Effect of ignition timing on combustion characteristic of the elliptical rotary engine under different rotary speeds

This research aims to reveal the effect of ignition timing (IT) on combustion characteristic of the elliptical rotary engine (ERE) under different rotary speeds. Therefore, computational fluid dynamics (CFD) model that can accurately describe the working process of the ERE was established and validated through experimental data. Simulation results show that, the higher the rotary speed, the higher the airflow speed and turbulent kinetic energy (TKE). With the advance of the IT, the combustion speed increases, combustion reaction intensity increases. As the rotary speed increases, the combustion speed decreases. When the rotary speed is 5000 r/min and 7000 r/min, as the IT advances, there is a noticeable rise of average pressure and temperature in cylinder, resulting in an earlier occurrence of peak pressure and temperature, the higher the rotary speed, the more obvious. But when the rotary speed is 3000 r/min, with the IT advances, the peak pressure and temperature increases firstly and then decreases. As the rotary speed increases, the pressure and temperature in cylinder decreases. In order to achieve the highest indicated power and indicated thermal efficiency (ITE), when the rotary speed is 3000 r/min, the IT should preferably be 20°CA BTDC, when the rotary speed is 5000 r/min, the IT should preferably be 25°CA BTDC, when the rotary speed is 7000 r/min, the ideal value of IT should be 35°CA BTDC. This research proposes a means for matching the rotary speed and IT of the ERE.