A contribution to the global modeling of heat transfer processes in Diesel engines

Abstract

Current challenges in research and development of powertrains demand new computational tools capable of simulating vehicle operation under very diverse conditions. This is due, among other reasons, to new homologation standards in the automotive sector requiring compliance of exhaust emissions regulations under any possible driving condition on the road. Global engine or vehicle models provide many advantages to engineers because they allow to reproduce the entire system under study, considering the physical processes that take place in different components and the interactions among them. This thesis aims to enable the modeling of heat transfer processes in a complete engine simulation tool developed at CMT-Motores Térmicos research institute. This 0D/1D simulation tool is called Virtual Engine Model (VEMOD).The development of heat transfer models comprises the engine block and the ancillary systems. The model of heat transfer in the engine block deals with the central problem of in-cylinder convection by means of a combination of experimental research, CFD simulation and multizone 0D modeling. The other thermal processes present in the engine block are examined in order to implement suitable submodels. Once the model is complete, it undergoes a validation with experimental transient tests. Afterwards, the ancillary systems for engine thermal management are brought into focus. These systems are considered by means of two new models: a model of heat exchangers and a model of thermo-hydraulic circuits. The development of those models is reported in detail.Lastly, with the referred thermal models integrated in the global simulation tool, a validation study is undertaken. The goal is to validate the ability of the Virtual Engine Model to capture the thermal response of a real engine under various operating conditions. To achieve that, an experimental campaign combining tests under steady-state operation, under transient operation and at different temperatures is conducted in parallel to the corresponding simulation campaign. The capacity of the global engine simulations to replicate the measured thermal evolution is finally demonstrated.As you set out for Ithaka hope the voyage is a long one, full of adventure, full of discovery. Cavafy AcknowledgmentsA PhD is a long voyage of discovery and personal growth. Far from being a solitary journey, there are many people who intervene to make possible that all efforts reach a good conclusion. Having reached this point, I wish to acknowledge all people and institutions that have contributed to this thesis by one means or another.First of all, I want to thank my PhD supervisor, Prof. Pablo Olmeda, for his teachings and support over these years. I'm also grateful to Dr. Antonio García for sharing with me his invaluable knowledge about research communication. Another important figure in this period has been Dr. Jaime Martín, from whom I have learned a lot by collaborating in research projects. Also thanks to Dr. Francisco Arnau, for his compromise in building the Virtual Engine...