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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.

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.