Experimental and modelling studies of natural gas and gasoline surrogate blends
Patel, Vaibhav
Patel, Vaibhav
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Publication Date
2023-03-09
Type
Thesis
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Abstract
Combustors rely heavily on fossil and/or bio-derived fuels that all produce significant quantities of greenhouse gas (GHG) emissions. Hence, the successful development of advanced combustors requires predictive chemical kinetic models to emulate the oxidation of natural gas and gasoline fuels and an in-depth understanding of the fuel ignition kinetics. These chemical kinetic models require experimental data for their validation over a wide range of pressure, temperature, and mixture composition conditions. Experimental facilities such as shock tubes and rapid compression machines are well suited to provide these validation targets. The potential future fuels and fuel blends studied in this thesis add to the growing database of ignition delay times (IDTs) that includes natural gas containing C1 – C3 alkanes and alkene, and their blends, three pentanol isomers (1-, 2-, and 3-pentanol) and gasoline surrogates including toluene/n heptane/iso-pentane/ethanol blends, cyclopentane/toluene/di-isobutylene/iso-octane blends. A thorough understanding of the ignition kinetics of natural gas and gasoline is necessary to improve sustainable advanced fuel technologies as we face economic, technological, and societal challenges. Therefore, natural gas (NG) blends and gasoline surrogates (GS) have been formulated to emulate the fuel properties of commercial fuel to conduct fundamental experiments and predictive simulations. Since the early 1960s, autoignition studies of NG have been conducted using single, binary, ternary, or multi-component (C1 – C7) mixtures. Similarly, since the early 2000s, GS combustion studies have been performed by adopting single, binary, ternary, or multi component (C4 – C10) mixtures, including oxygenated fuels such as ethanol, butanol, pentanol, MTBE, etc., as promising alternative fuels and blending components/additives for gasoline and its surrogates. Several studies have shown the importance of NG and GS mixtures that significantly influence the auto-ignition behaviour, which is a critical parameter for gas turbines, spark-ignited (SI), and homogeneous charge compression ignition (HCCI) engines. Therefore, it is essential to understand the oxidation of various NG and GS mixtures to increase engine efficiency and reduce emissions. This thesis focuses on building a comprehensive experimental IDT database that includes NG containing C1 – C3 alkanes and alkene, and their blends, three pentanol isomers (1-, 2-, and 3- pentanol) and GS containing toluene/n-heptane/iso-pentane/ethanol blends and cyclopentane/toluene/di-isobutylene/iso-octane blends. The experiments have been performed in two independent and complementary experimental facilities, a rapid compression machine (RCM) and a high-pressure shock tube (HPST). Depending on the fuel mixture’s reactivity, the RCM is used for the low- to intermediate-temperature regimes, while the HPST is used to study the intermediate- to high-temperature regimes. The IDT measurements were performed over a wide range of temperatures (650 – 1500 K) and at pressures p = 15 – 40 bar and equivalence ratios φ = 0.5 – 2.0. Furthermore, additional RCM experiments for these cyclopentane blends (Fuels 1–4) and E10-Fuel 4 were carried out at φ = 0.8 and p =25 and 40 bar. However, the IDT data are not presented in the thesis due to a confidentiality agreement with Shell Global Solutions. These IDT data provided in thesis are essential for developing and validating a reliable chemical kinetic mechanism for describing the oxidation of natural gas and gasoline mixtures. Therefore, a detailed chemical kinetic model (Galway_GSMechV1) has been formulated by adding cyclopentane, iso-octane, di-isobutylene, and toluene sub-mechanisms from the literature and using NUIGMech1.2 as the base chemistry. This thesis provides a substantial amount of IDT measurements to the growing database across a wide range of low to intermediate molecular weight hydrocarbon fuels and their blends. It also provides a single chemical kinetic mechanism for these fuels and can act as the basis for the further development of gasoline surrogate mechanisms. These IDT provide an understanding of the ignition kinetics of the studied hydrocarbon mixtures and help improve the development of predictive models for multi component GS mixture blends.
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NUI Galway