O desgaste de anéis de pistão e cilindro foi modelado através de um programa computacional que calcula as pressões hidrodinâmicas e de contato rugoso agindo nas superficies deslizantes de contato. Os valores previstos de desgaste são comparados com um ensaio em dinamometro de um motor diesel. / The wear of piston rings and cylinder liner was modelled through a computer code that calculates the hydrodynamic and roughness contact pressures acting in the contact surfaces. The predicted wear is compared with a 750 hours dynamometer test of a medium duty diesel engine

Neste trabalho avaliou-se experimentalmente a influência da onfiguração de bobinagem no comportamento mecânico de cilindros de compósito polimérico com bobinagem simétrica e assimétrica. Para tanto, foram fabricados pelo processo de bobinamento filamentar (filament winding) dois grupos de cilindros com extremidades abertas, que apresentaram alteração no posicionamento das camadas em relação ao plano médio, caracterizando laminados simétrico e assimétrico. No compósito deste estudo, utilizou-se uma matriz com sistema tricomponente com resina epoxídica e reforço de fibra de carbono. Para avaliação da resistência mecânica, os cilindros foram submetidos a ensaio hidrostático que consistiu da pressurização interna em dispositivo apropriado mediante a utilização de um fluido até que ocorresse o colapso. Adicionalmente, as deformações e os modos de falha dos dois grupos de cilindros foram analisados e comparados. A utilização de um programa de cálculo de elementos finitos permitiu concluir que esta ferramenta, muito usada em projeto, não consegue identificar tensões na orientação da fibra em cada uma das camadas do compósito, bem como tensões de cisalhamento interlaminares que surgem nos cilindros com configuração assimétrica. Os resultados dos ensaios mostraram que as configurações de bobinagem exercem influência no comportamento mecânico dos cilindros de material compósito, favorecendo a construção do tipo simétrica. / This work evaluated experimentally the influence of the stacking sequence of layers symmetrical and asymmetrical on the mechanical behavior of polymeric composite cylinders. For so much, two open-ended cylinders groups were manufactured by filament winding process, which had different stacking sequence related to the laminate midplane, characterizing symmetrical and asymmetrical laminates. The composite cylinders were made with epoxy matrix and carbon fiber as reinforcement. For evaluation of the mechanical strength, the cylinders were tested hydrostatically, which consisted of internal pressurization in a hydrostatic device through the utilization of a fluid until the cylinders burst. Additionally, were compared the strains and failure modes between the cylinders groups. The utilization of a finite element program allowed to conclude that this tool, very used in design, does not get to identify tensions in the fiber direction in each composite layer, as well as interlaminar shear stress, that appears in the cylinders with asymmetrical stacking sequence. The tests results showed that the stacking sequence had influence in the mechanical behavior of the composite cylinders, favoring the symmetrical construction.

Two different air-water interfacial flows are studied including plunging wave breaking and flow past a vertical surface-piercing circular cylinder using complementary CFDShip-Iowa version 6 including Cartesian grid solver and orthogonal curvilinear grid solver. The plunging wave-breaking process for impulsive flow over a bump in a shallow water flume has been simulated using the exact experimental initial and boundary conditions. The overall plunging wave breaking process is described with major wave breaking events identified: jet plunge, oblique splash and vertical jet. These major events repeat up to four times before entering the chaotic breaking. The simulations show a similar time line as the experiments consisting of startup, steep wave formation, plunging wave, and chaotic wave breaking swept downstream time phases. Detailed wave breaking processes, including wave profile at maximum height, first plunge, entrapped air bubble trajectories and diameters, kinetic, potential, and total energy, and bottom pressures are discussed along with the experimental results. The simulations show differences and similarities with other experimental and computational studies for wave breaking in deep water and sloping beaches. The geometry and conditions in the present study are relevant to ship hydrodynamics since it includes effects of wave-body interactions and wave breaking direction is opposite to the mean flow. Large-eddy simulation with the Lagrangian dynamic subgrid-scale model has been performed to study the flow past a surface-piercing circular cylinder for Re and Fr effect. The flow features near the air-water interface show significant changes with different Reynolds numbers from sub-critical to critical regime. It is shown that the interface makes the separation point more delayed for all regime of Re. Remarkably reduced separated region below the interface is observed for critical Re regime and it is responsible for much reduced wake and recirculation region behind the cylinder and it recovers in the deep flow. At different Fr, significant changes are shown on the air-water interface structures. At lower Fr, relatively smaller bow waves are observed in front of the cylinder with Kelvin waves behind the cylinder and small amount of free-surface roughness and turbulence are also seen in the wake region. For higher Fr, the bow wave increases remarkably with the larger wake region and deeper depression and it breaks with similar features of plunging breakers. Much more small air-water interface structures including splashes and bubbles are observed behind the cylinder. It is hard to distinguish the Kelvin waves behind the cylinder due to much larger free-surface oscillations and turbulence. As Fr increases, the Kelvin wave angle decreases and deeper and narrower depression region behind the cylinder are observed. The flow features around the cylinder are significantly changed due to this cavity region behind the cylinder.

<p>The residual gas fraction is an important parameter to get good performance with high efficiency and low emissions in the HCCI-engine. </p><p>The goal in this thesis is to formulate an algorithm for estimation of the residual gas fraction based on the cylinder pressure. The estimation is improved if also the exhaust gas temperature is used together with the cylinder pressure. </p><p>The formulated algorithm has then been tested on data from a single cylinder engine running in HCCI-mode during steady state conditions. An error of 4% was noted compared with the residual gas fraction obtained from simulations. </p><p>The thesis also investigates the effects of some possible error sources.</p>

<p>In recent years Hardware-in-the-Loop HiL, has gained more and more</p><p>popularity within the vehicle industry. This is a more cost effective research alternative, as opposed to the tests done the traditional way, since in HiL testing the idea is to test the hardware of interest, such as an electronic control unit, in a simulated (or partially simulated) environment which closely resembles the real-world environment.</p><p>This thesis is ordered by Daimler Chrysler AG and the objective of this thesis is the developing of a cylinder-by-cylinder model for the purpose of emulation of misfire in a four-stroke SI-engine. This purpose does not demand a precise modelling of the cylinder pressure but rather an adequate modelling of position and amplitude of the torque produced by each cylinder. The model should be preferebly computaionally tractable so it can be run on-line. Therefore, simplifications are made such as assuming the rule of a homogenous mixture, pressure and temperature inside the cylinder at all steps, so the pressure model can be analytical and able to cope with the real-time demand of the HiL. The model is implemented in Simulink and simulated with different sample rates and an improvement is to be seen as the sample rate is decreased.</p>

Experiments were conducted in a free-surface, re-circulating water channel to determine the dependence of spanwise flow uniformity in the near wake of a circular cylinder on the end conditions using Particle Image Velocimetry. The Reynolds number was 10,000. The end conditions consisted of plates with different leading edge geometries and configurations. A cylinder bounded by two endplates with sharp leading edge geometry generated the most uniform near wake. The horseshoe vortex dynamics in the cylinder/ wall and cylinder/endplate junctions were also studied. Upstream flow separation significantly altered the behavior of the horse shoe vortices. Periodic horse shoe vortex oscillation was found for experiments with the upstream flow attached; this periodic oscillation was disrupted with the presence of upstream flow separation. The endplate leading edge distance was also investigated. The oscillation frequency of the horse shoe vortex system was found to decrease with increasing leading edge distance.

Experiments were conducted in a free-surface, re-circulating water channel to determine the dependence of spanwise flow uniformity in the near wake of a circular cylinder on the end conditions using Particle Image Velocimetry. The Reynolds number was 10,000. The end conditions consisted of plates with different leading edge geometries and configurations. A cylinder bounded by two endplates with sharp leading edge geometry generated the most uniform near wake. The horseshoe vortex dynamics in the cylinder/ wall and cylinder/endplate junctions were also studied. Upstream flow separation significantly altered the behavior of the horse shoe vortices. Periodic horse shoe vortex oscillation was found for experiments with the upstream flow attached; this periodic oscillation was disrupted with the presence of upstream flow separation. The endplate leading edge distance was also investigated. The oscillation frequency of the horse shoe vortex system was found to decrease with increasing leading edge distance.

Paper making involves three fabrics: forming, pressing, and drying. The forming fabric is responsible for sheet forming, the initial dewatering of a low concentration pulp suspension into a wet sheet of paper. In the process of forming, topographical and hydrodynamic marks can be transferred from the drainage media (the forming fabric) to the sheet produced. An experimental investigation of a model forming fabric was performed to identify the geometric parameters having the largest influence on hydrodynamic wire mark. The data were also compared with the numerical simulations of Huang. To simplify the problem, justifiable engineering simplifications were made. The second phase (the fibres) was removed and the machine-direction filaments were neglected. This reduced the problem to investigation of flow through a bank of dissimilar cylinders. It was desired to find the most important geometrical parameter to reduce flow non-uniformity in the paper side flow field. Particle image velocimetry, pressure drop and flow visualization tests were conducted to investigate the flow through the array of cylinders. It was found that with a cylinder surface separation of 0.75$\times$ the paper side cylinder diameter the pressure drop tended toward the sum of the rows, and the paper side flow field was nearly identical to the paper side row only flow field, regardless of the backing side cylinder dimensions and configuration. It was seen that when the pressure drop through the bank of cylinders was equal to the sum of the rows' pressure drops the paper side flow field was the same as the paper side row only flow field. As such, pressure drop can act as an indication of when the machine side row will not affect the paper side flow field.

Paper making involves three fabrics: forming, pressing, and drying. The forming fabric is responsible for sheet forming, the initial dewatering of a low concentration pulp suspension into a wet sheet of paper. In the process of forming, topographical and hydrodynamic marks can be transferred from the drainage media (the forming fabric) to the sheet produced. An experimental investigation of a model forming fabric was performed to identify the geometric parameters having the largest influence on hydrodynamic wire mark. The data were also compared with the numerical simulations of Huang. To simplify the problem, justifiable engineering simplifications were made. The second phase (the fibres) was removed and the machine-direction filaments were neglected. This reduced the problem to investigation of flow through a bank of dissimilar cylinders. It was desired to find the most important geometrical parameter to reduce flow non-uniformity in the paper side flow field. Particle image velocimetry, pressure drop and flow visualization tests were conducted to investigate the flow through the array of cylinders. It was found that with a cylinder surface separation of 0.75$\times$ the paper side cylinder diameter the pressure drop tended toward the sum of the rows, and the paper side flow field was nearly identical to the paper side row only flow field, regardless of the backing side cylinder dimensions and configuration. It was seen that when the pressure drop through the bank of cylinders was equal to the sum of the rows' pressure drops the paper side flow field was the same as the paper side row only flow field. As such, pressure drop can act as an indication of when the machine side row will not affect the paper side flow field.

The steady problem of free convective heat transfer from an isothermal inclined elliptic cylinder and its stability is investigated. The cylinder is inclined at an arbitrary angle with the horizontal and immersed in an unbounded, viscous, incompressible fluid. It is assumed that the flow is laminar and two-dimensional and that the Boussinesq approximation is valid. The full steady Navier-Stokes and thermal energy equations are transformed to elliptical co-ordinates and an asymptotic analysis is used to find appropriate far-field conditions. A numerical scheme based on finite differences is then used to obtain numerical solutions. Results are found for small to moderate Grashof and Prandtl numbers, and varying ellipse inclinations and aspect ratios. <br /><br /> A linear stability analysis is performed to determine the critical Grashof number at which the flow loses stability. Comparisons are made with long-time unsteady solutions.