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Патент USA US2406126

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Aug."ZG, 1946.
' Filed June 7, 1943
. .. 4
I 2,406,126
Patented Aug. 20, 1946
arr-Q: P
2,406,126 *
ottb‘Tzwéiret‘Baaén; Switzerland; designer’ to AirT
- tien'ge'sellsch'aft Brown, Boveri. & Cie., Baden;
. Switzerland‘
can; (or. 230-122)
For manufacturing reasons the‘ bladingibf
multiestage axial type compressors is generally
composed ofas many similar stages. aspossible';
the majority of the .rows of moving blades ‘as well
as most of the ro'wsof stationaryibladesbeing?
each of the same kind. In the special case‘fo‘fithe
so-called; symmetrical‘. . blade ‘arrangement the.
moving and stationary blades are. not merely of
the .same‘desig'n" but the moving and stationary
blades are also the image of each other. The
entrance and exit angles are also repeated from
5 m1 8"the
with thenovell’corrstructio'
andFig. 9 shows a spe
cial'modi?ed form qi'ftne invention. _, _,
The ‘ axial blower ‘shown diagrammatically in?
sectiQnTin Fig-.- -1 >_ comprises ?vesyrnmetricalnor
.mal stages which'1 each include" mew of rotating?
blades sand ‘a row?" of ' stationary "blades ~3iyv The‘
swirl wnienmust be'iinpaneq‘ tofthe- now» n orderv to obtainiin"v accordancelwith‘the» direc 1on of-?ow,
02‘: (Fig? 4)? ails‘iiiootri‘lenny lhbi‘J-“VllEéT?IJSt moving
blade row (Fig. 2) is achieved by the stationary
stage to stage, the only di?erence between the
blade row’ I. This blade row consists of heavily
stages being the length and twist of the blades.
curved guide blades in which the medium has its
Amongst these blades, which on account of their
axial velocity or changed to a velocity 02. Corre
similarity are designated as “normal stages” 15 sponding to the increase in velocity there is a
there is a kind where the absolute path of the
decrease in pressure (Fig. 3) which can onlybe
?ow both in front of the stationary blade as well
compensated again in the subsequent compressor
as in front of the moving blades diverges consid
erably from the axial direction. In order ‘to ob
With the arrangement according to the inven- 7
tain a smooth entrance into the ?rst stage of such 20 tion the guide row I in Fig. 1 is replaced by a
blading it is necessary to give the medium which
specially shaped moving blade row 4 as shown in
has to be compressed a certain swirling motion
Figs. 5' and 6. The relative velocity wi (Fig. 8)
which diverts the ?ow into the desired circumfer
corresponding to the absolute axial velocity 01 is '
ential direction.
reduced to wz due to being diverted in the moving
It is known to produce vthis entering swirl by 25 blade row 4. 202 in direction and magnitude thus
giving the entrance spiral of the casing a special
gives the same absolute velocity ascz in Fig. 4.
form or by means of a row of stationary blades 7
with nozzle-like guide elements or by combining
both these devices. A disadvantage of all these
devices is, however, that the required swirling ef
feet is only achieved at the expense of a drop in
pressure which can only be compensated by addi
tional stages and this means further losses.
The present invention concerns a blade ar
Since, however, this velocity has been obtained by
a reduction in velocity there will bean increase
in pressure as shown in Fig. 7 and not a pressure
30 drop as is the case with the known arrangement
previously described.
As can be seen from Figs. 6 and 8 the moving
blade row located in front of the normal. stages
differs from the normal moving blades in various
rangement for axial compressors with a plurality 35 respects. ' The circumferential components of they
of rows of the same stationaryand the same
relative velocities of the additional moving blade
moving blades or at leastgeometrically similar
row are considerably higher than those of the
blades, so-called normal stages, and with a ?ow 7 moving blade rows of the normal stages and the
of the medium which is to be compressed which
' entrance angles are therefore acuter. The blade
diverges considerably from the axial direction 40 does, however, not need to be bigger.
both in front and after each guide row, so that
Although the usual form of the invention is
the medium which is to be compressed in order to
with two independent. rows of moving blades it is
achieve a smooth entry must receive a certain
also possible to combine both rows to form a sin‘
swirl, this swirl being mainly produced by a mov
gle row. The pro?le of these combined moving
ing blade row which is located in front of the 45 blades is then composed of a blade part which at
I ?rst moving blade row of the normal stage blad
ing. The normal construction of blading accord
ing to one form of the invention thus commences
with two rows of moving blades the second of
. the inlet possesses the angleand pro?le conditions
of the guide blades in the supplementary moving
row- and of a trailing blade part which has the
same angle and pro?le conditions as a moving
which is a moving blade row of a “normal stage.” 50 compressor blade of the “normal stages.”
The invention is explained by means of three
constructional examples shown in the accom
panying drawing the ?rst of which, Figs. 1 to 4,
refers to the hitherto known arrangement of ,
This combined construction is shown in Fig. 9.
In the blade 5 which is a combination of the blades,
2 and 4 the velocity w of Fig. 8 must bedirectly
reduced to wa. The advantage of this combina
blading, whilst the second example illustrated in 65 tion is that a row of blades can be dispensed with.
nent to the gas as it enters said'?rst compressor"
Slightly higher ?ow losses due to the greater
stage and for discharging the gas therefrom at
substantially the same angle as that at which gas
Since the ?rst row of moving blades of the normal
discharged from the rotating blades of each of
stages is combined with the supplementary row in
front of the normal stages the first moving row is 5 said plurality of compressor stages, said rotating
"immediately followed by-_a normalstationary blade means having an entrance angle more acute
deviation have, however, to be taken into account. '
with respect to ‘the axial ‘direction of gas flow
Under certain conditions it is also possible to
use the same pro?les for the supplementary movg
than the corresponding entrance angle of the ro
' tating blades' of said plurality of compressor
ing blades as for the moving rows, of ‘the 'normal‘10 ' stages and having a discharge angle identical with
stages. The blades of the supplementary; row
' the corresponding discharge angle of the rotating
of said plurality of compressor stages.
'-must, however, be 50 arranged that their angle "
2. In an axialy?ow gas compressor, the inven
to the circumferential direction is considerably
, more acute than the entrance angle "of the sue-e} .~ tion as recitedin claim 1, wherein said rotating
15 blade means comprisesan inlet row of blades hav
ceeding normal stages.
In addition to the moving bladerow the shape
ing said more acute entrance angle, and a second
of the inlet casing can also assist'in impartL'a -'
v.row of blades between said inlet row and said row
swirling effect on the medium.
' ’ "
of stationary‘blades of the ?rst compressor stage,
" said ‘second row of blades having the same pro
1. In an axial ?ow gascompressor, the com- 20 file as the rotating blades of said plurality of com- '
I claim:
bination with v a; plurality pig-compressor; stages
pressor stages.
and of stationaryvblades‘ of geometrically similar
"3. In an axial ?ow gas compressor, the inven
tion/as recited :in claim. 1, wherein said rotating
blade means comprisesa single row of‘ blades hav
comprising‘ alternately-arranged rows of rotating
pro?le,‘ of a ?rst compressor stage preceding said
pluralityiof compressor stages;_ said ?rst compresT
25 ing entrance'portions of saidmore'acute entrance
sorsiage cqmnrisin's arrow of stabionarygbladesof .
‘ t'hesame pro?le as; thelrqws of stationary blades
angle and trailing portions of the same angleand
of said plurality-of‘
' prO?leas the rotating blades
riffseid pluralitydiecmpressorlstases, and rotate
ing blade means: preceding said row of stationary
blades'forf-imparting au‘circumferential compor. 3n
compressor stages.
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