Role of Nozzle Hole Diameter in Modulating Spray Dynamics and Enhancing Combustion Performance in Reactivity-Controlled Compression Ignition Engines

This study investigates the influence of nozzle hole diameter (NHD) variations on spray dynamics, combustion efficiency, and emissions in a Reactivity-Controlled Compression Ignition (RCCI) engine using Computational Fluid Dynamics (CFD) simulations with the CONVERGE software. The study systematically examines NHDs ranging from ۱۳۰ µm to ۱۷۵ µm and evaluates their impact on key parameters such as injection pressure, droplet formation, Sauter Mean Diameter (SMD), and evaporation rates. The results demonstrate that reducing NHD to ۱۳۰ µm significantly enhances fuel atomization by reducing SMD to ۱۵.۴۹ µm and increasing droplet number by ۲۴%, which in turn accelerates evaporation and improves fuel-air mixing. These effects shorten ignition delays, accelerate combustion, and increase peak cylinder pressures and temperatures. Optimal NHDs (۱۵۰–۱۶۰ µm) achieve the highest combustion efficiency (۹۲.۰۴%) and gross indicated efficiency (۳۸.۵۸%). However, further reduction in NHD below this range causes premature ignition, energy dissipation, and higher NOx emissions (۱۰.۰۸ g/kWh) due to elevated combustion temperatures. Conversely, when the NHD increases to ۱۷۵ µm, the larger droplets formed result in prolonged ignition delays, slower combustion, and lower peak pressures. These effects negatively impact combustion efficiency and promote incomplete combustion, leading to higher HC (۱۵.۲۷ gr/kWh) and CO (۴.۲۲ gr/kWh) emissions. Larger NHDs, however, lower NOx emissions to ۲.۶۶ gr/kWh due to reduced peak temperatures. This study clearly identifies an optimal NHD range (۱۵۰–۱۶۰ µm) that effectively balances droplet size, evaporation rate, combustion timing, and emission reduction, thereby enhancing both engine performance and environmental sustainability.

کلیدواژه ها:

RCCI Engine ، Nozzle Hole Diameter ، Spray Dynamics ، Combustion Efficiency ، Emissions