US668484A - Nozzle for turbines. - Google Patents

Description

' No. 668,484. Pate nted Fob. l9 |90| N. s. BUK.

NOZZLE FUR TURBINES.

(Application filed s. 1: 2."; 1898 (No Model.)

m n I u n I No. 668,484. Patentod'Fob.'l9, I90l. N. S. BOK.

u'ozz'us ron Tuna-mas.

(Application filed 80171:.23, 1898.)

(llo Model.) 2 Shoets$haoi 2.

WiTNESSES: INVENTOR WWW LZ 5. @24

BY ATTORN EY UNiTn STATES PATE T OFFICE.

NILS SVENSSON 136K, OF STOGKHOLM, SWEDEN.

NOZZLE FOR TURBINES.

SPEGIFICATIONi'orming part of Letters Patent No. 668,484, dated February 19, 1901.

Application filed September 23,1898. Serial No. 691,685. (l lo model.)

To (tZZ whom, it may concern:

Be it known that I, NILS SVENSSON 136K, a subject of the King of Sweden and Norway, and a resident; of Stockholm, in the Kingdom of Sweden, have invented certain new and useful Improvements in Nozzles for Elastic- Fluid Turbines, of: which the following is a specification.

The object of this invention is to collect, shape, and direct more perfectly than heretofore the driving fluid of turbines operated by means of vapors, gases, or a 'mixtu re of both, and so that its energy can be utilized by the turbine to a greater extent and by a change of its direction of motion be used for braking or reversing the motor.

In the accompanying drawings, which illustrate embodiments of the invention, Figure 1 is an axial section of the nozzle and includes also cross-sections of the same, showing the forms at different points. Fig. 2 is a view similar to Fig. l, but showing the nozzle jointed, so that its outlet extremity may be turned for reversing. Fig. 3 illustrates another form of reversing-nozzle. Figs. 4 and 5 are illustrative Views which will be explained. Fig. 6 illustrates a nozzle similar to Fig. 1, except that the exhaustion-passage is curved.

In Fig. 1 an expansion-passage a is shown, which is continued by a bend b in one piece with it, through which the driving fluid is conducted to the vanes of an axial turbine c on having been compelled by its own ms ci ca during its passage through the said bend to follow along the concave surface of the bend and in so doing to fill the whole width of the passageformed by the bend and its continuation, the guide-passage d forming a layer the thickness of which is approximately determined by the pressure of admission. In the present case the expansion-passage a has circular sections, while the sections of the bend b, which collects the fluid, gradually change from circular to rectangular ones with rounded corners, the latter sections in the guidepassage d, succeeding the bend b, gradually passing into the shape of a segment of a circular ring. (See the sections in Fig. 1.) In the last section of the guide-passage (at e) the latter has the same or nearly the same dimension as the opposite space between the vanes, measured radially. The edge of the last section of the guide-passage cl at the end of the aforesaid circular-ring segment where the collected fluid flows through should be extended so far that no part of the fluid can escape, being directed by itonto the turbine wheel at the angle that the fluid should have with relation to the direction of the first-elementf of the vanes of the turbine.

In Fig. 2 the bend b and guide-passage d by means of a conical joint communicate with the expansion-passage on, and consequently by being rotated about the axis A B can be so reversed that the driving fluid will strike the back of the vanes of the turbine, a braking or a reversal of the direction of motion of the turbine being thus effected. The dotted lines in Fig. 2 show the position of passages b and d after the reversal.

In Fig. 3 it is indicated how the direction of motion of the driving fluid can be changed by shifting or sliding the sections 1) d of the passage over to the right, so that the sections 1) d will instead form the continuation of the passage (1-. If a similar change of direction is to be effected in the passage in Fig. 1, this is done by rotating the part containing the passages a, b, and 61 around the axis A B.

It is evidently of importance that the driving fluid in the last section of the admissionpassage shall be so shaped that when first admitted to the first element of the vanes it will fill the entire radial width of the vane-space, (in an axial turbine,) for if this is not the case the fluid, owing to its pressure on the surface of the vane, must disperse on the vane while the latter is moving away from it. In this case the pressure of the fluid on the same surface is decreased by an amount corresponding to the work spent in the said dispersion. Moreover, it is probable that the losses are still further augmented by the eddies formed in the act of dispersion.

That the last sectional shape (a segment of a circular ring) of the admissi0n-passage is better than the extended elliptical form produced by obliquely cutting a cylindrical nozzle-piece is very evident from Fig. 4, where g h c' It show a circular-ring segment of the same height as the ellipse Z m n 0 when both have the same area. In this figure, g 76 is equal to the radial width of the vane-space.

Calculation shows that about 12.5 per cent. of the whole area of the ellipse falls on the ends of the ellipse overlapping the ring-segmen t, while evidently an equal percentage of thearea falling inside the ring-segment is not taken up by the ellipse. about twenty-five per cent. of the driving fluid is, owing to the elliptical section, so unfavorably applied to the vanes of the turbine that it is forced to disperse more or less, and in the axial turbine this dispersion is radially inward and outward in the vane-spaces. In addition to this, owing to the greater length of the ellipse, the dispersion takes place in about 21.5 per cent. more vane-space, and accordingly under more unfavorable conditions with regard to friction of the vanes, this in the case of full admission in an ordinary expansion-passage having a straight nozzle of cylindrical cross-section. The conditions will be still more unfavorable to such an expansion-passage when the reduction of the pressure of admission of the fluid by the governor is taken into consideration, for in the straight expansion-passage one of the following alternatives will then occur: (a) The driving fluid on completing its expansion, as indicated by dotted lines in Fig. 5, will leave the conical wall at the section p, for instance, and approximately retaining its shape will enter between the vanes, covering an elliptic area 1 r s i, (see Fig. 4,) which has been reduced to the length (1 .9, thus embracing a smaller number of spaces, but also in the same ratio to the wid th *1 f, so that the dispersion in the spaces between the vanes becomes still more considerable than in the case of full admission, or (Z2) the velocity of the driving fluid will decrease in the admissionpassage in the same ratio as the section at p is greater than that at p, so that the passage will be completely filled and the fluid will enter the turbine wheel with increased velocity, covering the entire ellipse lm n 0, in which case the same disadvantages of dispersion and distribution over an equal number of vane-spaces will obtain as in the case of full admission.

Vt ith a bent passage and the last section shaped as a segment of a circular ring of a height equaling the radial height of the vanespace the driving fluid under all circumstances flows along the concave wall of the bend at velocities approximately corresponding to the different pressures of admission, and since the radial width of discharge of the driving liuid onto the vanes during the period of admission is constant h 1) the extent of space occupied by the fluid in the direction of the periphery will be approximately proportional to the pressure of admission. Thus, for instance, in Fig. a the ellipse q 1's i is equal in size to the circular-ring segment 0 i 1;, which indicates the shape of the vanesurface occupied by the driving fluid when the same fluid is admitted to the turbine by a bent passage. and for the same reduction in the pressure of admission as has been assumed to take place in Fig. 5. (See dotted lines.) Thus with this arrangement of passages the number of vane-spaces occupied by the fluid is diminished in the same ratio as the pressure of admission is lowered by the This means that l governor, or, in other words, the driving fluid in this case under all conditions is properly collected and shaped, thus favoring the elliciency.

From the above it is also evident that the wall of the bend and of the guide passage or nozzle, which is situated opposite to that by which the conduction and shaping of the fluid is effected, can be left out without affecting the working, and that consequently this portion of the passage can be made either open or closed.

In order that the driving fluid, even for the maximum reduction of the pressure of admission, shall follow the portion of the wall of the expansion-passage c which passes over into the concave portion of the bend b, the expansion-passage a may, as in Fig. (5, be slightly curved, thus causing the fluid to occupy the cross-hatched portion of the passage. (Seen in Fig. 6.) It will be evident without further explanation that if the radial dimension of the last section (at e) be taken large in comparison with the tangential ones the form of the said last section may be made quite rectangular.

Having thus described my invention, I claim 1. A nozzle fora fluid-turbine, the passage in which has a gradually-flared inlet portion a, a curved intermediate portion b, and a straight outlet portion cl, the portions a and (I being connected by said curved portion, substantially as set forth.

2. A nozzle for a fluid-turbine, the passage in which has a gradually-flared inlet portion a, a curved intermediate portion Z), and an outlet portion (Z, the part of the nozzle containing said portions 1) and (Z of the passage being movable, whereby the direction of the discharge may be reversed, substantially as set forth.

3. A nozzle fora fluid-turbine, the passage in which is flared throughout the first or inlet part of its length, curved laterally and of uniform width throughout the second or intermediate part of its length, and straight and of uniform width throughout the third, or outlet part of its length, substantially as set forth.

at. A nozzle for a fluid-turbine having in it a passage the inlet portion (t of which is flared uniformly about its axis, the intermediate portion 1) curved, and the outlet portion (Z straight with its axis oblique to that of the portion a, that portion of the nozzle in which the oblique passage (Z is formed being rotatable about the axis of the portion a, substantially as set forth.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

NILS SVENSSON non.

Witnesses:

ERNST SVANGVIST, H. B. OHLSSON.

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