Study On Effects Of Hydrogen Addition On Combustion And Emission Of Ethanol/gasoline Engine

This study explored the characteristics of ethanol/gasoline fuel and hydrogen combined application on internal combustion engines from the perspectives of alternative fuels,energy saving and emission reduction through experimental method,in order to find the best fuel blending ratio under different operating conditions.During the test,ethanol and gasoline were mixed and stored in the fuel tank in different proportions.The mixed liquid fuel in the fuel tank was injected through the intake port,and the hydrogen was injected directly into the combustion chamber in the middle and later stages of the compression stroke through the high-pressure injector.The main operating conditions of the test include low and medium loads or speeds.This study is mainly divided into two parts.First,the relationship of combustion and emission data under various operating conditions with fuel blending ratio were explored,and then the relationship of the data about combustion and emission with fuel blending ratio were established through analysis of variance and regression analysis.According to the research work in the first part,the following conclusions could be drawn:(1)The adding of hydrogen has greatly improved the pressure in the cylinder and combustion speed,especially under lean combustion conditions.As the ratios of hydrogen increases,the effect does not increase proportionally.Under the optimal ignition advance angle,the torque shows an increasing trend with the increase of hydrogen ratio.Under the stoichiometric ratio,small hydrogen ratio can obtain higher improvement of torque,and under lean conditions,medium or high hydrogen ratio will obtain higher torque.The maximum value of the torque will move to the direction of higher hydrogen ratio as the increase of speed and the decrease of load.(2)The effect of ethanol on combustion speed shows multi-polar and varies with operating conditions.Under most operating conditions,the combustion speed of medium alcohol blended fuel is lower,and the torque is lower too.At the same time,increasing the load will make the maximum values of maximum combustion pressure move to the direction of higher alcohol blending ratio.(3)In terms of NO_x emissions,an increase in the alcohol blending ratio will lead to a decrease in NO_x emissions,while an increase in the hydrogen blending ratio will increase the NO_x emissions.The test results show that under most operating conditions,compared with 10% alcohol blending,the pure ethanol reduce NO_x emissions by more than 40% on average.Compared with 20% hydrogen blending,non-hydrogen can reduce NO_x emissions by more than 50% on average.The increase in speed and the decrease in load will reduce NO_x emissions.(4)HC emissions show a gradual decrease with the increase of the hydrogen blending ratio.HC emissions decrease first and then increase with the increase of the alcohol blending ratio,which obtain a minimum value at 70% to 90% alcohol blending ratio.The results show that a 20% hydrogen blending ratio can reduce HC emissions by more than 25% on average compared to nonhydrogen,and an 82% alcohol blending ratio can reduce HC emissions by more than 40% on average compared to a 10% alcohol blending ratio.(5)The CO emissions are mainly affected by the excess air coefficient.In addition,the CO emissions show a gradual decrease with the increase of the hydrogen blending ratio,and do not change significantly with the alcohol blending ratio.Small hydrogen ratio and medium alcohol ratio will get maximum CO emissions under most operating conditions.Particulate emissions show a significant decrease with the increase of alcohol blending ratio,and will increase when the ratio of alcohol blending is too large.The alcohol blending ratio is an important factor affecting the diameter of particles.The larger the ratio of alcohol is,the smaller the particle diameter.There is no obvious regularity with the change of hydrogen blending ratio.In the second part,the correlation between the combustion and emissions performance of the engine and the fuel blending ratio was determined by analysis of the variance through the test data,and the relationship between the combustion emissions performance of the engine and the fuel blending ratio was established through regression analysis.The relevant analysis conclusions are as follows:Statistical analysis shows that torque and harmful gas emission are not only related to hydrogen ratio and alcohol ratio,but also affected by the synergistic effect of the two.This also shows that the combustion and emission performance has a high-order nonlinear relationship with the blending ratios,and the regression model obtained shows a great change under different conditions,which indicates that the change of working conditions are the main reason of high-order relationship.At the same time,it can be seen from the comparison of the maximum points and minimum points that changing the fuel blending ratio can greatly change the engine's power and emission performance.Therefore,it is very practical to find the best blending ratio under specific conditions through the regression equation.