Development Of Electronic Control System And Study On The Emission Characteristics Forthe Methanol/Diesel Dual-Fuel Engine

In present,the contradiction between supply and demand of crude oil is becoming more and more serious,and the environmental problem is worsening,while the increase of vehicle population further aggravates these problems.Therefore,it is necessary to study new alternative energy(new fuels and electric vehicles),in which the application of new fuels needs some refits of conventional internal combustion engines,such as natural gas,alcohol fuels and alkanes.As a kind of new alternative energy,methanol has higher thermal efficiency,and its power performance and economy are better,the research of methanol has a good prospect.In this paper,the port fuel injection methanol/diesel dual-fuel engine was studied.In this paper,a high pressure common rail diesel engine was refitted.The methanol injector was installed in the diesel engine intake manifold,and a methanol/diesel dual-fuel engine test bench was built.Through the existing dual-fuel ECU the injection of diesel was controlled.Methanol injection adopts multi-point sequential injection,and the development of methanol/diesel dual-fuel engine methanol injection electronic control system achieves the control of methanol injection.The methanol injection electronic control system includes two parts: lower computer control system and upper computer software.Lower computer control system receives and processes the signal of camshaft position sensor,and makes the signal identified by a single chip microcomputer.Then the engine speed could be calculated by the signal.And by artificial control lower computer control system can receive the injection timing and injection pulse width of methanol injection by using the serial communication,which can control methanol injection.At the same time,the methanol injection electronic control system can control that some methanol injectors inject methanol or not,which is used to do the cutting out methanol experiment.There are five modules in lower computer control system which includes two Atmega128 single chip microcomputers,MAX3232 transceiver,MAX9924 sensor signal process chip,LM2576S-5.0 regulator,IR2101 and IRF3415 driver IC.Then the hardware circuit was designed.And the control software of lower computer control system was developed.The upper computer software sends control parameters by anthropogenic input to the lower computer control system which is used to control the methanol injection.And the upper computer software can display the engine speed and the return value of methanol injection pulse width and timing.In addition,circuit board and shell of the lower computer control system were manufactured.Then the operation test of the methanol/diesel dual-fuel engine methanol injection electric control system was conducted after the design and development of the electric control system.Furthermore,the emission characteristic of methanol/diesel dual-fuel engine was researched experimentally on the test bench which has been built.The results show that the effect of methanol injection timing has a little effect on the emission characteristics,and has a large impact on HC emissions relatively.In addition,its impact on the fuel economy is not significant.Diesel injection timing has a greater impact on emissions characteristics and fuel economy.With the increase of diesel injection timing(fuel supply advance angle increases)under test set conditions,HC and CO emissions are reduced.Smoke is reduced,while NO_x emission increases and fuel economy is better.The effect of the co-combustion ratio on the emission characteristics was been studied in two modes(cutting out methanol mode and normal dual-fuel mode).In the normal dual-fuel mode,the increase of the co-combustion ratio can make the combustion worse and the HC and CO emissions increase,while the smoke and NO_x Emissions are reduced.In the mode of cutting out methanol,the effect of co-combustion ratio on HC and CO emissions is declining as a whole.The smoke slightly increases first and then decreases,while NO_x increases.Compared to the normal dual-fuel mode,HC and CO emissions dropped significantly and completely lower,the smoke has an improvement to some extent,while NO_x is slightly higher.The brake specific fuel consumption of cutting out methanol is totally lower than that of normal dual-fuel at the same co-combustion ratio.In general,cutting out methanol can significantly improve the emission characteristics and economy of the methanol/diesel dual-fuel engine at low loads.