Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(SCCI). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


University of New South Wales

1. Behzadi, James. Conditional moment closure for SCCI combustion.

Degree: Mechanical & Manufacturing Engineering, 2017, University of New South Wales

Homogeneous charge compression ignition (HCCI) and stratified charge compression ignition (SCCI) engines potentiallyoffer high fuel economy and low emissions. Practical problems need to be overcome, however, and several of them areaffected by or may be alleviated/controlled by stratification of the charge, whether deliberate mixture-stratification by directinjection, or thermal stratification resulting from wall-heat transfer. This thesis therefore seeks to develop and evaluate acomputational model of the combustion process in HCCI and SCCI engines that is capable of simulating the effects of chargestratification. The basis of the modelling is an approach known as conditional moment closure (CMC), originally developedfor nonpremixed jet flames, which reduces errors associated with closure of chemical source terms by conditioning themon a variable upon which they principally depend. This thesis builds on previous work to adapt CMC to HCCI and SCCIengines which considered thermally stratified ignitions in an environment free of walls. In two important steps towards acomplete CMC model of an SCCI engine, the present thesis considers first mixture-stratified ignition and second thermallystratified ignitions in the presence of walls. In the former case the baseline CMC model considers mixture fraction as theconditioning variable, while in the latter it considers total enthalpy. Extensions of these models by considering second orderclosure, double conditioning, and conditioning on reacting scalars are also considered.Two sets of two-dimensional direct numerical simulation (DNS) are employed to evaluate performance of the CMCmodels. The first DNS data-set simulate ignitions in SCCI-like thermochemical conditions with compositionally stratifiedn-heptane / air mixtures in a constant volume representing the bulk gas at top dead centre (TDC) of an SCCI engine.The second DNS data-set considers the effect of wall heat transfer on auto-ignition of thermally stratified hydrogen/airmixtures in a two-dimensional channel representing the TDC of an HCCI engine. The first DNS data-set is parametrised byfluctuations in mixture composition and temperature, whereas the second set is parametrised by temperature fluctuations.Using the first DNS data-set, and the mixture-fraction CMC model, a posteriori tests of the model, which is implementedin an open-source computational fluid dynamics (CFD) package known as OpenFOAMR , reveals an excellent agreementbetween the CFD-CMC solver and the DNS data-set for the cases with low levels of stratification, whereas deviations fromthe DNS are observed in cases which exhibit high level of stratifications. A subsequent a priori analysis reveals that thereason for disagreement is failure of the first-order closure due to the high level of conditional fluctuations. A second-orderclosure is also shown to fail to improve the results and it is only double conditioning that provides a satisfactory closure forthe reaction rates.Using the second DNS data-set modelling ignition in a channel with wall heat… Advisors/Committee Members: Hawkes, Evatt, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW, Bolla, Michele, Aerothermochemistry and Combustion Systems Laboratory, ETH Zurich, Talei, Mohsen, Department of Mechanical Engineering, University of Melbourne, Kook, Shawn, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW.

Subjects/Keywords: DNS; CMC; openFOAM; SCCI; HCCI

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Behzadi, J. (2017). Conditional moment closure for SCCI combustion. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/57440 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43407/SOURCE02?view=true

Chicago Manual of Style (16th Edition):

Behzadi, James. “Conditional moment closure for SCCI combustion.” 2017. Doctoral Dissertation, University of New South Wales. Accessed April 13, 2021. http://handle.unsw.edu.au/1959.4/57440 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43407/SOURCE02?view=true.

MLA Handbook (7th Edition):

Behzadi, James. “Conditional moment closure for SCCI combustion.” 2017. Web. 13 Apr 2021.

Vancouver:

Behzadi J. Conditional moment closure for SCCI combustion. [Internet] [Doctoral dissertation]. University of New South Wales; 2017. [cited 2021 Apr 13]. Available from: http://handle.unsw.edu.au/1959.4/57440 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43407/SOURCE02?view=true.

Council of Science Editors:

Behzadi J. Conditional moment closure for SCCI combustion. [Doctoral Dissertation]. University of New South Wales; 2017. Available from: http://handle.unsw.edu.au/1959.4/57440 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43407/SOURCE02?view=true


University of New South Wales

2. Zhang, Haoyang. Modelling of stratified charge compression ignition engines.

Degree: Photovoltaics & Renewable Energy Engineering, 2014, University of New South Wales

Homogeneous charge compression-ignition (HCCI) engines have been considered to hold potential for next generation internal combustion engines with low emissions and low fuel-consumption. However, some technical hurdles, such as low combustion-efficiency at low load and excessive pressure-rise rate (PRR) at high load, significantly challenge its practical application.In this thesis, fundamental studies of fuel ignition response to thermal stratification were first conducted by using direct numerical simulations coupled with a detailed chemistry mechanism. For a two-stage ignition fuel with negative temperature coefficient (NTC) behaviour, dimethyl ether, the auto-ignition regime was found to depend strongly on the initial temperature. Molecular diffusion was found to be negligible in comparison to chemical reaction when the initial temperature fell inside NTC regime; however, once the initial temperature was outside NTC regime, diffusion became relatively more significant. Diffusion was also observed to decrease with an increase of the length-scale. PRR was found to be reduced with thermal stratification, but this was also dependent on the mean temperature.Then, non-reacting multi-dimensional engine modelling was conducted to investigate the effects of fuel direct injection on the resulting mixture distribution. It was found that as the start of injection was retarded, more fuel was concentrated in the central areas of the cylinder, leading to a potential increase of combustion efficiency and potential reduction of carbon monoxide and unburned hydrocarbons, but a potential increase of excessive nitrogen oxides. Droplet-wall interaction and spray-to-spray interaction were observed to play essential roles in fuel distribution. Furthermore, the use of high injection pressure can enhance the mixing, while the use of high swirl ratio and low injection pressure showed negative effects on the global mixing.Finally, reacting engine simulations were carried on to study the effects of thermal stratification on a fully premixed HCCI engine fuelled by ethanol. These studies pointed out many challenges with attempts to model HCCI predictively, owing to strong sensitivities to initial charge temperature and pressure, wall temperatures, residual gas composition, initial turbulence intensity and models for its evolution and wall models. These sensitivities were analysed and used to construct an optimised model that agreed quite well with experimental pressure traces and associated quantities such as the PRR, the indicated mean effective pressure, and the thermal efficiency. Analysis of the optimised model results was used to determine that enhanced thermal stratification demonstrated a significant reduction of the PRR. The degree of the reduction was found to depend on the penetration of thermal stratification into the bulk-gas regions. In addition, turbulence played an important role in the control combustion phasing primarily by altering the distributions of thermal stratification. Advisors/Committee Members: Hawkes, Evatt, Photovoltaics & Renewable Energy Engineering, Faculty of Engineering, UNSW, Kook, Sanghoon, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW.

Subjects/Keywords: CFD; HCCI; SCCI; Autoignition; Direct injection

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Zhang, H. (2014). Modelling of stratified charge compression ignition engines. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/53630 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:12325/SOURCE02?view=true

Chicago Manual of Style (16th Edition):

Zhang, Haoyang. “Modelling of stratified charge compression ignition engines.” 2014. Doctoral Dissertation, University of New South Wales. Accessed April 13, 2021. http://handle.unsw.edu.au/1959.4/53630 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:12325/SOURCE02?view=true.

MLA Handbook (7th Edition):

Zhang, Haoyang. “Modelling of stratified charge compression ignition engines.” 2014. Web. 13 Apr 2021.

Vancouver:

Zhang H. Modelling of stratified charge compression ignition engines. [Internet] [Doctoral dissertation]. University of New South Wales; 2014. [cited 2021 Apr 13]. Available from: http://handle.unsw.edu.au/1959.4/53630 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:12325/SOURCE02?view=true.

Council of Science Editors:

Zhang H. Modelling of stratified charge compression ignition engines. [Doctoral Dissertation]. University of New South Wales; 2014. Available from: http://handle.unsw.edu.au/1959.4/53630 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:12325/SOURCE02?view=true

3. Böhmler, Judith. Well-controlled and well-described SAMs-based platforms for the study of material-bacteria interactions occuring at the molecular scale : Des plateformes monocouches moléculaires auto-assemblées, contrôlées et décrites de façon approfondie, pour l'étude des interactions matériau-bactérie à l'échelle moléculaire.

Degree: Docteur es, Chimie, 2012, Mulhouse

L'adhésion bactérienne est la première étape du processus de formation d'un biofilm et est un enjeu majeur de la recherche depuis plusieurs dizaines d'années. Les biofilms ont des conséquences parfois dramatiques dans des domaines comme la santé, l'agroalimentaire ou la purification des eaux usées. Toutefois, l'adhésion bactérienne reste un phénomène mal compris. Dans cette thèse, l'adhésion bactérienne est étudiée sur des surfaces modèles très bien organisées et structurées, de chimie de surface variable à l'échelle moléculaire. Une méthodologie de caractérisation adaptée aux monocouches déposées sur wafers de silicium est proposée. Des surfaces modèles composées de monocouches mixtes auto-assemblées de densités variables de NH2 dans un continuum de CH, sont développées et optimisées. Ces surfaces contrôlées, de densités de 0% NH2 à 100% NH2 dans CH3, sont utilisées comme outil pour étudier l'adhésion bactérienne en conditions de culture « batch »et « temps réel ». Les résultats montrent un impact significatif sur l'adhésion bactérienne de faibles différences chimiques à l'échelle moléculaire. Les résultats des expériences menées en conditions « batch » permettent de déterminer deux zones « plateau » dans lesquelles l'adhésion bactérienne ne varie pas significativement malgré des variations importantes de la concentration en groupements amine sur la surface. Une zone de transition entre les zones « plateau » est mise en évidence, dans laquelle une faible modification de la concentration en groupement amine mène à l'augmentation / diminution significative du nombre de bactéries adhérées. Cette tendance est montrée pour deux souches différentes de bactérie.

Bacterial adhesion is the first step of biofilm formation and in the focus of research interest since several decades. Biofilms cause many problems, sometimes dramatic, for example in health, food packing or waste water purification. Despite of high interest, bacterial adhesion process is only poorly understood yet. In this work, bacterial adhesion was investigated on well-organized and structured model surfaces with various chemistries at molecular scale. For that purpose a characterization methodology was developed to sufficiently analyze monolayers on silicon wafers, and controlled mixed monolayers surfaces with different densities of NH 2 backfilled with CH3 were developed and optimized. These controlled surfaces with different densities of 0 % NH2 up to 100% NH2 were eventually used as tool to study bacterial adhesion in batch and real time conditions. The results demonstrate a significant impact on bacterial adhesion of weak difference in the surface chemistry at molecular scale. In the batch experiments, two so-called "plateaus" zones were determined, in which bacterial adhesion is not significantly different despite the change of the amine concentration on the surface. On the contrary, one transition zone exists between the "plateaus" in which a slight chunge.in the amine concentration leads to a significant increase / decrease of the bacterial adhesion.…

Advisors/Committee Members: Anselme, Karine (thesis director).

Subjects/Keywords: Plaquette de silicium; Spectres haute résolution XPS; SAM; Monocouches mixtes; E. coli SCCI; S. epidermidis ATCC35984; Adhésion bactérienne; Expériences en temps réel; Silicon wafer; XPS high resolution spectra; SAM; Mixed Monolayers; E. coli SCCI; S. epidermidis ATCC35984; Bacterial adhesion; Real-time experiments

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Böhmler, J. (2012). Well-controlled and well-described SAMs-based platforms for the study of material-bacteria interactions occuring at the molecular scale : Des plateformes monocouches moléculaires auto-assemblées, contrôlées et décrites de façon approfondie, pour l'étude des interactions matériau-bactérie à l'échelle moléculaire. (Doctoral Dissertation). Mulhouse. Retrieved from http://www.theses.fr/2012MULH4073

Chicago Manual of Style (16th Edition):

Böhmler, Judith. “Well-controlled and well-described SAMs-based platforms for the study of material-bacteria interactions occuring at the molecular scale : Des plateformes monocouches moléculaires auto-assemblées, contrôlées et décrites de façon approfondie, pour l'étude des interactions matériau-bactérie à l'échelle moléculaire.” 2012. Doctoral Dissertation, Mulhouse. Accessed April 13, 2021. http://www.theses.fr/2012MULH4073.

MLA Handbook (7th Edition):

Böhmler, Judith. “Well-controlled and well-described SAMs-based platforms for the study of material-bacteria interactions occuring at the molecular scale : Des plateformes monocouches moléculaires auto-assemblées, contrôlées et décrites de façon approfondie, pour l'étude des interactions matériau-bactérie à l'échelle moléculaire.” 2012. Web. 13 Apr 2021.

Vancouver:

Böhmler J. Well-controlled and well-described SAMs-based platforms for the study of material-bacteria interactions occuring at the molecular scale : Des plateformes monocouches moléculaires auto-assemblées, contrôlées et décrites de façon approfondie, pour l'étude des interactions matériau-bactérie à l'échelle moléculaire. [Internet] [Doctoral dissertation]. Mulhouse; 2012. [cited 2021 Apr 13]. Available from: http://www.theses.fr/2012MULH4073.

Council of Science Editors:

Böhmler J. Well-controlled and well-described SAMs-based platforms for the study of material-bacteria interactions occuring at the molecular scale : Des plateformes monocouches moléculaires auto-assemblées, contrôlées et décrites de façon approfondie, pour l'étude des interactions matériau-bactérie à l'échelle moléculaire. [Doctoral Dissertation]. Mulhouse; 2012. Available from: http://www.theses.fr/2012MULH4073

.