US2840342A - Turbine exhaust - Google Patents

Description

June 24, -1958 D. lli. SILVERN TURBINE E1n-MUST Filed March 1v, 195s IURBINE EXHAUST David H. Silvern, Olean, N. Y. Application March 17, 1953, serial No. 342,780

s claims. (ci. 25a- 39) This invention relates to an improvement for discharging an elastic fluid from axial flow machines; more particularly, this invention pertains to means for collecting and discharging the elastic `lluid leaving the nal blade wheel of an axial ilow turbine.

Turbines, by and large, Convert the pressure head available in an elastic fluidv or gas such as steam, air or combustion gases, into useful energy. The elastic fluid discharges from the blades of the last turbine stage yat comparatively high velocity and low pressure.. yThis Vhigh velocity decreases through the ggas outlet passageway and generally the ultimate exhaustpressure is less ,t'hanthe pressure of the gas leaving the blades, indicatingfthat energy `losses occur in the outlet passageway to dissipate velocity and pressure alike. Numerous proposals have been advanced in the art forrminimizingy these. energy losses in the outlet passageway 'but to date noue has been found to reduce these losses to a material extent.

An object of this invention is to provide a structure which avoids the loss .of pressure head in vthe outlet passageway of an axial iiow turbine.

ited States Patent A further object is to provide a turbine outlet structure which converts lthe high `velocity of the gas exhausting from the `blades of the last turbine Wheel into pressure while efficiently directing the exhaust gas away from Vthe turbine blades.A

Other objects and'advantages of the. invention will lbe apparent from the description whichfollows.

In the accompanying drawings forming a part of the specification and showing for exemplifcation a preferred form of this invention:

Figure 1 is' a schematically illustrated cross-sectional view of the turbine outlet structure; and Y Figure 2 is a section through Iline 2-2 of Figure l.

An axial flow turbine 10, partially represented, discharges (the gas lfrom 'blades 12 of its last stage in a generally axial direction, i. e., parallel to rotor shaft 14. The gas flows 'without any change of ldirection into diffuser yll6 which, according to well known principles, translates gas velocity into a static pressure head. Diff-user 16, which is an annular passageway that is gradually flared outwardly relative to the rotor shaft 14, starts with a substantially straight section having a 'length generally more than twice the height of the blades 12 in the Ilast turbine stage. Ordinarily, the length of the straight section of diffuser 16 is at least one foot. The crosssectional area of diffuser 16 gradually increases along its length to the order of two or three times its area adjacent blades 12. A critical `feature of proper diffuser design is the requirement of symmetrical gas flow therethrough without substantial Change in the direction of gas iiow.

At a point Where diffusion is substantially completed,

p 2,840,342 Fat-tentedV June 24, 1958 conduit 24. Therefore, vane 20a directly in line with exhaust 24 is straight, that is, is aligned with a plane passed through it and the turbine axis. The others are individually curved relative to a plane passed through the innermost point thereof, that is, the point on the vanes closest to `the radial axis of the turbine,l and the `turbine axis, each according to the angle through which the gas must be dellected to ow toward exhaust 24. The end vanes Zilli which are farthest from exhaust 24 tendto divide the gas at the bottom of ring 22 so that ha-lf ilows around each side of collector ring 22. As can be seen in Figure 2, each vane is so angled as to direct the gas laminar which ilows over it towards the exhaust 24, with the angles of the individual vanes, as illustrated, 'being such that the sum total of all the laminae from all of the vanes on each side of the plane through vane 20a and the turbine axis, substantially filling the collector ring. The individual vanes 20 are preferably joined into a unitary structure 'by two at rings 30. Thus, all the vanes 20 may-'be prepositioned in proper relationship to each other and the assembly inserted at the entrancerto the collector ring 22. Alternatively, each vane 20 may be individually positioned and fastened to the side lwalls of collector ring 22. l

The presence .of vanes 20is of Critical importance. Transforming the symmetrical axial and radial `liows into the generally rotational asymmetrical flow in collector ring 22 is best effected by deecting forces applied lby vanes 20.` In the absence of vanes Ztl,V the asymmetrical ilow occurring in collector ring 22 appears to cause great turbulence and to react upstream on diffuser 16 by building up the backv pressure land reducing. turbine output.

It has been found important to haveV each change of direction of Ygas yflew substantially completed, before cornmencing a new change of direction. Thus, the gas has substantially completed turning from a substantially axial flow direction in diiuser =16 to a direction radially outward from rotor shaft i4, before it is redirected'around collector kring 22 toward exhaust conduit 24. The-separation of the angular displacements effected `by radial turn 1-8 and guide vanes 2i) is essential to the successful operation of this invention. It has been found that positioning vanes 20 further upstream, i. e., inside radial turn 18, builds up a back pressure thereby decreasing turbine efficiency.

Collector ring 22 gradually increases in crosssection from a minimum adjacent vanes 2Gb Vto a maximum adjacent the entrance to exhaust conduit 24. The actual relative 'dimensions of collector ring 22 are proportioned in conformity with the volumes of gas entering all along its inner edge from between the vanes 20. The exhaust conduit 24 Will ordinarily exhaust to a condenser in the case-of a steam turbine, and to a regenerator in the case of a gas turbine.

A combustion gas turbine `built according to the principles of this invention lwith the 'final stage of turbine blades 4 inches high, a diffuser (straight section) i8 inches long, a radial turn ending at to the rotor axle, and 37 guide vanes equidistant-ly spaced around the entrance to the collector ring delivered 4300 horsepower. Without the guide vanes, the same turbine delivered only 4,0004 horsepower.

IWhile this invention has been described in connection with an axial 'ow turbine, it is not limited thereto. Axial `remove the `compressed gas will increase lcompressor efficiency. Y

IIn view of the various modifications of nthe invention which will'occur to those skilled in the art upon consideration of the foregoing disclosure without departing from the spirit Vor scope thereof, only such limitations should be imposed as are indicated by the appended claims. What is claimed is: l. An exhaust for use in an axialliow turbine com prising a diffuser beginning at the last stage of the turbine and terminating in a radial turn `for divertingthe axial llow of `the turbine gasesY into `a radial ow; a radially extending collector ring, having a single exhaust conduit opening, surrounding and opening into the radial turn for colhausting the c ollected gases through its exhaust conduit; a plurality of vanes separating the radial turn and the collector ring with the individual vanes so curved away from radial planes through the4 turbine axis as to separate the gases into two parts with both parts'being simultaneously directed around opposite sides of the collector ring towards the exhaust conduit. I f

2. An exhaust for use in anaxial ow turbine comprising a diffuserbeginningat the last stage of the turbine and terminating in aradial turn for diverting the axial tlow of the turbine gases into Aa radial ow; aradially extending collector ring, having a single exhaust conduit, surrounding and opening `into `the radial turn -for collecting the gases exhausting from the radial turn and then exhausting the collectedgases through the exhaust conduit; a `plurality of vanes separating said radial turn'and collector ring with the vanes being divided into two oppositely oriented `groupsland the vanes of each group -extendjng'fromthe radial turn towards the collector ring and each vane being angled towards the collector exhaust conduitrelativeto radialpplanes through the turbine A-axis Vto split thegases radially owing from the radial'turn into two simultaneously flowing circumferential streams with each stream flowing only through one half'of the collector ring towards the exhaust conduit and the streams flowing in opposite directions.

3. Aconstruction as delned in claim 2, and each vane being oriented at a` greater angle towards the collector exhaust conduit than the preceding vane starting with the vanes most distant `from the exhaust conduit to laminate the opposite owing streams, Iwith each gas laminar 0f the streams being directed towards the collector'ex- 4 haust conduit and `with the stream laminations filling the collector ring.

4. A gas turbine exhaustV for an axial tlow turbine for changing the axial 4flow of gas lrst into a radial ow and then into a circumferential ow divided into two major, oppositely and simultaneously owing sections directed towards an exhaustopening, comprising: an axial ow diffuser in the form of an outer cylindrical wall spaced `from and surrounding an inner cylindrical wall beginning at the last stage of the turbine and terminating in a radial turn for directing the axial flow of the gases between said `walls through the diffuser then to exhaust the gases radially of the diffuser, a radially extending collector ring surrounding and opening into the radial turn and `having a collector exhaust; guide vane means positioned lbetween the radial turn and the collector ring and arranged for directing the radial ow of gases into the Y collector ring in a circumferential flow of two sections Y lecting the gases exhausting therefrom and thereafterl exlwith the sections simultaneously flowing, each through one `halt' of the collector ring, towards the collector exhaust land with one'section owing in a clockwise direction and the other in a Ycounter-clockwise direction, said yguide vane means comprising a plurality of vanes arranged to surround the radial turn with each vane extending in a direction from the radial turn towards the collector Vringwith the vanes being divided into two groups, the vanes 'of one group being curved towards the collector exhaust in one directionrelative to radial planes through the turbine axis and the .vanes in the other group being curved towards the collector exhaust in the opposite direction. i

5. A construction as defined `in claim 4, and each vane 4being curved at a greater angle towards the collector exhaust than the preceding vane starting with the vanes most distant lfrom the collector exhaust to laminate the oppositely flowing -gas sections with each gas ylaminar vbeing directed towards the collector exhaust and with the gas vlaminations arranged to completely fill the collector ring.

References Cited in the tile of `this patent l UNITED STATES PATENTS 1,328,8354 Kasley Jan. 27, 1920 1,488,582 Allen Apr. 1, 1924 2,247,817 McMahan July 1, 1941 2,435,042 Johansson Jan. 27, 1948 2,453,524 McMahan Nov. 9, 1948 2,458,730 Ponomarel `Tan. 11, 1949 2,620,230 Hait Dec. 2, 1952 2,641,442 Buchi, June 9, 1953 2,655,307

Buckland.V Oct. 13, 1953

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