US1151689A - Oblique-cut guide-channel for turbines. - Google Patents

Description

H. KELLER.

OBLIQUE CUT GUIDE CHANNEL FOR TURBINES.

APPLICATION FILED OCT. I3. 1914.

Patented Aug". 31, 1915.

2 SHEETS-SHEET I.

fiiizewes H. KELLER.

OBLIQUE CUT GUIDE CHANNEL FOR TURBINES.

APPLICATION FILED OCT. 13 I914- Patented Aug. 31,1915.

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HULDREIGI-I KELLER, OF ZURICH, SWITZERLAND, ASSIGNOR TO THE FIRM OF AK'IIEN- GESELLSCI-IAIFT DER MASCI-IINENFABBIKEN ESCHEB WYSS & GIE., OF ZURICH,

SWITZERLAND.

OBLIQUE-CUT GUIDE-CHANNEL FOR TURBINES.

Application filed October 13, 1914.

To all whom it may concern Be it known that I, HULDREICH KELLER, a citizen of the Republic of Switzerland, residing at Zurich, Switzerland, have invented new and useful Improvements in Oblique- Cut Guide-Channels with Quadrilateral Section for Steam and Gas Turbines; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which is appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification.

This invention relates to an oblique-cut guide channel, with quadrilateral section, for steam or gas turbines, which are working with a so-called overeXpansion. These turbines are such that, in the pressure stage in which the guide channels are used, a drop of pressure is to be utilized which is greater than that which corresponds theoretically to the ratio of the section of nozzle outlet to the smallest section throat of the guide channel. If, for instance, guide channels are used, the walls of which are parallel toward the outlet, it is thereby presumed that a velocity greater than the velocity of sound should be attained with these channels, although theory allows only the attaining of the velocity of sound, or even a somewhat smaller velocity. According to this inven tion, the side walls of such an oblique-cut guide channel are so designed that, seen in the direction of the fiow, they are in the oblique-cut more deflected from the middle plane of the channel than in that part of the channel having fully inclosed section and adjacent to the nozzle-throat. Also according to this invention, the outlet opening of the oblique-cut has the form of a trapezoid, having its smaller side at the beginning, its broader side at the end of the oblique-cut.

The present invention may be better understood by reference to the Figures 1 to 9 on the annexed drawing sheet, which refers to a horizontal axially working steam tur bine, the guide channels of same consisting chiefly of parallel running walls in that part of the channel which has fully inclosed section and which channels are intended to allow a steam velocity exceeding that of sound and Specification of Letters Patent.

Patented Au 31, 1915.

Serial No. 866,447.

may be used for a pression stage in which the velocity of steam is greater than the critical pressure.

Fig. 1 shows diagrammatically the axial projection of the outlet section of a number of guide channels, which are designed according to the usual custom, with parallel walls and of rectangular section, arranged in series close to one another, the axial center line of which, for illustrative purposes, is developed along a plane, instead of a cylindrical surface. Fig. 2 shows the development of the aXial center of such a guide and runner wheel blading in a flat plane. Fig. 3 shows diagrammatically, seen from A, the course in which the layer of steam flows along the wall I) just before the points 5 and 6. Fig. 4 is a corresponding figure, showing the course in which the layer of steam flows along the wall 0 just near the points 7 and 8. Fig. 5 is a cross-section on the line CD through the steam jet leaving the guide channel II; Fig. 6 is a corresponding cross section through the steam jets leaving the channels I, II, III; Fig. 7 shows the section which the steam jets have to have, in order that said section coincides with the inlet plane of the runner wheel. Fig. 8 is a projection corresponding to Fig. 1, illustrating the outlet-openings of guide channels constructed according to this invention; Fig. 9 is a cross-section on the line 5-11 of Fig. 2 through a guide channel of the hitherto known form; Fig. 10 is a corresponding cross-section through a guide channel constructed according to my invention; Fig. 11 is an imaginary section taken immediately beneath the blade 0 through the channel 11; Fig. 12 is a longitudinal section on the line IVV of Fig. 13 seen from X, of a De Laval nozzle constructed according to my invention; Fig. 13 shows a section on the line VIVII of Fig. 10, seen from Y, of a nozzle of the hitherto known shape; Fig. la is the aXial projection of the outlet opening of this nozzle; Fig. 15 is a cross section on the line YY (Figs. 12 and 13) seen from VI, of a De Laval nozzle of the known form; Fig. 16 is a corresponding cross section of a nozzle constructed according to my invention; Fig. 17 is a section corresponding to Fig. 13, through a nozzle constructed ac.- cording to my invention, and Fig. 18 is a corresponding section through a nozzle of the guide channel 11 will be hereafter considered. The steam enters in the direction of the arrow at 9 (Fig. 2) and between the positions 10, 12 and 5, 11 and in the adjacent oblique-cut 5-8 (Fig. 2) the two blades 5 and 0 have a constant spacing, 2'. e. are parallel to each other. Thus the continuation of the blade 0 beyond this parallel wall portion, 11. e. from 11 to 8, lies in exactly the same direction as 12 to 11. Also the side walls (Z and e have a constant spacing. Re-

ferring to Fig. 2, the part between 10, 12 and 5, 11, represents the longitudinal section of the channel H, through the part where the walls lie parallel, the triangle 5, 8,

. 11, the part through the socalled obliquecut. As it is presumed that the pressure stage for which the channel is determined should create a velocity above that of sound, it follows that within the parallel wall portion, ale. from 10, 12 and 5, 11 (losses due to friction neglected) the critical pressure p prevails. Tests have proved that a particle of steam flowing along the surface of but a few millimeters length, for instance from 5 to 13, and being under the critical pressure 79 in the neighborhood of the point 5, or at the point 5 decreases to the back pressure 1), existing in the neighborhood of the runner wheel. A steam particle flowing along the wall 0 of the channel 11, which still possesses at or near the point 11 the critical pressure, expands along the comparatively long distance from 11 to 8, to approximately the back pressure 79 Since the steam possesses in the immediate vicinity of the point 5, a certain overpressure above the surrounding steam, which is approximately equal to the difference between the critical pressure p and the back pressure 9 the steam jet tends to expand. In the direction normal to the side 10 to 5 this is only possible in a small degree because expansion of the steam is hindered by the steam delivered through the channel I. l The steam will therefore tend to expand chiefly in the direction vertically to the middle plane of the guide wheel and therefore vertically to the plane of Fig. 2. The degree of this expansion is much greater just behind point 5,

- Where a greater pressure prevails, than immediately behind point 8, where the pressure isnearly equal to the back pressure 79,. Layers of steam which are parallel to the walls Z) and 0, will flow, seen from A, in a course as shown diagrammatically in Figs. 3 and 4. The shaded part represents the side walls d and e of the channel. According to Fig. 3, the first mentioned layer of steam has, just before the points 5 and 6, which latter correspond to the same points of Fig. l s, 2'. e. the width of the channel. At a distance a; from the latter, 2'. e. at 13 to 13,

where this layer of steam enters into the runner wheel, it has the width t. As will be seen from Fig. 1, the steam layer flowing along the wall 0 at '4' to 8, possesses likewise the channel width s,but at adistancewat 16, Fig. 2, where this steam layer penetrates into the runner wheel, it possesses the breadth. 1616:u (Fig. l) which is much less than the breadth a (Fig. 3). A cross section through the steam jet, on leaving the guide channel 11, taken in the entrance plane of the runner wheel ((1-51) of Fig. 2) would be represented by a trapezoid 13, 16, 16, 13 Fig. 5. If we imagine all the steam jets, after leaving the guide channels I, II, III, etc., to be cut in the manner before mentioned, by a plane, coinciding with the inlet edges of the runner wheel blades (C D Fig. 2), a form as shown in Fig. 6 ofdrawing representing a series of trapezoids P, 11, HP, etc., will be obtained. In order that the runner wheel blading may catch all the various steam jets, the height of the moving blades should be at least equal to 25. Under these conditions, there would be, however, at position E, a certain amount of waste space. As it is desirable to avoid these waste spaces, which would necessitate the height of the moving blades being only equal to a, the excess portion E of the steam due to the larger width of the steam jet ver this breadth would result in a loss of useful work in the runner wheel, and furthermore would interfere with the passage of the other steam jets. In order that the steam jets may have such a form that their sections, made by a plane coinciding with the inlet plane of the runner wheel (CD Fig. 2), will take the shape as illustrated in Fig. 7, the side walls of the steam channels I, II, III, etc., will, according to this invention in the oblique-cut be deflected in such a manner, that, for example, the internal distance at the point 8 in channel II is larger than at the points 5 and 11. An imaginary section taken immediately beneath the blade 0 through channel II and seen from A would take the form as shown in Fig. 11, instead of that shown in Fig. 4. Thus according to this invention the outlet openings of the channels have the shape of a trapezoid, as shown in Fig. 8, the short cross-side 5*6* of which is lying at the beginning, the long cross-side 7 *8* of which is lying at the end of the oblique-cut; A longitudinal section, taken above the blade 6, however, retains the form shown in Fig. 3. In this manner the guide wheel rim at its outlet takes, instead of the arrangement shown in Fig. 1, which is composed of rectangles, an arrangement made up of a series of trapezoids as shown in Fig. 8. These latter, still retain their breadth s on their smaller side, but on the broader side of the trapezoids however, have the breadth i), which is determined by the breadth of the whole steam jet entering the inlet plane of the runner wheel taking into consideration that expansion of the steam jet down to the back pressure p meanwhile occurred and also by taking into consideration its volume and velocity. Such an outlet opening may also be obtained by guide-channels with par.- allel end walls by giving the cross section for instance of the channel II in Fig. 2 at 5-11 or 10-12 not a rectangular shape as shown in Fig. 9, but a trapezoid like shape as shown in Fig. 10 in such a manner, that the front wall of the channel, that is the back side 12-8 of the blade 0 of the channel II, is broader than the back wall of the channel, that is the front wall 10-5 of the blade 0.

This invention can also be applied to the so-called De Laval nozzle as shown in Fig. 12 in the longitudinal section as seen from X and taken through IV-V of Fig. 13 and also in Fig. 13 which shows a sectional plan of the nozzle taken through VI and VII in Fig. 12 and seen from Y. The nozzle possesses in the longitudinal section seen at 21-22 its narrowest section or throat, at position 23-24: the oblique-cut begins. In the case of nozzles as constructed up to the present time (seen in Fig. 13) the side walls 28 to 27 and from 28 to 27 have at most the same inclination to the guide wheel middle plane (IV-V) as in the fully inclosed portion of the nozzle, 2'. e. from 26 to 28 and from 26 to 28. According to the present invention, the side walls are given, in the oblique-cut, a greater inclination to the middle plane, than in the fully inclosed portion of the nozzle, 6. e. the side walls, in the oblique-cut, take up the positions shown by the lines 29 to 31 and 29 to 31. Special attention is drawn to the fact that, in some of the nozzles hitherto constructed they have, in the oblique-cut, even parallel side walls, as shown by the lines 30 to 32 and 30 to 32 in Fig. 18, 2'. 6. parallel to the straight middle line. The front view of such a guide wheel rim is represented by Fig. 1, while the nozzles according to this invention, having a form as shown in Fig. 17 (28-31 and 28-31), the front View of the guide wheel rim is represented as in Fig. 8.

Fig. 15 shows a cross-section of the nozzle taken in the plane X-Y and seen from VI. The side wall 21-22-24-25-23-21 as shown in Fig. 12, is a plane, the section line of which is thestraight line26-27 asshown in Fig. 13. At the side wall of the front li-mit line 22-25 extends over the beginning of the oblique-cut at 24 and both the side walls (26-27 and 26-27 in Fig. 13) are deflecting toward the outlet, the outlet opening of the oblique-cut obtains the shape of a trapezoid as shown in Fig. 14 (23-23- 25-25) corresponding with Fig. 8. The form of the trapezoid can be still more expressed, if the cross sectionof the De-Laval nozzle as seen from VI in Fig. 12 is not rectangular as shown in Fig. 15, but is made quadrilateral, i. e. of a trapezoid shape as shown in Fig. 16.

It is not necessary, that the beginning of the greater inclination of the side walls should coincide with the beginning of the oblique-cut.

In order that consideration may be given to axial working turbines of the cylinder form, the channel cross-section should not be taken symmetrically through the mean cylinder-plane. Further the outlet sections of the guide channels may be twisted after a known special manner relatively to each other. out of the mean circular ring in the direction of the rotation of the rotor, as shown in American Letters Patent No. 1024.391 of April 23rd, 1912.

What I wish to claim is:

1. In a guide channel for elastic fluid turbines working with over-expansion, an oblique-cut having an outlet opening, which has the form of a trapezoid, the shorter parallel side of which lies at the beginning and the longer parallel side of which lies at the end of the oblique-cut.

2. In a guide channel for elastic fluid turbines working with over-expansion, a channel portion with a rectangular cross section and an oblique-cut having side walls, which are more deflected from the middle plane of the channel than the side walls of said portion having a rectangular cross section.

3. In a guide channel for elastic fluid turbines working with over-expansion, a channel portion with a rectangular cross-section and parallel walls and an oblique-cut having diverging side walls.

4:. In a guide channel for elastic fluids, a throat, an adjacent diverging portion with a rectangular cross section and an obliquecut having side walls, which are more de flected from the middle plane of the channel than the side walls of said portion having a rectangular cross section.

5. A guide channel for elastic fluid turbines working with over-expansion, having side walls, which are even from the smallest cross-section of the channel to its outlet end and which are so inclined with respect to each other that the front limiting wall of thenchannel is broader than the rear limiting wa v 6. In a guide channel for elastic fluid turbines I working with over-expansion, a throat, a channel portion arranged adjacent said throat and having a fully inclosed section and an oblique-cut provided with an outlet opening 'having the form of a trapezoid, each lateral limiting wall of the channel forming a plane from the throat to the outer point of the oblique-cut. I

7. In a guide channel for elastic fluid turbines working with over-expansion, a

channel'portion having a fully inclosed sec-- tion and an oblique-cut having an outlet opening, which has the form of a trapezold,

the shorter parallel side of which lies at Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G.

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