被动进气式自由活塞发电机设计与特性分析

Design and Characteristics Analysis of Free-piston Linear Alternator with Piston-mounted Passive Inlet Valve

摘要:

设计了一种采用轴向直流换气的被动进气式自由活塞直线发电机，阐述了其主要结构和工作原理，建立了动力学及热力学方程，实验验证了仿真模型的工作过程，分析了工作过程运动特性和相关结构参数对系统性能的影响规律，为性能优化及样机设计提供依据。结果表明工作过程中，发动机换气持续时间约占全周期的58%，有利于新鲜充量进入到气缸；活塞运动曲线呈非对称状，在上止点加速度变化剧烈，需要加大燃烧放热速度来适应其变化；适当加大活塞质量及排气口开闭位置，减小点火提前位置和进气阀门的开启压力，可使样机具有较高的输出功率。

Abstract:

A free-piston linear alternator with an axial uniflow-scavenged using passive charge valve was designed. The structure and principle of the alternator were introduced. A simulation model of the working process which was validated with the test was established based on dynamics and thermodynamics equation. The motion characteristics and the performance effective factors of the alternator which was beneficial for performance optimization and prototype design were analyzed. The simulation results show that the alternator possesses a longer ventilation time and the duration accounts for about 58% of the whole cycle, which provides sufficient fresh mixture entering the cylinder. The motion curve of piston is non-symmetrical, the acceleration of the free-piston at TDC changes violently and it needs accelerate the combustion heat release rate to adapt to the changes. It should appropriately increase the piston mass and the opening-closing position of the exhaust valve, and reasonably reduce the ignition advanced position and the working pressure of the inlet valve to reach higher output power.