Dr. Mohammad Javad Noroozi, Mr. Mahdi Seddiq, Mr. Hessamedin Habibi,
Volume 10, Issue 4 (12-2020)
Abstract
Due to very low PM and NOx emissions and considerable engine efficiency, dual-fuel combustion mode such as RCCI strategy attracted lots of attention compared to other combustion modes. In this numerical research work, the impacts of direct injection timing and pressure of diesel fuel on performance and level of engine-out emissions in a diesel-butanol RCCI engine was investigated. To simulate the combustion process, a reduced chemical kinetic mechanism, which consists of 349 reactions 76 species was used. The influence of thirty-six various strategies based on two diesel spraying characteristics such as injection pressure (650, 800, 1000, and 1200 bar) and diesel spray timing (300 to 340 CA with 5 CA steps) have been examined. Results indicated that, under the specific operating conditions like 1000-bar spray pressure by direct injection at 45 CA BTDC and the spray angle of 145 degrees, the level of cylinder-out pollutants such as CO (up to 26%), NOx (about 86%), PM (by nearly 71%) and HC (about 17.25%) have been simultaneously reduced. Also, ISFC decreased by about 2.3%, IP increased by about 2.4%, and also ITE improved by nearly 2% compared to the baseline engine operating conditions.
Mr Mehran Nazemian, Mr Mehrdad Nazemian, Mr Mahdi Hosseini Bohloli, Mr Hadi Hosseini Bohloli, Mr Mohammad Reza Hosseinitazek,
Volume 14, Issue 3 (9-2024)
Abstract
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 130 µm to 175 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 130 µm significantly enhances fuel atomization by reducing SMD to 15.49 µm and increasing droplet number by 24%, 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 (150–160 µm) achieve the highest combustion efficiency (92.04%) and gross indicated efficiency (38.58%). However, further reduction in NHD below this range causes premature ignition, energy dissipation, and higher NOx emissions (10.08 g/kWh) due to elevated combustion temperatures. Conversely, when the NHD increases to 175 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 (15.27 gr/kWh) and CO (4.22 gr/kWh) emissions. Larger NHDs, however, lower NOx emissions to 2.66 gr/kWh due to reduced peak temperatures. This study clearly identifies an optimal NHD range (150–160 µm) that effectively balances droplet size, evaporation rate, combustion timing, and emission reduction, thereby enhancing both engine performance and environmental sustainability.
