Engine downsizing is one of the most effective ways to reduce vehicle fuel consumption. Highly downsized (>50%) 4-stroke gasoline engines are constrained by knocking combustion, thermal and mechanical limits as well as high boost. Therefore a research work for a highly downsized uniflow 2-stroke engine has been proposed and carried out to unveil its potential. In this study, one-dimensional (1D) engine simulation and three-dimensional (3D) computational fluid dynamic analysis were used to predict the performance of a boosted uniflow 2-stroke DI gasoline engine. This was experimentally complemented by the in-cylinder flow and mixture formation measurements in a newly commissioned single cylinder uniflow 2-stroke DI gasoline engine. The 3D simulation was used to assess the effects of engine configurations for engine breathing performance and in order that the design of the intake ports could be optimised. The boundary conditions for 1D engine simulation were configured by the 3D simulation output parameters, was employed to predict the engine performance with different boost systems. The fuel consumption and full load performance data from the 1D engine simulation were then included in the vehicle driving cycle analysis so that the vehicle performance and fuel consumption over the NEDC could be obtained. Based on the modelling results, a single cylinder uniflow 2-stroke engine was commissioned by incorporating a newly designed intake block and modified intake and exhaust systems. In-cylinder flow and fuel distribution were then measured by means of Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) in the single cylinder engine. The numerical analysis results suggested that a 0.6 litre two-cylinder boosted uniflow 2-stroke engine with an optimised boosting system was capable of delivering comparable performance to a NA 1.6 litre four-cylinder 4-stroke engine yet with a maximum 23.5% improvement potential on fuel economy. Furthermore, simulation results on in-cylinder flow structure and fuel distribution were then verified experimentally.

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A numerical model for simulating a dry forward in-situ combustion process in two dimensions, was developed. The primary focus is on the simulation of the compositional changes that take place inside the porous medium during the running of the process. The model allows any number of hydrocarbon components and six others, namely, liquid water, water vapour. oxygen, nitrogen, carbon dioxide, and carbon monoxide. It describes the flow of water. oil, and gas, and includes the gravity and capillary effects. The vapourisation and condensation effects of both hydrocarbons and water enhanced the heat transfer, primarily by conduction and convection, ahead of the combustion front. Equilibrium calculations are performed on the components in both the liquid and vapour phases. The changes in pressure, temperature, and flUid compositions govern the direction of the interphase mass transfer. Heat is generated by two types of reaction, namely, low temperature oxidation and burning of the crude oil. The model allows the movement of a thin burning front inside the burning cell. It is found to give a better temperature profIle. representative of the combustion process. Oxygen mole fraction is calculated throughout the porous medium according to the reaction kinetics. thus no assumption is made regarding the degree of oxygen consumption. The effects of oxygen bypassing caused by the kinetic-limited combustion is therefore represented. A total of 18 components were used in the computer runs. Results show the preferential vapourisation of the lighter components in the vicinity of the high temperature burning front. The lighter components then move towards the producer. faster than do the heavier ones. This segregation produce fuel that is heavier than the original oil. High temperature in the upstream cells causes a reduction in the oil viscosity. which in turn increases its mobility, thus transporting more heat downstream. The rise in temperature in the condensation cell results in a decrease in the rate of water vapour condensation; extending the condensation zone downstream. In the high pf(>ssure run. all the hydrocarbon in the downstream cells condenses. In the burning cell however. both the vapour and the liquid phases are present due to the high front temperature. The vapour phase is richer in the light components while the liqUid is richer in the heavy components.

<p>This thesis describes a grey-box model for the dimensionalstability properties (i.e. curl and twist) of the carton boardproduced at AssiDomän Frövi paper mill in Sweden.AssiDomän Frövi AB is one of Sweden major cartonboard manufacturer, and produces some 350000 ton of board peryear.</p><p>Curl is defined as the departure from a at form, and it mayseriously affect the processing of the paper. For this reason,customers impose quite restrictive limits on the allowedcurvatures of the board. So, it is becoming more and moreimportant to be able to produce a carton board with a curlwithin certain limits. Due to the economic significance of thecurl problem, much research has been performed to find sheetdesign and processing strategies to eliminate or reducecurl.</p><p>The approach we used to tackle this problem is based ongrey-box modelling. The reasons for such an approach is thatthe physical process is very complex and nonlinear. The inuenceof some inputs is not entirely understood, and besides itdepends on a number of unknown parameters andunmodelled/unmesurable disturbances.</p><p>One of the main part of the model is based on classicallaminate theory which is used to model the dimensionalstability of multi-ply board. The main assumption is that eachlayer is considered as an homogeneous elastic medium.</p><p>The model is then complemented with a sub-model forunmodelled/umeasurable disturbances which are described asstates of a dynamical system, and estimated by means of anextended Kalman filter.</p><p>The simulated curvatures show a general agreement with themeasurements. However, the prediction errors are too large forthe model to be used in an effective way, and a bigger efforthas to be carried out in order to improve the physicalsub-models.</p><p>A chapter of this thesis discusses the modelling of thewet-end part of the paper machine with Dymola, a modelling toolfor simulation of large systems based on Modelica language.</p>

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