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WO2004041638A2 - Dispositif pour etablir et soutenir un flux de couches limites laminaires - Google Patents

Dispositif pour etablir et soutenir un flux de couches limites laminaires Download PDF

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Publication number
WO2004041638A2
WO2004041638A2 PCT/US2003/035003 US0335003W WO2004041638A2 WO 2004041638 A2 WO2004041638 A2 WO 2004041638A2 US 0335003 W US0335003 W US 0335003W WO 2004041638 A2 WO2004041638 A2 WO 2004041638A2
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WIPO (PCT)
Prior art keywords
flow
channel
laminar
ingested
outer skin
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Ceased
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PCT/US2003/035003
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English (en)
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WO2004041638A3 (fr
Inventor
Fabio Paolo Bertolotti
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Individual
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Individual
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Application filed by Individual filed Critical Individual
Priority to AU2003291694A priority Critical patent/AU2003291694A1/en
Publication of WO2004041638A2 publication Critical patent/WO2004041638A2/fr
Publication of WO2004041638A3 publication Critical patent/WO2004041638A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C21/00—Influencing air flow over aircraft surfaces by affecting boundary layer flow
    • B64C21/02—Influencing air flow over aircraft surfaces by affecting boundary layer flow by use of slot, ducts, porous areas or the like
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C3/00—Wings
    • B64C3/38—Adjustment of complete wings or parts thereof
    • B64C3/44—Varying camber
    • B64C3/46—Varying camber by inflatable elements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/10—Drag reduction

Definitions

  • This invention relates to the construction of a structure for the establishment and sustainment of laminar flow over a surface via the ingestion of boundary layer air.
  • the laminar-flow condition in the boundary layer of a fluid flowing over the surface of a body can be difficult to establish once the boundary layer is in a turbulent state. It is further known that establishing and sustaining the laminar-flow condition in the boundary layer can reduce the resulting skin friction between the fluid and the body. This is especially pertinent, for example, in the field of aircraft construction, whereby the improvement of the laminar-flow of the boundary layer and the resulting lower skin friction can achieve potential fuel savings in the operation of the aircraft . For these reasons, means for avoiding or clearing turbulence- causing surface contamination, such as insect collisions with the aircraft surface, as well as means for stabilizing the laminar state of the boundary layer flow over the surface, have been widely studied for many decades. In the context of commercial aircraft, known laminar-flow control devices generally must operate with the best efficiency at only one condition, namely the cruise flight condition, and are thus designed primarily for this operating condition.
  • the boundary-layer flow relevant for the present invention initiates, or is born, at a regular flow-attachment region, also known in the art as a flow stagnation region, such as, but not limited to, the regular flow-attachment region at the leading- edge of the body; at the leading-edge of a member of the body, such as a wing, nacelle, fin, flap, aleron, winglet, or similar appendage; and at the attachment regions occurring in internal flows at points whereat the flow impinges on, and is bifurcated by, a nonporous surface.
  • a regular flow-attachment region also known in the art as a flow stagnation region, such as, but not limited to, the regular flow-attachment region at the leading- edge of the body; at the leading-edge of a member of the body, such as a wing, nacelle, fin, flap, aleron, winglet, or similar appendage; and at the attachment regions occurring in internal flows at points whereat the flow impinges on, and
  • boundary-layer flow initiates at the regular flow- attachment region in a laminar state
  • methods known to those skilled in the art to help maintain the flow in a laminar state.
  • Two of the most widely known methods are the use of an extended region of favorable pressure gradient (i.e. "natural laminar-flow control") and the use of surface suction. Both methods can be combined to form “hybrid laminar-flow control.” Localized surface heating has also been shown to stabilize the boundary-layer flow.
  • boundary-layer flow is tripped into turbulence near the leading-edge, or at any point along the surface of the object, it is very difficult to re-laminarize the flow at a location further downstream.
  • One of the main technological problems with the establishment and maintanence of the laminar state in a selected boundary-layer flow is the surface roughness created by impact of a foreign object on the surface in the leading-edge region of the body. Such roughness can be created, for example, by the impact of insects on the leading-edge of an aircraft's wing, nacelle, and other appendages, during take-off, landing, and low-altitude flight. The roughness on the object's surface creates turbulent flow, preventing the formation of laminar flow downstream.
  • One design, known to those skilled in the art, for solving the impact problem on the leading-edge proposes the use of a perforated surface in the leading-edge region of the body, and the ejection of a cleaning fluid through this perforated surface for a brief duration in time.
  • the fluid dissolves the proteins that constitute the insect's body, and the resulting liquid evaporates into the atmosphere.
  • This design has five main shortcomings: first, the manufacturing of the porous surface and the apparatus for dispensing the fluid is expensive, thus counteracting the fuel savings from laminar flow; second, the apparatus adds weight, and this also counteracts the fuel savings; third, the wetted surface picks-up dust, which becomes hardened to the surface when the liquid evaporates; fourth, the apparatus is complex, leading to higher maintenance costs; fifth, the apparatus necessitates re-filling at regular intervals, leading to higher operating costs.
  • Another proposed design for solving the impact problem uses flaps that extend from underneath the leading-edge to cover the leading-edge during take-off and ascent. This device has been successfully applied to objects with rectilinear leading-edges (in plan view) , such as wings, but its application to nacelles, or other bodies with oval or cylindrical shape, is too complex and costly.
  • Another design for sustaining laminar flow and allowing accessibility to interior machinery in nacelles proposes a single, monolithic, nacelle skin movable along the axis of the nacelle upon rails, or skid pads.
  • the potential savings in fuel consumption are strongly reduced, making the design not desirable .
  • a further problem with current laminar-flow devices is their lack of a means for re-establishing laminar flow once turbulent flow is initiated. This shortcoming limits the extent of the laminar- flow region to areas near the flow-attachment line at the leading-edge .
  • a) is mechanically simple and light-weight; b) can be located at essentially any region of the object's surface;
  • d) can work in conjunction with established methods for sustaining laminar flow
  • f) can re-establish laminar boundary-layer flow in the presence of an upstream boundary-layer flow in the turbulent state.
  • the invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages as apparent from the present description, claims, abstract, and drawings .
  • an outer skin arrangement having an outer surface partitioned into a controlled surface region where laminar flow is expected and an uncontrolled surface region; an elongated surface opening located upstream of the controlled surface region and extending through the outer skin to create a virgin leading-edge in the outer skin, the elongated surface opening ingesting at least the approaching boundary-layer flow and thereby creating a new, virgin flow-attachment region at the virgin leading-edge from which the boundary-layer flows in a laminar state onto the controlled surface region; and a channel for accepting the ingested flow and ejecting the ingested flow at a location on the uncontrolled surface region.
  • the preferred embodiment of the channel comprises a channel diffuser for decelerating the ingested flow and recovering most of the ingested fluid's kinetic energy into pressure, a channel center-section for transporting the ingested flow with minimum skin friction and pressure loss, and a channel nozzle for re- accelerating the ingested flow prior to ejection.
  • the energetic boundary layer can be ejected essentially tangent to the uncontrolled surface region to delay or prevent boundary-layer separation at a location further downstream.
  • the leading-edge of the body or body appendage separates the oncoming flow into a top flow region and a bottom flow region.
  • the embodiments of the invention can be partitioned in two groups: in Group I, the boundary layer is ingested from one of the top or bottom flow regions and ejected into the other flow region; in Group II, the boundary layer is ingested and ejected in the same flow region.
  • the region of outer skin spanning from essentially the elongated surface opening to essentially the channel exit in Group II embodiments can be detached from the body without affecting the ability of the controlled surface region to sustain laminar flow, allowing regular access to the interior of the body.
  • the junctions between the detachable and fixed portion of the body may trip the boundary layer into the turbulent state, but this boundary layer is ingested or ejected, hence does not affect the laminar boundary-layer state on the controlled surface region.
  • Fig. 1 is a schematic sectional view of an aerodynamic body representing a nacelle cowl
  • Fig. 2 is a plot of normalized pressure iso-lines for the aerodynamic body of Fig. 1, moving through air at altitude and speed typical of commercial jet-powered airplanes;
  • Fig. 3 is a schematic sectional view of the leading-edge region of an aerodynamic body according to the invention.
  • Fig. 4 is a schematic sectional view of the leading-edge region near the keel of a nacelle at an angle of attack similar to airplane take-off conditions, according to the invention
  • Fig. 5 is a schematic sectional view of a portion of the outer skin of an aerodynamic according to one embodiment of the invention.
  • Fig. 6 is a schematic sectional view showing further detail near the virgin leading edge for the embodiment shown in Fig. 5;
  • Fig. 7 is a view similar to that of Fig. 6, but showing coupling details between an upstream laminar-flow unit and a downstream laminar-flow unit;
  • Fig. 8 is a schematic sectional view of the leading-edge region of an aerodynamic body according to another embodiment of the invention, showing the flexible membrane fully expanded;
  • Fig. 9 is the same view as Fig. 8, but with the membrane contracted;
  • Fig. 10 is a schematic sectioned perspective view of a portion of the outer skin, according to another embodiment of the invention.
  • Fig. 11 is a schematic perspective view of an engine nacelle incorporating an embodiment of the current invention in a service position allowing access to the space within the nacelle;
  • Fig. 12 is a schematic perspective view of a commercial aircraft incorporating embodiments of the invention at different locations.
  • FIG. 1 schematically shows the basic geometry of a representative aerodynamic body 100 such as a nacelle cowl or the like of an aircraft.
  • the aerodynamic body 100 has an outer skin 11, and a regular flow-attachment region 20 at the leading edge.
  • this aerodynamic body 100, or especially the nacelle cowl 100 is moving through the air, the free-stream airflow impinges onto the regular flow-attachment region 20 and separates into a top flow region 14 and a bottom flow region 16.
  • Each flow region grazes along the aerodynamic body 100, thereby creating a boundary layer airflow over at least part of the outer surface 12 of outer skin 11.
  • Fig. 1 further shows the outer surface 12 of outer skin 11 divided into a controlled surface region 220 adopted to support boundary-layer flow in the laminar state, and an uncontrolled surface region 210, over which the boundary-layer flow may be in a laminar or turbulent state.
  • the regular flow-attachment region 20 is subject to frequent impacts from insects and other particles in the air during takeoff, landing and low-altitude flight.
  • the surface roughness created by the accumulation of these impacts creates sufficient disturbance to trip the boundary-layer flow into a turbulent state.
  • an elongated surface opening 310 is located downstream of the regular flow-attachment region 20 and immediately upstream of the beginning of the controlled surface region 220. The elongated surface opening penetrates through the outer skin to generate a new virgin leading edge 200 on the outer skin.
  • the elongated surface opening 310 is sufficiently large to ingest at least the entire boundary-layer approaching the elongated surface opening 310, thereby creating a new virgin flow-attachment region at the virgin leading edge 200.
  • the virgin leading edge 200 is exposed to non-turbulent flow, enabling the laminar-flow state to exists in the boundary- layer developing over the controlled surface region 220.
  • the ingested air is accepted by a channel 300, and ejected through channel exit 320 at some location in the uncontrolled surface region 210.
  • the preferred embodiment of the channel 300 has a channel diffuser 330 for decelerating the ingested flow and converting most of the kinetic energy of the ingested flow into pressure, a channel center-section 340 for transporting the ingested flow, and a channel nozzle 350 for accelerating the ingested flow prior to flow ejection through the channel exit 320.
  • the channel diffuser is located near the elongated surface opening 310.
  • the channel diffuser is designed to provide as rapid a deceleration as possible without appearance of flow separation along its walls. The procedure for establishing such a design is well known to those skilled in the art. Decelerated flow provides the added beneficial effect of low skin friction between the ingested flow and the walls of the channel 300.
  • channel walls in the center-section 340 are made slightly divergent to create an adverse pressure gradient in the flow direction that is strong enough to maintain the skin friction near zero, but not strong enough to cause flow separation. The ingested flow is, thus, transported through the channel center- section 340 with little loss in pressure, and at a small drag penalty.
  • the ingested flow approaches the channel exit 320 having lost essentially minimal total pressure since the ingestion event. Consequently, the ingested flow can be re-accelerated in the channel nozzle 350 to a velocity approaching the value of the free-stream velocity present over the uncontrolled surface region 210 at the location of the channel exit 320.
  • the ejection of the ingested flow in a direction tangent to the uncontrolled surface region 210 will energize the overall boundary-layer flow downstream of the channel exit 320, thereby endowing the overall boundary-layer to penetrate into a region of stronger adverse pressure gradients and remain attached longer to the outer skin 11 than possible in the absence of flow ejection from the channel exit 320.
  • a region of stronger adverse pressure gradient is created when the controlled surface region 220, having thereupon a favorable pressure gradient for laminar-flow stabilization, is extended towards the trailing edge of the aerodynamic body 100.
  • Group I the boundary layer is ingested from the top flow region 14 and ejected into the bottom flow region 16, or vice versa;
  • Group II the boundary layer is ingested and ejected in the same flow region.
  • a first embodiment of the invention has the virgin leading-edge 200 in the vicinity of the regular flow- attachment region 20 of the nacelle cowl 100.
  • the channel 300 separates the nacelle cowl 100 into a forward nacelle part 114 and a rearward nacelle part 116.
  • the forward nacelle part 114 contains the regular flow-attachment region 20, and is held fixed relative to the rearward nacelle part 116 by azimuthally spaced- apart struts (not shown) spanning the width of the channel 300.
  • the forward nacelle part 114 preferably contains conventional means to heat the surface to prevent ice build-up, such as heating tubes 400. Additionally, the core of the forward nacelle part 114 can be filled with a metal matrix material 410 to add structural strength and aid in the diffusion of heat.
  • the virgin leading-edge 200 is located downstream from the regular flow-attachment region 20 and is separated from the surface of the forward nacelle part 114 by more than the height of the turbulent boundary-layer approaching the virgin leading- edge 200, and preferably by more than 2 times the boundary-layer height (height is defined by the conventional 99% rule, i.e. the point whereat the stream-wise velocity reaches 99% of the free- stream velocity) so as to guarantee that the virgin leading-edge is exposed to a smooth, turbulence-free, undisturbed flow.
  • the flow ensuing from the new stagnation-region on the virgin leading edge 200 is laminar, and is kept laminar over the controlled surface region 220 by conventional means, such as natural laminar-flow control, or such as surface suction applied over part, or all, of the controlled surface region 220.
  • the channel exit 320 In the absence of the channel diffuser 330, channel center- section 340, and channel nozzle 350, the channel exit 320 must be located in a region of lower static pressure than that at the elongated surface opening 310 to establish the desired flow through the channel 300.
  • the elongated surface opening can be located at point labeled "A" and exit at the point labeled "B" . More freedom in the selection of the location of the elongated surface opening and channel exit is obtained with the presence of pressure recovery functionality provided by the channel diffuser 330 and channel nozzle 350, as discussed above.
  • the elongated surface opening 310 can be moved into a region of lower static pressure, the exit can be moved into a region of higher static pressure, or both, and still obtain the desired flow through the channel.
  • a heating means such as the heater- pipe 401, is located near the virgin leading-edge 200 to avoid ice build-up there.
  • An added advantage of heating the virgin leading-edge 200 and near-by outer skin material is the stabilization of the boundary-layer over the controlled surface region 220 that further enhances the boundary-layer flow to remain in the laminar state.
  • Heat to the virgin leading-edge 200 can be produced by cooling engine-bearing oil, for example, or by extracting heat from the engine's exhaust, so as not to subtract power from the engine.
  • An added advantage of this embodiment occurs on the lower part of the nacelle cowl 100 during take-off.
  • This part of the nacelle is known as the keel, and is exposed to a high angle of attack during take-off.
  • the boundary-layer tends to separate from the uncontrolled surface region 13 of the nacelle facing the engine fan as the flow accelerates rapidly away from the regular flow-attachment region 20.
  • boundary-layer separation occurs, the fan blades are subjected to unequal azimuthal loading that can harm the blade's structural integrity, as well as promote the dangerous situation of engine stall.
  • the regular flow-attachment region 20 on the keel-side of the nacelle moves outwardly towards the outer surface of the nacelle due to, in part, the nacelle's angle of attack during take-off and climb.
  • the static pressure at the elongated surface opening 310 is near maximum since the inlet is situated near the regular flow-attachment region, while the channel exit 320 is located within, or near the onset, of the adverse pressure gradient responsible for promoting separation over the uncontrolled surface region 13 of the nacelle facing the engine fan.
  • the combination of the channel diffuser 330, the channel center-section 340 and the channel nozzle 350 works to ingest the flow near the regular flow-attachment region 20 and transport the ingested flow to the channel exit 320 with a minimum loss of total pressure, hence allowing the ingested flow to be ejected from the channel exit 320 with high momentum and, consequently, help the boundary-layer downstream on the channel exit 320 overcome the adverse pressure gradient over the uncontrolled surface region 210 and remain attached this surface.
  • the forward nacelle part 114 is slidably attached to the rearward nacelle part 116 to allow the elongated surface opening 310 to close during the flight portion in which insect impact is likely. By closing the elongated surface opening 310, the virgin leading-edge 200 is further protected against insect contamination.
  • an embodiment of the invention comprises a monolithic laminar-flow unit 150 comprising the outer skin 11 between the elongated surface opening 310 and the channel exit 320 functioning as an upper structural element 221, and a lower structural element 222.
  • the upper structural element 221 contains the virgin leading-edge 200 as well as the controlled surface region 220.
  • the lower structural element 222 mechanically joins with the outer skin 11 and provides a smooth continuation of the outer surface 12.
  • the channel 300 is formed by the space between the upper structural element 221 and the lower structural element 222, and comprises the elongated surface opening 310, the channel diffuser 330, the channel center-section 340, the channel nozzle 350 and the channel exit 320.
  • the upper and lower structural elements are fixedly connected via webbing 260 that is azimuthally spaced- apart, as visible in figures 6 and 7.
  • the webbing 260 extends the length of the channel center-section 340, and extends only partially into the channel diffuser 330 and the channel nozzle 350.
  • the webbing extends the entire length of the monolithic laminar-flow unit 150 so as to seal the channel 300 from the lateral influx of fluid.
  • This construction leads to a structural shell having a beneficial high stiffness and strength due to the high moment of inertia created by the upper structural element 221 and lower structural element 222.
  • the controlled surface region 220 is flat, and subjected to a zero pressure gradient.
  • the height of the channel center- section 340 is 12 times the height of the elongated surface opening 310. If A denotes the surface area of the controlled surface region 220, then the total wetted area of the monolithic laminar-flow unit 150 is approximately three times A, on account of the wetted surface area of the channel 300.
  • the drag produced by the turbulent, slow moving, flow inside the channel 300 is approximately 1.67 Newtons per meter width.
  • This number includes the factor of 2 in wetted area of the channel 300 in comparison with that of the controlled surface region 220.
  • the total drag of the monolithic laminar-flow unit 150 namely 8.3 + 1.67 Newtons per meter width, is only 20 percent higher than that of laminar flow on the controlled surface region 220 per se. In comparison, when the flow over the controlled surface region 220 is turbulent, the drag force is approximately 87 Newtons per meter width.
  • the monolithic laminar-flow unit 150 yields essentially the same low-drag benefits as that of laminar flow over the controlled surface region 220 per se.
  • a more accurate estimate of skin friction based on the solution of the governing differential equations of fluid motion applied to a configuration wherein the controlled surface region 220 extends for 85% of the nacelle chord, yields a total external skin friction reduction of about 50%, with the main difference between the rough estimate and the more accurate estimate being the contribution to skin friction by the diffuser and nozzle sections of the channel 300.
  • the monolithic laminar-flow unit 150 comprises a forward heating tube 402 and a rearward heating tube 403 running parallel to each other and parallel to the virgin leading-edge 200.
  • the forward heating tube 402 and the rearward heating tube 403 run the length of the virgin leading-edge 200 and then connect to each other form a circuit for the heating fluid in which hot fluid flows first through the rearward heating tube and then through the forward heating tube.
  • This arrangement allows the inlet and outlet to the circuit to be conveniently located at one lateral end of the monolithic laminar-flow unit.
  • the monolithic laminar-flow unit 150 can be pulled away from the outer skin 11 to allow access to the machinery below.
  • An embodiment of the invention for removably attaching the monolithic laminar-flow unit 150 to the nacelle is shown in figure 11, where the monolithic laminar-flow unit 150 hinges in a conventional fashion at the crown of the nacelle and has conventional means for fastening the monolithic laminar-flow unit 150 shut at the keel of the nacelle.
  • Flexible tubes 404 connect the forward heating tube 402 and the rearward heating tube 403 to the non-movable part of the nacelle and close the overall heating circuitry.
  • an upstream monolithic laminar-flow unit 152 and a downstream monolithic laminar-flow unit 151 are be joined to each other to provide an extended region of laminar flow.
  • the two units are adopted to provide a continuous passage of channeled air from the upstream monolithic laminar-flow unit 152 to the downstream monolithic laminar-flow unit 151.
  • the upstream monolithic laminar-flow unit 152 has a weakly converging passage 352 replacing the usual channel nozzle and channel exit.
  • the downstream monolithic laminar-flow unit 151 has a receiving channel 360 matching with, and receiving fluid from, the weakly converging passage 352 of the upstream monolithic laminar-flow unit 152.
  • the fluid passing through the receiving channel 360 mixes with the flow from the channel diffuser 330 of the downstream monolithic laminar-flow unit 151.
  • a lobed mixer 362 aids this mixing process.
  • 0-rings 380 In order to avoid a loss in pressure in the flow within the channels of the upstream monolithic laminar-flow unit 152 and the downstream monolithic laminar-flow unit 151 seal against each other in hermetic fashion, using, preferentially, 0-rings 380. More than two monolithic laminar-flow units can be chain connected to create an extended controlled surface region sustaining laminar flow.
  • Chaining multiple monolithic laminar-flow units together provides at least three advantages.
  • First, any undesired tripping of the laminar boundary-layer over one monolithic laminar-flow unit generates turbulent flow only up to the beginning of the following monolithic laminar-flow unit. Thus, the propagation of turbulent flow is blocked, yielding a robust system for laminar-flow control.
  • an inflatable surface patch 450 can be placed upstream of the virgin leading-edge 200 to guarantee zero change of insect impact on the virgin leading- edge.
  • the inflatable surface patch 450 rests upon a perforated surface 460 when not inflated.
  • the perforated surface 460 provides exposure of the inflatable surface patch 450 to a pressurizable channel 470. This channel is pressurized when the inflation of the patch 450 is desired, and is slightly de- pressurized at other times to make the patch 450 press against the perforated surface 460, thereby producing a smooth continuation of the surface neighboring the patch 450.
  • a liquid-spray mechanism is located upstream, and in the vicinity of, the virgin leading-edge 200.
  • the liquid-spray mechanism comprises a supply manifold 480 that feeds and ejects cleaning fluid through flush mounted surface orifices 482 to clean the virgin leading-edge.
  • the cleaning fluid contains additives for dissolving the largely protein makeup of insects .
  • a partial list of the locations that can receive the embodiments of this invention comprises: the nacelle 160, the upper wing surface 162, the lower wing surface (not shown) , the winglets (not shown) , the horizontal stabilizer 164, the vertical stabilizer (fin) 166, and the fuselage 168, especially in regions near a change in surface pressure, such as near the end of the well known fuselage bulge in the Boeing 747.
  • the present inventive structure for influencing or controlling the boundary-layer flow of a fluid along a surface is especially applicable to the outer skin of nacelles, and airfoil members such as the wings, stabilizers, fins and control surfaces of aircraft.
  • the inventive structure is further applicable to any other situation involving a relatively high speed boundary-layer flow of a fluid along a surface, such as fan blades and turbine blades within a jet engine, helicopter rotor blades, ship propellers, ship rudders, blades of wind turbines, as well as surfaces of missiles, torpedoes, and submarines.

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  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Nozzles (AREA)

Abstract

Selon l'invention, l'enveloppe extérieure (11) d'un corps aérodynamique (100) présente un orifice (310) de surface allongée produisant un bord d'attaque vierge (200) dans l'enveloppe extérieure et ingérant la couche limite d'approche s'étendant sur l'enveloppe extérieure, ce qui permet la création une région de fixation d'écoulement sur le bord d'attaque vierge, duquel le flux laminaire peut se développer sur une région de surface contrôlée de l'enveloppe extérieure. L'air ingéré est reçu par un canal (300) comprenant un diffuseur (330) de canal destiné à diminuer le flux ingéré, une section centrale (340) de canal destinée à transporter le flux ingéré, une buse (350) de canal destinée à réaccélérer le flux ingéré, une sortie (320) de canal destinée à éjecter le flux ingéré à un emplacement situé à l'extérieur de la région de surface contrôlée. Des moyens de chauffage (401) situés sur le bord d'attaque vierge effectue des fonctions de dégivrage et augmente la stabilité du flux laminaire sur la région de surface contrôlée. Le corps aérodynamique comprend également l'assemblage de manière structurelle de la matière définissant la partie de l'enveloppe extérieure présentant la région de surface contrôlée et de la matière définissant le canal dans une unité (150) à flux laminaire monolithique qui peut être séparée du reste de l'enveloppe extérieure pour permettre l'accès à l'intérieur du corps aérodynamique.
PCT/US2003/035003 2002-11-04 2003-11-03 Dispositif pour etablir et soutenir un flux de couches limites laminaires Ceased WO2004041638A2 (fr)

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Application Number Priority Date Filing Date Title
AU2003291694A AU2003291694A1 (en) 2002-11-04 2003-11-03 Device for establishing and sustaining laminar boundary-layer flow

Applications Claiming Priority (2)

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US42358702P 2002-11-04 2002-11-04
US60/423,587 2002-11-04

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WO2004041638A2 true WO2004041638A2 (fr) 2004-05-21
WO2004041638A3 WO2004041638A3 (fr) 2004-08-19

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Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2427972A (en) * 1944-02-01 1947-09-23 Frederick C Melchior Self-energizing airfoil
US2841344A (en) * 1955-11-28 1958-07-01 Stroukoff Michael Boundary layer control
US5098037A (en) * 1989-11-06 1992-03-24 The B. F. Goodrich Company Structural airfoil having integral expulsive system

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AU2003291694A8 (en) 2004-06-07
AU2003291694A1 (en) 2004-06-07
WO2004041638A3 (fr) 2004-08-19

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