Study On Combustion And Emission Performance Of Hydrous Ethanol Gasoline Combined Injection Engine

As a major automotive consumer,environmental pollution and energy shortages are more serious,and energy conservation and emission reduction are our current priorities.Ethanol has always been regarded as a reliable alternative fuel and has its own advantages.Nowadays,anhydrous ethanol gasoline is widely used in our country,but the energy consumed by dehydration and purification to anhydrous ethanol accounts for 30%-40% of the energy in the entire ethanol production process,which will still aggravate energy consumption.In this thesis,on an internal combustion engine that can be combined injection,gasoline intake injection is used,and hydrous ethanol is directly injected to study its combustion and emission performance.The variables involved in the test include alcohol ratio,water ratio in ethanol,injection timing,injection pressure,excess air ratio,speed,load and ignition advance angle.The main research work and test results are as follows:(1)In the combined injection engine test,it is determined that the best injection strategy for direct injection of ethanol is as follows: the proportion of direct ethanol injection is 20%,the injection pressure is 11 MPa,and the injection time is 120°CA BTDC.Then,when the ratio of ethanol remains unchanged,aqueous ethanol with different mixing ratios instead of anhydrous ethanol,the injection strategy of aqueous ethanol is determined as follows: the injection pressure is 9 MPa,and the injection time is 120°CA BTDC.(2)Under the above injection strategy,the effects of ignition timing and water mixing ratio on combustion and emission were studied.The result proves that at a suitable ignition timing,a small amount of water can improve the power and economic efficiency.With the increase of the water mixing ratio,the cylinder temperature can be reduced and the combustion phase can be delayed.At the same time,with the increase of water ratio,NOx emission can be reduced,which has little impact on CO and increases HC emission.As the ignition timing advances,the number of nucleation mode and accumulation mode particles increases.With the increase of the water mixing ratio,the particles first decrease and then increase.When the ignition advance angle is appropriate,the water mixing in the cylinder can be reduced at most 80% of particulate emission.(3)In the analysis of the influence of speed,load and water mixing ratio on combustion,it is found that as the water mixing ratio increases,the engine power and economy first increase and then decrease.With the increase of speed and load,the optimal water mixing amount is Increased.For the flame propagation in the cylinder,as the water mixing ratio increases,the flame propagation is inhibited,and as the speed and load increases,its influence is reduced.(4)In the analysis of the influence of speed,load and water mixing ratio on emission,it is found that as the load increases,CO emission decrease,and HC and NOx emission increase.As the speed increases,CO emission increase,and HC and NOx emission decrease.With the increase of water mixing ratio,TPN(Total Particle Number)first decreases and then increases at small loads,and keeps decreasing at medium and large loads.Under the conditions of suitable water mixing ratio,the amount of TPN can be reduced by 72.19%,60%,and 52.05% respectively under the three loads in the experiment,from small to large,and the main reduction is APN(Accumulation mode Particle Number).The particle emission trend is different with the increase of water mixing ratio at different speeds.At low speeds,with the increase of water mixing ratio,the total particle number first decreases and then increases.At medium and high speeds,it keeps decreasing with the increase of water mixing ratio.(5)In the analysis of the influence of water mixing ratio on emission under different excess air ratio,it is found that,in general,with the increase of water mixing ratio,CO emission remain basically unchanged,HC emission rise,and NOx emission decrease.Water mixing ratio has the greatest impact on HC and NOx during lean burn,and has the least impact on rich gas mixtures.With the increase of the excess air ratio,the number of TPN,NPN(Nucleation mode Particle Number)and APN has been reduced,from the power mixture to the lean mixture,the number of TPN has been reduced by more than ten times.In summary,the effect of using hydrous ethanol with a small water mixing ratio under a combined injection engine is better than that of anhydrous ethanol,which can improve combustion and reduce particulate emission.When a large proportion of water is mixed,NOx emission can be reduced,and particulate emission can be reduced under certain working conditions,but the power and economy are reduced.As the speed and load increase,the optimal water mixing ratio increases.