Date of Graduation
Statler College of Engineering and Mineral Resources
Lane Department of Computer Science and Electrical Engineering
Permanent Magnet Linear Generators (PMLG) are electric generators which convert the linear motion into electricity. One of the applications of the PMLG system is with free piston engines. Here, the piston is moved by the expander using an internal combustion engine or a Stirling engine. Other applications of the PMLG are wave energy conversion, micro energy harvesters, and supercritical CO2 expander systems. The most common technology of the electric generators is a rotary electric generator. The current technology of the engine-generators (GENSET) is of a rotary type which uses a crankshaft to convert the linear motion to rotary motion coupled to a rotary electric generator. This technology can be improved by using PMLG in the place of rotary generators by eliminating the crankshaft in the system.
This research thesis is to introduce a new design guideline and steps to design and optimize a PMLG for linear reciprocating applications. The new design guideline provides the steps and techniques to calculate the electrical and geometrical parameters of the PMLG system with experimental verification. A finite element (FE) model of the PMLG system was developed using Finite Element Method Magnetics (FEMM) software. Furthermore, two experimental prototypes of the reciprocating engine PMLG were constructed and tested. The results from the experimental prototype were compared with the FE model and errors less than 10 % were found.
One of the important aspects of the reciprocating free piston engines is to have a low moving mass of the translator to increase the frequency of the system. Therefore, using the FE model, sensitivity study of different geometric parameters such as the magnet thickness, outer diameter of the magnet, airgap, frequency, stroke length, turns, poles, and spacer of the PMLG system was performed. It was found that the magnet thickness has a greater power / moving mass ratio compared to the other geometric parameters. Furthermore, an optimization routine was developed to optimize the PMLG system with low moving mass and low volume. Finally, a MATLAB GUI was developed for the optimization routine to simplify the process of optimization for new designers of the PMLG system.
Subramanian, Jayaram, "Design, Modeling and Optimization of Reciprocating Tubular Permanent Magnet Linear Generators for Free Piston Engine Applications" (2020). Graduate Theses, Dissertations, and Problem Reports. 7869.