Browsing by Subject "Internal combustion engines"

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    Friction force measurement and analysis of the rotating liner engine
    (2005) Kim, Myoungjin; Matthews, Ronald D.
    As emissions regulations become more stringent and fuel prices increase at a significant rate, the fuel efficiency of piston engines becomes more important than ever. Since most of the engine’s friction losses are from the piston/ring assembly, it is indispensable to reduce the piston/ring assembly friction for better fuel economy. The Rotating Liner Engine (RLE) was developed to remove the boundary lubrication of the piston/ring assembly friction through cylinder liner rotation. Even though the RLE was initially developed mainly by Dr. Dardalis several years ago, the friction reduction effect of the RLE was not confirmed except via preliminary motoring tests using a crude dynamometer. The main purpose of this dissertation is to confirm the RLE effect on piston assembly friction reduction using sophisticated measurement methods. Three different friction measurement methods were applied in measuring the friction force difference between a baseline engine and a prototype RLE. Through the use of three different friction measurement methods, the friction reduction of the RLE has been confirmed via this dissertation research and each of the friction measurement methods is also compared based on its measurement results. The analysis of the friction mechanism of the baseline engine was performed using the instantaneous IMEP method and a commercial simulation program called RINGPAK. Through the use of experimental methods and the simulation, the friction mechanism of the piston/ring assembly is analyzed. The limitation of the experimental and the calculation methods is also discussed.
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    Predictive modeling of piston assembly lubrication in reciprocating internal combustion engines
    (2005) Xu, Huijie; Bryant, Michael D.; Matthews, Ronald D.
    The influence of piston assembly lubrication on the reciprocating internal combustion engine performance has received considerable attention for over halfcentury. An in-depth understanding of piston assembly friction and cylinder wear is crucial for achieving a better fuel economy and higher durability engine design. Early studies show hydrodynamic lubrication theory is applicable to the interface of piston assembly and cylinder liner throughout most of the piston middle stroke. However, when the piston motion ceases near top dead center (TDC) or bottom dead center (BDC) of the stroke, the piston velocity is not adequate to establish a hydrodynamic lubrication action. Lubricating films become very thin and contact between the surface asperities on the ring and the liner will support part of the piston ring restoring force. Therefore, wear on the cylinder liner surface may occur in the vicinity of TDC and BDC. Severe surface wear could affect the liner-ring sealing performance and result in excessive gas blow-by and fuel consumption. The objective of this dissertation is to develop a complete mathematical and computational model to predict the piston assembly friction loss in terms of the piston assembly design parameters and cylinder liner surface topography. Piston assembly experiences all three lubrication regimes including hydrodynamic, mixed and boundary lubrication. In order to simplify modeling, early studies usually considered either a full film hydrodynamic lubrication described by Reynolds equation, or a mixed film lubrication described by average Reynolds equation. While our model is based on the real surface interactive between piston assembly and cylinder liner, the latest tribology theory and effective numerical approach have been applied to model piston assembly friction problem. An integrated friction model over three lubrication regimes was developed based on both quasi-static and dynamic equilibrium conditions of the piston assembly. The new model was verified by experimental data with specified pressure and velocity boundaries. Finally, the friction characteristics of a rotating liner engine (RLE) design was investigated as an extension of the conventional piston assembly friction model.