Parametric modeling and optimization of the intake port in a naturally aspirated opposed rotary piston engine across the full speed range

The opposed rotary piston (ORP) engine offers advantages such as compact size, simple structure, and high power density, making it highly promising for long-endurance unmanned aerial vehicles (UAVs). Parametric modeling of intake ports and the investigation of structural parameters on intake characteristics for ORP engines are crucial for improving the intake performance. In this paper, based on the kinematic model of the ORP engine, parametric modeling of the intake and exhaust ports are performed, a 3D numerical model is established to explore the intake characteristics at different engine speeds. The impact of intake delayed closing angle (IDCA), intake inclination angle (IIA), and dual intake ports on the intake characteristics of the ORP engine are investigated. Finally, the combustion characteristics and performance metrics of the engine using optimized intake ports are compared against the baseline intake phase. The results indicate that the CGE and pumping loss of the ORP engine initially increase and then decrease with rising engine speed. The CGE exceeds 92 % at 1000 r·min⁻¹ and 94 % at 5000 r·min⁻¹ when the IDCA are set at 8° and the IIA at −20°. The pumping losses at 4000 r·min⁻¹ and 5000 r·min⁻¹ are reduced by 33.3 % and 30.9 %, respectively, after intake port optimization. The performance metrics at 1000 r·min⁻¹ and 2000 r·min⁻¹ show a slight decline compared to pre-optimization due to lower turbulence kinetic energy (TKE) and intake backflow. However, at 3000–5000 r·min⁻¹, the optimized intake port structure significantly improves performance metrics of the ORP engine.