Virtual prototyping and optimisation of microwave ignition devices for the internal combustion engine

Schöning, Christoph (2014) Virtual prototyping and optimisation of microwave ignition devices for the internal combustion engine. PhD thesis, University of Glasgow.

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The internal combustion engine (ICE) has been used in automotive vehicles without any significant improvement in energy efficiency for over a hundred years. There are several possibilities for developing a ‘greener’ and more powerful engine such as the homogeneous charge microwave ignition (HCMI) system. In this thesis, the HCMI system is analysed and investigated through simulation based ‘virtual prototyping’ in combination with an intelligent optimisation and a Computer-Automated Design (CAutoD) framework. The intention is to analyse and develop designs which could be used to transform the existing ICE ignition system to the HCMI system with minimal modifications to the existing engine. With the help of the finite element method (FEM), the microwave induced electromagnetic field in the engine cylinder is first simulated for `virtual prototyping' using a computer model. This then takes the prototyping methodology one step further, by replacing the process of human tuning of the prototypes with a computer-automated search process using computational intelligence. To realise this, an interface between the FEM model and the CAutoD framework is designed using the Application Programming Interface (API) of the FEM simulation software. This connection facilitates a rapid exchange of data between the simulation model and the search algorithm. Thus, rendering it possible to accommodate a wider exploration or a higher simulation resolution for superior and more accurate prototyping. Another contribution of this thesis is the improvement of the search performance, including the combination of deterministic and non-deterministic search algorithm as well as using a new technique to solve optimisation problems without using the frequency as an input variable. The knowledge gained from the analysis of nature-inspired algorithms is used to perform a pre-evaluation and hence to provide a population which guides a non-deterministic search towards potentially optimal directions for the global maximum. A CAutoD system is then developed to optimise digital prototyping on various aspects of the ignition device for the HCMI system. This helps deepen the understanding of relationships between the characteristic outputs of a design, and the input parameters that affect the performance of the device. The CAutoD system is first applied to a basic cylinder model, with one single antenna in the middle, to analyse the single variable changes for the antenna designs. It is discovered that the inner antenna length has a significant impact on the maximum electric field intensity inside the engine cylinder. Then it is applied to the design process involving multiple variable changes for the global optimum electromagnetic performance. The results are presented in multi-dimensional graphs, which illustrate the relevant relationships between the different input variables. For example, it is revealed that the resonance frequency is affected more by the piston position than by the antenna length, which underlines the importance of the correct and exact timing advance and control of the ignition event. Subsequent to the extensive and systematic analysis of different antenna designs and input variables, Computer-Automated Design (CAutoD) has been applied to various designs to expand the understanding and virtual prototyping of the HCMI system. The criterion for the best design is to first provide the highest possible electromagnetic propagation performance within the cylindrical cavity by using the lowest microwave input power. With this, the reection of the microwave energy from the cylinder back to the microwave source, under the geometric conditions of the cylinder and antenna model, will also be minimised. During the search process, the default antenna model was extended with an additional antenna, which leads to a dramatic decrease in the field, once the additional antenna is introduced. This determines, that any antenna at the outer shield of the coaxial cable and inside the cylinder head, interferes with the electromagnetic propagation inside the cavity and lowers the propagation performance. The results show that this field will break down the air-fuel mixture inside the cylinder because the field strength is comparable to that, created by a spark plug. Hence, a HCMI system can be designed to replace a spark ignition system without requiring physical modifications to the engine cylinder.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Colleges/Schools: College of Science and Engineering > School of Engineering
Funder's Name: UNSPECIFIED
Supervisor's Name: Li, Prof Yun and Howell, Dr John
Date of Award: 2014
Depositing User: Christoph Schöning
Unique ID: glathesis:2014-5487
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 25 Sep 2014 10:56
Last Modified: 16 Oct 2017 09:12

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