الفهرس 
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Abstract
In the present work, a complete temperature - entropy chart for natural gas was constructed. The T-S chart consists of different curves, including the constant pressure lines, constant volume lines, enthalpy and energy curves. A computer (Basic) program was designed to calculate all thermcdynamic properties at different temperatures and excess air factor (”-). This computer program aids plotting any T-S chart at a certain air/fuel ratio to be used for any natural gas.
The T-S chart was constructed for the natural gas of Abu-Qir gas fields, with average carbon and hydrogen contents of 76 % and 24 % respectively. The T-S chart of Abu-Qir natural gas was constructed for five cases at ”-=1 (stoichiometric), ”-=1.1 (for NG engines), ”-=1.5 (for NG lean burn engines), ”-= 2 (for NG boilers & furnaces), and ”-=4 (for NG turbines). The combustion of Abu-Qir NG was studied and the exhaust gases produced at any air/fuel ratio were considered in the designed computer program. The numerical results of all calculations were compared to the available thermodynamic tables.
The performance of the spark-ignited Wuakesha gas engine at Abu-Qir gas fields was studied on the constructed T-S chart at ”-=1.1 and compared to the performance of a similar engine burning Benzene fuel. In addition, the problem of Back-fire in gas engines could be demonstrated through plotting the Fanno line of the exhaust system, of the applied spark ignited gas engine. The critical chimney height was fixed.
The performance of Solar gas turbine running at Abu-Qir gas fields was also studied on the T-S chart at ”-=4 and the Fanno line of the exhaust system was studied to fix the maximum exhaust pipe height.
The obtained results showed that the used computerized calculations are satisfying the tables of thermodynamics which prove the a(;l,;uracy of the constructed T-S charts at different air/fuel ratios. The performance results of the applied gas engine on the T-S chart at 1-.=1.1 reached conclusions and recommendations to avoid Back-fire in spark-ignited, natural gas engines.