US1539396A - Elastic-fluid turbine - Google Patents

Description

Patented May 26, 1925..

FRANZ LiisnL, or BRUNN, 'oznonosLovAKIA.

ELASTIC-FLUID TURBINE.

Application filed August 2-6, 1924, Serial No. 734,355.

T0 all whom it may co ncewt:

Be it known that I, FRANZ Losnn, a citizen of Czechoslovakia, residing at Brumn Czechoslovakia, have invented certain new and useful Improvements in Elastic-Fluid Turbines, of which the following is a specification.

This invention relates to turbines of the elastic fluid type.

The object of the invention generally stated is a turbine having higher thermodynamic efficiency than prior known turbines, and particularly a high pressure turbine unit whose low pressure elements possess a novel and improved form of blading in which specially shaped stationary and rotating blades are combined in a novel manner whereby the working efficiency of the turbine is substantially increased.

lVith the. steam pressures ordinarily here tofore used it is possible by superheating to the required degree before admission to maintain the steam above the saturation point substantially throughout the greater part of the turbine so thatthe saturation point occurs very late or only in the last stages, but with the higher admission pressures being used the greater part of the low pressure end of the turbine is compelled to work with wet steam unless reheating of the working steam is resorted to. Resuperheating or reheating of the steam is complicated and usually uneconomically effected and therefore in most cases is impracticable. Undue wetness of the steam in the low pressure end of the turbine cannot be avoided with the higher pressures by superheating before admission because superheating cannot be carried at present beyond 4504500 G. with safety. As an example, with steam turbines of admission pressures of 30 atmospheres the steam reaches the saturation point at about 2 atmospheres, and accordingly the whole low pressure part of the turbine working under 2 atmospheres is compelled to function with Wet steam which becomes wetter as the vacuum pressure is reached. The water content of the wet steam tends to lag behind the expanding steam and escapes out of the guide canals with both a diminished velocity and a different direction with reference to the velocity and direction of the steam flow. This lagging water content tends therefore to strike the blades in a manner to exert braking and retarding thrusts thereon, and otherwise impairs the expansive working and efficiency of the steam conveying it. Moreover it is found that an undue water content in the wet steam Zone has a deteriorating and injurious influence on the guide blades themselves, especially if of the usual and ordinary construction, and particularly on the portions of the blades near the periphery of the turbines due to the tendency of the fine water drops or contents suspended in the flowing steam to be driven towards the circumference of the rotating parts b centrifugal force.

I halve found that these objectionable influences may be reduced by properly proportioning the exitangles of the stationary nozzles with reference to the entrance angles of the rotating blades, as for example by diminishing the exit angles of those parts of the stationary blades which guide the wet portions of the steam. The entrance angles of the rotating blades may becorrespondingly changed to assist in avoiding the objectionable influences of the water content, and this is preferably effected by rounding the entrance edges of the rotating blades corresponding to the altered exit angles of the stationary blades. The altered angles of the stationary and rotating blades accommodate the functioning of the turbine to the wet steam. Preferably also the stationary guide nozzle chambers are subdivided radially to reduce turbulence losses and to form an interior chamber for the dryer working steam and an exterior circumferential chamber into which the wet steam tends to flow. V

Fora better understanding of the inven-' tion, reference may be had to the accompanying drawings forming apart of this application, wherein:

Figs. 1 and 2 are explanatory diagrams,

Figs. 3 and 4 are perspective views of the stationary and rotating blades respectively embodying my invention, and

Fig. 5 is a diagrannnatic plan view of the stationary and rotating blades.

Referring to Fig. 1 illustrating a velocity diagram, o represents the absolute velocity of the steam, a the circumferential velocity and a0 is the resulting relative exit velocity of the steam, The water part of the steam which tends to lag behind the steam is represented by *0 which indicates the absolute velocity of the water content and, since the peripheral velocity is the same for both the steam and water contents there is arelative exit velocity to of the water part which difters from the relative velocity u; of the steam in both quantity and direction, showing that the water part does not in the ordinary forms of blading enter the rotating nozzle canals in a thrustl ess manner, but tends rather t strike the blade back and brake or retard the rotation. According to the present invention these objectionable influences are reduced or substantially removed by diminishing the exit angles of the stationary blades with reference to the rotating blades in a radial direction towards the outer circumference in a manner to alter the water flow direction sutliciently to avoid the thrusts upon the bacl: of the blades. Preferably also the corresponding entrance angles of the rotating blades are correspondingly altered, as by gradually rounding the entrance ecges thereof in a radial direction towardsthe circumference.

Referring to Figs. 3, 4E, and 50f the drawings showing an embodiment of my invention, the stationary guide blades (1 are observed to have an exitangle [3 at their extreme outer ends radially or" the turbine near the circumference of the wheel and an'angle it which is substantially larger than the ai'igle ,6 at their inner ends, the angles intermediate the ends varying between the angles [3 and a in accordance with the demands of practice. Preferably the exit angles should gradually and progressively decrease -from the angle a at the inner ends of the blades to the exit angle ,8 at the extreme outer ends. This may be eitected by giving to the blades a a distorted or twisted form from the lower ends to'their outer ends so as to gradually decrease the exit angles toward the circumference. The vector diagram of Fig. 1 may represent the velocities as to dimensions and directions at the inner ends of the blades, where o is the velocity (absolute) of the steam, o is the absolute water velocity, u is the circumterential velocity, '20 is the relative steam velocity (dotted lines) and 10' is the relative water velocity (dotted lines). With the same exit angle alpha (a) at the outer ends of the blades, the relative velocities of the steam and water contacts are represented by the full lines 20 and Q respecti vel-y, the circumferential velocity u at the outer ends being larger than u. .The divergence of the water velocity line is observed to increase as the circumferential velocity increases radially outward, while the wet steam, due to centrifugal force, tends to How outwardly, leaving the dryer steam in the innermost parts of the guide nozzle chambers. The objectionable in .iuences ot the wet steam are therefore more pronounced in the outermost portions of the guide nozzles, the construction exhibited in Figs. 35 obviates to asubstantial degree these objections in that the divergence of the water velocity is gradually decreased in the outward radial direction. Fig. 2 may be used to represent the directions of velocities at the outer ends of the blades embodying my invention, where the exit angle has been reduced from alpha ((1) 01'' Fig. 1 to beta (,8). The relative steam and water velocities are represented by w and 20' respectively, and the reduction of divergence of w is indicated by the angle phi prime e) which is observed to be substantially smaller than the angle phi of Fig. 1. As aboveindicated, the intermediate exit angles vary between alpha and beta with corresponding variations in the other directional angles. In Fig. 2 the direction angle of the relative velocities w and 10 is observed to be smaller than the direction angle indicated in Fig. 1., and ac cordingly the objectionable influences of the water content are thereby substantially reduced particularly in the outer zone of the blades, which works with the wetter steam.

In my construction it is evident that even L though the water content does la g behind the steam, it does not brake the blade rotation but on the contrary strikes the working side of the rotating blades to do work therein. Th performance is still further improved by altering the entranceangles ot the rotating blades also, for example, as shown in Fig. 5 in which the angles a and ,8 indicate that the rotating blade entrance edge angles are gradually increased radially of the turbine towards the outer circumference in correspondence with the alteration of the exit angles of the stationary blading. Such a re sult may be effected, for example,by rounding the rotating blade entrance edges from a distinctly sharp edge at the inner ends to a substantially rounded edge at their outer ends, this rounding ot the blade entrance edges of the blades Z) being gradually increased corresponding to the gradual change in the exit angle of thestationary guide blades (5. This rounding of the entrance edges of the blade 7; is indicated at b, the comparatively sharp inner edge being indicated by 6 The rounding of the entrance edges of the blades 6 cooperates with the reduced exitangles of the stationary blades in eliminating the objectionable influences of the water content of the wet steam and particularly in that it reduces the injurious and destructive influences of the water content upon the rotating blades.

It is desirable to separate the Wetter outer zone of the blades from the inner zone in order to minimize the turbulent or whirling losses due to the tendency of the steam to be whirled outwardly caused by the changing construction of both the stationary and rotating blades. For this purpose I have dividedthe stationary blades into inner and outer zones or chambers which may be accomplished in any suitable manner, as for example by the partitions o suitably secured between the blades. The wet or heavier steam tends to be thrown outwardly by centrifugal force and therefore the outer zone or chambers of the guide nozzles formed by the partitions contain the steam with larger water contents, the dryer and lighter steam flowing through the in ner chambers.

The gradually diminishing exit. angles of the stationary guide nozzles and the gradually altered entrance angles of the ro- Eating blades function efficiently with the wet steam the angles being such that the lagging water content strikes the rotating blades in a manner to perform work and not brake or retard the rotation. The rounded entrance edges of the rotating blades also function to prevent injury by the impact of the wet steam, and this method of altering the angles is simple and economical.

Having thus described my invention what I desire to claim and protect by Letters Patent is:

1. A steam turbine in which the low pres sure or wet zone stationary blades are formed with smaller exit angles towards the outer circumference of the turbine and in which the entrance edges of the rotating blades which function withthe aforesaid stationary blades are provided with varying entrance angles from their innermost ends to their outermost ends.

:2. A steam turbine in which the low pressure or wet zone stationary blades are formed with decreasing exit angles towards the outer circumference of the turbiri'e thereof and in which the entrance edges of the rotating blades are gradually rounded to wards the circumference corresponding to the alteration of exit angle of the stationary blading.

A turbine of the character set forth in claim; 1 wherein the stationary guide blades have a distorted or twisted for1nation to give the varying exit angle.

4. A steam turbine in which the rotating blades in the wet steam zone have entrance edge angles which are gradually increased from their lnnermost ends to their outermost ends for the purpose set forth, and in which the stationary blades functioning with the aforesaid rotating blades are formed so that the exit edge angles at different points therealong vary to correspond with the changes in the entrance edge angles of the rotating blades.

5. A turbine of the characterset forth in claim 1 in which the stationary canals are divided into at least two chambers in a radial direction for the purpose set forth.

6. A steam turbine in which the low pressure or Wet zone stationary blades are formed with exit angles decreasing towards the outer circumference of the turbine and in which the entrance edge angles of the rotating blades are gradually increased to wards the outer circumference in correspondence with the alteration of the exit angles of the stationary blading, for the purpose set forth. g

7. A steam turbine in which the low pressure or wet zone stationary blades are formed with exit. angles decreasing towards the outer circumference of the turbine and. in which the entrance edges of the rotat ing blades are gradually rounded and their entrance edge angles gradually increased towards the outer circumference in correspondence with the alteration of the exit angles of the stationary blading for the purpose set forth. I

8. A steam turbine in which the low pressure or wet zone stationary blades are formed with exit angles decreasing towards the outer circumference of the turbine and the stationary canals between said. stationary. blades are divided into at least two chambers in a radial direction, and inwhich the entrance edges of the rotating blades are gradually rounded and their entrance edge angles are gradually increased towards the outer circumference in correspondence with the alteration of the exit angles of the stationary blading, for the purpose set forth.

In testimony whereof, I have signed my name to this specification.

FRANZ LOSEL. Vitnesses:

CARL L. NEUMAN, J. MICHEL.

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