الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 114 |  |  |
| | | from | 114 | | |
Abstract
The present work is an experimental investigation 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 cyclic variations.
The engine test rig used in this investigation is fitted with all the instrumentation required for evaluating engine performance 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.
The test rig was also furnished with computer controlled data acquisition systems with a complete set of software for monitoring and recording the variation of cylinder pressure.
The tests are performed on the engine at idling and at low load conditions, where the variations are very clear and can studied easily.
During the tests, natural gas proved to be a good fuel for spark ignition engine. It is indicated through the results that the engine speed and mixture equivalence ratio has the greatest influence on cyclic variations. These variations decreased as the engine speed and the air/fuel ratio increase.
The use of natural gas generally has a positive effect in reducing these variations.
When natural gas is used as a fuel to investigate the effect of engine speed on cycle by cycle variation, the coefficient of variation of cylinder pressure decrease by a bout 44% compared with a gasoline as a fuel. Also for increasing engine speed the coefficient of variation is reduced by 29%, air to fuel ratio 39%, exhaust temperature 35%, carbon monoxide 50% and unburned hydrocarbon by 41%.
Also, when using natural gas as a fuel to investigate the effect of increasing air to fuel ratio on cycle variation, the coefficient of variation of cylinder pressure decrease by 48% compared with a gasoline as a fuel. Also for engine speed the coefficient of variation is reduced by 39%, air to fuel ratio by 32% exhaust temperature 39%, carbon monoxide percentage 65% and unburned hydrocarbon 40%.
………………………………………………………………………………………………………….