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Title: Systematic reduction of chemical mechanisms via rate-controlled constrained equilibrium
Author: Koniavitis, Panagiotis
ISNI:       0000 0004 7657 9696
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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The development of reduced chemical mechanisms in a systematic way has emerged as a potential solution to the problem of incorporating the increasingly large chemical mechanisms into turbulent combustion CFD codes. In this work, Rate-Controlled Constrained Equilibrium (RCCE) is linked with different systematic methods for identifying the major species in different detailed mechanisms. As a result, a methodology is proposed for developing reduced mechanisms with RCCE via a Computational Singular Perturbation (CSP) analysis of counterflow non-premixed flamelets for different scalar dissipation rates, by integrating over mixture fraction space a modified CSP pointer and weighting the local ordering for each strain rate. RCCE simulations with the derived reduced mechanisms for methane with 16 species and for propane with 27 species are compared with the integration of the detailed mechanisms GRI 1.2 and USC-Mech-II respectively. The last, and most complex, problem under investigation is a detailed mechanism for a realistic surrogate fuel for kerosene, for which two reduced mechanisms are developed via the RCCE-CSP methodology with 17 and 42 species. The applicability of the methodology is demonstrated in non-premixed flames for several strain rates, in non-premixed flames ignited with a pilot to test the dynamic behaviour, in premixed flames for different equivalence ratios and subsequently in perfectly stirred reactors for ignition delay times for varying temperature, pressure and equivalence ratio. An additional combustion regime, studied here, is a laminar non-premixed flamelet, with time-dependent strain rate at high pressure, to test the dynamic behaviour of the reduced mechanisms compared to the full model. Overall very good agreement is obtained, indicating that the methodology can produce reliable mechanisms for different fuels and for a wide range of conditions, combining a remarkable degree of reduction in computational time.
Supervisor: Rigopoulos, Stelios ; Jones, W. P. Sponsor: European Union
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral