Optimum Permanent Magnets Configuration in Flat-Quasi Linear Permanent Magnet Generators

Flat-quasi type of linear permanent magnet generators (LPMGs) have been considered to be applied for several applications, such for wave energy conversion and free piston combustion engine. One of the important issues concerning LPMG is the permanent magnets configuration, due to its effects to the generator’s excitation performance. In this paper, a 1 kW flat-quasi LPMG would be designed and built. During the process, optimum permanent magnets configuration was required and researched. The optimum configuration considered the output power and resulted cogging force. Invetigation was then conducted by modifying several variables, including poles’ arrangement, pole length, number of pole, and pole skewing angle. The modification constraints were total permanent magnets’ volume and generator dimension. The results showed that permanent magnet configuration with halbach arrangement, pole length equals 55% of the slot pitch length, and 61.19o skewing angle produced the optimum output values

An investigation of the performance of a free-piston engine using Miller cycle and renewable fuels

A dual-piston type two-stroke spark-ignition free-piston engine prototype has been developed. A comprehensive review on recent published researches and patent documents from academia and industrial organizations on free-piston engine, especially the application of renewable fuels such as hydrogen and ethanol, was conducted. Relevant parameters affecting the operating performance and a number of challenges had been identified as the common denominator for this technology. Modelling and simulations using one-dimensional tools were conducted in parallel with the development activities. Three main simulation models for the crankshaft engines were developed, validated and optimised before converted into the free-piston engine model. This was done by using imposed-piston motion sub-model. The two-stroke free-piston engine model had undergone parametric study for valve timing optimisation. By using similar methods, a two-stroke hydrogen free-piston engine was developed from the prototype and it was validated by experimental data. Emission performance, along with the relationship between equivalent ratio, in-cylinder temperature and NOx emission on the hydrogen FPE was investigated. Series of ethanol-gasoline blend free-piston engine were developed, essential parameters such as compression ratio, air/fuel ratio and valve timing, etc., were amended for each model and both engine performance and emission performance were analysed. Miller cycle has been applied on three types of free-piston engine models: gasoline FPE, hydrogen FPE and ethanol FPE. Two types of Miller cycle (LIVC and EIVC) were both applied and analysed, and different late/early intake valve closing angles (from 5°CA to 35°CA) have been converted to specific time to apply on the free-piston engine. Engine performance and emission performance of Miller cycle free-piston engines have been obtained and individually presented. It turns out that large late/early intake valve closing angles (time) are not suitable in renewable free-piston engines due to the efficiency reduction

Dynamic Simulation of a Novel Free-Piston Linear Generator

This paper proposes a new structure of free-piston linear generator (FPLG) which consists of double two-strokes combustion chambers with inner and outer piston-couples and a linear electric generator with multi-movers in order to improve the system efficiency. The one-dimensional thermodynamics model of the combustion chambers and the model of the linear electric generator have been respectively derived mathematically. And the hybrid simulation model of the whole FPLG has also been established using MATLAB/SIMULINK. The features and operation process with basic igniting and scavenging strategy have been analyzed. It indicates that the novel FPLG has comparative potential and capacity for producing higher electric power and reaching higher power density