The Acoustic Performance Research On Internal Combustion Forklift Exhaust Muffler With The Consideration Of Air Flow And Medium Temperature

The complex flow field and temperature field inside muffler will appear,when high flow velocity and high temperature air flow that internal-combustion engine exhaust enters into the muffler.The velocity and temperature of air flow vary with positions in muffler,which will affect the propagation rules of sound waves inside muffler and the acoustics performance of muffler.To accurately analyze the acoustics performance of muffler,it is needed to consider the factors of air-flow and medium temperature.However,the flow field and temperature field in muffler is usually simplified into constant or uniform flow,the linear gradient temperature in current research,which will cause greatly errors.The paper regard a certain internal-combustion forklift exhaust muffler as a research object,and research on the acoustic performance considering the influence of air-flow and medium temperature.The main working contents are as follows:(1)Based on the theories of flow field,fluent software was used to simulate exhaust muffler internal fluid flow and heat transfer,and calculate velocity field and temperature field inside exhaust muffler under the conditions of the idle speed and high speed of engine.(2)The heat transfer boundary conditions calculated by fluent software were applied to the calculation of steady state temperature field in exhaust muffler,and the muffler shell temperature distribution was gained by using the steady-state thermal analysis module of ansys workbench.It can indirectly verify the correctness of the internal flow field simulation analysis of exhaust muffler by comparing the results of simulation and test.(3)According to the analysis results of velocity field and temperature field in exhaust muffler,acoustic simulation software was used to calculate the transmission loss.The transmission loss curves gained were contrast to the transmission loss curve of the exhaust muffler under the condition of atmospheric pressure,so that analyze acoustics performance of exhaust muffler considering the influence of air-flow and medium temperature.(4)Based on the acoustics simulation results,the exhaust muffler was improved and simulated.The compare of transmission loss curve of pre and post improvement of exhaust muffler,indicating that the transmission loss of the improved exhaust muffler is higher than the original exhaust muffler in the most frequency bands,and the silencing effect of muffler is developed.(5)The exhaust noise of the internal-combustion forklift was tested,and the A sound pressure level and frequency spectrum of the exhaust noise when the forklift was equipped with the improved and original exhaust muffler at the idle speed and high speed condition were gained.The test results verify that the improvement of the exhaust muffler is effective,and show the importance of considering the influence of air-flow and medium temperature when the acoustics simulation analysis of the exhaust muffler is carried out.