Effect of nano-sized aluminum additive on wall heat transfer characteristics of the liquid-fueled scramjet engine

In this paper, effects of three kinds of turning vanes on flow and heat transfer of turbine blade tip-walls with a U-shaped channel have been numerically studied. Numerical simulations are performed to solve three-dimensional, steady, Reynolds-averaged Navier-Stokes equations with the standard k-ω turbulence model. The aspect ratio (AR) and the hydraulic diameter of the channel are 2 and 93.13 mm, respectively. The effects of single-layer, double-layer and double-layer dome-shaped turning vanes in the turn region on the tip-wall heat transfer and overall pressure loss of rectangular U-shaped channels are analyzed. Detailed flow and heat transfer characteristics over the tip-walls, as well as the overall performance, are presented and compared with each other. Results show that the tip-wall heat transfer coefficients with double-layer dome-shaped turning vanes are the highest among the three cases. Double-layer dome-shaped turning vanes can promote the lateral spreading of secondary flow and effectively increase the uniformity of heat transfer on the tip-wall. More importantly, this structure can make the cooling air expand and accelerate at the center region of the top of the U-shaped channel, resulting in more heat to be removed from the tip-wall. Additionally, double-layer dome-shaped turning vanes can effectively reduce the pressure loss of the channel.

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Cluster and Bed-to-wall Heat Transfer Characteristics in a Dual Circulating Fluidized Bed

Industrial & Engineering Chemistry Research ◽

10.1021/ie200649c ◽

2011 ◽

Vol 51 (4) ◽

pp. 2048-2061 ◽

Cited By ~ 10

Author(s):

Myung Won Seo ◽

Young Ho Suh ◽

Sang Done Kim ◽

Sunwon Park ◽

Dong Hyun Lee ◽

...

Keyword(s):

Heat Transfer ◽

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Wall Heat Transfer ◽

Heat Transfer Characteristics ◽

Transfer Characteristics

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On the Mathematical Modeling of Heat Transfer Characteristics of Turbulent Flames in Industrial Furnaces

Energy Conversion ◽

10.1115/imece2002-39296 ◽

2002 ◽

Author(s):

Essam E. Khalil

Keyword(s):

Mathematical Modeling ◽

Heat Transfer ◽

Flow Pattern ◽

Three Dimensional ◽

Flow Regimes ◽

Wall Heat Transfer ◽

Governing Equations ◽

Heat Transfer Characteristics ◽

Combustion Chambers ◽

Transfer Characteristics

The recent advances in numerical methods and the vast development of computers had directed the designers to better development and modifications to air flow pattern and heat transfer in combustion chambers. Extensive efforts are exerted to adequately predict the air velocity and turbulence intensity distributions in the combustor zones and to reduce the emitted pollution and noise abatement to ultimately produce quite and energy efficient combustor systems. The present work fosters mathematical modeling techniques to primarily predict what happens in three-dimensional combustion chambers simulating boiler furnaces, areo engines in terms of flow regimes and interactions. The present work also demonstrates the effect of chamber design and operational parameters on performance, wall heat transfer under various operating parameters. The governing equations of mass, momentum and energy are commonly expressed in a preset form with source terms to represent pressure gradients, turbulence and viscous action. The physical and chemical characteristics of the air and fuel are obtained from tabulated data in the literature. The flow regimes and heat transfer play an important role in the efficiency and utilization of energy. The results are obtained in this work with the aid of the three-dimensional program 3DCOMB; applied to axisymmetrical and three-dimensional complex geometry with and without swirl with liquid or gaseous fuels. The present numerical grid arrangements cover the combustion chamber in the X, R or Y and Z coordinates directions. The numerical residual in the governing equations is typically less than 0.001%. The obtained results include velocity vectors, turbulence intensities and wall heat transfer distributions in combusors. Examples of large industrial furnaces are shown and are in good agreement with available measurements in the open literature. One may conclude that flow patterns, turbulence and heat transfer in combustors are strongly affected by the inlet swirl, inlet momentum ratios, combustor geometry. Both micro and macro mixing levels are influential. The present modeling capabilities can adequately predict the local flow pattern and heat transfer characteristics in Complex combustors. Proper representation of the heat transfer and radiation flux is important in adequate predictions of large furnace performance.

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