Research On Performance And Emission Of Hydrogen-gasoline SI Engine Based On Grey Relation Theory And Neural Network

The number of automobile in our country keeps rising year by year under the background of China’s rapid economic development.This makes the oil demand keeps increasing.But it has become an important factor in national economic development for a petroleum resource-poor country.Meanwhile,the air pollution from automobile exhaust has seriously affected the people’s life.Thus all over the word is working on the development of alternative fuels and reducing the automobile exhaust pollution.However,hydrogen can be used as an alternative fuel,and also can be added to gasoline engine to adjust the performance and emissions.So far,most of the literature about hydrogen-gasoline engine used the method of hydrogen/gasoline intake port injection.But the method of hydrogen direct injection and gasoline intake port injection has been used in this text.This method can effectively avoid backfire.Hydrogen injection process was simulated to find the best hydrogen injection timing.After that,bench tests were done for the hydrogen-gasoline SI(spark ignition)engine.The influences of hydrogen blending ratio,excess air ratio,spark advance and EGR(exhaust gas recirculation)ratio on the performance and emissions were analyzed.The grey relational degrees between each influence factor and the performance or emission parameters were calculated using the bench test data and the computing method of grey relational degree.Using the grey relative analysis method to analyze which factor has the greatest influence for each performance and emission parameters.Finally,neural network model was established.And it was used to forecast the performance and emissions of hydrogen-gasoline engine.The main conclusions were summarized as follows:With the increase of the spark advance,the NOX,HC and CO emissions increase.The minimum spark advance for best torque decreases with the increase of hydrogen blending volume fraction.With the increase of excess air ratio,the effective work gradually decreases,and the coefficient of variation of indicated mean effective pressure increases.The pressure rise rate and the coefficient of variation of indicated mean effective pressure decrease with the increase of hydrogen blending volume fraction.The increase of hydrogen blending volume fraction increase thermal efficiency and NOX emission,decrease unburned HC emission.Adding hydrogen to gasoline engine can reduce the coefficient of variation of maximum pressure and the coefficient of variation of indicated mean effective pressure.The coefficient of variation of maximum pressure and the coefficient of variation of indicated mean effective pressure are fall with the rise of spark advance.When using EGR,the increase of EGR ratio reduces NOX emissions significantly,and increase HC emissions.The peak of instantaneous heat release rate reduces with it,the corresponding phase of its peak also gradually postponed.The coefficient of variation of indicated mean effective pressure first decreases,and then increases.However,the effect of hydrogen blending energy fraction on coefficient of variation of indicated mean effective pressure is more obvious.Without EGR,the excess air ratio is principal element influencing the torque and power.Hydrogen blending ratio,excess air ratio and spark advance effect on CO emission are almost the same and are larger.The influence of excess air ratio is the largest for CO2 and HC emissions.The impact of hydrogen blending ratio on NOX emission is the biggest of the three factors.When using EGR,hydrogen blending ratio is principal element influencing the torque and power.Hydrogen blending ratio,EGR ratio and spark advance effect on CO emission are big and small difference.For CO2 emission the influence of hydrogen blending ratio and spark advance are basically the same.But it is little bigger than the influence of EGR ratio.For HC and NOX emissions the influence of spark advance is the largest.Compare to hydrogen blending ratio and spark advance the impact of EGR ratio on NOX emission is lower.BP(back propagation)neural network model is used to predict performance and emission of hydrogen-gasoline engine,and the prediction results were analyzed.Withthe increase of hydrogen blending ratio and the decrease of spark advance the torque of hydrogen-gasoline engine increase under the condition of excess air ratio is 1.5.Meanwhile,with the decrease of hydrogen blending ratio and the increase of spark advance the HC emission increase.However,with the increase of hydrogen blending ratio and spark advance the NOX emission increase.When using EGR and the hydrogen blending ratio is 25%,the torque is fall with the rise of EGR ratio under the condition of smaller spark advance.But the torque is rise with the rise of EGR ratio under the condition of bigger spark advance.With the rise of spark advance and EGR ratio the HC emission rises.With the decrease of spark advance and the increase of EGR ratio the NOX emission decreases.