1,721,226 research outputs found
Investigation of NOx reburning inside a porous burner
No full textNOx Re burning is an attractive approach for the reduction of emission from existing combustion systems. The process involves partial oxidation of the re burning fuel under fuel-rich conditions as well as reaction between hydrocarbon radicals and nitric oxide and subsequent conversion of the intermediate nitrogenous species. This study investigates the re burning characteristics of NOX inside a porous burner. Porous burners are quite effective in stabilising flames at wide range of operating conditions (from very lean to rich) and are classified as low pollutants emitting burners. An experimental porous burner was designed and manufactured for this purpose The burner is instrumented for measuring temperature and pollutant emissions. Porous burner consists of a mixing chamber, heat exchanger and porous bed Premixed air and fuel is fed through the mixing chamber, wherein NOX and other diluents such as nitrogen and carbon dioxide can be added to the mixture. The premixed mixture is ignited at a downstream position and the flame stabilises inside the porous bed very dose to the top of the heat exchanger. The effects of equivalence ratios, flow velocities and input NOX concentration on flame stabilisation, NOX reburning efficiency and temperature profiles along the burner are investigated It was found that up to 92% reburning of NOX is achievable when operating at moderately rich conditions. It was also found that NOX levels in the inlet gas mixture could affect the reburning efficiency. Results also show that the maximum convergence efficiency correlate with input NOX concentration as weH as the flow vdocity and this maximum is almost independent of equivalence ratio
The effect of oxygen concentration on the structure of turbulent nonpremixed flames
Full text linkMILD combustion is a newly implemented and developed concept to achieve high thermal efficiency and fuel saving while maintaining emission of pollutants at very low levels. It utilizes the concept of heat and exhaust gas recirculation to achieve combustion at reduced temperature, with a flat thermal field and low turbulence fluctuations. An experimental burner is used in this study. Temporally, and spatially resolved measurements of reactive scalars are conducted on three different flames of H2/CH4 fuel mixture at fixed jet Reynolds number and different oxygen mass fractions in the hot oxidant stream. The results show substantial variation of the flame structure with the decrease of the oxygen level. The results also point towards a different chemical pathway for the reaction in this combustion regime, where the formation of the OH radical and NO is less dependent on temperature.B.B. Dally, A.N. Karpetis & R.S. Barlo
Flow-induced vibration of an elastically mounted airfoil under the influence of the wake of a circular cylinder
No full textAbstract not availableJ.F. Derakhshandeh, M. Arjomandi, B. Dally, B. Cazzolat
High-power inductive electric propulsion operation with alternative propellants
No full textThis paper presents the results of an experimental campaign to measure thruster-relevant parameters for a high-power (180kW) inductive propulsion system utilising Ar, O₂, N₂, and CO₂ as propellants. Results from the investigation show that inductive thrusters can make use of these propellants without the severe degradation seen in other electric propulsion systems. Furthermore, the collection of experimental data at powers greater than 100kW provides a reference of performance for the high-power electric propulsion devices intended for missions in the near future. Thrust and specific impulse in inductive systems can be improved by preferentially combining the chemical properties of atomic and molecular propellants. The maximum thrust recorded during these experiments was 7.9N, obtained using a combination of argon and oxygen (0.68 Ar + 0.32 O₂). The combination of argon and molecular propellants also decreased thermal losses within the discharge volume. Specific impulse can be doubled for the same input electric power by combining propellants, and future modifications to the thruster geometry and acceleration mechanism can be used to further improve the performance of such systems.A.R. Chadwick, B. Dally, G. Herdrich, M. Ki
Effect of Reynolds number on the spatial distribution of OH and formaldehyde in jet flames in a heated and diluted co-flow
No full textThe spatial distribution of OH, formaldehyde (H2CO) and temperature imaged by laser diagnostic techniques are presented. The measurements are of nonpremixed jet flames in a hot and highly diluted co-flow. These conditions emulate those of Moderate and Intense Low Oxygen Dilution (MILD) combustion. This paper presents some results on the effect of O2 co-flow level and jet Reynolds number on the structure of the flames for various fuels (each diluted by hydrogen 1:1 vol/vol). A reduction of O2 levels is shown to lead to a substantial suppression of OH and a drop in peak temperatures. For strained flames, increased dilution of O2 also leads to reduction of H2CO. Reynolds number effects on the radial profiles of the flame species considered are shown to be minor compared to O2 levels. The drop of the peak temperature in a low O2 co-flow leads to a reduction of thermal gradients and hence a laminarisation of these flames. Strain rate does have a significant effect on the relative levels of H2CO however, with levels increasing markedly with higher Reynolds number.P R Medwell, P A M Kalt, and B B Dallyhttp://www.mecheng.adelaide.edu.au/aspacc05/noframes.htm
Modelling turbulent reacting jets under MILD combustion conditions
No full textA turbulent non-premixed Methane/Hydrogen (1/1 by volume) flames issuing from a jet in hot, low oxygen content coflow, was modelled using transport PDF (TPDF) approach. A comparison between the TPDF results and detailed experimental data of temperature, OH and CO is presented for flames with different oxygen level in the hot coflow (oxygen mass-fraction of 9%, 6%, and 3%). Different kinetics mechanisms were also used. Results from a previous study using the eddy-dissipation concept (EDC) model are also presented. A comparison in performance between the TPDF and EDC models is presented
Effect of fuel dilution on jet flames in a heated and diluted co-flow
No full textimaged by laser diagnostic techniques are presented. The measurements are of nonpremixed jet flames in a hot and highly diluted co-flow. These conditions emulate those of Moderate and Intense Low Oxygen Dilution (MILD) combustion. This paper presents results on the effect of O2 co-flow level and fuel dilution on the structure of the flames for a fixed jet Reynolds number. A reduction of O2 in the oxidant stream is shown to lead to a substantial suppression of both OH and H2CO levels. Within lifted flames, in comparison to the fluctuating levels of OH, H2CO levels remain constant. Although beyond the aim of the current investigation, a peripheral observation has been made that flames in a lower O2 co-flow stabilise at jet velocities which are lifted at higher O2 levels.http://www.mecheng.adelaide.edu.au/aspacc05
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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