US2314058A - Pump - Google Patents

Description

March 1 6, 1943. E. A. STALKER PUMP Filed June 25, 1941 2 Sheets-Sheet 1 March 16, 1943- E. A. STALKER PUMP Filed June 23, 1941 2 Sheets-Sheet 2 INVENTOR gum0 application Serial No. 313,967.

along line 5 5 in Figure 2; Figure 6 is a schematic view of the blades and guide vanes for a portion of a curved section Where- I Patented Mei-.16, i943 11 .v ST ES EN omce wa A.8taIke -,marbor,meu Application June 23, 19M, N 399, 19

' '15 claims. (cure-12a) My invention relates to pumps and-other fluid bathed machines and their elements and particularly to the axial flow type; and it has for its objects, first to provideja blower of small size capable of handlinglarge volumes of fluid at large pressures; second to provide amachine of claims. 7

An airfoil section similar to the one used for the blower blades is described for aircraft in my Figure 1 is an axial section through the blower;

Figure 1a pertains to the'theory of vane impellers; e

Figure 3 is a section along the line 3-3 in Figure 1;

Figure- 4 is a chordwise section through an im peller blade along line l-l'inFigure 2; j

Figure 5 is a fragmentary section of the annular ring about the ends of the impellerblades,

through the blades and vanes.

Axial flow pumps in the form of blowers have already established their usefulness in industry.

They are eflicient and well adapted for direct drive by high speed prime movers. They are however expensive if high pressures are to be generatedsince only a small pressure rise can be generated at each stage. The cost is high because of the great number of stages required and the great number of blades required in each stage.

The present invention utilizes blades .of high.

camber and means to increase thelift coeiflcient of the blades and to reduce the profile drag coefficient thereof.

The thrust T on the pumped fluid provided by an element of any blade can be expressed closely for'all the blades in the stage as .T -cepgBA cos (1) I ct=the lift coefficient.

=the density in slugs per cubic foot. 'V=the resultant velocity relative to the fluid.

l3f= the number of blades;

The pressure on the fluid. is found from the thrust by divldingEquation l by the cross sec- 60 -ti'onal area S which the fluid flows axp=cip mj a (2) This equation shows that the pressure per stage can be increased through increasing 01.. In fact if the efllciency is to be high this is the only 10 means of increasing the pressure since the ratio of blade area to duct area cannot be increased ever present practice without engendering large interference losses. I

The zero lift line of an airfoil section is readily I found; according to well known geometric con- I structions or .it can be established by experiment. The true angle of attack of the airfoil is who measured between this line and the direction of the resultant fluid motion relative to the airfoil.

The resultant motion is found from the compo- 'siticn of the axial and rotational motion of the airfoil relative to the fluid.

higher values at all angles of attack. The maximum height of the mean camber line above its subtending chord can be as great as 75 per cent of the chord length.

In order to produce a blade with a high lift coefficient and a low drag I have had to devise a new airfoil section. In particular the maximum height of the mean camber line should be very chord length. This value is far greater than any in use andin fact exceeds the value that could be used with no slot. In other words if there were no slot; the flow would not follow the upper contour even for customary angles of attack. Thus the mean camber. maximum height is preferably greater than 12 per cent-of the chord length. It may have an upper value as high as 75 per cent but Iprefer. to use .a-value of about 35 per cent. The upper contour'should have a large radius of curvature.

The drag of the m en-section is lemma.

before this happens there is some'turbulen'ce with-' wing. It might be thought therefore that a wing section of such high camber that the flow is burbled at customary angles of attack would give too high a drag even without a slot. However with th slot providing a let the flow follows the congreat expressed as a percentage of the subtending,

antand it may appear at-flrst that such a high curved section would produce too much drag. v

With the slot arrangement I however this is no'ttrue.

It is true that the drag is high even for ,con-.

ventional wings of high camber even below :the-

angle at which the flow burbles, because even in the boundary layer on the aft portion of the 4 more I apply this to thin wings. Preferably the a thickness should be about 12 per' cent of the chord length.

It may be as thin as 6 per cent and preferably should be less than 20 per cent. Figure 4 defines the chord length C.

These airfoil sections can be characterized by the ratio of the thickness to the maximum camber.

height. This ratio should have a value greater than 0.9 and less than 13.

The best upper surface curvature can also be defined in terms of the angular rate of change of the tangent to the upper surface. This tangent should be applied to the envelope contour of the airfoil section and therefore should exclude the edges themselves of any slot in the wing surface. This rate of change should be expressed with respect to the distance X along the chord subtending the mean camber line of the airfoil section. Let the change in angle of the tangent. be 0 (Figure 4) then the rate of change 0/X should be less than 63510. Thus if X is taken as 0.10 then 0 will be 63.5 degrees. In thin wings using boundary layer control this is too great a rate of change. The value should be in the neighborhood of 180/6. Then if X=0.1C, 0:18 degrees. The rate should be less than 635/0 and greater than 270/0. The thinner the wing the lower th rate should be. The rate should not be constant but should increase rearward along the chord line. A small value should be used Just ahead of the first slot and a larger value ahead of the second slot and so forth.

When the thickness of wings reaches about The case supports the guide vanes 6.

When the shaft 4 is rotated by the prime mover the blades 5 induce a flow through the annular passage 1. The flow enters the inlet 8 and leaves a the exit 9. A portion of the compressed fluid is diverted by passage I 0 to the interior of the blades 5 of the impeller.

As shown in Figures 1 and 4 the blades are hollow and have in their upper surfaces slots ll. Fluid enters the interior of the blades from the passage I0 and provides a jet through the slot substantially tangentially along the blade surface.

The function of the jet is to preclude a reversal of flow in the boundary layer on the upper surface of the blade by adding rearward momentum to the layer and thereby enabling it to oppose the high suction at the nose of the wing which strives to stop the rearward flow. A further description of this phenomenon is described in my U. S. Patent No. 2,084,463. 7

The blades of an impeller have attached to their outer tips a hollow annular tip shield l2 having a slot l3 in it extending a short distance above blade. See Figure 4. This slot is served with fluid from the blade interiors which upon issuance excludes the formation of a vortex in the corner between the blade and the shield. Preferably the junction of the two parts should be made with a flllet of generous radius.

The guide vanes are hollow also and receive fluid from the passage I I. They also have end shields with slots in them similar to that shown in Figure 4.

The fluid going to the blades through passages i0 and I4 is cooled by passing through the coolers I 5 and I6 respectively, which are served with cooling fluid through tubes l1 and 8 and I 9 and 20 from convenient sources.

The flns 2| and 21a also serve for cooling and the conduction of heat away from the compression passage.

- The hub is vented with a narrow annular passage- 22 through which the supporting arms 23 and 24 induce a flow. They are given an airfoil-shape and a pitch setting so that they act as fans. Preferably this passage should be narrow and provided with cooling fins 25.

Figure 1 shows the passage I0 serving all the blades of the impeller but in most cases it will be preferable to exclude the last stage since the pressure rise to serve the slot on the blade is that of only one stage. On the other hand the slot in the first stage is served with a pressure rise equal to that of all the stages. In creating a high lift coefficient it is important to have a large pressure difference between the inlet to the blade and the exit of the blade slot.

There is a disadvantage however in having too great a pressure difference since high velocities through the slots cause undue frictional losses. To reduce the velocity through the blades of the earlier stages which may have too high a pressure difference at the slots the passages I0 and I4 are tapered so that together with the bleeding off of fluid for some stages the restricted annular areas of these passages serves to reduce the pressure at the inlet stages. It is a feature of this invention that these passages i0 and I4 are tapered and subject to bleeding tubes 26 and 21 distributed axially along the lengths of these passages.

The passages in and H in the hub and casing respectively extend circumferentially about substantially the whole perimeter of the blower transverse to the axis of rotation. This is an important feature since the fluid reaches the slots in the blades with a minimum of changes in direction of flow and therefore avoids losses due to turbulence. The walls of the passages are supported at intervals by ribs 2| and 2Ia which also serve to conduct heat away from the main flow in the blower passage I.

The blower illustrated in Figure 1 contains five stages but will do the compressing of twenty stages of the conventional axial flow fan.

The blower case is split longitudinally to facilitate assembly. The rings I2 about the ends of the guide vanes are likewise split.

It is a feature of this invention that the upstream blades have greater angles of attack than the downstream blades. They should also have greater heights of the mean camber maximum ordinates. Figure 6 shows progressively larger angles of attack and cambers in the upstream direction.

The angles of attack are to be measured from the zero lift line. This is a line drawn through the trailing edge along the wind direction for which the lift is zero. This line is marked L=0 in Figure 1a.

inthe blower.

axial 'fiow blower, a

It is customary to refer to the group of blades or wing-like elements arranged peripherally about the hub in one plane as the rotor while the group or guide vanes or wing-like elements in one peripheral plane is called the stator.

These elements are capable of experiencing a said casing interposed between successiveimpeller blades so that said blades and said vanes are alternated along said axis, a duct in said hub in communication with the discharge from said axial passage, said blades being hollow and 7 each having a slot in its surface in communica- 'tion with said duct whereby a jet is discharged from the blade to increase its compressor action,

said duct lying wholly on the axis side of said passage. i

2. In combination in an axial fiow blower, a hub supported for rotation about an axis, a

plurality of impeller blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining a bloweraxial passage for the pumped fiow, a

plurality of guide vanes within said casing interposed between impeller blades so that said blades and said vanes are alternated along said axis, said casing having a duct in communication with the discharge end of said blower passage, said duct having a cross sectional area diminishing toward the inlet end of the blower, said vanes being hollow and having slots in their surfaces in communication with the vane interior, and

Vmeansof communication between the vane interior and said duct. I

3. In combination in an axial flow blower,'a

hub supported for rotation about an axis, a plurality of impeller blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining a blower axial passage for the pumped fiow, a.

plurality of guide vanes within said casing interposed between impeller' blades so that said blades and said vanes are-alternated along said axis, said hub having a duct in communication with the discharge end of said blower passage, said blades being hollow and having slots in their surfaces in communication with said hub duct,

a cooling device in said hub duct and means to pass a coolant therethroush to cool the fiow ,4. In combination in an hub supported for'rotation aboutan axis. a plusrality ofiimpeller blades supported on the hub 1 and distributed axially therethrough, a'casing to house said hub and between'them defining a blower axial passage for the pumped flow, a

plurality of guide vanes within said casing interposed between impeller blades so thatsaid blades and said-vanes are alternated along said axis, a passage in said hub in communication with the discharge end of said blower passage, at least some of said blades being hollow and having rality oi guide vanes within said casing inter-- posed between impeller blades sothat said blades and said vanes are alternated along said axis.

house said hub and between them' defining an axial passage of annular cross section for thepumped flow, a plurality of guide vanes within v 3 slots in their surfaces in communication with said hub passage, said hub having a-aecond passage therein and means to'induce the fiow oi a coolant therethrough.

5. In combination in an axial. fiow blower, a hub supported for rotation about an axis, a pinrality o1 impeller blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining a blower axial passage for the pumped fiowra plusaid blades having slots in their surfaces in communication with their interiors, and means toinduce flows through said slots. 'anupstream blade having a mean cambermaximum ordinate greater than that of a downstream blade.

6. In combination in an axial fiow'blower, a hub supported for rotation about an-axis, a plu-' rality of impellerv blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining a blower passage for the pumped flow, a plurality of hollow guide vanes within said casing-interposed between impeller blades so that said blades and said vanes are alternated along said axis, said vanes having slots in their surfaces-in com- Vmunica'tion with their interiors, and means to induce flows through said; slots, an upstream vane having a mean camber maximum ordinate hub supported for rotation about an axis, a plugreater than that of a downstream vane. V

7. In combination. in an axial flow blower, a

rality of impeller blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining a.

blower axial passage for the pumped flow, a plurality of guide vaneswithin said casing interposed between impeller blades so that said blades and said vanes are alternated along said axis,- said blades having slots in their surfaces in communication with their interiors, and means to induce flows through said slots, the angles ofattack of the blades measured between the plane of rotation and the zero lift lines of the airfoil sections of the blades increasing upstream of the pumped fiow. H

8. In combination in an axialfiow blower, a hub supported for rotation about an axis, a pinrality of impeller blades supported on the hub I and distributed axially therealong, acasing to house said hub and between them defining ablower passage for the pumped flow, a plurality of hollow guide vanes within said casing interposed between impeller blades sothatsaid blades and said vanes are altemated'along said axis,

said vanes having slots in their surfaces in communication with their interiors, andmeans to induce fiows through said'slots, the angles of attack of theblades measured between the plane of rotation and the zero lift lines of the airfoil sections of the blades increasing upstream of the pumped fiow. i

9. In combination in an axial ilow blower, a hub supported for rotation about an axis, a plurality of impeller blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining a blower passage for the pumped flow, aplurality of hollow. guide vanes within saidcasing interposed between impeller blades so that said blades and said vanes are alternated along said axis, said vanes having slots in their surfaces in communication with their interiors, and blower means in communication with the vane interiors through their ends to induce flows through said slots, said guide vanes having their leading edges substantially transverse to the axis of rotation of the impeller blades.

10. In combination in an axial flow blower, a hub supported for rotation about an axis, a plurality of impeller blades supported in the hub and distributed axially therealon a casing to house said hub and between them defining a blower passage for the pumped flow, a plurality of guide vanes within said casing interposed between impeller blades and alternated therewith along the blower axis, said blades having slots in their surfaces in communication with their interiors, said hub having an axial passage therein in communication with the exit. end of said blower passage and with the interiors of said blades, said hub passage extending circumferentially about the major part of the hub perimeter transverse to the blower axis.

11. In combination in an axial flow blower, a hub supported for rotation about an axis, a pinrality of impeller blades supported on the hub anddistributed axially therealong, a casing to house said hub and between them defining a. blower passage for the pumped flow, a plurality of hollow guide vanes within said casing interposed between impeller blades and alternated therewith along the blower axis, said vanes having slots in their surfaces in communication with their interiors, said casing having an axial passage therein in communication with the exit end of said blower passage and with the interiors of said vanes. said casing passage extending circumferentially about the major part of the blower perimeter transverse to the axis of the blower.

12. In combination in an axial flow fluid machine, a hub supported for rotation about an axis, a plurality of wing-like elements supported on the hub and distributed axially therealong, a casing to house said hub and between them defining an axial passage for the pumped flow, a plurality of wing-like elements supported in said casing interposed between axially successive elements on the said hub, at least one of said elements being hollow and having a slot in its surface, a duct in said machine in communication with said passage at a locality removed a substantial distance axially from said element and in communication with the interior of said element to induce a flow through its slot to increase its compressor action, said element having its communication opening with said duct on the same sideof said flow passage as the duct opening into said flow passage.

13. In combination in an axial flow blower a hub supported for rotation about an axis, a plurality of impeller blades supported on the hub and distributed axially therealong, a casing to house said hub and between them defining an axial passage of annular cross sections for the pumped flow, a plurality of guide vanes fixed to said casing interior and interposed between successive impeller blades so that said blades and vanes are alternated along said axis, a duct in said hub in communication with said axial passage, said blades being hollow and each having a slot in its surface in communication with said duct whereby a flow is induced through said slot to increase its compressor action, the majority oi. said blades being removed from the opening of said duct into said axial passage by at least one intervening stage of impellers so that a large pressure difierence exists between the inlet and exit ends of said duct.

14. In combination in an axial flow fluid machine, a hub supported for rotation about an axis, a plurality of rotor elements supported on the hub and distributed axially therealong, a casing to house said hub and between them defining an axial flow passage for the main flow of fluid, a plurality of stator elements within said casing interposed between rotor elements so that said rotor and said stator elements are alternated along said axis, said machine having an auxiliary duct, said elements being hollow and having slots in their surfaces in communication with said duct, and means to supply a fluid flow to the interiors of said hollow elements, said flow having a lower temperature than the flow in said main passage.

15 In combination in an axial flow fluid machine, a hub supported for rotation about an axis, a plurality of wing-like rotor elements supported on the hub and distributed axially therealong, a casing to house said hub and between them defining an axially extending flow passage for the main flow of fluid, a plurality of wing-like stator elements within said casing interposed between rotor elements so that said rotor and said stator elements are alternated along said axis, at least some of said elements being hollow and having slots in their surfaces, and an auxiliary duct communicating with said hollow elements and with a zone of substantially greater fluid pressure than that in the zone of said hollow elements for creating a flow of fluid through said slots to cause the main fluid flow to follow the contour of said elements.

EDWARD A. STALKER.

Certificate of Correction Patent No. 2,314,058. March 16, 1943.

EDWARD A. STALKER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, lines 4647,

. 2 and second column, lines 3-4, for that portion of the equations reading C p read Gig; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Potent Oflice.

Signed and sealed this 18th day of May, A. D. 1943.

[SEAL] I HENRY VAN ARSDALE;

Acting Commissioner of Patents.

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