DESCRIPTION

The invention relates to cryogenic engineering, namely, to a device for separation of multicomponent mixture, as well as to a nozzle channel for the said device, and may be used for liquefying gases, treating them or for extracting one or several target components from a mixture.

Centrifugal separation devices are widely used for separating or liquefying gases. These devices swirl a gas flow by using a swirler and supply the flow to the inlet of a nozzle channel for separation. Gas is cooled due to adiabatic expansion in the nozzle channel of a number of these devices, including this one, and the process of liquid phase condensation takes place. Under the influence of centrifugal forces acting in a swirled flow condensate drops are thrown to the channel walls, thus forming a liquid phase layer on them, which is collected with the use of a device for liquid phase collection. This device may be of various designs.

A device for separation of a multicomponent gas mixture is known in the art (see, RF Patent RU2348871, F25J3/00, 10.03.2009 III), which comprises a prechamber having a means for swirling a gas flow arranged therein, a nozzle channel for separation of a flow, a means for collecting a liquid phase, and a subsonic diffiiser or a combination of a supersonic diffuser and a subsonic diffuser.

The above-mentioned analogous solution is the closest to the claimed device for separation. However, this solution has drawbacks associated with the presence of non-stationary processes near a minimum (critical) section of the channel as well as with non-stationary positions of compression shocks and separation regions in the expanding (divergent) segment of the nozzle channel. The presence of rapid non-stationary processes results, on one side, in difficulties during a computational analysis of the separation channel operation and, on the other side, in lowering the efficiency of separation processes.

A nozzle channel for separation of a gas flow is known in the art (see, RF Patent RU2353764, E21B 43/34, 111), which comprises a convergent segment and a divergent segment with a cylindrical channel of an ejector mixing chamber and an inlet channel of a liquid collection device arranged therebetween. This analogous solution is the closest to the claimed nozzle channel.

One drawback of the above-mentioned known means is the presence of a high level of turbulence typical for a mixture flow in an ejector mixing chamber, which lowers the device efficiency, since intensive turbulent mixing of a flow takes place in the mixing chamber, and, thus, a part of liquid drops is returned to the flow due to the turbulent diffusion process.

The objective of the claimed invention is to provide a more efficient device for separation of a multicomponent mixture.

The technical effect of the claimed invention is to lower a pulsation level in a flow and, consequently, to increase separation efficiency and decrease total-pressure losses in a flow.

The stated technical effect is achieved by the design of the nozzle channel for separation due to the fact that it comprises a convergent segment, a divergent segment and a cylindrical segment arranged there between, the cylindrical segment having a generating line length more than 0.1D, where D is the diameter of the cylindrical segment, and the divergent segment is provided with an annular ledge in the form of a step which plane is perpendicular to the channel axis. Also, the stated technical effect is achieved in particular embodiments of the separation channel due to the facts that:

- the said annular ledge is made so as its height is greater than the displacement thickness in the boundary layer before the ledge,

- the outlet of the cylindrical segment is provided with an additional ledge.

The said technical effect is achieved in the design of the device for separation of a multicomponent mixture due to the fact that it comprises a prechamber with a mixture swirler arranged therein, a nozzle channel for separation, as connected to the prechamber in the said design, and a unit for collecting drops and/or solid particles.

Also, the said technical effect is achieved in particular embodiments of the device for separation due to the facts that:

- the flow swirler is made as a central body and blades attached to it as well as to the prechamber walls; the diameter of the central body is not greater than the minimum diameter of the channel,

- the flow swirler is made as the central axisymmetric channel with additional channels connected thereto, which are in communication with a multicomponent mixture source, an angle between the axis of each additional channel and the cross point of the walls of the central and additional channels being not less than 45° in the cross-section of the central channel, which cross-section passes through the axes of the additional channels,

- the unit for collecting a liquid phase is made as a chamber connected to the nozzle channel, the chamber wall being provided with perforations and/or an annular slot.

Unlike the analogous solution 111, the nozzle channel of the device for separation has the annular ledge enabling to fix a compression shock position with least losses of total pressure (totalpressure). The cylindrical segment (segment of constant section) having a length greater than 0.1D (where D is a diameter of the cylindrical segment) ensures depression of pulsations occurring in the channel at non-stationary condensation during transition from subsonic to supersonic section. And the inventors have determined that the combination of the said structural elements unexpectedly ensures a significant increase in the flow separation efficiency.

Fig. 1 shows the most preferable embodiment of the claimed device for separation. The device comprises: the prechamber 1 with the mixture flow swirler arranged therein, the nozzle channel 2 for mixture flow separation, the unit 3 for collection of a liquid phase formed, and a diffuser 4 (optional), which all are arranged in series.

According to the claimed invention, the nozzle channel 2 for separation of a multicomponent mixture comprises a convergent (narrowing) segment 5 and a divergent (expanding) segment 6, a cylindrical segment 7 (segment with a constant cross section) being arranged therebetween. A minimum length L _seg of the said segment 7 is 0.1D, where D is a diameter of the cylindrical segment (the channel minimum diameter). Most preferably, the cylindrical segment length L _seg = (0.2-0.5)D. This condition ensures the most efficient depression of pulsations arising in a flow in the channel convergent segment 5.

An annular ledge 8, which end plane is perpendicular to the channel axis, is located in the divergent segment 6 of the nozzle channel. A height h of the ledge 8 should be greater than a displacement thickness of a boundary layer before the said ledge. This condition enables to stabilize a shock position and a flow separation zone.

Displacement thickness is determined with the use of well-known gas- dynamic relations (see, for example, Abramovich G.N. "Applied Gas Dynamics", Part 1 , Nauka Publishers. 1991 , p. 302) as well as of numerical computations of equations relating to a turbulent flow in a channel.

Particular embodiments of the invention may comprise an additional ledge (not shown in the drawings) that ensures additional stabilization of a flow.

According to one aspect of the invention, a central body 9 with blades 10 arranged around it, which are installed at an angle to the cross-sectional plane of the prechamber 1 , may be used as a flow swirler, the blades 10 being secured both to the surface of the central body 9 and on the inner surface of the prechamber 1.

Fig. 2 shows the construction of another embodiment of the swirler that is made as a central axisymmetric channel 11 preferably embracing the central body 9 and forming a part of the prechamber 1, and additional channels 12 that are connected to the channel 11 and are in communication with a source 13 of a multiphase mixture. In the cross section of the central channel 11, which passes through the axes 14 of the additional channels, the angle φ between the axis 14 of each additional channel and the line 15 connecting the axis of the central channel 1 1 with the cross point of the walls of the central channel 1 1 and an additional channel 12 is at least 45°. In other words, the angle φ between the axis 14 of each additional channel and a normal 15 drawn from the axis of the central channel 1 1 to its surface on the cross point of the walls of the central channel and an additional channel 12 (to any two points) is at least 45°.

The selection of the angle φ from the range of 45° < φ < 90° enables to make a swirler with minimum total pressure losses for a given flow angular momentum, when a mixture passes through the swirler channels. Preferably, a diameter D _c of the central body 9 is not greater than the minimum diameter D of the channel (i.e., channel diameter at the cylindrical segment) (D _C ≤D).

If the dimensions of the central body are greater than the minimum diameter of the nozzle channel, then, as follows from calculations and experimental data, great irregularity of total pressure on the channel radius occurs, which is conditioned by a higher rotational velocity of a flow near the channel axis after the central body. This circumstance prevents flow total pressure from uniform restoring after its stagnation and results in losses of mixture total pressure at the device outlet.

The unit 3 for collection of a liquid phase may be made as a chamber connected to the channel, which wall is provided with perforations and/or an annular slot.

The device may also include a diffuser 4 installed for partial restoration of mixture total pressure.

The claimed device can be operated as follows:

A multicomponent mixture (in particular, a gas mixture or a gas-liquid mixture) enters the prechamber 1, where it passes through a swirler (e.g., the blades 10). Then, the swirled flow passes to the convergent segment 5 of the nozzle channel and acquires a required acceleration, and then to the cylindrical segment 7 where gas flow pulsations are depressed. After this, adiabatic expansion of the gas occurs in the divergent segment 6 of the channel, which is accompanied by a decrease in pressure, temperature and by formation of liquid phase drops having a size greater than 0.5 microns that are thrown to the channel walls by centrifugal forces. At that time, the compression shock position and the flow separation zoneare fixed with minimum losses of total pressure in the divergent segment 6 owing to the annular ledge 8. An enriched gas-liquid flow, as formed near the walls, enters the unit 3 for collection of a liquid phase, and a depleted gas mixture leaves the device through the diffuser 4.

Thus, the claimed device for separation, owing to the use of the separation channel having the above-described construction, enables to increase separation efficiency and reduce losses of total pressure when a mixture flows through the device.