The Research Of Exhaust System Heat Transfer And Thermal Properties

With the rapid development of China's automobile industry, the increase in car ownership makes the noise generated affect people's daily life has become a serious problem.Therefore, control of vehicle noise, not only to comfort of travel, but also related to the protection of the environment. The engine's exhaust system to produce the noise is a major source of vehicle noise, the installation of muffler is in the most effective measures to reduce vehicle exhaust system' noise, and is the main technical measures to reduce the engine noise. With the increased power of the engine displacement increases, the muffler also increased, its structure is also more complex. As the high temperature makes the exhaust gas system's shell have a greater gradient of temperature distribution, resulting in a heat stress, under the long time action will make the exhaust system produce a thermal fatigue damage.Today, the structure and performance of muffler's design, the main focus is the exhaust noise and exhaust back pressure, the heat load on the exhaust system and thermal performance is not a lot of concern, research on the thermal fatigue carried out less.This article is based on the vehicle exhaust system design and development projects. Three programs have been designed to steady-state thermal finite element analysis, from a chosen program of its good to thermal fatigue simulation to assess the fatigue life, and Study by numerical simulation and experimental data analysis methods combined. In this article, firstly, introduces the progress on heat transfer and heat load of heat stress in the muffler and mathematical methods of numerical technique; secondly, introduces the theoretical of heat transfer, including the theory of transient thermal analysis, thermal analysis of steady-state theory, the mathematical model of heat transfer boundary conditions and thermal stress calculation model; finally, to this article's computational tools, the basic principles of finite element method and the derivation of formulas and equations for calculating been described and analyzed.In the research of exhaust system's heat transfer and thermal load, application of Fluent software to simulate the exhaust system's gas to calculate the temperature distribution, access to the shell of the heat transfer boundary conditions; after by analysis of indirect coupling, the thermal fluid analysis will be mapped to the exhaust system boundary conditions of the solid model, to finite element method for heat transfer and analysis, and the application of ANSYS finite element software to calculate the muffler shell temperature distribution and its resulting thermal stress field distribution, and through the relevant tests to verify the calculation accuracy; finally, the heat transfer and heat load of three muffler model to comparative analysis. The conclusion is in terms of heat transfer and optimum heat load a program, and its simulation analysis of thermal fatigue. Through the main silencer element calculation of transient thermal analysis to obtain the thermal stress distribution of various time points, and through the relevant thermal fatigue theory to estimate fatigue life, and through the thermal fatigue testing to compare analysis. Lastly, research on the thermal fatigue analysis process.To through the exhaust system calculation of thermal analysis, to provide a reliable program for finalize the design, as the future design of the exhaust system to provide a direction of research and ideas, and through this research can be summarized methods of calculation and thermal fatigue life of the exhaust system of ideas.