Experimental and Skeletal Kinetic Model Study of Compressed Natural Gas Fueled Homogeneous Charge Compression Ignition Engine

Diaz Diaz

doi:10.3844/ajassp.2012.917.923

Abstract

Problem statement: In homogeneous charge compression ignition engines fuel oxidation chemistry determines the auto-ignition timing, heat release, reaction intermediates and the ultimate products of combustion. To shorten development time and to understand combustion processes, the use of simulation is increasing. Approach: A model that correctly simulates fuel oxidation at these conditions would be a useful design tool. Detailed models of hydrocarbon fuel oxidation, consisting of hundreds of chemical species and thousands of reactions. A way to lessen the burden was to use a skeletal reaction model, containing only tens of species and reactions. Results: The model was developed from the existing pre-ignition model, which had 10 species, 5 elementary reactions for kinetic and 6 elementary reactions for equilibrium and the standard k-? turbulence model had been used in this investigation. This model combines the chemistry of the low, intermediate and high temperature regions. Conclusion: Simulations are compared with measured and calculated data from the engine operating at the following conditions: speed 1500 RPM, inlet temperature 363-433 K, fuel CNG and ? range 3-5. The simulations are generally in good agreement with the experimental data including temperature, pressure, combustion duration and ignition delay and heat release.

Highlights

Internal combustion engines have been widely used in numerous applications throughout the world
Homogeneous Charge Compression Ignition (HCCI) is defined as the process by which a homogeneous mixture of air and fuel is compressed under conditions that auto-ignition occurs near the end of the compression stroke, followed by the combustion process that is significantly faster than conventional diesel or Otto combustion (Rattanapaibule and Aung, 2005)
Since the mixture is lean and fully controlled by chemical kinetics, there is a new challenge in developing HCCI engines as it is difficult to control the auto-ignition of the mixture and the heat release rate at high load operation, achieve cold start, meet emission standards and control knock (Kong and Reitz, 2003; Soylu, 2005)

Summary

Introduction

Internal combustion engines have been widely used in numerous applications throughout the world. A new mode of combustion is being sought in order to reduce the emission levels from vehicles and one of the new modes is Homogeneous Charge Compression Ignition (HCCI) engines. Since the mixture is lean and fully controlled by chemical kinetics, there is a new challenge in developing HCCI engines as it is difficult to control the auto-ignition of the mixture and the heat release rate at high load operation, achieve cold start, meet emission standards and control knock (Kong and Reitz, 2003; Soylu, 2005).

Results

Conclusion