Scavenging Ports’ Optimal Design of a Two-Stroke Small Aeroengine Based on the Benson/Bradham Model

Abstract

The two-stroke engine is a common power source for small and medium-sized unmanned aerial vehicles (UAV), which has wide civil and military applications. To improve the engine performance, we chose a prototype two-stroke small areoengine, and optimized the geometric parameters of the scavenging ports by performing one-dimensional (1D) and three-dimensional (3D) computational fluid dynamics (CFD) coupling simulations. The prototype engine is tested on a dynamometer to measure in-cylinder pressure curves, as a reference for subsequent simulations. A GT Power simulation model is established and validated against experimental data to provide initial conditions and boundary conditions for the subsequent AVL FIRE simulations. Four parameters are considered as optimal design factors in this research: Tilt angle of the central scavenging port, tilt angle of lateral scavenging ports, slip angle of lateral scavenging ports, and width ratio of the central scavenging port. An evaluation objective function based on the Benson/Bradham model is selected as the optimization goal. Two different operating conditions, including the take-off and cruise of the UAV are considered. The results include: (1) Orthogonal experiments are analyzed, and the significance of parameters are discussed; (2) the best factors combination is concluded, followed by simulation verification; (3) results before and after optimization are compared in details, including specific scavenging indexes (delivery ratio, trapping efficiency, scavenging efficiency, etc.), conventional performance indicators, and the sectional views of gas composition distribution inside the cylinder.

Investigation on the Performance Characteristics of 2-Stroke Heavy Fuel Light Aeroengine (2SHFLA) with Different Fuel Injection Systems: Modeling and Comparative Simulation

“…With regard to the initial prototype engine, the unique gas exchange process features prominently in its working principle. As shown in Figure 4, the complete gas exchange process can be roughly divided into three phases including free exhaust phase, forced scavenging phase, and final exhaust phase [31,32]. The expansion stroke of the initial prototype engine gradually draws to a close as the piston descends from the TDC.…”

“…It is in the cylinder that the scavenging process takes place. As a consequence, the EngCylScav is determined as the engine scavenging model with the scavenging profile displayed in Figure 14 as an indispensable model input [31]. As shown in Figure 14, the following two attributes establish the scavenging profile: the cylinder residual ratio (i.e., the mass fraction of burned gases in the cylinder) and the exhaust residual ratio (i.e., the mass fraction for burned gases in the exhaust pipe).…”

“…The cylinder pressure curve is one of the most important criteria for verifying the accuracy of the calculation results of the simulation platform of the initial prototype engine [31,32]. To enable real-time monitoring in the simulation process, the related cylinder pressure monitoring simulation modules are added into the established model.…”

A Novel Control Algorithm Design for Hybrid Electric Vehicles Considering Energy Consumption and Emission Performance

“…In order to simultaneously account for the indicators of energy consumption and emission performance, appropriate multi-objective optimization method should be employed. For the control algorithm of EMS for HEVs, DP, and ECMS are commonly used methods [37]. The former adopts a traverse approach to get the global optimum solution, while the latter usually establishes a m batt,eqv is the equivalent fuel consumption rate of consumed battery energy, α e f is an equivalence factor applied to convert consumed battery energy into fuel consumption rate, E batt is consumed battery energy, LHV is the low heating value of used fuel, and .…”

Investigation of the Vibration Transmission Characteristics of the Aero-Engine Casing System by Rotating Force Exciter

“…The reduction of the thickness of the casing structure of the aero engine will easily excite the casing vibration and give rise to the whole aero engine's vibration [1][2][3][4][5][6]. Most aero-engine faults are caused by vibration overrun.…”