Investigation On The Theory And Application Of Combustion Modeling For IC Engine

Engine manufacturers are facing increasingly servere emission standards due to environmental concerns and desire for more efficient conversion from chemical energy to mechanical power. Understanding the combustion process in internal combustion engine (IC engine) is the first step for improving emission control and engine performance. This paper has researched the combustion process in IC engine using the technology of computer simulation. Numerical modeling and experiment have been carried out on the diesel engine adopting variable composition air and the Diesel/LPG duel fuel engine. The main contents of this paper are as follow:The computer simulation of the combustion process in IC engine is performed in accord with the general procedure of the computer simulation of the combustion process in IC engine which is summarized firstly.The research results of the three-dimension mathematical models of in-cylinder process in IC engine have been summarized including: basic control equations,state equations,turbulent flow model,fuel spray model,turbulent combustion model,combustion chemical kinetics model,emission model,in-cylinder heat transfer model,initial condition and boundary condition etc. All of the models are integrated to form a complete mathematic models of combustion process in IC engine and are the theory foundation of simulating combustion process in IC engine.Numerical solving method of the mathematic model of combustion process in IC engine have been presented. The simulation software simulating the combustion process in IC engine has been developed based on the KIVA code and validated using the standard sample of KIVA. A calculation platform has been developed which can be used to simulate the combustion process in IC engine which adopts the new combustion mode and clean alternative fuel.The combustion model of the diesel engine which adopts variable composition air has been developed. The characters of the model are as follow: a criterion which can search and find the ignition grid cell automatically has been developed; the characteristic time model has been employed to simulate the combustion process and the four-step fuel oxidation reactions which developed by Westbrock C.K has been employed to simulate the process of fuel oxidation in place of single-step fuel oxidation reaction; Extended Zeldovich mechanism model and Hewson-Bolling mechanism model (HB model) have been implemented to model the form of NO emission.The device which can yield nitrogen-enriched air (NEA) and Oxygen-enriched air (OEA) for the diesel engine has been developed. Numerical calculation and experiment of the influences of diesel NO emission owing to adopting various composition air have been carried out. The mechanism of NO formation has been validated. They are high temperature,oxygen-enriched air and the time of high temperature persistency. The experiment and numerical simulation show that it is useful to lessen the diesel NO emission owing to adopting NEA technology and nitrogen concentration need not be too high. At the same time the power performance and fuel economy of the diesel engine descends and the engine-out emissions :CO and PM emissions increase. So it is necessary to adopt optimizing measurement to gain better effect.The mathematic combustion model for duel fuel engine has been developed, the combustion process in the duel fuel engine is broken into three phases: the period of low temperature ignition, the period of transition to high temperature combustion and the period of high temperature combustion. The Shell ignition model, global Arrehenius equation model and the characteristic time model based on Eddy Dissipation Concept (EDC) model are used to model the process of low temperature ignition of pilot diesel. the process of premixed combustion of pilot diesel and the process of the diffusion turbulence combustion of pilot diesel and the process of premixed turbulence combustion of gas fuel (LPG) respectively. The in-cylinder pressure history calculated is coincided with the results derived from experiment.The numerical simulation and experiment on the combustion mechanism, the combustion process, the property and influence factors of ignition, the mechanism and influence factors of roughness phenomenon, the characteristics of emission and the economy in Diesel/LPG dual engine have been investigated. Many significant results have been derived from the numerical simulation and experiment.. The research shows that it is effective to investigate the mechanism and characteristics of the combustion process in the alternative fuel engine and IC-engine which adopts new combustion mode owing to using the technology of computer simulation.