Influence of Engine Speed on Combustion, Performance, Airflow, and Emission Characteristics

Abstract

This study investigates the effects of engine speed on key performance, combustion, air intake, fuel consumption, and emission characteristics of a compression ignition engine operating within the range of 1500 to 3000 rpm. A series of controlled engine tests were conducted to evaluate combustion duration, brake torque, brake mean adequate pressure (BMEP), indicated mean effective pressure (IMEP), specific fuel consumption (SFC), NOx emissions, total mass airflow, and volumetric efficiency. The results reveal that combustion duration decreased significantly from 83°CA at 1500 rpm to 37°CA at 3000 rpm, while BMEP declined from 6.6 bar to 4.3 bar, and brake torque dropped from 1000 Nm to 630 Nm. IMEP peaked at 8.55 bar at 2000 rpm, indicating optimal combustion efficiency at mid-range speed. In contrast, SFC increased from 0.235 kg/kWh to 0.305 kg/kWh, reflecting reduced thermal efficiency at higher speeds. NOx emissions exhibited a peak value of 2220 ppm at 2100 rpm, then gradually declined, emphasizing the trade-off between power output and emission control. Volumetric efficiency decreased from 91.5% to 75.5%, while total mass airflow rose from 0.255 kg/s to 0.42 kg/s. The novelty of this study lies in its integrated and comparative analysis across multiple engine parameters, offering a holistic understanding of engine dynamics. These findings serve as a reference for optimizing engine performance and emission strategies, and they provide a benchmark for future research involving alternative fuels, advanced combustion modes, and real-time control algorithms.