Experimental Study On Gasoline Direct Injection Engine Fueled With Toluene Reference Fuel Containing Alcohols

Because of the fierce impact of new energy vehicles and the gradual aggravation of energy and environmental problems,conventional internal combustion engines are facing great challenges.In order to achieve efficient and clean combustion of internal combustion engine,finding and using renewable energy is a practical way.Among renewable energies,alcohol fuels have drawn much attention due to their extensive raw material distributions and excellent physical and chemical properties.Therefore,based on a modified direct injection gasoline engine,the experiments were conducted by blending the gasoline surrogate TRF with various alcohols to modulate the test fuel.Then,the combustion and emission characteristics of alcohols/TRF blends and dual fuel mode in a direct injection gasoline engine were explored.Firstly,using the n-propanol/TRF as the test fuel,the effects of npropanol proportion on combustion,emissions and thermal efficiency were studied.The results show that the PRTRF0.3 blend has an earlier ignition timing and a shorter flame development duration and rapid combustion duration.With the increase in n-propanol proportion,the indicated thermal efficiency increases and the emissions of CO,THC,alkanes,acetylene and aromatics decrease,and the particle geometric mean diameter(GMD)and the accumulation mode particles are also reduced.However,when the npropanol blending ratio is too high,the emissions of alkenes,aldehydes and particulate number will increase due to the higher latent heat of vaporization.Since the properties such as oxygen content,latent heat of vaporization,viscosity and lower heating value of alcohols with different carbon chain lengths are different,therefore,the combustion and emission characteristics of four kinds of straight chain alcohols(C2~C5)/TRF blends were compared and analyzed at the same blending ratio and oxygen content,respectively.The comparative analysis shows that n-butanol/TRF blend has the highest indicated thermal efficiency with the same blending ratio.As the carbon chain length increases,the CO and THC specific emissions as well as most unregulated gaseous emissions show the first decrease and then increase trend,and n-butanol/TRF blend has the lowest emissions.When the oxygen content of the blends is the same,the npropanol/TRF blend has the highest indicated thermal efficiency.Ethanol/TRF and n-propanol/TRF have lower CO emissions and higher NOx emissions,and ethanol/TRF has the highest THC emissions.With the increase of alcohol carbon chain length,the emissions of alkenes,acetaldehyde and acrolein decrease firstly and then increase,and the particle total number and the geometric mean diameter decrease significantly.In conclusion,n-Propanol and n-butanol are more suitable as alternative fuels for gasoline engines.In order to explore the potential of dual-fuel system for gasoline engine fueled with alcohol and TRF,this paper finally studied the combustion and emission characteristics of dual-fuel injection strategy with port injection ethanol and in-cylinder direct injection TRF.The higher latent heat of vaporization of ethanol leads to a decrease in thermal efficiency,and a further decrease with the increase of port injection ratio,but the indicated thermal efficiency can be improved by advancing the spark timing.With the increase of ethanol injection ratio,NOx,THC and most unregulated gaseous emissions decrease gradually.In addition,with the increase of octane number of direct injection fuel,the indicated thermal efficiency first decreases and then increases,and the emissions of regulated gaseous and major unregulated gaseous first increase and then decrease.