The Simulation Research On Combustion And Exhaust Emissions Characteristics Of Direct Injection Diesel Engine Fueled With Methanol

It’s urgent to search for a high quality alternative fuel to replace the petroleum fuel asthe energy problem and environment problem become more and more serious, methanolcome into public’s view because of it’s a series of advantages, such as high octane number,anti-knock characteristics, high speed flame propagation. The effect of injection nozzleparameters, ignition timing and injection timing as well as the exceed air coefficient ondirect injection diesel engine fueled with methanol was simulated and investigated with aview to make a clear of physical and chemical reaction in diesel cylinder in this paper, inaddition, this paper also makes a contrast with the thermal efficiency of compression ratioof14,15and16. The conclusion as follows:1. The performance and exhaust emissions characteristics of direct injection dieselengine fueled with methanol will deteriorate if using conventional diesel engine injectorswith less injector holes, another reason of this is that methanol has low latent heat ofvaporization, because of above reason, it’s difficult to form high quality density mixturearound the spark plug and it will lead to poor flame propagation. The preferable densitymixture can be formed when the ten holes nozzles and in-cylinder swir match accurately, sothe performance and exhaust emissions of the injection diesel engine can be improved withshort ignition delay and fast flame propagation.2. The direct injection diesel engine fueled with methanol will work unstable whenthe methanol injected too much because of high compression ratio, so the air coefficientplay a vital role in the performance and exhaust emissions characteristics. When the aircoefficient λ=1.5, the in-cylinder pressure is high because of large amount of methanolinjected, the quality of flame propagation is improved, the in-cylinder temperature increasestoo much, Because of all above, the NO exhaust emissions increases and the CO exhaustemissions as well as SOOT exhaust emissions decrease. When the air coefficient λ=5, the in-cylinder mixture is too lean to form preferable density mixture under the impact ofin-cylinder swir density, this lead to less NO exhaust emissions while the SOOT exhaustemissions and CO exhaust emissions increase.3. Both methanol injection timing and ignition timing have a significant effect onmethanol engine performance, combustion, and exhaust emission. The flame propagationdeteriorates regardless the ignition timing and injection timing advance or retardexceedingly. Much leaner mixture around spark plug formed if the ignition timing advancestoo much; the homogeneous level increases and leaner mixture formed around spark plug ifthe ignition timing retard exceedingly. The homogeneous level also increases and leanermixture formed around spark plug if injection timing advanced too much at ignition timing.The methanol evaporates less and leaner mixture formed if injection timing was retardedexceedingly resulting in unfavorable performance and exhaust emissions characteristics.4. Higher in-cylinder pressure, higher the maximum heat release rate and much moreNO exhaust emissions as well as less CO and SOOT exhaust emissions are obtained athigher compression ratio when the air coefficientλis small in compared with lowcompression ratios. The distinction of all parameters presented above among differentcompression ratios is obvious when the air coefficientλis small. In addition, higher thermalefficiency is obtained at higher compression ratio when the air coefficient λ is small;Although Higher in-cylinder pressure, higher the maximum heat release rate and muchmore NO exhaust emissions as well as less CO and SOOT exhaust emissions are alsoobtained at higher compression ratio when the air coefficient λ is big, The distinction of allparameters presented above among different compression ratios is unconspicous. Inaddition, higher thermal efficiency is obtained at lower compression ratio when the aircoefficient λ is big.