US3322332A

US3322332A - Cross flow machine

Info

Publication number: US3322332A
Application number: US518137A
Authority: US
Inventors: Laing Nikolaus
Original assignee: LAING VORTEX Inc
Current assignee: LAING VORTEX Inc
Priority date: 1962-09-05
Filing date: 1966-01-03
Publication date: 1967-05-30
Anticipated expiration: 1984-05-30

Description

y 1957 N. LAING 3,322,332

CROSS FLOW MACHINE Original Filed Sept. 5, 1962 4 Sheets-Sheet 1 p INVENTOR Nikolaus Lcling ATTORNEYS.

May 30, 1967 N. LAING GROSS FLOW MACHINE 4 Shets-S heet 2 Original Filed Sept. 5, 1962 INVENTOR 1 us Luing ATTORNEYS I N. LAING I CROSS FLOW MACHINE Original Filed Sept. 5 1952 M ay 30, 1967 4 Sheets-Sheet 5 o 0 0 0 0 o o 0 0 00000000 oooooo o 0 C L C C@ 000 00 0 0000 v o o o o o o 0 00 0 0 o o o o o o 3 @O 0 0 0 03 00 0w 0 nili0 0 0 m A l v a F H 1 3 0; 0 a

May 30, 1967 N. LAING 3,322,332

' CROSS FLOWMACHINE Original Filed Sept. 5, 1962 4 Sheets-Sheet &

INVENTO'R NlkOlG Lcnng W ZVQWXP ATTORNEYS United States Patent 3,322,332 CROSS FLOW MACHINE Nikolaus Laing, Stuttgart, Germany, assignor, by mesne assignments, to Laing Vortex, Inc., New York, N.Y. Original application, Sept. 5, 1962, Ser. No. 221,621, now Patent No. 3,232,522, dated Feb. 1, 1966. Divided and this application Jan. 3, 1966, Ser. No. 518,137

Claims priority, application Germany, Dec. 7, 1956, E 13,333, E 13,334 5 Claims. (Cl. 230125) This invention relates to machines for inducing movement of fluid, which is understood as including both liquids and gases; this application is a division of copending application Ser. No. 221,621 filed Sept. 5, 1962, now Patent No. 3,232,522, itself a continuation-in-part of application Ser. No. 671,114 filed July 5, 1957, now abandoned. The invention more particularly concerns flow machines of the cross-flow type, that is, machines comprising a cylindrical bladed rotor mounted for rotation about its axis in a predetermined direction and defining an interior space, and guide means defining with the rotor a suction region and a pressure region, the guide means and rotor co-operating on rotation of the latter in said predetermined direction to induce a flow of fluid from the suction region through the path of the rotating blades of the rotor to said interior space and thence again through the path of said rotating blades to the pressure region. More especially but not exclusively, the invention concerns flow machines of the cross-flow type wherein the guide means and rotor co-operate to set up a vortex of Rankine character having a core region eccentric of the rotor axis and a field region which guides the fluid so that flow through the rotor is strongly curved about the vortex core; such flow machines will herein be designated tangential machines and the characteristics of a pre-' ferred form of such a machine will be described in detail later.

If a simple tangential machine is throttled by increasing resistance on the suction or pressure side of the rotor, whether by apparatus with which the machine is used (e.g. a filter becoming clogged) or by specially provided throttle means, then throughput will tend to fall and the pressure drop in the apparatus to rise; this continues to a critical point after which further throttling induces a degree of instability. This characteristic of the tangential machine is no drawback for many applications, such as a simple table fan or fan heater, but for other applications especially those of a more sophisticated sort, it can be a disadvantage so serious as to preclude use of the tangential fan altogether. One main object of the invention is to improve the stability of the machine at lower throughput. Another object is to provide a tangential machine which is adjustable so that notwithstanding a reduced throughput of the machine the pressure it produces can be maintained at a desired value.

With these objects in view the invention provides a machine of the cross-flow type having by-pass means which provide a channel for a flow of fluid through the rotor additional to that between the inlet and outlet oi the machine so that the throughput of the rotor exceeds that of the machine as a whole. The by-pass flow is of course distinct from and additional to the recirculating flow in the vortex core region.

' The by-pass means may be provided in a tangential machine as defined, by two parts of a guide body adjacent which the Vortex forms, which parts are adapted to define an opening upstream of the outlet for recirculation of fluid from the pressure region to the suction region which may itself form the inlet. The two guide body parts are preferably adjustable, so that the amount of recirculation can be varied; this also makes it possible to vary within limits the pressure produced with a given throughput or to maintain constant pressure with varying throughput.

Another form of by-pass means provided by the invention is a diifuser leading fluid from the pressure region to the outlet which diffuser defines openings leading boundary layer flow back to the suction region of the machine. This tends to improve conversion of velocity to static pressure energy in the diffuser. If the machine operates against a back pressure, recirculation back to the suction region requires no duct, but if the machine is delivering to ambient fluid then a duct is provided leading flow from said diffuser openings back to the suction region.

Yet another form of by-pass means may be used according to the invention when a cross-flow machine is required to produce a sub-ambient pressure at the inlet; in this aspect the invention provides a duct leading from the inlet of the machine to the suction region adjacent the rotor, the duct having two adjacent portions the first of larger cross-sectional area and the second of smaller cross-sectional area the first leading into the second in the direction of flow to define an opening for entrance of ambient fluid into said duct downstream of the inlet.

Various preferred embodiments of the invention will now be described by way of example and with reference to the accompanying diagrammatic drawings; in which FIGURE 1 is a cross-sectional view of a fluid machine having by-pass means in accordance with the invention;

FIGURE 2 is a graph illustrating velocity of fluid flow at the outlet of a cross-flow fluid machine utilizing a fluid vortex for guiding in part the flow through the rotor of the machine;

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

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

FIGURE 5 illustrates the ideal fluid flow occurring in one half the cross-sectional area of arotor of a fluid machine constructed according to the invention;

FIGURE 6 is a vector diagram illustrating flow of fluid contacting a blade of rotor of a machine constructed according to the invention where the fluid is passing from the interior of the rotor to the exit side of the machine:

FIGURE 7 is a view similar to FIGURE 1 showing the machine thereof adjusted for recirculation from the pressure region to the inlet of the machine;

FIGURE 8 is a graph illustrating the average pressure dilference between the inlet and outlet as compared with the throughput of a machine constructed according to the invention;

FIGURE 9 is a diagrammatic view of a diffuser combined with means for recirculating boundary layer from the diffuser sidewalls to the suction region of a machine constructed according to the invention, and adapted to produce sub-ambient pressure at the inlet;

FIGURE 10 is a diagrammatic view illustrating another manner combining a diffuser and cross-flow machine according to the invention, the machine being adapted to operate against a back pressure; and

FIGURE 11 is a partial cross-sectional view of a modified inlet arrangement for a cross-flow machine adapted to produce sub-ambient pressure at the inlet, this machine also having fluid by-pass means as called for by the present invention.

Referring first to FIGURE 1, the flow machine there shown comprises a cylindrically bladed rotor 2 having thereon a plurality of blades 3 concavely curved in the direction of rotation of the rotor indicated by the arrow 4 wherein the blades 3 have their outer edges 5 leading their inner edges 6. The outer edges define an outer envelope 7 while the inner edges define an inner envelope 8 when the rotor is rotated. The rotor is mounted, by means not shown, whereby it will rotate about its axis. A guide wall 9 extends the length of the rotor and merges with a wall 10 to form one side of an exit duct 11 of the machine. A vortex-forming and stabilizing means 12 also extends the length of the rotor and is positioned exteriorly thereof and has thereon a wall 13 which forms part of the exit duct and which more particularly forms part of a diffuser section 14 as is more fully explained hereafter.

The vortex-forming and stabilizing means 12 has a rounded end 15 which has a portion extending towards the rotor in the direction of rotation to form a converging gap 16 which, as more fully explained hereafter, serves to form and stabilize a fluid vortex when the rotor is rotated. The means 12 also serves to separate the suction side S from the pressure side or discharge region P of the machine and defines with the wall 9 an entry and an exit region to the rotor. End Walls 19, only one of which is shown, substantially cover the ends of the machine.

The wall 9 terminates at point 20 which is spaced from the rotor a minimum of one-third the blade depth and not more than three times the blade depth of the blades 3 in order to minimize interference which causes an undesirable noise when the machine is operated while at the same time the wall provides a means to guide the flow leaving the machine. Wall 15 of the vortexforming and stabilizing means 12 likewise is spaced a substantial distance from the rotor, in this instance a distance equal to a minimum distance of at least onethird the blade depth of the blades of the rotor. Because both the wall 9 and the vortex-forming and stabilizing means 12 are spaced from the latter a substantial distance, close manufacturing tolerances do not have to be observed when assembling the machine and, as such, the machine lends itself to economical construction such as is achieved when sheet metal stampings are utilized.

In operation of the fluid machine illustrated in FIG URE 1, a fluid vortex having a core designated by the line V approximating a Rankine type vortex is formed wherein the core is positioned eccentrically with respect to the rotor axis and wherein the core will interpenetrate the path of the rotating blades of the rotor such that a portion of the fluid from the discharge region is recirculated back into the interior of the rotor. The whole throughput of the machine will then flow twice through the blade envelope in a direction perpendicular to the rotor axis indicated by the flow lines F, MF.

FIGURE 4 illustrates an ideal relation of the vortex to the rotor 2 and the distribution of flow velocity in the vortex and in the field of the vortex. The line 40 represents a part of the inner envelope 6 of the rotor blades 3 projected onto a straight line while the line -41 represents a radius of the rotor taken through the axis of the vortex core V. Velocity of fluid at points on the line 41 by reason of the vortex is indicated by the

horizontal lines

43a, 43b, 45c and 43d, the length of these lines being the measure of the velocity at the points 43a 43b 43c 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 441) to the core. It will be understood that the curve shown in FIGURE 4 represents the velocity of fluid where an ideal or mathematical 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 V 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 43a and 43b, and in actual practice, the profile will still be substantially that shown in FIG- URE 4 so that there will be in the region of the periphery of the core V shown in FIGURE 1 a flow tube MP of high velocity and the velocity profile taken at the exit of the rotor will be similar to that shown in FIGURE 2 where the line FG represents the exit of the rotor 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 flow is concentrated in the portion of the output represented by the line AE which is less than 30% of the total exit of the rotor. 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 principle 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 flow tube indicated as MP in FIGURE 1. With a given construction the physical location of the flow tube MF may be closely defined. The relative velocity between the blades and fluid in the restricted zone of the rotor blades 3 through which the flow tube MF passes is much higher than it would be if a flow machine were designed following the conditions adhered to heretofore in the art respecting 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 the flow tube MF passes than if that flow tube had the average velocity of throughput taken over the whole exit of the rotor. There is a more efficient 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 eificiency.

FIGURE 5 illustrates the ideal distribution of flow tubes F occurring within one half the rotor area defined by the inner envelope 6, it being understood that the flow tubes in the other half of the rotor are similar. The maximum velocity flow tube MP 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 maximum velocity flow tube MF undergoes a change of direction of substantially 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 throughput, represented by the flow tube MF, passes through the rotor blades where they have a component of velocity in a direction opposite to the main direction of flow 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 asdetermined 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, on the other hand, is considered as being largely determined by the configuration of the vortex forming means which forms and stabilizes a vertex in cooperation 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 over-all 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 substantially greater than 90.

It is to be appreciated that the flow lines of FIGURE 1 do not correspond exactly to the position of the vortex core V 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 osculates that envelope. Although this position is achieved in certain constructions hereinafter described, it is not essential, and in fact, is not achieved in the structure shown in FIGURE 1.

It is to be further appreciated that despite the divergence of the flow in FIGURE 1 from the ideal, the maximum velocity flow tube MF with which is associated the major part of the throughput is nevertheless turned through an angle of substantially 180 in passing from the suction to the pressure side of the rotor and that this maximum flow tube passes through the rotor blades where the blades have a velocity with a component opposite to the main direction of flow through the rot-or as indicated by the arrow A.

Referring now again to FIGURE 1, and also to FIG- URE 7 which shows another condition of the FIGURE 1 apparatus, it will be seen that the guide body 12 comprises a fixed body member 100 and a movable body member 101 which is pivoted about an axis 106 extending parallel to the rotor axis and substantially at the centre of the arc defined by the surface 15. The movable body member 101 has a wall 103 on the pressure side which in the closed condition of the member shown in FIGURE 1 fairs into the exit duct wall 13. When the movable body 101 is pivoted about axis 106 to the open position as shown in FIGURE 7, the rounded end surface 15 adjacent the rotor 1 presents approximately the same profile to the fluid leaving the rotor so that the vortex continues to be formed and remains substantially in the same position as shown in FIGURE 10. At least a portion of the high velocity tube MF, however, is no longer guided to the outlet of the machine by the walls 103 and 104, but instead is guided back to the entry side of the rotor through a passage or by-pass 107 formed by wall 108 of body 101 and wall 109 of body 100 to again re-enter the rotor on the suction side of the machine, and in so doing, it forms a closed circuit as indicated in FIGURE 7. As a result of this construction, the throughput of the rotor exceeds that of the machine as a whole with the throughput of the machine being only that flow which is not recirculated back to the suction side and which, as indicated previously, comprises only a proportion of the total throughput of the rotor.

FIGURE 8 represents a comparison of the fluid pressure difference across a machine constructed according to the invention with the throughput volume where X represents the average pressure diiference between the suction and pressure sides of the machine and p represents the throughput volume. The curve represents the comparison of x difference with qb when the machine of FIGURES 1 and 7 has the body 101 in the closed position shown in FIGURE 1. The curve 121 represents the pressure difference across the machine when the member 101 takes the open position shown in FIGURE 7.

It will be seen that as the machine in its FIGURE 1 condition is throttled from free-delivery =0) the pressure rises to a maximum 122 and that on further throttling the machine enters an unstable region illustrated by the dotted part of the curve. The machine cannot be used in this region. By contrast, if the member 101 is moved to the open position shown in FIGURE 7 the throughput at free delivery is less, but the pressure rises gradually to a maximum at or near zero throughput. Throughput here means the quantity of fluid moved between inlet and outlet: in the closed (FIGURE 1) condition of the member 101 reduction of throughput correspondingly reduces the amount of fluid passing the rotor, while in the open condition of the member 101 (FIGURE 7) the amount of fluid passing the rotor, by reason of recirculation through the by-pass 107, remains at a sufficient level to ensure stability despite a reduction of the throughput of the machine as a whole. This characteristic of the machine is important when throttling is anticipated, either by special control means, or for example by clogging of a filter in apparatus with which the machine is used. This characteristic is also important where several machines such as that shown in FIGURES 1 and 7 are operated in parallel Where it is desired that the pressure in the circuits be substantially the same.

The movable member 101 permits the user of the machine of FIGURES 1 and 7 to choose which of the

characteristics

120, 121 of FIGURE 8 to operate on, whether by manual or automatic control. Thus for free delivery the member 101 can be held closed, and only opened at a given pressure. Some intermediate characteristic can be obtained by partial opening of the by-pass 107. However it it to'be understood that the member 101 may be fixed in position if the possibility of regulation is not required for a given application of the machine.

' Unless the outlet of the machine according to the invention is constructed as a diffuser, pressure at the outlet will be general be low. Diffuser construction thus is important when the machine is to be used to increase pressure of a fluid and special problems arise when used in a machine constructed according to the invention because of the particular velocity profile at the outlet of the machine. Referring to FIGURE 9, a diffuser is illustrated providing the by-pass effect with which the invention is concerned and enabling the efiiciency of conversion of velocity to pressure energy to be substantially improved. The structure illustrated comprises a cross-flow machine (e.g. such as illustrated in FIGURE 1 but with the guide body 12 in one piece) having a duct 131 leading from an inlet 131a to the suction side 130a of the machine which is at sub-ambient pressure and a diffuser section 132 connected to the pressure side 1301) of the flow machine and leading to an outlet 132. The walls of the -diifuser section are perforated as shown at 133 in the region where the tendency of the boundary layer to separate from the walls of the diffuser is the greatest. Conduit means 134 connect the perforations with the suction side of the flow machine so that the flow comprising the boundary layer is removed through the perforations by suction and is recycled back to the suction side 130a of the machine 130'. In this way, laminar flow will be preserved over a greater area of the diffuser so increasing pressure and permitting a wider diffuser angle.

The structure illustrated in FIGURE 10 is generally similar to that illustrated in FIGURE 9 except that no positive means are included for recirculating the fluid comprising the boundary layer. The diffuser 132' delivers not direct to the outlet but through means producing a back pressure (such as a heat exchanger) and thence to the outlet here designated 1453a. The inlet duct 131 of FIGURE 9 is omitted and the suction side 130a of the machine 130 forms the inlet. The back pressure against which the machine works is the determining factor controlling the passage of the fluid constituting the boundary layer through the perforations 133 with a high back pressure resulting in a greater flow through the perforations.

Referring to FIGURE 8, it is to be noted that if a machine according to that shown in FIGURE 1 (with guide body 12 formed in one piece) has a diffuser such as that shown in FIGURE 9 or FIGURE 10, the machine will operate over a curve 121, by reason of the recirculation through the diffuser side wall openings 133.

Where the pressure drop is on the inlet side of the apparatus, a similar effect can be achieved by a duct arrangement such as that shown in FIGURE 11 where a duct 150 leads fluid from an inlet 151 to the suction side 152 of a flow machine designated generally 153 such as previously discussed, generally corresponding parts being given the reference numerals of FIGURE 1. The duct 150 comprises two adjacent portions 154, 155. Duct portion 154 extends within the upstream end of duct portion 155 with a clearance so as to form an annular by-pass passage 156. When the pressure in duct portion 154 is considerably below that of the surrounding fluid or atmosphere by reason of throttling adjacent the inlet 151, the fluid will then pass through the passage 156 along the flow line F into the duct 154 and thence to the flow machine 153 such that the amount of fluid passing the rotor 2 is raised. The efiect of this by-pass flow is once again illustrated in FIGURE 8. The length and cross-section of the by-pass passage 156 should be designed to balance the dynamic pressure due to the moving fluid stream at the periphery of the duct 155 against the static pressure difference between the interior of the duct 154 and the exterior. The by-pass flow will then be to some extent self-regulating.

I claim:

1. A fluid flow machine comprising a cylindrical rotor mounted for rotation about its axis in a predetermined direction and defining an interior space, guide means extending the length of the rotor and defining therewith a suction region and a pressure region the guide means comprising a guide body between pressure and suction regions going in said predetermined direction and guide wall opposite the guide body and defining therewith said pressure region, the guide means and rotor cooperating on rotation of the latter in said predetermined direction to set up a vortex of Rankine character having a core region eccentric of the roto axis and adjacent the guide body and a field region wherein fluid is guided from the suction region through the path of the rotating blades of the rotor to the interior space within the rotor and thence again through the path of the rotating blades of the rotor to the pressure region, flow taking place through the rotor in planes transverse to the rotor axis and as seen in such planes being strongly curved about the vortex core, said pressure region leading to an outlet for the machine and said guide body including parts to define an opening upstream of the outlet for recirculation of fluid from the pressure region to the suction region and thence again through the rotor whereby the fluid throughput of the rotor-exceeds the throughput through said outlet; the parts of said body comprising a movable part and a fixed part with the parts of said guide body in one position defining a substantially smooth imperforate wall and in another position defining said opening.

2. A flow machine as claimed in claim 1, wherein said 8 movable guide body part is pivotally mounted adjacent the rotor.

3. A flow machine having an inlet and an outlet wherein the pressure differential between said inlet and outlet is subject to variance, said machine comprising a cylindrical bladed rotor mounted for rotation about its axis in a predetermined direction and defining an interior space, guide means extending the length of the rotor and defining therewith a suction region on the inlet side of the rotor and a discharge region on the outlet side of the rotor, the guide means comprising a guide body between discharge and suction regions going in said predetermined direction and a guide wall opposite the guide body and defining therewith said discharge region with said guide wall and guide body being spaced from said rotor by substantially more than a working clearance, the guide means and rotor cooperating on rotation of the latter in said predetermined direction to set up a vortex of Rankine character having a core region eccentric of the rotor axis and adjacent the guide body whereby fluid is recirculated from said discharge region into the interior space of the rotor, said vortex forming a field region wherein fluid is guided from the suction region through the path of the rotating blades of the rotor to the interior space within the rotor and thence again through the path of the rotating blades of the rotor to the discharge region, flow taking place through the rotor in planes transverse to the rotor axis and as seen in planes being strongly curved about the vortex core with the stream tubes of fluid adjacent the guide body being turned approximately 180 and with the main flow of fluid through said machine being turned more than and fluid bypass means comprising a passage extending between said discharge region and said suction region to provide for flow of fluid through the rotor additional to the fluid flow between the inlet and outlet wherein the fluid flow in said passage is responsive to change in differential pressure between said inlet and outlet such that fluid flow in said passage increases with increase in diflerential pressure, whereby the fluid throughput of the rotor between suction and discharge regions exceeds the fluid throughput of the machine between inlet and outlet such that tendency of collapse of said vortex due to increase in differential pressure between said inlet and said outlet is reduced.

4. A fluid flow machine as claimed in claim 3, including an outlet duct leading fluid from the discharge region to said outlet, wherein the bypass means comprises a portion of the outlet duct having at least one opening therein through which at least part of the flow in said outlet duct may flow back to the suction region for recirculation through the rotor.

5. A fluid flow machine as claimed in claim 3 including an inlet duct leading fluid from the inlet to said suction region wherein the bypass means comprises a portion of the inlet duct having at least one opening through which at least part of the flow in said outlet duct may flow back to the suction region for recirculation through the rotor.

References Cited UNITED STATES PATENTS 2,808,197 10/1957 Forgo 230-122 2,942,773 6/1960 Eck 230125 3,033,441 5/1962 Coester 230125 3,035,760 5/1962 Simmons 230-425 FOREIGN PATENTS 963,773 1/1950 France.

DONLEY J. STOCKING, Primary Examiner.

HENRY F, RADUAZO, MARK NEWMAN, Examiners.

Claims

1. A FLUID FLOW MACHINE COMPRISING A CYLINDRICAL ROTOR MOUNTED FOR ROTATION ABOUT ITS AXIS IN A PREDETERMINED DIRECTION AND DEFINING AN INTERIOR SPACE, GUIDE MEANS EXTENDING THE LENGTH OF THE ROTOR AND DEFINING THEREWITH A SUCTION REGION AND A PRESSURE REGION THE GUIDE MEANS COMPRISING A GUIDE BODY BETWEEN PRESSURE AND SUCTION REGIONS GOING IN SAID PREDETERMINED DIRECTION AND GUIDE WALL OPPOSITE THE GUIDE BODY AND DEFINING THEREWITH SAID PRESSURE REGION, THE GUIDE MEANS AND ROTOR COOPERATING ON ROTATION OF THE LATTER IN SAID PREDETERMINED DIRECTION TO SET UP A VORTEX OF RANKINE CHARACTER HAVING A CORE REGION ECCENTRIC OF THE ROTOR AXIS AND ADJACENT THE GUIDE BODY AND A FIELD REGION WHEREIN FLUID IS GUIDED FROM THE SUCTION REGION THROUGH THE PATH OF THE ROTATING BLADES OF THE ROTOR TO THE INTERIOR SPACE WITHIN THE ROTOR AND THENCE AGAIN THROUGH THE PATH OF THE ROTATING BLADES OF THE ROTOR TO THE PRESSURE REGION, FLOW TAKING PLACE THROUGH THE ROTOR IN PLANES TRANSVERSE TO THE ROTOR AXIS AND AS SEEN IN SUCH PLANES BEING STRONGLY CURVED ABOUT THE VORTEX CORE, SAID PRESSURE REGION LEADING TO AN OUTLET FOR THE MACHINE AND SAID GUIDE BODY INCLUDING PARTS TO DEFINE AN OPENING UPSTREAM OF THE OUTLET FOR RECIRCULATION OF FLUID FROM THE PRESSURE REGION TO THE SUCTION REGION AND THENCE AGAIN THROUGH THE ROTOR WHEREBY THE FLUID THROUGHPUT OF THE ROTOR-EXCEEDS THE THROUGHPUT THROUGH SAID OUTLET; THE PARTS OF SAID BODY COMPRISING A MOVABLE PART AND A FIXED PART WITH THE PARTS OF SAID GUIDE BODY IN ONE POSITION DEFINING A SUBSTANTIALLY SMOOTH IMPERFORATE WALL AND IN ANOTHER POSITION DEFINING SAID OPENING.