Investigating the Influence of Intake Runner Configuration on Scavenging and Combustion Processes in Elliptical Rotor Engines

Elliptical rotor engines (ERE), also known as X-engines, feature intake and exhaust ports located on the rotating rotor. As the rotor turns, these ports traverse the entire combustion chamber, sequentially completing the scavenging process in three distinct combustion chambers through coordination with the cylinder walls. This intake and exhaust characteristic significantly differs from the characteristic found in traditional Wankel rotor engines. This study established an optical elliptical rotor engine to obtain the in-cylinder flow field by using Particle Image Velocimetry (PIV) and constructed a CFD model based on the experimental results. Then the effects of two different intake runners on the scavenging and combustion process of ERE were investigated. The results indicated that: Due to structural limitations, the prolonged intake port opening duration results in significant gas backflow during the intake process. The curved intake runner exhibits a higher turbulent kinetic energy (TKE), while the straight intake runner achieves faster intake velocity. At engine speeds of 3000 r/min, 5000 r/min, and 9000 r/min, the straight intake runner improved volumetric efficiency by 2.6%, 4.6%, and 22.8% compared to the curved intake. At low speed, the curved intake runner demonstrates superior maximum cylinder pressure and combustion performance due to its faster flame propagation speed. However, at high engine speed, the influence of intake runner on the in-cylinder flow field diminishes. The straight intake runner’s higher volumetric efficiency compensates for its slower flame propagation speed, resulting in better cylinder pressure and combustion parameters compared to the curved intake runner.