Experimental Investigation on the Effect of using gasoline with commercial additives on Spark Ignition Engines performance and Emissions Characteristic

Gasoline is the primary source of energy in combustion engines, despite some drawbacks, such as knocking inside the engine, incomplete combustion, and the production of high emissions. The main trend has been toward the use of chemical additives as improvers, including oxidizing additives and aromatic hydrocarbon compounds. Both additives have an effect on the combustion process. Oxidizing additives improve the combustion process inside the chamber by adding additional oxygen to the fuel, which helps accelerate flame propagation, such as ethanol and oleo-octane plus. On the other hand, aromatic additives are used to increase the octane number, which in turn enhances the thermal stability of the fuel, such as toluene and cyclohexane (Thermol-p), but they can also increase the exhaust temperature. In this research, a practical experiment was studied using a 4-stroke single-chamber air-cooled gasoline engine with five fuel additives, one of which was at double concentrations. To study the BTE, BSFC and exhaust emissions from each of them at four loads (no load, 1000, 2000, 3000, 3500) kW and a constant engine speed of about 1500 RPM . The 50mm ethanol blend achieved the highest BTE of 22.98% compared to 18.68% for conventional gasoline (a 23% improvement), and the lowest BSFC of 396g/kWh compared to 484g/kWh (a 18.2% decrease). This was followed by the 100mm toluene blend with an efficiency of 24.01% (+28.5%) and a BSFC of 378g/kWh (-21.9%). In terms of emissions, the HC oxygenate additives reduced emissions by -42.9% (ethanol: 12.75 ppm versus gasoline: 22.35 ppm), while Thermol-P increased emissions by +31.8% (29.48 ppm). NOx increased by +40% with toluene (2040 ppm vs. 1458 ppm for gasoline), while remaining moderate with ethanol (1542 ppm). CO2 emissions remained roughly constant (0.05%), while CO₂ increased with ethanol (10.62%) and toluene (10.81%) compared to gasoline (9.64%). The results show that ethanol offers the best balance between performance and the environment, while toluene significantly enhances efficiency but increases NOx, while Thermol-P performs poorly in terms of emissions.