U.S. patent application number 15/730139 was filed with the patent office on 2018-05-10 for high efficiency double suction impeller.
The applicant listed for this patent is Nuovo Pignone Tecnologie Srl. Invention is credited to Lorenzo BERGAMINI, Tommaso CAPURSO, Marco TORRESI.
Application Number | 20180128271 15/730139 |
Document ID | / |
Family ID | 58010305 |
Filed Date | 2018-05-10 |
United States Patent
Application |
20180128271 |
Kind Code |
A1 |
BERGAMINI; Lorenzo ; et
al. |
May 10, 2018 |
HIGH EFFICIENCY DOUBLE SUCTION IMPELLER
Abstract
A new double suction impeller, in particular for centrifugal
pumps and hydraulic power recovery turbines, wherein the flow-path
arrangement has inter-blade channels intersecting each other at the
impeller's outer diameter so that the equivalent number of blades
is doubled with respect to a conventional configuration obtained by
the coupling of two single suction impellers.
Inventors: |
BERGAMINI; Lorenzo; (Bari,
IT) ; TORRESI; Marco; (Bari, IT) ; CAPURSO;
Tommaso; (Bari, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nuovo Pignone Tecnologie Srl |
Florence |
|
IT |
|
|
Family ID: |
58010305 |
Appl. No.: |
15/730139 |
Filed: |
October 11, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/007 20130101;
Y02E 10/223 20130101; F04D 29/2255 20130101; F04D 29/628 20130101;
F04D 29/2205 20130101; F04D 1/006 20130101; Y02E 10/20
20130101 |
International
Class: |
F04D 1/00 20060101
F04D001/00; F04D 29/22 20060101 F04D029/22; F04D 29/00 20060101
F04D029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 7, 2016 |
IT |
102016000111763 |
Claims
1. A double suction impeller, comprising: a hub associated to a
tubular center bore, the hub comprising: a plurality of blades
integrally attached to the hub and to a left side shroud and to a
right side shroud, the left side shroud and the right side shroud
being provided with a center aperture adjacent to the tubular
center bore, the outer edge of the left side shroud and the outer
edge of the right side shroud defining the impeller exit, the
impeller exit having a width and a median plane wherein each pair
of adjacent blades of the plurality of blades define a plurality of
inter-blade channels adapted to connect a plurality of input
apertures, located within the center apertures of both the left
side shroud and the right side shroud, to a plurality of output
apertures located on the impeller exit, the inter-blade channels
comprising left side inter-blade channels, having their respective
input apertures located within the center aperture of the left
side, and right side inter-blade channels, having their respective
input apertures located within the center aperture of the right
side shroud, characterized in that the left side inter-blade
channels and the right side inter-blade channels intersect the
median plane of the impeller exit in a way to dispose the plurality
of output apertures of the left side inter-blade channels to be
aligned and alternated with the output apertures of the right side
inter-blade channels, on the impeller exit.
2. The double suction impeller according to claim 1, characterized
in that the double suction impeller is made of a single piece.
3. The double suction impeller according to one or more of claims
from 2, characterized in that the center bore is adapted to receive
the impeller drive shaft, the impeller drive shaft being drivingly
connected to said center bore by a key and a keyway.
4. The double suction impeller according to claim 3, characterized
in that the center aperture comprises an aperture edge and an
aperture rim.
5. The double suction impeller according to claim 4, characterized
in that it further comprises: a suitable housing having axial
inlets and a circumferential volute or diffuser outlet passage.
6. A centrifugal pump comprising a double suction impeller
according to claim 5.
7. A hydraulic power recovery turbine comprising a double suction
impeller according to claim 5.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a high efficiency double
suction impeller, e.g. one that may be used for centrifugal
pumps.
BACKGROUND
[0002] Radial flow turbo machinery devices are particularly adapted
to convert shaft power to kinetic energy (and vice versa) by
accelerating (or decelerating) a fluid in a revolving device called
impeller. When used as power-absorbing machines, impellers are
commonly used to raise the pressure of a fluid or induce a fluid
flow in a piping system.
[0003] The impeller is the device, within the turbo machinery,
that, rotating, exchanges energy with the fluid. In its simplest
implementation the impeller comprises a plurality of blades fitted
onto a hub plate. The shape and the geometry of impeller blades can
be of many different types depending on the use, the rating, the
performance of the turbo machinery.
[0004] Having defined the specific speed, NS, of a pump as
follows:
NS = nQ 1 / 2 1.1618 H 3 / 4 ##EQU00001##
where, n=rotating speed in revolution per minute Q=volumetric flow
rate in [m.sup.3/h] H=differential head [m] for centrifugal pumps
of capacity larger than 10 m 3/h designed with low or medium
specific speed values (e.g. NS<1600) and a double suction
configuration, an impeller with a small number of blades is
required in order to keep the head vs flow rate stable and
continuously rising towards zero flow. This requirement is very
important especially in case of more than one centrifugal pump
employed in parallel, each working with a fraction of the available
flow. Furthermore, centrifugal pumps of large capacity designed for
low or medium specific speed values and for medium or high values
of hydraulic head, require impellers having large diameters and
narrow exit width. Double suction impellers are usually composed by
two single suction impellers each elaborating half of the total
flow and arranged in a back-to-back configuration.
[0005] In the state-of-the-art, centrifugal pumps having impellers
provided with a center rib and staggered blades, the ratio between
the impeller exit width b2 and the impeller diameter D2 can be well
lower than 0.05. Impellers of this kind often show an unstable head
vs flow rate characteristic curve. In addition to that, another
drawback of this kind of impellers lies in the low blade exit
angles (normally between 15.degree. and 20.degree.) and
corresponding large wrap angles (normally between 120.degree. and
270.degree.) that are required to maintain acceptable slip factor
values. As a result, the hydraulic efficiency of the
state-of-the-art impeller of this kind is typically smaller than
95%.
[0006] Furthermore, the low blade load typical of this kind of
impellers (normally corresponding to head coefficients "psi" lower
than 1, psi being equal to:
psi = 2 gH u 2 2 ##EQU00002##
where g=gravity acceleration in [m/s 2] H=differential head in [m]
u2=peripheral speed of the impeller in [m/s]) increases the
required diameter of the impeller, thus increasing the disk
friction losses by 1%-2% when compared to impellers having head
coefficients greater than 1.
[0007] The achievable head coefficient can be increased by
employing conventional split blades impellers, but this choice does
not solve the problem of the narrow b2/D2 and poor head curve
stability. Moreover, the number of leading edges of conventional
split blades impellers is doubled, causing additional hydraulic
losses.
BRIEF DESCRIPTION OF THE INVENTION
[0008] Embodiments of the present invention therefore relate to a
double suction impeller having the channels between the blades
starting from both inlets and crossing the median axis of the
impeller exit in such a way that, as a result, the equivalent
blades number is doubled with respect to a conventional
configuration obtained by the coupling of two single suction
impellers.
[0009] In the new impeller reducing the slip factor by increasing
the equivalent number of blades permits reducing the diameter of
the impeller, thus reducing the size and therefore the
manufacturing cost of the pump installing said impeller.
[0010] Compared to a conventional impeller provided with splitter
blades, embodiments of the new impeller do not introduce any
additional leading edge and corresponding losses.
[0011] For low specific speed pumps the new shape of the
inter-blade channels of the impeller is such that the hydraulic
diameter is increased and the length of each channel reduced, thus
reducing the hydraulic losses with respect conventional
impellers.
[0012] Furthermore, the reduction of the impeller diameter brings
also along a significant reduction of the losses due to disk
friction, thus increasing the overall pump efficiency.
[0013] The advantages and benefits associated to the new double
suction impeller, with respect to an equivalent state-of-the-art
impeller, increase as the operating speed of the new double suction
impeller is decreased.
[0014] The main application for the new double suction impeller is
within centrifugal pumps and hydraulic power recovery turbines
especially, but not exclusively, intended for refinery,
petrochemical and pipelines. However, other applications are
possible and contemplated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] These and other features, aspects, and advantages of
embodiments of the present invention will become better understood
when the following detailed description is read with reference to
the accompanying drawings in which like characters represent like
parts throughout the drawings, wherein:
[0016] FIG. 1 illustrates a meridional section of a state of the
art double suction impeller;
[0017] FIG. 2 illustrates a view of the inter-blade channel of the
state of the art double suction impeller;
[0018] FIG. 3 illustrates a detail of the outer diameter
arrangement of a state of the art double suction impeller;
[0019] FIG. 4 illustrates a detail of the section of an embodiment
of a new double suction impeller;
[0020] FIG. 5 illustrates a view of the inter-blade channel of
another embodiment of the new double suction impeller;
[0021] FIG. 6 illustrates a detail of the outer diameter
arrangement of another embodiment of the new double suction
impeller;
[0022] FIG. 7 illustrates a first front view of another embodiment
of the new double suction impeller;
[0023] FIG. 8 illustrates a meridional cross section of an
embodiment of the new double suction impeller; and
[0024] FIG. 9 illustrates a side view of an embodiment of the new
double suction impeller.
DETAILED DESCRIPTION OF THE INVENTION
[0025] With reference to the enclosed drawings and according to an
exemplary embodiment, embodiments of the present invention relate
to new a double suction impeller, in particular for centrifugal
pumps, wherein the flow-path arrangement is characterized by
inter-blade channels intersecting each other at the impeller outer
diameter.
[0026] In one embodiment, the new double suction impeller comprises
channels between the blades starting from both inlets and
intersecting at the outer diameter of the impeller in such a way
that the equivalent blade number is doubled with respect to a
conventional configuration obtained by simply adjoining to a
central rib two single suction impellers, as illustrated in
enclosed FIGS. 1, 2 and 3.
[0027] In greater detail, and with reference to enclosed FIGS. 4,
5, 6, 7, 8 and 9, the new double suction impeller includes a
shrouded impeller 10. The shrouded impeller 10 may further include
a hub 11 associated with a tubular center bore 12. The tubular
center bore 12 may be adapted to receive the impeller drive shaft
which is drivingly connected thereto, generally by a key and a
keyway.
[0028] The shrouded impeller 10 can be made either of one single
piece--or assembly--or it can be made of a plurality of assemblies,
e.g. comprising one left shroud, one right shroud and a central
core.
[0029] In one embodiment, the new impeller is made of one single
assembly, and the hub 11 further includes a plurality of blades 13
integrally attached to the hub 11 and to a pair of integral
shrouds, a left side shroud 14 and a right side shroud 15. Each one
of the integral shrouds 14, 15 is provided with a center aperture
16, 31 that constitutes the impeller eye. The impeller eye is
adjacent to said tubular center bore 12 and comprises an aperture
edge 17 with an aperture edge radius and an aperture rim 18 with an
aperture rim radius.
[0030] The left side shroud 14 defines the left side aperture and
the right side shroud 15 defines the right side aperture of the
double suction impeller according to the present invention.
[0031] The outer edge of said left side shroud 14 and the outer
edge of said right side shroud 15 define the impeller exit, said
impeller exit having a width 19 and a median plane 20.
[0032] In greater detail, each pair of adjacent blades 13 of said
plurality of blades 13 define a plurality of inter-blade channels,
referred to in enclosed FIG. 5. Said inter-blade channels are
adapted to connect a plurality of input apertures, located within
the center apertures of both said left side shroud 14 and said
right side shroud 15, to a plurality of output apertures located on
said impeller exit.
[0033] With reference, in particular, to enclosed FIGS. 4 and 6,
said inter-blade channels comprise left side inter-blade channels
21, having their respective input apertures 22 located within the
center aperture of said left side shroud 14, and right side
inter-blade channels 24, having their respective input apertures 25
located within the center aperture of said right side shroud
15.
[0034] Advantageously, said left side inter-blade channels 21 and
said right side inter-blade channels 24 are such as intersecting
the median plane 20 of said impeller exit in a way to dispose the
output apertures 23 of said left side inter-blade channels 21
aligned and alternated with the output apertures 26 of said right
side inter-blade channels 24, on said impeller exit.
[0035] In operation, when rotated, fluid will be drawn axially into
the impeller as indicated by the arrows 27, 28, impelled by the
plurality of blades 13 passing between the hub 11 and said left and
right shrouds 14, 15 and finally expelled radially through said
exit as indicated by the arrows 29. The impeller runs in the
direction of arrow 30 in a suitable housing having axial inlets and
a circumferential volute or diffuser outlet passage.
[0036] In the double suction impeller according to the present
invention, the effect connected to the crossing by said inter-blade
channels of the median axis of the impeller exit is such that the
equivalent blades number is doubled with respect to a conventional
configuration obtained by the coupling of two single suction
impellers.
[0037] With reference to enclosed FIG. 2, the section 33
corresponds to the inlet of a channel of an impeller of the state
of the art, and area 32 corresponds to the outlet of a channel of
an impeller of the state of the art.
[0038] With reference to enclosed FIG. 5, the section 35
corresponds to the inlet of a channel of the new impeller, and area
34 corresponds to the outlet of a channel of the new impeller.
[0039] It is apparent that, when comparing inter-blade channels of
a double suction impeller of the prior art with the inter-blade
channels of the new double suction impeller, the outlet area 34 of
the inter-blade channels of the new double suction impeller has a
rectangular shape with an aspect ratio much closer to 1 with
respect to that of a state of the art impeller.
[0040] Finally, benefits introduced by the new double suction
impeller include, inter alia, reduction of the slip factor and
reduction of hydraulic losses. These reductions may translate to an
efficiency increase of about 3% to 4% and, ultimately, to a lower
operating expenditure and lower capital expenditure.
[0041] The above description of exemplary embodiments refers to the
accompanying drawings. The same reference numbers in different
drawings identify the same or similar elements. The following
detailed description does not limit the invention. Instead, the
scope of the invention is defined by the appended claims.
[0042] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment.
Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments. The
above detailed description does not limit the scope of the claimed
invention. Instead, the scope of the invention is defined by the
appended claims.
* * * * *