US2573621A

US2573621A - Elastic fluid turbine

Info

Publication number: US2573621A
Application number: US733663A
Authority: US
Inventors: Sterland Ernest George
Original assignee: English Electric Co Ltd
Current assignee: English Electric Co Ltd
Priority date: 1946-03-21
Filing date: 1947-03-10
Publication date: 1951-10-30
Anticipated expiration: 1968-10-30
Also published as: CH265292A

Description

1951 E. G. STERLAND ELASTIC FLUID TURBINE Filed March 10, 1947 9M1 W 2? MM a, 6M MM FIG.

Patented Oct. 30, i951 ELASTIC FLUID TURBINE Ernest George Sterland, Cambridge, England, assignor to The English Electric Company Limited, London, England, a British company Application March 1 0, 1947, Serial No. 733,663 In Great Britain March 21, 1946 2 Claims (Cl. 253-59) The invention relates to elastic fluid (steam or gas) turbines and has the object of shortening the length of such'turbines required for a given number of stages.

It is known in the construction of the rotors of elastic fluid turbines to machine deep recesses between stages, so as to sub-divide the rotor into a number of discs each of which has one or more grooves machined into its periphery into which the complementarily profiled feet'of blades may be inserted, which discs are integral with a common central or hub-like portion of the body. However, the gaps between the stages increase the length of the rotor and consequently of the turbine as a whole.

It has also been suggested in the construction of the rotors of such turbines to divide the rotor into disc-like portions by means of deep annular recesses, the opposing faces of such discs being suitably grooved near their periphery so that the complementarily profiled feet of blades may be inserted. However, for turbines running at relatively high speeds of revolution in which high stresses are produced in the disc-shaped portions, it is necessary in order to reduce these stresses to a minimum to shape the faces of the discs in such a way that the axial width of the discs near the bottom of the annular recess is considerably greater than near their periphery. This results in a large axial length for each stage of blading, and thus an increased length of the rotor and consequently of th turbine as a whole.

It has further been suggested in built-up rotors to arrange the rows of blades between the individual discs or rings of the rotor assembly, the lowest pressure stage disc only carrying a row of blades in addition to the interdisc blades of the previous stages.

In order to overcome the disadvantages of these previously suggested methods of construction, the following improvement has been made in the first method of construction described above, in which according to the invention deep annular recesses are machined between stages so as to sub-divide the rotor into a number of discs, each integral with the common central or hub-like portion of the body, and having one or more grooves machined in its periphery into which the complementarily profiled feet of rows of blades may be inserted. Circular grooves are machined in the opposing surfaces of at least some of the discs near their circumferences, and additional rows of blades, with their roots profiled complementarily to said grooves in order to secure fixing, are inserted into the said grooves between such adjacent discs, th rotor blades on the individual discs being arranged substantially on the centre planes of discs engaged by rotor blades inserted in the profiles between adjacent discs on both sides, and being arranged off-set from the centre planes of discs engaged on one side only by rotor blades inserted into the circumferential grooves of adjacent discs, the off-set being away from the inserted blades.

In order that it may be more readily understood, the invention is illustrated by way of example in the accompanying drawing, of which:

Fig. 1 is a part of an elevation in section of a turbine according to the invention, and

Fig. 2 is a detail on a larger scale.

The solid rotor I has a bore 2 for internal inspection of the forging and is sub-divided into

discs

3, 4, 5, 6, by deep annular recesses I, 8, 9, machined into the rotor body. Thus these discs are integral with the solid centre portion adjacent the bore 2 of the rotor I. The blades of four stages ll, I2, I4 and I6 of the turbine are arranged in the usual Way on the

discs

3, 4, 5 and 6 respectively, and additional rows of blades I3 and I 5 are inserted into the gaps between

discs

4, 5 and 5, 6 respectively. The turbine stator 20 and the guide vanes 2I to 26 for the turbine stages II to I6 are indicated diagrammatically for completeness but do not in themselves differ from the usual design of such components.

As will be seen more clearly from Fig. 2, serrations Il are arranged in the roots of the blades, such as 15, and complementary serrations I8 in the opposite surfaces of adjacent discs, such as 5 and 6, near their circumference. The serrations I1 and I8 are interlocked and transmit forces from the turbine blades to the respective discs. Alternatively, the roots of the blades I5 or I3 may be for example T-shaped as shown for the roots of blades I6, and engage appropriately shaped grooves on the adjacent discs instead of the serrations shown.

As will be seen from Fig, 1, th turbine blades I2 and I6 are offset from the centre planes of their respective discs 4 and 6 towards the sides away from the adjacent row of additional inserted blades I3, I5 respectively. This is done in order to balance the forces transmitted from the blades I3 and E5 to one side of each of the respective discs 4, 6. However, in a disc such as 5, having additional blades attached on both sides, the blades such as I4 are arranged substantially on the centre line.

The number of inserted stages is shown to be two in Fig. 1 but obviously as many such stages can be arranged as required by the overall number of stages and the particular design of the turbine. In the embodiment shown no such additional blades have been inserted between the stages marked H and I2 in order that the stresses in the disc 3 which carries the blades II and whicla fis expose dag higl temperatures, be kept as ,lQw as. possible.) However,' if such considerations do not prevail, a row of additional blades could be arranged between stages H and [2 as well. n.i,-. .M.

What I claim as my invention and desire to secure by LettersPatentisg i 1. An elastic fluid turbinegcomrising; a casing, stator blades arranged in said casing; a rotor T said rows of rotor blades between adjacent discs,

the rotor blades on the individual discs being 2 a'rrang'd substantially on the centre planes of g I dl scs engaged by rotor blades inserted in the profil consisting of a central body andudisc s integral with the said central body, said disc sloeing fgir; cumferentially grooved on opposing sides near the circumference thereof, rows of rotor -blades blades "between adjacent discs on both sides, and

foif set from the; centre planes of discs engaged onr one side only by, rotor blades inserted into the lsaid. circumferential grooves of adjacent discs,

theoiT-set being away from the said inserted