FIELD OF THE INVENTION
The present invention relates to adjustable inlet guide vane (IGV) mechanism of axial
flow turbomachines like, axial flow compressor for rotating the plurality of vanes to
control various flow parameters. More particularly, the invention relates to a low-friction
producing device for rotating a plurality of inlet guide vanes (IGV) equally spaced
circumferentially and pivotable radially in the annular flow path of an axial flow turbomachinery.
BACKGROUND OF THE INVENTION
In the turbomachineries like, axial flow compressor, gas turbine etc. one or more rows of
pivoted plurality of guide vanes are used to change the direction of the incoming flow
suiting to different operating conditions of the machine. To change the vane angle
precisely and simultaneously, a mechanism which is connected to each of the vanes
through pinion gears and face gear used referred as IGV mechanism. The IGV
mechanism is connected to an actuator through actuator rod/linkage to transmit motion
to the system.
IGV mechanism is basically meant for rotating plurality of inlet guide vanes of various
turbomachineries to change the direction of the flow. For smooth operation of the IGV
mechanism, force required to operate it needs to be reduced for reducing bending force
at various components of the mechanism and avoiding jamming in the IGV system.
Three closer prior art related to IGV mechanism are given below,
[1] JP2807498B2 Sakai Haruki, Nishikawa Hisashi.
[2] US 4890977 Eric Tremaine; Allan B. Newland.
[3] US2015/0132113 A1 Lorenz JAENIKE.
In the prior art [1], IGV mechanism is described for turbo-compressor, where frictional
resistance between the guide ring and shroud is reduced by supporting the guide ring
on the plurality of guide pins, such that it is freely movable in the axial and
circumferential direction.
But disadvantage of this invention is that, guide ring is connected to the plurality of
guide vanes by means of linkage, which cannot turn the vanes precisely due to absence
of gears.
Another disadvantage is that, bending force exerts on the vane shaft as the guide vane
moves freely in the axial direction and rigidly of the system reduces during operation as
the guide pins are fixed on the casing only at one end. These lead to premature wear
and backlash problem in the system linkage. Thus the reliability of the IGV mechanism
reduces.
In the prior art [2] and [3], IGV mechanism is invented for turbomachines to rotate the
plurality of inlet guide vanes which are having axis of rotation parallel to the axis of the
respective turbomachines. Whereas in the present invention, IGV mechanism is for
axial turbomachinery like, axial flow compressor, wherein inlet guide vanes rotate about
the axis perpendicular to the rotational axis of the machine.
It is reported in the prior art [2] that, ring gear, sector gear, driven bearing lie in the
same plane with respect to the central axis for avoiding lateral force or twisting moment
to the ring gear. But disadvantage in the prior art [1] is that, friction between the ring
gear and the housing is huge, as plain bearing with higher contact surface used in this
invention. Due to higher friction between the IGV components, force needed to operate
the IGV mechanism increases. This may lead to jamming of rotating components and
also increases bending force in various components of the IGV mechanism. As a
consequence this causes premature wearing and backlash in the system components.
Whereas, in the present invention, anti-frictional bearings are used to support carrier
ring which carries the ring gear referred here as face gear, to reduce friction between
the components.
In the prior art [3] IGV mechanism is described for turbine using actuating lever and
rotatable ring and friction between these components is reduced by several means. But
disadvantage of this invention is that, guide vanes cannot be turned very precisely due
to absence of gears between the rotating components. In the present invention pinion
gears and face gear is used for precise rotation of the vanes.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to propose an IGV mechanism to rotate
plurality of vanes precisely and smoothly, requiring lower operating forces to avoid
chances of jamming of the system and to reduce bending force at various components
of the mechanism. This is achieved by reducing friction between the carrier ring and its
supporting components by using plurality of stepped supporting wheels along with
support flange and other associated components.
SUMMARY OF THE INVENTION
Accordingly, there is provided a low-friction producing device for rotating a plurality of
inlet guide vanes (IGV) equally spaced circumferentially and pivotable radially in the
annular flow path of an axial flow turbo-machinery.
In one aspect the prior art problems are overcame in the present invention by
introducing pinion and face gear and stepped supporting wheels for precise rotation of
the vanes and prevention of axial movement of the guide ring respectively. Arrangement
of giving support at both the ends of the guide pins are also introduced in the present
invention.
The device of the present invention for IGV mechanism reduces friction between the
carrier ring and the support components by introducing plurality of stepped supporting
wheels around the circumference of the outer surface of the shroud. Three variants of
the IGV mechanisms are presented here, with three different support arrangements for
the carrier ring to reduce the induced stress on the spindle of the support flange.
BRIEF DESCRIPTOR OF THE ACCOMPANYING DRAWINGS
The features and advantages of the inlet guide vane mechanism will be more evident
from the following non-limiting example and schematic drawings as indicated below:
Fig. 1 IGV mechanism of prior art ref. [1].
Fig. 2 IGV mechanism of prior art ref. [2].
Fig. 3 IGV mechanism of prior art ref. [3].
Fig. 4 is an exemplary embodiment of the sectional view of few initial stages along with
the IGV of axial flow compressor, in which flow takes place parallel to its
rotational axis.
Fig. 5 is an exemplary embodiment of a front view of an IGV mechanism for axial flow
turbomachines like, axial flow compressor with various components of the
system.
Fig. 6 is an exemplary embodiment of an enlarged view of the pinion gear, face gear,
steeped supporting wheel along with other associated components of IGV
mechanism.
Fig. 7 is an exemplary embodiment of the sectional view through the shroud, pinion
gear, face gear, carrier ring, stepped supporting wheel along with the associated
components of IGV mechanism.
Fig. 8 is an exemplary embodiment of the sectional view through the shroud, pinion
gear, face gear, carrier ring, supporting wheel, a pair of steepedsupport flange
along with the associated components of second variant of the IGV mechanism.
Fig. 9 is an exemplary embodiment of the sectional view through the shroud, face gear,
carrier ring, stepped supporting wheel along with the associated components of
third variant of the IGV mechanism.
DETAILED DESCRIPTION OF THE INVENTION
The invention is explained with various accompanying drawings where the same or
similar components or parameters are referred with the common number.
Fig. 4 is an exemplary embodiment depicts sectional view of few initial stages of an
axial flow compressor along with inlet guide vanes and rotational axis of the machine
intersecting axes 28 of plurality of pinion gears at point G.
Fig. 5 is an exemplary embodiment of an IGV mechanism assembly, depicts plurality of
guide vanes 10 equally spaced circumferentially about the rotational axis of the
compressor, are pivoted in annular space in between the hub 11 and shroud 12 of the
axial flow compressor.
Fig. 5 and 6 shows, plurality of pinion gears 13 are fixed on the spindle 14 of each vane
10 extended through shroud 12 of the casing. Axes of the pinion gears intersects the
rotational axis of the compressor at point G. A circular face gear 15 designed in two
halves engages all pinion gears 13 to rotate guide vanes precisely and simultaneously.
Face gear 15 is fixed on the carrier ring 16 by screws 22 and both are coaxial with the
axis of rotation of the compressor. Carrier ring 16 is split in two equal halves at the
vertical parting plane. Projected flanges 23 are provided at both ends of each halves of
the carrier ring 16 for bolting both the halves together using two pair of flanges 24,25 at
as shown in Fig. 5. Plurality of stepped supporting wheels 17 which are constructed with
two coaxial wheels of different diameters integrated together equally spaced
circumferentially about the rotational axis of the compressor.
Fig. 7 shows that, the stepped supporting wheels 17 are placed such that, outer surface
of the smaller diameter wheels are in contact with outer surface of carrier ring 16 to
prevent its radial displacement, which may causes due to rotational of the face gear 15
and self-weight of face gear 15 and carrier ring 16. Similarly, axial displacement of
carrier ring 16 in one direction along the rotational axis of compressor is prevented, as
the carrier ring 16 is in contact with the surface of the bigger wheel of stepped
supporting wheel 17. Axial displacement of carrier ring 16 in other direction along the
rotational axis of the compressor is prevented by the pinion gears which are in contact
with the face gears 15. Carrier ring 16 is supported by the stepped supporting wheel 17
such that, uniform clearance 21 between inner surface of carrier ring 16 and outer
surface of shroud 12 around the circumference is maintained to avoid friction between
them as shown in the Fig. 6 and Fig. 7. This helps to reduce the power requirement for
operating the system.
The plurality of stepped supporting wheel 17 are mounted on the ball bearing sleeves
18 which sit on the spindle 19 of the support flange 20 as shown in the FIG. 6 and Fig.7.
Ball bearing sleeve 18 is provided to reduce frictional resistance between stepped supporting
wheels 17 and spindle 19 allowing smooth rotationof stepped supporting wheels 17, avoiding
chance of jamming of the system. This in turn also helps to reduce torque required to operate
the system as well as bending force at various locations of IGV mechanism. Spindle 19 of the
support flange 20 is an integral part of it and overhung length of the spindle 19 is
approximatelyhalf of the width of support flange 20 along its axis to obtain more rigidly in the
supporting system. Circular fillet is provided at the circumference of the spindle 19 where it joins
to the support flange 20 for avoiding stress concentration at that location shown in the Fig. 7.
Fig. 6 shows that, support flange 20 is designed in a typical triangular shape to avoid stress
concentration while taking load of face gear 15 and carrier ring 16 during operation and bolted
on the outer surface of the shroud 12 for easy assembly of the entire system. Two halves of
carrier ring 16 are bolted together by two pair of flanges 24,25 sandwiching the projected
flanges 23 in between at two opposite location of the system as shown in Fig. 5. Pair of flanges
25 is also bolted and sandwiched the rod 26 of actuator which provides motion in the system.
Carrierring 16 and axis of actuator rod 24 are located on a same place perpendicular to the
rotational axis of compressor.
To reduce induced stress in various components of the supporting components like, spindle 19,
support flange 20 etc. and provide more rigidity in the IGV mechanism assembly, second and
third variants of inventive IGV mechanism are presented here.
Fig. 8 shows second alternative arrangement of the IGV mechanism where spindle 19 of the
support flange 20 is elongated and supported by the bore 30 of another support flange 29 bolted
similar way as firstsupport flange 20, equally placed around the circumference of outer surface
of the shroud 12, opposite side of the pinion gears 13.
Fig. 9 shows third alternative arrangement of the IGV mechanism where spindle 19 of the
support flange 20 is slightly elongated and supported by the bore 30 of the comparatively
slimmer support flange 29 having threaded stud 31, fixed on the outer surface of the shroud 12,
at other side of the carrier ring 16. In this arrangement, first support flange 20 are bolted on
outer surface of the shroud 12 such that, slimmer second support flange 29 placed in the middle
of two consecutive pinion gears 13 and much closes to the stepped supporting wheel 17 in
order to reduce the length of the spindle 19.
WE CLAIM
1. A low-friction producing device for rotating a plurality of inlet guide vanes (IGV)
equally spaced circumferentially and pivotable radially in the annular flow path of
an axial flow turbo-machinery comprising:
- a plurality of inlet guide vanes 10 pivoted on both hub 11 ad shroud 12 of the
casing, of the machine;
- a plurality of pinion gears 13, mounted on the spindle 14 of the IGV, extended
through the shroud 12 of the casing;
- a face gear 15 split in two halves, connecting all the pinions for simultaneous
rotation of the vanes 10,
- a carrier ring 16 split in two halves to hold the face gear 15 coaxially using
screws fixed parallel to the axis of rotation of a compressor;
- a plurality of stepped supporting wheels 17 mounted on the anti-friction bearing
sleeve 18 and further mounted on a spindle 19 of a first support flange 20 bolted
on an upper surface of the shroud 12; and
- a plurality of second support flanges 29 equally placed around the circumference
of outer surface of the shroud 12 to support the elongated spindle 19 of the first
support flange 20, for providing more rigidity to the IGV and reduce stresses on
IGV supporting components.
2. The device as claimed in claim 1, wherein said carrier ring 16 is supported on its
outer surface and one side surface by the plurality of stepped supporting wheel
17 to hold coaxially with the rotational axis of the compressor maintaining uniform
clearance between the inner surface of the carrier ring 16 and outer surface of
the shroud 12 around the circumference.
3. The device as claimed in claim 2, wherein each of said stepped supporting wheel
17 is fixed on the anti-frictional bearing 18.
4. The device as claimed in claim 3, wherein each of the anti-frictional bearing 18 is
further supported on the spindle 19 of the first support flange 20 on the outer
surface of the shroud 12.
5. The device as claimed in any of the proceeding claims, wherein said stepped
supporting wheel 17 arrests the radial and axial movement of said carrier ring 16
allowing a smooth rotation, clock wise or counter clock wise about the rotational
axis of the compressor.
6. The device as claimed in any of the proceeding claims, wherein the carrier ring
16 is configured to rotate under less force requirement as producing less
frictional resistance due to absence of direct surface contact between inner
surface of the carrier ring and outer surface of the shroud.
7. The device as claimed in claim 1, wherein an uniform clearance is maintained
between the inner surface of the carrier ring 16 and the outer surface of the
shroud 12 around its circumference, and wherein axes of the carrier ring 16 and
face gear 15 are coaxial to the rotational axis of the compressor.