US1745429A - Axial-flow steam turbine - Google Patents

Description

Feb. 4, 1930. A. LYSHOLM AXIAL FLOW STEAM TURBINE Filed May 3, 1928 Patented 4, 1930 v IU-hl I TED STATE-S PATENT OFFICE srnoms ANGTURBIN, F STOCKHOLM SWEDEN ALF'LY SHOLM, OF STOCKHOLM, SWEDEN, ASSIGIfTOR TO AKTIEBOLAGET 'IJUNG- SWEDEN, A JOINT-STOCK COMPANY OF axmrrrnow STEAM TURBINE Application filed May 3, 1928, Serial No. 274,907, and in Sweden May 11, 1927.

Heretofore, turbines have been so constructed that an outer cap surroundsan inner guide-blade-carrying cap, and that the space between these caps constitutes the outlet of the turbines, or is in connection with such outlet. 7

In such constructions, the inner cap and the outer cap have been made integral, but in such tial joints, it has a manner that the said united caps would be axially divided into two halves surrounding the inner rotating parts of the turbine, which halves have been held together by means of bolts. If the driving medium is admitted to such a turbine, the pressure acting within the turbine tends to force the connecting flanges apart and cause a leak. To obviate this and cause the steam pressure to bring about automatic ti htening of the axial parbeen previously pro osed to conduct the driving medium throng the turbine in such a manner that steam of high pressure would enter the space between the mner and the outer cap, which caps are con- 7 structed as separate parts, In order to avoid leaky joints the outer up has been part1 constructed so as 'to be axially undivide Such constructions, however, are not suitable in turbines operating with a back pressure and under very high pressures, for mstance 1150 at., since the exhaust steam will in this 1 case still have a very high pressure, for instance 75 at. Even steam of this, pressure will force the connecting flanges apart and cause open joints, if such steam is conducted through axially divided casings, caps or steam conduits.

The present invention refers to turbines of b drawing showing an axial cross section through a turbine according to the invention.

In the drawing, 1 designates the shaft of the turbine, which shaft is formed at its one end into a pinion 2 and at its other end into an attaching device 3 for the turbine rotor 4. The shaft 1 terminates in an inner hollow Epace and an outer conical portion, as at 3,

tting to a correspondingly shaped portion of the turbine rotor 4. In certain places between the conical surfaces, conical pins 5 are forced into correspondin holes, which pins are retained by means 0 the central bolt 6. The turbine rotor 4 is formed into or connected with turbine disks 7, 8, 9 and 10 adapted to carr blades 11, 12, 13 and 14. Fitted between t ese turbine disks are guideblade-carrying rings 15, 16 and 17, which are shaped in connection with or united with an inner ca 18. This cap 18 is axiall divided in the 'p ane of the paper, as are t e guideblade-carrying rings 15, 16 and 17. The two halves of the cap 18 are ke t together by means ofi bolts, as at 19, 20 an 21. Between the turbine rotor 4, or the parts connected therewith, and the inner cap 18, or the parts connected therewith, packings have been provided inknown manner by means of thin wearing edges, as will appear from the drawing. I

The inner' divided turbine cap 18 is attached to a ring 23 by means of bo ts 22. This ring 23 is secured, in turn by means of bolts '24, to an undivided outer cap 25 surroundin the whole turbine, said cap 25 being secure a ring 28 fixedly connected therewith, in such a manner that facilities are provided for the expansions of said cap by reason of tensions caused by heat. During the expansion of the turbine .cap, the same will slide on the studbolts 26 so as to reduce the play 29 between the cap 25 and the ring 28. In this case, too, the frame 27 constitutes a casing surrounding the toothed gearing with which the pinion 2cooperates, and also carries one of the bearings 30 of the turbine shaft.

The supply conduit 31 for the driving medium is arranged in conjunction with the y means of stud-bolts 26 to a frame 27 or to 'ring 23. These parts form together the head piece of the turbine. The supply conduit 31 is formed with a flange 32, and is attached to the ring 23 by means of bolts provided between the bolts 22. Thus the supply conduit 31 of the turbine is arranged centrally about the geometrical axis of the turbine, and does not cause any oblique forces detrimental to the turbine.

The driving medium or steam passes through the supply conduit. 31 and through the openings or nozzles 33, whereupon said driving medium or steam flows through the blades 11, 12, 13 and 14 of the turbine and through the guide blades provided therebetween, while delivering energy. The turbine described is intended to operate at an initial pressure of 150 kilograms per square centimeter and at a speed of rotation of 12000 revolutions per minute. Of this pressure, the turbine will transfer into kinetic energy a fall of pressure of about 7 5 kilograms per square centimeter, for which reason an approximate pressure of 75 kilograms per square centimeter will prevail, during the running of the turbine, in the space 34 between the outer cap 25 and the inner cap 18, whereas the average steam pressure within the inner cap 18 will be about 115 kilograms per square centimeter. Inasmuch as the difference in pressure between the space inside ,the inner cap 18 and the space 34 between the caps is smaller than the diflerence in pressure between the space 34 and the space surrounding the outer cap, the strains Willbe greater on the outer cap than on the inner one: Thus the advantage is obtained according'tothe invention, in regard to a steam-tight fit, that steam of lower pressure is conducted between theinner divided and'the outer axially undivided eap surrounded by atmospheric pressure, whereas steam of a higher pressure is conducted through the. inner axially divided cap surrounded by exhaust steam. If the pressure, within theturbine, of the driving medium would then force axial connecting flanges apart and cause them to become untight, this will have no influence but that small quantities of steam will leak out into the space between the caps. The loss produced 'hereby will have a minimum value when the steam present in this space is then used for other useful purposes. l

The steam entering the turbine through the nozzles 33 will obviously fill the space in front of the turbine disk 7 and bring about an axial pressure, counted in the direction of flow of the steam. To counteract this pressure, a balancing plunger 37 is arranged, whichis'fixedly arranged on the turbine rotor 4 and provided in known manner with tightening members 38 directed toward stationary members in the steam inlet 31. Moreover, the turbine is provided, in addition to the plunger 37 with the tightening members 38 the'inner cap.

pertaining thereto, with connecting channels 42 between the space 39 and the space 41 after the last turbine disk 10. Thus the pressure in the space 39 will be approximately equal to the pressure in the outlet of the turbine, by reasonof which an axial pressure will also be produced in a direction opposed to that of the pressure on the balancing plunger 37 These pressures will be approximately equal, first, because the diflerence, in steam pressure on both sides of the balancing plunger 37 is approximately equal to the difference in steam pressure in front of the turbine disk 7 and behind the turbine disk 10, and, second, because the'pressure surface of the balancing plunger 37 is approximately equal to the pressure surface of the turbine disk 7. y

The turbine is provided in known manner with packing means at 40 in connection with means to suck out leaking steam.

According to the invention, the ring 23 and the steam supply part 31 are formed into a head wall without axial connecting flanges, said head wall covering so large an opening that the inner cap 18 may be taken out therethrough together with the rotating parts pertaining to the turbine, the cap 18 being formed at 35, into an enlarged flange or the like hearing on a corresponding flange or the like in the outer cap 25. By this means the inner cap 18 is guided while the opening will at the same time become so large that the inner parts may be conveniently removed out of and introduced into the outer cap. If the steam supply conduit 31 isremoved and the a ring 23 is made free both from the inner and the outercaps, the cap 18 as well as the rotor 4 may, after the central bolt 6 has been reinoved and the pins 5 have been released, be removed axially through the opening limited byfthe enlarged portion at 35 on the outer cap 25. a i

What I claim is 1. In combination in a turbine, an axially divided inner cap carrying guide blades, an axially undivided outer cap surrounding said inner cap, said outer cap being adapted to limit the outlet of the turbine outwardly and being under a lower pressure than the inner cap.

steam supply member,'an axially divided inner cap, an axially undivided outer cap surrounding said inner cap, a frame connected with said outer cap, said outer cap carrying said inner cap as well as the steam supply 2. Incombination in a turbine having amember of the turbine, and a conduit connecting the low pressure part of the turbine with the space between said caps, whereby said outer cap is under a lower pressure than 3, In combination in a turbine, an axially dlvided mner cap, an axially undivided outer cap surrounding said inner cap, a frame conspace between the two casings, said undivided nected with said outer cap, carrying said inner cap, an tainmg the steam supply member of the turbine, said outer cap carrying said end plate and said end plate covering an opening for inserting and removing said inner cap and the moving arts of the turbine.

4. In com ination in a turbine, an axially divided inner cap, said inner cap carrying guide blades, an axially undivided outer cap surrounding said inner cap, a frame connected with said outer cap, said outer cap carrying said inner ca an end plate containlng the steam supp y member of the turbine, said outer cap carrying said end plate and said end plate covering an opening for inserting and removing said inner cap and the moving arts of the turbine.

5. In com ination in a turbine, an axially divided inner cap, said inner ca carrying guide blades, an axially undivide outer cap surrounding said inner cap, a frame expansibly connected with said outer cap, said outer cap carryin said inner cap, an end late containing t e steam supply member 0 the turbine, said outer cap carrying said end containing t e steamsupply member 0 the] turbine, said outer cap carrying said end plate and said end platecovermg an opening for inser'tin and removing said inner cap and the movlng parts of the turbine.

6. In combination in-a turbine, an axially divided inner cap, said inner ca carrying guide blades, an axially undivide outer cap surrounding said inner cap, a frame expansibly connected with said outer cap, said outer 7 cap carryin I said inner cap, an end late plate, said end plate covering an opening-for inserting and removing sai inner cap'and the moving parts of the turbine and a con! duit connecting the low pressure part of-the' turbine with the space between said caps in order to keep said outer cap under a lower pressure than the inner cap.

7 In combination in a turbine, an axially divided innercap carrying guide blades, an axially undivided outer cap surrounding said inner cap and adapted to limit the outlet of the turbine outwardly, a conduit connecting the low pressure part of said turbine with the space between said caps, the fall of pressure in the turbine being such that the difference between the pressure prevailing within thev inner cap and the pressure in said space will be smaller than the difference between the pressure in said space and the atmospheric pressure.

8. In a turbine, an axially divided casing, an inlet member for supplying high pressure elastic fluid to said divided casing, an undivided casing surrounding said divided casing leaving a space between the two casings, an exhaust member in communication with said ALF L said outer cap casing constructed to withstand a portion of end plate con'-- said high pressure elastic fluid.

In testimony whereof I aflix llYlysfi ature. LM.

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