Research Of Combustion Properties Of Natural Gas And DEE With Multi-Point Spark Ignition Based On Rapid-Compression Machine

Since the advent of internal combustion engine, it changed the life of human beings,and became a powerful engine to promote the development of modern industrialcivilization, but it also brings very serious energy crisis and pollution. Therefore,research on the new oil alternative fuel for saving energy and reducing emissions isbeing paid more and more attention among each country.Direct injection technology and HCCI combustion technology are currently the mostpopular technologies in the field of internal combustion engine. Direct injection is thatby injecting fuel to the combustion chamber directly, the rich mixture will be formednear the spark plug, and becomes thinner gradually. This can make total air fuel ratioincreasing, and implement lean combustion, thereby reduce fuel consumption. But dueto the stratification of the fuel, the flame spreads from spark point to around. If there isonly one spark point, the speed of the initial combustion period will be too low, andcyclical variations will become serious. And the range that the mixtures can be ignited isrelatively narrow at lean burning. HCCI combustion can make lean mixture burningstably; it also can improve fuel efficiency and reduce NOXemissions at the same time,so it has attracted a great deal of attention. HCCI combustion, however, also has itsweaknesses, for example, it’s difficult to control the burning time and the knockingphenomenon is easy to occur. So it has not been widely promoted into practicalapplication yet.In order to solve this problem, this research intends to adopt the way of multi-pointignition. By installing multiple spark plugs in the combustion chamber, the fuel underthe condition of extremely lean still can be ignited easily. Multi-point ignition can formmultiple ignition core and flame propagation region, then it can obtain higher efficiencyof combustion heat release. This method not only can improve the efficiency of thecombustion in the initial combustion period, but also can shorten the whole combustionperiod, improve cycle fluctuations, expand the combustion limits.Therefore, this research intends to use natural gas and Di-ethyl ether (DEE) as fuels.Natural gas has many merits, conveniently used, good emission performance, abundantreserves, low running cost, high safety and so on, which is extremely promising if beingused into spark ignition engine. And it is regarded as a very promising clean fuel gas. DEE is very easy to be ignited spontaneously, which is beneficial to be used in HCCIcombustion because it has high energy density, high cetane number, good compressioncharacteristics, low viscosity and high volatile nature.The Rapid Compression Machine (RCM) is used to simulate the intaking,compression, expanding process of an actual engine, and a combustion system is built,which is close to the actual direct injection engine. The applied basic research aboutmulti-point spark ignition combustion experiment and HCCI combustion experiment isdid, the result of combustion period, the characteristics of pressure, the component ofemissions and combustion efficiency are analyzed and compared. The main conclusionsof this research are: multi-point ignition can expand the limit of combustion and ispossible to improve combustion rate. It also can shorten the initial combustion period atlow equivalence ratio. And the probability of knocking is restrained.