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The description of the supply pressure hydraulic circuit and the couplings between its components are presented. A comparison between simulations and experiments is carried out. Using some linear facilities, it is possible to conclude that the low frequency modes mainly correspond to the wave effects of hydraulic lines which connect valves to each other. In order to maintain a pressure in the supply circuit, an electronic pressure control is necessary. The design of a control law needs to build different linear models for different levels of pressure since the system is very non linear. Three transfer functions are found for three pressure levels. These transfer functions are very similar to the ones used by the automatic control department and obtained by experiments. Using these transfer functions it is possible to design the control law.

In the analysis of a cooling network, Computational Fluid Dynamics methods show an unquestionable usefulness. Nevertheless, this approach is largely limited for simulating the behavior of multidisciplinary components connected in a system. The lumped parameter approach suits these systems simulation. This awareness has led to the development of methods for structuring these kinds of problems. Applying the multiport method, the Thermal, Thermal-hydraulic and Cooling system libraries were created. These libraries comprise a set of basic and specific components from which it is easy to model large thermal-hydraulic and engine cooling networks. These basic and specific elements facilitate the study of phenomena whose knowledge is indispensable for the analysis of a whole system. An application of these libraries to a RENAULT car is presented.

The modeling of thermal phenomena in transient state in a vehicle, typically the studies of heat exchanges in the engine or the heat exchange in the exhaust line leads to the use of nodal methods or lumped parameters in systems approach. This lumped parameters vision has led to important formalization studies these past years leading to two important concepts: the multiport concept of which bond-graphs constitute the theoretical framework, and the polymorphic modeling concept leading to the definition of a minimum of basic elements allowing to build a maximum of situations. This article proposes to demonstrate how these concepts have been used to bring about the development of a library of basic elements. Its application is demonstrated by the modeling of the different modules composing the engine (lubrication, cooling, exhaust and metal masses).