Search Results

We developed a numerical method for PFI engine, which would take complex intake-port phenomena into consideration. Numerical study for PFI engine has additional difficulty compared with that for GDI engine, because in-cylinder distribution of mixture is strongly affected by remaining fuel in intake-port. The new simulation method proposed in this paper has adopted split calculation of two steps. Fuel distribution in intake-port is calculated in the first step, and then this result of adhered and floating fuel distribution in intake-port is used as boundary and initial conditions in the next step. Together these two steps realize accurate in-cylinder mixture distribution prediction. According to experimental verification, the new method showed a capability to predict accurate liquid film distribution with less calculation cost. And then we applied the method into the investigation for optimum injection strategy to improve engine performance and to reduce emission.

We developed the numerical simulation tool by using OpenFOAM® and in-house simulation codes for Gasoline Direct Injection (GDI) engine in order to carry out the precise investigation of the throughout process from the internal nozzle flow to the fuel/air mixture in engines. For the piston/valve motions, a mapping approach is employed and implemented in this study. In the meantime, the spray atomization including the liquid-columnbreakup region and the secondary-breakup region are simulated by combining the different numerical approaches applied to each region. By connecting the result of liquid-column-breakup simulation to the secondary-breakup simulation, the regions which have different physical phenomena with different length scales are seamlessly jointed; i.e., the velocity and position of droplets predicted by the liquid-column-breakup simulation is used in the secondary breakup simulation so that the initial velocity and position of droplets are transferred.

A 3D simulation technique to estimate density of particulate matter (PM) from spark ignition (SI) gasoline engines is proposed. The technique is based on a two-equation model consisting of coupled conservation equations of soot particle number and mass and fluid transportation equations. The nucleation rate of soot particles was obtained from a database built by simulation of elementary reaction with the proposed technique. Two approaches were explored to obtain the nucleation rate. One involves 0-dimensinal SI simulation and the other involves 1-dimensinal flame propagation simulation. The estimation results were verified with measurement data obtained with a single cylinder SI engine a homogeneous pre-mixed fuel was supplied. It was confirmed that appropriate results could be obtained with the 1-dimensional approach for the nucleation rate model.

A technique of estimating particulate matter (PM) from gasoline direct injection engines is proposed that is used to compute mass density and particle number density of PM by using fuel mass in rich mixtures obtained by using non-combustion computational fluid dynamics (CFD). The CFD code that was developed by the authors employed a Cartesian coordinates system as a discretization method and large eddy simulation (LES) as a turbulence model. Fuel spray droplets were treated with the discrete droplet model (DDM). The code was verified with some experimental data such as those obtained from in-cylinder gas-flows with a laser Doppler velocimeter (LDV) and in-cylinder fuel concentration with laser induced fluorescence (LIF). PM emissions from a single-cylinder gasoline direct injection engine were measured with an electrical low pressure impactor (ELPI) to determine the model constants that were required in the estimation model.