U.S. patent application number 10/760834 was filed with the patent office on 2004-09-23 for impeller and stator for fluid machines.
Invention is credited to Doege, Klaus, Franzke, Uwe, Krause, Ralph.
Application Number | 20040184914 10/760834 |
Document ID | / |
Family ID | 31502579 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040184914 |
Kind Code |
A1 |
Doege, Klaus ; et
al. |
September 23, 2004 |
Impeller and stator for fluid machines
Abstract
Impeller and stator for use in a fluid machine and consisting,
for reducing flow noise and for improving the stability of the
characteristic curve between the flow input and output
cross-sections, of a solid material matrix with a plurality of flow
channels for deflecting the flow and increasing the pressure.
Inventors: |
Doege, Klaus; (Dresden,
DE) ; Franzke, Uwe; (Reinhardtsgrimma, DE) ;
Krause, Ralph; (Dresden, DE) |
Correspondence
Address: |
Law Offices of Karl Hormann
P.O. Box 381516
Cambridge
MA
02238-1516
US
|
Family ID: |
31502579 |
Appl. No.: |
10/760834 |
Filed: |
January 20, 2004 |
Current U.S.
Class: |
415/220 |
Current CPC
Class: |
F04D 29/30 20130101;
F04D 29/54 20130101; F04D 29/38 20130101 |
Class at
Publication: |
415/220 |
International
Class: |
F01D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 17, 2003 |
DE |
103 02 773.4 |
Claims
What is claimed is:
1. An impeller and stator for use in a fluid machine, comprising: a
solid material matrix non-isotropically formed by segments spaced
from each other for forming fluid flow channels and wherein the
impeller and stator additionally function as one of a rectifier and
strainer.
2. The impeller and stator of claim 1, wherein in the direction of
flow the segments are of polygonal cross-section and are formed
from tapes.
3. The impeller and stator of claim 2, wherein in the direction of
flow the segments are of honey-com cross-section.
4. The impeller and stator of claim 2, wherein the segments are of
one of square and trapezoidal cross-section.
5. The impeller and stator of claim 1, wherein the segments are
formed from one of plastic and metal tape.
6. An impeller and stator for use in a fluid machine and consisting
of a solid material matrix of isotropic porous materials provided
with a plurality of fluid flow channels and additionally
functioning as one of a rectifier and strainer.
7. The impeller and stator of claim 6, wherein the porous materials
are foams.
8. The impeller and stator of claim 7, wherein the isotropic foams
constitute one of metal and plastic foams.
9. An impeller and stator for use in a fluid machine consisting of
a solid material matrix of one of fiber-like structures and
strainers disposed obliquely the direction of flow and comprising a
plurality of fluid flow channels and additionally functioning as
one of a rectifier and strainer.
10. An impeller and stator for use in a fluid machine consisting of
a solid material matrix comprising, in the flow direction, at least
two layers a first one of which is formed of fiber-like structures
or of an isotropic material and the second layer is formed of
segments.
11. The impeller and stator of claim 1, wherein cover tapes are
provided for mechanically stabilizing the solid material
matrix.
12. The impeller of claim 1, wherein the fluid flow channels are
partially connected with each other in a radial direction.
13. The impeller of claim 1 wherein the impeller is a radial
structure and wherein a support disc and a cover disc are provided
for mechanically stabilizing the solid material matrix.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention.
[0002] The invention, in general, relates to an impeller and to a
stator for fluid machines and, more particularly, to an impeller
and a stator for use in fans and compressors.
[0003] The compression of gaseous fluids may be carried out by
fans, hereinafter sometimes referred to as ventilators and blowers,
providing a small pressure increase and by compressors providing a
large pressure increase.
[0004] Turbo-compressors operate on the principle of energy being
supplied by changing the helix. The gas flows through a rotating
impeller provided with a plurality of vanes or blades for supplying
the energy. The gas flows through the impeller axially, diagonally
and radially. Accordingly, compressors are known as radial,
diagonal and radial fans or compressors.
[0005] In addition to impellers, fixed flow direction devices,
so-called stators or diffusors, equipped with individual vanes are
used for improving the transmission of energy and the degree of
efficiency in fans and compressors. The vanes of the impellers and
of the stators are provided with an entry or front edge and with an
exit or rear edge. The surfaces of the vanes between front and rear
edge are known as pressure and suction sides.
[0006] As regards the vanes of the impellers and stators, the mean
pressure at the pressure side of the vanes is larger than at the
suction side which causes forces to affect the vanes. The forces
equal the forces exerted by the impellers and stators on the flow
and which cause the change of the helix and the transmission of
energy in the fans and compressors. In the prior art, the impeller
vanes are affixed to a hub with an axial, diagonal or radial
contour.
[0007] At their outermost side opposite the impeller hub, the vanes
may be connected and fastened by a ring, a covering tape. In
diagonal and radial fans and compressors the ring is known as a
cover disc. Toward the outside, the impellers and stators are
enclosed by a housing. In the upstream and downstream direction the
impeller hub may be extended by a stationary housing. For the sake
of small flow losses, the gaps between the impeller or stator and
the housing are configured to be as small as possible. As a rule,
the impellers are driven by an electric motor by way of the hub of
the impeller.
[0008] An intensive noise is known to be generated when the
impellers and the pressure fields tied to the vanes between
pressure and suction side are rotating. The noise is known as
rotary noise. Another significant source of the noise are pressure
variations which are caused by the flow through the impellers and
stators and the formation of small and large swirls connected
therewith.
[0009] Many measures of minimizing the noise are known in the prior
art.
[0010] A distinction is to be made between active measures, such
as, for instance, the design of fans and compressors with small
flow losses, the selection of irregular spaces between the vanes
(division) as well, as disclosed by DE 196 04 638 A1,
crescent-shaped vanes or co-rotating jets and diffusors.
[0011] A blower is known from DE 42 05 925 A1in which the center
portion of the vanes is made of a porous material. As a result of
the porous material the vanes may be permeated from their pressure
side to the suction side. This leads to lowered pressure
differences and reduced noises otherwise generated by swirls and
pressure difference. However, this causes the efficiency of the
energy transmission and of the pressure increase to be reduced as
well. As disclosed by U.S. Pat. No. 5,244,349, perforated vanes are
used instead of porous material to reduce the mass of the
vanes.
[0012] The conditions are similar in an axial impeller with
crescent-shaped vanes which as taught by DE 196 04 638 A1 are
interrupted in the flow direction. It results in improved pressure
distribution and an improved energy transmission as well as reduced
noise generation.
[0013] The prior art also teaches lowered noise emission by
protrusions at the rear edges of impellers. In this connection, it
is assumed that as well as the pressure fields the protrusions
affect the swirls in the flow.
[0014] A second group of measures is essentially directed to muffle
the generated noises. These measures are known as passive
measures.
[0015] For instance, DE 100 19 237 A1 proposes to fabricate the hub
and the housing of sound-attenuating material. A blower is
described by DE 42 44 906 A1 in which a portion of the interior of
the housing is made of sound-absorbing material. In connection with
fans, DE 196 04 638 A1 proposes crescent-shaped vanes for reducing
the generation of noise.
[0016] Further attempts at solving the noise problem of impellers
and stators are the subject of Swiss patent CH 409 225 which
provides a flow grid structured as a fibrous body with elongated
fibrous individual bodies.
[0017] German patent 174,180 utilizes zig-zig rings and tapes which
are flowed through in a direction oblique to the shafts.
[0018] In GB 2,065,773 A disks of rigid porous materials forming
sturdy impellers for the transmission of energy.
[0019] DE 195 45 977 A1 is addressed to a similar aspect, viz.: the
cost-efficient fabrication of impellers where conventional
impellers with vanes are replaced by inexpensive bent strips of
sheet metal.
[0020] For evaluating the level of noise of fans, the specific
A-valued noise power level is utilized which is related to
predetermined values of total pressure increase, volume flow and
number of rotations. If the specific noise levels are correlated,
for instance, to the diameter as a parameter of the type of fans, a
range will result which embraces acceptable fans as regards their
degree of efficiency and specific noise power level. Very good
radial and axial fans attain specific total noise power levels of
about 20 dB (A) and 32 dB (A), respectively.
[0021] Nevertheless, the development in recent years has shown that
intensive efforts notwithstanding, it has not been possible further
to reduce the minimum specific noise power levels. Hence, in spite
of the intensive efforts, the prior art suffers from the
disadvantage that the noise pollution from fans and compressors is
still unacceptably high.
[0022] Fans of flow technologically favorable properties and
compressors providing large pressure increases and large volume
flows at a predetermined number of rotations and diameter often
suffer from the fact that they have no stable characteristic curve.
This characteristic curve, derived from applying increased pressure
as a function of the volume flow does not monotonously drop at an
increasing volume flow. This characteristic is caused by irregular
separations from the impeller and stator vanes--rotating
separation--and leads to reduced efficiency, increase noise
emission and an additional mechanical load on the vanes. For that
reason, fans must not be operated in an unstable operating range.
Several stabilizing devices are known for preventing an unstable
operation.
OBJECT OF THE INVENTION.
[0023] It is a primary object of the invention to provide impellers
and stators for axial, diagonal and radial fans or compressors
which have a significantly lower specific noise power level than
conventional fans and compressors.
[0024] Another object of the invention resides in improving the
stability of the characteristic curve of such fans and
compressors.
[0025] Other objects will in part be obvious and will in part
appear hereinafter.
BRIEF SUMMARY OF THE INVENTION.
[0026] In the accomplishment of these and other objects, the
invention provides an impeller and a stator for fluid machines,
more particularly fans and compressors, which for reducing flow
noise and for improving the stability of the characteristic curve
between the flow input and output cross-section are formed by a
solid material matrix with a plurality of flow channels where a
deflection of the flow and the pressure increase connected
therewith occur.
[0027] In accordance with an advantageous embodiment of the
invention the solid material matrix is not isotropically structured
of segments spaced from each other and which form the flow channels
for the fluid.
[0028] In the direction of flow, the segments are of polygonal
cross-sections, for instance, and are formed by tapes.
[0029] In another advantageous embodiment the segments are formed
with a honey-comb, square or trapezoid cross-section. Preferably,
the segments are formed by tapes of plastic or metal and are
fabricated by a molding process.
[0030] In accordance with a further embodiment of the invention the
solid material matrix consist of isotropic porous materials
provided with flow channels for the fluid. Advantageously, the
porous materials are foams. Metal or plastic foams are especially
suitable.
[0031] In accordance with a further embodiment of the invention the
solid material matrix is formed of fibrous structures or of sieves
arranged transversely of the flow direction.
[0032] The object of the invention is accomplished by structuring
the solid material matrix, in the direction of flow, of at least
two layers, the first layer being made of fibrous structures or of
an isotropic porous material and the second layer being formed of
segments.
[0033] It is generally advantageous to provide cover tapes for
mechanically stabilizing the solid material matrix or, in the case
of a radial structure of the impeller, to form a supporting disc
and a covering disc.
[0034] An embodiment of the invention which in terms of minimizing
flow noise is particularly advantageous is provided with flow
channels which for a partial pressure balance are partially
connected to each other in the radial or circumferential direction
thereby to reduce the noise pollution.
[0035] As conceived by the invention, the impeller and the stator
are not in the conventional manner provided with individual vanes.
In accordance with the invention, the impeller and stator are
formed by a solid material matrix with a plurality of flow
channels. As here understood, a solid material matrix are
structured materials with fluid flow channels for deflecting the
flow. When structured as an axial fan, the solid material matrix of
the impeller or stator is formed in the manner of a disc, for
instance.
[0036] The invention offers the advantageous set forth
hereinafter:
[0037] In the manner of turbo-machines, the transmission of energy
takes place by a change of the helix. New Parameters assume the
place of polars of the vanes, of the grid affects and of the
marginal losses. These are primarily the forces (3 components) per
unit of volume exerted on the flow by the solid material matrix or
the structured materials.
[0038] The swirling noise tied to the impeller and stator vanes as
well as struts and the like as well as the noise of rotation and
the siren sound are eliminated. For that reason the noise spectrum
in the center frequency range which defines the fan noise, is of an
extremely low level. The flow noise at very large frequencies is
increased. This does not, however, adversely affect the A-value
level.
[0039] In the partial load range "rotational separation" and thus a
continuous intensive noise occurs in high-load fans. Rotational
separation is based upon the laminar separation and upon the
formation of large structures extending beyond individual vanes of
a wheel. Such effects hardly occur in the case of a solid material
matrix made of structured material; i.e. all characteristic curves
are stable, special sensitizers are eliminated.
[0040] The degrees of efficiency of the novel fans are not
substantially worse than those of conventional fans the losses of
which are compound of planar, margin, gap and mixing losses. In the
case of vanes of structured material the losses resulting from the
deflection (analogously to planar losses) are substantially greater
than is usually the case. Margin losses, gap losses and mixing
losses are reduced.
[0041] All struts, e.g. for mounting the machine, are
advantageously made either of a structured material are they are
integrated into it for minimizing the size of the separation
swirls.
[0042] For achieving good partial load performance, two or more
basic structures may be used to the impeller and stator. Thus, for
minimizing impact losses, an isotropic fibrous structure is
particularly advantageous at the entrance of the wheel as a
honey-comb structure at the exit of the wheel for lowering
frictional losses.
[0043] Stepped pressure values of about 1 are required (e.g. vacuum
cleaner blower) for many applications with an axial feed direction.
Hitherto, this has been possible only with radial stages, often
with a follow-up stator and return-feed grids. Axial fans with
correspondingly large pressure values suffer from unstable
characteristic curves with all the disadvantages resulting
therefrom. This disadvantage does not arise with axial stages of
structured materials.
[0044] Because of the stability of their characteristic curves the
impellers and stators in accordance with the invention are used in
smoke-removal fans.
[0045] Because of its reduced noise emission, the concept in
accordance with the invention is used in fans for computers. A
further exemplatory field of applications is the use of the concept
for water vapor turbo compressors.
[0046] The mentioned number of possible applications demonstrates
that the principle in accordance with the invention may be applied
to many differently dimensioned fans and compressors.
DESCRIPTION OF THE SEVERAL DRAWINGS
[0047] The novel features which are considered to be characteristic
of the invention are set forth with particularity in the appended
claims. The invention itself, however, in respect of its structure,
construction and lay-out as well as manufacturing techniques,
together with other objects and advantages thereof, will be best
understood from the following description of preferred embodiments
when read in connection with the appended drawings, in which:
[0048] FIG. 1 is an axial section of an axial fan for mounting in a
pipe;
[0049] FIG. 2a, b is an axial sectional view of the axial fan for
mounting in a pipe;
[0050] FIG. 3 depicts an unwound coaxial section through impeller
and stator of an axial fan for mounting in a pipe;
[0051] FIG. 4 depicts an axial section of the axial fan with free
aspiration;
[0052] FIG. 5 depicts an unwound coaxial sectional view through
impeller and stator of an axial fan of fibrous and cellular
material;
[0053] FIG. 6 is an axial sectional view through a radial fan with
an impeller of precisely structured material;
[0054] FIG. 7 depicts different cellular structures for an impeller
for a radial fan (radial section);
[0055] FIG. 8 is an unwound coaxial sectional view through the
impeller and stator of a radial fan in which the cellular structure
is formed by many undulating and profiled discs;
[0056] FIG. 9 is an unwound coaxial section through the impeller
and stator of a radial fan in which the cellular structure is
formed by many ribbed discs;
[0057] FIG. 10 is an unwound coaxial section through the impeller
and stator of a radial fan in which the cellular structure is
formed by many ribbed discs;
[0058] FIG. 11 is an axial view of the ribbed discs of FIG. 10;
[0059] FIG. 11 a, b depict unwound coaxial sections through an
impeller and stator of the axial fan with covers; and
[0060] FIG. 12 is a radial section of the structure of an impeller
of a radial fan with covers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0061] FIG. 1 depicts an axial fan 23 provided with an impeller 1,
a stator 2 and an impeller hub 3 for mounting the impeller 1 on the
shaft of a drive motor 5. As a rule, the drive motor 5 will be an
electric motor, but other machines may be used whenever
circumstances favor it. In addition to their function suitably to
deflect the flow, the vanes of the rector serve to support the
motor 5 within a housing 6. For reasons of stability and assembly,
the center of the stator 2 is limited or defined by a stator hub 4.
The shaft of the drive motor 5 has been identified as 22.
[0062] In accordance with the invention, impellers and stators of a
solid material matrix of preferably precisely structured material
are used rather than conventional impellers and stators with
profiled twisted vanes or blades. The wall thickness of the
materials forming the segments may be very thin. In this manner the
effect of the power which the vanes or blades otherwise exert on
the flow in conventional fans, is distributed over many small
segments of "structural elements" of the matrix. The structure
lends a very high stability to the impeller 1 and stator 2. Where
special requirements demand it, supportive elements are integrated
into the impeller 1 and stator 2.
[0063] In the direction of the flow 11, the segments are of
polygonal cross-section, honey-comb cross-section 15, or square or
trapezoidal cross-section.
[0064] The segments are formed from tapes 19 of plastic or metal.
Preferably, all struts, links, brackets and the like are either
also made of structured material or they are integrated into it.
The direction of the incoming flow 11 of the fluid and the
rotational axis 10 of the shaft of the drive motor 5 and of the
impeller 1 have also been shown.
[0065] In accordance with a preferred alternative embodiment of the
invention, the impeller 1 and stator 2 are made of isotropic foams
for reducing running and flow noise. Advantageously, the isotropic
foams are metal or plastic foams.
[0066] In an equally advantageous embodiment the impeller 1 and
stator 2 are made of fiber-like structures 14.
[0067] FIG. 2 represents and enlarged sectional view of the axial
fan in the flow direction 11. The structure of the segments is
formed, for instance, by winding and connecting a tape 19 with
prefabricated struts 20. At a strong helical change and for reasons
of reducing losses, the pitch of the structure is usually larger in
the radial direction than in the circumferential direction in view
of the fact that with the deflection and circumferential direction
the losses of the secondary flow increase. For velocity and
pressure balancing, the structure may be provided with openings in
the radial as well as circumferential direction.
[0068] FIG. 3 results from a coaxial section and its flattening
onto a planar. The flow channels 21 may be seen to be different for
the impeller 1 and the stator 2. For purposes of explaining the
geometry of the section, the directions of the incoming flow 11 and
of the rotation 12 of the impeller 1 have been shown. The flow
channels 21 may as shown be uninterrupted, or they may consist of
several sections. The dimensions of the flow channels 21 must be
selected so as to result in the formation of boundary layers at
Reynold values slightly below the change-over to turbulent boundary
layers.
[0069] FIG. 4 depicts an axial fan provided with a suction nozzle.
To achieve a good partial load performance, this advantageous
embodiment of the invention provides for two different structure
layers are used in the impeller 1. This is possible for the stator
as well. The first layer in the direction of the incoming flow is
of a fiber-like isotropic structure 14 for minimizing shock losses
at the entrance to the impeller. The following second layer as the
exit of the impeller is formed of a honey-comb structure 15 and is
advantageous for reducing frictional losses.
[0070] Furthermore, the fiber-like isotropic structure 14 makes a
radial flow balance possible. The centrifugal and centripetal
channel design in the structure of the impeller 1 and stator 2 may
advantageously be used for attaining a desirable radial pressure
and velocity distribution. With reference to the precisely
structured impeller 1 the radius of curvature of the suction nozzle
13 is very small. For ensuring the stability of the impeller 1 a
covering tape 7 is used which also keeps the different layers in
engagement with each other.
[0071] FIG. 5 depicts the fiber-like isotropic structure 14 of the
entrance of the impeller 1 and of the stator in a flattened coaxial
sectional view, as well as the honey-comb structure 15 at the exit
of the impeller 1 and of the stator 2.
[0072] FIG. 6 is an axial sectional view of a radial fan 24
provided with an inventive impeller 1 made of precisely structured
material. The impeller 1 of precisely structured honey-comb
material is connected to the drive motor 5 by a support disc 16 and
by the hub 3 of the impeller. A cover disc 8 limits the impeller 1
at its side opposite the support disc 16. The impeller 1 is
enclosed by a spiral housing 9. In different applications it may be
advantageous to insert a stator 2 (not shown) also made of
precisely structured material behind the radial impeller 1.
[0073] Depending upon its intended use, the impeller 1 is
constructed with different fiber-like structures 14 or different
honey-comb cellular structures 15. In the four quadrants of a
radial section of the impeller 1 of a radial fan, FIG. 7 shows
different combinations and structures formed of one or more
straight or bent honey-comb structures and combination fiber and
honey-comb structures. The desired precise structure is formed by
the compartmentation of the impeller in axial and circumferential
directions.
[0074] In the first quadrant of FIG. 7a) a dual-layered impeller is
shown. It consists of a first layer of a fiber-like structure 14
and of a second layer of a honey-comb structure 15.
[0075] In the second quadrant of FIG. 7b) there are shown two
layers, the first layer consisting of a honey-comb structure 15 of
obliquely disposed segments and the second layer consisting of a
honey-comb structure with radially disposed segments.
[0076] The fourth quadrant 7c) depicts a layer consisting of a
honey-comb structure with obliquely arranged segments. In the third
quadrant of FIG. 7d) a layer is shown which consists of a
honey-comb structure 15 with bent or curved segments.
[0077] FIG. 8 and FIG. 9 depict the structure of a precisely
structured radial impeller of many thin, profiled and prefabricated
discs 17 having ribs. The discs are placed axially adjacent and
connected to each other. The result is a radial impeller 1 of high
rigidity which may axially be further strengthened by stays.
[0078] FIG. 10 depicts a flattened coaxial section of an impeller 1
and a stator 2 of a radial fan 24 in which the cellular structure
is made up of many ribbed discs 17. The cellular structure is
limited by the support disc 16. In accordance with this
advantageous embodiment of the invention the depicted arrangement
of the segments results in mechanical stability since forces can
circumferentially be better absorbed by segments arranged in this
manner.
[0079] FIG. 11a and FIG. 11b respectively depict a coaxial section
and an axial section of an axial impeller or stator in which the
flow channels 21 are formed by tongues 26 made by punching out and
peening of tapes. Closures 25 are being used for reducing radial
flow compensation.
[0080] FIG. 12 discloses a disc provided with ribs formed by two
rows of tongues 26 of different inclinations in the circumferential
direction. Another advantageous embodiment of the invention would
be to use of more than two rows of tongues 26.
* * * * *