US2426950A - Rotary pumping apparatus - Google Patents

Description

P. M. RIEDE ROTARY PUMPNG APPARATUS Filed July 1o, 1942 Sept. Z, 1947.

` 11V V EN TOR.

,Feier 1% ede Patented Sept. 2, 1947 ROTARY PUMPING APPARATUS Peter M. Riede, Buffalo, N. Y., assignonto ,The

Linde Air Products Com a corporation oi Ohio Application Juiy10, 1942, Serial No. 450.1381

s claims.

' The present invention relates to a method and apparatus for pumping highly volatile liqueed gases having a boiling point temperature at atmospheric pressure below 273 K.- It is of particular advantage in the pumping of liquid oxygen' which has a boiling point at atmospheric pressure considerably below 233 K.

yIn the transfer and supply of liquid oxygen for industrial use there is a need `for a pump capable of producing pressures of ZOOLpounds and upwards, a desirable operatingl range being from about 100 to 350 pounds per square inch. The capacity of a pump to be used for such purposes should be relatively high as, for example, a discharge rate in excess of 100,000 cubic feet per hour measured as gas at normal temperature and atmospheric pressure. The conditions commonly require intermittent operation and, accordingly, the priming time should be short, and complete automatic operation without more than infrequent attention is very desirable. Also in general the construction should be light weight, compact and simple in order to minimize vaporization and the consequent interference with operation and loss of oxygen material.

The present invention is directed to the `-problem of meeting these and other criteria. It involves the special design of a multi-stage rotar;r pump employing impellers of the character known as turbine type, having aseries of blades at the periphery extending radially inwardlyfor a short distance only, adapted to moveiin an annular channel extending around andoenclosing the bladed periphery for nearly its entirelex'- tent. Of particular importance is the matter-'vof correlation of size and speeds of the impellers both as respects the individual impellers and-their relation to each other, whereby there isffacco'mplished an efilciency and dependability-of operation in connection with the handling o ffgliquefled gases exemplified by liquid oxygen which, it is believed, has not heretofore been attained.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly :comprises the several steps and the relation of one ormore of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts which are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of which invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had pany, New*v York; N. Y.,

to the following detailed description taken in con'-v` nection with the accompanying drawing,y in which:

Fig. 1 is a view in elevation of a pumpand power operating means representative in general of the invention;

Fig. 2 is a cross-sectional view in elevation showing details 'of the pump interior, including in particular the rotary impellers; and

Fig. 3 is an irregular cross-sectional view of the pump casing taken on the line 3.-3 of Fig. 2 but with the rotary parts omitted. y

The results of my discoveries forming the sub..- ject matter hereof are exemplified in the drawings showing a l.multistage pumping means employing impellers of the turbine type, the sizes -and speeds of operation of which and their relation to each other will be discussed hereinafter. 1n a pump of this character it has been found that by proper correlation a major increase in pressure may be attained in a second stage which isi considerably greater than that possible in the first stage of such a pump or in a single stage pump of similar character. That is to say, the rise in pressure possible in thesecond stage is far inexcess of the rise in pressurein the first stage. this is more specifically illustrated-by the fact that although the maximum pressures obtainable under normal conditions with a single stage pump of the type here considered are materially less than 100 pounds per square inch; yet` a two stage pumpl constructed and operated in accordance witir'the principles of vtheinvention will produce pressures of 350 pounds'and upwards. The values given are for liquidoxygenf?v The rise .in pressure in the second stageand lthe..maximum final pressure are, however, dependent upon the character of the first stage as wellfas that?. of the second stage. It has been discovered thatwithin reasonable limits of impeller diameter'the best f results are obtained when the peripheral speeds of the impellers are maintained 'within'h certain limits, respectively, and that the peripheral speed ofthe high pressurestage; should be considerably greater than that of the low pressure stage.

Continuing with the statement of conclusions in this respect it has been found that the objectives may be attained in a pump` having a first stage impeller of the type heretofore noted operating at a, peripheralspeedge'n'erally within the range of 2,000 to 3,000'fet-per minute; and a second stage having a similar type impeller operating at a peripheral speed in the range of about 3,200 to 4,500 feet per minute. In general the peripheral speeds are preferably such that the peripheral for.` the first v,of 350 pounds -per speed of the second stage impeller is about one quarter to one-half greater than that of the first stage impeller.

As a specific example of results obtained, two turbine type pumps separately driven but coneach being six inches in diameter. The optimum and about 2,700 R. P. M. for the second stage, which, in terms of peripheral speed. may be expressed as approximately 2,500 feet per minute stage and 4,200 feet per minute for the 'secondfstaga Peripheral speeds for the first stage overa range of approximately 2,000 to 3,000

gave good results, although not quite as good as withln .therange-or about 2,200 to 2,830 feet Der minute (1.400100 1.80.0 R. P..M.

w With the first stage pump operatingat 1600 R. P. M. good results were "obtained over4 a.fai rly wide range of speeds of the high pressure stage', the optimum however being, as stated, around 2,700 R, P. M.,

which gave a; discharge pressure of well over 300 l poundsper 'square inch,y The delivery rate varied with the pressure but was relatively high throughout the range of pressures tested.

In a turbine pump arrangement employing a low pressure impeller abouteight inches in dlameter, the optimum Vspeed wasA about 1,200

` R. P.A M. which gives the same peripheral speed as that of a six inchdiam'eter impeller operating at 1,600 R. P. M. Vreferred `toabove.'

vide a moderate pump intake pressure such as that o: a head provided by an elevated supply .nected in series were operated, the impellers of The general principles and' conclusions may be illustrated by other examples. Witha six inch diameter rst stage impeller and an eight inch diameter for the higher pressure stage with both impellers operating at 1,750 R.,P. M., a pressure square inch was easily attained.

As heretofore noted, a range oi! peripheral speeds for the second stage may be given as generally between about y ute, although-a preferred range would comprise 3,200 and A4,5500 feet per minabout 3,600 to 4,200 feet per minute. Thediameter for the first stage impeller should be preferably in the range of nve to nine. inches, and for the next or higher stage a dlameterin the range of six to ten inches. These diameters c ontern plate, oi course, appropriate R..'P. M. respectiv e1y, and when both impellers aremounteid 0n the same shaft the impeller for the higherpressure stage will be larger than that, of the low prwsjur'e stage. r 1 1 It will be understood that the pressureslm'entioned are with liquid oxygen having a relatively' low viscosity. It will also 'be understood that lf still higher ultimate pressures are desired further stages may be added, and that the values and description given herein refer to the nrst two stages of a-pump.

In the drawings there is depicted a speciilc arrangement illustrative of the principles of the invention. It comprises a two-stage turbine type pump with both impellers mounted on the same shaft but of unequal diameter to result in different peripheral speeds for the two stages. The general arrangement as shown in Fig. 1 includes a. pump I0 having a tubular extension sleeve II for the drive shaft with an outer seal I2. The drive shaft I3 is provided with a suitable outboard bearing shown generally at l I4 mounted on a supporting bracket I5. The source of power is indicated as an electric motor It connected directlyA to the'pump shaft I3 by a suitable coupling I1.

An intake to the first stage is shown at 2l, which for good results on` liquid oxygen will be connected to a source of supply adapted to pro;

peller tank giving a gravity flow of liquid to the pump inlet. The liquid is discharged from the first stage at the outlet 2i from which it is led through pipe 22 to the inlet to the higher pressure stage and is discharged from there at the outlet 23.

Referring now to Fig. 2, the pump has a main casing 25 provided with a cover plate 26 at the left end, and a further cover plate 21 at the right, each of these cover. plates being secured in place by suitable means such as .cap screws. The end plate 26 is provided with an extending tubular portion 28 in which is secured the shaft enclosing sleeve II. The end plate 21 also has an enlarged tubular extension 29 enclosing the inner end of the drive shaft, a small plate 30 being secured to the outer end of the extension 29 by suitable means such as cap screws to provide a tight seal.

The specific drive means and the bearing ar` rangements may be varied. but that shown illusv trates one having particular advantages with respect tothe avoidance of leakages and reduction of friction and vapor-ization of the liquid oxygen. As specifically shown, the shaft I3 lis provided with a portion having splines 32 adapted to drive the low pressure stage impeller 34 and thehigh slidable as to each of the impellers, the latter being designed to float thereon independently of each other.

As heretofore noted, the impellers are of the turbine type having blades arranged at the periphery designed to operatein pumping channels extending for nearly the entire circumference 'of the respective impellers and, accordingly, the im- 24 is provided with milled out slots 4I, there being similar alternate slots on each side of the ller adapted to propel the iluld through the `channel l2 located in the main housing part at.

Similarly the impeller 35 is provided with milled out slots 43 on the opposite sides of its peripheral portion, which operates in the pumping channel vll. The milled out slots are such as to result in suitably spaced vanos or blades arranged in accordance with impellers of this type.

In Fig. 3 thereis shown a broken away view in cross-section of the pumping channel of the low pressure stage. It is important to avoid turbulence or undue restriction particularly in the inlet to the first stage and accordingly as shown in Fig. 3 the inlet to the pumping channel for the ilrst stage is of smooth contour and of gradual reduction in size. A similar shape is preferably employed at -theoutlet. As shown in Fig. 3, the

pumpingchannel 42 is provided with a partitionl 44a suitably shaped in accordance with the provision of a smooth inlet and outlet, and which also serves the purpose of dividing the outlet from the inlet, the partition a comprising in substance a raised flat portion projecting toward the lateral face of the bladed portion of the impeller ll. The end plate 28 is provided with a similar channel and partition part complementary to the channel I2 and partition part a shown in Fig. 3.

.similar to that the two impellers it may I'he outer edge of the channel 42 is drawn inwardly at the region 42a so that with the projecting portions is reduced to substantially the size of the bladed portion of the sandths of an inch clearance. The arrangement of the high .pressure stage' pumping channel isof the low pressure stage iliustrated, except being displaced in general 180 degrees therefrom.

The hub portion 36 of the impeller 34 is located between two bearing rings 46 and `41 which determine the axial position of the impeller, the hub having a slidable iit on the splined shaft whereby the impeller in eiTect floats lthereon.l The bear- -ing ring 4B at the left is located in and supported by the cover plate 26 and the bearing ring 41 at the right is carried by the ring 68 which is threaded into an annular recess inthe main housing 2,5.

The axial position of the impeller 34 may be adjusted through adjustment of the ring v48 and by the use of annular shims wherever appropriate, as adjoining one or both of the bearing rings 46 and 41. and also if desired at the point 49 between the main housing 25 and the end plate 26.

As heretofore noted, the impeller 35 is rotated through the spline connection with the drive shaft I3 but similarly to the impeller 34 is designed to float freely thereon in an axial direction. Fitted within the tubular extending portion 29 of the end plate 21 is an annular bearing sleeve 5I which serves as a radial support for the impeller sleeve 31 and in turn forms an inner radial bearthe drive shaft I3. The annular ing support for bearing sleeve mentat one is secured against endwise moveend by the ring 52 secured in the housing part 25 by suitable means as by 'the screws 63 and at the opposite end by the annular sleeve 54 formed on the end cover plate 30. i

'I'he impeller 35 bears at the left against an.

annular thrust bearing ring 56 located in a supporting ring 51 threaded into an annular recess right-hand sideof the hub to the left against the thrust bearing 44a the .channel at 'this region impeller with-but a few-thou- 5I of a character which are self-lubricating, not requiring the application of any auxiliary lubricant, such Vas hydrocarbons, fromtheqexterior. Also the material employed for the bearings is inert to liquid oxygen. A bonded graphite ywhich may be impregnated, if desired, with suitable-materials has been .found especially effective for the purpose describe Y.

'Ihe sealing means against leakage of, oxygen material is located at I2 at the outer end of the extended sleeve II. The specific construction of the seal may -vary anddetails are not disclosed herein, but in general it may advantageously be of the type employing an expansion bellows' engaging against al bearing ring of a material similar to the thrust bearing rings located on the interior of the pump housing. With the arrangement illustrated the leakage of heat into the pump is reduced to a minimum and the rubbing parts of the seal may be kept reasonably warm.

The pump impellers are of a diameter and the intended speed of operation are in accordance withv the values and relation to each other described in the early part hereof. A particularly efiicient arrangement is one employinga 10W pressure stage impeller 34 having an outer diameter of about six inches and a high pressure stage impeller having an outer diameter of about nine inches. With a standard electric motor having a direct drive connection to the pumpv shaft I3, operated at 1,750 R. P. M., thelow pressure l impeller will have a. peripheral speed of about his se, which has the combined result of maintaining! thrust bearing ring 56, and, in addition, the engagement of the surfaces eiiects a seal against leakage of the liquid from the high pressure stage into the low pressure stage. Axial adiustmay be effected by adment of the impeller 35 Justment of the ring 51 or by the use o1' shims on either side of the thrust bearing 56.

In 'connection .with the axial adjustment of a running nt between these two rib parts, a clearance of a few thousandths of an inch being provided on each side. The impeller 34 is similarly positioned between the ribs 62 and' 83.

It will be noted that the inner end of the shaft 2,750 feet per minute and the high pressure impeller will have a. peripheral speed of about 4,1254feet per minute. Such a pump is capable of delivering liquid oxygen at pressures well above 300 pounds per square inch if necessary. Its capacity is also relatively high within pressures o normally required.

ASince certain changes in carrying out the above method and in the constructions set forth. whichmay be made without deembody the invention l v'parting from its scope, it is intended that all matter contained in the above description or shown in the accompanying ydrawing' shall be interpreted as illustrative and not in a limiting-sense.

Having. described my invention, what I claim as new and desire to secure by letters Patent. is: l 1. Ina multi-stage rotary pumping means for 'pumping liqueiied gases having a boiling point ati atmospheric pressure below 273 K.. having stages of relatively low and high pressure suitably connected by fluid conduits, a rotary impeller of the turbine type with bladesv at the periphery thereof foreach of said stages, a 'driving shaft. said impellersv being axially spacedv thereon,- casing means pumping channel for' providing an annular fluid diameter oi' .the impeller and its channel for the high pressure stage being substantially greater than that of the lower pressure stage and said high pressure impeller having thereby a greater Peripheral speed.

V2. In a multi-stage rotary pumping means for pumping liquefied gaseshaving a boiling point at atmospheric pressure below 273 K., said means impellers being mounted in axially spaced rela' each impeller enclosing the bladed peripheral portion thereof respectively, the

immenso tion on said an annular huid pumping channel for each impeller enelosing the bladedperipheral portion thereof respectively, the diameter oi thelow pressure impeller and the speedl of the driving'means having stages of relatively low and high pressure suitably connected by tiuid'conduits. a rotary impeller oi the turbine type with blades 'at the periphery thereof for each of said stages, a driving' shaft -with power relation on said shaft. and easing means prothe 'blade'd peripheral portion shaft. and easing means providing iswithintherangeof2,000t0` means for operating it, saidsimpellers being mounted in axially spacedl 'viding an annular iluid pumping channel for each impeller enclosing B thereoi respectively. the diameter of the low pressure impeller and the speed of the driving means heini auch that the peripheral speed of the low pressure impeller is within the range oi 2,000 to 3,000 feet per -high pressure minute, and the diameter ot the impeiler being sumcientiy greater than that of the lower pressure stage to provide a peripheral speed withinv the ranse of 3,200 t0 4,500 feet per minute.

prima u. nrs-.Dn

permanences 4crm-:n

The following references are o! record in the ille of this patent:

UNITED s'rsrss PATENTS Number Name Date Micheli Mal. 3, 1914 Kirgan Sept. 15, 1931 Leopold et al. Oct. "I, 1941 Holmes July 12, 1927 Gilrl'ey -4.--- Sept. 23, 1941 Gurley June 15,1943

Images