Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Patent
1998-03-16
2000-09-19
Barefoot, Galen L.
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
244207, 244208, 244130, B64C 2108
Patent
active
061199877
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
Field of the Invention
The present invention relates to the field of aerohydrodynamics and heat and mass transfer; in particular it relates to problems of controlling the wall or boundary layers of continuous media gases and/or liquids, which move with regard to heated or isothermal freely streamlined surfaces and surfaces of pressure and/or energy transfer channels, the said surfaces being heated by the said continuous media and especially relates to a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 8.
It is well known that just the boundary or wall layers are one of the main sources of the aerohydrodynamic resistance, when a flow runs past a surface, see f.i. Schlichting G. "Theory of Boundary Layer", Moscow, NAUKA Publishing House, 1974, pp. 712, as well as the factor that determines the thermal resistance in the transfer of heat from the heated surface to the flow core or from the heated flow to the surface, past which the flow runs.
In 1904 L. Prandtl suggested a method, see e.g. Prandtl L., Titiens O."Hydro- and Aerodynamic.IIV. 1,2. M., ONTI, 1935 for controlling the boundary layer by sucking off the moving medium particles, decelerating in the flow wall layer. The essence of this method is well known and it is used for practical purposes in the case of laminar and turbulent flows.
The majority of the results obtained in heat and mass transfer intensification by means of the so-called two-dimensional artificial surface roughness method may be characterized by the possibility of a an increase, by 1.5 to 3 times, of the heat transfer in channels of practically any geometrical shapes. And to achieve such an intensification of the heat transfer it is required that the absolute height of the roughness elements is from 0.02 to 0.03 of the equivalent diameter of the channels in the case when the two-dimensional projections are of a triangular or rectangular shape or if they are made in the form of wire wound around the streamlined surface. The appropriate depth for two-dimensional cross grooves on a cylindrical streamlined surface is from 0.03 to 0.05 of the equivalent hydraulic diameter of the channel. The heat and mass transfer intensification method by means of the two-dimensional artificial surface roughness is effective for the transient and developed turbulent modes of flow of the heat carrier. However, the use of this method involves an essential increase of the hydraulic resistance, which exceeds 4 to 10 times that of a smooth channel. This strong increase of the hydraulic resistance is the main cause, which restrains the use of the two-dimensional artificial surface roughness method for the intensification of the heat transfer in energy transfer devices.
GB 2 263 525 A discloses a flow control arrangement for incorporation in the surface of a body subject to fluid flow comprising an array of magnetohydrodynamic actuators to impose a force on an electrically conductive fluid in a direction parallel to the surface to produce a predetermined boundary layer condition. WO-A-94/00342 is concerned with an apparatus and a method for controlling a boundary layer in a flow of a fluid having a predetermined electrical conductivity and moving relative to a surface, wherein the apparatus comprises a conductivity altering means, a magnetic field generating means and a electric current generating means.
The authors of the EP-A-85 107 484.9. "Heat Transfer Tube for Single Phase Flow", claimed a heat exchange tube which is provided with at least one row of projections (concavities) on the inner surface of the said tube along a spiral curve, while the contour of the cross section of these projections consists of smooth curves in any part of the height of the projections, including the base. In this case the cross section area monotonously decreases in the direction towards the projection apex, whereas the projection height is from 0.45 to 0.6 mm. The spiral curve is selected so that the pitch of the variant (circumferential pitch, azimuthal pitch) along t
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Gachechiladze Ivan Alexandrovich
Kiknadze Gennady Iraklevich
Oleinikov Valery Grigorievich
Barefoot Galen L.
Vida Nikolaus
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