VOL. 4, NO. 1, FEBRUARY 2009 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2009 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com SIMULATION OF IN-CYLINDER PROCESSES IN A DI DIESEL ENGINE WITH VARIOUS INJECTION TIMINGS S. M. Jameel Basha 1 , P. Issac Prasad 2 and K. Rajagopal 3 1 Mechanical Engineering Department, Intell Engineering College, Anantapur, A. P., India 2 Mechanical Engineering Department, Koneru Lakshmaiah College of Engineering, Vijayawada, A. P., India 3 Mechanical Engineering Department, JNT University, Hyderabad, A. P., India E-Mail: jameel_junaid@yahoo.com ; Prasadissac2002@yahoo.co.in ABSTRACT The gas motion inside the engine cylinder plays a very important role in determining the thermal efficiency of an internal combustion engine. A better understanding of in cylinder gas motion will be helpful in optimizing engine design parameters. An attempt has been made to study the combustion processes in a compression ignition engine and simulation was done using computational fluid dynamic (CFD) code FLUENT. An Axisymmetric turbulent combustion flow with heat transfer is to be modeled for a flat piston 4-stroke diesel engine. The unsteady compressible conservation equations for mass (Continuity), axial and radial momentum, energy, species concentration equations can express the flow field and combustion in axisymmetric engine cylinder. Turbulent flow modeling and combustion modeling was analyzed in formulating and developing a model for combustion process. 1. INTRODUCTION The Modeling of a process has come to mean developing and using the appropriate combination of assumptions and equations that permit critical features of the process to be analyzed. The new and changing requirements demanded by the market have greatly increased the complexity of engine design to give optimum operating characteristics to the fuel economy and limitations in emissions models that are being developed and used to describe engine operating and emission characteristics can be categorized as thermodynamic or fluid dynamic in nature, depending on weather the equations which give the model its predominant structure and based on energy conservation or a full analysis of the fluid motion engine combustion models are classified as  Thermo dynamic based models (Zero dimensional models)  Fluid dynamic based models (Multi dimensional models) The new dimensional models usually refer to a thermodynamic analysis of the engine cycle where charge is assumed to be uniform in composition. These models are not realistic in nature. Fluid dynamic based models are often called as multi dimensional models due to their inherent ability to provide detailed information of the spatial distribution of gas velocity and other characteristics of the flow within the engine cylinder [2]. These models are realistic in nature and are able to take care of the combustion chamber geometries. 1.1 Scope of present work It is evident from the foregoing discussion that multidimensional calculations for the in cylinder flows are proved to be powerful tool as diesel engines are widely used now a days. A two dimensional Axisymmetric model has been chosen for this investigation. The turbulence model and combustion model has been taken for analysis. The turbulence and combustion models used are made as clear as possible to capture the real process. The three dimensional model with changed piston geometry, injection, valve motor would demand greater computer capabilities for analysis. 1.2 CFD Analysis CFD codes are structured around the numerical Algorithms that can tackle fluid flow problems. In order to provide easy access to their solving power all commercial CFD packages include sophisticated user interfaces to input problems parameters and to examine the results. Hence all codes contain three main elements. A pre-processor (ii) a solver and (iii) a post-processor Pre-processor The user activities at the pre-processing stage involve:  Definition of the geometry of the region of interest: The computational domain.  Grid generation-The sub division of the domain in to a number of smaller non overlapping sub domains : a grid (or mesh) of cells.  Selection of the physical and chemical phenomena that need to be modeled.  Definition of fluid properties.  Specification of appropriate boundary conditions at cells which coincide with or touch the domain boundary. The accuracy of a CFD solution is governed by the number of cells in the grid. In general, the larger the number of cells, the better the solution accuracy. 1