الفهرس 
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Abstract
Air pollution presents a major problem in crowded cities like Cairo; a major amount of that air pollution is due to internal combustion engine emissions. The use of Natural Gas in internal combustion engines improves the air quality. Natural gas is a green house fuel, and found in big quantities in Egypt.
Natural Gas is used in automotive` engine, and stationary engines for power generation. Natural Gas can be admitted directly to the engine from the main supply without the need of the high cost gas supply systems.
The present work deals with the behavior of Natural Gas in the combustion chamber of stationary engines.
The effect of flame speed on burning rate and performance of an air-cooled gasoline engine run on NG fuel was studied.
The tests were carried out on a single cylinder-spark-ignition-stationary air cooled, without any control on the cooling fluid temperature to simulate the actual working conditions. The engine was fed with Natural Gas from the main domestic pipeline supply, also with gasoline through a simple carburetor. An ionization gap measuring circuit in conjunction with a high-sampling rate data acquisition system was used for flame speed measurements inside the engine cylinder.
Two cases of experiments were carried out:
In the first, gasoline was used as a fuel. In the second, Natural Gas was used.
The effects of three parameters, namely the equivalence ratio, engine speed, and throttle opening were studied in both cases. Special attention was given to flame speed measurements, and its connection with the other performance and emission parameters.
The equivalence ratios tested varied from 0.72 to 1.65 for Natural Gas, and from 0.85 to 1.48 for gasoline fuel.
The speeds tests varied between 2500 and 3600 rpm. The effect of throttle openings between 40% to 100% full throttle opening was studied. The results showed better performance with full throttle opening than those of part throttle openings.
The following results of using Natural Gas in SIE`s were recorded:
-A power loss of about 40% was observed when using Natural Gas instead of gasoline. The major reason for this is the reduction of volumetric efficiency of Natural Gas fueled engines.
- Under the normal operating conditions of the engine, Natural Gas attained higher flame speeds than gasoline, for equivalence ratios lower than 1.28,and all throttle openings and the range of speeds tested;
-For Natural Gas, the maximum values of flame speeds and power were observed with mixtures leaner than those of gasoline. Both maxima were observed in the slightly rich side.
-Higher exhaust temperatures were observed with Natural Gas than those for Gasoline.
-The measured emission levels (CO, and HC) were lower in the case of Natural Gas than those in the case of Gasoline.
-Higher thermal efficiencies and lower bsfc were observed with Natural Gas, than those of Gasoline.
In addition, a semi-empirical correlation for calculating flame speed, as well as simple procedure for calculating the burning rate were given.
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