Modelling and Development of Integrated Electrical Machines in Linear Combustion Engines

自由活塞发动机发电机（FPEG）系统是一种特殊类型的内燃机，代表了将燃料的化学能转化为电能的新途径。与传统发动机不同，这种发动机不使用曲轴，而是通过活塞的直线运动直接产生电能。去掉曲轴，使用直线电机直接耦合活塞的好处是，活塞在燃烧过程力的作用下可以自由运动。这意味着活塞的运动不再受曲轴的限制。换句话说，没有必要将活塞的直线运动转换为旋转运动。因此，通过消除曲轴，可以更直接地实现燃料到电力的转换。因此，减少了摩擦损失和系统总重量，并显着提高了效率。永磁电机在力/功率密度方面具有最好的性能。此外，效率也更高，因为使用永磁电机而不是线圈携带电流，以及与相同设计功率的其他拓扑相比，永磁电机占用的体积更小。由于这些原因，永磁同步电机被选择用于此应用。由于管状直线电机与活塞和气缸的形状更加兼容，与扁平直线电机相比，管状直线电机更适合与发动机集成。线性永磁电机表现出一些缺点：齿槽力和边缘力，干扰位置精度并引起振荡和不稳定，偏心增加了线性轴承的摩擦，造成损失并降低了有效力。为了减少这些缓冲力，可以采用一些策略，例如，通过倾斜或步进磁铁和优化PM尺寸。该项目的主要目标是紧凑型FPEG系统产生电力的可行性，例如，充电电池或提供任何负载。将线性电机与压缩机气缸相结合的新颖想法使系统设计紧凑。提出采用一组环向线圈作为定子，在连杆-活塞表面埋设环形永磁转子作为转换器，将直线电机与压缩机气缸集成在一起。然后在发动机的作用下，翻译器前后直线运动，产生电能。此外，在西门子LMS imagine Lab Amesim仿真软件中，可以对机电系统的耦合进行检测。然后通过修改线性焦耳发动机发电机系统的关键参数来确定系统的最优性能（例如发电）。此外，通过对线性发电机（LG）的优化，可以达到三个目标。第一个目标是获得最大的电力。为了达到最大的电力输出功率，有必要开发具有最大轴向力的LG。因此，在一定的边界条件下，寻找一种能保证轴向力最大的几何结构是十分重要的。第二个目标是减少LG的齿槽力。这对LG的耐用性很重要。第三个目标是减轻推动者的重量。这对于获得最佳引擎性能非常重要。所有这些优化的基础是FEA工具。通过使用该工具，可以计算不同类型LG的二维和三维有限元结果。综上所述，FPEG系统产生电力，然后将产生的电力输入电力电子系统进行电力转换，从而为车载电池充电或为电机通电，以驱动电动车辆的车轮。这项技术还可以用作混合动力汽车的增程器或为汽车提供电力

A Free Piston Engine Generator (FPEG) system is a special type of combustion engine representing a new approach concerning the conversion of the chemical energy of fuel into electrical energy. Unlike conventional engines, this type of engine does not use a crankshaft, and generates electric energy directly by a linear movement of pistons.The benefit of removing crankshaft and using linear electrical machine coupled directly to the piston is that, piston is free to move under the action of combustion process force. That means the movement of piston is not restricted by crankshaft any more. In other words, there is no need to convert linear motion of piston to rotary motion. Consequently, converting fuel to electricity can be achieved in more direct way with elimination of crankshaft. As a result, frictional loss and total system weight are reduced, and efficiency is increased significantly.Permanent Magnet (PM) electrical machine has the best performance in terms of force/power density. Furthermore, efficiency is also higher due to using PMs instead of coils carrying current as well as PM electrical machines occupy less volume compared to other topologies for the same design power. Due to these reasons, PM synchronous electrical machine is chosen for this application. Tubular shaped linear electrical machine is a suitable candidate for integration with engine compared to flat shaped linear electrical machine, because it is more compatible with piston and cylinder shape.Linear PM electrical machines exhibit some drawbacks: cogging forces and edge forces, disturbing the positional accuracy and cause oscillations and instabilities, and eccentricity increases the friction in linear bearings, causing losses and reducing the effective force. In order to decrease these detent forces, some strategies can be adopted, for example, by skewing or stepping the magnets and optimizing the PM dimension.Primary objective of this project is feasibility of compact FPEG system to generate electrical power, for instance, charging electric batteries or supplying any load. The novel idea to combine the linear electrical machine with the compressor cylinder leads to a compact system design. It is proposed to integrate the linear electrical machine with the compressor cylinder, by using a set of coils circumferentially as a stator and embedding ring shaped PMs on the surface of connecting-rod-piston as a translator. Then linear movement of translator back and forth driven by engine process, generates electrical power. Furthermore, coupling the mechanical and electrical systems can be examined in Siemens LMS imagine Lab Amesim simulation software. Then optimal system performance (for instance electrical power generation) can be identified by modifying the key parameters of linear joule engine generator system. What's more, there are three aims to be achieved by the optimization of the Linear Generator (LG). The first aim is to get a maximum electrical power. To reach a maximum of electric output power it is necessary to develop a LG with maximum axial force. So it is important to find a geometric structure which guarantees a maximum of axial force under consideration of certain boundary conditions. The second aim is to reduce the cogging force of the LG. This is important for the durability of the LG. The third aim is to reduce the weight of the mover. This is important to get an optimal engine performance. The base of all these optimizations is the FEA tool. By using this tool it is possible to calculate 2-D and 3-D FEA results for different types of LG. In conclusion, FPEG system, generates power, then this generated power is fed into power electronic system for electrical power conversion purpose, hence leads to charge an on board battery or energising the motor in order to drive the wheels of an electric vehicle. This technology can also be used as a range extender in hybrid electric vehicles or providing the electrical power for aut