Combustion And Emission Characteristics Of Gasoline Rotory Engine With Different Ignition Parameters And Fuel Mixing Conditions

Rotory engines are widely used in military field as power source of military equipment because of its simple and compact structure,high power-weight ratio and flexible handling.With the development of hybrid electric vehicles,the rotory engine,as the power source of the range extender,also has a relatively broad development prospects.The rotational speed of a rotory engine is relatively high.The micro-cyclic variation of the initial ignition nucleus generation and development in the ignition process of the engine will cause completely different characteristics of flame propagation and cylinder pressure in the later stage,which will lead to cyclic variation of engine power performance and emission performance.Therefore,it is important to study the influence of ignition parameters and initial ignition conditions on the ignition process of a rotory engine.In addition,the working chamber of the rotory engine is narrow and flat,and it is difficult for flame to propagate to the back of the working chamber during combustion,which results in insufficient oxidation of the combustibles in the back of the working chamber and high fuel consumption and emission,especially under the conditions of medium and high speed operation.Compared with gasoline,hydrogen has many advantages,such as low ignition temperature,fast flame propagation,high combustion temperature and short quenching distance.It is also of practical significance to explore the effects of different hydrogen mixing ratios on ignition,combustion and emission performance of gasoline rotory engines under medium and high speed operation conditions.Furthermore,referring to the method of using EGR internal purification technology to reduce NO_x during combustion in reciprocating piston engine,the effects of different inert component coefficients on ignition,combustion and emission performance of gasoline rotary engine under medium and high speed operation conditions were investigated by incorporating inert gas CO₂ into the intake of gasoline rotary engine,which can also provide some data support for the operation parameters of a gasoline rotory engine.In this paper,the combustion and emission characteristics of a gasoline rotory engine under different ignition parameters and fuel mixing conditions were simulated by means of numerical simulation.Based on the structural parameters of Z160F gasoline rotory engine,a physical model was established.The three-dimensional dynamic simulation of the engine was realized by using Fluent as the research platform and self-compiled C program.According to the operation characteristics of the rotary engine,the turbulence model,ignition model and combustion model were selected reasonably,and then the simplified isooctane reaction mechanism was coupled to successfully realize the dynamic simulation calculation of the working process of the gasoline rotary engine.The innovations and conclusions of the research work are as follows:?1?The ignition process under different ignition energies,equivalence ratios and ignition advance angles were simulated.The temperature nephogram in the ignition process was processed by using MATLAB self-programming program,and the radius of the ignition nucleus at different time under different conditions was obtained.The radius of the initial nucleus is most affected by the ignition energy.With the increase of the ignition energy,the faster the radius of the nucleus increases,the larger the radius of the critical nucleus,and the more stable the ignition process is.When the mixture equivalence is large,that is to say,the relatively dense mixture is beneficial to the development of the ignition nucleus of the rotory engine.When the equivalence ratio is 1.1,the radius of the nucleus develops relatively best.Under the same conditions of eccentric shaft speed,mixture equivalent ratio and ignition energy,when the ignition advance angle of engine is 35°CA BTDC,the ignition radius increases fastest and the ignition of engine is the most stable.?2?The effects of different hydrogen mixing ratios on ignition process,combustion performance and emission performance of a gasoline rotory engine were investigated.The effective instantaneous heat release rate and effective cumulative heat release rate in a rotory engine were proposed and deduced,which provides some ideas for the analysis of the heat release law in the combustion process of a rotory engine.When the chemical equivalence ratio of mixed gasification is kept at 1,with the increase of hydrogen content in intake,the average turbulent kinetic energy in cylinder increases,the growth of ignition nucleus accelerates,the critical radius of ignition nucleus increases,the maximum pressure in cylinder increases,and the eccentric axis angle corresponding to the maximum pressure advances,and the combustion isovolumetric increases.With the increase of hydrogen content in mixture,the maximum combustion temperature in cylinder increases,the mass fraction of NO in exhaust increases,and the mass fraction of CO decreases.?3?The effects of different CO₂ mixing ratio on ignition process,combustion performance and emission performance of gasoline rotory engine were investigated.Under the condition that the chemical equivalence ratio of mixed gasification is kept at 1,with the increase of inert gas ratio in the mixture,the average turbulent kinetic energy in cylinder decreases,the growth rate of ignition nucleus slows down and the critical radius of ignition nucleus decreases;the maximum pressure in cylinder decreases and the eccentric axis rotation angle corresponding to the maximum pressure lags behind,the combustion phase delays as a whole,and the post-combustion period lengthens.With the increase of inert gas proportion in the mixture,the maximum combustion temperature in cylinder decreases,the mass fraction of NO in exhaust decreases obviously,and the mass fraction of CO increases.