Experimental Study On Cold-Start Of Direct Injection Spark-Ignition Methanol Engine

Energy and environmental issues are big problems afflicting humanity now, and they areconcomitant. Since the second industrial revolution, extensive use of fossil fuels has made alarge of fossil energy consumption, and caused heavy pollution to the environment, whichleads to the environmental degradation. Especially the last hundred years, the generation ofthe automotive industry and its rapid development have exacerbated this situation. Accordingto statistics, car fuel consumption accounts for more than35%of the total oil consumption.Therefore the development of alternative fuels is imperative to mitigate the energy crisis.China is rich in coal but short of petroleum and gas, so developing methanol as alternativefuel for vehicle is in line with our national conditions.The significance of using methanol as an alternative fuel:(1) methanol can be used as avehicle energy to replace the petroleum products, which eases China’s oil crisis, reduces thedependence on imported oil, and ensure oil security;(2) methanol,which is an oxygenatedfuel, can reduce emissions of environmental pollution;(3) Methanol production has a widesource. China has a major coal power, so producing methanol from coal is in line withChina’s national condition;(4)The production, transport and storage technology of methanolis quite mature, and does not need to redevelop;(5) As an alternative fuel, methanol cancomplement China’s oil reserves and slow down the energy crisis.Because the methanol physical and chemical properties are similar to gasoline, theexisting engine systems does not need many transformations. And as an oxygenate fuel,ethanol can reduce the emissions. The octane value of methanol is higher than gasoline, sothe pure methanol engine has higher thermal efficiency and power output. When using methanol, with the lower conventional emissions, unconventionalemissions increases a lot. The unconventional emissions of methanol is mainly unburnedmethanol and formaldehyde. Methanol has a large latent heat of vaporization, which lead tocold start problems. So at cold start condition the unconventional emission increasessignificantly. Academia has mature solution to the cold start problems of methanol, but inthis paper the improvement of the direct injection to methanol cold start will be verified.The thesis has conducted the cold start experiment of direct injection methanol engineto solve the problem of methanol fuel’s cold start difficult. In order to study the performanceof direct injection methanol engine, this thesis has taken a four cylinder direct injectionspark-ignition engine as the experimental engine and established the experimental platform.Besides, the thesis has also built the acquisition and examination system of methanol andgasoline’s conventional emissions and the acquisition and examination system of methanol’sunconventional emissions through the combination of chromatographic analysis andspectrum analysis. The thesis has mainly adjusted the boundary conditions of the cold startworking condition of direct injection methanol engine and discussed the influences of eachboundary condition to the performance of methanol cold start. Besides the methanolexperiment, the thesis has also conducted gasoline cold start experiment under the samecondition as that of the methanol. And it has also made a comparative analysis between theperformance of methanol and gasoline’s cold start. Through the analysis of the experimentalresults, the thesis has got the following conclusions:1As a kind of alternative fuel, the conventional emission performance of methanol isprior to that of the gasoline. Under the working condition of cold start, the conventionalemission of methanol is lower than that of the gasoline. And the conventional emissionperformance of the former is just about one tenth of the latter. Hence, we can get theconclusion that as an alternative fuel, the use of methanol can achieve the aim of reducingconventional emission.2Methanol’s cold start is relatively poor. It is known that a relatively serious factor thatinfluences methanol cold star emission is the ambient temperature. Besides, through experiment, it is found that when the temperature is lower than6℃, it is hard to start thedirect injection methanol engine. Hence, air preheater system is necessary for the use ofdirect injection methanol engine in winter or in cold regions.3The cold start working condition of methanol is more economical than that of thegasoline. Through experiment, it is found that under the cold start working condition andwith the same equivalent carbon content, the number of start cycle of methanol is less thanthat of gasoline. Hence, we can get the conclusion that the startability and economicalefficiency of methanol is prior to that of gasoline.4. Methanol engine’s unburned methanol and formaldehyde emissions are contrary tothe trend of changes but there is no definite link in numerical between them. Under the coldstart working condition, unburned methanol emission is higher and methanol emission isabout one tenth of that of the unburned methanol. Hence, we can get the conclusion that inthe process of cylinder burning, unburned methanol occupies about one tenth of the totalamount of the response methanol.5The thesis has taken the combination of gas chromatography and spectrum analysis asits abnormal emission measurement method. Through experimental verification, it has beenfound that this measurement method has a relatively high precision, its error is within5%and its measurement method is feasible.