US2197521A - Turbine apparatus - Google Patents

Description

Aprifl 16, 1. A. EGLI 2,197,521

TURBINE APPARATUS Filed April 21, 1938 Ha im ll/llllll/l/lIII/IIj Fm a.

ll WITNESSES: INVENTOR HDOLF' Equ. BY J v 'BIM ATTORNEY Patented Apr. 16, 1940 UNITED STATES PATENT OFFICE Application April 21, 1938, Serial No. 203,254

2 Claims.

My invention relates to steam turbines and more particularly to stages thereof of the partial peripheral admission impulse type and it has for an object to provide for gradual acceleration of steam in blade passages as the latter enter the nozzle region.

In a partial peripheral admission impulse stage, the steam remains practically at rest in the rotating blade passages as long as the latter are not in the nozzle zone. Accordingly, as a blade passage enters the nozzle zone, the steam therein must be accelerated by the initial jet or jets before normal flow through the blade passage is established. Acceleration of the fluid involves pressures and velocities which produce axial forces on the blades larger than those of the steady state flow. In some cases, such an axial force acting on the blades may be excessive, and it is the object of the present invention to reduce the velocity in the initial nozzle or nozzles of a group in order to reduce the rate of acceleration and therefore the axial force acting on the blades.

A more particular object of my invention is to provide the initial nozzle or nozzles of a group with orifices serving to throttle the admission to the initial nozzle passage or passages for the purpose of reducing the velocity in such passage or passages relatively to the velocity in the remaining passages.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

Fig. 1 is a sectional view of a two-row impulse turbine stage having my improved nozzle group; and,

Fig. 2 is a detail developed sectional view showing my improved nozzle group.

In the drawing, there is shown a rotor l0 and a stator ll carrying, respectively, the rotating blades l2 and I3 and the intervening stationary blades M, the rotating rows of blades I2 and I3 and the intervening stationary row of blades l4 constituting the usual two-row impulse stage.

Steam at suitably high velocity is supplied to the initial row of blades [2 by means of a nozzle group, at E5, communicating with a nozzle chamber l6.

As the rotating blades are not subject to the influence of steam issuing from the nozzle passages for a considerable portion of each revolution, it will be apparent that steam remains at rest relative to the moving blade passages as long as the latter are not in the nozzle zone. Therefore, referring to Fig. 2, with the blades l2 moving in the direction of the arrow,it will be apparent that just as soon as a blade passage is acted upon by the jet or steam issuing from the initialnozzle passage ll, steam in the blade passage will be accelerated by the jet and axial as well as lateral force will be applied to the blades depending upon the rate of acceleration.

The rate of acceleration, and consequently the 10 magnitude of the axial or lateral force, is reduced by throttling the admission of steam to the initial passage, such passage having a box or cover 20 separating the entrance thereof from the nozzle chamber l6 except for the orifice or nozzle 2|. The orifice or nozzle 2| restricts the flow of steam from the chamber IE to the nozzle passage, that is, it establishes a pressure drop in series with the pressure drop in the nozzle passage ll, the latter pressure drop determining the 20 jet velocity. By this means, the jet velocity of the passage I1 is reduced over what it would be without the cover 26) and the orifice or nozzle 2!; and, in consequence, the steam in the blade passage is accelerated less rapidly as it comes 5 under the influence of the jet and the magnitude of the lateral force induced on the moving blades corresponding to the acceleration is also reduced. 9

A more gradual acceleration effect may be had by progressively increasing jet velocities. Accordingly, in Fig. 2, the initial nozzle passage ll has the adjacent passage I8 supplied with steam by a larger orifice or nozzle 22. The remaining nozzle passage or passages l9 of the group are in direct communication with the nozzle chamber [6.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by theprior art or as are specifically set forth in the appended 5 claims.

What I claim is:

1. In a steam turbine, a row of moving blades, means defining a nozzle chamber, means providing for the partial peripheral admission of 50 steam to the row of moving blades from the nozzle chamber and comprising a plurality of nozzle passages, and a cover for the initial nozzle passage of the group considered in the direction of motion of the moving blades and separating the inlet of said passage from the nozzle chamher, said cover'having an orifice for supplying steam from the nozzle chamber to the initial nozzle passage.

2. In a steam turbine, a row of moving blades, means defining a nozzle chamber, means providing for the partial peripheral admission of steam to the row of moving blades from the nozzle chamber and comprising a plurality of nozzle passages, and a cover for a plurality of nozzle passages at the end of the group approached by the moving blades, said cover having orifices for admitting steam from the nozzle chamber to the respective passages and said orifices increasing in size in the direction of blade travel in order to provide for gradual increase in velocity of the jets.

ADOLF EGLI.

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