DE102017124689A1 - Axial compressor, comprising juxtaposed rotors that rotate in opposite directions - Google Patents

Abstract

The invention relates to an axial compressor comprising a first motorized shaft (12) arranged along an axis carrying a succession of forward rotors (14, 16) rotating in a so-called forward rotational direction, each axially on the upstream side receiving a gas stream to compress it, passing it to the other side, said compressor being characterized in that, axially in the direction of the flow, at least one forward rotor (14, 16) has a rearward rotor (22, 24) supported by a second shaft (20) and driven in rotation in the direction reverse to the forward direction, disposed adjacent to the forward rotor (14, 16).

Description

The present invention relates to an axial compressor, which can provide in particular a large flow rate, in particular for the compression of air or gas in the industry, as well as a system which is equipped with such an axial compressor.

A known turbocharged type of engine, in particular by the document FR-A1-2940247 1, includes a free turbine driven by the combustion gases generated in a combustion chamber, comprising a succession of rotors that are alternatively driven by a planetary gear in opposite directions of rotation. The two sets of rotors each drive a propeller, one rotating in a first direction, conventionally referred to as forward, and the other rotating in the reverse or reverse direction, these two propellers successively in an annular channel surrounding the turbine are arranged, wherein a drive cold air flow is generated.

This device, which solves particular problems of the turbo-engines, makes it possible to equalize the torque at the two propellers and produce a stream of cold air which does not involve residual yawing, thereby reducing in particular the mechanical stresses on the fastening systems of this turbo-engine.

Moreover, one known type of compressor, called an axial compressor, has an inlet air flow arranged along the axis of a motorized shaft passing through a series of axial stages, each successively comprising a rotor connected to that shaft, then a directional stator, on the other side exit along the same axis.

At the output of the axial compressor, one or more centrifugal compressors comprising a centrifugal turbine can be arranged, which in turn increase the pressure level of the starting gases, in order in particular to obtain high compression rates.

Each axial stage first comprises the rotor equipped with compaction blades, which axially absorbs and accelerates the gas flow rate, giving it a certain tangential velocity. Then comes the strainer-equipped stator, which provides a reverse tangential velocity to direct the flow, eliminating this tangential component of its velocity, thereby increasing the pressure of the gas.

The cross-section of the successive axial stages is decreasing to account for the volume of gases which decreases as a function of their compression.

Axial compressors, comprising three or four stages of compression, are commonly used in the industry, the entirety of the rotors of these stages being driven by a shaft at the same speed.

The design of this type of compressor is generally optimized to obtain performance at a design point, also called a design point, which gives the best yield with a special combination of throughput and compression rate with a specific drive speed of the rotor.

However, the design of an axial compressor for the industry raises particular problems different from those encountered in the propulsion of an aircraft, in particular the drives illustrated in the above-mentioned prior art.

On either side of the design point, performance generally decreases more or less rapidly, depending on the design chosen. Thus, there is not much flexibility to be active in a wide range of functions while maintaining good performance near the design point, posing problems for a number of industrial applications.

This type of compressor also poses problems associated with the axial space requirement, defined in particular by the number of stages comprising each a rotor and a stator which are arranged successively and have a certain length.

The present invention has the particular object to avoid these disadvantages of the prior art.

It proposes, for this purpose, an axial compressor comprising a first motorized shaft disposed along an axis carrying a succession of forward rotors rotating in a so-called forward direction, each receiving a gas flow axially on the upstream side, around it to compress, passing it to the other side, said compressor axially in the direction of the flow after at least one forward rotor comprises a reverse rotor, which is supported by a second shaft and is driven in rotation in the direction opposite to the forward direction, in addition to Forward rotor is arranged, characterized in that the rotors comprise rotor blades having a variable inclination.

In this way, depending on the development of the functional parameters of the compressor, the inclination of the rotor blades can be adjusted to optimize the performance.

An advantage of this axial compressor is that by calculating the vanes of each reverse rotor and the speed of rotation to give the gas a tangential pulse substantially opposite that of the previous forward rotor, a stream is obtained in the compressor which remains substantially axial , with possibilities of high performance over a wide range of applications.

Further, each reverse rotor which produces a compression directing the axial yaw rate of the stream constitutes a compression stage. The intermediate stators of the prior art compressors are omitted, thereby making it possible to reduce their axial footprint with a same number of compression stages , A much shorter compressor is produced.

The axial compressor according to the invention may further comprise one or more of the following features, which may be combined with each other.

Advantageously, the forward rotor comprises a reverse rotor after itself. In this way, the airflow is directed each time in the tangential direction.

According to one embodiment, the first shaft and the second shaft are each driven by a drive independent of the other drive.

According to another embodiment, the first shaft and the second shaft are connected by a transmission system which reverses the direction of rotation. In this way, the axial compressor requires only one drive to drive both shafts.

In this case, in particular, the transmission system may comprise a planetary gear.

In addition, the axial compressor at the entrance or at the exit of the entirety of the rotors may comprise a stator comprising guide vanes which are alignable by pivoting about their axis.

The invention also relates to a compression plant which is equipped with an axial compressor comprising one of the preceding features, wherein it comprises at least one radial compressor at the outlet of the axial compressor.

The invention also relates to an air separation plant by cryogenic distillation comprising a compressor as described above or an air compression plant as described above, wherein the compressor or the compression plant is connected to a distillation column system for supplying compressed air to at least one column of the system.

The separation plant may include a compressor and / or a fan upstream of the air compression plant. The compression system can compress the air from the air pressure or from a pressure at least 2 bar above the air pressure.

In the prior art, the air compressors of an air separation plant, which compresses the entire supply air from the air pressure, a very poor performance when the air flow is reduced to a value below 70% of the nominal flow rate. Furthermore, it is necessary to keep the output pressure constant. Counter rotation technology allows the compressor to better adapt to variable throughput.

• - 1 ein Schema ist, das eine Anlage, umfassend einen erfindungsgemäßen Axialverdichter, der mit zwei Antrieben ausgestattet ist, und einen Radialverdichter, darstellt; und
• - 2 ein Schema, das eine Anlage, umfassend einen Axialverdichter nach einer Variante, der mit einem einzigen Antrieb ausgestattet ist, und zwei Radialverdichter, darstellt.

The invention will be better understood, and further features and advantages will become more apparent from the study of the following description, given by way of example and with reference to the accompanying drawings, in which:

• - 1 Fig. 2 is a diagram illustrating a plant comprising an axial compressor according to the invention, equipped with two drives, and a centrifugal compressor; and
• - 2 a diagram illustrating a system comprising an axial compressor according to a variant, which is equipped with a single drive, and two centrifugal compressor.

1 FIG. 10 illustrates an air compressor including an axial compressor including an input on the upstream side. FIG 2 , which receives the room air, which enters the compressor axially, and an air outlet on the downstream side 4 ,

The exit 4 provides the air, which has been brought to a first level of compression, to a centrifugal compressor comprising a radial turbine 6 which further increases the compression level to provide increased pressure.

The axial compressor comprises four rotors 14 . 16 . 22 . 24 , which are aligned on a same major axis, which successively from the first to to the fourth, starting from the downstream side, and following each other directly with a small axial clearance.

A first electric motor 10 , which is arranged on the axis in the air flow upstream of the totality of the rotors, drives with its shaft 12 , which is aligned downstream with a direction of rotation, called forward direction, the first 14 and the third rotor 16 Called forward rotors.

A second electric motor 18 , which is arranged on the axis in the air flow downstream to the totality of the rotors, drives with its shaft 20 , which is aligned upstream with a counter or reverse rotational direction, the second 22 and the fourth rotor 24 , Called reverse wheels, on. The wave 20 of the second electric motor 18 passes freely through the third rotor 16 to the second rotor 22 reach upstream to power it.

The second electric motor 18 also drives with a downstream shaft 26 emerging from the air duct of the axial compressor, the turbine 6 of the centrifugal compressor.

For the axial compressor is a series of rotors 14 . 16 . 22 . 24 obtained, which are arranged axially next to each other, which rotate in opposite directions in succession and each lead to an increase in the compression level of the air.

Advantageously, the inclination of the blades of each rotor and the rotational speeds of the two waves 12 . 20 determined to be at the output of each reverse rotor 22 . 24 to obtain a yaw rate of the air that is substantially zero. In addition, each gives backward rotor 22 . 24 the received air flow a Tangentialimpuls that substantially to that of the previous forward rotor 14 . 16 is awarded, is opposite.

It should be noted that in known manner, the pitch of the rotor blades is variable depending on the radius of the rotor blades to adjust their angle at each point as a function of the tangential velocity in order to obtain the desired velocity vector.

Variable pitch rotor blades may be arranged to provide greater flexibility, particularly for rotational speed adjustment, including an actuation system integrated into the hub of each rotor which allows the blades to rotate about their radial axis.

In this way, a substantially axial air flow is obtained at the output of the axial compressor, which has no yaw motion, which limits the losses and increases the power.

In addition, in particular to avoid rotor blades with variable adjustment, at the entrance of the first rotor 14 or at the exit of the last rotor 24 a stator is added, comprising automatically by pivoting about its axis orientable vanes, which guide at each point the velocity vector of the air flow to adjust its angle. This improves performance regardless of throughput.

Moreover, calculations and tests have shown that the intrinsic performance of the succession of forward and reverse rotors is good over a relatively wide range of uses. In particular, a greater distance from the design point, which gives the best performance with a particular mix of throughput and compression rate, is possible with a performance that is little diminished.

In particular, the speed of the electric motors can be independent 10 . 18 depending on the operating conditions, in particular the desired throughput and the desired compression rate, be set with an optimization of performance. For this purpose, motors with variable speed can be used.

The number of stages of the axial compressor is not limited. 1 represents four stages, but for example, six or eight may be provided.

It should be noted that a prior art axial compressor comprises a stator arranged thereafter for each rotor, thereby substantially doubling its axial length in comparison with the compressor according to the invention.

2 represents an air compressor, comprising an axial compressor, at its output 4 Air, which has been brought to a first level of compression, successively to a first centrifugal compressor, which with a first turbine 6 equipped, then to a second centrifugal compressor, with a second turbine 32 equipped to greatly increase the compression level.

The axial compressor comprises the second electric motor 18 , the same way through the second wave 20 which is oriented upstream, the second 22 and the fourth rotor 24 drives.

A gearbox 30 comprising a planetary gear system between the third 16 and the fourth rotor 24 is arranged, takes the movement of the second wave 20 and a support of the reaction forming frame, not shown, for a reverse or counter-rotation movement on the first shaft 12 which is oriented upstream and the first 14 and the third rotor 16 wearing.

The first wave 12 extends upstream, exiting the air duct of the axial compressor to the turbine 32 to drive the second centrifugal compressor.

In the same way, successive reverse rotations are obtained for each rotor having a speed deviation caused by the gear ratios of the gears in the housing 30 arranged planetary gear is regulated.

The in 2 shown axial compressor, comprising a single electric motor 18 with a single tax system, is easier and more economical than the one in 1 shown. However, it has less flexibility to optimize its function due to the dependence of the speed ratios between the two sets of rotors.

The air compression plant of the two figures may be used to supply air to a cryogenic distillation column system to separate the air to form an oxygen-enriched fluid and / or a nitrogen-enriched fluid. The compression system can compress the air from the air pressure or from a pressure at least 2 bar above the air pressure. It can thus correspond to a main air compressor or a secondary compressor.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• FR 2940247 A1 [0002]

Claims (9)

An axial compressor comprising a first motorized shaft (12) disposed along an axis carrying a succession of forward rotors (14, 16) rotating in a so-called forward rotational direction, each receiving a gas flow axially on the upstream side compressing it, passing it to the other side, comprising axially in the direction of the flow after at least one forward rotor (14, 16) a reverse rotor (22, 24) carried by a second shaft (20) and rotating in the is driven to the forward direction reverse direction, which is arranged adjacent to the forward rotor (14, 16), characterized in that the rotors (14, 16, 22, 24) comprise rotor blades having a variable inclination. Axial compressor to Claim 1 , characterized in that each forward rotor (14, 16) includes a rearward rotor (22, 24) therethrough. Axial compressor to Claim 1 or 2 , characterized in that the first shaft (12) and the second shaft (20) are each driven by a drive (10, 18) independent of the other drive. Axial compressor to Claim 1 or 2 , characterized in that the first shaft (12) and the second shaft (20) are connected by a transmission system (30) reversing the direction of rotation. Axial compressor to Claim 4 , characterized in that the transmission system (30) comprises a planetary gear. Axial compressor according to one of the preceding claims, characterized in that it comprises, at the inlet or outlet of the assembly of rotors (14, 16, 22, 24), a stator comprising guide vanes which are orientable by pivoting about their axis. Compression plant, which is equipped with an axial compressor according to one of the preceding claims, characterized in that it comprises at least one radial compressor (6, 32) at the outlet of the axial compressor. Air separation plant by cryogenic distillation, comprising a compressor according to one of Claims 1 to 6 or an air compression system Claim 7 wherein the compressor or the compression plant is connected to a distillation column system for supplying compressed air to at least one column of the system. Plant after Claim 8 comprising a compressor and / or a fan upstream of the air compressor or the compressor.

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