Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.13/805503
- Title
- Study on the inhibition mechanisms of CBrF₃, CF₃I and C₃F₇H in methane fuelled premixed flames
- Author/Creator
-
Luo, Caimao
- Institution
- University of Newcastle. Faculty of Engineering and Built Environment, School of Engineering
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This dissertation is focused on developing updated inhibition kinetics of hydrofluorocarbon (HFC), CBrF₃, CF₃I and C₃F₇H and modelling of inhibition phenomenon using the updated kinetic mechanism. The thesis is divided into three bodies of work: the first is presented in three chapters, which outlines the purpose of the study, a review of the relevant literature and numerical techniques developed and applied for kinetic analysis; the second part of the thesis involves updating CBrF₃, CF₃I and C₃HF₇ inhibition mechanisms while the final part applies the three updated kinetic mechanisms to specific applications. In the first section, the background of the study, the literature related to elementary reactions of hydrofluorocarbon (HFC), CBrF₃, CF₃I and C₃HF₇ inhibition mechanisms and numerical techniques used to obtain insight to the complicated kinetics of hydrocarbon flames inhibited by halon and halon alternatives are presented. In the second section of the thesis, based on comparing the burning velocity and flame structure of methane-air-CBrF₃ (or CF₃I or C₃F₇H) systems, the inhibition kinetics of CBrF₃, CF₃I and C₃F₇H are updated. At the same time, the inhibition mechanism based on Br, I or H atom flux, in addition to the more standard C atom flux, is assessed. The higher inhibition capability of the bromine or iodine containing compounds is assessed by identifying and analysing the inhibition cycles, by which the Br or I containing compounds are regenerated and enhance scavenging of radicals. Several inhibition cycles are revealed using the Br or I atom flux analysis. The third section of this dissertation pursues application of the inhibition mechanisms, which ultimately aims to solve specific fire-safety related problems. The first application is an assessment of the flame suppressing effect of combinations of CF₃I with hydrofluorocarbons (HFCs), such as C₃HF₇, C₂HF₅, CHF₃, and fluorocarbons (FCs), such as C₂F₆. The inhibition efficiency is divided into physical and chemical effects, with chemical influences decreasing once the agent concentration exceeds a specified value termed the agent saturation limit. An assessment of whether other suppressants will change the agent saturation limit and determine whether the combined chemistry or physical effects of two agents is coupled or uncoupled, whether or not the combined chemistry or thermal physics effect of two agents is independent each other, is presented. Finally, we determine whether or not the existence of other agent influences the chemical reaction inhibition pathways. Reaction pathway analysis based on C, I and F atom fluxes is used to explain these phenomena. The second application gives an explanation as to the apparent reverse suppressing effect of the CBrF₃ in inhibiting the methanol-fuelled flames compared to CF₃I. The major reactions responsible for this suppressing phenomenon are presented, and an explanation for the high suppression capability of CF₃I over CBrF₃ for methanol flame is presented. The third application investigates the evolution of toxic gases, such as CO, HBr, HF and HI in hot layers formed in enclosed fires mitigated with CBrF₃ and CF₃I. Both equilibrium and time-evolving concentrations of toxic gases were estimated. The effect of the global equivalence ratio, temperature of the hot layer, agent concentration on the toxic gases is studied by comparing the species evolution histories.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Date
- 2010
- Keyword(s)
-
inhibition mechanism;
chemical kinetics;
inhibition cycle;
hydrocarbon fuelled premixed flames;
reaction pathway analysis;
flame structure;
burning velocity
- Resource Type
- thesis
- Rights
- Copyright 2010 Caimao Luo
- Identifier
- http://hdl.handle.net/1959.13/805503
- Language
- eng
-
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