Wavelets Transform of a Multifractal Measure in a Cool Flame Experiment

Fractals ◽  
1997 ◽  
Vol 05 (01) ◽  
pp. 35-46 ◽  
Author(s):  
M. Nicollet ◽  
A. Lemarchand ◽  
G. M. L. Dumas
Keyword(s):  
Wavelet Transform ◽  
Low Temperature ◽  
Flame Propagation ◽  
Flame Temperature ◽  
Singularity Spectrum ◽  
Cool Flame ◽  
Localization Domain ◽  
Wavelets Transform

In order to characterize the chaotic variations of the cool flame temperature observed during the oxidation of a hydrocarbon at low temperature and under non-homogeneous conditions, we perform multifractal analyses of different measures. In the cool flame localization domain, the singularity spectrum obtained for the visited temperature histogram is comparable to the spectrum deduced from a wavelet transform. In the cool flame propagation domain where the temperature histogram is too narrow to be analyzed, the wavelet transform allows us to prove the multifractal character of the chaos observed. The choice of the parameter value retained to perform the wavelet transform is discussed in detail.

SINGULARITY SPECTRUM OF NONPERIODIC TIME SERIES: SURROGATE DATA AND WAVELET TRANSFORM

Fractals ◽  
2000 ◽  
Vol 08 (02) ◽  
pp. 129-137 ◽  
Author(s):  
M. NICOLLET ◽  
A. LEMARCHAND ◽  
G. M. L. DUMAS
Keyword(s):  
Time Series ◽  
Wavelet Transform ◽  
Flame Temperature ◽  
Deterministic Chaos ◽  
Surrogate Data ◽  
Singularity Spectrum ◽  
Cool Flame

We study the singularities of time series giving the evolution of the cool flame temperature of a hydrocarbon. Several tests using surrogate data and wavelet transform are applied to the original signals. The results suggest that the hypothesis of deterministic chaos cannot be ruled out in the original signals. The multifractal organization of their local singularities is proven.

The role of low temperature fuel chemistry on turbulent flame propagation

2014 ◽  
Vol 161 (2) ◽  
pp. 475-483 ◽  
Author(s):  
Sang Hee Won ◽  
Bret Windom ◽  
Bo Jiang ◽  
Yiguang Ju
Keyword(s):  
Low Temperature ◽  
Flame Propagation ◽  
Turbulent Flame

scholarly journals Role of Low-Temperature Fuel Chemistry on Turbulent Flame Propagation

2019 ◽  
Vol 35 (2) ◽  
pp. 158-166
Author(s):  
Fan ZHANG ◽  
◽  
Zhe REN ◽  
Shenghui ZHONG ◽  
Mingfa YAO ◽  
...  
Keyword(s):  
Low Temperature ◽  
Flame Propagation ◽  
Turbulent Flame

scholarly journals Nitric Oxide Circumstances in Nitrogen-Oxide Seeded Low-Temperature Powling-Burner Flames

2017 ◽  
Vol 3 (3) ◽  
pp. 157
Author(s):  
M. Furutani ◽  
Y. Ohta ◽  
M. Nose
Keyword(s):  
Nitric Oxide ◽  
Low Temperature ◽  
Hydrogen Cyanide ◽  
Chemical Species ◽  
Nitrogen Monoxide ◽  
Cool Flame ◽  
Spectrum Measurement ◽  
Temperature Development ◽  
Flame Region ◽  
Blue Flame

<p>Flat low-temperature two-stage flames were established on a Powling burner using rich diethyl-ether/ air or n-heptane/air mixtures, and nitrogen monoxide NO was added into the fuel-air mixtures with a concentration of 240 ppm. The temperature development and chemical-species histories, especially of NO, nitrogen dioxide NO<sub>2</sub> and hydrogen cyanide HCN were examined associated with an emission-spectrum measurement from the low-temperature flames. Nitrogen monoxide was consumed in the cool-flame region, where NO was converted to the NO<sub>2</sub>. The NO<sub>2</sub> generated, however, fell suddenly in the cool-flame degenerate region, in which the HCN superseded. In the blue-flame region the NO came out again and developed accompanied with remained HCN in the post blue-flame region. The NO seeding into the mixture intensified the blue-flame luminescence probably due to the cyanide increase.</p>

Fractal Dimensional Analysis of Runoff in Jinsha River Basin, China

2013 ◽  
Vol 405-408 ◽  
pp. 2181-2184 ◽  
Author(s):  
Yun Xia Xie ◽  
Shang Chun Zeng ◽  
Wen Sheng Wang
Keyword(s):  
Fractal Dimension ◽  
Wavelet Transform ◽  
Dimensional Analysis ◽  
River Basin ◽  
Hydrological Processes ◽  
Jinsha River ◽  
Runoff Series ◽  
Transform Coefficients ◽  
Wavelets Transform

The hydrological processes are becoming more and more complex. Fractal dimension is one of the important measurements of complexity. This paper utilizes wavelets transform technique to calculate the fractal dimension of runoff for eight stations (Zhimenda, Shigu, Ganzi, Yajiang, Guili, Luning, Xiaodeshi, Pingshan ) in the Jinsha River Basin. The results show: the runoff series in the Jinsha River Basin is fractal; the approach for estimating the fractal dimension by using wavelet transform coefficients is feasible and effective; the fractal dimension of runoff reflect the influence of factors on the runoff.

Investigation of the Roles of Flame Propagation, Turbulent Mixing, and Volumetric Heat Release in Conventional and Low Temperature Diesel Combustion

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Sage L. Kokjohn ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Heat Release ◽  
Oxygen Concentration ◽  
Reaction Zone ◽  
Flame Propagation ◽  
Ignition Delay ◽  
Flame Structure ◽  
Combustion Model ◽  
Combustion Mode ◽  
Flame Structures

In this work, a multimode combustion model that combines a comprehensive kinetics scheme for volumetric heat release and a level-set-based model for turbulent flame propagation is applied over the range of engine combustion regimes from non-premixed to premixed conditions. The model predictions of the ignition processes and flame structures are compared with the measurements from the literature of naturally occurring luminous emission and OH planar laser induced fluorescence. Comparisons are performed over a range of conditions from a conventional diesel operation (i.e., short ignition delay, high oxygen concentration) to a low temperature combustion mode (i.e., long ignition delay, low oxygen concentration). The multimode combustion model shows an excellent prediction of the bulk thermodynamic properties (e.g., rate of heat release), as well as local phenomena (i.e., ignition location, fuel and combustion intermediate species distributions, and flame structure). The results of this study show that, even in the limit of mixing controlled combustion, the flame structure is captured extremely well without considering subgrid scale turbulence-chemistry interactions. The combustion process is dominated by volumetric heat release in a thin zone around the periphery of the jet. The rate of combustion is controlled by the transport of a reactive mixture to the reaction zone, and the dominant mixing processes are well described by the large scale mixing and diffusion. As the ignition delay is increased past the end of injection (i.e., positive ignition dwell), both the simulations and optical engine experiments show that the reaction zone spans the entire jet cross section. In this combustion mode, the combustion rate is no longer limited by the transport to the reaction zone, but rather by the kinetic time scales. Although comparisons of results with and without consideration of flame propagation show very similar flame structures and combustion characteristics, the addition of the flame propagation model reveals details of the edge or triple-flame structure in the region surrounding the diffusion flame at the lift-off location. These details are not captured by the purely kinetics based combustion model, but are well represented by the present multimode model.

Investigation of the Roles of Flame Propagation, Turbulent Mixing, and Volumetric Heat Release in Conventional and Low Temperature Diesel Combustion

2010 ◽  
Author(s):  
Sage L. Kokjohn ◽  
Rolf D. Reitz
Keyword(s):  
Low Temperature ◽  
Heat Release ◽  
Oxygen Concentration ◽  
Reaction Zone ◽  
Flame Propagation ◽  
Ignition Delay ◽  
Flame Structure ◽  
Combustion Model ◽  
Combustion Mode ◽  
Multi Mode

In this work, a multi-mode combustion model, that combines a comprehensive kinetics scheme for volumetric heat release and a level-set-based model for turbulent flame propagation, is applied over the range of engine combustion regimes from non-premixed to premixed conditions. Model predictions of the ignition processes and flame structures are compared to measurements from the literature of naturally occurring luminous emission and OH planar laser induced fluorescence (PLIF). Comparisons are performed over a range of conditions from conventional diesel operation (i.e., short ignition delay, high oxygen concentration) to a low temperature combustion mode (i.e., long ignition delay, low oxygen concentration). The multi-mode combustion model shows excellent prediction of the bulk thermodynamic properties (e.g., rate of heat release), as well as local phenomena (i.e., ignition location, fuel and combustion intermediate species distributions, and flame structure). The results of this study show that even in the limit of mixing controlled combustion, the flame structure is captured extremely well without considering sub-grid scale turbulence-chemistry interactions. The combustion process is dominated by volumetric heat release in a thin zone around the periphery of the jet. The rate of combustion is controlled by transport of reactive mixture to the reaction zone and the dominant mixing processes are well described by the large scale mixing and diffusion. As the ignition delay is increased past the end of injection (i.e., positive ignition dwell), both the simulations and optical diagnostics show that the reaction zone spans the entire jet cross-section. In this combustion mode the combustion rate is no longer limited by transport to the reaction zone, but rather by kinetic timescales. Although comparisons of results with and without consideration of flame propagation show very similar flame structures and combustion characteristics, the addition of the flame propagation model reveals details of the edge or triple-flame structure in the region surrounding the diffusion flame at the lift off location. These details are not captured by the purely kinetics based combustion model, but are well represented by the present multi-mode model.

Feature Set Reduction in Rotation Invariant CBIR Using Dual-Tree Complex Wavelet Transform

2012 ◽  
pp. 232-248
Author(s):  
Deepak Sharma ◽  
Ekta Walia ◽  
H.P. Sinha
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Image Retrieval ◽  
Symmetry Property ◽  
Rotation Invariance ◽  
Image Feature ◽  
Content Based Image Retrieval ◽  
Complex Wavelet Transform ◽  
Complex Wavelets ◽  
Wavelets Transform

An accurate Content Based Image Retrieval (CBIR) system is essential for the correct retrieval of desired images from the underlying database. Rotation invariance is very important for accurate Content Based Image Retrieval (CBIR). In this chapter, rotation invariance in Content Based Image Retrieval (CBIR) system is achieved by extracting Fourier features from images on which Dual Tree Complex Wavelets Transform (DT-CWT) has been applied. Before applying DT-CWT, the Fourier feature set is reduced by exploiting the symmetry property of Fourier transform. For an N x N image, feature set has been reduced from N2/2 features to N2/4 features. This reduction in feature set increases the speed of the system. Hence, this chapter proposes a method which makes the Content Based Image Retrieval (CBIR) system faster without comprising accuracy and rotation invariance.

scholarly journals Development and Parametric Evaluation of a Tabulated Chemistry Tool for the Simulation of n-Heptane Low-Temperature Oxidation and Autoignition Phenomena

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
George Vourliotakis ◽  
Dionysios I. Kolaitis ◽  
Maria A. Founti
Keyword(s):  
Low Temperature ◽  
Residence Time ◽  
Diesel Oil ◽  
Low Temperature Oxidation ◽  
Temperature Oxidation ◽  
Cool Flame ◽  
Fuel Concentration ◽  
Tabulated Chemistry ◽  
The Impact ◽  
Independent Parameters

Accurate modelling of preignition chemical phenomena requires a detailed description of the respective low-temperature oxidative reactions. Motivated by the need to simulate a diesel oil spray evaporation device operating in the “stabilized” cool flame regime, a “tabulated chemistry” tool is formulated and evaluated. The tool is constructed by performing a large number of kinetic simulations, using the perfectly stirred reactor assumption. n-Heptane is used as a surrogate fuel for diesel oil and a detailed n-heptane mechanism is utilized. Three independent parameters (temperature, fuel concentration, and residence time) are used, spanning both the low-temperature oxidation and the autoignition regimes. Simulation results for heat release rates, fuel consumption and stable or intermediate species production are used to assess the impact of the independent parameters on the system’s thermochemical behaviour. Results provide the physical and chemical insight needed to evaluate the performance of the tool when incorporated in a CFD code. Multidimensional thermochemical behaviour “maps” are created, demonstrating that cool flame activity is favoured under fuel-rich conditions and that cool flame temperature boundaries are extended with increasing fuel concentration or residence time.

Sign in / Sign up

Export Citation Format

Share Document