| With the continuous growth of China’s economic aggregate and the rapid development of the logistics and transportation industry,the demand for transportation of dangerous chemicals is increasing in the market,and more than 95% of them are involved in long-distance transportation of vehicles.Due to the special properties of dangerous chemicals such as flammable,explosive and corrosive,the dangerous goods transport vehicle during driving can be regarded as a dangerous source of movement.The flow and temperature of the combustion exhaust gas in the vehicle exhaust system are the main risk factors.It is of practical significance to study the flow field and temperature field of the combustion exhaust gas in the exhaust system of dangerous goods transport vehicles.There are many studies on the thermal load,internal flow field,temperature field and structural dynamic performance of the exhaust system of ordinary vehicles,but there are few research literatures and results on the safety of special vehicles for dangerous goods transportation and the cooling performance of exhaust systems.Ordinary exhaust system devices do not meet the special requirements of the dangerous goods transport vehicle for the exhaust system.In this paper,the exhaust system of a dangerous goods transport vehicle is taken as the research object.The Fluent software is used to study the internal flow field and temperature field of the exhaust muffler of the exhaust system.With the result used as the boundary condition,the ANSYS/Modal module is used to perform constrained modal analysis on the muffler.Finally,the structure of the muffler is optimized according to the above research results,and the optimized muffler is verified by numerically simulation.Firstly,the assembly structure of the exhaust system is analyzed.For exhaust muffler,a three-dimensional model is built by Creo3.0,watershed extraction is carried out by ANSYS/DM and meshing is done by ANSYS/ICEM.By calculating the average temperature of the outlet of the muffler,it is known that the average temperature of the outlet is higher under normal speed and high speed working conditions,and the cooling performance of the muffler needs to be improved.Through the analysis of the flow field and temperature field in the muffler,there are vortex zones in the left and right sides of the muffler cylinder under the three working conditions.The maximum temperature of the outer surface of the muffler shell is greater than the requirement of the national standard.The test of the outer surface of the muffler shell shows that the error between the test temperature value and the numerical analysis value is within 10.56%.However,the trend of the two changes is consistent,which indirectly verifies the credibility of numerical analysis.Secondly,the ANSYS/Modal module is used to analyze the structural modality of the muffler under temperature load.By analyzing the natural frequencies of the muffler under three working conditions,it is known that the temperature load has a greater influence on the lower-order mode and less influence on the higher-order mode.Compared with the external excitation frequency,the muffler does not resonate,and the structural dynamic performance is available.However,the vibration deformation of the left side of the muffler cylinder is up to 73.542 mm,it is a harmful vibration mode which means it is a weak position.Finally,the structure of the muffler is optimized aiming for solving the above problems.The cooling water jacket is added to the outer wall of the muffler and the left and right sides of the cylinder are thickened by 1 mm to obtain two types of muffler A and B.The numerical simulation of the two types of muffler A and B shows that the B-type muffler has the best cooling performance when the cooling water flow rate is 0.8m/s,the maximum outlet temperature is 192.902°C,and the vibration deformation of the left side of the muffler cylinder also dropped by 18.70%.Therefore,the optimized B-type muffler effectively enhanced the cooling and structural dynamics. |
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