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Tests have been conducted on a special single cylinder-indirect injection-compression ignition-research engine (Ricardo- E6) fueled with gaseous fuel to investigate the effects of operating conditions such as concentration of gaseous fuel, quantity of diesel (pilot) fuel injected, injection timing of pilot fuel and exhaust gas recirculation (EGR) ratio on the NOx emissions. Diesel fuel was used as the pilot fuel and methane or propane were used as the main fuel which was inducted in the intake manifold to be mixed with the intake air. Through the experimental investigations, it is shown that, NOx emissions increase significantly by increasing the concentration of the gaseous fuel (total equivalence ratio), employing a large pilot fuel quantity, heating the inlet gaseous fuel-air charge and advancing the injection timing of pilot fuel. It was found that admission of diluents resulted in reductions in exhaust oxides of nitrogen (NOx).

The operation of diesel engines on gaseous fuels commonly known as dual fuel engines in which diesel fuel was used as the pilot fuel and the gaseous fuel (methane and sometime propane in the present work) was used as the main fuel. The gaseous fuel was inducted in the intake manifold to mix with the intake air. The investigation was conducted on a high speed indirect injection (Ricardo-E6) dual fuel engine and was concerned with the effects of exhaust gas recirculation (EGR) on dual fuel engine combustion and emissions,in particular, the effects of intake air temperature and diluent admissions (N2 & CO2) on combustion and emissions. The use of diluents to displace oxygen (O2) in the intake air resulted in reduction in the O2 supplied to the engine, increased inlet charge thermal capacity (thermal effect), and, potentially, participation of CO2 and N2 in the combustion process (chemical effect).

A quasi-two zone predictive model developed in the present work for the prediction of the combustion processes in dual fuel engines and some of their performance features. Methane is used as the main fuel while employing a small quantity of liquid fuel (pilot) injected through the conventional diesel fuel system. This model emphasizes the effects of chemical kinetics activity of the premixed gaseous fuel on the combustion performance, while the role of the pilot fuel in the ignition and heat release processes is considered. A detailed chemical kinetic scheme consists of 178 elementary reaction steps and 41chemical species is employed to describe the oxidation of the gaseous fuel from the start of compression to the end of expansion process. Depend on the results of the sensitivity analysis, the detailed chemical kinetic scheme was simplified to another scheme consists of 41 elementary reaction steps and 17 chemical species to reduce the time of computations.

It is well known the dual fuel operation at lower loads suffers from lower thermal efficiency and higher unburned percentages of fuel. The present work includes a computational investigation to predict the effects of Exhaust gas recirculation (EGR) on the operation of an indirect-injection dual fuel (Ricardo-E6) engine by using a detailed chemical kinetic scheme and a quasi-two zone analytical model. The comprehensive chemical kinetic scheme for methane oxidation consisting of 178 elementary reaction steps with 41 species. A quasi-two zone analytical model is based on the effective energy releases of the pilot diesel fuel while using the detailed chemical reaction kinetic scheme for the oxidation of methane. Through the results, it was shown that, the active species such as H, O and OH produced in the high temperature combustion process and found in the exhaust gases are play a significant role in the preignition reactions.

It is well known that the operation of dual fuel engine at lower loads suffers from lower thermal efficiency and higher unburned percentages of fuel. To study this problem, tests have been conducted on a special single cylinder- compression ignition research engine (Ricardo E6) to investigate the effect of pilot fuel quantity on the performance of an indirect diesel engine fueled with gaseous fuel. Diesel fuel was used as the pilot fuel and methane or propane were used as the main fuel which inducted in the intake manifold to mixed with the intake air. Through the experimental investigations, it is shown that, the low thermal efficiency and poor emissions at light loads can be improved significantly by increasing the amount of pilot fuel. While increasing the amount of pilot fuel at high loads led to early knocking.

The combustion processes of of lean mixtures of methane in air is examined by employing a detailed chemical kinetic scheme consisting of 178 elementary reaction steps with 41 species. The changes with time in the concentrations of the major relevant reactive species are determined from the preignition reactions to the time near equilibrium conditions. The results of such an approach to the combustion process are considered over a wide range of initial temperatures (1000 K - 1600 K) and equivalence ratios (0.2 - 1.2) while the pressure was kept at atmospheric. Calculated results obtained while using this model tend to be in good agreement with the corresponding experimental values of ignition delay. The ignition delay of methane-air mixture correlated by the following empirical expression in which constants A and B are function of the equivalence ratio while Ti is the initial mixture temperature in °K.

An experimental investigation of the performance of a mixture preparation system used with spark ignition internal combustion engines is presented. The proposed carburetor works on the principle of adiabatic vaporization of liquid gasoline fuel before it is led to engine cylinders by means of passing atmospheric air, induced by engine suction, through fuel. The study aims at the determination of parameters that affect the performance of this system. It is demonstrated through the results that this carburetor is a better device for mixture preparation in spark ignition engines having numerous advantages over conventional carburetors most notably fuel economy.