US3393893A

US3393893A - Blade construction for turbines

Info

Publication number: US3393893A
Application number: US525582A
Authority: US
Inventors: Niskanen Erkki Pietari
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-02-09
Filing date: 1966-02-07
Publication date: 1968-07-23
Anticipated expiration: 1985-07-23
Also published as: DE1551197A1

Description

July 23, 1968 E. P. NISKANEN 3,393,893

BLADE CONSTRUCTION FOR TURBIINES Filed Feb. 7, 1966 2 Sheets-Sheet 1 l '5m l f/// ll FIG. 1

July 23, 1968 E, P, NNNNNN EN 3,393,893

\ A Nw v wy S' United States 4Patent O 3,393,893 BLADE CONSTRUCTION FOR TURBINES Erkki Pietari Niskanen, Kissankellontie 13, Helsinki, Finland Filed Feb. 7, 1966, Ser. No. 525,582 Claims priority, application Sweden, Feb. 9, 1965,

,654/65 3 Claims. (Cl. 253-165) ABSTRACT OF THE DISCLOSURE A blade construction for a turbine wherein annular arrays of blades on a rotor wheel, which are directed inwardly towards the axis of rotation of the wheel, are each secured at their inner ends to a common ring which is received in a groove of another wheel having radially outwards arrays of -blades which are interdigitated with the blades of the first wheel, the outer ends of the inwardly directed blades being slidably received in the associated wheel for radial movement.

The present invention relates to a blade construction for turbines especially for axial iiow turbines with rotor wheels rotating in opposite directions and provided with rings of blade.

In steam and gas turbines of this kind, in which two turbine rotors rotate inside one another forming axial iiow channels lfor the power and are provided with rings of blade which protrude into these flow channels and are alternatively directed inwards and outwards, the blades of such inwardly directed rings become subject to a certain bucking action due to the centrifugal force of the rotating rotor wheels, because the inwardly directed blades in question are supported mainly at their radially outer ends by the respective rotor wheels. It is known to support the blades of such inwardly directed -blade rings at their radially inner ends by means of relatively thin shroud rings, which, however, cannot receive the strains acting on the blades. Thus the buckling action mentioned above irnposes certain restrictions on the blades as far as suitable shape, dimensions and working conditions are concerned.

The object of the present invention is to eliminate this disadvantage and the arrangement according to the invention is mainly characterized by the fact that the blades in each blade ring, which extends towards the axis of rotation, are radially slidably joined at their outer ends with the rotor wheel body supporting said blade ring, and

radially tixedly joined at their inner ends with a support ring, which is common for all blades of said blade ring and is dimensioned so that the entire radial strain, to which the blades are subject due to centrifugal force, is received at the inner ends of the blades by means of the support ring.

By supporting those blades, which are directed inwardly towards the axis of rotation, at their radially inner ends, it is achieved that the strain, to which the blades are subject because of the centrifugal force, is received entirely at the inner ends of the blades by means of the support ring, thus effectively eliminating the buckling strain acting on the blades. The torque produced in the blades by the power medium is transmitted in the usual way by the blades to the rtoor wheel body, to which the blades are attached radially slidably at their opposite outer ends in relation to the support ring.

Owing to the support ring according to the present invention, the rotor wheel body will, to some extent, be relieved of strains and its rnass can be reduced in view of the strain, which now according to the invention is received by the support ring. In this case the mass of the support ring can, however, be made less than the mass by lCC which the blade wheel body can be reduced by means of the support ring, because the support ring is at a lesser radial distance from the axis of rotation than the rotor wheel body, and the support ring is consequently subject to less centrifugal strain. By the blade construction according to the invention there is thus achieved not only an elimination of the blade buckling risk, but also the considerable advantage that the total mass of the rotor wheel bodies and the support rings is less than the mass of the rotor wheel bodies in conventional turbines, while in addition the diameter of the turbines can -be reduced.

When applying the present invention to a turbine, where the rotor wheel bodies are composed of a number of ring shaped sections, which are joined axially one behind the other and which support the respective blade rings, it is suitable to provide for each supporting ring a circumferential groove in the interplane between two rotor wheel body sections, which groove encloses the respective support ring with a certain clearance. The mounting of the rotor wheel bodies can now be effected by arranging the various sections of the two rotor wheel bodies one by one axially behind each other and by joining adjacent sections belonging to the same rotor wheel body with each other.

A more detailed description of the invention is given below with reference to the attached drawing, where FIG. 1 is an axial cross sectional view of one embodiment of a turbine provided with a blade construction according to the invention,

FIG. 2 is a cross sectional view taken along line II-II in FIG. 1 and FIG. 3 is a cross sectional view of a support ring according to another embodiment of the invention.

In the drawing only an outline of the turbine construction has been given, and turbine parts which are unimportant for an understanding of the invention have been left out.

The turbine comprises two co-axially arranged shafts 1 and 2, which rotate in opposite directions and each support a rotor wheel 3 and 4, which are arranged with their

blade supporting bodies

31, 41 and 42 interengaged to form axial ring shaped

flow passages

5 and 6. The bodies of the rotor wheels are provided with annular arrays or rings of blades which alternately protrude into said passages from both rotor wheels in interdigitating fashion. The body 31 of one rotor wheel 3 is fitted with a ring of blades 32, in which the blades extend radially inwardly toward the axis of rotation, and a ring of blades 33, in which the blades extend radially outwardly. The body of the other rotor wheel is fitted with a ring of blades 43, in which the -blades extending radially outwardly and the body part 42 is fitted with a ring of blades 44, in which the blades extend radially inwardly. A steam inlet is designated by reference numeral 7 and steam passes from the inlet 7 through openings 8 in the rotor wheel 3 into a common inner space 9 of the rotor wheels and further on through channels 10 in the rotor wheel 3, the flow passage 5, reversing channels 11 in the rotor wheel 4 and finally through the ow passage 6.

In accordance with the present invention, the blades of each blade ring, which extend radially inwardly towards the axis of rotation, are radially xedly joined at their inner ends with a support yring and at their outer ends are radially slidalbly joined with the rotor wheel body supporting said blades. Therefore, the blades of the blade ring 32 are, as shown in FIG. 2, provided at their inner ends with fastening means 36, which are radially Iixedly mounted in a support ring 34, and at their outer ends with fastening means 37, which are radially slida-bly mounted in the body 31 of the rotor wheel 3. The rblade-s of the blade ring 44 are similarly joined with the support 3 rings 45 and the -body 42. The support rings are co-axial with the turbine shafts 1 and 2 `and dimensioned so that the entire radial strain, to which the blades 32, 44 are subject due to the centrifugal force produced by the rotation of the rotor wheel, is resisted by the support rings 34 and 45, respectively, so that the blades 32, 44 do not exert any radial forces, but only peripheral torque on the

bodies

31 and 42 respectively. In the inner body 41 of the rotor wheel 4, peripheral grooves 46 have been provided exactly in line with the support rings 34, and in the body 31 of the other rotor wheel, peripheral grooves 35 have been provided for the support rings 45, which grooves with a certain clearance enclose the respective support rings in such a manner that the support rings do not obstruct the axially evenly diverging shape of the

flow passages

5 and 6 in the direction of the ow.

As appears from FIG. 1, the

bodies

31, 41 and 42 of the rotor wheel bodies are composed of separate rings shaped

sections

31', 41 and 42, the interplane of they sections being substantially parallel to each other and perpendicular to the axes of rotation of the turbines. In each case the peripheral grooves 35, 46 have been arranged exactly in line with the interface between two blade wheel sections so that the two sections together limit the peripheral groove. When using a sectional construction of this kind, the mounting of the rotor wheels can be effected by arranging the various sections of the rotor wheel bodies one by one alternately and axially behind each other and by joining adjacent sections belonging to one and the same rotor wheel body with each other and With the respective rotor wheel.

A turbine which has been provided with a blade construction according to the invention, operates in a manner, which is in itself previously known, but at the same time it has the advantages indicated in the preamble of the specification, as compared with conventional blade constructions.

The drawing and the corresponding part of the specication are only intended to illustrate the idea of the invention. The details of the blade construction according to the invention may vary considerably within the scope of the patent claims. Thus the support rings can be shaped in various ways, as has been shown by way of example in FIG. 3.

What I claim is:

1. A turbine comprising a pair of shafts arranged coaxially for rotation in opposite directions about a common axis, a rotor wheel on each shaft rotatable therewith, said wheels including respective axially spaced arrays of blades arranged around said axis of rotation, the blades on one lwheel extending radially inwards towards said axis and the blades of the other wheel extending radially outwards away from said axis, the blades of said wheels alternating axially and being interdigitated, a support ring for each of the arrays of blades which extends radially inwards, each said support ring being mounted coaxially with said shafts and being connected to the inner ends of all of the blades of the associated array in radially iixed relation, the outer ends of the latter array of blades being slidably mounted for radial movement in the associated wheel, each support ring being dimensioned so that the entire radial force applied to the blades by centrifugal force is resisted :by the ring at the inner ends of the blades.

2. A turbine as claimed in claim 1, wherein each wheel has arrays of blades which respectively extend radially inwards and outwards.

3. A turbine as claimed in claim 1, wherein each rotor wheel comprises a plurality of annular sections joined together in axial relation and supporting Irespective arrays of blades, the annular sections which carry the radially outwardly extending blades having annular peripheral grooves -between adjacent arrays of blades, which grooves are aligned with the arrays of blades extending `radially inwards, said support rings being accommodated in said grooves with slight clearance.

References Cited UNITED STATES PATENTS 824,449 6/1906 Stuart 253--71 X 2,530,908 11/1950 Ray. 2,838,275 6/1958 Harris et al.

FOREIGN PATENTS 564,639 6/1957 Italy.

EVERETTE A. POWELL, JR., Primary Examiner.