Diesel engines are primarily used in the power generation sector owing to their characteristics of high efficiency and power, but account for higher emissions, mainly NOX and PM. Ethanol being a bio-based alternate fuel, holds the potential to be one of the most promising fuels for blending with diesel for emissions reduction, primarily due to its oxygenated nature, which results in a lower carbon content than diesel. In this study, four different ethanol-diesel blends have been developed for investigation (a) 5% (v/v) ethanol/diesel blend (E5D95), (b) 10% (v/v) ethanol/diesel blend (E10D90), (c) 15% (v/v) ethanol/diesel blend (E15D85) and (d) 20% (v/v) ethanol/diesel blend (E20D80). Additives and couplers were developed, as well, to address the problem of corrosion, cetane number reduction and blend stability. A detailed physico-chemical characterization was performed to measure various critical properties (density, cetane number, calorific value, flash point, etc.) of various diesel-ethanol blends. Also, all the blends were subjected to the stability test to understand the solubility and separation of ethanol and diesel at various temperatures. Subsequently, detailed experiments were conducted to understand the combustion and engine-out emission characteristics of ethanol–blended diesel fuels. A four-stroke, naturally aspirated, three-cylinder mechanically operated direct-injection diesel engine was used in this regard. Being a stationary Genset engine, D2-5 mode test as per ISO 8178 part IV was conducted at 1500 rpm. Engine brake power, torque, specific fuel consumption, inlet air flow rate, exhaust gas temperature, exhaust emissions, and the in-cylinder combustion, as well as fuel injection pump and injector end high-pressure line data were captured.
Performance of the tested engine with ethanol blending remained at par with the baseline diesel, however a reduction in the PM and gaseous emissions establishes ethanol blend as a favorable fuel solution for the tested CI engine. Experimental results indicate that, adding ethanol in diesel results upto a 6% reduction in the cycle NOx (for 20% blend) as compared to the baseline diesel; however, HC and CO were observed to have an increasing trend. A significant reduction of PM (~42%) was observed with 20% ethanol blending, as compared to the baseline diesel. The thermal efficiency was observed to be improved by 7% maximum with 20% ethanol blend. A meticulous analysis of the combustion data indicated no significant change in the in-cylinder pressure and the start of injection from baseline diesel to ethanol blends, at full load condition. However, at part load operation (below 50% load), peak firing pressure was reduced up to 6%, and the start of injection and combustion got retarded by ~2 deg, which deteriorated the thermal efficiency slightly. 5% ethanol blend came out as optimum for quick implementation in the existing engine perspective. Higher ethanol blend % is also possible for implementation, nonetheless the additional HC/CO emissions might have to be dealt with by a catalytic converter.
Keywords: Diesel-ethanol blended fuel, Alternate fuel, Physico-chemical properties, combustion and emission, NOX reduction, PM reduction