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Localization of Combustion Engine Noise Origin with the use of Acoustic Emission
Rasch, František ; Mazůrek, Ivan (referee) ; Klíčník,, Martin (referee) ; Pražák, František (referee) ; Píštěk, Václav (advisor)
This doctoral thesis deals with the diagnostics of combustion engines, which have clearly suffered a mechanical damage. The text describes a basic principle of a diagnostics based on an observation of a noise of a running engine. There are mentioned the basic methods of a noise recording with direct conection to the specifics of measurement a running combustion engine noise. The introduction describes the spread of a vibration in solid structures. For the combustion engine vibration and source of noise is dedicated an independent chapter, which focuses on all noise generators, not only mechanical and thermodynamic but also noise caused by fluid and gas flowing. An integral part of the thesis is also a list and examples of signal processing, serving for efficient localization of the noise root cause. The noise statistics are compared with event diagram of engine investigation. Considering the information of the crank shaft position, we are then able to localize a possible root cause of the mechanical problem. For this purpose unique computer software for MS Windows operation system was developed. This system is able to generate event timelines of the piston engines. The inputs are basic engine data, such as the number of cylinders, ignition sequence, valve timing diagrams and information regarding two stroke or four stroke engine types. The program also allows us to detect a potential damage by direct comparison of the engine timeline and noise signal input. The thesis is also supplemented by measurements serving for key-parameter-diagnostics, i.e. the selection of the most suitable running engine operation. Comparison of different technical diagnostic approaches shows the suitability of mentioned diagnostic process.
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