TURBO -COMPRESSOR TRAIN WITH ROLLING BEARINGS AND RELATED ASSEMBLY METHOD
BACKGROUND
TECHNICAL FIELD
Embodiments of the subject matter disclosed herein generally relate to methods
and systems and, more particularly, to mechanisms and techniques for providing
an entire turbo-compressor train with a single lube pump and/or with a single
lubrication oil medium.
DISCUSSION OF THE BACKGROUND
Gas turbines are used in many sectors of the industry, from military to power
generation. They are used mainly to produce electrical energy. However, some
gas turbines are used to propel various vehicles, airplanes, ships, etc. In the oil
and gas field, the gas turbines are used to drive compressors, pumps and/or
generators. As shown in Figure 1, a gas turbine 12 may be connected to a
compressor or generator 14 and to an auxiliary equipment 16. A gear box 18 or
other equipment may be provided between the gas turbine 12 and the compressor
or generator 14. All these elements form a turbo-compressor train 10.
The gas turbine 12 may include a compressor 20 that is configured to receive a
gas (e.g., air) at an input 22 and to provide the gas compressed to a
predetermined pressure at an outlet 24. The compressed gas is then input to a
combustor 26 where it is mixed with a fuel provided from a line 28. The mixture of
gas and fuel is ignited and the hot gases at high pressure are provided to an input
30 of an expander 32. The exhaust gases are then released at output 34 of the
expander 32.
The expansion of the hot gases through the expander 32 determines a rotation of
a rotoric part (not shown) which is coupled, through the gear box 18 to a shaft of
the compressor 14. Thus, the compressor 14 is driven by the expander 32. One
or more of the components of the turbo-compressor train 10 involves heavy rotoric
parts (e.g., shaft, impeller, etc.) that rotate at a high speed. In order to promote
the rotational motion of these components and to minimize the friction, various
bearing units are provided in the train. A few arrangements are discussed next.
Figures 2A-C show the train 10 of Figure 1 in which some elements have rolling
bearings and the remaining elements have hydro-dynamic bearings. Those
elements having the rolling bearings are identified with A and those having the
hydro-dynamic bearings are identified with B. Further, it is noted that the rolling
bearings need to use synthetic oil while the hydro-dynamic bearings need to use
mineral oil. Thus, the arrangements shown in Figures 2A and 2B need two lube
pumps, one for each type of bearings while the arrangement shown in Figure 2C
uses one lube pump and the mineral oil. These arrangements have a higher
weight and maintenance cost due to the dual lube pump, they have a large
footprint and require higher plant complexity. A disadvantage of the configuration
shown in Figure 2C is the higher lube oil consumption needed for hydrodynamic
bearings.
Accordingly, it would be desirable to provide systems and methods that avoid the
afore-described problems and drawbacks.
SUMMARY
According to one exemplary embodiment, there is a turbo-compressor train that
includes a gas turbine configured to transform thermal energy into mechanical
energy; a centrifugal compressor having a shaft connected to a shaft of the gas
turbine; and a single lube pump configured to provide synthetic oil to the gas
turbine, and the centrifugal compressor. The gas turbine, the centrifugal
compressor and the single lube pump each has only rolling bearings.
According to another exemplary embodiment, there is a turbo-compressor train
that includes a gas turbine configured to transform thermal energy into mechanical
energy; a generator having a shaft connected to a shaft of the gas turbine; and a
single lube pump configured to provide synthetic oil to the gas turbine, and the
generator. The gas turbine, the generator and the single lube pump each has only
rolling bearings.
According to still another exemplary embodiment, there is a method for
assembling a turbo-compressor train. The method includes mechanically
connecting a gas turbine to a centrifugal compressor; mechanically or electrically
connecting a lube pump to the gas turbine; and providing each of the gas turbine,
the centrifugal compressor and the lube pump only with rolling bearings and the
lube pump is configured to pump synthetic oil.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of the
specification, illustrate one or more embodiments and, together with the
description, explain these embodiments. In the drawings:
Figure 1 is a schematic diagram of a conventional turbo-compressor train;
Figures 2A-C are schematic diagrams of conventional turbo-compressor trains
having two lube pumps or being supplied only with mineral oil;
Figure 3 is a schematic diagram of a rolling bearing;
Figure 4 is a schematic diagram of a hydro-dynamic bearing;
Figure 5 is a schematic diagram of a turbo-compressor train having a single lube
pump according to an exemplary embodiment;
Figure 6 is a schematic diagram of a turbo-compressor train having a single lube
pump electrically connected to the train according to an exemplary embodiment;
Figure 7 is a schematic diagram of a centrifugal compressor;
Figure 8 is a schematic diagram of another turbo-compressor train having a single
lube pump according to an exemplary embodiment; and
Figure 9 is a flowchart of a method for assembling a turbo-compressor train with a
single lube pump according to an exemplary embodiment.
DETAILED DESCRIPTION
The following description of the 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. The following
embodiments are discussed, for simplicity, with regard to the terminology and
structure of a gas turbine system connected to a compressor or generator. However,
the embodiments to be discussed next are not limited to these systems, but may be
applied to other systems that have plural machines connected to each other and
each machine has its own bearing system.
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.
According to an exemplary embodiment, the components of an entire turbocompressor
train are provided with rolling bearings. Thus, no component has
hydro-dynamic bearings, which is different from the traditional trains in which the
compressors have hydro-dynamic bearings. In this regard, it is noted that
traditional centrifugal compressors do not have rolling bearings because for this
solution it is more complex to compensate the axial thrust. Moreover, the dynamic
behavior of the compressor with rolling bearings is negatively influenced by the
high stiffness, while the solution with hydrodynamic bearings is much more
damped. In this exemplary embodiment, a single lube pump is used for all the
components, which results in a lower weight of the train, lower machine cost, lower
footprint, and higher reliability. By removing the mineral lube oil pump for the
hydro-dynamic bearings, depending on the machine, up to 250 k of energy may
be saved. Therefore, according to this exemplary embodiment, all the
components of the train use synthetic oil. The single lump pump may be part of
the train or may be an auxiliary component of the train. The lump pump may be
mechanically or electrically connected to the train.
Prior to discussing the arrangement of the novel train, a brief description of a
rolling bearing, hydro-dynamic bearing, mineral oil and synthetic oil is believed to
be in order. A generic rolling bearing 50 is shown in Figure 3. The rolling bearing
50 includes two races, an exterior race 52 and an interior race 54. These two
races guide rolling elements 56. The rolling elements 56 may be balls, as shown
in the figure, or may have other shapes, e.g., cylinders, etc. They may be tapered
or not. A cage 58 may be used for keeping the rolling elements at desired
distances one from the other. Other types of rolling bearings exist and are known
in the art.
The rolling bearing 50 shown in Figure 3 is traditionally lubed with synthetic oil or
grease, depending on the application. Synthetic oil is a lubricant that includes
chemical compounds which are artificially made (synthesized). The synthetic
lubricants can be manufactured using chemically modified petroleum components
rather than crude oil, but can also be synthesized from other raw materials.
Synthetic oil is used as a substitute for lubricant refined from petroleum when
operating in extreme temperature, because it generally provides superior
mechanical and chemical properties than those found in traditional mineral oils.
A generic hydro-dynamic bearing 60 includes a ring 62 that is configured to hold
plural pads 64, each having a working surface 64a. The pads 64 are retained by a
blocking plate 66 to prevent them from sliding in a rotational direction A when a
shaft (not shown) rotates at high speeds inside the ring 62, in direction A.
Corresponding retention plates 68, for preventing axial dislocation, retain the pads
64 in the proximity of the ring 62. Ring 62, blocking plate 66 and retention plates
68 define a predetermined volume in which pad 64 may pivot about a retaining
head (not shown). Mineral oil is provided on the working surface 64a so that an oil
film forms between the rotating shaft (not shown) and the pads 64.
The mineral oil is a liquid by-product of the distillation of petroleum to produce
gasoline and other petroleum based products from crude oil. The mineral oil
includes mainly alkanes (typically 5 to 40 carbons) and cyclic paraffins, related to
petroleum jelly (also known as "white petrolatum").
As discussed above, according to an exemplary embodiment, a turbo-compressor
train is configured to have only rolling bearings and no hydro-dynamic bearings.
Thus, when the compressor in the turbo-compressor train is a centrifugal
compressor, no hydro-dynamic bearings are used. In this regard, it is noted that
the conventional centrifugal compressors do not use rolling bearings but only
hydro-dynamic bearings.
Figure 5 shows an exemplary embodiment of a turbo-compressor train 100 having
all components provided with rolling bearings and no hydro-dynamic bearings.
The turbo-compressor train 00 includes a compressor 102 fluidly connected to a
combustion chamber 104 in which fuel and air are mixed together and ignited.
The hot gasses are provided to an expander 106 whose shaft is rotated by the
expansion of the hot gasses. The expander 106 may be an axial expander. A
shaft 108 of the expander 106 may be connected to a shaft 110 of a centrifugal
compressor 112 and also to the compressor 102. A shaft of the compressor 102
may be connected to an auxiliary gear box 114 that is configured to transmit
rotational motion to a shaft of a pump 116. The pump 116 may be the lube pump
for the synthetic oil necessary to the rolling bearings of the various components of
the turbo-compressor train.
According to an exemplary embodiment illustrated in Figure 6 , a train 200 includes
all the components shown in Figure 5 for the train 100 except that the pump 216 is
not part of the train. Further, the pump 216 is not mechanically (rotational motion)
connected to the train. In this exemplary embodiment, the pump is supplied with,
for example, electrical power from a power source 218 (e.g., power grid or a power
generator of the train). In this regard, it is noted that all the embodiments
discussed in this application (e.g., Figures 5 and 8) may have the pump either
mechanically or electrically connected to the train. Further, the pump may be or
not part of the train, depending on the application.
According with an exemplary embodiment, the pump 116, the auxiliary gearbox
114, the compressor 102, the expander 106, and the centrifugal compressor 112
each has rolling bearings. Thus, according to this exemplary embodiment, a
single lube pump is used and the only oil used is the synthetic oil. In one
application, the centrifugal compressor 112 may be replaced by a generator. In
this case, the generator has rolling bearings and not hydro-dynamic bearings.
Because the rolling bearings may not support enough axial trust in comparison to
the hydro-dynamic bearings, a dedicated thrust balance system (developed by the
assignee of this patent application) may be necessary.
A generic centrifugal compressor 140 modified as discussed above is shown in
Figure 7 and is defined by the fact that air intake reaches along an X direction, at
position 142, an impeller 144 and exits along a Y direction at position 146 having
increased the speed of the air due to the centrifugal motion through the impeller
144. The impeller 144 is shown connected to the shaft 110, which is supported
by the rolling bearings 148 and 150.
Returning to Figure 5, it is noted that piping 170 connects the lube pump 116 to
each of the components of the turbo-compressor train for supplying the necessary
synthetic oil. According to an exemplary embodiment illustrated in Figure 8, a
gearbox 180 may be provided between the shaft 108 of the expander 106 and the
shaft 110 of the centrifugal compressor or generator 112. In this case, the
gearbox 180 is configured to use synthetic oil and, if necessary, rolling bearings.
According to an exemplary embodiment illustrated in Figure 9 , a method for
assembling a train as discussed above is not described. The method includes a
step 900 of mechanically connecting a gas turbine to a centrifugal compressor; a
step 902 of mechanically or electrically connecting a lube pump to the gas turbine;
and a step 904 of providing each of the gas turbine, the centrifugal compressor
and the lube pump only with rolling bearings and the lube pump is configured to
pump synthetic oil.
The disclosed exemplary embodiments provide a turbo-compressor and a method
for providing rolling bearings to each component of the turbo-compressor. It
should be understood that this description is not intended to limit the invention. On
the contrary, the exemplary embodiments are intended to cover alternatives,
modifications and equivalents, which are included in the spirit and scope of the
invention as defined by the appended claims. Further, in the detailed description
of the exemplary embodiments, numerous specific details are set forth in order to
provide a comprehensive understanding of the claimed invention. However, one
skilled in the art would understand that various embodiments may be practiced
without such specific details.
Although the features and elements of the present exemplary embodiments are
described in the embodiments in particular combinations, each feature or element
can be used alone without the other features and elements of the embodiments or in
various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any
person skilled in the art to practice the same, including making and using any
devices or systems and performing any incorporated methods. The patentable
scope of the subject matter is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples are intended to be within
the scope of the claims.
CLAIMS
1. A turbo-compressor train, the train comprising:
a gas turbine configured to transform thermal energy into mechanical
energy;
a centrifugal compressor having a shaft connected to a shaft of the gas
turbine; and
a single lube pump configured to provide synthetic oil to the gas turbine,
and the centrifugal compressor,
wherein the gas turbine, the centrifugal compressor and the single lube
pump each has only rolling bearings.
2 . The train of Claim , wherein the gas turbine comprises:
a compressor configured to compress air;
a combustion chamber configured to receive the compressed air from the
compressor and to ignite the compressed air after mixing it with fuel; and
an expander configured to receive hot gases from the combustion chamber
and transform the thermal energy of the hot gases into rotational motion.
3. The train of Claim or Claim 2, further comprising:
an auxiliary gearbox connecting a shaft of the gas turbine to a shaft of the
lube pump and the auxiliary gearbox is configured to work with synthetic oil, or
a power source configured to provide energy to activate the pump.
4 . The train of any preceding Claim, further comprising:
piping connecting the lube pump to the gas turbine and the centrifugal
compressor for distributing the synthetic oil.
5. The train of any preceding Claim, wherein no mineral oil is used in any
component of the train.
6 . The train of any preceding Claim, wherein the gas turbine includes an
axial expander.
7. The train of any preceding Claim, further comprising:
a gearbox configured to mechanically connect a shaft of the gas turbine and
a shaft of the centrifugal compressor.
8. The train of any preceding Claim, further comprising:
an auxiliary gearbox connecting a shaft of the gas turbine to a shaft of the
lube pump and the auxiliary gearbox is configured to work with synthetic oil;
piping connecting the lube pump to the gas turbine and the centrifugal
compressor for distributing the synthetic oil;
a gearbox configured to mechanically connect a shaft of the gas turbine and
a shaft of the centrifugal compressor; and
the gas turbine further comprises:
a compressor configured to compress air,
a combustion chamber configured to receive the compressed air
from the compressor and to ignite the compressed air after mixing it with
fuel, and
an expander configured to receive hot gases from the combustion
chamber and transform the thermal energy of the hot gases into rotational
motion.
9. A turbo-compressor train, the train comprising:
a gas turbine configured to transform thermal energy into mechanical
energy;
a generator having a shaft connected to a shaft of the gas turbine; and
a single lube pump configured to provide synthetic oil to the gas turbine,
and the generator,
wherein the gas turbine, the generator and the single lube pump each has
only rolling bearings.
10. A method for assembling a turbo-compressor train, the method
comprising:
mechanically connecting a gas turbine to a centrifugal compressor;
mechanically or electrically connecting a lube pump to the gas turbine; and
providing each of the gas turbine, the centrifugal compressor and the lube
pump only with rolling bearings and the lube pump is configured to pump synthetic
oil.