Search Results

The homogenization of fuel, air, and recycled burnt gases prior to ignition as well as detailed intake, spray, combustion and pollution formation processes of Homogeneous charge compression ignition (HCCI) engine with liquid Dimethyl ether (LDME) fuel are studied by coupling multi-dimensional computational fluid dynamic KIVA-3Vr2 code with detailed chemical kinetics. An extended hydrocarbon oxidation reaction mechanism including 81 species and 362 elementary reactions used for (HCCI) engine fueled with (LDME) fuel was constructed and studded at different engine conditions by using CHEMKIN software and then a validating reduced mechanism that can be used in a modeling strategy of 3D-CFD/chemistry coupling for engine simulation is introduced to meet the requirements of execution time acceptable to simulate the whole engine physicochemical process including intake, spray, compression and combustion process.

A zero-dimensional, thermodynamic model with detailed chemical kinetics and cylinder wall heat transfer correlations has been used to study the detailed oxidation mechanism of natural gas in homogeneous charge compression ignition (HCCI) engine. A short mechanism made up of 241 reversible elementary reactions among 47species has been assembled from a previously extended detailed mechanism. The mechanism was numerically investigated at different operating and geometry conditions of HCCI engine during the time period in which both intake and exhaust valves are closed. The study is performed to elucidate the mechanisms of extinction and combustion behaviors of natural gas fuel with the effect of hydrogen addition to overcome the control of autoignition timing over a wide range of speeds and loads, limiting the heat released rate at high load operation, and meeting emission standards.

This work seeks to confirm the possibility of using Dimethyl ether (DME) as an additive to the blend of pure Natural gas or Natural Gas/Hydrogen blend to improve performance, efficiency, and emissions of a homogeneous charge compression ignition (HCCI) engine. In the proposed technique, Hydrogen could help to extend the operating range of CNG fuel in HCCI engine and decrease the regulated emissions significantly, while DME will play a major role in controlling the auto-ignition timing of the HCCI engine combustion especially at low intake charge temperature. This task has been achieved herein theoretically and numerically with farther validation by the experimental work. The main goal was to find the optimal operating conditions of CNG HCCI engine with the minimum number of laboratory engine tests.

Homogeneous charge compression ignition (HCCI) is a new combustion concept which achieves high efficiency, low nitrogen oxides (NOx), and particulates matter (PM) emissions. In order to realize the HCCI combustion, a homogenous mixture preparation plays an important role in the HCCI engine. However, it is well known that diesel fuel is very difficult to achieve a uniform mixture distribution within the engine cylinder because of its high viscosity and poor fuel vaporization. In order to eliminate these problems, the low viscosity and high volatility Dimethyl ether (DME) was added into diesel fuel to enhance the spray and atomization. The spray tip penetration and spray cone angle of DME/diesel-blended fuel has been examined by using direct photography technology. Measurements were achieved by using spray images taken with a high-resolution CCD camera synchronized with strobe light.

The interaction of natural gas fuel manifold injection with the in-cylinder flow field, and the combustion behavior of an HCCI engine is numerically investigated by using numerous capabilities of multi-dimensional computational fluid dynamic (KIVA-3VR2) code coupled with detailed chemical kinetics. A validating oxidation reaction mechanism that mainly consisted from 314 elementary reactions among 52 species is employed to simulate the whole engine physicochemical process including the intake flow interaction with natural gas port fuel injection, the homogeneity of the gas fuel and the air during suction and compression strokes, autoignition and combustion process. The simulation problem of the gaseous fuel injection by using the original KIVA spray sub-model is solved by implementing a new modification into the original KIVA sub-routines to enable multiple inlet conditions through the use of regions.

In recent years, entirely combined CFD-Multi-Zone chemistry combustion models have been developed fashionably in investigating the HCCI engine combustion. In this work, an enhanced Multi-zone chemistry model is recommended for the HCCI engine combustion and emission simulation. There are four sorts of zones enclosing the crevice zone; boundary layer zone, external zones and center zone of the engine cylinder have been applied. The volume of each zone is steady and depends on the engine geometry. The boundary layer zone is the closest zone to the engine cylinder wall. In this study, the reduced chemical kinetic oxidation mechanism of diesel/biodiesel-ethanol has been numerically investigated in homogenous charge compression ignition (HCCI) engine. The oxidation mechanism of the diesel oil-biodiesel-ethanol at different blends was developed and coupled with Multi-Zone chemical kinetics model.