US1967963A - Reversing steam turbine - Google Patents

Description

July 24, 1934.

J. F. METTEN REVERSING STEAM TURBINE Filed Sept. 26, 1933 ATTORNEYS erally on line Patented July 24, 1934 PATENT OFFICE REVERSING STEAM TURBINE John F. Metten, Philadelphia, Pa.

Application September 26, 1933, Serial No. 691,007

8 Claims. (01. 253-70) This invention relates to steam turbines and particularly to turbines of the reversing type operating in either direction of rotation as in turbines for marine propulsion.

,In this type of installation the astern turbine is commonly required to develop from one-third to three-fifths the power developed by the. ahead turbine which is designed for maximum economy while the astern or backing turbine on account of its use in maneuvering is designed with a minimum possible number of stages for the required power in order to keep down the rotation losses during normal forward driving. In previous practice it has been usual for the Iastern or backing turbine to have its exhaust end opposing the exhaust end of the ahead turbine and its nozzle chest attached to the head of the main turbine casing. This has caused objectionable stresses in the turbine casing parts Ldue particularly to the entrance of the hot steam for the reversing turbine into the cool casing parts associated with the exhaust of the main turbine. There is also an unavoidable condensation of steam by the mass of cold metal in ,1 the astern turbine, and in the usual construction this condensed water is blown out at very highvelocities tending to damage the last rows of blading of the ahead turbine.

The object of this invention is to avoid these Iobjections and to provide a reversible turbine in which the ahead turbine and astern turbine are so combined as to reduce the casing stresses and avoid undesirable consequences of the condensation of the steam entering the astern .turbine.

A further object of the invention is to increase the efliciency of the turbine by reducing the outflow resistances and losses and providing forQfree, unobstructed discharge of the steam .to the condenser without turbulence and eddies.

Other objects of the invention particularly in;

the detailedstructure of the. turbine parts will appear from the in connection with jin which v Fig. 1 shows a longitudinal sectional view of the end of a reversible turbine taken on lines 11 of Fig. 2 and illustrating. one embodiment of my invention;

Fig. 2 is a transverse sectional view taken genaway; and V I Fig. 3' is a partial sectional view on enlarged scale taken on the iing'in the direction of'the arrows.

following description tzatkenv the accompanying drawing,

2-2 of Fig. 1 with parts broken line 3-3 of Fig. 2and look- In the specific embodiment of the invention shown in the drawing, the main turbine is indicated generally at 3 mounted on the condenser casing designated 4 and the exhaust end of the main ahead turbine casing is indicated at 5, the main rotor being shown at 6 and the blading at 7 on the rotor and 8 on the stator or casing. The backing turbine 10 is shown as a single stage impulse type unit with the astern turbine disc 11 fixed to the ahead turbine rotor 6 and carrying the moving blades 12. The stationary or guide blades 13 are carried by the casing 14 which incorporates the annular steam chest 15 and is secured to the extension 16 of the main ahead turbine casing by the flange and bolts at 17, this flange being a part of the casing 14 and connected thereto by a series of arms 18. The space between the arms 18 provides for the passage of exhaust steam from the backing turbine into the condenser exhaust passage 20 which is common to both the ahead and backing turbines. Y

The inlets for the supply of steam to the backing turbine are shown at 21 and each consists of a sleeve connecting the nozzle on the outside of the main casing 16 to the steam chest 15. This steam chest 15 is made in two parts in symmetrical annular form around the axis of the turbine as shown and is so shaped as to its outer surface 23 as to form a generally smooth conical guide for the exhaust from the. main ahead turbine. An extension guide ring 24 is provided bringing the proper contour close to the inlet path through the exhaust of the blading '7, 8 and gradually turning this exhaust outward into the discharge.

A similar exhaust guide ring 25 is provided opposite the exhaust blades of the backing turbine to avoid impingement of the high temperature exhaust from the astern wheel on the main casing 16 and also to guide this exhaust outward and avoid turbulence.

' In Fig. 2 a cross-section is shown through the astern turbine, the horizontal parting joint being formed between the upper and lower halves of the backing turbine cylinder. The nozzle chests 15 are separate on the top and bottom half of the cylinder each with its separate steam connections 21 these halves being joined along the line 30 (Fig.2) by special flange parts 14 (Fig. 3). The main exhaust guide extension baffie' 24 is also indicated in Fig. 2 carried across the gap between the ends of the nozzle chest 15 adjacent the joint 30 and forming a continuous and symmetrical annular guide in combiand the arms 18 connecting the chest to the main casing connecting fiange at 17 also provide sufficient compensation to avoid excessive heat stresses in the main casing to which it is attached.

In the turbine of this invention the" extension 16 of the main casing 5 carries the astern turbine in spaced relation to the end wall of the casing and with the arms 18 intervening so that the expansion and contraction of the, astern,

turbine casing parts are not directly imposed as stresses on the supporting casing. The exhaust from the astern turbine being in the same direction as that of the main turbine passes outward toward the end Wall of the extension 16 and spreading around the guide 25 passes back to the outlet passages of the main turbine thus protecting the main turbine parts from the astern turbine exhaust. Both the exhaust of the main turbine and the astern turbine are smoothly guided without obstruction and without the formation of turbulence in the outflow and all of the guiding and supporting parts are compactly assembled within the small end space provided within the extension 16 of the main casing. In the usual reversible turbine with the exhaust rows of blading facing each other undesirable outflow conditions occur in the exhaust partly because the astern turbine wheels and blades come within the path of the outflow of the main turbine, which outflow is of high velocity and causes turbulent conditions at the exhaust exit with an appreciable lowering of the ahead turbine efficiency. In the combination of this invention the main exhaust passes smoothly out around the spreading guide and expands into the discharge spaces, carrying the vapors to the condenser, and similarly, the astern turbine exhaust is smoothly expanded and turned out into the same discharge spaces. At-the points of relatively high velocity where the steam is leaving the turbine blades efiicient conditions of flow are maintained and the velocity of the outflow is progressively lowered as the vapors expand into the discharge spaces. There is nothing obstructive in, the high velocity portion of the outflow of either turbine unit and the discharge from the astern turbine being turned and expanded, isat relatively low velocity where it passes into the discharge spaces of the ahead turbine. Each of these turbine units is thus maintained at high efficiency and without interference from the other.

I claim: A

1. ,In a steam turbine the combination witha main turbine rotor having an exhaust in--a direction toward the end of the turbine, of a separate coaxial reversing turbine rotor at one end of said main rotor adjacent said exhaust and exhausting in the same direction, said r0 tors being spaced apart end to end, and a steam chest for the reversing turbine between said exhausts and annular surfaces provided by -said steam chest for smoothly guiding the exhaust from the main turbine so that it does not impinge on any blading.

2. In a steam turbine, the combination with a casing comprising a main portion and a separate extension, of a main turbine rotor therein having its exhaust in a direction toward the end of the turbine, a reversing turbine rotor at one end of the main portion of said casing having its exhaust in the same direction as the exhaust of the main rotor, an annular entrance steam chest located between said exhausts, and acting to guide the main exhaust outward, said rotors being spaced apart end to end, and means for supporting said reversing turbine from said extension portion of said casing.

3. .In a steam turbine, the combination with a casing, of a main turbine rotor therein having its exhaust in a direction toward the end of theturbine, a separate coaxial reversing turbine rotor at one end of said main rotor in said casing having its exhaust in the same direction as the exhaust of the main rotor, an entrance steam chest located between said exhausts,

means carried by said chest for receiving and mo guiding the main exhaust steam outward, said rotors being spaced apart end toend, and means for supporting said reversing turbine from said casing and permitting the exhaust from the reversing turbine to mix with the exhaust from the main turbinep- I 4; In a steam'turbine, the combination with a turbine casing, of a main turbine rotor therein having an exhaust, an outlet for said exhaust, a reversing turbine in said casing adjacent'the exhaust end of said main turbine rotor and having the exhaust of the reversing turbine in the same directionas the said adjacent exhaust from said main turbine rotor and; adapted to discharge through said main turbine-outlet, said main rotor and reversing turbine being spaced apart end toend, and an annular steam chest between the said main exhaust and said reversing turbine smoothly guid-- ing the discharging steam so that there is no impingement of the exhaust steam on the blading of either rotor. V V

5. In asteam turbine the combination with a casing, of a main turbine rotor adapted to be driven by steam and having its inlet at one end of said casing and its exhaust directed toward the other end thereof,-a separate coaxial reversing turbine rotor between said main rotor exhaust and the end of said casing having its inlet between said-main and said reversing rotors and exhausting in the same direction as the main turbine rotor, said rotors-being arranged-end to end, and means for guiding both of said exhausts to'a common outlet comprising surfaces of the steam inletmeans of said revers ing turbine actingto deflect the exhaust from the main rotor.

' 6. In a steam turbine the combination with a;casing,*of a main turbine rotoradapted tobe driven by steam and having its inletatjone end of said casing and itsexhaust directed toward the other end thereof, a separate coaxial reversing, turbine rotor between W said main" ro tor exhaust and the endof'said'casing having its inlet between. saidmain and said reversing rotors and exhaustingfin; the same. direction as. the main turbine rotor, said rotors being, ar-

ranged end to end, means for'guiding both of said exhausts to a common surfaces of the steam inlet outlet comprising means of said reversing turbine acting to deflect the exhaust from the main rotor, and means for supporting said reversing turbine from the end portion of said casing.

'7. In a steam turbine the combination with a main turbine rotor having an exhaust in a direction toward the end of the turbine, of a separate coaxial reversing turbine rotor mounted at one end of said main rotor adjacent said exhaust and exhausting in the same direction and having a steam chest between said exhausts, said rotors being spaced apart end to end, and means for guiding the exhaust of the main rotor outward comprising annular surfaces carried by said steam chest deflecting said main exhaust so that it does not impinge on any blading.

8. In a steam turbine the combination with a main turbine rotor having a casing comprising a main portion and a separate extension supported from said main portion, a reversible turbine located Wholly within said extension and having spaced arms connecting it to the end of said extension so as to reduce the stresses of expansion and contraction transmitted to said supporting extension, means between said rotors for supplying steam to said reversing turbine, and means for discharging the exhausts from both of said rotors through a common outlet.

JOHN F. METTEN.

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