simulation verification of single expansion muffler and single internal intubation muffler;the calculation of muffler pressure loss is divided into the traditional semi empirical formula method and the commonly used computational fluid dynamics(CFD)method,this paper briefly introduces its principle and gives the measures to reduce the pressure loss in structure measures.Secondly,in order to reduce the pressure loss of the muffler,CFD method is used to analyze the pressure loss of different structures of the guide pipe.The results show that the transition elbow structure has not only good aerodynamic performance,but also good noise attenuation performance.Combined with different forms of guide pipe,the transfer loss of the offset expansion muffler,the side branch expansion muffler and the return expansion muffler are analyzed The results of loss analysis and pressure loss analysis show that the acoustic performance and aerodynamic performance of the muffler are improved,and the offset expansion type and the side expansion type have their corresponding equivalent structure forms in theory.Then,A muffler structure in the form of a shunt tube is proposed,and the CFD +Virtual.Lab co-simulation method is used to analyze the transmission loss,resistance loss and dipole aerodynamic noise;The results show that the muffler with shunt tube can reduce the pressure loss,but its acoustic performance is reduced due to the reduction of the expansion ratio of the outlet section.At the same time,the internal structure of the muffler is complex due to the splitter tube,which causes the noise of the muffler itself,The dipole aerodynamic noise also increases sharply.Finally,several typical exhaust muffler structures of medium power and high power diesel engines are analyzed,and combined with perforated pipe muffler and shunt pipe muffler,the pressure loss is optimized;the optimized muffler pressure loss is lower than the typical structure of double cavity and three cavity muffler,but the noise reduction is between the two cavities.