Experimental Studies on the Use of Methanol-Butanol Blends in a Hot Surface Ignition Engine 2023-01-0316

The property of methanol to surface ignite can be exploited to use it in a diesel engine even though its cetane number is very low. Poor lubricity of methanol is still an issue and special additives are needed in order to safeguard the injection system components. In this work a common rail three cylinder, turbocharged diesel engine was run in the glow plug based hot surface ignition mode under different injection strategies with methanol as the main fuel in a blend with n-butanol. n-Butanol was used mainly to enhance the viscosity and lubricity of the blend. The focus was on the effect of different injection strategies. Initially three blends with methanol to n-butanol mass ratios of 60:40, 70:30 and 80:20 were evaluated experimentally with single pulse fuel injection. Subsequently the selected blend of 70:30 was injected as two pulses (with almost equal mass shares) with the gap between them and their timing being varied. Finally the effect of mass share of the injection pulses was evaluated. All the experiments were done at a speed of 1800 rpm, Brake Mean Effective Pressure (BMEP) of 8 bar and injection pressure of 850 bar and performance, emissions and combustion parameters were analyzed.

Higher methanol shares increased the efficiency because of controlled combustion rates and proper combustion phasing. Enhancing the methanol share, due to its high latent heat of vaporization lowered the temperatures and the Oxides of Nitrogen (NO_x) levels with near zero smoke levels. However, Hydrocarbon emission (predominantly formaldehyde and methanol) was found to be higher but it was possible to reduce it by using a diesel oxidation catalyst. Double pulse injection resulted in an improvement in the brake thermal efficiency due to better combustion phasing. Reduced the rate of pressure rise and NO_x emissions were also observed. An almost equal share between the two injection pulses was found to be acceptable and the efficiency was better than the base diesel engine with negligible smoke and lower NO_x levels.