US3319877A - Machines of the cross-flow type for inducing movement of fluid - Google Patents

Description

May 16, 1967 a. ECK ETAL 3319,87?

MACHINES OF THE CROSS-FLOW TYPE FOR INDUCLNG MOVEMENT OF FLUID Original Filed Sept. 5, 1962 2 Sheets-Sheet 1 INVENTORS BRUNO ECK ATTORNEYS May 16, 1967 B. ECK ETAL 3,319,877

MACHINES OF THE CROSS-FLOW TYPE FOR INDUCING MOVEMENT OF FLUID Original Filed Sept. 5, 1962 v 2 Sheets-Sheet 2 INVENTORS BRUONOA ECK A 6 BY NIK L US L jw I W 7" 3 ATTORNEYS= United States Patent ()fiice 3,319,877 Patented May 16, 1967 3,319,877 MACHINES OF THE CROSS-FLOW TYPE FOR INDUCING MUVEMENT F FLUID Bruno Eek, Cologne-Klettenberg, and Nikolaus Laing, Stuttgart, Germany, assignors, by mesne assignments, to Laing Vortex, Inc., New York, N.Y.

Continuation of application Ser. No. 453,352, May 5, 1965, which is a continuation of application Ser. No. 221,621), Sept. 5, 1962. This application Sept. 1, 1966, Ser. No. 589,147

Claims priority, application Germany, Dec. 7, 1956, L 26,388, E 13,333, E 13,334 5 Claims. (Cl. 230-125) This invention relates to cross-flow fluid machines for inducing movement of fluids which is to be understood as including both liquids and gases, and this application is a continuation of copending application 453,352, filed May 5, 1965, itself a continuation of application 221,620 filed Sept. 5, 1962, which in turn was a continuation-inpart of application Ser. No. 671,114, filed July 5, 1957 and now abandoned. The invention relates more particularly to cross-flow machines, i.e. machines or" the type comprising a hollow cylindrical bladed rotor mounted for rotation about its axis and through which, in operation of the machine, fluid passes at least twice through the path of the rotating blades in a direction transverse to the axis of the rotor.

The invention concerns more especially fluid flow machines for operation under conditions of low Reynolds numbers. The Reynolds number of a particular fluid flow condition is a dimensionless number representing the ratio of the product of flow velocity and a characteristic linear dimension of the part under observation to the kinematic viscosity of the fluid. For the purpose of the present application Reynolds number (Re) will be defined as where d is the blade depth radially of the rotor, c is the peripheral speed of the rotor, and 'y is the kinematic viscosity of the fluid, the latter being equal to the quotient of the dynamic viscosity and density. A Reynolds number is considered hereto to be low if, as above defined, it is less than 5 X The invention has particular (though not exclusive) application to small domestic cross-flow fans. Such a fan having for example a rotor diameter of 60 mm. and being rotated at 1500 r.p.m. will operate at a Reynolds number of approximately Re=2,000. In general for a particular Imotor-and-fan combination the Reynolds number will be ascertainable within reasonable limits from a knowledge of the fan dimensions and the motor characteristics.

From the definition just given, it will be understood that the invention concerns more especially flow machines which are small dimensionally, run at low peripheral speeds, and are intended for use with air or other gas having a low density, or used with a fluid having a high viscosity.

It is known that in a flow machine having bladed rotors, an initial acceleration and a subsequent deceleration of the flow occurs in boundary layers on the suction side of each blade as fluid passes over the blade. The higher the viscosity of the fluid in relation to this density or in relation to the relative viscosity between the blade and fluid (i.e. the lower the Reynolds number) the greater is the deceleration of the boundary layer in the deceleration zone of the blade. If the boundary layer is slowed down sufliciently, it separates from the blade and no longer follows the blade contour. The point at which separation occurs is known as the separation point. The separation point travels forward along the surface of the blade against the direction of flow in proportion to the increase in the effect of the viscosity relative to density or to the decrease in the relative velocity between the fluid and the blade.

The movement forward of the separation point along the blade because of low Reynolds number conditions produces a number of undesirable effects in the type of flow machine described. A vorticity zone in which the kinetic energy of the fluid is converted into thermal energy is produced after the separation point with the result that the efiiciency of the machine drops. The degree of deflection of the fluid in passing through the path of the rotating blades decreases owing to the fact that the flow does not follow the full extent of the blade profile. This results in less pressure gain in the machine since pressure gain is determined by the extent of the deflection of the stream tubes in the blade channel. Finally the turbulent flow in back of the separation point effectively reduces a part of the cross-section of the blade channels so that the throughput through the rotor of the machine also diminishes.

For the reasons given, it has previously been considered that the operation of the flow machines under conditions of low Reynolds numbers would necessarily and inescapably involve low efficiencies in comparison with efiiciencies obtainable under conditions of high Reynolds numbers. For example, although the inefficiency of the small blowers above referred to base been notorious, it has been tolerated simply because it has not hitherto been thought capable of improvement.

It has hitherto been thought that to avoid mixing losses a flow machine should always be designed to have a rectangular velocity profile at every section taken across the flow, that is, the graph of velocity of fluid flow at a given point plotted across the flow channel should rise rapidly from zero at one side of the channel to a steady value maintained over the greater part of the section and should then drop again rapidly to zero at the other side. It has also been assumed hitherto that a flow machine of the type described should always have the blades loaded approximately equally by the fluid in the circumferential zones where the fluid passes through the rotor blades. These two related conditions can normally be satisfied without much difliculty.

Following the principles hitherto generally adhered to in the art and enunciated above, one skilled in the art would normally prefer to design a cross-flow blower, such as that shown in Patent No. 2,742,733, so as to work under conditions of high Reynolds numbers and would design the blade angles and ducting on the basis of, and with a view to producing a rectangular velocity profile throughout the blower and an equal loading on the rotor blades in the circumferential zones where the fluid passes these rotor blades. On the other hand, if operation at low Reynolds numbers could not be avoided, the same design principles would normally be applied and the resulting lower efliciency regarded as inevitable.

An object of the present invention is to provide a crossflow machine capable of operating under conditions of low Reynolds numbers with better efficiency than has hitherto been regarded as acceptable.

The invention depends in part on the appreciation that contrary to what has previously been thought by those skilled in the art, it can be advantageous under flow conditions of low Reynolds numbers to bring about in a flow machine a velocity profile having a pronounced maximum with a consequent very unequal loading of the blades in the circumferential zones through which fluid passes. This velocity profile with a pronounced maximum gives rise to some flow tubes within the blower having much a greater velocity than the other flow tubes within the blower.

In the restricted circumferential zones of the rotor blades through which the high velocity flow tubes pass, correspondingly high relative velocities exist locally between the fluid and the blades, so that in these zones momentum is imparted to the fluid at efficiencies which could otherwise be obtained only with machines operating under conditions of correspondingly much higher Reynolds numbers. The velocity profile with a pronounced maximum leads to lower velocities than the mean velocity in other circumferential zones of the rotor blades and in these zones transfer of momentum occurs at an efliciency which is lower than it would have been had the velocity profile been rectangular. However, the available momentum in a flow tube issuing from the blades increases with the square of its velocity; thus the momentum of the fluid as a Whole is substantially concentrated in the high velocity flow tubes so that the transfer efliciencies in the zones of slow throughflow have little effect on the over-all efliciency.

The invention depends in part also on the appreciation that the above-mentioned velocity profile with a pronounced maximum can be obtained by setting up in the machine a cylindrical vortex including a field region with a velocity profile approximately that of a Rankine vortex and a core region eccentric to the rotor axis.

The invention depends in part on the related but further appreciation that for good efliciency and throughput the vortex should have a compact and well-defined core and that flow, particularly that of the fastest stream tubes which (as will be seen) pass adjacent the core region, should flow smoothly into the rotor around the vortex core and out again. We have found that in passing through the rotor the main flow should be turned by 90 at least and preferably nearer 180. This has been found to require that the means chiefly responsible for stabilizing the vortex position, normally a guide surface adjacent which the core is located, must subtend only a relatively small angle at the rotor axis. An angle of 30 will commonly be as great as can be tolerated, and it will be preferred to have the vortex stabilizing means subtend a much smaller angle than this, say less than 20, though to some extent the optimum angle will depend on the design of the vortex stabilizing means: it is even possible to have only a dividing wall between the pressure side and the suction side as seen in the direction of rotation. This contrasts with some prior art arrangements where the underlying concept has been to provide a Wall closely covering an arc of the rotor where the blades return from the pressure to the suction side, to prevent escape of fluid from the pressure to the suction side: from this prior art concept it followed that the larger the arc and the closer the walls the more effective the seal: arcs of 45 and more were common in this type of fan (see Anderson U.S. Patent1,920,952). We have found on the contrary that such a covering wall is, surprisingly, disadvantageous in that it prevents an effective vortex from being set up and stabilized, interferes with flow into and out of the rotor, and gives rise to noise levels higher than experienced with any other fluid flow machine.

The invention also contemplates in part providing wall means to guide fluid leaving the delivery or pressure side of the machine (which wall means, if desired, may serve as part of a diffuser) and positioning the wall an appreciable distance from the outer envelope generated by the blades as the rotor rotates.

In addition to spacing of the guide wall, the invention also contemplates spacing the vortex forming and stabilizing means at an appreciable distance from the rotor.

This concept of appreciable spacing of the guide wall and vortex stabilizing means from the rotor contrasts with the prior art concept that at least one guide wall and sometimes both should be at minimum spacing from the rotor. The spacing recommended according to the invention should considerably exceed a mere working clearance and: should preferably be at least 5% of the rotor diameter in: machines designed for low Reynolds numbers, and may advantageously be of the order of 10% of the rotor diameter. Because of this spacing the machine may be quan-- tity-produced without close manufacturing tolerances, that is to say economically, without danger of the rotor interfering with stationary parts and without the machines grossly varying characteristics. This appreciable spacing; does not result in reduced throughput and efficiency asv might be expected but instead within limits results in in creased efficiency and throughput. It also reduces the noise set up by the machine in operation, which is of course very significant to domestic applications.

Broadly, a cross-flow machine constructed according to the invention is designed for use with low Reynolds numbers and comprises a hollow cylindrically bladed rotor mounted for rotation about its axis with the interior of the rotor defining a substantially unobstructed space and with the blades of the rotor being curved with their outer edges leading their inner edges. End wall means for substantially closing the ends of the rotor may be provided along with vortex forming and stabilizing means extending the length of the rotor and subtending an are at the rotor axis which is less than 30 and preferably less than 20 which means when the machine is operated, will form and stabilize a substantially cylindrical fluid vortex having a core interpenetrating the paths of the rotating blades: and a field region approximating that of a Rankine vortex whereby a major part of the flow passing through the: machine will pass through the path of the rotor blades where they have a component of direction opposite to the main direction of flow within the rotor. Guide wall means are provided whereby the flow of fluid at the pressure side of the rotor may be directed in a desired direction. The vortex forming and stabilizing means and the guide wall means are spaced from the rotor by more than i a mere working clearance, i.e. at least 5% of the rotor diameter and advantageously by a distance equal to about 10% of the rotor diameter. The spacing should be greater than /2 of the blade depth and preferably not more than three times the blade depth.

Further features of the invention may include an approximately arc for fluid entry to the rotor providing the possibility of insertion of the rotor through the inlet into assembled position within the guide means and giving optimum cross-sectional area for flow. The vortex forming and stabilizing means can take various forms. One possible form is that of a rounded nose merging into an outlet wall: another form is a wall portion concentric with the rotor over a small arc (say 10).

Referring to the drawings in which embodiments of the invention are illustrated.

FIGURE 1 is a cross-sectional view of a cross-flow machine constructed according to the invention;

FIGURE 2 is a graph illustrating velocity of fluid flow at the outlet of a cross-flow fluid machine constructed according to the invention;

FIGURE 3 is a graph illustrating velocity of fluid flow at the outlet of conventional cross-flow machines;

FIGURE 4 is a graphy illustrating velocity of fluid flow within the field of a Rankine type fluid vortex;

FIGURE 5 illustrates the ideal fluid flod lines occurring in one half the cross-sectional area of a rotor of a machine of the type shown in FIGURE 1;

FIGURE 6 is a vector diagram illustrating flow of fluid contacting a blade on its second transversal of the path of the rotating blades or when the fluid passes from the interior of the rotor to the pressure side of the machine;

FIGURE 7 is a cross-section of another form of flow machine somewhat similar to that shownin FIGURE 1.

Reference is made to the figures wherein like parts have like identifying numerals and, in particular to FIG- URE 1 which illustrates a flow machine having a cylindrically bladed rotor 1 which is mounted, by means not shown and without the aid of a central shaft, for rotation about its axis in the direction of the arrow 2. The rotor 1 has flat discs 1 at its ends which support blades 3 which in turn extend longitudinally of the rotor. The blades have inner and outer edges 4 and 5 lying on inner and outer blade envelopes 6 and 7 formed when the rotor is rotated. The blades 3 are concave facing the direction of rotation and have their outer axial edges leading their inner axial edges.

A first peripheral guide wall means 8 extends the length of the rotor and merges with a wall 10 to form one side of an exit or outlet duct of the machines. A vortex forming and stabilizing means 9 which comprises a guide body also extends the length of the rotor and as thereon a wall 11 which forms part of the exit or outlet duct and more particularly which forms a diffuser section 19. End walls 20, only one of which is shown, cover the ends of the machine and may, although not necessarily, close the ends of the rotor. The wall 8 and body 9 define an inlet at the entry arc 12 and an outlet an the exit are 13 for flow of fluid to and from the rotor. Thus the wall 8 and the body 9 provide an are for entry of fluid into the rotor which in this embodiment is substantially greater than 180 though this is by no means essential.

The body 9 divides the suction region S from the pressure or discharge region P. That part of the body 9 which is the most effective to form and stabilize a vortex is the wall portion 9a which forms a second peripheral guide wall in opposite relation to the first guide Wall 8. The guide body 9 is so positioned that its location of nearest approach to the rotor 1 is spaced from the rotor by at least one half of the blade depth rather than closely adjacent to the rotor as considered necessary in conventional cross-flow machines where a casing surrounds a portion of a rotor to separate pressure and suction sides of the machine. The wall portion 9a is gently curved convexly to the rotor to form a convex guide surface and extends over an are substantially less than It is seen that the body 9 presents two guide surfaces 9a and 11, which merge in an arc.

The wall 8 terminates at the zone 14 thereof where it lies nearest the rotor: at this zone the wall as spaced from the rotor a minimum of 5% of the rotor diameter and not more than 20% of the rotor diameter.

At all events the spacing of wall portion 9a and guide wall 8 from the rotor, in the case of a small machine Working under low Reynolds numbers conditions, must exceed a mere working clearance and must be at least 5% of the rotor diameter and not more than 10% in the case of wall 9a and more than 20% in the case of wall 8. This appreciable spacing minimizes undesirable noise when the machine is operated, while at the same time, within limits, improving throughput and efiiciency.

The entry are 12 and the exit are 13 both terminate at the zone 14. From the Zone 14, the wall 8 diverges steadiy from the rotor in the direction of rotation indicated by the arrow 2, with increasing radius of curvature: remote from rotor the wall may be straight, as shown at 10. The pressure region P accordingly consists of a channel the median line of which is of spiral formation.

Because both the wall 8 and body 9 separating the outlet and inlet sides of the machine are substantially spaced from the rotor, the machine can be made without adhering to close manufacturing tolerances, while still effectively separating the out et and inlet sides and maintaining the relatively high efl-lciency of the machine. A machine constructed according to the invention particularly lends itself to sheet metal construction.

In operation of the FIGURE 1 machine, a vortex, having a core Whose periphery is designated by the stream line V, and approximating a Ranking type vortex, is produced wherein the core is positioned eccentrically to the rotor axis. Substantially the whole throughput of the machine flows twice through the blade envelope in a direction perpendicular to the rotor axis as indicated by the stream lines F and MF. It is seen further by reference to FIGURE 1 that the vortex core by interpenetrating the blades over the outlet arc serves to reduce the effective area of the outlet so as to form an outlet region bounded on one side by the wall 8 and on the opposite side by the vortex core and that the flow from the machine passes through this region. Also it is seen that the body '9 forms a side of an inlet region for the machine through which flow enters the machine and that a major portion of flow in the inlet region is substantially parallel to and opposite to that in the outlet duct.

FIGURE 4 illustrates an ideal relation of the vortex to the rotor 1 and the distribution of flow velocity in the vortex core and in the held of the vortex. The line 40 represents a part of the inner envelope 6 of the rotor blades 3 projected onto a staight line while the line 41 represents a radius of the rotor taken through the axis of the vortex core. Velocity of fluid at points on the line 41 by reason of the vortex is indicated by the horizontal lines 43a, 43b, 43c and 43d, the length of these lines being the measure of the velocity at the points 43a 43b 430 and 43d The envelope of these lines is shown by the curve 44 which has two portions, portion 44a being approximately a rectangular hyperbola, and the other portion, 44b, being a straight line. Line 44a relates to the field region of the vortex and the curve 44b to the core. It will be understood that the curve shown in FIGURE 4 represents the velocity of fluid where an ideal physical vortex is formed, and that in actual practice, flow conditions will only approximate these curves.

The core of the vortex is a whirling mass of fluid with no translational movement as a whole and the velocity diminishes from the periphery of the core to the axis 42. The core of the vortex intersects the blade envelope as indicated at 40 and an isotach I within the vortex having the same velocity as the inner envelope contacts the envelope. The vortex core is a region of low pressure and the location of the core in a machine constructed according to the invention can be determined by measurement of the pressure distribution within the rotor.

The velocity profile of the fluid where it leaves the rotor and passes through the path of the rotating blades will be that of the vortex. In the ideal case of FIGURE 4, this profile will be that of the Rankine vortex there shown by curves 44a and 44b, and in actual practice, the profile will still be substantially that shown in FIGURE 4 so that there will be around the periphery V of the core shown in FIGURE 1 a stream tube of high velocity whose centre line is the stream line MF and the velocity profile taken at the exit are 13 will be similar to that shown in FIGURE 2 where the line FG represents the exit are 13 and the ordinates represent velocity. The curve shown exhibits a pronounced maximum point C which is much higher than the average velocity represented 'by the dotted line.

It will be appreciated that much the greater amount of fluid flows in the flow tubes in the region of maximum velocity. It has been found that approximately of the performance is concentrated in the portion of the output represented by the line AE which is less than 30% of the total are 13. A conventional velocity profile for fluid flow in a defined passage is illustrated by way of contrast in FIGURE 3 where the average velocity of flow is represented by the dotted line. Those skilled in the art regard this profile as being approximately a rectangular profile which following the principles generally adhered to is the sort of profile heretofore sought in the outlet of a flow machine.

The maximum velocity C shown in FIGURE 2 appertains to the maximum velocity stream tube indicated at MP in FIGURE 1. With a given construction the physical location of the maximum velocity stream tube may be closely defined. The relative velocity between the blades and fluid in the restricted zone of the rotor blades 3 through which the maximum velocity stream tube passes is much higher than it would be if a flow machine were designed following the conditions adhered to heretofore in the art respective the desirability of a rectangular velocity profile at the exit arc and even loading of the blades.

Under low Reynolds number conditions, this unevenness of the velocity profile leads to beneficial results in that there will be less separation and energy loss in the restricted zone, through which pass the maximum velocity stream tube and the stream tubes adjacent thereto than if these stream tubes had the average velocity of throughput taken over the whole exit are 13 of the rotor. There is a more efltcient transfer of momentum to the fluid by the blades in this restricted zone and while the transfer of momentum in the flow tubes travelling below the average velocity will be less eflicient, nevertheless when all of the flow tubes are considered, there is a substantial gain in efficiency.

FIGURE 5 illustrates ideally a number of stream lines F characterizing stream tubes occurring within one half the rotor area defined by the inner envelope 6, it being understood that the stream tubes in the other half of the rotor are similar. The centre line MP of the stream tubes of highest velocity is shown intersecting the envelope 6 at point 50 and the isotach I as being circular when the whole rotor is considered. It is seen that ideally the stream tubes of highest velocity undergoes a change of direction of substantially 180 from the suction to the pressure sides when the flow in the whole rotor is considered. It is also to be noted that the major part of the throughput, contained in these stream tubes, passes through the rotor blades where the blades have a component of velocity in a direction opposite to the main direction of fiow within the rotor indicated by the arrow A.

FIGURE 6 is a diagram showing the relative velocities of flow with respect to a blade at the point 50 referred to in FIGURE 5. In this figure V represents the velocity of the inner edge of the blade 3 at the point 50, V the absolute velocity of the air in the flow tube MF at the point 50, and V the velocity of that air relative to the blade as determined by completing the triangle. The direction of the vector V coincides with that of the blade at its inner edge so that fluid flows by the blade substantially without shock.

The character of a vortex is considered as being determined largely by the blade angles and curvatures. The position of the vortex, n the other hand, is considered as being largely determined by the configuration of the vortex forming means which forms and stabilizes a vortex in co-operation with the bladed rotor. The particular angles and curvatures in any given case depend upon the following parameters-the diameter of the rotor, the depth of a blade in a radial direction, the density and viscosity of the fluid, the disposition of the vortex forming means and the rotational speed of the rotor, as well as the ratio between overall pressure and back pressure. These parameters must be adapted to correspond to the operating conditions in a given situation. Whether or not the angle and shape of the blades have been fixed at optimum values is to be judged by the criterion that the flow tubes close to the vortex core .are to be deflected approximately 180.

It is to be appreciated that the flow lines of FIGURE 1 do not correspond exactly to the position of the vortex core as illustrated in FIGURES 4 and 5 which represent the theoretical or mathematical flow. These latter figures show that it is desirable to have the axis of the core of the vortex within the inner blade envelope 6 so that the isotach within the core is tangent to that envelope. Although this position is achieved in certain constructions hereinafter described, it is not essential, and in fart, is not achieved in the structure shown in FIG- R-E l.-

It is to be further appreciated that despite the divergence of the flow in FIGURE 1 from the ideal, the stream tubes of highest velocity which carry a major part of the throughput are nevertheless turned through an angle of substantially 180 in passing from the suction to the pressure side of the rotor and that these stream tubes pass through the rotor where the blades have a velocity with a component opposite to the main direction of flow through the rotor as indicated by the arrow A.

FIGURE 7 illustrates a machine constructed according to the invention having a vortex forming and stabilizing means of slightly different construction than that shown in FIGURE 1. In the structure shown, the machine has a vortex forming and stabilizing means which has a wall portion 146 defining an arc concentric with the rotor. The means 145 further has a wall porttion 147 which serves as a side wall for the exit duct of the machine. The exit duct has a width substantially the same as the diameter of the rotor. While the particular construction shown is not as eflicient as that shown in FIGURE 1 in that the vortex formed is not stabilized to the same extent as is the vortex in FIGURE 1, nevertheless, the construction shown will form and stabilize a vortex to cause the machine to work within acceptable limits.

While the several forms of machine described are particularly adapted for use under low Reynolds number conditions, their construction may also be used under high Reynolds number conditions; however, they are considered particularly adaptable for low Reynolds number conditions wherein rotor type fluid flow machines have been notoriously inefficient.

We claim:

1. A fluid flow machine of the cross-flow type comprising a rotor having a cylindrical ring of rotor blades of predetermined diameter mounted for rotation about a cylindrical axis and having a substantially unobstructed hollow interior, said blades being of concave shape and having outer axially extending edges leading inner axially extending edges in the direction of rotation of said rotor, and said blades being supported at their ends by substantially flat discs substantially closing the ends of the cylindrical ring; and a casing about said rotor comprising a plurality of walls defining a peripheral inlet and a peripheral outlet spaced from each other about the circumference of the rotor, said walls including a first peripheral guide wall spiraling outwardly away from the periphery of the rotor with the location of nearest approach of said first wall to said rotor being spaced radially outwardly of said rotor within the range of 520% of the preselected diameter of the rotor and with said first wall having an upstream portion defining a side of the inlet and a downstream portion defining a side of the outlet, and a smooth curved guide body forming a second peripheral guide wall in opposite relation to said first peripheral guide wall with said body being defined by a convex surface, said guide body having an upstream portion forming a side of the Peripheral inlet and a downstream portion forming a side of the peripheral outlet with the location of nearest approach of said body to said rotor being spaced radially outwardly of said rotor within the range of 510% of the preselected diameter of the rotor, and said second guide wall extending downstream from said location of nearest approach of said body to said rotor and having a convex guide surface at its upstream end which defines with the periphery of the rotor a means whereby on rotation of said rotor the blades cooperate with the body to establish a rotating vortex of fluid rotating in the direction of the rotor and interpenetrating the blades adjacent said inlet to induce flow through said inlet into the rotating cylindrical ring of blades and thence out through said outlet.

2. A flow machine as claimed in claim 1, wherein the inlet is in the region of 3. A flow machine as claimed in claim 1, wherein the first guide wall diverges continuously from the rotor starting at a point of nearest approach which defines one end of the inlet.

4. A fluid flow machine of the cross-flow type having an outlet duct, an outlet region in said duct, and an inlet region through which the major portion of fluid passes into said machine, said machine comprising a rotor of predetermined diameter having a cylindrical ring of rotor blades mounted for rotation about a cylindrical axis and having an unobstructed hollow interior, said blades being of concave shape and having outer axially extending edges leading inner axially extending edges in the direction of rotation of said rotor and said blades being supported at their ends; and a casing about said rotor comprising a plurality of walls defining with the rotor a peripheral inlet arc and a peripheral outlet are spaced from one another about the circumference of the rotor; said walls including a first peripheral guide wall extending continuously outwardly of the periphery of the rotor with the location of nearest approach of said first wall to said rotor being spaced radially outwardly of said rotor Within the range of 20% of the preselected diameter of the rotor, said first guide wall separating the peripheral inlet are from the peripheral outlet arc in the direction of rotation of the rotor and defining one side of the outlet duct, and a guide body forming a second peripheral guide wall in opposite relation to said first peripheral guide wall with the location of nearest approach of said body to said rotor being spaced radially outwardly of said rotor Within the range of 5-10% of the preselected diameter of the rotor, with said second guide Wall separating the peripheral outlet are from the peripheral inlet arc in the direction of rotation of the rotor, with a portion of said guide body defining a second side of the outlet duct, and with said guide body subtending an angle less than 30 at the rotor axis; said rotor on rotation cooperating with the guide body to establish and stabilize a vortex having a core rotating in the direction of the rotor with the core interpenetrating the blades over a part of said outlet arc and adjacent the body wherein the portion of the outlet arc between said core and said first wall forms said outlet region and wherein the portion of said body adjacent said peripheral inlet are forms a side of said inlet region through which the major portion of the fluid flows whereby said body and vortex core separate the outlet region from the inlet region in the direction of rotation of the rotor and whereby said vortex core induces a flow of fluid through said inlet region, through a portion of the inlet are, into the rotating cylindrical ring of blades and thence out through said outlet region and outlet duct such that the direction of the major portion of flow in said inlet region is substantially opposite and parallel to the flow in said outlet duct.

5. A fluid flow machine according to claim 4 wherein the surface of the guide body at the location of nearest approach to said rotor is curved from said location towards that portion of the guide body forming a side of the outlet duct.

References Cited by the Examiner UNITED STATES PATENTS 1,920,952 8/1933 Anderson 230- 2,942,773 6/1960 Eck 230125 3,035,760 5/1962 Simmons 230-125 3,096,931 7/1963 Eck 230125 3,178,100 4/ 1965 Datwyler 23 0125 FOREIGN PATENTS 559,024 1/1958 Belgium.

DONLEY J. STOCKING, Primary Examiner. H. F. RADUAZO, Assistant Examiner,

Claims (1)

1. A FLUID FLOW MACHINE OF THE CROSS-FLOW TYPE COMPRISING A ROTOR HAVING A CYLINDRICAL RING OF ROTOR BLADES OF PREDETERMINED DIAMETER MOUNTED FOR ROTATION ABOUT A CYLINDRICAL AXIS AND HAVING A SUBSTANTIALLY UNOBSTRUCTED HOLLOW INTERIOR, SAID BLADES BEING OF CONCAVE SHAPE AND HAVING OUTER AXIALLY EXTENDING EDGES LEADING INNER AXIALLY EXTENDING EDGES IN THE DIRECTION OF ROTATION OF SAID ROTOR, AND SAID BLADES BEING SUPPORTED AT THEIR ENDS BY SUBSTANTIALLY FLAT DISCS SUBSTANTIALLY CLOSING THE ENDS OF THE CYLINDRICAL RING; AND A CASING ABOUT SAID ROTOR COMPRISING A PLURALITY OF WALLS DEFINING A PERIPHERAL INLET AND A PERIPHERAL OUTLET SPACED FROM EACH OTHER ABOUT THE CIRCUMFERENCE OF THE ROTOR, SAID WALLS INCLUDING A FIRST PERIPHERAL GUIDE WALL SPIRALING OUTWARDLY AWAY FROM THE PERIPHERY OF THE ROTOR WITH THE LOCATION OF NEAREST APPROACH OF SAID FIRST WALL TO SAID ROTOR BEING SPACED RADIALLY OUTWARDLY OF SAID ROTOR WITHIN THE RANGE OF 5-20% OF THE PRESELECTED DIAMETER OF THE ROTOR AND WITH SAID FIRST WALL HAVING AN "UPSTREAM PORTION DEFINING A SIDE OF THE INLET AND A DOWNSTREAM PORTION DEFINING A SIDE OF THE OUTLET, AND A SMOOTH CURVED GUIDE BODY FORMING A SECOND PERIPHERAL GUIDE WALL IN OPPOSITE RELATION TO SAID FIRST PERIPHERAL GUIDE WALL WITH SAID BODY BEING DEFINED BY A CONVEX SURFACE, SAID GUIDE BODY HAVING AN UPSTREAM PORTION FORMING A SIDE OF THE PERIPHERAL INLET AND A DOWNSTREAM PORTION FORMING A SIDE OF THE PERIPHERAL OUTLET WITH THE LOCATION OF NEAREST APPROACH OF SAID BODY TO SAID ROTOR BEING SPACED RADIALLY OUTWARDLY OF SAID ROTOR WITHIN THE RANGE OF 5-10% OF THE PRESELECTED DIAMETER OF THE ROTOR, AND SAID SECOND GUIDE WALL EXTENDING DOWNSTREAM FROM SAID LOCATION OF NEAREST APPROACH OF SAID BODY TO SAID ROTOR AND HAVING A CONVEX GUIDE SURFACE AT ITS UPSTREAM END WHICH DEFINES WITH THE PERIPHERY OF THE ROTOR A MEANS WHEREBY ON ROTATION OF SAID ROTOR THE BLADES COOPERATE WITH THE BODY TO ESTABLISH A ROTATING VORTEX OF FLUID ROTATING IN THE DIRECTION OF THE ROTOR AND INTERPENETRATING THE BLADES ADJACENT SAID INLET TO INDUCE FLOW THROUGH SAID INLET INTO THE ROTATING CYLINDRICAL RING OF BLADES AND THENCE OUT THROUGH SAID OUTLET.

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