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EXPERIMENTAL AND KINETIC MODELING STUDIES OF
FLAMES OF H2, CO, AND C1-C4 HYDROCARBONS
by
Okjoo Park
A Dissertation Present to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements of the Degree
DOCTOR OF PHILOSOPHY
(AEROSPACE ENGINEERING)
DECEMBER 2013
Copyright 2013 Okjoo Park
Object Description
| Title | Experimental and kinetic modeling studies of flames of H₂, CO, and C₁-C₄ hydrocarbons |
| Author | Park, Okjoo |
| Author email | okjoo.park@gmail.com;okjoo.park@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Aerospace Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2013-07-22 |
| Date submitted | 2013-09-30 |
| Date approved | 2013-10-01 |
| Restricted until | 2013-10-01 |
| Date published | 2013-10-01 |
| Advisor (committee chair) | Egolfopoulos, Fokion N. |
| Advisor (committee member) |
Wang, Hai Ronney, Paul D. Shing, Katherine |
| Abstract | Developing reliable chemical kinetic models is a key ingredient in current and future efforts to develop science-based predictive tools, which will be used for the design of more efficient, less polluting, and flexible-fuel combustion systems. While a variety of combustion properties are needed for the comprehensive validation of detailed kinetic models, a minimum requirement for a model’s validity is the prediction of fundamental mixture properties including the laminar flame speed that is a measure of the heat release rate, and thus the driving force of dilatation that leads to power production. ❧ In this study, the combustion characteristics of hydrogen/carbon monoxide/C₁-C₄ hydrocarbons were investigated both experimentally and numerically in laminar premixed and non-premixed flames. These characteristics included laminar flame speeds and extinction limits. Experimentally, flames were established in the counterflow configuration and flow velocity measurements were made using the particle image and laser Doppler velocimetry. Numerically, laminar flame speeds and extinction limits were simulated using quasi-one-dimensional codes, which integrated the conservation equations with detailed descriptions of molecular transport and chemical kinetics. ❧ Although the hierarchical importance of hydrogen chemistry to the modeling of combustion kinetics has long been recognized, there exist notable discrepancies between experimental and computed fundamental combustion properties especially in flames. Hydrogen/air mixtures are flammable for a wide range of equivalence ratios, with reactivity that ranges quite notably from near-limit to near-stoichiometric conditions. Among others, the extent of reactivity is manifested by the laminar flame speed that could vary from several cm/s to few m/s under atmospheric conditions. Additionally, due to the very low molecular weight of hydrogen, its lean mixtures with nitrogen containing oxidizers are thermo-diffusionally unstable due to the sub-unity Lewis numbers. In the present investigation, accurate experimental data were determined for hydrogen/oxygen/nitrogen flames and compared against computed results. The novelty of this investigation is that reference flame speeds that are raw experimental data obtained in positively stretched flames were compared against computed results, which eliminates issues related to cellular flames and linear or non-linear extrapolations. ❧ In addition, uncertainties still exist in modeling of important three-body recombination reactions, such as for example the H-terminating H + Ο₂ + M → HΟ₂ + M. The collision efficiency of the water molecule is known to be large, and as a result its presence at conditions of high density can have a notable effect on various combustion phenomena. The influence of water vapor addition on the extinction of premixed and non-premixed H₂/air flames was investigated experimentally and numerically in low temperature flames. ❧ One of the critical elements towards accurate predictions of combusting flows is to characterize and minimize the uncertainties associated with predictions of fundamental flame properties. In this work, a large set of laminar flame speed data, systematically collected for C₁-C₄ hydrocarbons with well-defined uncertainties, were used to demonstrate how well-characterized laminar flame speed data can be utilized to explore and reduce the remaining uncertainties in a reaction model for small hydrocarbons. The USC Mech II kinetic model was used as a case study. The method of uncertainty minimization using polynomial chaos expansions (MUM-PCE) was employed to constrain the model uncertainty in laminar flame speed prediction. In addition, the types of hydrocarbon fuels with the greatest impact on model uncertainty reduction are identified along with the attendant accuracy that is needed in flame measurements to facilitate better reaction model development. Results demonstrate that a reaction model constrained only by laminar flame speeds of methane/air flames reduces notably the uncertainty in the predictions of the laminar flame speeds of C₃ and C₄ alkanes, because the key chemical pathways of all of these flames are similar to each other. However, the uncertainty in the model predictions for flames of unsaturated C₃-C₄ hydrocarbons remains significant without considering their laminar flames speeds in the constraining target data set, because the secondary rate controlling reaction steps are different from those in methane flames. |
| Keyword | combustion; laminar flame; uncertainty minimization; hydrocarbon; hydrogen; synthesis gas |
| Language | English |
| Format (imt) | application/pdf |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Park, Okjoo |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Filename | etd-ParkOkjoo-2061.pdf |
| Archival file | uscthesesreloadpub_Volume8/etd-ParkOkjoo-2061.pdf |
Description
| Title | Page 1 |
| Full text | EXPERIMENTAL AND KINETIC MODELING STUDIES OF FLAMES OF H2, CO, AND C1-C4 HYDROCARBONS by Okjoo Park A Dissertation Present to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements of the Degree DOCTOR OF PHILOSOPHY (AEROSPACE ENGINEERING) DECEMBER 2013 Copyright 2013 Okjoo Park |
