| With the strengthening of my country's comprehensive national strength,the government has made great efforts to improve various infrastructures,and the demand for dangerous goods is also increasing.According to statistics in 2011,there are nearly200,000 vehicles for various dangerous goods transportation and more than 600,000 employees.Such items often have special properties such as inflammable and explosive,so higher requirements should be put forward for this kind of transport vehicles.At the same time,due to the rapid increase in the number of vehicles,noise pollution has gradually become a hot issue.So far,there have been many studies on the flow field,structural performance and acoustic performance of vehicle exhaust systems,but the results of coupling studies are slightly less.This paper selects the exhaust muffler of a special vehicle as the research object.Firstly,a three-dimensional model of the muffler was established based on physical measurements.After dividing the fluid mesh,the fluid analysis was performed.The internal flow field and temperature field of the muffler under three working conditions were calculated.The correctness of the simulation results was verified through experiments.The results showed that the average The deviation does not exceed 6.5%.The analysis results are as follows: the temperature field distribution is similar under the three working conditions,the exhaust gas temperature and the muffler shell temperature are higher under the medium-speed and high-speed working conditions,and their values exceed the regulations of GB 13365-2005,and the cooling performance needs to be improved.Then,divide the structural grid and the acoustic grid,and use the numerical results obtained from the CFD analysis as the boundary to solve the structural mode of the muffler.The analysis results are as follows: the temperature load has an effect on the structural mode,the frequency value is reduced,and the mode shape The characteristics have little effect.The maximum deformation of the side of the expansion cavity at the outlet end of the muffler is 60.788 mm,which is the weak position of the muffler;the dynamic performance is good,and it will not resonate with the engine excitation and the road excitation.Taking the temperature field as the boundary condition,the transmission loss of the muffler under the influence of temperature load is calculated.The analysis result shows that under the influence of temperature,the noise reduction value in the low frequency range is reduced by 2?3 d B on average,the middle frequency range changes little,and the high frequency range value increases.,About 23 d B.Secondly,an acoustic-structure coupling system is established,and the structural performance under the interaction between the acoustic cavity and the structure is analyzed.The analysis results are as follows: the first 3 orders have little change,and the4-8th mode frequencies are reduced,indicating that the air in the coupling system is opposite to the The mode shape characteristics dominated by structural deformation have little effect,but the maximum deformation of each order is increased,and the average value is 0.6 mm.Finally,optimize the design of the muffler,install a cooling water jacket outside the expansion cavity of the muffler,determine the width of the cooling water tank to be 6 mm,the flow rate of cooling water to be 0.6 m/s,and thicken the muffler shell by 1mm through analysis of variant variables.After optimization,simulation calculations show that the average outlet temperature of the high-speed operating conditions that needs improvement is 257.03°C,a drop of 24.68%;the maximum temperature of the shell is 128.74°C,a drop of 39.75%;the maximum deformation of the weak point of the shell is reduced by 21%.After optimization,the safety of the dangerous goods transport vehicle is effectively improved. |
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