Simulations of methanol fueled locomotive engine using high pressure co-axial direct injection system

Abstract

Methanol has emerged as a strong alternate fuel candidate, which can meet future fuel requirements for locomotive traction. Simulation approach is an excellent tool for preliminary technical feasibility assessment of alternative fuels compared to time consuming experiments. The objective of this study was therefore to assess the feasibility of 90% diesel displacement by methanol (on energy basis) in the ALCO-251 locomotive engines, the workhorse of Indian Railways (IR). In the first phase of this study, base model of ALCO-251 locomotive engine was prepared in 1-D simulation software (GT-Power), which was validated using the experimental data of mineral diesel provided by Research Designs and Standards Organization (RDSO), which is the R&D wing of IR. Locomotive engine works on eight different engine speeds at different notches: 350 rpm (1st Notch), 450 rpm (2nd Notch), 550 rpm (3rd Notch), 650 rpm (4th Notch), 750 rpm (5th Notch), 850 rpm (6th Notch), 950 rpm (7th Notch), 1050 rpm (8th Notch). In the second phase of the study using this validated model, a co-axial injector was used where methanol was used as the primary fuel, and diesel was used as the secondary fuel for pilot injection using Co-axial High Pressure Direct Injection (HPDI) method. For simulations, methanol and diesel injectors were housed in a single injector body of the co-axial injector, but they had individual controls. Co-axial injector was actuated such that first it injected diesel in hot air-environment to initiate the combustion, followed by injection of methanol as the main motive fuel. Base model simulated the engine performance, emissions, and combustion characteristics quite well, which were in good agreement with the experimental data. Pareto optimized dimensions of the co-axial injector were 0.486 mm nozzle hole diameter, and 3 holes for pilot diesel injection, and 0.544 mm nozzle hole diameter, and 5 holes for methanol injection. HPDI of Methanol with Pilot Diesel Injection Model with optimized injector dimensions exhibited in-cylinder pressure curve shapes similar to the base model with similar/ superior torque characteristics, higher brake thermal efficiency, and lower NOx emisssions. Inevitably, 1-D simulation for the locomotive engine represented a potential method to achieve similar/ better engine performance, combustion and emission characteristics via this new fuel injection concept, using high pressure co-axial direct injection system.