Browse Publications Technical Papers 2011-36-0065
2011-10-04

Life Cycle Analysis of an Aeromodel Engine by Images Correlated with the Wear Evolution and Pontual Temperature of the Engine Head 2011-36-0065

There are increased demands for ever more efficient and friendly environmental automotive and model airplane engines. The burning parameters have still an insufficient reliability to describe the complexity of a flame, their mass and energy flows in an internal combustion engine. The aim of this paper is to furnish a visualization by SEM (Scanning Electron Microscopy) images for the development of oxides in specific orthogonal locii of two sets of chamber walls of Al-Si alloys that confine the flame (piston crown and engine head in the zone around its spark plug). They give a real description of the end of combustion and by means of the oxides generated they rescue some information on the flame combustion and oxidizing zone preferential directions during the engine life. To better understand step by step some engine life cycle aspects, it was investigated the wear evolution of the combustion chamber walls and the piston pin of an internal combustion engine, two strokes, 1.2 HP, that revealed a set of precious information about the engine head external wall temperature and internally the main pollutant oxides generated during its running. These data include material wear evidences shown for an engine in their conditions as acquired, after the running-in at 10⁵ and after 2x10⁶, 4x10⁶, 5x10⁶, 6x10⁶, 8x10⁶ and 12x10⁶ cycles. A significant sequence of images were collected since oxides nucleation, growth, collapse and debris detachment until adhesion of tribochemical films based on lubricant interactions into the engine combustion chamber. The intensifying of the service life generating mechanical power supports the deterioration of the Al-Si alloy of the piston crown and engine head - which temperature signal was measured at 1 Hz - due to adhesive, delamination, erosive and mainly oxidative wear. The steel pin that links the piston with the connecting rod suffers the additional contribution of the contact fatigue wear mechanism. The aim of this study was to investigate the images by a set of analysis including since images obtained by a digital camera, Optical Microscopy, SEM-EDS (Scanning Electron Microscopy and X-Rays Dispersive Energy Spectroscopy) until spectrogram by XRD (X-Rays Diffraction) and microanalysis by EDS (X-Rays Dispersive Energy Spectroscopy). Why did silicon readily form oxides with carbon, iron, potassium, wolfram and nitrogen at the piston crown but not so readily at the engine head at 6.2x10⁶ life cycling of engine? Why amorphous and crystalline oxides are formed simultaneously? Genesis, cracking, detachment, adhesion and polymerization of amorphous and crystalline oxides and their tribochemical contributions to lubricant interactions were observed and require additional studies.

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