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You searched for +publisher:"University of New South Wales" +contributor:("Hawkes, Evatt R., Photovoltaics & Renewable Energy Engineering, Faculty of Engineering, UNSW"). Showing records 1 – 2 of 2 total matches.

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University of New South Wales

1. Salehi, Fatemeh. Conditional moment closure for HCCI with temperature inhomogeneities.

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

With the concerns growing regarding the need to reduce NOx emissions and improve combustion efficiency, HCCI technology has been developed. In spite of its benefits, it presents challenges which are mainly concerned with controlling the auto-ignition timing and limiting the rate of heat release. Numerical simulations have become useful tools to provide a detailed understanding of the combustion process leading to overcome these challenges. This thesis focuses on developing a model based on the first-order CMC approach for modelling the ignition of lean mixtures under HCCI conditions. The premixed CMC equations are derived with the choice of enthalpy as a conditioning variable. The performance of the CMC model is examined for different fuels under various conditions. Three DNS data-sets are employed. The first DNS data-set modelled the ignition of n-heptane/air mixture with mean temperatures in NTC regime whereas the second and third sets of DNS data modelled the ignition of thermally stratified n-heptane/air and iso-octane/air mixtures, respectively, with mean temperatures outside the NTC regime. The CMC results are in excellent agreement with the DNS for the cases with small-to-medium temperature inhomogeneities whereas the CMC under-predicts the ignition delay in the cases with large temperature inhomogeneities. Further investigation using the DNS data shows that the conditional fluctuations are significant in the cases with large thermal stratifications which in turn cause a breakdown of the first-order closure hypothesis. In these cases where a mixed mode of deflagration and spontaneous ignition exists and the dissipation fluctuations generate conditional fluctuations. An assessment of the conditional variance equations, derived for premixed flames, shows correlations between dissipation and conditional fluctuations and correlations between reaction and conditional fluctuations are the dominant sources of conditional fluctuations. The performance of the CFD-CMC solver is also evaluated for modelling the effects of compression heating and expansion cooling. For this purpose, a DNS of a lean thermally stratified ethanol/air mixture is used. The results show the inclusion of compression heating and expansion cooling suppresses the deflagration mode and hence the CMC model predicts the ignition process very well for all cases even for those with large thermal stratification. Advisors/Committee Members: Hawkes, Evatt R., Photovoltaics & Renewable Energy Engineering, Faculty of Engineering, UNSW.

Subjects/Keywords: Thermal stratification; HCCI; Conditional moment closure

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

APA (6th Edition):

Salehi, F. (2014). Conditional moment closure for HCCI with temperature inhomogeneities. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/54425 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:34945/SOURCE02?view=true

Chicago Manual of Style (16th Edition):

Salehi, Fatemeh. “Conditional moment closure for HCCI with temperature inhomogeneities.” 2014. Doctoral Dissertation, University of New South Wales. Accessed April 16, 2021. http://handle.unsw.edu.au/1959.4/54425 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:34945/SOURCE02?view=true.

MLA Handbook (7th Edition):

Salehi, Fatemeh. “Conditional moment closure for HCCI with temperature inhomogeneities.” 2014. Web. 16 Apr 2021.

Vancouver:

Salehi F. Conditional moment closure for HCCI with temperature inhomogeneities. [Internet] [Doctoral dissertation]. University of New South Wales; 2014. [cited 2021 Apr 16]. Available from: http://handle.unsw.edu.au/1959.4/54425 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:34945/SOURCE02?view=true.

Council of Science Editors:

Salehi F. Conditional moment closure for HCCI with temperature inhomogeneities. [Doctoral Dissertation]. University of New South Wales; 2014. Available from: http://handle.unsw.edu.au/1959.4/54425 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:34945/SOURCE02?view=true


University of New South Wales

2. Rusly, Alvin Mulianto. The transiency of in-cylinder flame development in an automotive-size diesel engine.

Degree: Mechanical & Manufacturing Engineering, 2013, University of New South Wales

Global growth in the sales of light-duty diesel-powered vehicles is effectively driven by diesel engine¬ís superior fuel economy though concerns implicating emission formations and usage of non-renewable fossil still persist. Such obstacles present a need for better understanding of the diesel combustion, which will help improve engine efficiency and reduce pollutant emissions. To address this issue, experimental study of in-cylinder combustion processes is conducted in a light-duty diesel engine with focus on flame development transience. A new experimental research facility has been designed and constructed to study transient behaviour of diesel flames during combustion. The facility houses a modified single-cylinder diesel engine that allows optical access to the combustion chamber at realistic engine environment and ambient conditions. Two distinctly different diesel combustion regimes are investigated: one with short injection duration and the other with long injection duration. The first of the combustion regimes consists of short injection duration and long ignition delay ultimately resulting in a positive ignition dwell (fuel injection completes prior to ignition). In this regime, the overall combustion is dominated by premixed burn phase whereby further improvement of efficiency is limited by a drastic increase in in-cylinder pressure. If the problem is severe, undesirable pressure ringing follows the initial pressure rise, which is called diesel knock. The first part of this thesis addresses this issue of knocking in a light-duty diesel engine. In the optical engine, high-speed natural hot soot luminosity imaging was performed to visualise flame behaviour during the knocking cycles. It is found that the diesel flame oscillates against the normal swirl direction and the oscillation frequency matches the frequency of in-cylinder pressure ringing, which is the first observation of such correspondence in a diesel engine. Experimentation with pilot injection showed a remedial effect through elimination of pressure ringing and dampening of flame oscillation. Such results are connected with a short ignition delay and less intense premixed combustion as shown through a lower pressure rise rate and negative ignition dwell (i.e. mixing-controlled combustion).The second regime investigated in this thesis presents long injection duration through a single-hole injector resulting in a negative ignition dwell (combustion starts prior to the end of injection). This regime is dominated by mixing-controlled combustion phase corresponding to high-load engine operating conditions. Opposed to the short-injection regime with positive ignition dwell, this long-injection regime is characterised by a lifted flame that is under the strong influence of jet-wall interaction during and after the fuel injection. Therefore, the focus of last half of this thesis is on the jet-wall interaction and its impact on lift-off length (i.e. distance between the nozzle to the first detectable flame base within a specified spatial range with respect… Advisors/Committee Members: Kook, Sanghoon, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW, Hawkes, Evatt R., Photovoltaics & Renewable Energy Engineering, Faculty of Engineering, UNSW.

Subjects/Keywords: Re-entrainment; Diesel; Knock; Lift-off Length; Optical Engine

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

APA (6th Edition):

Rusly, A. M. (2013). The transiency of in-cylinder flame development in an automotive-size diesel engine. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/52828 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11501/SOURCE01?view=true

Chicago Manual of Style (16th Edition):

Rusly, Alvin Mulianto. “The transiency of in-cylinder flame development in an automotive-size diesel engine.” 2013. Doctoral Dissertation, University of New South Wales. Accessed April 16, 2021. http://handle.unsw.edu.au/1959.4/52828 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11501/SOURCE01?view=true.

MLA Handbook (7th Edition):

Rusly, Alvin Mulianto. “The transiency of in-cylinder flame development in an automotive-size diesel engine.” 2013. Web. 16 Apr 2021.

Vancouver:

Rusly AM. The transiency of in-cylinder flame development in an automotive-size diesel engine. [Internet] [Doctoral dissertation]. University of New South Wales; 2013. [cited 2021 Apr 16]. Available from: http://handle.unsw.edu.au/1959.4/52828 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11501/SOURCE01?view=true.

Council of Science Editors:

Rusly AM. The transiency of in-cylinder flame development in an automotive-size diesel engine. [Doctoral Dissertation]. University of New South Wales; 2013. Available from: http://handle.unsw.edu.au/1959.4/52828 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:11501/SOURCE01?view=true

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