Abstract
Ethanol has significant potential for the reduction of fuel consumption and the emissions of engines. In this paper, a dual-fuel combined engine test rig with ethanol injected in the intake port and gasoline injected directly into the cylinder are developed and the effects of ethanol/gasoline ratio (Re) on the combustion and emission of particle numbers are investigated experimentally. The results indicate that the peak in-cylinder temperature (Tmax) decreases continuously with the increase of the ethanol/gasoline ratio (Re). For particle emissions, ethanol can significantly reduce the accumulation mode particle number (APN) at low engine speed; and the lowest number of particulates are at G25 (the gasoline ratio is 25% of the fuel) at low load. And at high engine load, the total particle number (TPN) is insensitive to speed with large ethanol fraction and TPN is relatively small. With the decrease of Re (Re < 50%), TPN rises sharply. When the direct injection timing advances, TPN reduces continuously and the effects caused by speed can be neglected. On the contrary, the speed has significant effects on particle emissions at various ignition times. At low speed, increasing ignition advance can cause the increase of the TPN; which is contrary to the effects of particle emissions at medium engine speed. And the effect of ignition timing at high speed on particle number is not obvious. The ignition timing for which the lowest TPN is reached will increase with the direct injection timing advances.
Highlights
In the context of the energy crisis and environmental pollution, it is important to find ways to alleviate the energy crisis and to reduce environmental pollutions
Huang et al [24,25,26,27] studied the effects of injection timing on the formation and combustion of the mixture on a combined injection engine using the mode of ethanol direct injection and gasoline port injection
The results of experiments are presented with two parts: the first part is the combustion and the second part is particle emission characteristics
Summary
In the context of the energy crisis and environmental pollution, it is important to find ways to alleviate the energy crisis and to reduce environmental pollutions. Wang et al [13,14,15,16,17] conducted a comparative study of n-butanol and gasoline combustion and particulate emissions in a spark ignition engine equipped with a combined injection system. Compared to gasoline direct injection engines, the dual-fuel engine’s compression ratio increased from 9.5 to 13.3 and achieved higher thermal efficiency. Zhuang et al [22] studied the flame zone characteristics of gasoline, ethanol and butanol in the early stage of combustion in a single-cylinder spark-ignition direct injection engine. Huang et al [24,25,26,27] studied the effects of injection timing on the formation and combustion of the mixture on a combined injection engine using the mode of ethanol direct injection and gasoline port injection. The control of particulates after ethanol was mixed with gasoline as an oxygen-containing fuel is obvious
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