Abstract
In the present work is described the development of a new turbocharger modelling technique developed for Diesel engine Simulation and Diagnostic studies, as well as the validation and practical application of the proposed methodology. It involves turbocharger components simulation (compressor and turbine) using physical, meanline (1-D) models.The motivation for the work, overview and basics of internal combustion engine technology and applications are outlined in Chapter 1. Chapter 2 consist of a brief overview of Diesel engine charge induction and gas exchange methods, with special emphasis on turbocharging, being the focus of the thesis. Turbocharging history and development, as well as operating principle are presented, and recent developments on the field specifically regarding large scale engines are discussed. In Chapter 3 is conducted a review of the literature to present established methodologies for the simulation of compressor and turbine in engine simulation applications. It ...
In the present work is described the development of a new turbocharger modelling technique developed for Diesel engine Simulation and Diagnostic studies, as well as the validation and practical application of the proposed methodology. It involves turbocharger components simulation (compressor and turbine) using physical, meanline (1-D) models.The motivation for the work, overview and basics of internal combustion engine technology and applications are outlined in Chapter 1. Chapter 2 consist of a brief overview of Diesel engine charge induction and gas exchange methods, with special emphasis on turbocharging, being the focus of the thesis. Turbocharging history and development, as well as operating principle are presented, and recent developments on the field specifically regarding large scale engines are discussed. In Chapter 3 is conducted a review of the literature to present established methodologies for the simulation of compressor and turbine in engine simulation applications. It is thus verified the need for a new approach to turbocharger simulation in practical application that combines the benefits of simplicity and low computational time, as well as accuracy required for its implementation in practical simulation and diagnosis applications. The novelties of the approach, as well as a brief description of the developed methodology are presented in 3.2.In Chapter 4 are described in detail the methodology for compressor and turbine simulation implemented in the present work. It is also verified the ability of the developed models to predict compressor and turbine operation by comparing model predictions against available experimental maps of both turbine and compressors.Since the developed models are intended to be used together with a complete engine simulator in order to facilitate physically- based T/C simulation, in Chapter 5 are provided guidelines for linking the models with existing engine simulation software. More specifically, it is outlined the calibration of turbine and compressor model from experimental data (these consist of official engine shop test and NOx file data, that are always available for large marine engines). As part of the thesis, the models have been linked to two engine simulation platforms. The first is an in- house, NTUA Diesel engine performance and emissions prediction code. The second one is a commercial- general purpose engine 1-D modelling tool. This demonstrates model’s suitability for both research oriented activity and for turbocharger simulation in commercial/ practical applications. Extensive methodology is provided regarding the linking of the developed models with an engine simulator.In Chapter 6 are provided simulation applications of marine 2-stroke Diesel engine using the newly developed methodology. More specifically, in 6.2 is validated the new simulation methodology with respect to its ability to predict turbocharger, as well as engine performance. In 6.3 is tested the ability of developed models to predict turbocharger operation in T/C cut out conditions, i.e. in conditions that differ from the original matching of the T/C on the engine. This way it is tested the T/C methodology prediction accuracy outside of the model calibration range. Finally, in 6.4 is utilized the ability of developed T/C models to predict turbine maps with different geometrical characteristics in order to determine optimal matching for the power turbine of a turbocompound system fitted on a large scale marine 2-stroke engine.In Chapter 7 are presented applications of the new T/C model on the field of Diesel engine diagnostic studies. In 7.1 is evaluated the effect of ambient condition variation on a large scale marine Diesel engine operating parameters at low and high engine loading conditions, while in 7.2 it is defined the impact on engine operation from the degradation of air path components. The new methodology is used to provide insight specifically on two frequent modes of turbine blading degradation, namely increase of rotor- shroud clearance and fouling of the stator nozzle from deposits. Finally, in 7.3 it is proposed a monitoring method for engine air flow estimation and air path condition evaluation based on the developed T/C modelling methodology. For this reason it is applied for 2 cases of large scale Diesel engines for which experimental data were available. In Chapter 8 are outlined the conclusions of the thesis, the novelties compared with previous work and recommendations for future work in the field.
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