The Transient Numerical Analysis Of In Cylinder Flow Field Of The Engine Intake Process

The intake process as engine work cycle begin, it has played a key role in engine workprocess. The gas flow organization of the engine intake process will directly influence thecombustion process of the flame propagation, the stability of the burning and burning whethercompletely, further influence engine performance and its emissions.The conventional method of engine intake process research is through the experiments toobtain the gas flow in intake process parameters and study the flow condition, it need highcost and long experimental period. As continuous improvement of the computational fluidmechanics theory and the development of computer technology, the numerical simulationmethod has gradually become the main method of engine working process research,especially for the gas flow in engine cylinder transient numerical simulation has become theresearch focus, because the transient numerical simulation is consistent with the engine actualworking process, it can observe the flow state formed by gas in cylinder in the intake processintuitive and get more comprehensive flow field information. Numerical simulation methodalso has low cost, short cycle advantages.In order to have a more profound understanding of the engine intake process, this articlehas done the following work, create the three-dimensional model of helical intake port-valve-cylinder; research on how to divide the grid of port-valve-cylinder in this transient simulation,make the change of the grid in the simulation process and the valve and piston in actualmovement is consistent, and maintain a good quality; based on the control volume methodand combined with dynamic mesh technology, in the light of a spiral inlet port of dieselengine intake process for three-dimensional transient numerical simulation. According to thesimulated calculation results analysis of the two different helical intake port position we canfound:1. When the simulation under the condition that the small valve lift, the position of helical intake port position have an insignificant influence on the intake process flow structurechange, but according to the size of parameter change curve, the induction effect of the intakeprocess under the condition of helical intake port in radial arrangement is better than thetangential arrangement.2. Through the analysis of the velocity vector graph on cylinder different height crosssection of intake process in different crank angle can found that gas flow guided by spiralinlet volute during the intake process, eddy generated in the upper part of the cylinder andtransfer from the upper to the lower in a spiral downward and ending in the bottom of thecylinder as a more stable eddy current.3. Through the analysis of the velocity vector graph on cylinder longitudinal section ofintake process in different crank angle can found that, the cylinder interior gas is sucked underintake valve and guided by the wall of the cylinder, form two vortices. The two vortexgradually merge into a larger tumble in the later period of intake process.The conclusions of this paper have a more intuitive understanding of how the flow fieldchanges during the intake process of diesel engine with helical intake port, and providereferences for the air intake system design and optimization of the diesel engine.