US2355413A

US2355413A - Elastic fluid turbine blading

Info

Publication number: US2355413A
Application number: US427601A
Authority: US
Inventors: David J Blcomberg
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-01-21
Filing date: 1942-01-21
Publication date: 1944-08-08
Anticipated expiration: 1961-08-08

Description

1944- D. J. BLOOMBERG 2,355,413

] ELASTIC FLUID TURBINE BLADING Filed Jan. 21, 1942 P: A; r /6 Inventor:

i-jig Atto rn ey.

m. M David J. Bloombehg Patented Aug. 8, 1944 i i i David J. Bloomberg, Newton, Mala, assignor to I .General Electric Company, a corporation oi New York Application January a1. 1942, Serial No. 427,601 6 Claims. (c1. ass-r7) The present invention relates to elastic fluid, turbine blading, more specifically to blading oi rotary bucket wheels. In elastic fluid turbines designed for constant speed and pressure condi- -tions ithas been the practice heretofore to provide bucket blades substantially crescent-shaped in cross-section and with constant entrance angle along their entire length except in the case of bucket blades used for low pressure turbine stages where in certain instances it has been customary to take into consideration the diflerence between the rotationalspeed of the'outer'and in-. nor portions of such buckets and varythe entrance angle accordingly. It has been found that aside from differences indiflerential speed present arrangements of turbine blading do not take into consideration changes in elastic fluid velocities due to friction at-the inner and outer walls of nozzles for directing elastic fluid towards the bucket blades. The buckets ordinarily aredee signed to attain best emciency with regard to the elastic fluid velocity obtaining in the central ormajor portion or the nozzles.

The objector my invention is to provide an for best efliciency with'regard to the elastic fluid velocity existing near such portion.

For a consideration oi what I believe to be novel and my invention, attention is directed to the ijollowing description and the claims appended thereto in connection with the accompanying the.

phragm it in the present example overlap with the bucket I! of the bucket wheel l0.

Adjacent partitions II form nozzles or passages for properly directing elastic fluid from one bucket wheel to a succeeding bucket wheel. The velocity of elastic fluid passing through a nozzle formed between partitions II is approximately constant over an intermediate portion oi. the norzle area between the inner and outer diameters extending over a length of about 80% or the entire length of the partition ii. The velocity near the inner and outerportions of the nozzle decreases due to friction along the end walls oi the nozzle and other sources of losses and becomes in zero at the end wall. In Fig. l the dot-and-dash line 20 is atypical velocity curve plotted over the radial length of anozzle between the inner and outer diameters. The velocity in for the intermediate portion oi the nozzle, as stated above,

20 issubstantially constant. The velocity or for the end portions of the nozzle decreases from m to zero at the nozzle wall.

In the velocity diagram oi Fig. 2 the vector to designates the wheel speed. The vectors v1 and improved construction or elastic fluid turbine 25 v: designate average velocities oi the elastic fluid bladingwhereby each bucket portion is designed in the intermediate portions and the end portions respectively 0! the nozzle. The resultant of the vectors to and or is an and its angle towards the horizontal, that is the angle at which elastic fluid m is discharged iromthe nozzle and enters the bucket passages, is designated with an. The resultant oi the vectors to and or is designated with as. Its angle towards the horizontal is as. In

. order to obtain best eiflciency for an elastic fluiw In the drawing m 586mm as velocity an at an angle a: the bucket blade shoui.

7 view; partly broken away. oi. an elastic fluid turbine embodying my invention: Fig. 2 is an explanetary view; Figs. 3,5 and 7 are perspective views of three modifications according to my invention: and Figs. 4, 6 and 8 are top views of the bladesin Figs. 3, 5 and 7 respectively.

The arrangementin Fig. 1 comprises a bucketv wheel it! having a ring or disk H with a plurality of circumierentlally spaced buckets I! attached thereto. The blades of the buckets I! will be described hereafter. During operation elastic fluid is directed towards the bucket I! by anozzle dig aphragm I3 and the elastic fluid discharged from the bucket wheel is passed to anotherbucket wheel through the intermediary oi another nozale diaphragm it having a plurality of circumi'erentially spaced partitions I! held between an inner disk It and an outer ring I1. The diaphragms It and are supported on an outer casing or shell I. The partitions of the dia- II have an entrance angle equal to all. Such a bucket blade is indicated in Fig. 2 in cross-section by reference numeral II. with such cross-section best efliciency is obtained with regard to the indil termedlate portion only of the nozzle. In order to attain similar good emciency for the reduced esteem velocities near the end portions of the bucket blade I provide these end portions with entrance angles as. In Fig. 2 I have shown with in regard to the vector 2:; a cross-section 22 oi a 60 ing from the crossseetion tito the cross-section II. The cross-section 2| has a sharp inlet edge with an entrance angle a1 while the cross-section 22 has a rounded inlet edge with an entrance an gle as. The provision of end portions with larger entrance angles is particularly efl'ectlve in case of buckets overlapping the partitions from which they receive elasticfluid as indicated in Fig. 1 withregardto the buckets l2 and the partitions of the diaphragm l3.

The bucket in Figs. 3 and 4 comprises a base 23 with a blade 24 secured thereto. The blade 24 has an intermediate portion 25 which is crescentshapedand has a cross-section corresponding to the cross-section 2| Fig. 2. The blade 24 has a portionv 28 at each end which has a cross-section merging from a section corresponding to that 01 2| in Fig. 2 towards a section or end race 21 corresponding to the section 22 in Fig. 2.

- an entrance angle larger than that 01' the inter- As indicated in Fig. 4 the entrance edge 28 oi! the bucket. is uniformly spaced along its entire length from the center lineof the bucket. thev spacing being indicated by the reference character 29. The blade arrangement as shown in Fig. 3 is very efficient but requires more machining due to the increasing thickness of the entrance portion near the ends of the blade relative to theintermediate portion.-

The arrangement in Figs. 5 and 6 requires littie additional machining as compared with that of an ordinary blade with uniform entrance angle along its entire. length. The bucket of Fig. ,5 has. a blade 30 secured to a base 3|. The crosssectionof the blade is essentially crescent-shaped along its entire length, as shown in Fig. 6. End portions of the entrance edge I2 of the blade are.-;cut away, thus providing a portion with an entrance angle gradually increasing from the mediate portion.

2. A turbine blade of the kinddescribed, which blade has an intermediateportion with a sharp entrance edge Iorminga uniform entrance angle for elastic fluid and a portion at each end with an entrance edge increasing in thickness towards the end and-forming an entrance angle increasing from vthatof the intermediate portion towards the end. i

3. A turbine bladeoi the kind described which has an intermediate portion essentially crescentshaped, in cross-sectionand havinga sharp inlet edge with .uniformsentrance angle, and an entrance portion at eachaend which has a crosssection equal to a part of the cross-section of the I intermediateportionwithpartsnotboth end porangle-p1 (Fig. 6) for the intermediate portion to the angle ,8: for the outer ends of the end portions. The spacing of the inlet edge, of this bucket from the center line is not uniform, however. At the outer ends the blade is spaced from the center line by a distance 33 which is less than the spacing 34 for the intermediate portion.

a bucket with a blade 35 fastened at its inner end to a base 36. The blade has an intermediate portion 31 extending over at least 80% of the entire length of the blade and being essentially crescent-shaped in cross-section. The blade has end portions 38, each having a length of less than 10% of the entire length of the blade. These end portions are gradually bent backward in the direction of rotation on the inlet side with regard to the intermediate portion, as shown in Fig. 2. The entrance edges of the end portions are-cut away so that the entrance edge of the entire blade is uniformly spaced from its center line.

tions near-the inlet edge-being gradually cut away in order to form entrance angles gradually increasing from that of the-intermediate portion towards the outer ends of the endportions.

4. A turbine blade of the kind-described which has an intermediate portion substantially crescent-shaped in cross-section and forming a constant entrance angle and'a portion at each end also substantially crescent-shaped in cross-section and, having an entrance angle which increases from the inner end of such end portion towards its outer end.

5. In a turbine, a diaphragm having a plurality of circumferentially spaced partitions and a bucket wheel having a plurality; of circumIerentially spaced buckets with end portions overlapping corresponding. end portions of the partitions, both end portions of each bucket near its entrance edge beingcut away and forming entrance anglesfor elastic fluid largerthan the entrance angle of the intermediate bucket portions.

6. A turbine blade of the kind described, which blade has an intermediate portion with a sharp entrance edge and a portion at each end bent back in the direction of rotation with regard to the intermediate portion .to form entrance angles increasing towards the outer ends of the end portions.

DAVID J. BLOOMBERG.