RU2442027C1 - Radical compressor's axial bearer unloading unit with the operating wheel arrangement "back to back" - Google Patents

Abstract

FIELD: mechanics.

SUBSTANCE: device refers to compressing and can be used in radial compressors primarily in the bi-sectional ones with the wheel arrangement "back to back" and providing the quick control of the axial force and reducing the load on the axial bearers. Axial bearer's unloading unit of the bi-sectional radial compressor, including the unloading device as a dummy piston located between compressor's sections and high-low pressure sections, formed by the walls of the unloading device and the compressor's operating wheels , installed on the rotor, in that, the mentioned low-pressure section communicates with low-pressure section from the suction side through a throttling device, done with the ability to change its flow passage at the rotor's axes displacement.

EFFECT: quick control of the axial force and reducing the load on the axial bearers.

3 cl, 2 dwg

Description

The invention relates to the field of compressor engineering and can be used in centrifugal compressors, mainly two-section with the location of the wheels "back to back".

Known units for unloading the thrust bearing of a turbomachine by changing the pressure in the cavities of the unloading device (see, for example, SU 903570, publ. 07.02.82, SU 641167, publ. 05.01.1979, SU 469815, publ. 05/05/1975) depending on the parameter determining the axial force acting on the thrust bearing. In the unloading units, the deflection parameter of the throttle devices — elastic plates in the thrust bearing, the oil pressure under the bearing pads, or the temperature of the pads are used as the determining parameter of the axial force.

The disadvantage of these nodes is the low reliability and inertia of the feedback system "sensor - executive body".

There is also a knot for unloading a thrust bearing, which includes a self-regulating unloading (throttle) device - a “gas-static heel” (Shnepp VB “Axial stability of a circulating centrifugal compressor with an unloading device.” In the lennimikhimmash's collection of reports “Centrifugal Compressor Machines”, ed. , 1966, p. 175-185). When the unit operates, when the compressor operating mode changes, the rotor moves, changing the throughput of the labyrinths forming the discharge chamber, so that a new pressure is established in this chamber, sufficient to restore the rotor balance in the new mode.

In multimode centrifugal compressors, the diameter of the intersection unloading device (dumis) is selected in the range near the design point based on the permissible loads of the thrust bearing, taking into account the possible wear of the labyrinth seal of the dumis. When the compressor is operating at increased flow rates or during emergency stops, when there is a sharp decrease in pressure for each section, the resulting axial force acting on the rotor can change both direction and magnitude and exceed the allowable forces on the thrust bearing.

The use of the aforementioned thrust bearing unloading unit by changing the pressure in the cavity of the unloading device due to the throughput of the labyrinths in multimode compressors with the location of the unloading device (dummies) between the sections in some cases leads to a negative reaction of the rotor behavior, i.e. any movement of the rotor leads to an increase in the axial force acting on the rotor in the direction of movement.

The technical result of the invention is to increase reliability due to the speed of axial force control and reduce the load on the thrust bearing in multi-mode two-section centrifugal compressors with the arrangement of the wheels "back to back".

The technical result is achieved by the fact that the unloading unit of the thrust bearing of a two-section centrifugal compressor includes an unloading device located between the compressor sections in the form of a dumis and a low and high pressure cavity, formed by the walls of the unloading device and compressor impellers mounted on the rotor, while the said low pressure cavity is communicated with a low pressure section on the suction side through a throttle device configured to change its passage cross section for axial movement of the rotor.

The throttle device can be made in the form of an annular hole formed between the surface of the annular protrusion made on the wall of the compressor impeller and the surface of the annular recess made in the intersection wall, while the annular hole is in communication with the low-pressure section on the suction side through channels made in intersection wall.

In addition, through said protrusion can be made through holes connecting the low-pressure cavity with a gap between the wall of the impeller and the intersection wall to equalize the pressure in the specified cavity and the gap.

Thus, the above set of features provides a speed control axial force and reduce the load on the thrust bearing.

The invention is illustrated using the drawings.

Figure 1 shows a section of the inventive site.

Figure 2 shows an enlarged fragment of figure 1.

The unloading unit of the thrust bearing 1 of a two-section centrifugal compressor contains a housing 2, in which a two-section rotor 3 is installed, and includes an unloading device located between the compressor sections in the form of a dummis 4 with a low pressure cavity 5 formed by the walls of the dumis 4 and the impeller 6 of the compressor located on the rotor 3. The second impeller 7 is located on the other side of the dumis 4, while the walls of the dumis 4 and the impeller 7 form a cavity 8 of high pressure. The cavity 5 on the suction side communicates with the low-pressure section through the throttle device 9, made in the form of an annular hole 10 formed between the surface of the annular protrusion 11, made on the wall of the impeller 6 of the compressor, and the surface of the annular recess, made in the intersection wall 12. 10 communicates with the low pressure section on the suction side through channels 13 made in the intersection wall 12. To equalize the pressure in the cavity 5 and in the gap between the wall of the impeller 6 and ezhsektsionnoy wall 12 in the protrusion 11 holds several through-holes 14 connecting the cavity 5 with the specified clearance. The throttle device 9 is made with the possibility of changing its bore with axial movement of the rotor 3.

When the compressor is operating, any deviation from the nominal mode, resulting in a change in the axial force and axial shift of the rotor 3, will lead to a change in the relative position of the rotor 3 relative to the intersection wall 12 - the distance h in the throttle device 9 will either increase (when the rotor 6 is moved to the left) or decrease ( when the rotor 6 is shifted to the right).

When the rotor 3 is shifted to the left, the cool section of the throttle device 9 increases, the pressure in the cavity 5 decreases, the value of the axial force acting on the low-pressure rotor 3 decreases relative to the nominal value by

,

,

where Δp (kg / cm ² ) is the decrease in pressure in cavity 5 (low pressure);

f _R.K. (cm ² ) is the area of the end face of the impeller in contact with the gas in the cavity 4;

f _g (cm ² ) - the same for dummies 4.

The axial load acting on the thrust bearing 1 is reduced by ΔF _axes.

When the rotor 3 is shifted to the right, the orifice of the throttle device 9 decreases, the pressure in the cavity 5 rises, and the axial force increases. ΔF _axes, tending to return the rotor 3 in the nominal position, the load on the thrust bearing 1 is reduced again.

For the real design of two-section rotor 3

F _R.K. = 2800 cm ²

f _g = 415 cm ²

and Δ _p = 2 kgf / cm ² .

The decrease in axial force will be ΔF _os ~ 4770 kgf.

Thus, the axial position of the rotor 3 is self-regulating when the compressor operating mode changes due to a change in pressure in the discharge cavity 5, and the thrust bearing 1 accepts less load.

Claims (3)

1. The unloading unit of the thrust bearing of a two-section centrifugal compressor, including an unloading device located between the compressor sections in the form of a dumis and a low and high pressure cavity, formed by the walls of the unloading device and compressor impellers mounted on the rotor, characterized in that the said low pressure cavity is in communication with section of the low pressure on the suction side through a throttle device configured to change its flow area with axial per rotor room. 2. The node according to claim 1, characterized in that the throttle device is made in the form of an annular hole formed between the surface of the annular protrusion made on the wall of the impeller of the compressor and the surface of the annular recess made in the intersection wall, while the annular hole is in communication with the section low pressure on the suction side through channels made in the intersection wall. 3. The node according to claim 2, characterized in that the said protrusion is made through holes connecting the low pressure cavity with a gap between the wall of the impeller and the intersection wall.

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