Abstract
A closed-cycle, three-dimensional (3D) computational fluid dynamics (CFD) analysis campaign was conducted to evaluate the performance of using spark plugs to assist gasoline compression ignition (GCI) combustion during cold idle operations. A conventional spark plug using single-sided J-strap design was put at a location on the cylinder head to facilitate spray-guided spark assistance. Ignition was modeled with an L-type energy distribution to depict the breakdown and the arc-to-glow phases during the energy discharge process. Several key design parameters were investigated, including injector clocking, number of nozzle holes, spray inclusion angle, number of fuel injections, fuel split ratio, and fuel injection timings. The study emphasized the region around the spark gap, focusing on flame kernel formation and development and local equivalence ratio distribution. Flame kernel development and the ignition process were found to correlate strongly with the fuel stratification and the flow velocity near the spark gap. The analysis results showed that the flame kernel development followed the direction of the local flow field. In addition, the local fuel stratification notably influenced early-stage flame kernel development due to varying injection spray patterns and the fuel injection strategies. Among these design parameters, the number of nozzle holes and fuel injection timing had the most significant effects on the engine combustion performance.
Highlights
Regulatory demand for reducing vehicle criteria pollutants and CO2 emissions is increasing around the world
Gasoline compression ignition (GCI) has gained attention in recent years because of its potential to harness gasoline’s low reactivity to enhance partially premixed compression ignition, whereby high fuel efficiency is achieved while engine-out
We found that combustion efficiency was improved and CA50 was advanced by increasing the glow plug surface temperature
Summary
Regulatory demand for reducing vehicle criteria pollutants and CO2 emissions is increasing around the world. GCI has gained attention in recent years because of its potential to harness gasoline’s low reactivity to enhance partially premixed compression ignition, whereby high fuel efficiency is achieved while engine-out. The implications of gasoline’s high volatility and low reactivity on spray evaporation, fuel-air mixing, and ignition under very cold conditions have not been clearly established [16,17,18,19]. During cold start operation, forced ignition assistances such as glow plugs have been commonly used in diesel engines to increase the local temperature and promote vaporization prior to the mixture preparation process [20]. Building on previous spark-assistance work, we conducted a thorough evaluation of the injector spray pattern and the fuel injection strategy to gain insight into their impacts on flame kernel development, equivalence ratio distribution near the spark gap, and global combustion characteristics. Particular emphasis was placed on studying the effects of several key design variables, including injector clocking, number of nozzle holes, spray inclusion angle, fuel split ratio, and fuel injection timings
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
