A comparative energy and exergy analysis was experimentally performed using a bi-fuel compressed natural gas (CNG) spark ignition engine. The experiments were conducted for gasoline and CNG fuel at 1700 rpm and different operating loads from 5 to 30 Nm. The experiments were performed under stoichiometric air-fuel ratio and maximum brake torque ignition timing. Quantitative and qualitative analysis were conducted using the first and second law of thermodynamics, respectively. The effect of engine operating load on various energy and exergy parameters was compared for both the fuels. Output energy with respect to engine load was found higher for CNG compared to gasoline. Engine wall heat transfer was also higher in the CNG engine case due to its high combustion chamber temperature and lower burning velocity. The difference in heat transfer energy fraction between gasoline and CNG gradually increased with engine load. The exhaust energy was found maximum in the case of CNG under low operating load and reduced to a minimum at higher engine operating load. The unaccounted energy fraction was found lower for the CNG engine and reduced with respect to engine load. CNG exhibits the highest exergy efficiency (26.80%) compared to gasoline (25.50%) at 30 Nm load. On average, a 2% higher exergy efficiency was observed with the CNG engine at all operating load conditions. This indicates CNG has a higher potential to convert chemical energy present in the fuel into useful work output. CNG shows lower exergy destruction at all operating loads compared to gasoline, and it reduces significantly at higher engine loads. In all operating loads, exergy transfer due to exhaust gas and heat transfer to the wall was higher in the case of CNG.

中文翻译：

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双燃料压缩天然气火花点火发动机热力学过程的定量和定性分析

使用双燃料压缩天然气 (CNG) 火花点火发动机通过实验进行比较能量和火用分析。实验是针对汽油和 CNG 燃料在 1700 rpm 和 5 到 30 Nm 的不同操作负载下进行的。实验在化学计量空燃比和最大制动扭矩点火正时下进行。分别使用热力学第一定律和第二定律进行定量和定性分析。比较了两种燃料的发动机运行负载对各种能量和火用参数的影响。与汽油相比，CNG 的输出能量相对于发动机负载更高。由于其燃烧室温度高和燃烧速度较低，CNG 发动机箱中的发动机壁传热也较高。汽油和压缩天然气之间的传热能量分数随着发动机负荷的增加而逐渐增加。发现在低运行负荷下的 CNG 情况下，排气能量最大，而在较高的发动机运行负荷下则降至最低。发现 CNG 发动机的未计算能量分数较低，并且相对于发动机负载降低。与汽油 (25.50%) 相比，CNG 在 30 Nm 负载下表现出最高的火用效率 (26.80%)。平均而言，在所有工作负载条件下，CNG 发动机的火用效率提高了 2%。这表明 CNG 具有将燃料中存在的化学能转化为有用功输出的更高潜力。与汽油相比，CNG 在所有工作负载下显示出更低的火用破坏，并且在更高的发动机负载下显着降低。在所有工作负载中，