Study On The Influence Of Ignition Timing And Hydrogen Injection Pressure On The Performance Of Hydrogen-doped Gasoline Engine

In the context of the current energy transition in China and the establishment of the "carbon peak and carbon neutral" target,the development of new clean renewable energy sources as alternative fuels for automobiles is the way forward for the long-term development of the automotive sector.Due to its renewable,environmentally friendly,fast combustion,good propagation and high calorific value per unit,hydrogen has great potential for application in the field of internal combustion engines and has a very bright future for development.Numerous studies have shown that the ignition advance angle has a great influence on the dynamics,economy and emissions of hydrogen-doped petrol engines,and that the hydrogen injection pressure affects the state of the in-cylinder mixture formation and thus the combustion state of the engine.This article takes a dual fuel engine with inlet hydrogen injection and cylinder injection as the research object,establishes a three-dimensional simulation model for the inlet hydrogen injection and cylinder injection engines,and conducts experiments and simulation verification using AVL-Fire.Six sets of ignition timings with different ranges were selected at different speeds and loads to investigate the effect of ignition timing on engine combustion and emission performance,with hydrogen injection pressure ranges of 2 bar,2.5 bar,3 bar and 3.5 bar at low and medium speeds,and 3 bar,3.5 bar,4 bar and 4.5 bar at medium and high speeds.To investigate the effect of hydrogen injection pressure on in-cylinder mixture movement,in-cylinder combustion and emissions.The ignition timing and hydrogen injection pressure that make the power,economy and emission of the hydrogen-doped gasoline engine optimal are obtained from the results of the study,and further optimization is carried out.Based on the data from the simulation experiments and the theoretical formulae of the assignment method,the index weights of the G1 assignment method,the entropy assignment method and the combination assignment method are calculated respectively.Finally,a simulation experiment was carried out to verify the performance evaluation indexes of the hydrogen-doped engine by fitting a non-linear surface to obtain the optimal combinations of ignition timing and hydrogen injection pressure under each operating condition.The research results indicate that within the ignition timing range selected for the study,as the ignition advance angle increases,the indicated power and indicated thermal efficiency of the engine show a trend of first increasing and then decreasing.By analyzing the simulation results,it can be obtained that the optimal ignition timing for hydrogenated gasoline has the best power and economy.At different speeds,with the decrease of load,the optimal ignition advance angle shows a trend of advancing.The increased pressure of hydrogen injection and the increased intensity of in-cylinder turbulence are conducive to a more homogeneous mixture formation and contribute to the combustion of the engine.As the engine speed increases,the optimum hydrogen injection pressure increases and the effect of hydrogen injection pressure on the in-cylinder temperature and pressure is more significant at low and medium speeds.The best combinations of ignition timing and hydrogen injection pressure were obtained by fitting a non-linear surface to the comprehensive performance evaluation indexes of the hydrogen-doped engine using the combination weighting method and taking the medium load conditions of 3000r/min and 6000r/min as examples: 13.59°CA,0.258 MPa and 22.76°CA,0.45 MPa.