Study On Combustion And Particle Characteristics Of Diesel Engine Fuelled With Methanol-blending Biodiesel Micro-emulsion Fuels

As the problems with emission laws and energy crisis getting increasingly severe, seeking renewable energy for replacing fossil fuel is becoming a research hotspot. Methanol and biodiesel have great prospects for using in engines because they are widely applied as renewable clean fuels. Biodiesel could directly apply in engine without changing mechanism for its intersolubility with diesel, but the physicochemical properties between methanol and diesel are greatly different, so it is very difficult to apply methanol in diesel engine directly. This thesis compounds methanol with biodiesel and diesel based on microemulsion theory, and does research on physicochemical properties and particle emission characteristics. The study provides theoretical basis for deep research on micro-emulsion fuels in the future.This dissertation compounded methanol-blending biodiesel fuels by selecting n-butyl alcohol as micro-emulsifiers based on microemulsion mechanism, and analysed the physicochemical properties. On a 186FA diesel engine, the performance experiments of methanol-blending biodiesel were carried out, especially on fuel efficiency, combustion and emission characteristics. The results show that, compared with blending biodiesel, as methanol proportion rising, there was a increasing trend of micro-emulsion fuels consumption of engine under the same working condition, especially running at the low load, the biggest amplitude reached 21.1%, but the gap was smaller at medium and high load; compared with blending biodiesel, the diesel engine of combustion pressure, pressure rise rate and heat release rate curves obviously retarded, the maximum pressure rise rate and heat release rate increased, the biggest amplitude reached 9.6% and 43.9% respectively. The HC emission of diesel engine increased gradually. Compared with blending biodiesel, the fuels mixed with methanol could effectively decrease CO、NOx and PM emission at the same time.With the EEPS particle size spectrometer, the particulate number concentration distribution characteristics were studied for a diesel engine fuelled with blending biodiesel and three different mixing proportion methanol-blending biodiesel micro-emulsion fuels. The results show that the particle presented nuclei mode and the size was mostly between 6 nm and 22 nm at low load; at high load, the particle number concentration distributions was unimodal with size between 6 nm and 275 nm, the particle morphology was accumulation mode, and the peak of particulate size distribution was around 100 nm. As the increase of methanol fraction, the percentage of nuclei mode particle raised while the accumulation mode particle decreased, the sum of exhaust particle declined.The study observed the exhaust particulates by SEM/TEM, and the influence of methanol-blending biodiesel on topographic characteristics of particulates was analyzed. The results show that, particulates of different fuels demonstrated catenulate、dendritic and cluster structures. And they became more compacted and size distribution of particulates was smaller as the methanol proportion increasing. In addition, the aggregation degree was larger.