الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
An efficient used of the world energy sources and reducing the level of atmospheric pollution is an ever increasing demand. A CONSIDERABLE A mount of investigations have been carried out on either improving the combustion characteristic of fuel-air mixture in internal combustion engines or looking for alternative fuels.
It was after Otto`s invention of the four-stroke engine in 1877 that gasoline became the fuel in automobiles because of it `s easy handling properties and relatively high energy content. Most of the early development of the internal combustion engine was based on the use of gaseous fuels. Gas fueled engines were found primarily in stationary applications only. In recent years, the use of gaseous fuels in engines has been encouraged for its pollutant emissions and the high cost of the liquid fuels.
Natural gas, because of its properties has a considerable potential as a future resource to replace conventional fossil fuel. Natural gas appears to be capable of performing a prominent role among alternative fuels. In fact, it costs less than other types of fuel, and it is accessible in countries where there are existing distribution infrastructures. Using natural gas as a fuel for internal combustion engines results in reduction of pollutant emissions, reduces engine wear and noise level, extends engine life and decrease engine maintenance.
The gasoline powered internal combustion engine, when modified to take advantages of the properties of natural gas, can reach better efficiency. The modifications performed on the vehicle address specifically fuel storage and delivery.
In this thesis, a series of comparison tests was conducted on a single cylinder, spark ignition engine, which is modified to run on either gasoline or/and natural gas to investigate the effect of using natural gas as a fuel on engine performance and exhaust emissions. The engine test bed used in this investigation is fitted with all equipments and devices required for measuring the performance parameters such as power, mass flow rate of air and fuel, exhaust temperature and speed, and also the exhaust emissions of carbon monoxide and unburned hydrocarbons.
During the test, natural gas proved to be a good fuel for spark ignition engine with minimum alteration. It is indicated through the results that, natural gas engine can operate much leaner than gasoline, and produce less emissions and reduce engine specific fuel consumption. The results obtained indicate that, there is a DROP in power by about 11 % due to the reduction in volumetric efficiency by about 31% over all ranges of operating conditions. Also during all operating ranges, the carbon monoxide was reduced by about 24 %.
A mixture of natural gas and gasoline was tested with variable percentage content of gas , and the results from these tests show an important in engine performance characteristics for a maxiture containing 24 % natural gas by weight as compared with either natural gas only or gasoline only.
A simple method of supplying a constant flow rate of natural gas is tested in the present experimental work. It is found that, there is a simple way to each nearly the same characteristics ot trend of gasoline fuel in engine by operating conditions without any need for complex adaptors or conversion systems. For the engine under investigation, a gas flow rate of about (1.3 Kg/hr) can be used to cover a wide range of operating conditions.