الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The major challenge in Egypt is to urge the owners of passenger vehicles to use unconventional fuel instead of petrol in their vehicles by adding CNG kit. Unfortunately, this generates some major problems. Several diagnoses and side effects have been faced in petrol engines which are provided with CNG kit such as misfire, valve seats recession, backfire and low service life of the engine. Many technical problems have been faced in vehicles which are designed to operate efficiently by petrol. The objective of this study is to investigate the effect of using natural gas as a fuel on the S.I.E behavior in passenger cars in Egypt. The primary approach for solving these problems was to decrease the negative side effects on the engine when operating on CNG mode.
To achieve the objective of this thesis, a set of customer surveys was carried out to find out the customer expectations and a target was set to achieve the best balance between both engine service life and customer satisfaction.
The effect of changing valve angle from 45° to 40°, 35° and 30° on reducing the stress on the exhaust valves was investigated by using ANSYS program software.
The improvement of service life of the engine was attained by changing the angle of the exhaust valve from 45° to 30°.the result was decrease of wear (increase of wear resistance) of the valve, which led to the increase of service life of the exhaust valve.
The temperature downstream the exhaust valve was measured at different engine speed and time, and it was found that it increased with the increase in engine speed. The behavior of flow of CNG and air in the mixer was investigated by using ANSYS
Software and it was found that when a screen of mesh was used homogenous mixture was obtained.
A screen of wire mesh was installed in the mixer throttle .Two different meshes were used: Mesh A and mesh B .the size of cell was not the same in both meshes. Backfire was reduced in the case of mesh A and was eliminated completely in the case of mesh B. The emission was measured after using the screen of mesh and the percentage of CO, HC, and CO2 was improved.