Structure Optimization For Engine Exhaust Manifold Based On Fluid-solid Coupling

Exhaust manifold is one of the important components of engine exhaust system. The capability of adapting thermal load and thermal stress to determine the reliability of the engine. The flow condition inside the exhaust manifold affect engine performance such as scavenging performance, residual hydrocarbon and exhaust hydrocarbon and pumping work. Exhaust manifold has a higher required in the turbocharged diesel engine. Not only need to withstand thermal load, but also influence the use of pulse energy and the actual efficiency of turbine. Thus affect the engine of the transient intake capacity. Therefore, research and analysis the performance of internal transient gas flow and heat transfer process of solid wall of the exhaust manifold is much instructive significance to improve its efficiency and lifetime.Primarily, based on the experimental measuring and one-dimension simulation, this paper conduct the numerical simulation of inner transient flow-field of exhaust manifold on a heavy diesel engine. In order to ensure the correctness of transient flow in exhaust manifold, this paper conduct the numerical simulation of the engine working process based on the structure and working parameters of the engine by software GT-POWER, and hence, we come through the transient flow boundary conditions of the exhaust manifold. Through the calculation of the flow field in the exhaust manifold transient, this paper analysis the inner gas flow situation in different times, and study the smoothness and dissipate during exhaust stroke of each cylinder, and the influence between each cylinder when in exhaust stroke.Secondly, this paper conduct the flow-structure coupling numerical simulation of inner flow-field of the exhaust manifold. In order to get the accurate pipe temperature, this paper first conduct the external flow numerical simulation of exhaust manifold, by external flow field simulation, we can get the accurate convective heat transfer coefficient of external exhaust manifold.Thirdly, this paper conduct the flow-structure coupling simulation of exhaust manifold. By using flow-structure coupling simulation of both flow-field in exhaust manifold and solid temperature, we can transfer the convective heat transfer coefficient and inner temperature boundary into the internal boundary of fluid-structure coupling simulation, which is hard to determine in single flow field simulation or single solid field simulation. By fluid-solid coupling numerical simulation, we can get fluid-solid heat transfer with high accuracy, and thus, we can get the more accurate fluid temperature field and solid temperature field. At last, we provide improvement advice to the thermal load of exhaust manifold.