Study On Combustion And Emission Characteristics Of Isopropanol-butanol-ethanol(IBE)/Gasoline Combined Injection Engine

With the progress of the automotive industry,vehicles not only facilitate human journey,but also bring a series of environmental and energy issues that need to be effectively addressed.On the one hand,China’s environmental departments have formulated strict regulatory requirements to curb environmental issues;On the other hand,China’s increasingly serious import dependence on oil resources has also attracted the attention of the national security department.In order to solve these problems,finding alternative fuels is a practical and effective measure.As an emerging renewable fuel,IBE not only retains the good physical and chemical properties of alcohol fuels,but also has the characteristics of low production cost and convenience for its wide application.Studies have shown that the combustion characteristics of IBE are similar to those of n-butanol.And it has good dynamic performance and can effectively reduce emissions.As an intermediate product of the fermentation ABE process,IBE can reduce the corrosion of the engine.Based on the port injection+direct injection combined injection technology was widely used,this thesis explores the effect of IBE and gasoline on engine combustion and emission characteristics under different injection modes through bench tests,so as to determine which is the best mode for the application of IBE in ignition engine.In this optimal injection mode（port injection gasoline+direct injection IBE mode）,the effect of direct injection ratio on engine combustion and emission characteristics was studied under different ignition advance angles and excess air ratio,which is determined for the optimal ratio range of direct injection for IBE in ignition engines.The research process and conclusions of this thesis are as follows:（1）Research on the influence of IBE/Gasoline injection mode on engine combustion and emission characteristics.To research the optimal injection mode of IBE/Gasoline in a combined injection engine,port injection IBE+direct injection gasoline（I+G）mode and port injection gasoline+direct injection IBE（G+I）are selected.The two combined injection modes are compared,and the pure gasoline combined injection（G+G）mode is introduced as a comparison standard.Through the engine bench test,the change law of the engine combustion and emission characteristics of the three injection modes was studied under different direct injection timing,ignition advance angle,λ,speed and load as well as the effect of adding IBE on the engine combustion and emission characteristics,so as to determine the optimal injection mode of IBE/gasoline in combined injection engines.The results show as follows:1)When the direct injection timing is 300°CA BTDC,the average indicating pressure in G+I mode is 47.83%and 40.92%higher than that in G+G and I+G injection modes respectively.In most operating conditions,the average indicating pressure of G+I mode is always the highest,followed by I+G mode,and the IMEP of G+G mode is the smallest.Whenλ=0.9 and 1.0,the peak cylinder pressure in G+I mode is higher than G+G mode and I+G mode,and can reach the peak cylinder pressure faster;whenλ=1.2,the peak cylinder pressure is lower than the G+G mode but still higher than the I+G mode in G+I mode.Due to the high laminar flame velocity of IBE,which can increase the stability of flame propagation,the Co V_IMEPof the port injection gasoline+direct injection IBE mode is always the lowest of the three modes under different operating conditions.2)For the emission characteristics,under most operating conditions,the G+I mode has the lowest NOx emissions,HC emissions,CO emissions,and particulate emissions among the three modes.Under the three injection modes,NOx emissions gradually decreased with the delay of direct injection timing;as the ignition advance angle increases,NOx emissions gradually increase,while HC emissions slightly increase;both HC and CO emissions continue to decrease with increasing rotational speed,while NOx is less affected by the speed changes.Increasing the excess air ratio can effectively reduce CO emissions in the G+I mode,while HC emissions will first decrease and then increase as the excess air ratio increases.In the G+I mode,simultaneously with the delay of direct injection timing,the number and concentration of nuclear film and accumulated particles increase.With the delay of the direct injection timing,the particle emissions of G+G and I+G modes first increases and then decreases.3)By comparing the combustion and emission characteristics of the engine under three modes,it can be concluded that the port injection gasoline+direct injection IBE（G+I）mode is beneficial to improve engine combustion and has lower gaseous emissions and particulate emissions under different operating conditions,making it the best supply mode for the IBE/gasoline combined injection mode.（2）Study on the effect of direct injection ratio on combustion and emission characteristics of a port injection gasoline/direct injection IBE engine.Under the optimal injection mode of port injection gasoline+direct injection IBE,the effects of different IBE direct injection ratios on the combustion and emission characteristics of the port injection gasoline/direct injection IBE engine were investigated through engine bench tests using different ignition advance angles and excess air ratio.Research shows:1)For combustion characteristics,under different excess air ratio and ignition advance angles,large proportion of direct injection IBE can increase the average indicating pressure of the engine as well as the utilization ratio of cylinder working volume,and improve combustion efficiency.When the ignition timing is 10°CA BTDC,λ=1.0 the IMEP of 100%IBE direct injection ratio is 10%higher than that of 0%IBE direct injection ratio,whileλ=1.2,13%higher.When increasing the IBE direct injection ratio,the ignition timing corresponding to the optimal ignition angle will gradually delay.In order to obtain a higher average indicated pressure,it is necessary to appropriately reduce the ignition advance angle while injecting a large proportion IBE into cylinder.With the increase of the proportion of direct injection IBE in the cylinder,the peak cylinder pressure gradually increases.When ignition timing=20°CA BTDC under operating conditions ofλ=1.0 andλ=1.2,the peak cylinder pressure of pure IBE injection is respectively 9.2%and 17.1%higher than that of pure gasoline injection.IBE has good lean burn performance.Under the lean burn conditions,a large proportion of IBE direct injection is beneficial to reducing cycle variability and improving engine combustion stability.2)For emission characteristics,whenλ=1.0,NOx emissions gradually decrease with the increase of IBE direct injection ratio;whenλ=1.2,NOx emissions first increase and then decrease with the increase of IBE direct injection ratio.Under different operating conditions,HC emissions decrease as the proportion of IBE direct injection increases.With the increase of excess air ratio,the reduction effect of IBE direct injection ratio on HC emissions is weakened.Whenλ=1.0,with the increase of IBE direct injection ratio,CO emissions shows a downward trend;whenλ=1.2,IBE direct injection ratio has little effect on CO emissions.Whenλ=1.0,the total particle emissions decrease with the increase of IBE direct injection ratio;whenλ=1.2,the total particle emissions first decrease and then increase with the increase of IBE direct injection ratio,20%～60%IBE direct injection ratio had the lowest particle emissions.To sum up,the combustion and emission performance of the engine is optimal at the proportion of 60%～100%IBE direct injection.