| Boats,as traditional means of water transportation,have always played a vital role in transportation.Nowadays,with the increasing demand for entertainment,high-speed boats have also been widely used in modern water tourism projects.As the main power source of ships,engines have stricter technical requirements than vehicle engines.In recent years,with the rapid development of social economy and the advancement of engine technology,boat engines are developing in the direction of high speed,low fuel consumption and strict emissions.However,as an important system of the engine,the intake and exhaust system,its layout type,structural parameters,etc.have a crucial impact on the power and fuel economy of the engine.Therefore,it is particularly important to analyze and optimize the intake and exhaust manifolds in order to give full play to the power and fuel economy potential of the engine.This article takes a SJ486 high-speed gasoline engine with a displacement of 1.8L from a certain boat company as the research object.In order to improve the mid-high speed power and economy of the engine,The structural parameters such as the length,diameter,resonant cavity volume and layout of the manifold were optimized by numerical simulation.It has achieved the improvement of engine mid-high speed power and the improvement of fuel economy,and provides reference and guidance for the designing and manufacturing of the manifold.Have certain theoretical research value and more important engineering guidance significance,The main research contents of this article are:1.Early test and model building.Build an engine bench test platform,measure the relevant performance characteristics of the high-speed gasoline engine under various operating conditions,and carry out disassembly surveying and mapping.The engine working process simulation software GT-POWER was used to build the gasoline engine performance simulation model,and it was calibrated with bench test data to ensure the effectiveness of further analysis.2.Analysis of the influence of structural parameters on performance.Based on the calibrated performance simulation model,the influence of the intake and exhaust manifold length,diameter,resonant cavity volume,layout and other intake and exhaust manifold structural parameters on engine power and fuel economy is analyzed.This provides direction and guidance for the optimization of subsequent intake and exhaust manifolds.The analysis results show that,compared with the original intake and exhaust manifolds,the central intake manifold and 4-2-1 exhaust manifold are more beneficial to improve the power of the engine and improve fuel economy;increase the intake and exhaust manifold Structural parameters such as the length of the tube and the volume of the resonant cavity are conducive to improving the high-speed power and fuel economy of the engine.3.Multi-objective optimization analysis of engine performance.Using the design of experiment(DOE)method,the structural parameters of the intake and exhaust systems are selected as the test factors,and the engine power and fuel economy are used as the test response,And the second-order response surface fitting is carried out based on the experimental data.Then,taking the best performance of medium and high speed power and fuel economy as the optimization goal,and setting weight coefficients for low,medium and high speed,so as to perform multi-objective optimization.The optimization results show that The maximum torque of the engine has increased by 1.22%,the maximum percentage of increase has reached 2.22%,the fuel consumption rate has dropped by a maximum of2.14%,and the maximum fuel consumption rate has dropped by 1.46%.The power and economy of the engine have been improved,Reached the development goal.4.Flow field analysis and optimization.Based on the optimized intake and exhaust structure schemes,the intake and exhaust manifolds were re-modeled in 3D software,and the flow characteristics were simulated and analyzed using the 3D simulation software STAR-CCM +,Furthermore,the space structure was further optimized,and good flow characteristics were obtained,and the final optimization plan was proposed to provide reference and guidance for the designing and manufacturing of the actual intake and exhaust manifolds. |
