US2047501A - Steam or gas turbine - Google Patents

Description

July 14, 1936 F. A. WETTSTEIN 2,047,501 I STEAM OR GAS TURBINE Filed Apfil 24, 1955 4 Sheets-Shegt 1 INVENTOR 4.7%? Mme/Mm.

BY I ATTORNEYS.

July 14, 1936. F. A. WETTSTEIN STEAM OR GAS TURBINE Filed April 24, 1935 4 Sheets-Sheet, 2

INVENTOR ATTORNEYS July 14, 1936. F. A. WEITTSTEIN 2 4 STEAM OR GAS TURBINE Filed April 24, 1955 4 Sheets-Sheet s INVENTOR 0% Wwm.

BY WW;W%ZQZZEW.

ATTORNEYS.

July 14, 1936.

F. A. WETTSTEIN STEAM OR GAS TURBINE.

Filed April 24, 1935 4 Shee'ts-Sheet 4 3 ;.25.

A'rroRNEYS Patented July 14, 1936 UNITED STATES PATENT QFFICE assignor to Aktiebolaget Spontan, Stockholm,

Sweden, a corporation of Sweden Application April 24, 1935, Serial No. 18,051 In Germany May 3, 1934 21 Claims. (01. 25369) The present invention relates to steam and gas turbines and. has particular relation to an improved construction for the last rings or rows of moving blades of :such turbines. I

It is well known that the performance of gas or steam turbines is largely determined by the characteristics of the last blade rows, especially by the peripheral velocity and fluid outlet area of the very last moving blade row. The U. S. Nos. 1,897,172 and 1,942,608, disclose a method of constructing mov-. ing bladerows with greater peripheral velocities and outlet areas than were theretofore possible.

This. result is attained by making the moving blades of relatively thin sheet metal strips, formed along centrifugal catenary curves, and securing the ends thereof to axially separated annular blade carrier rings which, in turn, are interconnected through the medium of a framework. In this way, an appreciably lighter blade. construction is obtained which makes it possible to operate at correspondingly higher peripheral velocities andwith greater outlet areas. However, the peripheral velocity and size of these outlet areas are limited by the load or stress which the blade carrier rings can safely withstand as well as-by the permissible load on the framework interconnecting-the blade rings.

It is therefore one of the objects of the present invention to remove this limitation and to provide a moving blade row of novel construction wherein the loads or stresses set up due to cen-' trifugal force may be safely taken up even though the size and peripheral velocity of the blades'and.

their supporting structure are increased'b'eyond present limits. Another object is to provide a turbine rotor with new and structurally improved means for supporting and interconnecting the blade carrier rings. i

A further object is to provide a novel supporting structure for the last row of moving'blades of a steam or gas turbine which structure is lighter and stronger than those hitherto known and cooperates with the preceding portion or stage of the turbine in a novel manner for the supply of the motive fluid to'said last row of blades.

Still another object is to providenovelly constructed means forsecurely attaching the ends of arched turbine blades to their carrier rings which means are both light in weight and sufllciently strong to anchor the blades ends against displacement under the relatively powerful centrifugal forces developed'at high speeds of rota- The invention is characterized essentially by the fact that bothblade carrier rings are supported by radially or substantially radially ex= tending members, at least one of which assumes the form of an annular ring made up of struts, spokes or the like, between which the driving medium flows to the blades. The carrier ring supporting members are then connected together by a drum or ring, or by the turbine shaft itself, the diameter of this connecting element being materially smaller than that of .the blade carrier rings. This form of construction makes it possible to take up appreciably greater centrifugal forces and permits the blade carrier rings as well as the blades themselves to be of greater diam- 15 eter and consequently-to attain greater peripheral speed, whereby at a given R; P. M. a correspondingly greater performance per turbine out- In the drawings, wherein like reference characters indicate like parts throughout the several views:

Fig. 1 is a longitudinal section through an axial flow turbine, the last moving blade row and outlet of which are constructed according to the 35 present invention.

I Fig. 2 is a cross section through the outlet casing of the same turbine, also showing a portion of.the outlet.

Fig. 3 is a section taken substantially along line 3 3 of Fig. 1.

Fig. 4 is a diagrammatic showing of a portion of the axial flow blade. construction. and of the supporting struts for the last blade row of the turbine illustrated in Fig. 1.

Fig. 5 is a partial longitudinal section through another form of turbine, showing the.--applica-' tion of the invention to a combined radial and axial flow turbine.

Fig; 6 is a side elevation of a turbine having two outlets connected to condensers laterally of the turbine. I

Fig. 7 is a longitudinal section through a double arranged I axial flow turbine with a common outlet or ex- 55 the present invention.

haust blade row constructed in accordance with Fig. 8 is a section taken substantially along line 8-8 of Fig. '7.

Fig. 9 is a fragmentary. section taken substantially along line 9-9 of Fig-11 through a portion of still another form of blade row'embodying the invention.

Fig. 10 is a modification of the construction shown in Fig. 9.

Fig. 11 is a partial longitudinal section taken substantially along line-i l--fi| of Figs. 9 and 10. Fig. 110. is an enlarged view of a portion of the structure of Fig. 11. i

Fig. 12 is a fragmentary section: taken subby showing the novel form of blade securing thereof are suitably secured means provided by the present invention.

Referring now to the embodiment illustrated in Figs. 1, 2, and 3, the invention is there shown in its application to an axial turbine. The steam enters the turbine through inlet 8 and impacts against a speed rotor'9 and then a large number of axial stages ill. I l are passageways for tapping steam for feed water preheating. Following the last axial moving blade row I2 a guide blade row i3 is provided. Insofar as the drawings relate to conventional turbine parts they should be understood without further description; the following description is therefore limited to the novel parts of the turbine constituting the present invention.

From guide blades l3 the steam flows, 'as indicated by arrows i4, through a ring of struts or spokes i5 in a substantially axial direction, and then radially through the last moving blade row consisting of arched or sheet metal blades l6. After leaving blades IS, the steam exhausts through the diffuser guide blade row H to the outlet i8. The arched blades iii of this modification, the form of which is shown in Figs. 1 and 2, are preferably made of relatively thin sheet metal, as of stainless steel, and the ends in a pair of blade carrier rings i5 and 20. Blade carrier ring 20 is supported by turbine disk M with which it is integral. Blade carrier ring IS, on the other hand, is supported by the struts or spokes i5 which, as shown in Fig. 3, form an annular ring through which the steam flows to blades l6 constituting the last moving blade row of the turbine. Struts IS, in turn, are carried by a disk 22 which, like disk, is concentric with the turbine shaft. Blade carrier ring [9, struts I5 and disk 22 are preferably integral with one another. Runner disks 2| and 22 are securely interconnected by means of a ring or drum on self -s'upporting blade carrier rings. The load or stress upon such self-supporting rotating rings,

as is well known, increases proportionately-with the square of the peripheral speed. .It'is' there;

equal to the outer diameter of the last blade row of the axial flow portion oi. the tur-, of a portion of anothertation of the self -supporting rings;

. made of a diameter as rotor operating at 23, the diameter of which is, as shown, materially less than the diamouter part of disk radial direction, I curvein continuation of that of blades l8, so that fore impossible to increase the size of these rings beyond a certain diameter without rendering them incapable of withstanding the stresses set carrier rings of the arched blades by means of radially or substantially radially arranged mem:

which is substantially moving bers, the outer diameter of bine-in the present specific instance blade carrier ring 20 is supported by a disk 2! and .blade' carrier ring i9 by a ring consisting of struts l5 and disk 22.

Since the centrifugal forces acting during roparts supporting the blade carrier rings cause the said parts to distend, the carrier ringswill also be distended to a corresponding extent,-whereby they are subjected to the same stresses as prevail in the radially extending supporting parts. In other words. the load created by centrifugal force is distributed and divided between the blade carrier rings and their radiallyextending supporting elements, the major portions thereof being' absorbed by the latter elements. The stresses in,the blade attachment rings cantherefore bemaintained lower than in by the same token, it is possible to provide blade carrier rings of appreciably" greater diameter without setting up stresses greater thanthose that can be safely carried. Moreover, since. the arched blades i6 are made of relatively thin sheet metal, 1. e., they' are-very light in comparison with conventional turbine blades, the blade carrier rings may be larg'eas the outer diameter of the last moving blade row of normal highperforrhance axial turbines.

The light radial fiow wheel according to the present invention, also makes it possible to add another low pressure rotor at the outlet side of the present-day conventional limit turbines of the axial type, said eralspeed and employing a greater outlet area than was heretofore possible with known outlet blade rows. As a result of the-higher peripheral speed of the last blade row. a relatively greater heat drop may be produced therein, so that the nextio the last rotor may operate at an appreciably higher pressure and with a correspondingly smaller volume of steam. By the addition of a blade row constructed in accordance with the present. invention. it thus becomes possible to increase the maximum performance of a turbine at a given R. P. M. to fromthrce to four-fold the value heretofore attainable.- .The magnitude of.

-- the heat drop in the last rotor presents the further advantage that the moisture in the steam does not attain a high value until expansion takes place in the last blade row, whereby danger ofblade erosion is correspondingly minimized.

, As shown in Fig. l, supporting struts l5 and the 2| are inclined toward the or .are formed along a catenary construction of an arched blade,

an appreciably higher periphperipheral speed it. By a composition of the inlet upon rotation there is no bending stress but only a tensile stress in these parts, notwithstanding the axial force exerted by the arched blades.

Struts l are also preferably tapered outwardly (that is, in a radial direction) and of such cross section at right angles to their length as to offer a minimum of resistance to the flow of the steam or other driving medium as it passes from fixed guide blades I3 to moving blades i5. Fig. 4 shows a preferred embodiment of blades i2 of the last axial blade row, as well as of guide blades l3 and struts l5. As indicated by the velocity diagrams of Fig. 4, the driving mediumleaves the moving blades l2 at the relative outlet velocity wz. By a composition of the relative outlet velocity we with the peripheral velocity u of blades l2 there is obtained the absolute outlet velocity 02. This velocity is converted in the fixed guide blades l3, preferably without expansion, into inlet velocity or into the ring of struts l5 which also rotates at velocity 01 with the peripheral velocity u, there is obtained the relative inlet velocity The guide blades l3 are preferably constructed in such manner that the relative inlet velocity 101 into the rotating strut ring I5 is axially directed. The guide blades can be twisted in known manner so that the same inlet angle of the driving medium is produced along the entire length of the struts independently of the variable peripheral velocity of the latter and of the variable radius thereof. 01 course, if desired, struts may be disposed at a certain angle relative to theaxial direction also. However, for constructional reasons, the embodiment of struts with an axially extending cross'section as shown in Fig. 4 is to be preferred.

The driving medium leaving the arched blades i5 is passed between housing walls 24 and 25 (Fig. l), which are formed as an annular diffuser.

Guide blades II, which are suitably secured in housing walls 24 and 25, are preferably so formed that they also act as a diffuser for the outgoing driving medium. This results, upon decreasing speed, in a compression of the outgoing driving medium, thus reducing the outlet loss. The guide blade ring I I offers the further advantage that,

when the turbine is idling, the driving medium surrounding blades l6 practically forms a ring of steam or gas which rotates with blades l6, whereby turbulent currents within the exhaust casing are avoided and power consumption during idling is reduced to a minimum; also, this construction protects the blades l5 from the dangerous eddy currents which otherwise arise, particularly if the vacuum is destroyed.

Outlet ll of the turbine preferably assumes the form of a spiral casing 26, whereby current losses between the last rotor and the condenser are reduced to a minimum and whereby a diffuser action, and thus a consequent reduction in outlet losses, may be obtained. Spiral casing 25 is preferably made of relatively thin sheet metal. In order that the casing may be rigid, however, the diffuser casing walls 24 and 25 which form the outlet from blades ii are connected together by means of a ring of streamlined struts 21. As shown in Fig. 2, struts 21 are preferably made in the form of an annular framework, whereby great solidity as well as the requisite rigidity of the turbine casing is obtained. The direction of flow' of the driving medium through the blades IS, the diifuser guide blades l1 and the spiral casing I8 is shown by arrow 28 in Fig. 3, arrow 19 indicating the direction of rotation of blades l3.

Another embodiment of the spiral casing is shown in Fig. 6. In this instance, the turbine 29 is provided with two laterally arranged condensers 30 and 3|, the spiral casing being correspondingly subdivided into two parts 32 and 33. -As shown by way of example in Fig. 5, the blade row according to the present invention may also advantageously be used as the last rotor either for radial flow turbines or for combined radial and axial fiow turbines. In the embodiment of Fig. 5, the driving medium first passesv through a radial turbine consisting of the moving blade rows 34 and the guide blade rings 35, and then through two stages of an axial turbine consistinr. of guide blades- 35 and moving blades 37. From the last row of moving blades 31 the driv- 1:, ing medium passes through a radial flow low pressurestage constructed in accordance with the present invention-that is, through guide'blades 38, struts 39 and arched blades 40 into the outlet casing, the latter being not shown on the drawing for the sake of clearness. In this embodiment, the turbine rotor is supported only at the right end as viewed in the drawings, i.'e., fioatingfy. As "another exemplary embodiment of the pres- 5 entinvention, Figs. '7 and 8 show the application thereof to a double axial flow low pressure turbine having a common outlet. In this case, the driving medium fiows first in opposite directions through the two axial blade systems 4| and 30 42, the quantities thereof leaving said systems then combining and flowing through the arched blades 43 into outlet casing 44. Arched blades 43 are suitably secured to rings 45 and 46. In

ments, in this case both bladecarrier rings 45 and 46 are supported by struts 41 and 48 which, in turn, are secured to or formed integrally with disks 49 and 50. These disks are mounted on the turbine 'shaft 5i together with the rotors of the axial stages. The diffuser. blades of this embodiment are subdivided by means of a separator ring 54 into two diffuser blade rows 52 and 53, the blades of-which are inclinedv slightly from ring 54 toward the turbine axis. This construction offers the advantage, among others, that the water of condensation thrown from the outermost points of arched blades 43 does not strike the diffuser blades but instead is collected on the relatively thick ring 54. The fact that the diftends to cause whatever condensate is deposited on these blades to run toward the ends thereof, thereby preventing it from dropping down onto the arched blades 43. As shown in Fig. 8, outlet casing 44 in this modification does not assume the form of a'spirai but it is symmetrical in form. Accordingly, the diffuser blades 52 and 53 are preferably so formed that the driving medium leaves them in a radial direction.

Figs. 9, 10, and 11 show another modification of the invention, on an enlarged scale. In this embodiment, ring 55 which carries one end of each of the blades assumes the form of a polygon, the number of sides of which corresponds to the number of arched blades. This construction makes it' possible for the bases of the arched blades, aswell as the blade attachment, to be rectilinear. Accordingly, each blade end is provided with an enlargement which may be inserted into one of the straight dovetail-shaped grooves provided obliquely on the periphery of the carrier ring 55, as shown on an enlarged scale in Fig. 11a. As hereinbefore described, the carrier ring 55 is supported by struts 56 and disk 51.

,groove 63. arcuatein form and enlarged in cross section Due to the large centrifugal forces which -arise during-rotation of the turbine rotor, the blades produce a bending stress in the blade carrier ring 55, whereby ring 55, which acts as a supporting beam, is bent between e h pair of struts 58. In order to retain this bending force within allowable limits, it is necessary in certain cases to provide a large number of struts 56. In such cases, as shown in Fig. 10,'it may'be advantageous to provide struts 58 which are subdivided at the outer part thereof. into two or more branches 59 and 60. Arrow Si in Fig. 10 indtcatesl the path ofthe driving medium relative to the rotating blade wheel.

In the exemplary embodiment shown in Figs. 12 and 13, the blade carrier ring 62 is circular and is provided with a circular dovetail-shaped blade The blade bases are correspondingly similarly to the showing of Fig. 11a. In this modification, drum 66 which interconnects supporting disks 64 and 65, is carried by a disk 61.

Figs. 14 and 15 show another modification wherein the arched blades 68 are again carried by a circular ring 69. In contrast to the foregoing construction, however, struts 10 which support carrier ring 69 are each made separate and are individually securable by separate connections to both ring 69 and disk H. In the form shown, each end of each strut 10 is bifurcatedor forked, the inside surfaces of each fork being grooved to form sawtooth-shaped threads corresponding to similar threads 12 formed on the inner surface of carrier ring 69 and on the outer edge of disk ii. In assembling a rotor of this construction, the forked ends of struts 10, which are spread apart sufliciently to allow passage over the threaded portions 12, are placed over said threads and are then brought into rigid clamping engagement therewith, as by a rolling operation. In most cases, however, it is advantageous, as shown in the previous modifications, to make the blade carrier ring, struts and disk integral, wherebygreater strength and less weight result.

At high peripheral speeds, such as are employed with a turbine rotor constructed according to the present invention, powerful centrifugal forces are produced. nothwithstanding the relatively light character of the arched blades, and it is therefore important that the attachment of the blades in thecarrier rings be particularly secure and also that the attachment and the blade carrier ring be as light as possible.

Fig. 16 shows a construction which is particu larly well suited for this purpose. The enlarged blade base I3 is provided with arcuate sawtoothshapedthreads or members 14 which fit corresponding recesses formedin the walls of the usual blade base receiving groove of the blade carrier ring 15, on the one hand-andin an arcuate filler member 16, on the other. also provided with sawtooth-shaped threads 11, whereby it is connected to the blade carrier ring ll.

of the carrier ring in such position that its threads ll engage therecesses formed in one side wall in the peripheral direction until it comes into interlocking toothedengagement with the threads Filler member 1'6 is The .blades are assembled with the carrier ring by first inserting ablade base 13 in the groove vl4 of the blade base.

ring groove at its narrowest point so as to effectively prevent the blade from being pulled out of 5 the groove by centrifugal force. As shown in Fig. 12, an intermediate space 18 is provided between each two successive blades in order that the last blade may be inserted. This is accomplished by moving all the blades together as closely'as possible until there is a suiiiciently large intermediate space provided into which the filler member for the last blade may be inserted. Since the described blade attachment produces only relatively small bending stresses on thehalves 15 of the blade carrier ring encompassing the blade base, the blade carrier ring may be made relatively thin and light, which is of great importance at its high peripheral speed.

It will be obvious that the present invention is 20 not limited in its scope to the particular constructions described and illustrated, but is capable of a variety of mechanical embodiments. For example, it is obvious that, in the construction shown in Fig. 16, the plurality of threads and recesses formed on the blade base and filler member and in the walls of the carrier ring groove may be replaced by single shoulders and recesses,

or equivalent means operating upon an interlocking or wedging principle. Various other changes, which will now become apparent to those skilled in the art, may be made in the form, details of construction and arrangement of the parts of the disclosed embodiments without: departing from the spirit of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a steam or gas turbine of the type including a radial flow stage comprisinga pair of axially spaced rotatable blade carrier rings to which are secured the ends of aplurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for su porting said bladecarrie'r' rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in, pianes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacingof said carrier rings and each being secured to one of said rings at its outer periphery, at least one 'of said members having openings formed therein through which the turbine driving medium may be supplied to saidblades.

2. ,In asteam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier'rings to which 0 are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members lying in planes substantially perpendicular to the rotor shaft of the turbine and axially spaced by an amount substantially equal to the axial spacing of said carrier rings, each of said members ineluding a disk concentric with and connected to the turbine shaft to the outer periphery of which is secured one of said blade carrier rings, at least one of said members having openings formed thereinthrough which the turbine driving medium may be supplied to said blades.

3. In a steam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved substantially equal to the axialspacing of saidcarrier rings and each being secured to one of said rings, at least one of said members consisting of a central disk portion from the periphery of which radially extend a plurality of circumferentially spaced struts, the'outer ends of said struts being secured to one of said carrier rings and the spaces between said struts serving as openings through which the turbine driving me-' dium'may be supplied to said blades.

eluding a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings andeach being secured to one of said rings, at least one of said members consisting of a central disk por-- tion from theperiphery of which radially extend a plurality of circumferentially spaced struts, the outer ends of said struts being secured to one of said carrier rings and the spaces between said struts serving as openings through which the turbine driving medium may be supplied to said blada, said disk portion, struts and carrier ring being made in. one piece so as to provide an integrally formed structure of increased strength.

5. In a steam orgas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each oi; ;whi'ch is curved outwardly from the turbine rotor shaft ina 'centrifugalcatenary curve, means for supporting said blade carrier rings and blades andfor absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially-equal to the axial spacing of said carrier rings and each being secured to one of said rings, one of said members consisting of a central disk portion from the periphery of which radially extend a plurality of circumferentially spaced struts, the outer ends of said struts being secured to one of said carrier rings and the spaces between said struts serving as openings'through which the turbine driving medium may be supplied to said blades, the other member consisting of a solid disk.

for absorbing the stresses set up therein by centurbine. 4. In a steam or gas turbine of the type inv of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and trifugal force comprisinga pair of members lyv ing in planes substantially perpendicular to the rotor shaft of the turbine and axially spaced by an amount substantially equal to' the axial spacing of said carrier rings, each of saidmembers consisting of a disk concentric with and connected to the turbine shaft and a plurality of circumferentially spaced struts extending radially from the periphery of said disk, the outer endsof the struts 'of each member being secured to one of said blade carrier rings and the spaces between said struts serving as openings through which the turbine driving medium may be supplied to said blades from the two axial flow portions of the 7. In a steam or gas turbine of the type includinga radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected tobut lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an'amount substantially equal to the axial spacing of said carrier rings and each being se- 0 cured to one of said rings at its outer periphery,

at least one of said members having openings formed therein through which the turbine drive ing medium may be supplied to said blades, the outer peripheral portion of each of said members adjacent the connection with its associated blade carrier ring being curved toward the other member along a substantially catenary curve similar to that of said blades. 8. In a steam or gas turbine of the type ineluding aradial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members con- -centric with and connected to but lying in planes 0 substantially Perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings, at least one of said'e5 members consisting of a central disk portion from the periphery of which radially extend a plurality of circumferentially spaced struts, said struts .belng tapered in the direction of their extension from said disk portion and having secured to 79' through which the turbine driving medium may cluding a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings'and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine; said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings, at least one of said members consisting of a central disk portion from the periphery of which radially extend a plurality of circumferentially spaced struts, the outer ends of said struts being bifurcated and secured to one of said carrier rings, the spaces between said struts serving as openings through which the turbine driving medium may be supplied to said blades.

10. In a steam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings, at least one of said members consisting of a central disk portion from the periphery of which radially extend a plurality of circumferentially spaced struts, the outer end of eachof said struts being subdivided into at least two branches-and the ends of said branches being secured to one of said carrier rings, the spaces between said struts serving as openings through which the turbine driving medium may be supplied to said blades.

11. A turbine blade supporting structure according to claim 3 wherein each of said struts is streamlined in the direction of flow of the turbine driving medium through the openings between said struts.

12. A turbine blade supporting structure according to claim 3 wherein each of said struts is provided with a cross section which is elongated in a direction parallel to the turbine shaft.

13. In a steam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings, at least one of said members consisting of a central disk portion, a plurality of circumferentially spaced struts extending radially outward from the periphery of said disk portion, and means for securing the opposite ends of each of said struts to said disk portion and one of said carrier rings, respectively, the spaces betweensaid struts serving as openings through which the turbine driving medium may be supplied to said blades.

14. In a steam or gas turbine of the type including a radial flow stage comprising'a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings, at least one of said members consisting of a central disk portion, sawtooth-shaped threads formed on the peripheral surface of said disk portion, a plurality of circumferentially spaced struts extending radially outward from the periphery of said disk portion, one end of each of said struts being bifurcated and having threads formed in the inner surfaces of said bifurcated portion corresponding to and interlocking with the threads on said disk portion, and means for securing the other end of each of said struts to one of said carrier rings, the spaces between said struts serving as openings through which the turbine driving medium may be supplied to said blades.

15. In a steam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings at its outer periphery, at least one of said members having openings formed therein through which the turbine driving medium may be supplied to said blades, and means for interconnecting said members at points intermediate their peripheries and their centers.

16. In a steam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings at its outer periphery, at least one of said members having openings formed therein through which'the turbine driving medium may be supplied to said blades, and means for interconnecting'said ,memberscomprising a cylindrical drum element coaxial withporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of members concentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine, said members being axially spaced by an amount substantially equal to, the axial spacing of said carrier rings and each being secured to one of said rings at its outer periphery,

at least one of said members having openings formed therein through which the turbine driving medium may be supplied to said blades, a disk parallel to and intermediate said members coaxial with said turbine shaft, and a substantially cylindrical drum element secured to the periphery of said disk and connected at its ends to said members, the diameter of said disk and drum element being less than that of said blade carrier rings.

18. In a steam or gas turbine of the type including a radial flow stage comprising a pair of axially spaced rotatable blade carrier rings to which are secured the ends of a plurality of relatively thin sheet metal blades each of which is curved outwardly from the turbine rotor shaft in a centrifugal catenary curve, means for supporting said blade carrier rings and blades and for absorbing the stresses set up therein by centrifugal force comprising a pair of membersconcentric with and connected to but lying in planes substantially perpendicular to the rotor shaft of the turbine,- said members being axially spaced by an amount substantially equal to the axial spacing of said carrier rings and each being secured to one of said rings, at least one of said members consisting of a central disk portion from the periphery of which radially extend a plurality of circumferentially spaced struts, the

said carrier rings and the spaces between said struts serving as openings through which the turbine driving medium may be supplied to said blades, and a plurality of stationary guide blades arranged adjacent the path of rotation of said struts for directing said, driving medium toward said openings.

19. In a 'rotbr for a steam or gas turbine, a central disk, a plurality of circumferentially spaced struts extending radially from the periphery (if said disk, and a blade carrier ring secured to the outer ends of said struts, said blade carrier ring including means for receiving and holding the ends of a plurality of turbine blades and the spaces between said struts serving as open-;

ings through which the turbine driving medium may be supplied to said blades.

20'. A rotor for a steam or gas turbine comprising a pair of axially spaced rotatable disks, a plurality of circumferentially spaced struts extending radially from the periphery of one of said disks, a blade carrier ring securedto the outer ends of said struts, a second blade carrier ring securedto the periphery of the other disk, and a plurality of relatively thin, arched sheet metal blades extending between said carrier rings and having their ends secured thereto, the spaces.

between said struts serving as openingsthrough which the turbine driving medium may be sup-" plied to said blades. i

21. A rotor for a steam or gas turbine comprising a pair ofraxially spaced rotatable disks,

, a plurality of circumferentially spaced struts extending radially from the periphery of one of said disks, a blade carrier ring secured to the outer ends of said struts, a second blade carrier secured to said disks, the diameter of said mem-- her beingsubstantially equal to the diameter of said strut supporting disk.

FRI'IZ ALEXANDER wn'rrs'mm.

' outer ends of'said struts being secured to one of ring secured to the periphery of the other disk,

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