| With the development of science and technology and the increasing emphasis on environmental protection requirements,national regulations will have stricter and stricter requirements for noise control that affect public health and the living environment.The installation of exhaust mufflers is the most realistic and effective noise reduction method for internal combustion engine related products.The development of resistant mufflers with good silencing performance and low exhaust back pressure to reduce the noise of mechanical equipment is not only conducive to improving the living and working environment,but also in line with national and national regulations.Industry requirements.In this paper,without changing the structural unit of the single muffler,the exhaust muffler of a gasoline engine is taken as the research object,and the acoustic test and the performance simulation analysis of the sound field and flow field are carried out on it.The parallel connection of the muffler unit is proposed,and the LMS Virtual.Lab is used.The simulation with computational fluid dynamics software Fluent explored the muffling performance of the muffler of the parallel muffler unit and the speed and pressure changes of the internal flow field,revealing the influence of various parameters on the transmission loss and pressure loss of the overall muffler of the parallel muffler unit.Through acoustic tests and acoustic finite element analysis,the overall muffler of parallel muffler units can effectively increase the transmission loss and reduce pressure loss compared with the single muffler unit muffler.Although it does not have the high level of sound attenuation of the tandem muffler unit muffler,it has a higher level of sound attenuation.Low pressure loss is more suitable for use in scenes that are sensitive to pressure loss.The influence of the transmission loss and pressure loss characteristics of the overall muffler of the parallel muffler unit under the conditions of no flow and flow is preliminary studied,and it is found that t The flow velocity has a certain influence on the transmission loss in the middle and high frequency band of the whole muffler with parallel silencing units.The pressure loss increases with the increase of the flow velocity at the inlet end and is proportional to the square of the flow velocity.The pressure loss increase of the overall muffler of the series muffler unit is much greater than that of the parallel muffler unit.The overall muffler of the parallel muffler unit has a short air inlet pipe combined with a branch outlet,a middle air inlet pipe combined with a branch outlet,a long air inlet pipe combined with a branch outlet,and a long pipe at the inlet and outlet and a short pipe at the inlet and outlet.The five different parallel connection methods of tube junction,air inlet and outlet,etc.,middle tube junction,etc.,are preliminarily discussed for the transmission loss and pressure loss of the overall muffler of these five parallel muffler units.The transmission is caused by the length of the pipeline and the combined and split flow of the inlet and outlet pipes.Differences in loss curve changes and differences in aerodynamic performance.The shunt state of the outlet pipe can bring a lower pressure loss gain.Increasing the number of connecting pipe partitions can significantly increase the pressure loss,but too many connecting pipe partitions will not increase its pressure loss;as the angle between the connecting pipe partition and the connecting pipe axis increases,the pressure loss will slow down.Larger;reasonable connecting pipe diaphragm aperture is beneficial to reduce pressure loss,while the existence of connecting pipe diaphragm has little effect on the transmission loss of parallel muffler units.Changing the length of the connecting pipe can control the formation of sub-wave peaks and effectively control the narrow-band noise without causing significant pressure loss changes.The research results provided the reference and guidance function for the design and application of muffler with parallel muffler units. |
