TED-AJ03-287 ENTROPY ANALYSIS IN THE INVESTIGATION OF THE MICROSCOPIC DIFFUSION STRUCTURE OF TURBULENT JET FLAMES

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概要

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• Rapid mixing of fuel and air is essential to improve combustion in diffusion flames, and an understanding of the microscopic structure in the diffusion process is important. However, the relationship between the structure of the heterogeneous distribution of fuel clouds and the local turbulence structure is not well understood. Additionally there is no appropriate index for the analysis of degree and scale of the heterogeneity. This paper investigates a method for identifying the homogeneity degree and the scale of clouds : in this paper large scale cluster of fluids, for example fuel vapor (or air), is termed "cloud". The method is based on the entropy concept of statistical dynamics, and it identifies the homogeneity degree of the fuel concentration. Entropy values increase with the progress of uniformity in diffusion processes, and by analyzing entropy values it is possible to identify the scale of the heterogeneity. The entropy analysis is based on the concept of statistical entropy, and it identifies the homogeneity degree in the fuel concentration. The entropy values increase with the progress of uniformity in diffusion process. Figure [figure]A-1 is an example of the entropy values comparing two different states of heterogeneity. The pictures show tracers mixed in fuel jets and they were taken by a laser sheet. The entropy values of the N_2 jet image is higher than the value of the C_2H_4 image, corresponding to the degree of diffusion state. By analyzing the changing speed of entropy values, diffusion intensity of the fuel cloud can be estimated, and it is also possible to identify scales of the heterogeneity. Using the entropy analysis, microscopic structure in turbulent jet and diesel spray was investigated. Figure A-2 is a picture of a turbulent jet simulating diesel splays. In the experiment, water with fluorescent material is injected in the water. The PIV method was used for the analysis of the velocity distribution, and the diffusion intensity was obtained by the analysis of the local entropy. The result shows that the diffusion intensity is the highest at the vicinity of the nozzle exit, and the heterogeneity scale is the smallest. The heterogeneity scale increases gradually along the spray axis towards downstream, with containing smaller scales inside of the large clouds. In the downstream region, small-scale structure diffuses and becomes unclear, while large scale structure remains clearly.[figure]

著者

• KIKUTA Kazushige

  Div. of Mech. Sci., Hokkaido Univ.

• CHIKAHISA Takemi

  Div. of Mech. Sci., Hokkaido Univ.

• HISHINUMA Yukio

  Div. of Mech. Sci., Hokkaido Univ.

• YUYAMA Ryo

  Div. of Mechanical Science, Hokkaido University

• Yuyama Ryo

  Div. Of Mechanical Science Hokkaido University

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