自由活塞膨胀机-直线发电机集成系统动力特性研究

Dynamic Performance Research of a Free Piston Expander-Linear Generator

为了提高车用内燃机余热能回收系统中膨胀机热功转换效率,通过试验与仿真相结合的方法,在压缩空气平台上对一台自由活塞膨胀机-直线发电机集成系统进行了试验研究,同时,基于MATLAB/Simulink软件搭建了系统仿真模型并进行了验证.基于该仿真模型研究了活塞初始位移、活塞-动子连杆质量以及工作频率等对系统动力特性的影响.结果表明:当仿真进气压力为0.188 MPa、工作频率为2.5 Hz时,初始位移存在唯一值-0.045 307 m,使得活塞以位移0点为中心做往复运动;当进气压力、工作频率一定时,活塞运动行程、速度峰值、加速度峰值以及指示功均随活塞-动子连杆质量增大而减小.当系统启动时,工作频率应高于固有撞击频率f0,避免活塞对气缸顶面(或端面)产生撞击.

To improve the thermal conversion efficiency of the expander applied in the organic Rankine cycle for recovering low-grade waste heat from internal combustion engine, the performance of a free piston expander-linear generator was studied by experiments and simulations in the air test rig. A simulation model built by MATLAB/Simulink software was verified by experiments, and the influence of the initial displacement of the piston, the piston-mover mass and working frequency on the dynamic characteristics was studied. The results show that there is only one point ( -0. 045 307 m) that enables the piston to do reciprocating motion near the displacement of 0 point when inlet pressure and working frequency are 0. 188 MPa and 2. 5 Hz, respectively. Stroke length, peak velocity, peak acceleration and indicated work of the piston decrease with the piston-mover mass increasing. To protect the system of free piston expander-linear generator from damage, the frequency can not be too low, otherwise the piston will hit the cylinder.