Research On The Muffling Characteristics Of Double Exhaust Muffler In Light Truck

Exhaust muffler is the main tool to reduce engine exhaust noise,and the core work of the exhaust noise control project is structural optimization.The current muffler is generally designed as a single row structure,due to the limited space at the bottom of the car also further limits the size of the muffler in the structural improvement;On the other hand,as the noise limit for light trucks is getting lower and lower,no matter what improvements are made in light trucks with single-row mufflers,the control effect on exhaust noise is no longer significant,the control effect of the exhaust noise is not obvious enough to Light trucks meet noise limits.Therefore,under the permission of the bottom of the light truck,the study of double-row muffler is imminent.In this paper,HT01001-A and B are designed with two different structural mufflers,on the basis of UG and Hypermesh modeling software,ANSYS CFX platform was used to simulate the flow field of each model single and double row muffler,and the internal pressure field and velocity field distribution were obtained:The backpressure data obtained in the flow field analysis is transferred to the acoustic grid through the mapping transfer method between the grid data.The LMS Virtual.Lab acoustic software is used to obtain the transmission loss curve of the single and double row muffler;Finally,the influence of double row structure on pressure loss and acoustic performance is summarized,and the performance of different double-row muffler group under pressure and acoustic performance under the same volume condition is given.The design scheme of reducing the exhaust back pressure of the double-row structure muffler is put forward;Finally,the double-row improvement of HT01001-C impedance composite muffler is carried out.Combining with the characteristics of flow field and the acoustic performance,the feasibility of double-row improved scheme of impedance muffler is discussed.The result indicates:(1)For the HT01001-A interpolation bias muffler with simple internal structure,the increase of the pressure loss of the double-row muffler is mainly due to the intake bends.The expansion ratio has a great influence on the pressure loss,there is a critical expansion ratio and follows the change rule of expansion ratio and pressure loss in single row muffler.Compared with the single-row muffler in terms of acoustic performance,the increase in the total loss of the five groups of double-row muffler is:M=12.25 is 1%;M=12.88 is 8.5%;M=13.5 is 20%;M=14.2 is-12%;M =15 is 13.8%.(2)For the HT01001-B interpolated perforated muffler with more complex internal structure and more severe airflow,the pressure loss of the improved double-row muffler has been increased.The inlet and silencer cavities have an effect on the pressure loss.With the increase of the expansion ratio,the influence of the expansion ratio on the pressure loss is getting smaller and smaller.When the cavity length is reduced to a certain extent,the airflow velocity change in the transverse space becomes more and more obvious,leading to the increase of the pressure loss.Compared with the single-row muffler in terms of acoustic performance,the increase in the total loss of the five groups of double-row muffler is:M=12.15 is-7%;M=12.96 is-1%;M=13.8 is-14%;M=14.6 is 9%;M=15.5 does not change.(3)In the expansion of the cavity length and perforation rate and other important parameters of the same premise,increase the diameter of the import and export can significantly improve the double-row muffler pressure loss.(4)The double-row structure resulted in more severe pressure loss of the impedance composite muffler,while the total increase in transmission loss was only 3%.