Thesis (M.A.)--University of Hong Kong, 1966. / Also available in print.

There are two important omissions in the literature on bore polishing, firstly there is no evidence of the successful development of a reliable tribo test device to simulate bore polishing and secondly, the mechanism of bore polishing has not been fully defined. The aims of this study were: 1. To establish the principal characteristics of bore polishing In engines. 2. To produce bore polishing in the laboratory. 3. Differentiate between two reference oils in a laboratory tribo test. 4. To understand the mechanism of bore polishing. The principal characteristics of bore polishing have been identified by the examination of Tornado cylinder bores from an engine test. The graphite structure is visible on the surface which has a surface finish of less then 0.125 micro-m in C.L.A. value. The components used in these tests were a grey cast iron piston ring running on a grey cast iron cylinder bore typically used in commercial engines. A reciprocating tribo test was used to distinguish between the two reference oils. The result showed higher friction, wear and a smoother surface with the oil causing bore polishing compared to the other oil which did not produce bore polishing. Adding carbon, taken from the wall of a piston used in an engine test, to the lubricant in the laboratory tribo test produced a phenomenon resembling bore polishing. Comparisons have been made between the tribo test results and service engines and a good correlation has been obtained. Several analytical techniques have been used and the knowledge of bore polishing has been advanced. In particular, it is suggested that a combination of two processes, one mechanical and the other chemical, are associated with bore polishing. Four wear mechanisms were identified during this investigation; abrasion, delamination, corrosion and adhesion.

For oblique and normal water waves at various frequencies, the use of moored cylinders as breakwaters is considered numerically using linear three-dimensional analysis. The breakwater can be used by itself for protection of small structures or as a series of cylinders to protect a harbor, shoreline, or moored vessel from the destructive energy associated with incident water waves. The breakwater is completely submerged below the free surface and is attached to the ocean floor with six symmetrically configured mooring lines. The cylinder is filled with air and the mooring lines remain taut during the structure's motion. Six degrees of freedom describe the motion of the breakwater and additional degrees of freedom are introduced as the cables are modeled with the use of lumped masses connected with springs. The fluid is assumed to be inviscid and incompressible, so that the velocity field can be written as the gradient of the velocity potential. A boundary integral method is used to solve the integral equations that define the external fluid flow. Free vibrations of the cylinder in both air and water are considered and "dry " and "wet" natural frequencies are computed. Motions caused by water waves are studied to establish the effect of certain parameters on the effectiveness of the breakwater. The transmission coefficient is shown to be somewhat misleading when compared to plots that show the spatial variation of the wave amplitude. / Master of Science

The subject of this master´s thesis is the design of a single-purpose assembly device for pressing round seats into the cylinders of an air conditioning compressor. The whole thesis leads to a complete 3D model of the machine, including drawings. The 3D model and drawings were created in SOLIDWORKS.

To meet the constantly restricting emission regulations and develop better strategiesfor engine control systems, thorough knowledge of engine behavior is crucial.One of the characteristics to evaluate engine performance and its capabilityfor power generation is in-cylinder pressure. Indeed, most of the diagnosis andcontrol signals can be obtained by recording the cylinder pressure trace and predictingthe thermodynamic variables [3].This study investigates the correlation between the in-cylinder pressure andtotal trapped gas mass [10] with the main focus on estimating the in-cylinder gasmass as a part of a lab measuring procedure using the in-cylinder pressure sensors,or as a real-time method for implementation in an engine control unit thatare not equipped with the cylinder pressure sensors. The motivation is that precisedetermination of air mass is essential for the fuel control system to convey themost-efficient combustion with lower emissions delivered to the after-treatmentsystem [10].For this purpose, a six-cylinder Diesel engine is used for recording the enginespeed, engine torque, measuring the cylinder pressure profile resolved bythe crank angle, intake and exhaust valve phasing as well as intake and exhaustmanifold pressures and temperatures. Next, the most common ways of estimatingthe in-cylinder trapped gas mass are studied and the most reliable ones areinvestigated in-depth and a model with the acceptable accuracy in different operatingconditions is proposed, explained and implemented. The model in has athermodynamics basis and the relative errors is lower than 3% in all the investigatedtests. Afterwards, the most important findings are highlighted, the sourcesof errors are addressed and a sensitivity analysis is performed to evaluate themodel robustness. Subsequently, method adjustment for other operating conditionsis briefly explained, the potential future work is pointed and a complete setof results is presented in Appendix B.

To monitor and control the combustion in a diesel engine one can study the speed signal from the flywheel. The idea is that if individual cylinders give different amount of torque this will lead to variations in the flywheel speed. A model which describes the cylinder torque based on flywheel speed can be used to estimate the torque from individual cylinders. With this new knowledge of the individual performance of each cylinder the engine can be balanced. The balancing aim at making the speed of the flywheel more even but also required a model with estimated cylinder torque as input. This model may also be used for testing new control algorithms easily and gaining understanding of the dynamics. In this thesis a time dissolved model is constructed to describe the cylinder pressure-, crankshaft-, flywheel and damper dynamics. The model is based on a physical point of view by approximating the system into nodes containing mass, stiffness and friction. The inputs into the model are injection data from the engine management system (EMS) and a torque from a drive line. Ways to reduce the complexity of the model are investigated in order to invert the model to estimate the injection data based on flywheel speed measurements. Measurementsare done in a test bed to receive data required for model simulation and validation. The result is that the main behavior of the dynamics is caught. The self oscillation behaviors in some operating points are however not caught which indicates that the model can not explain all behaviors. A reduced model works almost as well but of course looses more of the non stiffness behavior. As expected, the model equations can not be solved in real time. The result of the inverted reduced model depends on the flywheel signal. When the signal contains little non stiffness behavior the result is good. An observer model based on the reduced model is suggested and tested in order to estimate the indicated torque from flywheel data. The observer manages to detect errors in the injection.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An edge-based hybrid finite element boundary integral (FE-BI) method using cylindrical shell elements is described for analyzing conformal quarter-wave patches embedded in a circular cylinder. Special care is also taken to deal with weight functions, dyadic Green’s function, and feed model. Some types of the patch arrays embedded in different circular radius have been developed. The tests of their VSWRs and radiation characteristics are in good agreement with the theoretical results.

No description available.

No description available.

Laminar natural convection heat transfer from the vertical surface of a cylinder is a classical subject, which has been studied extensively. Furthermore, this subject has generated some recent interest in the literature. In the present investigation, numerical experiments were performed to determine average Nusselt numbers for isothermal vertical cylinders (103 < RaL < 109, 0.5 < L/D <10, and Pr = 0.7) with and without an adiabatic top in a quiescent ambient environment which will allow for plume growth. Results were compared with commonly used correlations and new average Nusselt number correlations are presented. Furthermore, the limit for which the heat transfer results for a vertical flat plate may be used as an approximation for the heat transfer from a vertical cylinder was investigated.