Conceptual design of hydraulic systems for automotive engine applications : simulation, optimisation and testing

Sammanfattning: The main contribution of this thesis lies in the area of systems design, and especially of such systems that involve several engineering domains, so-called multidomain or heterogeneous systems. The design of these systems is concerned with a need for efficient tools, especially in the early conceptual phase of the development process.The scope of this work are heterogeneous systems and hydraulic systems for automotive engines, and gasoline engines in particular. To date the use of such systems in automotive engines is restricted to a small number of applications, predominantly lubrication systems. Lubrication systems have very much in common with traditional fluid power systems, with the major difference that the power in form of pressure and flow is used to transport a lubricant and not for actuation purposes. Temperature aspects as they are treated in this thesis are significant for lubrication system design in combustion engines, as the oil is used both for lubrication and cooling.Another application area for hydraulic systems in vehicle engines is carnless valve trains, where the inlet and exhaust valves of the engine are operated by hydraulic means. In this manner the losses which arise due to gas exchange can be significantly reduced. Such a variable valve train system is proposed in this thesis, where power consumption and robust operation are put in the foreground. In the design of new system concepts there are usually some critical components where the performance has to be verified at an early design stage. In the case of the proposed valve train system, both the hydraulic switching and check valves prove to be key components. System design implicates validated component models which made in-depth modelling and model identification issues the cornerstones of this work.This thesis discusses numerical simulation and optimisation techniques, both as analysis and design tools for automotive engine systems. In the case of simulation-based optimisation, an optimisation strategy is used to vary a set of design parameters in order to satisfy an objective function. The formulation of this objective function is obviously crucial for the optimisation output. In this thesis guidelines for the creation of such an objective function are given where the involvement of the design team is considered important.