U.S. patent application number 16/085292 was filed with the patent office on 2019-04-25 for adaptor with improved airflow.
This patent application is currently assigned to Cummins Generator Technologies Limited. The applicant listed for this patent is CUMMINS GENERATOR TECHNOLOGIES LIMITED. Invention is credited to Himanshu AGRAWAL, Haider ALI ABBAS, Abhishek KAKADE, Mark Jason RILEY, Robert Mitchell ROLSTON.
Application Number | 20190123618 16/085292 |
Document ID | / |
Family ID | 55968566 |
Filed Date | 2019-04-25 |
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United States Patent
Application |
20190123618 |
Kind Code |
A1 |
AGRAWAL; Himanshu ; et
al. |
April 25, 2019 |
ADAPTOR WITH IMPROVED AIRFLOW
Abstract
An adaptor is disclosed for connecting a rotating electrical
machine 12 to a prime mover 10. The adaptor comprises at least one
air outlet. The adaptor is arranged to provide an increase in a
cross-sectional area of air flow towards the outlet. In this way
part of the dynamic pressure can be converted into additional
static pressure rise through steady expansion of the air flow
cross-section. This in turn may help to improve the overall amount
of cooling air passing through the machine for a given fan input
power.
Inventors: |
AGRAWAL; Himanshu; (Mandla,
IN) ; KAKADE; Abhishek; (Pune, IN) ; RILEY;
Mark Jason; (Deeping St James, GB) ; ROLSTON; Robert
Mitchell; (Market Overton, GB) ; ALI ABBAS;
Haider; (Watford, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CUMMINS GENERATOR TECHNOLOGIES LIMITED |
Peterborough |
|
GB |
|
|
Assignee: |
Cummins Generator Technologies
Limited
Peterborough
GB
|
Family ID: |
55968566 |
Appl. No.: |
16/085292 |
Filed: |
March 9, 2017 |
PCT Filed: |
March 9, 2017 |
PCT NO: |
PCT/GB2017/050635 |
371 Date: |
September 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 15/10 20130101;
H02K 9/04 20130101; H02K 7/1815 20130101; H02K 5/20 20130101; H02K
9/06 20130101 |
International
Class: |
H02K 9/04 20060101
H02K009/04; H02K 7/18 20060101 H02K007/18; F01D 15/10 20060101
F01D015/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2016 |
GB |
1604667.4 |
Claims
1-38. (canceled)
39. An adaptor arranged to connect a rotating electrical machine to
a prime mover, the adaptor comprising an air outlet, wherein the
adaptor is arranged to provide an increase in a cross-sectional
area of air flow towards the air outlet.
40. An adaptor according to claim 39, wherein the adaptor comprises
a wall which directs air flow along an airflow path with an
increasing cross-sectional area.
41. An adaptor according to claim 40, wherein the wall functions as
a partial volute.
42. An adaptor according to claim 40, wherein the wall is arranged
to reduce re-entrainment of air back into the adaptor.
43. An adaptor according to claim 39, wherein the adaptor is
arranged to house a fan.
44. An adaptor according to claim 43, wherein the increase in the
cross-sectional area of the air flow is achieved by virtue of an
increasing distance between a perimeter of the fan and a wall of
the adaptor.
45. An adaptor according to claim 39, wherein the increase in the
cross-sectional area of the air flow is progressive.
46. An adaptor according to claim 39, wherein the adaptor is
substantially square-shaped in axial cross section.
47. An adaptor according to claim 39, wherein the adaptor comprises
a plurality of air outlets, and the adaptor is arranged to provide
an increase in a cross-sectional area of air flow towards each air
outlet.
48. An adaptor according to claim 47, wherein the air outlets are
spaced apart around the circumference of the adaptor.
49. An adaptor according to claim 48, wherein the adaptor has four
quadrants and an air outlet is provided in each of the four
quadrants.
50. An adaptor according to claim 39, wherein the adaptor comprises
a front member arranged to connect the adaptor to the prime mover
and a rear member arranged to connect the adaptor to the electrical
machine.
51. An adaptor according to claim 50, wherein the adaptor comprises
at least one wall connected between the front member and the rear
member, and the wall is arranged to direct air flow along an
airflow path with an increasing cross-sectional area.
52. An adaptor according to claim 51, wherein the air outlet is
provided in a first part of the wall, in the direction of air flow,
and a second part of the wall is without an air outlet or has an
air outlet which is blocked off.
53. An adaptor according to claim 52, wherein the second part of
the wall functions as a partial volute and/or to reduce
re-entrainment of air back into the adaptor.
54. An adaptor according to claim 39, further comprising a cowling
for directing airflow around at least part of the outside of the
adaptor, wherein the cowling is arranged to direct airflow which
exits from the top or bottom of the adaptor towards a side of the
adaptor.
55. An adaptor according to claim 39, the adaptor comprising an
adaptor core and a removable cover, wherein the removable cover
defines the air outlet.
56. An adaptor according to claim 55, wherein the removable cover
is arranged to fit over an aperture in the adaptor core.
57. A rotating electrical machine comprising: an adaptor arranged
to connect the machine to a prime mover; and a fan arranged to draw
air though the machine, wherein the fan is housed in the adaptor,
the adaptor comprises an air outlet, and the adaptor comprises a
wall which provides an increase in a cross-sectional area of air
flow from the fan towards the air outlet.
58. A method of cooling a rotating electrical machine, the rotating
electrical machine including an adaptor which connects the machine
to a prime mover, the adaptor comprising at least one air outlet,
the method comprising drawing air flow through the machine and out
through the at least one air outlet, wherein a cross-sectional area
of the air flow increases towards the or each air outlet.
Description
[0001] The present invention relates to an adaptor for connecting a
rotating electrical machine to a prime mover, and in particular an
adaptor which is designed to improve airflow through the
machine.
[0002] Power generation systems typically comprise a prime mover
connected to a rotating electrical machine. For example, a
generating set may comprise an internal combustion engine, such as
a diesel engine, coupled to a generator (alternator). In operation
the prime mover is used to drive the generator, in order to
generate the output power. This is achieved by mechanically
connecting rotating parts of the prime mover and the generator. An
adaptor may be used to connect non-rotating parts, in order to
prevent movement between the prime mover and the generator.
[0003] Rotating electrical machines generally comprise a rotor
which is caused to rotate relative to a stator. The stator itself
may be held within a stator frame. Typically, a magnetic field
produced by the rotor interacts with windings in the stator to
produce an electrical output. The rotor's magnetic field may be
produced by rotor windings or permanent magnets.
[0004] In operation, currents passing through the stator and/or
rotor windings, as well as other factors such as friction and
windage losses, may cause the machine to heat up. Therefore many
machines, particularly those of a larger design, require some form
of cooling. This may be achieved by providing a fan which forces
air flow through the machine. The fan may be mounted on the rotor
shaft, and may be driven directly by the prime mover.
Alternatively, an independently-driven fan may be provided. The fan
may either push or pull air through the machine. Air flow through
the machine is usually in a generally axial direction. The main
paths for the air flow are usually through the rotor/stator airgap,
and through an airgap between the stator core and the stator
frame.
[0005] In existing adaptor designs, the fan may be mounted on the
machine shaft inside the adaptor. Air outlets may be provided in
the adaptor in order to provide an exit path for airflow through
the machine. The air outlets may also provide access for an
operator to connect rotating parts of the prime mover and the
electrical machine during assembly.
[0006] An example of a known adaptor is disclosed in US
2014/0346780, the subject matter of which is incorporated herein by
reference.
[0007] In a previously considered adaptor design, air outlets are
provided at the side of the adaptor. For example, a "square-shaped"
adaptor design may be used, with two air outlets on each side of
the adaptor. A square shaped adaptor design may provide various
advantages, such as structural rigidity, ingress protection, and
allowing the expelled air to be directed in a sideways direction
away from other parts of the generating set.
[0008] However it has been found that square-shaped designs and/or
designs with side outlets may have a less than ideal aerodynamic
performance, leading to a reduction in the overall amount of
cooling air passing through the machine, and an increase in the fan
input power. It would therefore be desirable to provide an adaptor
with an improved aerodynamic performance.
[0009] According to a first aspect of the present invention there
is provided an adaptor for connecting a rotating electrical machine
to a prime mover, the adaptor comprising an air outlet, wherein the
adaptor is arranged to provide an increase in a cross-sectional
area of air flow towards the air outlet.
[0010] The present invention may provide the advantage that, by
arranging the adaptor so that it provides an increase in the
cross-sectional area of the air flow towards the outlet, a
progressive reduction in air velocity may be achieved within the
adaptor towards the outlet. This may help to convert part of the
dynamic pressure into additional static pressure rise through
steady expansion of the air flow cross-section. This in turn may
help to improve the overall amount of cooling air passing through
the machine for a given fan input power.
[0011] The cross-sectional area of the airflow is preferably in a
(notional) plane which is perpendicular to the direction of air
flow.
[0012] The adaptor may comprise a wall associated with the or each
outlet, which wall may direct air flow along an airflow path with
an increasing cross sectional area. The wall may be, for example,
part of a wall of the adaptor, such as a side wall, top wall or
bottom wall. Alternatively, the wall may be part of a removable
cover. In either case, the wall may function to gather airflow (for
example, from a fan), and guide it towards the air outlet. This may
help to reduce turbulence and/or energy loss in the airflow.
[0013] Preferably the wall functions as a partial volute. In
general terms, a volute is a curved funnel that increases in
cross-sectional area as it approaches the outlet. In an embodiment
of the present invention, a wall of the adaptor, while not
necessarily curved, may perform at least part of the function of a
volute, by increasing the cross-sectional area of the air flow and
thus reducing its speed. This may help to convert kinetic energy
into pressure, leading to an increase in the aerodynamic
performance of the adaptor.
[0014] The wall may also function to reduce re-entrainment of air
back into the adaptor. This may help to improve fan performance, by
preventing hot exhaust air from re-entering the adaptor.
[0015] The adaptor is preferably arranged to house a fan for
drawing cooling air through the machine. The fan may be, for
example, mounted on a shaft of the rotating electrical machine. In
this case a path for the air flow may be defined by the perimeter
of the fan on one side and a wall of the adaptor on the other side.
Thus the increase in the cross-sectional area of the air flow may
be achieved by virtue of an increasing distance between the
perimeter of the fan and an inside surface of the wall in a
direction of air flow towards an outlet.
[0016] The path for the air flow may be further defined by the
front and rear of the adaptor, for example, a front member and a
rear member which may be used to connect the adaptor to the prime
mover and the rotating electrical machine, respectively.
[0017] Preferably the increase in the cross-sectional area of the
air flow is progressive. This may help to ensure minimal turbulence
and energy loss in the air flow.
[0018] Preferably the adaptor is non-cylindrical. This may help
with structural rigidity, as well as allowing an increase in the
cross-sectional area of the air flow to be achieved. For example in
one embodiment the adaptor is substantially square-shaped in axial
cross section. However other shapes are also possible, and the
adaptor may be in the shape of any polygon such as a hexagon or
octagon. In all cases each of the walls may be either flat or
curved.
[0019] The adaptor may comprise a plurality of air outlets. In this
case the adaptor may be arranged to provide an increase in a
cross-sectional area of air flow towards each outlet. The air
outlets are preferably spaced apart around the circumference of the
adaptor. Thus, between each of the air outlets, there may be a
section of wall without an air outlet. The section of wall may
direct air flow to a subsequent air outlet.
[0020] In one embodiment four air outlets are provided. For
example, when viewed axially, the adaptor may be notionally divided
into four quadrants, and an air outlet may be provided in each of
the four quadrants. However any other number of air outlets, such
as 1, 2, 3, 5, 6 or some other number, may be provided instead.
[0021] The adaptor preferably comprises a front member for
connection to the prime mover and a rear member for connection to
the electrical machine. The adaptor may also include side walls, a
top wall and a bottom wall. The side walls, a top wall and a bottom
wall may connect the front member and the rear member, and may
provide internal surfaces to direct air flow to a subsequent air
outlet.
[0022] At least one of the side walls, top wall and bottom wall may
be at an angle to a circumferential direction about the adaptor.
For example, at least one of the side walls, top wall and bottom
wall may be substantially tangential to a circumferential direction
about the adaptor. This may allow the wall to provide a progressive
increase in the cross-sectional area of the air flow towards an air
outlet.
[0023] Preferably each of the walls is either flat, or curved with
a radius of curvature which is greater than the radius of the
adaptor. This may help to provide a progressive increase in the
cross-sectional area of the air flow.
[0024] Preferably each of the walls has an air outlet. This may
help to ensure that there are sufficient exit points for the air
flow. The air outlet may be provided in a first part of the wall,
in the direction of air flow. A second part of the wall (in the
direction of air flow) may be without an air outlet or may have an
air outlet which is blocked off. Thus the second part of the wall
may confine air flow within the adaptor. The second part of the
wall may direct air flow to an air outlet in a subsequent wall (in
the direction of air flow). Preferably the second part of each of
the walls functions as a partial volute and/or to reduce
re-entrainment of air back into the adaptor.
[0025] The adaptor is preferably arranged to provide air paths for
circulating air flow (that is, air flow which circulates in a
generally circumferential direction inside the adaptor). The
circulating air flow may be produced by a fan inside the
adaptor.
[0026] In some embodiments of the invention, the air outlets which
would have been provided in an existing adaptor design are blocked
off in order to achieve at least some of the advantages mentioned
above. However, the air outlets in an adaptor may also provide
access for an operator to connect rotating parts of the prime mover
and the electrical machine during assembly. If some of the air
outlets are blocked off, then access may become more difficult.
[0027] In one embodiment of the invention, the adaptor further
comprises one or more apertures to allow an operator access to
rotating parts. In this case the adaptor may further comprise means
for blocking the or each aperture. For example, a removable cover
may be used to block off an aperture. The cover may be press fitted
into the aperture and/or attached to the adaptor for example using
bolts.
[0028] In at least some of the arrangements described above, the
expelled air may be directed in various directions, such upwards
and/or downwards as well as sideways. However in some setups, such
as in some generating sets, it may be desirable for the expelled
air to be directed in a different direction, for example, away from
other parts of the generating set.
[0029] In one embodiment of the invention, the adaptor further
comprises means for redirecting airflow from an air outlet. For
example, the adaptor may further comprise a cowling which may be
located on the outside of the adaptor. The cowling may direct
airflow around at least part of the outside of the adaptor, such as
around a top or bottom of the adaptor. Preferably the cowling is
arranged to direct airflow which exits from the top or bottom of
the adaptor towards a side of the adaptor. This may help to ensure
that air is expelled away from other components.
[0030] In another embodiment of the invention the adaptor comprises
an adaptor core and a removable cover. This may provide the
advantage that a different cover can be provided to suit different
customer requirements or operating environments. For example, the
removable cover may be modified to suit different ingress
protection ratings and/or to include different filtration
components.
[0031] Preferable the removable cover defines the air outlet. Thus
in operation air flow may pass from the adaptor core, through the
removable cover, and through the air outlet defined by the
removable cover.
[0032] Preferably the removable cover is arranged to provide an
increase in a cross-sectional area of air flow towards the air
outlet. Thus removable cover may be used to adjust the air flow
pattern and thereby enhance the thermal performance of the
machine.
[0033] Preferably the removable cover is arranged to fit over an
aperture in the adaptor core. The aperture may be, for example, in
the perimeter of the adaptor core, such that, in operation, air may
flow radially outwards through the aperture. The aperture may be
defined, for example, by a space between two cross members
connecting a front member and a rear member of the adaptor
core.
[0034] An advantage of this embodiment of the invention is that the
cover can be removed during assembly to gain hand access to
coupling disc fasteners through the aperture. This can facilitate
assembly of the generator set. However when the cover is in place
it may prevent access to moving parts without a tool. Thus this
embodiment of the invention may facilitate assembly without
compromising safety, while also allowing the air flow pattern to be
adjusted, thereby enhancing thermal performance.
[0035] The adaptor may comprise a plurality of removable covers.
Preferably the adaptor comprises a plurality of apertures, and a
removable cover is provided for each aperture. For example, a
separate removable cover could be provided for each aperture, or
one cover could be provided for two or more apertures.
[0036] Preferably the adaptor core comprises a front member for
connection to the prime mover, a rear member for connection to the
electrical machine, and a plurality of cross members connecting the
front member and the rear member. In this case an aperture may be
defined by a space between the front member, the rear member, and
two adjacent cross members.
[0037] In this embodiment of the invention the front member may
comprise at least one area of reduced thickness. For example, the
front member may comprise one or more slots on its inside surface.
By area of reduced thickness it is preferably meant that the
thickness of the material in that area is less than the thickness
of the material in the surrounding area. This includes the case
that the thickness is reduced to zero, i.e. there is a hole.
[0038] By providing areas of reduced thickness, the weight of the
adaptor may be reduced, and less material may be needed for its
manufacture. The size and depth of the areas of reduced thickness
may be adjusted in order to achieve weight reduction while
maintaining sufficient mechanical stiffness.
[0039] Similar areas of reduced thickness may also be provided with
an adaptor in the other embodiments of the invention.
[0040] According to another aspect of the present invention there
is provided an adaptor assembly comprising an adaptor in any of the
forms described above, and a fan located inside the adaptor. The
fan may be for mounting, for example, on the shaft of the rotating
electrical machine. The fan may be arranged to produce a
circulating air flow within the adaptor which exits the adaptor in
a substantially tangential direction through the or each air
outlet.
[0041] The adaptor assembly may further comprise a coupling plate
for connecting a shaft of the electrical machine to the prime
mover. The or each air outlet, and/or the or each aperture where
provided, may allow an operator access to the coupling plate so
that the coupling plate can be bolted to a part of the engine, such
as a flywheel, during assembly.
[0042] According to another aspect of the present invention there
is provided a rotating electrical machine including an adaptor or
an adaptor assembly in any of the forms described above for
connecting the machine to a prime mover.
[0043] According to another aspect of the present invention there
is provided a method of cooling a rotating electrical machine, the
rotating electrical machine including an adaptor for connecting the
machine to a prime mover, the adaptor comprising at least one air
outlet, the method comprising drawing air flow through the machine
and out through the at least one air outlet, wherein a
cross-sectional area of the air flow increases towards the or each
air outlet.
[0044] Features of one aspect of the invention may be provided with
any other aspect. Apparatus features may be provided with method
aspects and vice versa.
[0045] As used herein, terms such as "axially", "radially" and
"circumferentially" are preferably defined with reference to the
axis of rotation of the electrical machine.
[0046] Preferred features of the present invention will now be
described, purely by way of example, with reference to the
accompanying drawings, in which:
[0047] FIG. 1 shows schematically a generating set comprising an
engine coupled to a generator;
[0048] FIG. 2 shows parts of a previously considered generator
design with an adaptor for connecting the generator to an
engine;
[0049] FIG. 3 shows parts of an adaptor assembly including the
adaptor and fan of FIG. 2;
[0050] FIG. 4 shows air flow patterns within the adaptor of FIGS. 2
and 3;
[0051] FIG. 5 shows an adaptor in accordance with one embodiment of
the present invention;
[0052] FIG. 6 shows exit paths for air flow in the adaptor of FIG.
5;
[0053] FIG. 7 shows air flow patterns within the adaptor of FIG.
5;
[0054] FIG. 8 shows an adaptor in another embodiment of the
invention;
[0055] FIG. 9 shows the adaptor of FIG. 8 with the apertures
blocked off;
[0056] FIG. 10 shows an adaptor design in another embodiment of the
invention;
[0057] FIG. 11 shows the cowling of FIG. 10 in more detail; and
[0058] FIGS. 12 to 16 show parts of an adaptor design in accordance
with another embodiment of the invention.
[0059] FIG. 1 shows schematically a generating set comprising an
engine 10 coupled to a generator (alternator) 12. The engine 10 is
typically an internal combustion engine such as a petrol or diesel
engine. The generator 12 may be any type of electrical generator,
such as a synchronous generator or a permanent magnet generator.
The engine 10 and generator 12 are both mounted on a bed frame 14.
Rubber mounts may be provided between the engine and the bed frame,
and between the generator and the bed frame. The crankshaft of the
engine (not shown) is mechanically coupled to the rotor of the
generator (not shown). In operation, mechanical energy produced by
the engine 10 is transferred to the generator 12 in order to
generate the electrical output.
[0060] In the arrangement of FIG. 1 the engine 10 comprises a
flywheel located in a fly wheel housing 16. An adaptor 18 is used
to connect the engine 10 to the generator 12. In FIG. 1 the adaptor
is shown attached to the flywheel housing 16, although the adaptor
may be attached to another part of the engine if designed. The
adaptor 18 provides structural attachment between the generator
housing and the engine, and thus helps to prevent relative movement
between the engine and the generator.
[0061] FIG. 2 shows parts of a previously considered generator
design with an adaptor for connecting the generator to an engine.
Referring to FIG. 2, the generator 12 includes a generator foot 13
which is arranged to connect to the bed frame either directly or
via a rubber mount. The generator also includes a terminal box 15
for electrical connections. The adaptor 18 is located at the drive
end of the generator 12. A coupling plate 20 is used to
mechanically couple the generator shaft to the engine's fly wheel.
A fan 22 is located inside the adaptor 18 on the shaft, and is used
to draw cooling air through the inside of the generator 12.
[0062] The adaptor 18 shown in FIG. 2 provides a number of
functions, including structural attachment of the generator 12 to
the engine housing, providing fan air outlets, allowing access in
order to bolt the coupling plate 20 to the engine flywheel and to
couple the adaptor to the flywheel housing, and limiting water
ingress into the generator. These impose a number of conflicting
requirements on the design.
[0063] FIG. 3 shows parts of an adaptor assembly including the
adaptor 18 and the fan 22 of FIG. 2. Referring to FIGS. 2 and 3, it
can be seen that the adaptor 18 has a "square" design. In this
design, rather than being cylindrical, the perimeter of the adaptor
is elongated at each side, so that the axial cross-section of the
adaptor approximates to a square. This "square" design helps to
achieve the necessary structural rigidity and limits water
ingress.
[0064] In the arrangement shown in FIGS. 2 and 3, the adaptor
includes two adjacent air outlets 24 on each side. These air
outlets are arranged symmetrically about a vertical plane passing
through the axis of the machine. A top wall 26 and bottom wall 28
are provided, which have a radius of curvature which is greater
than the radius of the adaptor. Thus the top wall and the bottom
wall extend outwards in a sideways direction (that is, a horizontal
direction perpendicular to the axis of the machine). The sides of
the adaptor 18 are squared off to provide the air outlets 24. A bar
25 is provided between the two adjacent air outlets 24 on each side
for mechanical strength. In addition to providing mechanical
strength, the bar (and other geometry features of the adaptor) also
provides mechanical stiffness.
[0065] The air outlets 24 are used to exhaust cooling air which has
passed through the generator. The air outlets also allow an
operator access to the coupling plate 20 so that it can be bolted
to the engine flywheel. In addition, the air outlets allow access
in order to couple the adaptor to the flywheel housing.
[0066] In practice it has been found that the aerodynamic
performance of the square adaptor design shown in FIGS. 2 and 3 may
be less than ideal. This may limit the cooling air-flow and
increase the parasitic fan power.
[0067] FIG. 4 shows air flow patterns which have been found to
exist inside the square adaptor of FIGS. 2 and 3. In the situation
illustrated in FIG. 4, the fan is rotating in an anticlockwise
direction, and the circulating airflow produced by the fan exits
through the air outlets. One problem which has been identified is
that reverse-flow may occur in some sections of the side air
outlets. This may lead to re-entrainment of hot exhaust air back
into the fan, as illustrated in FIG. 4. Another problem is that the
shape of the adaptor may not provide the most efficient internal
air flow paths for exhausting the circulating air flow.
[0068] FIG. 5 shows an adaptor 30 in accordance with one embodiment
of the present invention. The overall shape of the adaptor in FIG.
5 corresponds generally to the square adaptor design shown in FIGS.
2 and 3. However, in the adaptor of FIG. 5, the downstream outlet
on each side on each side of the adaptor (i.e. the second of the
two adjacent outlets in the direction of air flow) is blocked off.
A new outlet is provided in the top wall and the bottom wall of the
adaptor respectively, immediately after the blocked-off outlet
(again, in the direction of air flow). This results in an adaptor
with four asymmetric air outlets, rather than the four symmetric
outlets of FIGS. 2 and 3.
[0069] Referring to FIG. 5, the adaptor 30 of this embodiment
comprises a rear member 32, a front member 34, a top wall 36, a
bottom wall 38, and side walls 40, 42. The rear member 32 includes
a circular mating face or spigot 44 with bolt holes 46 for bolting
the adaptor to the frame of the generator. Similarly, the front
member 34 comprises a mating face or spigot (not visible in FIG. 5)
with bolt holes 48 for connecting the adaptor to the flywheel
housing. The number and location of the bolt holes 46, 48 may be
governed by standard requirements, such as SAE (Society of
Automotive Engineers) standards, and may be varied in dependence on
the particular engine and generator with which the adaptor is to be
used.
[0070] In the arrangement of FIG. 5, the rear member 32 and the
front member 34 are connected by means of the top wall 36, bottom
wall 38, and side walls 40, 42. The square nature of the design
helps to ensure structural rigidity.
[0071] Still referring to FIG. 5, it can be seen that each side
wall 40, 42 has a single air outlet 50, 52. In each case, the air
outlet 50, 52 is provided in the first part of the side wall, in
the direction of air flow (the direction of rotation of the fan).
Thus each air outlet is provided in the same location as the first
of the two adjacent air outlets 24 shown in FIGS. 2 and 3. However,
in the adaptor of FIG. 5, the second part of each side wall 40, 42
is blocked off, and thus confines air flow within the adaptor.
Instead, a new air outlet 54 is provided in the first part (in the
direction of air flow) of the top wall 36, and a new air outlet 56
is provided in the first part of the bottom wall 38. The second
part of the top wall 36 and the second part of the bottom wall 38
remain blocked off.
[0072] FIG. 6 shows schematically the exit paths for the air flow
in the adaptor of FIG. 5. In FIG. 6, the fan 22 rotates in an
anticlockwise direction, and thus produces a circulating air flow
within the adaptor. The circulating air flow produced by the fan 22
exits the adaptor 30 in a substantially tangential direction
through the air outlets 50, 52, 54, 56.
[0073] It has been found that the adaptor design shown in FIGS. 5
and 6 has a number of advantages over the previously considered
adaptor of FIG. 2. Firstly, it has been found that, by blocking off
the second of the two air outlets in each of the side walls, the
re-entrainment of exhaust air back into the fan can be reduced,
thereby improving fan performance.
[0074] However a further significant benefit is that the walls of
the adaptor can function as a partial volute, increasing the
cross-sectional area of the airflow from the fan towards the air
outlets. It has been found that this can improve the performance of
the fan, as explained below.
[0075] In the adaptor design of FIGS. 5 and 6, the fan acts as an
impeller to transform the mechanical energy imparted by the
rotating shaft into the air-flow as both kinetic energy (dynamic
pressure) and potential energy (static pressure) increases. It has
been found that, by blocking off the second of the two air outlets
in each of the side walls 40, 42, the side walls can perform the
following functions: [0076] 1. gather the air exiting the fan
blades and guide it towards the air outlet in the top or bottom
wall; and [0077] 2. provide a progressive reduction in air velocity
with minimal turbulence and energy loss, and hence convert part of
the dynamic pressure into additional static pressure rise through
steady expansion of the air flow cross-section.
[0078] Thus the partial volutes created by the side walls 40, 42
provide two significant benefits: they increase the overall
pressure rise created by the fan and improve the fan
efficiency.
[0079] Similarly, the top wall 36 and bottom wall 38 act as partial
volutes, guiding air flow towards the air outlets 50, 52, while
providing a progressive reduction in air velocity through steady
expansion of the air flow cross-section.
[0080] FIG. 7 illustrates air flow patterns within the adaptor 30
of FIGS. 5 and 6. Referring to FIG. 7 it can be seen that, in
comparison to the situation in FIG. 4, the air flow is less
turbulent, and there is little re-entrainment of hot exhaust air
back into the fan. FIG. 7 also shows the progressive expansion of
the air flow cross section towards the air outlets, giving a
progressive reduction in air velocity and hence improving the
performance of the fan.
[0081] Although in the adaptor shown in FIG. 5 the side walls 40,
42 are substantially flat, and the top wall 36 and the bottom wall
38 are curved, it would also be possible for the side walls to be
curved and/or for the top and/or bottom walls to be flat. It would
also be possible for any of the top wall, bottom wall and side
walls to have two or more sections at an angle to each other. In
practice any desired combination of curved and flat walls may be
used.
[0082] As discussed above, in existing adaptor designs the air
outlets also allow an operator to access rotating parts of the
machine, such as a coupling plate, so that the rotating parts of
the machine can be connected to the prime mover. Access is also
required to connect the stationary housings (adaptor to flywheel
housing). However it has been found that the adaptor design of FIG.
5 could potentially restrict the access which is available for
these purposes.
[0083] FIG. 8 shows an adaptor in another embodiment of the
invention. Referring to FIG. 8, the adaptor 60 of this embodiment
comprises rear member 62, front member 64, top wall 66, bottom wall
68, and side walls 70, 72. The rear member 62 includes a circular
mating face or spigot 74 with bolt holes 76 for bolting the adaptor
to the frame of the generator. Similarly, the front member 64
comprises a mating face or spigot (not visible in FIG. 8) with bolt
holes 78 for connecting the adaptor to a flywheel housing. As in
the adaptor of FIG. 5, in the adaptor 60 of FIG. 8, the rear member
62 and the front member 64 are connected by means of the top wall
66, bottom wall 68, and side walls 70, 72.
[0084] In the adaptor 60 of FIG. 8, the side walls 70, 72 each
include an air outlet 80, 82. Each of these air outlets 80, 82 is
provided in the first part of the side wall, in the direction of
air flow (the direction of rotation of the fan). Air outlets 84, 86
are also provided in the first parts of the top wall 66 and the
bottom wall 68, in a similar way to the adaptor of FIG. 5. However,
in the adaptor 60 of FIG. 8 additional apertures 88, 90 are also
provided in the second parts of the side walls 70, 72.
[0085] The additional apertures 88, 90 in the adaptor of FIG. 8 are
provided in order to allow access to the coupling plate (see FIG.
2) so that the coupling plate can be bolted to the engine fly wheel
during assembly of the generating set. The apertures also allow
access in order to connect the stationary housings (adaptor to
flywheel housing). The apertures 88, 90 are provided for access
only, and are blocked off after assembly of the generating set.
However, if desired, the apertures 88, 90 could be left open,
although this may remove some of the advantages of the
invention.
[0086] FIG. 9 shows the adaptor 60 of FIG. 8 with the apertures 88,
90 blocked off. Referring to FIG. 9, the adaptor 60 includes solid
covers 92, 94 which block off the apertures 88, 90. Each of the
covers 92, 94 has a recessed part 96 with a shape which corresponds
to and fits into the respective aperture 88, 90, and a lip 98 which
engages with the outside surface of the wall 70, 72. The solid
covers can be removed to allow access to the coupling plate, and
then put back in place once the generating set has been assembled.
The solid covers may be arranged to fit into the apertures 88, 90
with a press fit, and/or may be attached to the adaptor 60 with
bolts 93. When in place, the solid covers 92, 94 are substantially
air tight.
[0087] Although the covers 92, 94 shown in FIG. 9 have a recessed
part, it would also be possible to use plane (flat) covers with no
recess, or covers having another shape, if this does not affect air
flow/temperature rise significantly.
[0088] FIG. 9 also shows grills 95 which can be placed over the air
outlets 80, 82, 84, 86. The grills 95 allow air to exit while
helping to prevent entry of foreign bodies into the adaptor.
[0089] In the adaptor 60 of FIGS. 8 and 9, additional material may
be added in specific locations to increase the structural strength
and counteract the impact of the additional apertures. Referring to
FIGS. 8 and 9, cross ribs 100 are provided inside the side walls
70, 72 for additional strength. In addition, strengthening webs 102
are provided in the side walls 70, 72. In addition to strength,
these features provide additional stiffness/rigidity.
[0090] In some generating sets it is possible that, with the
adaptor designs described above, the vertical air-flow from the
additional top and bottom air-outlets may interact with other
components, such as the engine air inlet, the base frame or the
engine oil sump.
[0091] FIG. 10 shows an adaptor design in another embodiment of the
invention. In the arrangement of FIG. 10 the adaptor design is
substantially the same as that shown in FIGS. 8 and 9. However, in
the arrangement of FIG. 10, cowlings 104, 106 are provided on the
top and bottom of the adaptor 60 respectively. The cowling 104
takes air flow from the air outlet 84 at the top of the adaptor 60,
and guides the air flow around the top of the adaptor and to an
additional side outlet 108 at the top of the adaptor. Similarly the
cowling 106 takes air flow from the air outlet 86 at the bottom of
the adaptor, and guides the air flow around the bottom of the
adaptor and to an additional side outlet 110 at the bottom of the
adaptor. Thus the cowlings 104, 106 allow air to exit from the side
of the adaptor in a horizontal direction. This may help to prevent
the airflow from interacting with other components.
[0092] FIG. 11 shows the cowling 104 in more detail. Referring to
FIG. 11, the cowling 104 includes a curved top wall 112, and side
walls 114, 116. The side walls are designed to fit to the top wall
of the adaptor 60. The cowling 104 may provide a progressive
expansion of the air flow cross section towards the air outlet,
thereby giving a progressive reduction in air velocity and further
improving the performance of the fan. The cowling 106 of FIG. 10
has a similar shape to the cowling 104.
[0093] In practice, the shape of the cowlings may be adapted to fit
within the physical constraints of the generating set. Thus the top
and bottom cowlings may have a different shape, or a single cowling
may be used at either the top or bottom of the adaptor. The
cowlings may be arranged to guide airflow to either side of the
adaptor.
[0094] In any of the above embodiments the adaptor 30, 60 may be
formed from a single piece of metal, and may be cast and/or
machined in order to achieve the final adaptor shape, or the
adaptor may be fabricated. The cowlings 104, 106 and the covers 92,
94 may be formed from metal, or heat resistant plastic. However in
all cases any other suitable materials may be used instead.
[0095] Tests carried out by the present applicant have found that,
in one arrangement, an adaptor designed in accordance with the
principles described above may provide a 15% increase in air flow
rate in comparison to a previous adaptor design. This results in
better cooling of the generator, leading to better power density.
In tests, it has been found that an approximately 8.degree. C.
reduction in the temperature of the machine may be achieved in some
circumstances.
[0096] FIGS. 12 to 16 show parts of an adaptor design in accordance
with another embodiment of the invention. In the arrangement of
FIGS. 12 to 16, an adaptor core is provided which is essentially
cylindrical in shape. However removable covers are also provided in
order to modify the air flow pattern. The adaptor design of FIGS.
12 to 16 is designed to fulfil mechanical and thermal requirements
while keeping consistent or improving hand access to the coupling
disc fasteners.
[0097] Referring to FIG. 12, the adaptor core 120 of this
embodiment comprises a rear member 122, a front member 124, and
cross members 126. Four cross members 126 are provided, spaced at
regular intervals around the adaptor. The cross members 126 define
apertures 128. Thus in this embodiment four apertures 128 are
provided, spaced regularly around the adaptor core.
[0098] In the arrangement of FIG. 12 the rear member 122 includes a
circular mating face with bolt holes for bolting the adaptor to the
frame of the generator. Similarly, the front member 124 comprises a
mating face with bolt holes for connecting the adaptor to a
flywheel housing. The number and location of the bolt holes may be
governed by standard requirements, such as SAE standards, and may
be varied in dependence on the particular engine and generator with
which the adaptor is to be used.
[0099] Still referring to FIG. 12, it can be seen that slots 130
are provided on the inside of the front member 124. The slots are
areas of reduced thickness, and are designed to reduce the weight
of the adaptor. The size and depth of the slots are adjusted in
order to achieve weight reduction while maintaining sufficient
mechanical stiffness for various SAE sizes. Although in FIG. 12 the
slots are shown as areas of reduced thickness, in some embodiments
all material may be removed in these areas.
[0100] The adaptor core 120 of FIG. 12 may be made from SG
(spheroidal graphite) iron, although other suitable materials may
be used instead. The adaptor core may be made by casting and/or
machining, or any other suitable technique.
[0101] The primary function of the adaptor core 120 is to provide a
mating connection face between the generator frame and the engine
flywheel housing. The adaptor core is therefore designed to provide
a robust connection between the generator and the engine. The four
apertures 128 on the sides give improved hand access to reach the
coupling disc fasteners. This makes the adaptor easier to assemble
and service. The adaptor is designed in such a way that it is
lighter and stiffer with slots in the back face of the casting
(engine side) to make it lighter.
[0102] FIG. 13 illustrates how removable covers may be added to the
adaptor core of FIG. 12. Referring to FIG. 13, a separate cover
132, 134, 136, 138 is provided for each of the apertures 128. The
covers fit around the outside of the adaptor core, and are used to
adjust the air flow pattern.
[0103] FIG. 14 shows the cover 132 in more detail. Referring to
FIG. 14, the cover 132 comprises a rear wall 140, a front wall 142,
a top wall 144, and a side wall 146. The rear wall 140 and front
wall 142 extend radially outwards from the adaptor core in
substantially the same planes as the rear member 122 and front
member 124, respectively. Thus the rear wall 140 and front wall 142
constrain airflow beyond the periphery of the adaptor. The top wall
144 is substantially tangential to the adaptor core, and blocks off
air flow. The side wall 146 is substantially tangential to the
adaptor core and substantially perpendicular to the first wall, and
defines an air outlet. A grill 148 is provided in the air outlet
for ingress protection and to improve strength and rigidity.
[0104] FIG. 15 shows the cover 134 in more detail. Referring to
FIG. 15, the cover 134 comprises a rear wall 150, a front wall 152,
a top wall 154, and a side wall 156. The rear wall 150 and front
wall 152 extend radially outwards from the adaptor core in
substantially the same planes as the rear member 122 and front
member 124, respectively. Thus the rear wall 150 and front wall 152
constrain airflow beyond the periphery of the adaptor. The side
wall 156 is substantially tangential to the adaptor core, and
blocks off air flow. The top wall 154 is divided into two parts
158, 160. The first part 158 is substantially flat, and
substantially perpendicular to the side wall 156. However the
second part 160 is curved, and conforms substantially to the shape
of the outside of the adaptor core. The first part 158 and second
part 160 of the top wall 154 together define an air outlet. A grill
is provided in the air outlet for ingress protection and to improve
strength and rigidity.
[0105] The covers 136 and 138 shown in FIG. 13 have substantially
the same shapes as the covers 132, 134, respectively. The covers
may be made from any suitable material, such as sheet steel.
[0106] FIG. 16 shows the adaptor with the covers 132, 134, 136, 138
in place. The removable covers fit to the outside of the adaptor
core 120 to give it an overall "square" shaped design similar to
that of the adaptor of FIGS. 5 and 8.
[0107] Referring to FIG. 16, it can be seen that, when the covers
132, 134, 136, 138 are fitted to the adaptor core 120, they define
a top wall, a bottom wall, and side walls. The first part of each
of these walls is blocked off, while the second part of each of the
walls has an air outlet. As a consequence, the air flows in the
adaptor are similar to those shown in FIGS. 6 and 7.
[0108] In the arrangement of FIGS. 12 to 16, the internal profile
of the adaptor core 120 and the covers 132, 134, 136, 138 is
designed to provide a volute effect to the airflow. This improves
the airflow performance, in comparison to previously considered
adaptor designs. Thus the thermal performance of the generator can
be improved.
[0109] An advantage of the removable covers in the adaptor of FIGS.
12 to 16 is that they can be modified to suit different ingress
protection ratings. This can provide the flexibility to cater for
different customer requirements and operating environments. Various
different removable covers can be manufactured to provide various
degrees of ingress protection, without the need to manufacture a
different adaptor for each situation.
[0110] Another advantage of the removable covers is that they can
be removed during assembly to gain hand access to coupling disc
fasteners. This can facilitate assembly of the generator set.
However when the covers are in place they prevent the operator from
gaining access to moving parts without a tool, thereby complying
with operating regulations.
[0111] In addition, the removable covers can be used to adjust the
air flow pattern thus enhancing the thermal performance.
[0112] Furthermore, the removable covers may include various
different filtration components which may be adapted to suit
different customer requirements and operating environments.
[0113] It will be appreciated that embodiments of the present
invention have been described by way of example only, and
modifications in detail will be apparent to the skilled person. For
example, features of one embodiment may be provided with any other
embodiment. Although embodiments of the invention have been
described with reference to a generating set, the present invention
may be used with any type of system where it is desired to connect
a prime mover to a rotating electrical machine.
* * * * *