Study On Numerical Simulation For The Influence Of Intake System Structure On Volumetric Efficiency Of Diesel Engine

For the diesel engine, it’s helpful to improve the combustion process, if abundant fresh air could be inhaled into the cylinder, which enhance the power performance of the engine. Volumetric efficiency is a parameter of measuring the degree of completion in the intake process. The structure of inlet pipe can apparently influence volumetric efficiency, and to research it for the optimization of intake pipe structure and volumetric efficiency, which is significant to improve the power performance of the engine.In the intake process, the gas pressure waves that spread regularly in the pipe and is caused by the pressure difference due to the motion of the piston, which could increase the air input in the condition of returning the positive pressure during the opening of the inlet valve, so that to make the higher pressure than normal. This phenomenon of gas dynamics is called intake resonance. To design effectively the intake pipe structure such as length, diameter and volume of the pipe system, which can take advantage of the intake resonance to improve the volumetric efficiency and combustion process, is able to achieve the aim of improving the performance of the engine.This paper introduces the classic and common one dimensional unsteady flow numerical analysis method in detail such as characteristic method(CM), finite volume method(FVM) and finite difference method(FDM) individually, and explains the their basic principle, by which elaborate on the phenomenon of one dimensional flow in the inlet pipe, in order to comprehend the physical process, to analysis the issue of one dimensional flow and to lay a foundation on operating the specialized simulation software.This paper researches the influence of the intake pipe structure parameters of multi-diesel engine on volumetric efficiency with AVL Boost, and propose a scheme of improving the pipe structure. For the purpose of operating AVL Boost effectively, this paper at first explains the theory of the software and introduces the methods of setting software parameters, on the foundation of which simulates a four-cylinder direct injection diesel engine of LL480B with AVL Boost on a established model. It is rational to consider the model accurate for the engine and fundamental for the next step of the simulation task to the volumetric efficiency analysis, by the contrast of the external characteristic data curves of experiment and simulation.This paper improves the length, diameter and the volume of the intake pipes on the engine model with AVL Boost. The improved engine performance of the new intake pipe structure, contrasted with the original engine, which is proposed by analyzing the tendencies of change on volumetric efficiency, torque and pressure waves under the condition of different engine speeds, is considered better than the original intake pipe structure of the engine and indicates a definite direction for the CAD design of intake pipe.