| From the invention of automobiles to the recognition and mass use of society,automobiles have formed their unique development methods.And continue to promote social reform and progress.The combustion of the engine bears the brunt of the difference in engine performance.The development of science and technology has also noticed the irreversible damage to the environment while pursuing high-performance engines.Therefore,people need to find and explore new combustion methods and clean fuels,and coal-bed methane begins to enter people's sight.Because of its combustion and environmental protection,it has attracted much attention.Therefore,it is necessary for us to study its combustion in the engine.This paper builds a model of the engine combustion chamber based on Pro / Engineer,and conducts in-cylinder combustion simulation through CONVERGE.Because there is no reaction and kinetics model that matches the combustion of diesel-fired coal-bed methane,the combustion mechanism of the variable components of diesel ignition is simplified and merged through the chemical analysis kinetic software Chemkin-Pro The reaction mechanism is simplified.The detailed n-heptane combustion mechanism of Lawrence National Laboratory is used to replace diesel combustion,and the detailed natural gas combustion mechanism of the University of Southern California is used to replace the combustion of coal bed methane.The NOx reaction mechanism is combined to form the combustion mechanism required in this paper.Investigate the in-cylinder combustion cylinder and emission characteristics of diesel-ignited variable-component CBM engines.It is found through simulation that:(1)The increase of methane content in coal bed methane increases the in-cylinder combustion heat load,and the in-cylinder pressure and temperature have been significantly improved.The influence of methane on the engine temperature and pressure has beenthroughout,but the corresponding combustion load At the same time,the NOx content in the cylinder increases,the exhaust temperature increases,and the engine emission performance deteriorates.(2)The study found that although the content of ethane in coal bed methane is not much,it also has a very large impact on the combustion in the cylinder.Increasing the content of ethane will reduce the temperature and pressure in the engine cylinder.The effect of ethane on the temperature is between top dead center and the crank angle of 40 °,while the effect on the pressure is mainly concentrated on the top dead center to the crank angle of 15 ° between.And as the temperature and pressure in the cylinder decrease,the NOx content decreases significantly,and the temperature of the exhaust gas decreases slightly but not significantly.(3)The increase in the propane content in coal bed methane increases the combustion heat load in the cylinder,and the pressure and temperature in the cylinder are significantly increased.Its impact on pressure is mainly concentrated between the top dead center and the crank angle of 10 °.The influence of temperature is between the top dead center and the crank angle of 40 °,and the content of NOx generated by combustion rises significantly with the increase of propane,and the exhaust temperature also increases accordingly.(4)It can be seen that adding hydrogen to coal-bed methane of low component methane is beneficial to the combustion in the cylinder.As the hydrogen content increases,the combustion in the cylinder becomes more and more intense,and the heat load in the cylinder continues to increase.Its impact on pressure and temperature continues to affect after the top dead center.The addition of hydrogen can indeed greatly improve the impact of the low component methane combustion situation,but with the increase of hydrogen content,its emission The increase in gas temperature and the increase in NOx content in the exhaust have brought greater pressure to the exhaust system. |
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