RU2645100C1 - Peripheral device for reducing heat carrier leaks - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: peripheral seal of unbanded turbine stages containing helical grooves on the outer circumference at the radial clearance region of unbanded turbine stage. In the peripheral area of unbanded turbine stages, there are annular electric magnets of spline type generating electromagnetic field in the radial clearance region in 10⁹ to 10¹³ Hz frequency range, and the helical grooves are at an angle of 75° to the axis of the turbomachine.

EFFECT: reduction of heat carrier leaks through the radial clearance of turbine stages of unbanded type and thereby generated vibration and sound energy.

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Description

The invention relates to the field of turbine engineering and can be used in unbounded steps of steam and gas turbines.

In the peripheral region of the unbundled working grid of the turbine stage, the flows have a pronounced three-dimensional character. Once in the area of the outer circumference of the stage, the energy carrier is divided into the main interscapular flow, peripheral (in the space between the peripheral end surface of the blades and the outer circumference) in the radial gap between the main interscapular flow and the surface of the outer circumference of the stage), which have high energy . The interaction at the top of the working blades of the slit, peripheral and main flows causes the development of a vortex layer at the convex surface of the blades, which, twisting into a spiral, forms the core of the rotating working medium. The unsteadiness of the flow entering the impeller contributes to the instability of the flow in the boundary layer at the periphery of the working lattice and the formation of local stall vortex paths. Under these conditions, gas movement is accompanied by significant energy losses, the generation of vibrational processes and powerful sound pressure.

A seal is known for a radial clearance of a turbomachine, comprising a ring mounted on the housing, annular grooves are made on the surface of the blades of which are characterized in that, in order to increase operating efficiency by reducing the end coolant leakages, the seal is provided with a vibrator around the ring, made in the form of a piezoceramic cylinder with its inner and outer surfaces with electrodes fixed on the inner surface in the ring, and at the ends on the body (see A.S. USSR, No. 1471661, CL F01D 11/08, 1996). The disadvantage of this device is the additional energy consumption and the creation of vibration loads on the elements of the turbomachine, which can cause their resonance.

To reduce the leakage of the working fluid, a compressor rotary device can be used, containing ribs located in an additional annular cavity in the compressor housing located above the working blade of the compressor stage and communicating with the compressor flow part, at an angle to the longitudinal axis of the compressor, equipped with ribs that are located under at the same angle to the surface facing the flowing part, in an additional annular cavity, connected to it as a whole and have a wedge-shaped e sharpening at the ends (see RU No. 2282754, CL F04D 27/02, 2006). The disadvantage of this device is its lack of effectiveness in comparison with the proposed constructive option.

The objective of the invention is the creation of a device to reduce leakage of the coolant through the radial clearance of the turbine stages of unbandled type and the generated vibration and sound energy.

This task is achieved in that the peripheral seal of the unbranded turbine stages, containing helical grooves located in the radial clearance region of the unbranded turbine stage, characterized in that slotted type ring electromagnets are installed in the peripheral zone of the unstrained turbine stages, generating an electromagnetic field in the frequency range from 10 ⁹ up to 10 ¹³ Hz, and the helical grooves are made at an angle of 75 ° to the axis of the turbomachine.

This invention proposes the creation on the outer contour of the impeller of screw profile grooves, providing the effect of "locking" the flow at the periphery.

It is possible to additionally reduce the intensity of a highly turbulent vortex flow on the outer contour of the working blades at high Reynolds numbers due to laminarization of the flow — a decrease in the level of fluid anisotropy in the peripheral boundary layer.

In order to form an isotropic form of the energy carrier flow in the region of radial clearances of the turbine impellers, external influence on the gas molecules in the boundary layer by an alternating magnetic field with a frequency range from 10 ⁹ to 10 ¹³ Hz should be organized, which is adequate to the frequency of their natural vibrations.

It is possible to implement this method of damping the vibroacoustic activity of a gas by creating an alternating magnetic field. For this purpose, in the area of the radial clearance of the turbine stage, an annular slot electromagnet should be installed.

The present invention will allow to laminarize the peripheral flow, reducing the leakage of the working fluid through the radial clearance and thereby increase the turbine efficiency, significantly reduce the level of radiated sound energy, eliminate stalling phenomena in the peripheral radial clearance zone of unshielded working gratings, which will increase the reliability and efficiency of turbomachines.

The invention is illustrated.

In FIG. 1 shows a peripheral seal with helical grooves on the outer circumference of the impeller.

In FIG. 2 shows the profile grooves of a screw type (type B in FIG. 1).

In FIG. 3 shows a flow diagram of a working fluid inside a helical groove.

In FIG. 4 is a diagram of the flow of the working fluid at the outer contour of a stage equipped with helical grooves made at an angle α _to (75 °) to the axis of the machine (view A in Fig. 1).

In FIG. 5 shows the dependence of the efficiency of the stage on the design of the external contour.

A device for reducing leaks through the radial clearance in (Fig. 1) of an unbranded turbine stage, consisting of a guide apparatus 1 and an impeller 2, is a profile type screw grooves 3 and a slotted type 5 ring electromagnet mounted on the compressor outer circumference 4.

The device operates as follows: in the process of interaction between the slit and main flows, the core of a rotating working medium, getting inside the screw type 3 groove (Fig. 1, 2, 3), affects the main flow at the periphery at a certain angle to the axis of the rotor, makes it move towards the interventional gap of the stage, thereby reducing the magnitude of the peripheral leakage of the coolant (Fig. 4).

Studies of the efficiency of this type of sealing device were performed on a dynamic air bench using models of a highly loaded turbine compartment.

Tests of turbine stages were performed at five angles of inclination of the sealing grooves α _{to the} impeller 2 (relative to the axis of the machine) α _k = 82 °, 78 °, 75 °, 71 ° and 68 ° and the radial clearance value δ = 0.5 mm ( Fig. 1).

The dependence of the stage efficiency on the external contour design is shown in FIG. 5: 6 - for a smooth ring; 7 - for a ring with a helical groove at α _k = 75 °.

The efficiency of the initial version of the turbine stage (with a smooth peripheral ring) had the value η _ref = 0.82 at the optimal operating mode (Fig. 1, 5).

Studies of the turbine compartment in the presence of screw grooves 3 on the peripheral bypass allowed us to establish that the greatest increase in stage efficiency was obtained at α _к = 75 °, where its increase was 0.8% (Fig. 5). Under these conditions, the minimum levels of vibration and noise generated in the turbine compartment are also recorded.

To further reduce leakages of the working fluid and the vibroacoustic activity of the stage, the peripheral contour of the structure should be equipped with a spline-type annular magnetic device 5 with corresponding electromagnetic characteristics (Fig. 1).

The adjustment of the magnetic system should be carried out during the development of the power unit during bench tests of the turbine compartment.

Thus, the use of peripheral contours in unbranded turbine stages equipped with helical grooves with an angle of inclination of 75 ° and an electromagnet generating a magnetic field with a frequency of 10 ⁹ ... 10 ¹³ Hz will allow laminarizing the flow in the region of the radial clearances of the impellers, significantly increasing their efficiency and vibration reliability, significantly reduce the level of radiated sound energy.

Claims (1)

A peripheral seal of unstrained turbine stages, containing on the outer contour of the helical grooves in the region of the radial clearance of the unstrained turbine stage, characterized in that in the peripheral zone of the unstrained turbine stages, ring-type electromagnets are installed that generate an electromagnetic field in the radial clearance region in the frequency range from 10 to ⁹ 10 ¹³ Hz, and the helical grooves are made at an angle of 75 ° to the axis of the turbomachine.

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