Showing papers on "Airfoil published in 1969"

Evaluation of internal heat-transfer coefficients for impingement-cooled turbine airfoils.

Abstract: Although internal impingement cooling of the leading edge of gas-turbine airfoils has been shown to be effective, previously available heat-transfer data are not generally applicable to present-day turbine designs because of the unique geometry requirements. An experimental system which allows the ready acquisition of heat-transfer data necessary for thermal design of turbine airfoils is described. A cold-flow model is developed, and the measurement of local heat-transfer coefficients on a full-size model is accomplished by considering Joulean dissipation in very thin platinum strips bonded to the model. Heattransfer results are given which show the dependence of Nusselt number on Reynolds number, geometry, and chordwise location on the inside leading-edge region of the airfoil. Dimensionless correlations are presented which allow the designer to predict heat transfer for impingement cooling in these geometries for the range of parameters tested.

Vane assembly and temperature control arrangement

Abstract: A gas turbine engine vane assembly of the type adapted for use in an annular row of such assemblies and having spaced inner and outer platform portions for defining an annular hot gas stream flow path and a hollow airfoil extending therebetween. The airfoil is compartmentalized by a bridge member extending between the airfoil sidewalls and an impingement insert is provided for each compartment. Chordwise extending structural ribs are provided internally of the airfoil to strengthen the sidewalls and impingement baffles are provided outwardly of the platform portions for temperature control of these elements. Passageways are provided through the platforms to direct coolant to the downstream edges thereof and into the hot gas stream at an angle approximating the hot gas swirl angle.

Fluid-cooled airfoil

Abstract: An improved fluid-cooled airfoil having spaced leading and trailing edge chambers and a serpentine passage therebetween. Coolant is delivered to the leading and trailing edge chambers, respectively, by an impingement insert and the portion of the serpentine chamber adjacent the trailing edge chamber. Various features, such as turbulence promoters, inclined trailing edge passages and film-cooling passageways, are provided to enhance the heat-transfer properties of the airfoil.

Unsteady aerodynamic and stall effects on helicopter rotor blade airfoil sections.

Abstract: Oscillatory tests in pitch and in vertical translation were performed on symmetrical and cambered airfoils, at full-scale Reynolds numbers, to provide dynamic stall data for rotor blade analyses. The Mach number range applicable to the retreating side of the rotor disk was covered at frequencies up to the first bending and the first torsional natural frequency. A system with a torsional degree of freedom was also tested. The following key results were found: 1) The negative aerodynamic damping due to stall is highly sensitive to Mach number. 2) Negative aerodynamic damping can be encountered in large-amplitu de plunging motions. 3) The maximum normal force encountered during oscillation is substantially higher than that for static stall. In addition, the flow separation process is discussed.

Vortex generator for airfoil structures

Abstract: A vortex generator for the ends of airfoil structures that directs air on the high-pressure side of the structure into a vortex generator chamber and discharges the swirling air at the trailing edge of the structure. The exit orifice of the vortex generator may be directed at fixed or variable attitudes for causing the vortex created by the generator to either increase or decrease lift provided by the airfoil structure.

Preliminary study of effects of Reynolds number and boundary-layer transition location on shock-induced separation

Abstract: Transonic wind tunnel studies on airfoil to determine effects of Reynolds number and boundary layer transition location on shock induced separated flow

The turbulent wall jet in an arbitrary pressure gradient

Abstract: : A method for calculating the growth of a turbulent wall jet in streaming flow was developed. The flow is assumed to be two-dimensional, incompressible and over a plane, smooth wall. Downstream variations of pressure are permitted and separation in an adverse pressure gradient may be predicted. The method incorporates procedures for matching the flow to that at the blowing slot, although it is postulated that the upstream boundary layer there is thin enough that the wall jet develops without an unmixed wake (i.e. there is not a minimum in the mean-velocity profile). The method incorporates four integral momentum equations taken from the wall to various points in the flow. The calculation of the outer shearing stress, although empirical, is based on the large-eddy equilibrium hypothesis and therefore has some foundation. The remaining empiricism in the method is based on measurements in self-preserving wall jets. The method was used to predict the jet-momentum coefficient required to suppress separation over a trailing-edge flap attached to a thin aerofoil. Plausible curves have been obtained using assumed values of upstream boundary layer at the slot. (Author)

Experimental Aerodynamic Coefficients in the Analytical Study of Suspension Bridge Flutter

Abstract: Certain coefficients are designated, in the analytical formulation of the suspension bridge flutter problem, to provide for the aerodynamic forces of incipient flutter. A method is given for evaluating these coefficients through observation of wind tunnel model vibratory response under steady wind. Use of the method successfully reproduces the classical flutter aerodynamic coefficients of an aerofoil. When flutter coefficients are obtained by it for a model of the original Tacoma Narrows bridge, the method successfully predicts the incipient torsional flutter characteristic of this well-known structure. The paper also discusses the roles of model and prototype damping and the aerodynamic representativeness of section models relative to the full bridge.

Direct Correlation of Fluctuating Lift with Radiated Sound for an Airfoil in Turbulent Flow

Abstract: An airfoil in turbulent flow is thought to radiate sound in consequence of its fluctuating lift The instantaneous sound and lift should be connected by Curle's equation, which describes sound radiation from a rigid surface in contact with turbulent flow It follows that the crosscorrelation of sound and lift should be related in a corresponding way to the lift autocorrelation Such correlations were measured in the present investigation of an airfoil in a jet flow, and the Curle relationship was verified semiquantitatively The predicted comparative shapes of the correlation curves were found; the comparative magnitudes showed a 27% (27‐dB) discrepancy This small discrepancy is attributed to model vibration, which falsely enhanced the lift signal via inertial loading The work answers, in part, questions that have been raised as to the applicability of Curle's equation Further, it confirms that a rigid surface in contact with a turbulent flow need not be inherently passive—a reflector of sound—but can be an active generator of sound

Airfoil with porous leading edge

Abstract: A HOLLOW AIRFOIL FOR USE AS A TURBINE VANE OR BLADE IS MADE UP OF A NUMBER OF SHEET METAL LAYERS BONDED TOGETHER AND FOLDED AT THE LEADING EDGE. HOLES FOR TRANSPIRATION COOLING OF THE BLADE ARE FORMED IN THE LEADING EDGE, THE HOLES IN THE SUCCESSIVE LAYERS BEING DISPOSED IN SPANWISE ROWS WITH THE HOLES IN EACH LAYER PARTIALLY OVERLAPPING THE HOLES IN THE CORRESPONDING ROW IN ADJACENT LAYERS. THESE HOLES IMPROVE THE FOLDING PROPERTIES OF THE LEADING EDGE. SOME OF THEM ARE CONNECTED TO CONDUCT AIR TO THE FORWARD PORTION OF THE POROUS SIDE WALLS OF THE AIRFOIL.

Compressor for handling gases at velocities exceeding a sonic value

Abstract: In the fan portion of a turbofan engine, rotor blades comprise a primary cambered airfoil and an auxiliary airfoil. Where air flow exceeds a sonic velocity relative to the blades, the throat section between adjacent blades positions the normal air shock wave on the auxiliary airfoil. Each auxiliary airfoil forms a nozzle in combination with the pressure surface of its adjacent primary airfoil. This minimizes energy losses normally associated with such normal shock waves riding on the suction surfaces of cambered airfoils in regions of relatively thick boundary layer air. Lateral struts projecting from the primary airfoil, and used to position the auxiliary airfoil, create oblique shock waves which weaken the normal shock wave and minimize energy losses associated with a normal shock wave''s effect of distributing boundary layer air on an airfoil surface. These features are also effective in reducing the generation of noise.

Means and method for preventing the formation of audible frequencies in fluids passing over an airfoil section

Abstract: Means and method for preventing the formation of audible frequencies in fluids passing over an airfoil section in which the potential audible frequencies are converted into inaudible frequencies at the source of the fluid disturbance with the airfoil section.

Variable aerodynamic structure

Abstract: An aerodynamic or airfoil structure for a given span dimension includes a fixed spar or base portion and at least one movable portion comprising a plurality of pivotable rib elements which define a three dimensional aerodynamic structure when extended. The rib elements are hingedly mounted at one end to the fixed portion and at the other to an edge member, so as to form an internally movable parallelogram structure. When the ribs are in the compacted position, they nest against or within the fixed portion, and fold within each other. The aerodynamic or airfoil structure may be in two or more sections that are extendible spanwise through operation of an internal mechanism. Structures of this type may comprise aircraft wings, rotor blades, control surfaces, spoilers, flaps or specialized airfoil devices for atmospheric or reentry vehicles. The airfoils may have either or both trailing and leading edges that are compactible and deployable.

Aircraft having auxiliary airfoils

Abstract: An aircraft has a fuselage from which wings and horizontal stabilizers extend. At low speeds the lifting forces exerted by the airstream passing over the wings create a moment about the center of gravity for the aircraft, and that moment is offset by an opposite or trim force exerted on the horizontal stabilizers. At higher speeds the resultant of the lifting forces on the wings shifts rearwardly and thereby increases the moment about the center of gravity. At such speeds auxiliary airfoils extend from the fuselage to counteract the increased moment so that the trim force on the horizontal stabilizers does not become excessive. The auxiliary airfoils accordingly eliminate excessive static stability and the high drag and structural stresses associated with it.

Lift and control augmenter for airfoils

Abstract: Means is herein provided for augmenting the lift and controllability of an aircraft by blowing compressed air through spanwise slots in a multiple trailing edge flap system on the aircraft''s airfoils. The mechanism consists of a main flap, with rotary and translation motion relative to the associated airfoil; a lower surface flap which is hinged to both the airfoil and the main flap; and an airflow directional control device rotatably mounted to the aft end of the main flap. Downward deflection of the flap mechanism creates a spanwise duct between the main and lower surface flaps, through which compressed air, extracted from a suitable source, is allowed to flow. The air is ejected at high velocity from multiple spanwise slots provided in the flap mechanism. The resultant jet sheets impart a downward momentum to the air passing over the associated airfoil increasing the circulating flow around its chordwise sections and imparting an upward reaction. The airflow directional control device may be utilized both to vary lift symmetrically on the aircraft and to provide roll control by differential action.

Gas turbine airfoil having integral thermocouple

Abstract: A gas turbine airfoil having a thermocouple assembly mounted integrally therewith so as to sense the temperature at the surface of the leading edge of the airfoil without disturbing the gas flow conditions within the engine is disclosed.

Some New Concepts in Oscillatory Lifting Surface Theory

Abstract: New developments on lifting surface theory for oscillatory subsonic flow are given. Key concepts in the analysis are the use of concentrated loads rather than distributed pressure "mode" shapes, and the development of a modified kernel function which gives average values of vertical velocity over chojen intervals and which eliminates all singularity problems. Features of the analysis are: (l) loads are given directly in terms of vertical velocities, (2) no pressure modes have to be assumed, (3) singularities are obviated, (4) the locations of control downwash points are specified systematically, (5) control surfaces may be included, (6) treatment of nonplanar surfaces, such as T-tails, is possible, and (7) application is made through a simple quick routine procedure. Examples are given throughout to illustrate the concepts. This abstract is subject to special export controls, and each transmittal to foreign governments or foreign nationals may be made only with prior approval of the Air Force Flight Dynamics Laboratory (FDTR), Wright-Patterson Air Force Base, Ohio 45433-

Rotary semirigid airfoil

Abstract: A semirigid airfoil for use with rotary wing airborne vehicles. The airfoil includes a rigid spar defining a leading edge, a cable defining the trailing edge and having a root end thereof secured to a root truss and an opposite end thereof secured to a tip truss. Flexible material forms top and bottom airfoil surfaces. Means are provided for controlling the tension in the trailing edge cable during rotation of the airfoil.

Optimization of airfoils for maximum lift

Abstract: The pressure distribution which provides the maximum lift without separation for a monoelement airfoil in an incompressible flow is determined using existing boundary-layer theory and the calculus of variations. The airfoil profiles corresponding to these pressure distributions are determined using second-order airfoil theory. The results indicate maximum lift coefficients as high as 2.8 for Reynolds numbers between five and ten million, and the corresponding drag coefficients are on the order of 0.01. Compressibility has not been considered directly, however the form of the optimum pressure distributions suggests that the critical Mach numbers should be on the order of 0.35.

Lifting body boundary layer control

Abstract: A twin boom lifting body fuselage aircraft has airflow control ports adjacent leading and trailing edges of the airfoil lifting body. Preferred embodiments have interconnected ram air intake means in fuselage booms and air outlets along a trailing edge of a horizontal stabilizer. An engine mounted in a channel section of the horizontal stabilizer produces a low pressure area near the upper trailing portion of the lifting body promoting flow through the air control ports, thereby reducing drag and increasing lift of the aircraft.

Foldable semirigid airfoil for airborne vehicles

Abstract: The present invention relates to a foldable, composite rigid and semirigid airfoil for use with airborne vehicles. The airfoil includes a rigid portion. A hinged rigid spar defines a leading edge of the airfoil. The trailing edge of the airfoil is defined by both a rigid aileron structure forming part of the rigid wing portion, and a cable which interconnects the rigid portion of the airfoil with a root point of attachment on the fuselage of the vehicle. Flexible material forms top and bottom airfoil surfaces of the collapsible wing portion when the airfoil is deployed, said airfoil surfaces being continuous with the aerodynamic form of the rigid wing portion.

Nose slat fuselage lifting body

Abstract: Combined airfoil lifting fuselage and airfoil wing short takeoff and landing aircraft have lift promoting nose slats spaced forward and above a leading edge of the fuselage.

Angle of attack measuring device with adjustable airfoil

Abstract: An angle of attack measuring device is mounted on an aircraft in the airflow-deflection path of an airfoil. The airfoil is operatively secured to the aircraft at a location spaced from the wing. The relative angular position of the airfoil is controllably variable to adapt the operation of the angle of attack measuring system to different flight conditions of the aircraft.