Simulation Studies on Glow Plug Assisted Neat Methanol Combustion in a Diesel Engine

Methanol has a very low cetane number but it can be used in the neat form in a glow plug based hot surface ignition (HSI) engine at CI engine compression ratios. A CFD simulation model of a glow plug assisted methanol HSI engine was developed and validated using experimental data reported in literature. A study on the effect of single and multipulse injection of methanol, glow plug surface temperature, injection pressure and effect of shielding it were conducted by applying the model on to a three cylinder neat methanol HSI engine. A glow surface temperature of 1273 K was found to be sufficient for ignition of methanol at 50% load while the distance between the glow plug and the injector affected the ignition delay. The sprays were ignited sequentially starting from the one closest the glow plug which resulted in extended combustion. Injecting methanol in double pulses reduced the Maximum Rate of Pressure Rise (MRPR). It was desirable to inject 50% of the fuel in the first pulse at 50% load while this had to be reduced to 10% at 80% load for controlling the MRPR. At 80% load where auto-ignition of methanol was possible the glow plug could reduce the ignition delay and control the MRPR. Injection pressure affected the combustion process mainly due to changes in the injection duration. Thermal efficiency and THC levels were comparable to the base diesel values at 50 and 80% loads while the NOx emissions were lower at 80% load. A significant potential to lower the particulate levels was also observed.