| dc.description.abstract | The maritime industry is facing significant changes in the design of marine machinery systems due to stricter regulations on the emission of air pollutants and greenhouse gases and the need for increased energy efficiency. Designing compliant and efficient marine machinery systems depends on developing and implementing new technology and new technical solutions. This is a significant change for the deep sea sector, where the current marine machinery system concepts have changed little since the introduction of the turbocharged heavy fuel oil burning large two-stroke marine diesel engine, while for the offshore sector, additional technical solutions and systems add additional complexity to already advanced systems. Due to the geographic application of regulations, there are reasons to believe that a more diverse set of system solutions will appear suited to fit the trade, operation profile and area of operation. Moving from a standardized design to selecting between multiple viable designs or developing custom designs poses a significant challenge for marine machinery system designers. Designers need methods for evaluating suggested designs and for building confidence in novel systems prior to system realization. System modeling and simulation are considered important steps in our ability to develop novel systems. Successful use of system modeling and simulation increases our ability to address systems-related problems, such as the complexity of the interaction between components and sub-systems, and provides designers with a methodology to evaluate concepts using virtual prototyping. Although a promising method for virtual prototyping, system modeling and simulation faces challenges such as the following:
• How do we identify the relevant problem and represent the relevant physical phenomena using mathematics?
• How do we gather required data needed for a model to represent a physical component or system?
• How do we ensure that the model developed is able to answer the question being asked? How do we assemble models into total system models?
• How do we develop models that have equation structures for which we have efficient numerical solvers?
• How do we extract understanding and knowledge from simulation results?
• How do we make decisions based on simulation results?
These challenges, combined with the challenges facing the maritime industry, lead to the overall research goal of this thesis:
Improve the methods for system modeling and simulation in the maritime industry in order to increase our ability to evaluate energy efficient system concepts for reducing the emissions of air pollutants and CO2.
This thesis contributes to addressing these challenges by the following:
• Developing and testing a modeling approach for heat exchangers and heat exchanger networks to resolve common issues with the equation structure and the simulation of such networks. The modeling approach includes heat exchanger model reuse and easy heat exchanger network model assembly.
• Developing three interchangeable SCR system models with different model fidelities suitable for different trade-offs between simulation speed and result accuracy.
• Studying the potential of combining hybrid turbocharging with pre-turbine SCR systems on marine two-stroke diesel engines running on high-sulfur heavy fuel oil. The purpose of the system is to increase the operating range and improve system fuel efficiency.
• Addressing how to evaluate complex system models in an operational context and evaluating the effect of selecting different model fidelities when evaluating marine machinery systems in an operational context.
• Providing direction to generate scenarios that are useful for active searching for system-specific properties, such as emergent behavior. | nb_NO |
