US2166823A - Elastic fluid turbine nozzle - Google Patents

Description

July 18, 1939.

0. ROSENLOCHER ELASTIC FLUID TURBINE NQZZLE Filed'Sept. 1, 195a lnvantor om: Qosenlcher,

His Attorney Patented July 18, 1939 UNITED STATES 2,166,823 ams'rrc FLUID TURBINE NOZZLE Otto Rosenliicher, Berlin-Spandau, Germany, assignor to General Electric Company, a corporation of New York Application September 1, I938, Serial No.228,032 In Germany October 19, 1937 3 Claims.

This invention relates to elastic fluid turbines and more particularly to elastic fluid guide channels or nozzles therefor.

The guide channels or nozzles of gas or steam 5 turbines are usually of a curved cross-sectional shape. It is well known that the jet of operating fluid flowing through the guide channels does not completely fill the passage, but due to its inertia and the change of direction, the jet compresses it) against the face side of the channel and creates a low pressure zone against the back or opposite channel wall. I l a The magnitude of the low pressure area depends upon the sharpness of the bend, the speed l5 and the density of the operating fluid. In consequence of the formation of the area of eddies and low pressure, the main flow of the jet of operating fluid is limited in its cross-section by this eddy area and hence the effective crosssection of the jet is considerably reduced as regards the dimensions of the channel. Due to this constriction, the speed of the jet assumes higher values at this point than the jet would assume were its cross-section to correspond with u the cross-section of the channel. Especially high losses and harmful accessory effects occur when the constriction becomes so great that supersonic speeds are attained. In the widening beyond the constricted region of the jet, the vapor further accelerates to supersonic speedsrjust as in the case of the ordinary extended nozzle, but as the pressure behind the blade rim is higher than the pressure of the steam flowing with supersonic speed, a density impulse occurs by which the pressure of the flowing steam is suddenly raised.

Such density impulses are, as the practice 'of turbine construction has shown, connected with particularly high losses, and may also give rise to fluttering of the blades and rotor.

It is an object of this invention to provide the back or the nozzle blades with such a contour that the formation of low pressure regions and eddies will be substantially minimized.

It is a further object of this invention to provide vent passages through the blades connecting areas of high and low pressure to reduce the formation of eddy areas in the nozzle channels.

For a consideration of what I believe to be novel and my invention, attention is directed to so the following description and the claims appended thereto taken in connection with the accompanying drawing.

In the drawing, Fig. l is a cross-sectional view illustrating an elastic fluid turbine nozzle blade .5 according to my invention, while Fig. 2 is a similar view illustrating a second modification of my invention.

Referring to Fig. 1, the elastic fluid turbine nozzle blade 20 is shown having a front face 2| of substantially the conventional design, while the back side 22 is provided with one or more steps projecting outwardly therefrom and extending across the blade transversely as regards fluid flow. The most desirable position for such steps depends upon the type of a turbine in which 10 nozzles are to be used, considering such factors as the pressure, temperature, and density of the operating fluid. It is preferred that a first step 23 be provided somewhat back of the forward edge of the nozzle, at about the place where the 18 low pressure area begins to form. The step, which faces the channel entrance, creates a contracted vein which causes the jet to adhere rather closely to the surface of the blade therebeyond.

The first step may be followed by other steps, I

such as, 24, suitably arranged at points where the jet again tends to form a low pressure pocket against the-back side of the blade with results similar to those accompanying the provision of the step 23.

It is preferred that channels, or vent passages, be provided through the blades connecting a region of high pressure with the low pressure region to further reduce the tendency to the formation of eddy areas within the nozzle channel. Referring to Fig. 1, a passage 25 is provided through the blade 20 connecting a region of relatively high pressure, in front of the step 23, with the low pressure region before the step 24. In Fig. 2 is shown a second modification in 35 which the blade 20 is provided with a passage 26 extending from the face side of the blade therethrough to the low pressure region on the reverse side. According to the exact location and size of the passages '25 and 26, the steps 23, 23', 24, 24' may be modified as desired and by the coaction of the steps and the vent passages the formation of eddy areas within the nozzle channels may be reduced to a minimum.

Having described the principle of operation of 45 my invention together with the apparatus which I- now consider to represent the best embodiment thereof, I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is:

"1. An elastic fluid turbine nozzle blade having a passageway extending therethrough from a point onv the rear surface thereof toward the u inlet edge of the blade to a point on the rear suriace of the blade toward the exit edge thereof.

2. In an elastic fluid turbine; a plurality of arcuate blades defining nozzle channels for operating fluid, means for minimizing the formation oi low pressure areas in said channels comprisinga pair of spaced apart and outwardly projecting steps on the rear surface of each of said blades, said steps facing the entrance of said channel and a passageway through said blades establishing communication between a high pressure area in said channel and the space between said spaced apart steps. u

o'rro ROSENLCHER.

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