The Research In The Flow Field Characteristics Of Ventilation System Of Variable Stroke Engine

Variable-stroke engine, which can switch working mode based on driving conditionscombines the advantage of two-stroke and four-stroke engine. It has better dynamicperformance and economic performance, and will be one of the promising direction ofengine development. But there are some problems, such as poor ventilation quality, lowvolumetric efficiency, even ignition problems and other issues when four-stroke workingmode is converted to two-stroke working mode. So the main task of this paper is to studyventilation system in the two-stroke mode of variable-stroke engine. CFD (ComputationalFluid Dynamics) has matured on the research of Internal combustion engine. So this papermainly uses CFD to study ventilation system of two-stroke working mode.First, this paper introduces conservation equation of gas flow and the combustionmodel, which provides a theoretical basis for the numerical simulation of ventilationsystem of two-stroke working mode. Then uses CATIA software to establish the HondaWH125-6engine geometry model, contains intake port, combustion chamber, exhaust port.Uses pretreatment software Hypermesh to transfer geometric model into surface mesh,and then uses the professional internal combustion engine simulation software FIRE to getvolume mesh and dynamic mesh of the geometry model. This paper uses the professionalone-dimensional engine simulation software BOOST based on proved reliability toprovide accurate boundary conditions and initial conditions for FIRE.Increasing the inlet pressure and changing the inlet tilt rate are two main ways toimprove volumetric efficiency. In this paper, by using FIRE, respectively simulate ondifferent inlet pressure and different inlet tilt rate, get a detailed analysis of the velocityfield, pressure field and turbulent kinetic energy, also the combustion field and chargingefficiency, then compare the advantages and disadvantages of various physical fields,summarize the rule of the flow field parameters. Eventually determine the inlet pressure of0.18MPa for reasonable inlet pressure and90°inlet tilt rate is the better inlet tilt rate.