US 3244400 A
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Aprll 5, 1966 w. s. SAUNDERS 3,244,400 EXTENDED RANGE CASCADE FOR TORQUE CONVERTERS AND TURBO-MACHINERY Filed Oct. 30, 1964 2 Sheets-Sheet 1 FIG 4 W.SEL DEN SAUNDERS FIG 5 April 5, 1966 w. s. SAUNDERS 3,244,400
EXTENDED RANGE CASCADE FOR TORQUE CONVERTERS AND TURBO-MACHINERY Filed Oct. 50, 1964 2, Sheets-Sheet 2 INVENIOR W. SELDEN SA UNDERS United States Patent 3,244,400 EXTENDED RANGE CASCADE FOR TORQUE CONVERTERS AND TURBO-MACHINERY Walter Selden Saunders, Bethesda, Md. (24 S. Chester Road, West Chester, Pa.) Filed Oct. 30, 1964, Ser. No. 407,740 12 Claims. (Cl. 253-77) The present invention relates to cascades of fluid turning blades as used in torque converters and other types of turbo-machinery. Such blade cascades are required to operate over a wide range of inlet angles. When the inlet angle is other than that at design center, there are large losses of energy from the fluid. Therefore, the conventional cascade has a limited range of inlet angles over which it will give efficient performance.
It is the object of this invention to extend the useful range of inlet angles of a cascade of fluid turning blades.
A further object is to provide an extended range cascade of blades of simple and reliable construction without the use of mechanically movable elements between the blades and their supports.
v Yet a further object is to provide an extended range cascade that can be manufactured at low cost.
The useful range of the cascade is extended by the presentinvention by providing a smaller auxiliary blade for each main blade, spaced in such a way that a quasi-stable vortex is trapped between the two blades thereby reducing the energy losses in the fluid at large angles of incidence without seriously affecting the performance of the cascade at small angles of incidence.
FIG. 1 is diagrammatic representation of the fluid flow about the sections of .three members of a cascade of fluid turning blades. e
TFIG, 2 is similar to FIG. 1, except that the auxiliary blades o f the present invention are included.
FIG. 3 is a sectionof one thin sheet metal blade and its' 'auxiliary blade. V
FIG. 4 is a diagrammatic representation of two main blades of a cascade, each with two auxiliary blades.
f FIGQS is a diagrammatic representation of three main blades in a cascade, each having three auxiliary blades. A different mode of .flow is illustrated for each main blade. "f. FIG. 6 shows two blades of a cascade, each having one auxiliary blade.'
- FIG. 7 is a section through one main blade of a cascade and its'lauxiliary blade.
FIG. 8 is a section through one slotted main blade of a cascade havingone auxiliary blade.
Referring to FIG. 1, the blades 1, 2, 3 of the cascade havefa chord length 0, a pitch spacing P, and a mean camberline 4. The fluid flow through the cascade isrepresented by the streamlines 5. The angle of attack or incidence A is that angle between the approaching flow and the camberline 4, at the nose of the blade 6.
When the incidence A is near zero as shown for blade 1.inthecascade, the flow progresses through the cascade smoothly with minimum loss. The streamline 7 which attaches to the blade remains attached over almost the entirelength of the blade. However, when the angle A is increased, as shown for the middle cascade 2, the streamline 7 separates'near the nose of the blade 6, and a large wake region 8 is formed between the streamline 9 and the blade 2. The violent turbulence generated in this Wake accounts for a major portion of the energy losses occurring .at large values of A.
1 In FIG. 2 auxiliary blades 10, 11, 12 'with chord 0' have been added to the cascade of FIG. 1 in accordance with the. concept of the present invention. The nose of 12 is spaced a distance x behind the nose of the main blade 3 and it is spaced above 3 by the distance H. When the flow approaches at a small angle of attack A as shown for the top blade 1, it will traverse the cascade smoothly as in FIG. 1. However, when the angle A is increased, the flow pattern is completely changed as shown by the diagram of the flow around the middle blade 20f the cascade in FIG. 2. The streamline 7 still separates at the nose 6. But, the separated streamline 9'then reattaches for at least a part of the time to the small blade 11. Thus, a quasi-stable vortex 1 3 is formed in the space between 11 and 2. The vortex 13 is trapped in this space and a large turbulent wake does not form in this region. Therefore, the losses shown in the region 8 of FIG. 1 do not occur and the cascade of FIG. 2 has an extended range of eflicient performance.
The dividing streamline 9 then leaves the small blade 11. It may reattach to the main blade 2 for part of the time. Thus, the quasi-stable vortices such as 14 may form. The surrounding flow 5 now behaves to some extent as though the region enclosed by the streamline 9 were filled with solid material. Thus, the performance of a thick, bulbous nose blade at large A is obtained. However, the excessive losses of such a thick blade at small A are avoided.
The present invention may also be applied to vanes made from sheet metal stampings. One such blade 15 from a cascade is shown in FIG. 3. The auxiliary blade 16 bears a similar fixed spatial relation to the main blade as'that shown in FIG. 2. In quantity production, the sheet metal vanes are cheaper to produce. Through the use of the present invention it is possible to obtain extended range performance with sheet metal blades that is usually expected only from thicker, formedblades.
The conventional use of excessively thick bulbous nose I blades and other forms of auxiliary blades and slotted blades in cascade results from the attempt to prevent any separation from the main blade. In fact the very term streamlined refers to a body or passage so shaped as to keep separated regions of flow to a minimum. In contrast to this, the present invention makes noattempt whatsoever to prevent the separation of the flowfrorn the nose of the main blade at large A. Instead, the auxiliary blade is so positioned that it intercepts the separated streamline thereby trapping a quasi-stable vortex. Althougha large region of' separated flow exists, nevertheless the energy losses of the flow through the cascade are substantially reduced by this novel use of the auxiliary blade. Fur-. thermore, this location of the smaller blade does not com promise 'the performance of the cascade excessively at negative values of A and it provides conventional guide. vane action for moderate positive values of A. t
The specific cascades of FIGS. 1, 2 and 3 all operate at design centers when the flow approaches at A=0. The mean eamberline is a circular arc of 70. The pitch to chord ratio is P/c=0.5 for the cascade of FIG. 1. This cascade is very similar to that used as the reactor cascade in many three element torque converters.
I have determined that as in FIGS. 2 and 3 an auxiliary blade 16 with chord c' ='0.3c, formed with a camber line of the same radius as the main blade, should be added with its nose 2. distance x=0.14c behind the vane of the main blade 15 and at a height H=O.l4c above the main blade in order to trap quasi-stable vortices and reduce the flow losses at A=45. I have further determined that the passage formed between the two blades, 15 and 16 should have about the same percent of contraction along its length as does the turbine cascade as a whole. Accordingly the height at the rear of the blade 16 is set at 11:0.1 20. This allows the surface area of the small blade 16, to carry its share of the effort of turning the fluid, at
, A=0; (Note that H c' is approximately equal to P/c.)
aaaaaoo Therefore, the pitch to chord ratio in FIGS. 2 and 3 may be increased by approximately the corersponding amount (to P/c=0.65). This ratio may be increased still further it the camber line is changed from a circular arc to one that concentrates more of the fluid dynamic load in the vicinity of the small blade 16, followed by a sharper concave velocity distribution over the upper rear half of the main blade 15.
It is not now possible to give a general formula that will determine the optimum design of either a conventional cascade or one embodying the present invention for any specific application. The final optimum design is almost always obtained empirically. However, I have determined certain general trends regarding the size and location of the auxiliary vane embodying the present invention.
First, the value of H/c should be less than 1.0 to obtain good stability of the vortices.
Second, the value of H should not be less than about (P/3c) to obtain good loading of the small blade at A=0.
Third, the trapped vortices 13 and 14 will not support a large pressure difference between the inlet region and the outlet region of the passage 17 of FIG. 3. Consequently, the approximate chordal location for the end points of the blade 16 may be determined by choosing two locations at the same pressure from the empirical data on the suction side of the airfoil that would normally be used if the extended range value of A were in fact the design center. By inspection of this data on compressor cascades, it is clear that the present invention will work in these cascades as well as in turning vane and turbine cascades.
Fourth, the eflicient range of a given cascade embodying the present invention may be extended substantially further by increasing c'/ c accompanied by a corresponding increase in H/c, h/c and x/c. Of course this will usually compromise the performance at moderate values of A. However, for the same peak efficiency, the cascade of the present invention will have a wider range than a conventional cascade. Alternatively, for the same range, the present cascade will have a higher peak efliciency.
Futher extensions of the range of the present cascade may be obtained by staging more than one small blade with each main blade so that different sets of quasi-stable vortices are trapped at different angles. For example, an additional small blade 18 may be used on the opposite side of the main blade 19 with auxiliary blade 20 as shown in FIG. 4. The small blade 18 now trap-s vortices 2-1 and 212 at negative angles of incidence in a manner similar to the way 20 traps vortices at positive incidence as explained in connection with FIG. 2.
A further example of staging is given in FIG. 5. Main blades 23, 24, bear the same spatial relation to the small blades 26, 27, 28 as in FIG. 3. For moderate values of incidence as shown for blade 23, blade 26 traps vortices 29 and 30' as in FIG. 2. However, at larger values of incidence 26 loses its effectiveness. Therefore, another set of auxiliary blades 31, 32, 33 is added above 26, 2 7, 28. The flow is shown lfOI. blade 24 in FIG. 5. Blade 32 traps vortices 34 and 35.
7 Additional smaller blades 36, 37, 38 may be added to the rear and above 31, 32, 33. When vortices 2-9 and 30 form, blade 36 traps 39 and 40. At extreme angles of incidence these vortices may form again in the presence of vortices 34 and 3-5 as shown for blade 25 of the cascade.
FIG. 6 illustrates another useful characteristic of the cascade embodying the present invention. Two blades or the cascade 41 and 42 are shown with the properly spaced auxiliaries 4-3 and 44 When the flow is from left to right as shown for the blade 41, the cascade will accept the flow with good efficiency at the angle A=4-5 However, when the flow direction is increased, the output angle of the flow is more nearly parallel to the line of A=0 and not A=45. This flow is illustrated for the lower blade 4*2. This asymmetrical property can be exploited in the cascade of a cross flow blower when the flow into and out of the machine reverses its direction through the cascade with each revolution. Thus, with proper design of the ducts into which the blower is built, this property of the present cascade can increase the efliciency or the machine.
A cusp 45 may be incorporated into the main blade 46 near the top of its leading edge as shown in FIG. 7. The cusp is so located that it helps to stabilize the forward vortex 47 between 46 and the small blade 48 when the flow is at large incidence. When the flow is near zero incidence, the same cusp will form a different vortex 49 so that the losses associated with the insertion of the cusp remain small.
Similarly a cusp 50 may be incorporated to stabilize the rear vortex 51 which is trapped between the small blade 52 and the main blade 5-3, at high incidence. An additional blade 54 is provided with a conventional slot 55 between it and 53. The jet of air passing through the slot 55 helps in stabilizing the vortex 51. As in FIG. 7, a difierent vortex 56 forms in the cusp for low values of the incidence. This vortex is also stabilized by the jet at 55.
Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.
It is claimed and desired to secure by Letters Patent:
1. A cascade of relatively thin fluid turning blades having two diiierent modes of 'iiuid flow comprising a series of main fluid turning blades or relatively large total turning angle adjacently spaced a distance P such that the distance P between two of said main blades is less than the chord length c of one of said main blades and a series of auxiliary fluid turning blades, each said auxiliary blade having a fixed spatial relation to one of said main blades such that said auxiliary blade is adjacent to and spaced from said main blade providing a passage therelbetween, the cross-sectional area of said passage being nearly constant or sli htly diminishing so that said main blade and said auxiliary blade cooperate to provide a smooth flow or fluid through said passage when said fluid approaches the cascade at moderate angles of attack during the first mode or" flow in the cascade; said auxiliary blade being offset a distance H on the opposite side of said main blade with respect to the approaching fluid when said fluid approaches at very large angles of attack with a magnitude exceeding forty-five degrees during the sec- 0nd mode of flow in said cascade, and the nose of said auxiliary blade being located a distance x rearwardly of but near to the nose of said main blade with respect to the direction of the nose portion of the ca-rrrberline of said main blade, so that the fluid approaching at large angles of attack will separate from the nose of said main blade and reatt-aeh near to the nose of said auxiliary blade for an appreciable fraction of the time thereby forming a quasi-stalble trapped vortex in the region Otf the entrance of said passage, said auxiliary blade having a chord length 0' such that its trailing edge is located a substantial distance from the trailing edge of said main blade so that fluid leaving the trailing edge of said auxiliary blade during said second mode of flow will reattach to said main blade for an appreciable fraction of the time thereby forming a quasi-stable vortex near the exit region of said passage, the chord length of said aluxila iary blade being of sufiicient extent so that there is not an appreciable pressure difierence between the entrance region and the exit region of said passage thereby providing that both of said vortices will be reasonably stable and there will be no substantial flow through said pas-.
sage during said second mode of flow.
2. The cascade of claim 1 wherein x is substantially equal to H.
3. The cascade of claim 2 wherein x is substantially equal to .130.
4. The cascade of claim 3 wherein a is substantially equal to 0.3c.
'5. The cascade of claim 1 wherein H/c' is greater than P/Gc.
6. The cascade of claim 1 wherein H/c is less than 1.0.
7. The cascade of claim 1 wherein said main blade is formed with a cus'p cutout of said main blade such that said cusp is adjacent to the nose of said auxiliary blade so that said cusp will form a smaller quasi-stable vortex during said first mode of fiow and will cooperate with the nose of said auxiliary blade to further stabilize said quasi-stable vortex in said region of entrance of said passage during said second mode of flow.
'8. The cascade of claim 1 wherein said m-ain blade incorporates a cusp in the region adjacent to the exit of said passage so that a quasi-stable vortex will form in said cusp during said first mode of flow and said cusp will cooperate with said auxiliary blade to fiurther stabilize said rearward quasi-stable vortex during said second mode or flow.
9. The cascade of claim 8, wherein said main blade incorporates a slot connecting the two sides of said main blade, the exit region of said slot spaced rearw'ardly of but near to said cusp so that the fluid issuing through said slot cooperates with said cusp to further stabilize both of said quasi-stable vortices that form during both or said modes of flow.
10. The cascade of claim 1, and a second set of auxiliary blades each of said second set of auxiliary blades adjacent to and spaced from said m-ain blade and offset from the opposite side otf said main blade with respect to said first set of auxiliary blades so that a third mode of flow occurs in the cascade when the fluid approaches at large negative angles of attack exceeding minus fortyfive degrees, said second auxiliary blade being located a distance reanwardly of but near to the nose of said main blade with respect to the direction of the nose portion of the camberline of said main blade so that the fluid approaching at large negative angles of attack will separate from the nose of said main blade and reattach near to the nose of said second auxiliary blade for an appreciable fraction of the time thereby forming a quasistable vortex in the region between the nose of said second auxiliary blade :and said main blade, said second auxiliary blade having a chord length such that its trailing edge is located a substantial distance from the trailing edge of said main blade so that fluid leaving the trailing edge of said second auxiliary blade during said third mode of flow will reattach to said main blade for an appreciable fraction of the time thereby forming a quasistable vortex in the region between said second auxiliary blade trailing edge and said main blade, the chord length of said auxiliary blade being of sutficient extent so that there is not an appreciable pressure difference between the region of the nose and the trailing edge of said second auxiliary blade during said third mode of flow, said second auxiliary blade being disposed so as to cooperate with said main blade and said first auxiliary blade to provide a smooth flow of fluid through said cascade during said first mode of flow.
11. A cascade as in claim 1 wherein x is approximately equal to or slightly greater than H, and c is greater than about one quarter 0 but less than one half 0.
\12. A turbine cascade comprising a series of relatively thin main fluid turning blades with smoothly curved camberlines such that the passage between two of said blades is of considerably contracting cross-sectional area, said passage being of substantially greater extent in the chordal direction of said main blades than is the minimum distance separating two of said main blades, a series of auxiliary blades, each of said auxiliary blades being located in said passage between two of said main blades, the camberline and location of said auxiliary blade being such that it cooperates with said main blades to allow the flow to progress smoothly through said passage around both sides of said auxiliary. blade when the flow approaches said turbine cascade at angles of attack near zero de grees, said auxiliary blade being of substantially shorter chord length than said main blades and said auxiliary blade being located substantially nearer to the convex side than to the concave side of said passage thereby providing a second smaller passage between said auxiliary blade and the convex side of said main blade passage, the camberline of said auxiliary blade being such that the cross-sectional area of said smaller passage also contracts in the same direction as said main blade passage, said auxiliary blade being disposed nearer .to the entrance than to the exit of said main blade passage, the nose of said auxiliary blade being located near the entrance of said passage rearwardly of the nose of the closer of said main blades with respect to the direction of the chord line of said closer main blade, so that the fluid approaching from the concave side of said closer main blade at large angles of attack greater than forty-five degrees will separate from the nose of said closer main blade and reattach near the nose of said auxiliary blade for at least a part of the time thereby forming a quasi-stable vortex in the region of separated flow without a substantial flow through said smaller passage for this mode of operation, the chord length of said auxiliary blade being of sufiicient extent to provide room lfOI at least a part of a second quasi-stable vortex to form in said small passage lbehind said first quasi-stable vortex, and the trailing edge of said auxiliary blade being located a substantial distance from the trailing edge of said closer main blade so that flow leaving the trailing edge of said auxiliary blade will reattach for a part of the time to the convex side of said closer main blade before leaving said oascade and only a small pressure difference will exist between the entrance and exit regions of said smaller passage thereby promoting the stability of the quasi-stable vortices and preventing flow through said smaller passage during said mode of operation that occurs at large angles of attack.
References Cited by the Examiner UNITED STATES PATENTS 1,684,567 9/1928 Wragg -465 1,744,709 1/1930 Moody. 2,166,823 7/ 1939 'Rosenlocher. 2,406,499 8/1946 Jandasek. 2,972,468 2/ 1961 Weber 25'3--31 FOREIGN PATENTS 811,104 l/1937 France.
973,599 9/ 1950 France.
'3 60,851 1 1/ 19 31 Great Britain.
630,747 10/ 1949 Great Britain.
67,5 25 3/ 1944 Norway.
SAMUEL LEVINE, Primary Examiner. JULIUS E. WEST, Examiner.