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方法。与传统发动机不同，这种发动机不使用曲轴，直接通过活塞的直线运动产生电能。取消曲轴并使用直接耦合到活塞的线性电机的好处是，活塞在燃烧过程力的作用下自由运动。这意味着活塞的运动不再受曲轴的限制。换句话说，不需要将活塞的线性运动转换为旋转运动。因此，可以通过消除曲轴以更直接的方式实现燃料到电力的转换。因此，摩擦损耗和系统总重量都得到了降低，效率也得到了显著提高。永磁电机在力/功率密度方面具有最佳性能。此外，由于使用PM代替承载电流的线圈，效率也更高，并且对于相同的设计功率，与其他拓扑相比，PM电机占用更少的体积。由于这些原因，永磁同步电机被选择用于该应用。管状直线电机与扁平直线电机相比，更适合与发动机集成，因为它与活塞和气缸形状更兼容。直线永磁电机存在一些缺点：齿槽力和边缘力，干扰位置精度并引起振荡和不稳定性，以及偏心增加线性轴承中的摩擦，造成损失并减小有效力。为了减少这些磁阻力，可以采取一些策略，例如，通过倾斜或步进的磁铁和优化PM dimensions.Primary目标是紧凑的FPEG系统的可行性，以产生电力，例如，充电电池或供应任何负载。将线性电机与压缩机气缸联合收割机组合的新颖想法导致紧凑的系统设计。提出了一种将直线电机与压缩机气缸集成为一体的方法，即采用一组线圈作为定子，在连杆活塞表面嵌入环形永磁体作为转换器。然后在发动机过程的驱动下，平移器作往复直线运动，产生电能。此外，可以在Siemens LMS imagine Lab Amesim仿真软件中检查机械和电气系统的耦合。然后，通过修改线性焦耳发动机发电机系统的关键参数，可以确定最佳的系统性能（例如发电量）。另外，对直线发电机进行优化设计，有三个目的。第一个目标是获得最大的电力。为了达到最大的电输出功率，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，寻找一种能保证轴力最大的几何结构是非常重要的。第二个目的是减少LG的齿槽力。这对LG的耐用性很重要。第三个目的是减轻动子的重量。这对于获得最佳发动机性能至关重要。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2-D和3-D FEA结果。总之，FPEG系统产生功率，然后将所产生的功率馈送到电力电子系统中用于电力转换目的，从而导致对车载电池充电或激励电机以驱动电动车辆的车轮。这项技术也可以用作混合动力汽车的增程器，或为自动驾驶汽车提供电力。

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