Study On The Characteristics Of Unconventional Emissions At Cold-Start In An SI Methanol Engine

Energy and environment issues always come out together, so we can not treat them separately. With the rapid and sustainable development of the national economy, more and more people have possessed their own car, and motor fuel consumption of the oil consumption has accounted for more than 35 percent of total. With the popularity of auto, energy and environmental issues have been a serious threat to China's sustainable development. Therefore, it is of great significance to strengthen the research of alternative fuel on the protection of the environment, reducing pollution and safeguarding national strategic oil security.As alternative fuel, the significance of the methanol is:(1) Methanol is an alternative to petroleum fuels. It can ease China's current oil shortage effectively, and reduce our dependence on oil imports to safeguard China's oil security strategy.(2) As oxygenated fuel, methanol can reduce engine emissions of conventional pollution, and has a positive role in the protection of the environment.(3) Methanol fuel has a wide range of sources. China is a big country of coal production, and coal is rich in resources. Using coal to get methanol, which process is simple, mature and low-cost, conforms China's current energy basic conditions. Physicochemical properties and thermal parameters of methanol is close to gasoline, and methanol also has potential to improve engine's air capacity and thermal efficiency. Therefore, methanol is a good alternative fuel for ignited engine.However ,methanol is a single component fuel ,and is lack of low boiling point components ,so it has a very large vaporization heat .The temperature of mixed gas drops much during vaporization process ,leading to more difficult in cold start of methanol engine than of gasoline engine .In addition ,there are unburned methanol and formaldehyde in methanol engine emissions ,which we call as unconventional emissions .They have a great pollution and harm to environment and humanity, therefore, they can not be overlooked. Many tests proved that conventional emissions in methanol engine is lower than gasoline engine, but unconventional emissions is far higher than gasoline engine.Emissions regulations of Vehicle engine emphasize increasingly on emissions control of the start-up conditions. The Euroâ…¢and Euroâ…£standard has cancelled 40 seconds warm-time which is after starting the engine.The experimental results show that, in the process of cold-start ,emissions is higher than that of stable condition, so it is necessary to optimize combustion and control emissions. In the country, there are a lot of research on gasoline engine start-up and emission characteristics, as a result, a common testing method has been established. However, the research on methanol engine is not more, so we need to control the emission rule through experiments, and propose control scheme. Through experiments, we can provide data and technical support for establishing national standards.Chromatography can separate different substances because they have different absorption coefficient in the two phases. As the technology has a high resolution and a wide range of application ,it has been widely used. The ability to separate mixture of complicated components and take a quantitative analysis is chromatography technology's biggest advantage. This advantage is appropriate to measure and analyze the unburned methanol and formaldehyde in exhaust. This paper attempts to use gas chromatography to separate formaldehyde and methanol, but tests have failed many times, so I redesigned a chromatography analysis method which combines gas and liquid chromatography method, and proved the method is feasible through experiments. Instruments used are the Shimadzu GC2010 and Waters 600E-HPLC.If experiment just use gas chromatography only, it is very difficult to make the choice of the column and its working conditions, and need a very long trial and exploration.In this thesis, a modified single-cylinder four-stroke 125 mL EFI engine was used to carry out a series of test which study the impact on the unconventional emissions of boundary conditions that include injection pulse width, jet and ignition time, and for blending LPG, fuel ratio and LPG jet time is also the conditions. With the analysis method of chromatography, the test measured and analyzed the composition of unconventional emissions in engine exhaust.The initial conditions'impact on unconventional emissions when preheated the inlet with electric heating plug and blended LPG fuel were studied by experiment. Test results show that:(1)Methanol engine's unburned methanol and formaldehyde emissions are contrary to the trend of changes, but there is no definite link in numerical between them.(2)With the method that inlet was preheated by electric heating plug, the emission of unburned methanol is high, and much higher than the formaldehyde emission.(3)With the method blending LPG, combustion of methanol fuel is very good. Unburned methanol emission is only 1/3 of method of preheating, but formaldehyde emission becomes nearly twice. At last, the emission account of unburned methanol and formaldehyde is very close.Through experiments, I found there are many factors that impact unconventional emissions, and the rule is very complex. Therefore, in the next step to optimize the control of unconventional emissions of methanol engine cold start, we need to consider all factors, and meanwhile ,we should also guarantee engine a reliable start performance.