Experimental Investigation on Performance and Emission Characteristics of a Single Cylinder CRDI Engine Fueled with Diesel-Methanol Blend

摘要

Diesel engine is widely used for its high thermal efficiency and better fuel efficiency. However, increasing usage of petroleum fuel and environmental degradation motivates to use renewable biofuel as a replacement to conventional diesel. Biofuel produced from non-edible sources can be used as a partial substitute of diesel for the significant growth of fuel economy and reduction of environmental pollution. Methanol can be implemented as a blend fuel in the diesel without affecting engine design. In this paper, we study the effect of diesel-methanol blends and injection parameters in particular, start of injection (SOI) and fuel injection pressure (FIP) on a common rail direct injection (CRDI) diesel engine performance and emission were investigated. Four blends were prepared by mixing diesel with methanol (5%, 10%, 15% and 20% by mass) and adding a certain amount of oleic acid and Iso-butanol to get a stable blend. Experiments were performed at an engine speed and load of 1500 rpm and 15 Nm, respectively. FIP governs air-fuel mixture preparation and fuel atomization which control combustion behavior of the engine, whereas SOI was chosen to optimize the combustion delay affecting the overall performance. Results show that the trend of optimum SOI retards 15°, 12° and 5° CA bTDC with the increase in FIP of 200, 300 and 400 bar respectively. However, this does not hold good for M15 and M20 blend at 400 bar FIP due to ignition delay at higher fraction methanol blend. In comparison to baseline diesel, brake specific fuel consumption (BSFC) increases in diesel-methanol blend, which reduces the brake thermal efficiency (BTE). Methanol blend shows a significant impact on the reduction of smoke opacity in all blend fraction compared to baseline diesel operation. This further reduces on advancing SOI and increase in FIP. This mainly attributes the presence of oxygen molecule in methanol as well as sufficient time availability for air-fuel mixing. Higher spray penetration at high FIP removes the deficiency of local oxygen concentration in different regions of the combustion chamber. CO emission shows a negative impact on performance output at all blend fraction, which reduces on advancing SOI and increasing FIP. HC emission shows a similar trend to that of CO, however, at high FIP for all blend fraction, HC emission is lower than the baseline engine due to better mixing and more oxygen availability. The results indicate that methanol blend is an encouraging alternative for lower smoke at the cost of CO and HC emissions. Altogether, it is concluded that diesel-methanol blends can be suitably used in CRDI diesel engines after making a good trade-off between performance and emission.