Patent Description:
<CIT> discloses a gas turbine engine including a centrifugal compressor having a rotor and a thrust bearing disposed in connection with the rotor. <CIT> discloses a turbo-compressor train with a gas turbine engine, a load compressor, an accessory gearbox, a lube pump and ball bearings. <CIT> discloses a gas turbine engine with an alternator using synthetic oil, ball bearings and a single oil pump. <CIT> discloses a turbogenerator with a single oil pump for a gas turbine engine and a generator. <CIT> discloses a turbo-compressor train with a gas turbine engine, a centrifugal compressor and an additional gearbox.

Gas turbine engines are used in many sectors of the industry, from military to power generation. They are used mainly to produce electrical energy. However, some gas turbine engines are used to propel various vehicles, airplanes, ships, etc. In the oil and gas field, the gas turbine engines are used to drive compressors, pumps and/or generators. As shown in <FIG>, a gas turbine engine <NUM> may be connected to a compressor or generator <NUM> and to an auxiliary equipment <NUM>. A gear box <NUM> or other equipment may be provided between the gas turbine engine <NUM> and the compressor or generator <NUM>. All these elements form a turbo-compressor train <NUM>.

The gas turbine engine <NUM> may include a compressor <NUM> that is configured to receive a gas (e.g., air) at an input <NUM> and to provide the gas compressed to a predetermined pressure at an outlet <NUM>. The compressed gas is then input to a combustor <NUM> where it is mixed with a fuel provided from a line <NUM>. The mixture of gas and fuel is ignited and the hot gases at high pressure are provided to an input <NUM> of an expander <NUM>. The exhaust gases are then released at output <NUM> of the expander <NUM>.

The expansion of the hot gases through the expander <NUM> determines a rotation of a rotoric part (not shown) which is coupled, through the gear box <NUM> to a shaft of the compressor <NUM>. Thus, the compressor <NUM> is driven by the expander <NUM>. One or more of the components of the turbo-compressor train <NUM> 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 of conventional turbo-compressor trains are discussed next.

<FIG> show the train <NUM> of <FIG> 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 <FIG> need two lube pumps, one for each type of bearings while the arrangement shown in <FIG> 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 <FIG> 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.

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 engine 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 the present invention, the components of the entire turbo-compressor 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 configuration, 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 <NUM> kW of energy may be saved. Therefore, according to this configuration, all the components of the train use synthetic oil. The single lump pump is part of 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 <NUM> is shown in <FIG>. The rolling bearing <NUM> includes two races, an exterior race <NUM> and an interior race <NUM>. These two races guide rolling elements <NUM>. The rolling elements <NUM> 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 <NUM> 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 <NUM> shown in <FIG> 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 <NUM> includes a ring <NUM> that is configured to hold plural pads <NUM>, each having a working surface 64a. The pads <NUM> are retained by a blocking plate <NUM> to prevent them from sliding in a rotational direction A when a shaft (not shown) rotates at high speeds inside the ring <NUM>, in direction A. Corresponding retention plates <NUM>, for preventing axial dislocation, retain the pads <NUM> in the proximity of the ring <NUM>. Ring <NUM>, blocking plate <NUM> and retention plates <NUM> define a predetermined volume in which pad <NUM> 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 <NUM>.

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 <NUM> to <NUM> carbons) and cyclic paraffins, related to petroleum jelly (also known as "white petrolatum").

As discussed above, according to the present invention, a turbo-compressor train is configured to have only rolling bearings and no hydro-dynamic bearings. Thus, since 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.

<FIG> shows an embodiment of a turbo-compressor train <NUM> according to the present invention having all components provided with rolling bearings and no hydro-dynamic bearings. The turbo-compressor train <NUM> includes a compressor <NUM> fluidly connected to a combustion chamber <NUM> in which fuel and air are mixed together and ignited. The hot gasses are provided to an expander <NUM> whose shaft is rotated by the expansion of the hot gasses. The expander <NUM> may be an axial expander. A shaft <NUM> of the expander <NUM> is connected to a shaft <NUM> of a centrifugal compressor <NUM> and also to the compressor <NUM>. A shaft of the compressor <NUM> is connected to an auxiliary gear box <NUM> that is configured to transmit rotational motion to a shaft of a pump <NUM>. The pump <NUM> is the lube pump for the synthetic oil necessary to the rolling bearings of the various components of the turbo-compressor train.

According to a comparative example illustrated in <FIG> not forming part of the present invention, a train <NUM> includes all the components shown in <FIG> for the train <NUM> except that the pump <NUM> is not part of the train. Further, the pump <NUM> 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 <NUM> (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., <FIG> and <FIG>) have the pump mechanically connected to the train.

According to the present invention, the pump <NUM>, the auxiliary gearbox <NUM>, the compressor <NUM>, the expander <NUM>, and the centrifugal compressor <NUM> each has rolling bearings. Thus, according to this configuration, a single lube pump is used and the only oil used is the synthetic oil. In one application not forming part of the present invention, the centrifugal compressor <NUM> is 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) is necessary.

A generic centrifugal compressor <NUM> modified as discussed above is shown in <FIG> and is defined by the fact that air intake reaches along an X direction, at position <NUM>, an impeller <NUM> and exits along a Y direction at position <NUM> having increased the speed of the air due to the centrifugal motion through the impeller <NUM>. The impeller <NUM> is shown connected to the shaft <NUM>, which is supported by the rolling bearings <NUM> and <NUM>.

Returning to <FIG>, it is noted that piping <NUM> connects the lube pump <NUM> to each of the components of the turbo-compressor train for supplying the necessary synthetic oil. According to an embodiment illustrated in <FIG>, a gearbox <NUM> may be provided between the shaft <NUM> of the expander <NUM> and the shaft <NUM> of the centrifugal compressor or generator <NUM>. In this case, the gearbox <NUM> is configured to use synthetic oil and rolling bearings.

According to an exemplary embodiment illustrated in <FIG>, a method for assembling a train as discussed above is not described. The method includes a step <NUM> of mechanically connecting a gas turbine engine to a centrifugal compressor; a step <NUM> of mechanically or electrically connecting a lube pump to the gas turbine engine; and a step <NUM> of providing each of the gas turbine engine, 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 modifications, which are included in the 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.

Claim 1:
A turbo-compressor train (<NUM>) for use in the oil and gas field industry to drive a compressor, the train comprising a gas turbine engine (<NUM>, <NUM>, <NUM>), a centrifugal compressor (<NUM>), an auxiliary gearbox (<NUM>), a lube pump (<NUM>), a bearing system and a thrust balance system,
the gas turbine engine including a compressor (<NUM>) fluidly connected to a combustion chamber (<NUM>) in which fuel and air are mixed together and ignited, the hot gases being provided to an expander (<NUM>), the gas turbine engine (<NUM>, <NUM>, <NUM>) configured to transform thermal energy into mechanical energy, and
the centrifugal compressor (<NUM>) having a shaft (<NUM>) connected to a shaft (<NUM>) of the expander (<NUM>),
characterized in that
the lube pump is a single lube pump (<NUM>) connected to oil piping (<NUM>) and configured to provide synthetic oil to the gas turbine engine (<NUM>, <NUM>, <NUM>), the centrifugal compressor (<NUM>) and the auxiliary gearbox (<NUM>),
the auxiliary gearbox (<NUM>) connecting a shaft of the compressor (<NUM>) to a shaft of the lube pump (<NUM>), and the auxiliary gearbox (<NUM>) is configured to work with synthetic oil, and
the bearing system of the entire turbo-compressor train (<NUM>) being provided with rolling bearings, wherein no component of the train (<NUM>) has hydro-dynamic bearings and no mineral oil is used in any component of the train (<NUM>),
wherein the bearings of the gas turbine engine (<NUM>, <NUM>, <NUM>), the centrifugal compressor (<NUM>), the single lube pump (<NUM>) and the auxiliary gearbox (<NUM>) each comprise only rolling bearings configured to be lubricated by the synthetic oil provided by the single lube pump (<NUM>); and
wherein the thrust balance system is configured to compensate axial thrust in the turbo-compressor train (<NUM>).