US3156437A - Fluid flow straightening device in a propelled body - Google Patents

Description

P. MERCIER Nov. 10, 1964 FLUID FLOW STRAIGHTENING DEVICE IN A PROPELLED BODY Filed Aug. 21, 1961 United States Patent 3,156,437 FLUID FLOW STRAIGHTENING DEVICE IN A PROPELLED BODY Pierre Mercier, Piscop, Seine-et-Oise, France, assignor t0 S.F.E.R.M.A., Socit Francaise dEntretien et de Rparation de Materiel Aeronantique, Seine, France, a company of France Filed Aug. 21, 1961, Ser. No. 132,800 Claims priority, application France Sept. 2, 1960 1 Claim. (Cl. 244-73) The present invention relates to a flow straightening device for straightening a fluid stream which has been deviated by its passage about a rotating member provided with blades.

The invention relates moreparticularly to a straightening device for correcting the flow of an air stream, or jet, circulating within a faired body moving through the air, said correction being of such a nature as to confer to said faired body the highest aerodynamical fineness ratio possible.

It is a particular object of the present invention to provide an equipment for flying bodies displaceable through air at subsonic or supersonic speeds, and equipped with a turbine or a so-called windmiil for driving a servo-device such as an alternator.

Another object of the invention is to provide a device for stationary or movable apparatus serving to produce a subsonic or supersonic flow of a fluid, said device having for its function to'correct the deviation undergone by said fluid flow when passing through or about a rotating memberlprovided with blades, said rotating member being either a driving member or a driven member.

In a faired body displaced through the air and provided with a hollow passage or canal having a substantially circular or annular section in a plane perpendicular to the axis, or direction, of the displacements of said body, so as to delimit a fluid stream which drives a rotative driven member provided with blades (i.e. a turbine or a windmill), the fluid stream is deviated and rotated at the axis of said driven member. This deviation is highly undesirable, the more so as its amplitude varies with the speed of said fluid stream, the incidence angle of the blades and the resisting torque of said driven member.

Said deviation produces a variable additional drag of the faired body, and may cause, by reaction, said faired body to rotate about its axis.

A fluid flow straightening device constructed according to the principle of the present invention eliminates these disadvantages and furthermore presents additional advantages which will be described in detail hereinafter.

Broadly the principle of the present invention consists in providing in the fluid stream downstream of a rotating member producing a deviation, correcting vanes which are mounted at fixed points with respect to the axis of said rotating member, but adjustable about their respective axes said axes being arranged radially with respect .to said axis of said rotative member.

In one embodiment of the invention driving means such as electric motors, hydraulic or pneumatic cylinders, as well as conventional transmitting members are provided for varying the adjustment'of said correcting vanes in such a way that the fluid stream attacks at zero incidence a reference surface fixedly arranged at a location downstream of said vanes, whereby the device provides for maximum fineness ratio or maximum efficiency.

The correcting or straightening vanes of a device according to the invention are pivotally mounted in a peripheral ring member and/ or on a central hub-like member; simultaneous variation of the angle of incidence of all the vanes is obtained by a control system which may comprise link and lever mechanisms.

3,156,437, Patented Nov. 10, 1964 According to a preferred embodiment of the invention said means for varying the adjustment of the straightening of correcting vanes are controlled by means for measuring the difference between the pressures prevailing at the two active faces of the reference surface, so as to maintain the fluid flow at zero incidence, or at a low incidence, with respect to said reference surface. If said reference surface is so arranged that it contains the axis of the fluid flow the rotational aerodynamic deflection of said flow is compensated.

Said means for measuring the above-mentioned differential pressures may be constituted, for example, by a manometric capsule having probes or inlets arranged at either one of the faces of said reference surface, While the displacement of the diaphragm of said capsule closes or opens electrical contacts which control directly or by means of relays the driving motor or the adjusting cylinder (adjusting jack) for varying the adjustment of said straightening vanes.

It will be understood that it is within the scope of the present invention to provide any other convenient known means for measuring said differential pressures, such as piezoelectrical or similar means.

In a device according to the present invention the rotationally fixed straightening vanes may be provided with internal ducts for circulating a fluid with a view to exchange of heat with the fluid flow guided, or straightened, by said vanes.

Said heat exchange fluid circulated in said ducts is generally constituted by a liquid, and the heat exchange may be effected with a view to increasing the temperature of the air, or with a view to increasing the temperature of said liquid.

The particular combination of straightening vanes and heat exchange means according to the present invention is particularly advantageous in that it allows for efficient heat exchange, due to the comparatively high number of straightening vanes, while said heat exchange process does not cause any additional drag.

Furthermore, if a hot fluid to be cooled is present in a flying body equipped with a device according to the present invention said fluid will heat the airstream circulating about said straightening vanes whereby the volume of air at the exit of the faired body is greater than the volume of air at the entry of said body, which, in turn, results in additional thrust compensating at least partially, or even completely, the drag due to driving the windmill, if the exit speed of the air is higher than the speed at which said air passes about said straightening vanes.

In a device according to the invention the entry and the exit of the fluid circulated within the straightening vanes are obtained by means of a distributing duct and a collector duct communicating, respectively, with the ends of the ducts provided in said vanes, and with the stationary entry and exit circuit for said fluid. Said distributing ducts and collector ducts preferably are provided in the ring member bearing said straightening vanes.

According to the invention the best guiding effect for a fluid stream and the most efficient heat exchange is obtained by providing a great number of straightening vanes, said number being, for example, greater than the number of blades of the rotating member upstream of said straightening vanes, said number of straightening vanes having however no common factor with the number of said blades; in fact if the respective numbers of vanes and blades had such common factor this might result in flutter effects, or impair'the uniformity of the speed at the edges of said flow.

With a View to obtain a higher efliciency of the straightening vanes, as far as guiding of the fluid flow is concerned, it is advantageous to operate said vane within a range of low aerodynamic incidence angles, for which the drag/thrust ratio is favorable and does not cause any turbulence. The incidence angles comprised within this range will be designated hereinafter by the term preferential incidence, and they allow for the highest fineness ratio of an apparatus or faired body considered.

In a device according to the invention automatic means for adjusting the flow of the fluid stream within the faired body are provided in order to permanently maintain the incidence angle of said straightening vanes substantially within said range of preferential incidence.

A flow of the fluid stream may be varied either by varying the exit section of said fluid stream downstream of said straightening vanes, or by partial evacuation of said stream by means of bleeding upstream of the rotating member. In either case conveniently arranged flaps may be actuated by electric, hydraulic, pneumatic, or similar means in response to the deviation of the position of said straightening vanes with respect to the preferential incidence which has been chosen for said vane.

The appended drawings show one embodiment of the present invention, given by way of example only, said embodiment being by no way to be considered as limiting the scope of the present invention.

PEG. 1 is a partial view in section taken in a longitudinal plane of a fluid flow straightening device according to the invention.

FIG. 2 is a sectional longitudinal view taken perpendicularly to the plane of FIG. 1, along line A-A.

FIG. 3 is an end view taken perpendicularly to the axis of displacement of device, along the line BB.

The figures show a device according to the invention mounted on a flying body comprising a central body or hub body 1 having for instance a circular section in the plane perpendicular to the direction of displacement, which direction is indicated by arrow 2; the faired body comprises a duct 3 defining a passage for the fluid stream; in the example shown in FIGS. 1, 2 and 3 said duct has an annular section and is limited by a hub body 1 and by a peripheral portion 4 in the form of a sleeve, which is maintained on said hub body by profiled struts 5 and 6 uniformly spaced around the periphery of said hub body.

An alternator diagrammatically indicated at 7 is arranged within the hub body and is used for instance to supply current to servo-devices of the flying body. Said alternator is driven by a windmill placed in the fluid stream and comprising a plurality of blades 8 the incidence angle of which may be variable. It will be Well understood that a rotary member provided with blades, such as the above-mentioned windmill, might drive any other device or machine comprised in the equipment of the flying body.

At its exit from the windmill the fluid stream is no longer parallel to the axis of displacement, as said airstream has undergone a torsional or helicoidal dieviation.

According to the present invention the windmill provided with blades 8 is associated with straightening vanes 9 arranged downstream of said windmill and stationary with respect to the axis of the latter, while being able to be angularly adjusted about an axis 10 extending substantially spanwise, whereby the aerodynamic incidence of said vanes may be varied. Said straightening vanes have at least cylindrical extension 11 engaging in a peripheral ring member or annular support 12 provided with convenient radial bores.

In the example shown the straightening vanes 9 also are provided with a second extension 13 pivotally mounted in recesses provided in the hub body 1 or in a convenient part integral with said hub body.

Vanes 9 are interconnected by means of a convenient synchronizing mechanism allowing the incidence of said vanes to be adjusted, said mechanism being constituted, for instance, by a finger 14 integral with vanes 9 and cooperating with an adjusting annulus 15 arranged concentrically with respect to the supporting ring member 12 and free to turn about a limited angle with respect to ii said supporting member 12. In order to prevent the adjusting annulus 12 from jamming it may be centered and guided during its coaxial displacements by a system of rolls (not shown) the axes of which are rigidly connected to the vane supporting ring member.

The angular displacements of the adjusting annulus 15 are controlled by mechanical, electric, hydraulic, pneumatic or similar means known per se. The adjusting annulus 15 may be formed with a rack-like portion cooperating with a screw 16 which is rotatably driven by a motor 17 through a transmission mechanism 18 comprising a chain.

The incidence of vanes 9 is controlled in such a manner as to maintain the rotational aerodynamic deflection downstream of said vanes at a value substantially equal, or near, to predetermined or preselected value. It is possible, for instance, to correct the direction of the fluid stream in such a way that said stream reaches with zero incidence the surface of strut 6. If strut 6 is so arranged that its median plane comprises the axis 19 of the faired body complete correction or straightening of the fluid stream is obtained when the incidence of the latter with respect to surface 6 is zero.

According to the invention said surface 6, or reference surface, is provided with means for measuring the differential pressures on each face of said surface. In the embodiment diagrammatically shown in FIG. 2, two orifices 2t} and 21 are provided in the opposite faces of surface 6 and said orifices are connected by convenient ducts 22 and 23 to a manometric capsule 24 the diaphragm 25 of which bears a control rod 26 and causes f electric contacts 27 and 28 to close or to open, while said contacts control in turn, through convenient relays (not shown), the actuation in one direction or the opposite direction (or, if the pressures prevailing, respectively, on both faces of diaphragm 25 have the same value, the immobilisation) of the mechanism for controlling the straighteneing vanes, said mechanism comprising, for example, motor 17.

It will be well understood that any other convenient means for measuring the differential pressures might be utilized, without leaving the scope of the present invention.

In the embodiment hereinabove described the direction of the fluid stream is permanently corrected although the speed and the altitude of the flying body may vary, and in spite of the variation of the incidence of blade 8 of the windmill, and in spite of the variations of the power absorbed by the driven apparatus 7.

in a preferred embodiment of the invention straightening vanes 9 are used in combination with heat exchanging tubes. FIGS. 1 and 2 show two ducts 29 and 30 extending spanwise within each vane 9, and through which a heat exchanging liquid flows in opposite directions, while the air circulates about said vanes.

Ducts 29 and 3d are interconnected in the root 13 of the vanes, and at their opposite ends ducts 29 and communicate with a collecting duct 31 and a distributing duct 32, respectively, said collecting and distributing ducts being provided in the supporting ring member 12. Stationary ducts 31 and 32 are connected through convenient canals to the liquid circuit system. This arrangement results in achieving the communication between ducts 29 and 30 provided in the pivotable members, and the stationary portions of the liquid circuit system. It will be understood that convenient sealing means such as annular joints, O-rings and the like will be provided between the different parts so as to prevent all leakage or loss of liquid between vanes 9 and supporting ring member 12.

In the embodiment shown the device is provided with a variable exit opening for the airstream, downstream of the straightening vanes 9. A flap 33 which may have the form of a sliding sleeve can be actuated by a motor 34 driving a number of screws 35 engaging a part 36 solid with flap 33. It will be understood that any other means for actuating flap 3 3, such as jacks, could be used instead of motor 34 and screws 35, the important fact being that the provision of flap 33 determines the area of the outlet opening for the airstream.

According to the invention the adjustment of said outlet or exit opening is controlled as a function of the incidence of the straightening vanes, i.e. Within the predetermined limits of variation of this adjustment the exit area varies in such a way that the straightening vanes tend to assume a position corresponding to the preferential incidence which allows for the highest efliciency of said vanes.

The movements of motor 34 controlling the area of the exit opening can easily be controlled as a function-of the distance of adjusting annulus 15 (which controls the incidence of vanes 9) with respect to a medium position corresponding to a preferential incidence chosen for the vanes. For instance, a projection provided on annulus 15 may close either of two electric contacts (not shown) placed on either side of said medium position,v as the annulus is pivoted in one direction or in the opposite direction in order to modify the position of the vanes. Said electric contacts control (e.g. through convenient relays) movements of motor 34 in one direction or the other. It will be understood that any other convenient control system, such as a hydraulic system, a pneumatic system etc., might also be used within the scope of the present invention.

In order to prevent coupled vibration effects which might result from the combined control of the position of the straightening vanes and the exit opening area the respective time constants of these control operations are differentiated, and the respective control motions may be 'nitiated with convenient time delays.

In certain cases it may be advantageous to adjust the air flow through duct 3 so as to operate the straightening vanes under preferential incidence conditions, said variation of the air flow being obtained by bleeding air from said fiow upstream of windmill 8, instead of varying the exit opening as described hereinabove. One or several flaps 37, the actuating members (not shown) of which are controlled as a function of the position of the straightening vanes in a manner similar to the control system comprising parts 34, 35 of flaps 33, are arranged to be opened in the direction of arrow 38. It should be understood that both means for adjusting the air flow (i.e. flap 33 and flap 37) could be provided on the same device, as shown in FIG. 1.

It is thought that the invention and many of the attendant advantages Will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

What is claimed is:

In a body to be propelled in a fluid and having a length portion surrounded by a tubular element supported in coaxial and radially spaced relation therewith to define with said portion an annular fluid passage, an alternator in said body, a turbine having a row of radial blades extending in said passage for driving said alternator by the flow of fluid through said passage, the incoming fluid being deflected by said blades in a direction which forms an angle with the incoming fluid and said angle having a mean value determined in function of a given speed of said incoming fluid, at least one structural element in said passage aft of said blades, said element having a radial leading edge, a radial trailing edge parallel to said leading edge and two opposite side walls extending longitudinally between said radial edges, a plurality of circumferentially spaced straightening guide vanes in said passage between said turbine blades and said structural element, each vane mounted for pivotal movement about a radial axis, a mechanism for pivoting said vanes in parallel relationship from a predetermined mean position in either one of two opposite directions, said mean position corresponding to the mean value of said angle of deflection, motor means for operating said mechanism, and fluid pressure sensitive means connected to said opposite side walls of the structural element for controlling said motor means in response to fluid pressure differentials occurring at said opposite side walls upon variations of said angle of deflection from said mean value thereof to thereby adjust the straightening position of said vanes from said mean position thereof in either one of said opposite directions in accordance with said variations of the angle of deflection.

References Cited in the file of this patent UNITED STATES PATENTS 2,647,368 Triebbnigg Aug. 4, 1953 2,806,350 Hoifmann Sept. 17, 1957 2,888,243 Pollock May 26, 1959 2,928,235 Johnson Mar. 15, 1960 2,971,328 McLafferty Feb. 14, 1961 3,054,578 Brocard Sept. 18, 1962 I FOREIGN PATENTS 748,983 Great Britain May 16, 1956

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