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Патент USA US2405284

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R. BIRMANN
vG'ENTRIFUGAL COMPRESSOR
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Filed May 21, I942
2 Sheets-Sheet 1
24
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INVENTOR.
BY
ATTORNEYS
Hg. 6; 3%4.
‘ R. BIRMANN
2,4052
vCENTRIFUGAL COMPRES SOR
Filed May 21, 1942
2 Sheets-Shéet 2
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V
INVENTOR.
1 BY QM, , @17
ATTORNEYS
Patented Aug. 6 1946
2,405,284
UNITED STATES PATENT OFFICE
‘ 2,405,284
. CENTRIFUGAL COIVIPRESSOR
Rudolph Birmann, Newtown, Pa., assignor, by
mesne assignments, to Federal Reserve Bank
of Philadelphia, a corporation of the United
States of America
Application May 21, 1942, Serial No.443,9>57
1
17 Claims. ' (Cl. 230-130)
This invention relates to centrifugal compres
sors, and has particular reference to the con
struction and mounting of impellers therein.
The mounting of impellers operating at very
high rotational speeds involves various dif?culties,
particularly in the case of mounting on a com
mon shaft a plurality of impellers providing suc
cessive compressor stages. For example, when
such impellers are directly driven at the speed of
2
439,569, ?led April 18, 1942. As described in said
application, the impellers are designed to be di
rectly driven by a turbine at very high rotary
speeds.
'
'
?led May 4, 1942, though it will be obvious that
the invention is applicable to impellers of sub
stantially
different design. In accordance with
a gas turbine, they may operate substantially 10
the disclosure of the last named application, and
above the critical speeds for the rotating parts,
also in accordance with my application Serial No.
and provision for ?exibility is essential. Fur
407,408,
?led August 19, 1941, each impeller is
thermore, provision must be made to take care
made
in
two
parts, both to permit easier machine‘
of expansion, either due to temperature changes
ing and to effect the damping of vibrations which
involved in the compression of air, or the heating 15 may
be set up in the impeller blading during op
up of the compressor by reason of its position ad
eration. Accordingly, the impeller 2 comprises
jacent to a combustion turbine, combustion cham
two sections Ill and I2. The outlet section ID of
bers, internal combustion engines, or the like.
this impeller'is integral with the inlet section M
For high speed operation, and particularly in
of the next impeller 4, which is provided with a
the case of aircraft construction where weight 20 separate outlet section l6. Similarly, the im
must be kept at a minimum, it is essential that
pellers 6 and 8 are made of separate sections I8
the impellers should be made 'of light aluminum
and 20 in the one case and 22 and 24 in the
or magnesium alloys or the like,‘ which inthem
other, the sections l8 and 22, namely, the out
selves do not have su?icient strength orrigidity
let section of impeller 6 and the inlet section of
to permit the complete elimination of all parts 25 impeller
8, being integral as illustrated. In order
of steel construction. It is one object of the
present invention to provide a compressor con
'
Each of the impellers is preferably of the type
dsecribed in my application Serial No. 441,686,
to hold the two sections of the impellers in angu
lar alignment, the impeller sections are splined
struction to avoid the di?iculties above mentioned
upon tubular members 26, 28 and 30. These tu
and particularly to enable the assembly of light
metallic impellers with shafts or aligning mem 30 bular members may be conveniently referred to
as shaft members, though it will be noted here
bers of steel.
/
after that, except for 28, they do not function as
' The above and other objects of the invention,
true shafts from the standpoint of taking care of
particularly relating to details, will become‘ ap
lateral bending forces, having merely the func
parent from the following description, read in
tion of aligning the respective impeller sections
conjunction with the accompanying drawings, in
to which they are common and to transmit torque
which:
in addition to providing ?anges to aid in securing
Figure 1 is a fragmentary axial section through
the impeller sections together.
’
a multiple stage compressor embodying various
The
construction
involved
in
the
case
of
all
of
features of the invention;
the
shaft
members
26,
28
and
30
will
be
best
un
Figure 2 is a fragmentary transverse section 40 derstood from considering the section of Figure
taken on the plane indicated at 2-2 in Figure 1;
2, which shows the impeller section 20 provided
and
with
internal teeth engaging the external teeth
Figure 3 is a section generally similar to Figure .
1 but showing an alternative arrangement em
of the shaft section 28 as indicated at 32. These
common axis and forming the successive impel
lers of four compressor stages. The type of com
pressor illustrated is particularly designed for an
internal combustion power plant of the type de
it is splined. The various impeller sections car
ried by the shaft member 28 are connected in
pairs [4, l6 and I8, 20 by means of bolts 34 and
35, the heads of which engage, and are sunk into
are, to secure maximum strength, pref
bodylng features of the invention designed partic 45 teeth
erably of internal and external gear form of sub;
ularly for the assembly of two adjacent impellers.
stantially the same pitch diameter so as to form
Referring ?rst to the modi?cation of Figures 1
a close ?tting spline arrangement preventing any
and 2, there is indicated therein, in fragmentary
substantial relative‘ rotation between the shaft
form, a centrifugal compressor having four im
member and any of the impeller sections to which
pellers 2, 4, 6 and 8, rotating together about a
countersinks in, ?anges 36 and 38 carried by the
scribed, for example, in my application Serial No. 55 shaft
member 28. The bolts 34 and 35, of which
2,405,284.
3
4
parts thereof; and since the stationary casing
there are suificient to produce the necessary con
tact pressure between the impeller sections are
has an expansion also measured by the expansion
of the alloy involved in its construction, the
clearances all along the shaft remain substan
arranged about the axis and are preferably of the
“Aero-thread” type commonly used for the se
tially constant, the spacing between the ?anges
curing together of light metal alloy parts, though
36 and 38 being insufficient to disturb to any sub
if circumstances permit, any suitable type of bolt
stantial degree this correspondence of expansi
may be used for this purpose. The particular
bility at all points along the axis.
type of bolt referred to is described in Patent
In the case of the modi?cation of Figure 3,
2,150,876. Similar bolts 40 and 44, having their
is involved an alternative construction em
heads engaging, and sunk into, ?anges 42 and 10v vthere
bodying some of the same general principles in
46 on the shaft members 20 and 26, respectively; :
volved, in the previousmodi?cation. In the case
serve to hold together theimpeller. sections 10
of ‘this modi?cation, there are shown two im
and I: on the one hand and 22 and 24 onthe ' 7 pellers '55 and 58, which may be used as the sole
The mounting of the assembly which has been 15 two stages of a compressor, or may form a pair
of stages of, for example, a four-stage com
described comprises three bearings, the housings
pressor of the type illustrated in Figure l,
of which are indicated at 48, 50 and 54. The bear
in which case their shaft would be continued on
ing 48 surrounds the central portion of the
the other side of a central bearing. The impeller
shaft member 28, the parts thereof being split for
56 comprises the two sections 6!] and 52, while
assembly about this member. The bearing with
the impeller 58 comprises the two sections 54 and
in the housing 50 mounts the shaft member 25,
66. In each instance, one of these sections is
while that within the housing 54 mounts a shaft
undercut
in accordance with the disclosures of
extension 52 secured to the impeller section 24.
said applications Serial Nos. 407,408 and 441,686,
It will be evident from the foregoing descrip
referred to above. Between the impeller sections
tion that a strong ‘impeller assembly is provided,
613 and 66 is a ‘separating member 68, which has
between the various separate parts of which
the surface thereof formed to cooperate with a
torque is transmitted through the steel tubular
?xed member ‘E0 to provide labyrinthine packing
shaft sections such as 26, 28 and 30, described
other.
_
>
above, avery strong construction being provided
by the use of external and internal gear teeth
having close sliding ?ts with each other. The
various connecting bolts are relieved by the splin
ing arrangement from the transmission of torque
and serve solely to draw the various impeller sec
tions together._ ‘These connecting bolts are
threaded to an initial tension condition to pro
vide an axial pressure between the impeller sec
tions exceeding any tension forces that may exist
. between the stages. The sections 68 and 62 are
held in angular alignment by means of a series
of bushings spaced about the axis, one of which
bushings is indicated at 12, these bushings being
driven into aligned openings in the adjacent
faces of the impeller sections. Similar bush
ings ‘M hold in angular alignment the impeller
sections 64 and 66. The angular alignment of
the impeller sections so maintained are, of course,
suchas to cause the impeller vane surfaces to be
substantially smoothly continuous from one sec
between the separate sections of‘e‘ach impeller
tion to the other.
due to the lateral bending or ‘deflection of the
ing that the impeller sections do not part from
each other during operation. Byfu'ndercutting
the meeting edges of the vanes, as described in
said application Serial No. 407,408, referred to
above, an elastic contact between the impeller
vanes is secured.
’
.
.
'
A steel shaft v‘i6 is splined at 18 to the various
impeller sections and to the intermediate member
58, this splining being the same as that involved
in the previous modi?cation and illustrated spe
Joi?cally in Figure 2. This splining, as before,
serves to transmit torque to the various impeller
sections and so substantially relieves the bushings
‘I2 of torque transmission, the spline teeth. being
in accurate alignment when the bushings are in
rotor, i. e., the boltshave the function of insur
'
In'the compressor construction illustrated in
Figure 1‘,_the stationary casing and the impellers
are made of either the same aluminum or other hi)
place.
Threaded on the right hand end of the shaft
16 is a ring 80, which is turned to a position such
that rods 82, having close ?ts within the bush
be evident that if this is the case, except for the
ings l2 and ‘M and extending through aligned
steel shaft members which have been described,
openings in the various'impeller sections and. the
the’ expansion characteristics of the casing and
member 68, may be threaded thereinto. The left
the rotor as a Whole should be substantially the
hand ends of these rods are provided with‘ nuts
same, so that clearances betweenv the rotor parts
84 which are located in countersinks in. the im
and'the stationary casing parts would remain
peller section 62 and are tightened to draw the
substantially constant. This, it will be obvious,
will‘ be the effect of having the expansions of the (it various rotor parts together to the necessary de
light alloy,‘ or of different alloys having substan-_
tially thev same c'oe?‘lcients of expansion. It will
gree.
various light alloy partsof the rotor measured
from the flanges carried by the steel’shaft mem
bers 26, 28 and 30. For example, it will be evi
dent that if ‘the ?ange 36'be considered as the
origin for the expansion ofv the portions to the
left thereof, the axial movement of the ?ange 42
will be essentially that‘ resulting from the ex
pansion of the impeller sections between thesev
?anges. Likewise, this will be true in the 'case
of the movement of the flange 46 with respect to
the ?ange >38. . It will be evident,‘ therefore, that,
except for the expansion of the short length of
steel shaft between the ?anges 36 and 38, the
amount cfvexpansion'of" the rotor is measured
The shaft 16 is mounted in bearings within the
housings 86 and 88, respectively.
(if)
'
In the modi?cation just described, the, rods
82 are desirably formed of the same material as
the stationary casing, for example of magnesium
alloy. Under such conditions, if the bearing 88
is a thrust bearing (for example, of the type dis
closed in my application Serial No. 408,787, ?led
August 28, 1941), it will represent the ?xed origin
for the expansion of both the rotor and the cas
ing. , Since it .is adjacent the threaded ringv 80‘, it
will be evident that the movement of the nut 84
with respect thereto will be substantially com
solely by the expansion of the aluminum alloy 75 pletely defined by the expansion of the magne
2,405,284
sium' alloy rods 82 and will correspond to the
movement of the portions'of the casing having
the same position. along the axis as the nut 84.
Thus the various stationary and rotary parts are
so maintained that the clearances remain essen
tially constant, this being particularly true in
view of the fact that the aluminum .alloy im
peller parts will also have a coef?icent' of ex
pansion less than, but approximately that of
ber, and a pluralityof elongated axially-extend
ing members, one end of each of said elongated
members engaging said shaft member at a loca
tion adjacent said bearing and at its opposite
end engaging said rotor to limit axial movement
of the rotor relative to the shaft member, said
rotor having a coef?cient of thermal expansion
approximately the same as that of said casing.
5. A compressor comprising a casing, a hear
the magnesium alloy rods 82. The spacer 68 is 10
ing within the casing, a shaft member mounted
preferably of magnesium alloy to get a maximum
in said bearing, a rotor splined to said shaft
expansion throughout its length. As expansion
member, said rotor and shaft member having sub
takes place, the pressure gradient across. the im
stantially different coefficients of thermal ex
peller assembly will cause. the impeller sections to
pansion, and axially extending means secured to
slide to the left along the shaft in the same di 15
the shaft member at a single axial location ad
rection as the casing expands, imposing tension on
jacent said bearing and engaging the rotor at a
the rods 82.
_
substantial
distance from the bearing to limit
As an alternative to the arrangement of Figure
axial movement of said rotor relative to the shaft
3, but functioning in the same fashion, a tubular
member.
expansion member made from magnesium alloy 20
6..A compressor comprising a casing, a bear
may extend lengthwise within the hollow shaft,
ing
within the casing, a shaft member mounted
being locked to the shaft at one end at or near
in said bearing, a rotor mounted on said shaft
the thrust bearing, with its other end arranged
member, said rotor and shaft member having
to take the axial thrust of the sildeable rotor
elements, i. e., the impellers and spacers. In such 25 substantially different coefficients of thermal ‘
expansion, and axially extending means secured
case, for example, the inlet face of the impeller
to the shaft member at a single axial location ad
section 62 would be connected to the expansion
jacent said bearing and engaging the rotor at a
tube by means of pins or keys extending in
substantial distance from the bearing to limit
wardly from the impeller section through slots
axial movement of said rotor relative to the shaft
in the shaft into the tubular expansion mem 30 member.
‘
ber.- Such arrangement has the advantage of
-7.
A
compressor
comprising
a
casing,
a
bearing
avoiding the necessity for having any openings
extend through the impeller hubs.
-
within the casing, a shaft member mounted in
said bearing, a rotor splined to said shaft mem
What I claim and desire to protect by Letters
ber, said rotor and shaft member having sub
Patent is:
35 stantially different coefficients of thermal ex
l. A compressor comprising'a casing, a bearing
pansion, and a plurality of axially extending rods
within the casing, a shaft member mounted in
distributed about the axis of rotation, each of said
said bearing, a rotor comprising at least one im
rods being secured at one end to the shaft member
peller splined to said shaft member, said rotor
and shaft member having substantially different 40 at a single axial location adjacent said bearing
and at its opposite end engaging said rotor un
coefficients of thermal expansion, and a plurality
der tension to limit axial movement of said rotor
of rods, each of the rods being secured to the shaft
relative to the shaft member.
member at a location on the high pressure side
8. A compressor comprising a casing, a hear
of the impeller, extending to the low pressure
ing
within the casing, a shaft member mounted in
side of the impeller, and at the latter side en 45
said bearing, a rotor mounted on said shaft mem
gaging the rotor to limit axial movement of said
ber, said rotor and shaft member having substan
rotor relative to the shaft member.
tially
different coef?cients of thermal expansion,
2. A compressor comprising a casing, a bear
and a plurality of axially extending rods dis
ing within the casing, a shaft member mounted
in said bearing, a rotor comprising at least one 50 tributed about the axis of rotation, each of said
rods being secured at one end to the shaft mem
impeller mounted on said shaft member, and a
ber at a single axial location adjacent said bear
plurality of rods, each of the rods being secured
ing and at its opposite end engaging said rotor
to the shaft member at a location on the high
under tension to limit axial movement of said
pressure side of theimpeller, extending to the
low pressure side of the impeller, and at the lat 55 rotor relative to the shaft member.
9. A compressor comprising a casing, a hearing
ter side engaging the rotor to limit axial move
within
the casing, a shaft member mounted in
ment of said rotor relative to the shaft member,
said bearing, a rotor mounted on said shaft mem
each of said rods having a coefficient of thermal
ber, said rotor and shaft member having sub
expansion approximately the same as that of
stantially different coefficients of thermal expan
said casing.
60 sion, and a plurality of axially extending rods
3. A compressor comprising a casing, a hearing
distributed about the axis of rotation, each of said
within the casing, a shaft member mounted in
rods being secured at one end to the shaft mem
said bearing, a rotor mounted on said shaft mem
ber at a single axial location adjacent said bear
ber, and a plurality of elongated axially-extend
ing members, one end of each of said elongated 65 ing and at its opposite end engaging said rotor
to limit axial movement of said rotor‘relative to
members engaging said shaft member at a lo
the shaft member.
cation adjacent said bearing and at its opposite
10. A compressor comprising a casing, a bear
end engaging said rotor to limit axial movement
ing Within the casing, a shaft member mounted
of the rotor relative to the shaft member, each
of said elongated membershaving a coefficient 70 in said bearing, a rotor comprising a plurality of
impeller sections mounted on said shaft member,
of thermal expansion approximately the same as
and a plurality of axially extending rods dis
that of said casing.
tributed about the axis of rotation, each of said
4. A compressor comprising a casing, a bearing
rods being secured at one end to the shaft mem
within the casing, a shaft member mounted. in
ber at a single axial location adjacent said bear
said bearing, a rotor mounted on said shaft mem
ing, extending through an impeller section ad
2,405,284
7
jacent said bearing, and at its‘ opposite end en-i
gaging an impeller section more remote from the
bearing to limit axial. movement’of the impeller
8
member, said axially extendingmeans having 'a
coe?icient of thermal expansion approximately
the same as that of the casing.
.
14. A compressor comprising a casing,a pair
sections relative to the shaft member.
7 L.
of
spaced bearings within the casing, a pair of
11. A compressor comprising a casing, a bear Cl
shaft members mounted in said bearings, and a
ing within the casing-a shaft member mounted
multi-part rotor, said rotor comprising two parts
in‘ said beraing, a rotor comprisinga plurality of
respectively mounted on the shafts adjacent the
impeller sections mounted. on saidshaft mem
bearings and another part mounted on both
her, and a plurality. of axially extending rods
and bridging a spacebetween them, and
distributed about the axis of rotation, each of 10 shafts,
means
extending axially past the?rst mentioned
said rods being secured at one end to the. shaft
parts connecting the last mentioned parts ‘to the
member at a single axial. location adjacent said
respective shafts at points adjacent the bearings.
bearing,‘ extending through an impeller section
15. A compressor comprising a casing, a'pairv
adjacent said bearing, and at its opposite end
of
spaced bearings within the casing, a pair of
engaging an impeller’ section more remote from
shaft members mounted in said bearings andv
the bearing under tension to limit axial move
spaced from each other, and a rotor secured to
ment of the impeller sections relative to the shaft
said shaft members only adjacent said-bearings
and bridging the space between them, said rotor
12. A compressor comprising a casing,. a bear--v
ing within the casing, a shaftmember mounted‘ 20 having a coefficient of thermal expansion sub
stantially different from that of said shaft mem-._
in said bearing, a rotor, comprising a plurality of
impeller sections, mounted on said shaft member,
16. A compressor comprising a casing, a pair
and .a: plurality of axially extending rods dis
of
spaced bearings within the casing, ‘a pair of
' tributed about-the axis of rotation, each of, said
shaft
members mounted in said bearings and
rods being secured at one end on the high pres
spaced from each other, and a rotor splined to
sure side of the impeller to the shaft member
each of, said shaft members, secured to said
at a single axial location adjacent said bear—
shaft members only adjacent said bearings andv
ing, extending through an impeller section adja
bridging the space between them, said rotor hav
cent said bearing towards the low pressure side
of the impeller, and at its opposite end engaging 30 ing a coe?icient of thermal expansion substan
tially different from that of said shaft members.
an impeller section more remote from the bear
1'7. A compressor comprising a casing, a'pair
ing to limit axial movement of the impeller sec
of spaced bearings within the casing, a pair of
tions relative to the shaft member.
shaft members mounted in said bearings and
13. A compressor comprising a casing, a bear
ing within the casing, a shaft member mounted 35 spaced from each other, and a rotor secured to‘
said shaftlmembers only adjacent said, bearings
in said bearing, a rotor splined to said shaft
and bridging the space between them,rsaid rotor
member, said rotor and shaft member having
having a coefficient of thermal» expansion sub
substantially different coef?cients of thermal ex
stantially different from'that of said shaft mem
pansion, and axially extending means secured to
the shaft member at a single axial location adja 40 bers, and approximately the same as that of said
casing.
cent said bearing and engaging the rotor at a
RUDOLPH BIRMANN.
substantial distance from the bearing to limit
axial movement of said rotor relative to the shaft
member.
,
j
,.
bers.
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