Experimental Study Of Gasoline Configuration For Optimizing The Performance Of Engine

Energy resource and environment protection are a worldwide-concerned issue,which has been attached great importance by all sectors of society.Various countries have enacted emissions regulations,fuel consumption regulations and fuel standards.The automotive industry has also been devoted to save fuel and reduce emissions.However,the fuel consumption regulations and fuel standards have been more stringent,making the automotive manufactures and petrochemical corporations face severe challenges.In addition,the automotive industry has accumulated much experience about emission-reducing,while there are little researches about fuel economy optimization.The technological level of refinery process and fuel standards of China are different with these of other countries to some extent.Therefore,it is necessary to study and explore gasoline composition that corresponds with Chinese markets and ability of fuel production.Furthermore,it could also provide reference for the enactment of fuel standards of China in the next stage.This paper presents a study about the effect of gasoline composition on fuel economy,combustion and emissions.Firstly,the experiment was conducted in a turbocharged gasoline direct injection(GDI)engine with the displacement being 1.4 liter.To investigate the effect of the length of chain alkane on combustion and emissions,isooctane was selected as the base fuel,blended with short-chain,medium-chain and long-chain alkanes for comparison tests,respectively.Then the short-chain alkane,aromatic and oxygenated fuel were blended with isooctane respectively for the experiment aiming to study the effect of different group of gasoline composition on fuel economy,combustion and emissions.Results as below:(1)Medium-chain and long-chain alkanes are beneficial for the improvement of combustion velocity,shortening the ignition delay and advancing combustion phase.Overall,short-chain,medium-chain and long-chain alkanes,to some extent,could reduce CO and THC emission but they cannot obviously reduce NOx emissions.(2)Under all operating conditions,shot-chain alkane could improve ignition stability and combustion velocity due to the lower octane number,which benefits shortening ignition delay and optimizing combustion process.Nonetheless,the impact of octane number become weak under heavy load conditions,leading to the better performance of oxygenated fuel to optimize combustion process.(3)Compared to pure isooctane,blended fuels are able to reduce CO and THC emissions,but there is no obvious advantages in decreasing NOx emissions.(4)Under all operating conditions,aromatics have a good impact on fuel economy due to the higher density,lower heat value and energy density.20%toluene(20% toluene blended with isooctane)shows the lower break-specific fuel consumption(BSFC)whose maximum fuel saving ratio(FSR)and average FSR could reach to 5.42% and 2.75%,respectively.And it shows balanced ability to save fuel consumption in different speed and load regions.Under the condition of low speeds,small and medium loads,20%n-pentane(20% n-pentane blended with isooctane)shows lower BSFC with the maximum FSR being 4.64%,which means short-chain alkane has good potential to reduce fuel consumption due to better combustion stability.By contrast,20%MTBE(20% methyl tertiary butyl ether blended with isooctane),whose average FSR is-2.75%,shows the higher BSFC for its higher cyclical variation and lower heat value.Lastly,commercial gasoline with research octane number of 92 and three customized gasoline with different aromatics,short-chain alkanes and oxygen contents were chosen to conduct comparative tests in a natural aspirated port fuel injection(PFI)engine with the displacement being 1.6 liter,so as to verify the validity and universality of the conclusions from previous experiment.Based on the previous results,gasoline F with higher aromatic content aims to improve fuel economy under all operating conditions and gasoline L with higher shotchain alkane content intends to decrease fuel consumption under specific conditions.In conclusion,the results from the PFI engine are consistent with the results from the GDI engine,which has verified the validity and universality of the conclusions from the GDI engine.Results as below:(1)The mean FSR of gasoline F under all operating conditions are 3.68% while the mean FSRs under stable conditions could reach to 5.25%.And the mean FSR of gasoline L under medium and light load conditions at medium speeds could reach to 4.29%.Gasoline E with higher oxygen content and lower aromatic content,whose mean FSR under all operating conditions is 1.55%,shows better performance of fuel economy than gasoline L.(2)As for emissions,three customized gasoline present similar tendency with commercial gasoline.Gasoline L and F could reduce CO and THC emissions under stable operating conditions.Gasoline E is able to balance fuel economy and emissions because it could reduce CO,THC and NOx emissions to some extent,with the performance of fuel economy being well.