An Investigation Of Methanol Fuelling For Compression Ignition Engines

Methanol derived from biomass, coal and natural gas presents a promising alternative to substitute fossil fuels. However, the low cetane number of methanol makes autoignition difficult so that direct application of methanol to diesel engines is hard. To apply methanol into the diesel engines, the concept of a diesel methanol compound combustion (DMCC) has been proposed. In the modified diesel engines, methanol has been injected into the intake air fumigation to form the homogeneous mixture ignited by pilot diesel fuel.The system was firstly tested on two naturally aspirated and a turbocharged engine. The experimental results show that, at low loads, the brake thermal efficiency decreases with increase in fumigation methanol; but at high loads, it increases with increase in fumigation methanol. The fumigation method results in a significant increase in HC, CO, and NO2 emissions. The concentration of NOx is significantly reduced except at close to full load condition. There is also a reduction in the smoke opacity and the particulate matter (PM) mass concentration. For the submicron particles, the total number of particles decreases at low and medium loads but increases at high loads. In all cases, there is a shift of the particles towards smaller geometrical mean diameter, especially at high loads.Secondly, The DMCC system also applied to a naturally aspirated diesel engine with and without an oxidation catalytic converter. The combustion and emission characteristics were compared. A preliminary investigation of formaldehyde emission was conducted on the engine. In the DMCC system, there are two combustion modes taking place in the diesel engine, one is diffusion combustion with diesel fuel and the other is premixed air/methanol mixture ignited by the diesel fuel. Experiments were conducted at idle and at five engine loads at two levels of engine speeds to compare engine emissions from operating on pure diesel and on operating with DMCC, with and without the oxidation catalytic converter. The experimental results show that the formaldehyde emission of engine-out increase compared with the baseline. Using the DMCC mode coupled with an oxidation catalyst, the CO, HC, NOx and soot emissions could all be reduced.Diesel fuel can also be replaced by biodiesel made from waste-cooking oils. The third section of the study is aimed to investigate the effects of fumigation methanol on Experiments were performed on a 4-cylinder naturally aspirated diesel engine operating at a constant speed of 1800 rev/min for three engine loads. The results indicate no significant change in brake thermal efficiency and CO2 emission, an increase in both CO and HC emissions, and a decrease in both NOx and PM emissions. In particular, there is also an increase in NO2 in the exhaust gas. The results obtained with fumigation of 10% methanol are compared with those for ultralow sulfur diesel: There is an increase in CO and HC, by a factor of up to two, and an increase in NO2, by a factor of up to five, while the NOx is reduced by up to 8% and the particulate mass is reduced by up to 50%, depending on the engine load.The forth part of this study is also aimed to compare the effect of applying a biodiesel with either 10% blended methanol or 10% fumigation methanol. Experiments were performed on a 4-cylinder naturally aspirated direct injection diesel engine operating at a constant speed of 1800 rev/min with five different engine loads. The results indicate a reduction of CO2, NOx, and particulate mass emissions and a reduction in mean particle diameter, in both cases, compared with diesel fuel. It is of interest to compare the two modes of fueling with methanol in combination with biodiesel. For the blended mode, there is a slightly higher brake thermal efficiency at low engine load while the fumigation mode gives slightly higher brake thermal efficiency at medium and high engine loads. In the fumigation mode, an extra fuel injection control system is required, and there is also an increase in CO, HC and NO2 and particulate emissions in the engine exhaust, which are disadvantages compared with the blended mode.Finally, the performances of the passenger car powered by a DMCC engine have been evaluated. The results show that methanol can displace diesel fuel up to 35.1%, meanwhile, fuel economy and acceleration have been improved.In conclusion, methanol has been successfully applied to diesel engines to partly substitute diesel fuel. There are improvements in the engine efficiency and exhaust emissions compared with the baseline engines at some conditions. DMCC system retrofitted into diesel engines has significant implication to the socioeconomic benefits of China because methanol can be derived from coal which is abundant in China.