Numerical Investigation On The Turbulent Jet Characteristics And Regulatory Mechanism Of An Active Pre-chamber Fueled With Methanol

High-efficiency and clean combustion technology of low-carbon and zero-carbon fuels is the key technology for reducing CO₂ emissions and realizing carbon-neutral operation of internal combustion engines.Methanol fuels come from a wide range of sources,and the synthesis of methanol from green hydrogen and CO₂ can achieve carbon-neutral operation,which is a promising renewable synthetic fuel and has received extensive attention in the internal combustion engine community in recent years.However,due to the high octane number and latent heat of vaporization,the application of methanol in internal combustion engine still faces problems,such as difficulty in cold start under low-load conditions,poor combustion stability,and high peak pressure and pressure rise rate under high-load conditions.In recent years,the pre-chamber jet ignition technology has attracted wide attention,which has been regarded as an effective measure to realize the highly efficient and clean utilization of methanol fuel in internal combustion engines.However,there are very limited research on the methanol-fueled pre-chamber jet ignition combustion systems can be found in literatures.To this end,this paper conducts numerical investigation on the turbulent jet characteristics and regulatory mechanism of an active pre-chamber fueled with methanol.In this paper,a three-dimensional numerical model of an active pre-chamber turbulent jet ignition system fueled with methanol based on a high-pressure constant-volume combustion bomb is firstly established,and related sub-models were carefully calibrated and verified.On this basis,methanol mixture gas preparation,the influences of pre-chamber structure and control parameters on turbulent ignition jet characteristics were investigated.The results show that:the fuel spray significantly affects the mixture preparation by changing the flow structure inside the pre-chamber,and promoting the tumble flow inside the pre-chamber can improve the mixing process and form more homogeneous mixture.The structural parameters and operating parameters of the pre-chamber have important influence on the formation and development of the ignition jet.Under the current configuration,the pre-chamber with length-diameter ratio of 2 can produce the ignition jet with longer penetration distance and higher active intensity.The equivalence ratio of the pre-chamber and the jet injection hole diameter are the key parameters which affect the ignition jet characteristics,and a control strategy can be proposed accordingly.It is found that increasing the equivalence ratio,adopting a larger injection hole,and increasing the initial temperature of the pre-chamber can significantly improve the reactivity intensity of the ignition jet,while smaller injection hole can significantly increase the flow velocity of the jet,but the reactivity intensity of the jet will be greatly reduced.Furthermore,the effects of ignition jet on the combustion process of premixed lean methanol/air charge in the main-chamber was investigated.The results showed that:the velocity characteristic of the ignition jet has limited effect on the main-chamber combustion.The ignition delay of the main-chamber is shortened with the increase of the jet reactivity intensity,and the combustion heat rate of the main-chamber firstly increases and then decreases with the increase of the jet reactivity intensity,and the main-chamber combustion reaction rate reached the maximum when the equivalence ratio of the pre-chamber was about 1.3,For the same ignition jet,when the equivalent ratio of the main-chamber premixed charge is higher than 0.3,the ignition characteristics of the lean mixture does not change significantly with the varies of the equivalent ratio in pre-chamber.When the equivalent ratio of the main-chamber is further reduced,the ignition delay begins to prolong,and eventually leads to misfire.In summary,this paper conducted numerical investigation on the turbulent jet characteristics and regulatory mechanism of an active pre-chamber fueled with methanol,and the influence of the structure and control parameters of the pre-chamber on the characteristics of the turbulent ignition jet was explored and revealed,based on which a regulatory strategy of the turbulent ignition jet characteristics was proposed.The current study should have important theoretical significance and guiding value to the development of high efficiency and clean methanol engines.