Th. licence--Droit--Poitiers, 1862-01-11.

Th. licence--Droit--Paris, 1878-08-05.

Th. licence--Droit--Strasbourg, 1866-08-24.

Th. licence--Droit--Paris, 1880?

Th. licence--Droit--Paris, 1879-04-03.

Th.--Méd.--Paris 11--Kremlin-Bicêtre, 1978. N°: 120.

<p>The finite response time of the turbocharger is the most notable effect oftransient operation on a turbocharged diesel engine. To fulfil future emission requirements high amounts of transient EGR will be required. This impliesthat advanced turbocharger systems have to be introduced to enable high boost pressures with improved or at least maintained response time. The increased amount of tunable parameters from the more advanced turbocharging system will make it difficult to optimise the engine experimentally. Therefore the wish is to optimise the engine numerically, however this is a difficult task which demands more knowledge within the field of modelling the gas exchange system and its components, which is the aim of the present work. Engine simulations have been performed in the 1-dimensional fluid dynamic code GT-Power for transient operation and validated with engine measurements. The turbine was modelled according to the state of the art which is via look-up tables with measured turbine performance data from a steady-flow rig and used under the assumption that the turbine behaves in a quasi-steady manner. Turbine performance data was also obtained via the semi-empirical turbine design software, Rital for comparison. A heavy-duty diesel engine has been modelled with two different gas exchange system configurations. The standard configuration with a single twin-entry turbine and a rebuilt gas exchange system including a two-stage turbocharging system and high pressure loop for EGR. The results shows that it is difficult to predict the performance of the gas exchange system and its components, especially the turbine performance. When trying to predict turbine performance under transient operation the difficulties added, compared to stationary operation are long scale transients as wall temperature gradients in the cylinder and the exhaust manifold which directly influences the amount of isentropic energy to the turbine. This makes it even more difficult to predict the isentropic exhaust gas energy content compared to stationary operation, which is difficult to measure and therefore to state how well the turbine model actually performs. However, even though it is difficult to predict engine performance in detail the models have proved to be useful for concept studies as a help in engine design.</p>

<p>The general trend toward increased use of computer models and simulations during product development has led to a need for accurate and reliable product models. The function of many products relies on contact interfaces between interacting components. To simulate the behavior of such products, accurate models of both components and interfaces are required. Depending on the purpose of the simulation, interface models of different degrees of complexity are needed. In simulation of very large systems with many interfaces, it might be computationally expensive to integrate detailed models of each individual interface. Condensed models, or abstractions, that describe the interface properties with a minimum of degrees of freedom are therefore required.</p><p>This thesis deals with mechanical interfaces with an emphasis on friction. In the four appended papers friction models are discussed in terms of condensed models, as well as in terms of more detailed contact models. The aim is to study how friction can be modeled in behavioral simulation of products and to discuss the convenience and relevance of using different types of friction models as building blocks of a system model in behavioral simulations.</p><p>Paper<b> A </b>presents a review of existing condensed friction models for sliding contacts under different running conditions and discusses the models from both simulation and tribological points of view.</p><p>In papers<b> B </b>and <b>C</b> a simplified contact model, called the elastic foundation model, is used to model friction in a boundary-lubricated rolling and sliding contact. The model is integrated in a dynamic rigid body model of a mechanical system, the system behavior is simulated, and the result is compared with experimental results.</p><p>Paper <b>D</b> discusses the application of the elastic foundation model to rough surface contact problems and investigates how the error in the elastic foundation results depends on surface roughness.</p>

Thesis (M.S.)--University of Michigan, 1967.

Thesis (M.S.)--University of Michigan, 1967.