In recent years, due to the stringent emission regulations worldwide, alternative fuels, such as ammonia, liquified natural gas (LNG), and alcohols, are gaining attention as potential substitutes for traditional fossil fuels. These fuels can potentially reduce greenhouse gas emissions, improve air quality, and reduce dependence on imported oil. Ammonia is a clean-burning and promising hydrogen carrier fuel with a high energy density. However, its low reactivity restricts the application of ammonia in the transport sector, whereas adding methanol as a combustion promoter enhances the reactivity of ammonia. LNG is another low-carbon energy resource gaining popularity due to its lower emissions and cost-effectiveness compared to traditional fuels such as gasoline or diesel. Alcohols, specifically propanol and butanol, which can be synthesized by converting renewable electricity into chemical energy, have high octane rating, making them ideal for use in high-performance engines. Moreover, due to a high hydrogen-to-carbon ratio, they are more reactive and able to burn more completely, which makes them well-suited for lean premixed prevaporized (LPP) combustion. Developing chemical kinetic models for alternative fuels is essential for understanding their combustion characteristics and optimizing engine performance. This thesis aims to develop and validate chemical kinetic models to investigate the combustion chemistry of ammonia-methanol blends, LNG mixtures, and propanol and butanol isomers. However, since each fuel presents its own challenges, different approaches were employed. For ammonia-methanol blend mixtures, it is essential to find appropriate cross carbon-nitrogen reactions. For each neat fuel, one reaction mechanism that can predict ignition delay times (IDT) with the least discrepancy was chosen from the literature. Those mechanisms were used as the seed mechanism in the software Reaction Mechanism Generator (RMG) to automatically generate a kinetic mechanism for the auto-ignition of ammonia-methanol blend mixtures. Further investigations of the H atom abstraction of methanol by NH2 radical were carried out using ab-initio calculations and compared to RMG estimates. Then, an in-house algorithm was implemented to reduce the size of the mechanism. The 16 LNG mixtures studied in this thesis contain C1-C5 alkanes, including two isomers of butane and pentane, to investigate the correlation between methane number (MN) and mixture composition. This correlation may predict the unknown MN of other LNG fuels, as MN is an important characteristic to determine the knocking properties of LNG. No reaction mechanisms in the literature have been validated against mixtures containing all C1-C5 alkanes. Thus, a comprehensive chemical kinetic mechanism for LNG mixtures and three reference mixtures containing methane and hydrogen has been developed by updating the NUIGMech1.3 mechanism. Similarly, for propanol and butanol isomers used as the electro-fuels (e-fuels) in the LPP approach in aviation, no reaction mechanism is available in the literature to describe their combustion chemistry under lean fuel-air conditions. The Sarathy2012 and Saggese2020 mechanisms were merged and modified to construct a comprehensive reaction mechanism for lean and ultra-lean conditions. The main experimental data used in this thesis to validate the developed chemical kinetic mechanisms for the studied fuels were the IDTs measured in our group in a high-pressure shock tube (HPST) and rapid compression machine (RCM). Only to provide the experimental data at a high-temperature range for ammonia-methanol blends to complete the database, IDTs of blending mixtures containing 0-20% methanol were measured in the HPST at the pressure of 10 bar, and temperatures between 1050 and 1550 K. Moreover, further validation of the developed mechanisms was carried out based on literature data on laminar burning velocity (LBV). The detailed developed mechanisms for each category of fuels satisfactorily predicted IDTs. In this thesis, sensitivity analyses of reaction rate constants, pathways analysis, and net rate of progress for each reaction were presented based on the developed mechanisms to provide valuable insights into combustion chemistry. Moreover, the developed mechanism for alcohols was used to investigate the impact of the combustion of propanol and butanol isomers on the environment by calculating their emissions contribution at two lean fuel-air conditions and compared to that of a rich condition. Overall, the chemical kinetic modeling results highlighted the importance of developing accurate and reliable chemical kinetic models to better understand the complex combustion chemistry of alternative fuels.


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    Titel :

    Detailed kinetic modeling in the energy conversion processes of low-carbon alternative fuels


    Weitere Titelangaben:

    Detaillierte kinetische Modellierung in den Energieumwandlungsprozessen von kohlenstoffarmen alternativen Kraftstoffen


    Beteiligte:
    Nadiri, Solmaz (Autor:in) / Universitätsbibliothek Braunschweig (Gastgebende Institution) / Fernandes, Ravi (Akademische:r Betreuer:in) / Schröder, Daniel (Akademische:r Betreuer:in) / Shu, Bo (Akademische:r Betreuer:in)

    Erscheinungsdatum :

    2024



    Medientyp :

    Sonstige


    Format :

    Elektronische Ressource


    Sprache :

    Englisch



    Klassifikation :

    DDC:    629.2





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