FSAE Racing Engine Air Intake System Optimization Design

Rational engine air intake system design can reduce the energy loss in the inlet, guarantee the charging efficiency of engine and improve the engine power. To determine the structural parameters of air intake system is the main content of the air intake system design. FSAE car air intake system generally consists of air filter, throttle, flow-limiting valve, diffuser, voltage stabilizing cavity and intake manifold. This article optimized the CQUFSAE racing engine air intake system based on 1d simulation and 3d simulation software GT-Power and FLUNET. Considering the fluid flow characteristics, this papper improved the charging efficiency of air intake system, and reduced the loss of flow, optimized the engine torque and power. This paper mainly studied the following aspects:(1) Firstly, this paper introduced the technology of variable intake manifold and the development of engine air intake system numerical simulation,made the decision to carry on the air intake system numerical simulation to achieve the goal of optimization design.(2) Secondly, this article introduced the air intake system performance evaluation index "volumetric efficiency" and "charging efficiency". Dynamic effects of air intake system were analyzed: reasonable design of the secondary variable intake manifold can effectively improve the charging efficiency of engine applying dynamic effects. The frictional energy loss and the local energy loss in the air intake system were analyzed. 2015 FSC contest rule was analyzed, the preliminary selection, air intake form selection, flow-limiting valve design, throttle selection and the arrangement of the diffuser were completed, and the installation position of racing air intake system was determined.(3) The third, this paper expounded the use of GT-Power software to establish the engine, the air intake and exhaust system model, meanwhile the process of parameter Settings, and made use of the engine bench test results to verify the model. Discussed the influence of diffuser position change on the engine power, torque and charging efficiency, and determined the optimal opening Angle of diffuser as 8°. Studied the effect of air intake manifold length change on the engine performance, determined the secondary variable intake manifold length to be 180 mm and 74 mm respectively, switch point to be 10000 rpm, using long intake manifold with low speed, short intake manifold with high speed. Analyzed the influence of cavity volume change on the engine power, torque, and charging efficiency, the selected voltage stabilizing cavity volume was 3L. Determined the work length of flow-limiting valve to be 15 mm.(4) Finally, this paper introduces the CFD theory and basic knowledge of the turbulence model, determined to use standard k-? simulation model for fluid flowing in air intake system. Used CATIA to establish the three-dimensional fluid model of air intake system, completed the grid division, applied the data from one-dimensional simulation to the three-dimensional fluid boundary condition, completed solver Settings. Set the Chamfering of diffuser and Angle of intake manifold as variables, A total of 36 fluid models are set up, using FLUENT software for simulation analysis. This papper compared the mass flow rate of each model to find the best uniform one: diffuser chamfering was 80 mm, intake manifold Angle was 100°, and finally completed the air intake system design.