RU2470178C1 - Device for increasing stable operation of axial-radial hydraulic turbine (versions) - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to hydraulic machinery and may be used in suction tubes of radial-axial hydraulic turbines at hydroelectric power stations. Proposed device comprises nozzle 1 for fluid feed to suction tube 2 beyond outlet edge of wheel 3. Nozzle 1 is made in the wall of tube 2 beyond outlet edge of wheel 3 to communicate via, at least, one bypass line 4 with downstream tube section 2. Nozzle outflow face represents annular slit or holes on tube 2 that make skewed face of nozzle 1 and ledge on tube wall. Ledge edge nearby wheel 3 extends beyond ledge edge, further from wheel 3.

EFFECT: reduced flow pulsations, stable operation.

11 cl, 9 dwg

Description

The invention relates to hydraulic engineering and can be used in the suction pipes of radial-axis hydraulic turbines in hydroelectric power plants to increase the stability of the radial-axis hydraulic turbines.

Known suction pipe of a radial-axial hydraulic turbine containing diffuser inlet and outlet sections connected by a curved elbow (Stepenkov Yu.A. Device and repair of equipment of machine shops of hydroelectric power plants. M: Higher school, 1985, p.22, 38).

A disadvantage of the known suction pipe is an increased level of cavitation erosion and noise due to flow pulsations in the flow part.

Known suction pipe of a radial-axial hydraulic turbine containing diffuser inlet and outlet sections connected by a curved elbow, while it is equipped with profiled blades mounted along its flowing part on the convex and concave walls of the curved elbow with a slope downstream, and bypass pipelines communicating interscapular channels concave wall of a curved knee with interscapular channels of its convex wall. This device allows to reduce the level of cavitation erosion and to reduce the noise level by reducing the intensity of flow pulsations in the suction pipe (RU No. 2188965, MPK F03B 11/04, 09/10/2002).

A disadvantage of the known device is that it does not allow to adequately reduce the formation of a vortex bundle in the axial region behind the output cut of the impeller of a radial-axial hydraulic turbine, which does not allow to eliminate vibrations due to pulsations of the hydrodynamic pressure of the liquid in the suction pipe when the turbine operates on an off-design mode.

Closest to the claimed invention in technical essence and the achieved result is a device for increasing the stability of a radial-axial hydraulic turbine, comprising a nozzle for supplying a liquid medium to the suction pipe in the region behind the exit cut of the impeller of a radial-axial hydraulic turbine (see application WO 2007/142709 , CL F03B 11/00, 12/13/2007).

The disadvantage of the known device adopted as a prototype, as well as the reason that impedes the achievement of the desired technical result when using the aforementioned known device, is that this technical solution does not allow to reduce vibration due to pulsations of the hydrodynamic pressure of the liquid in the suction pipe when the turbine is in off-design mode .

This technical solution does not allow automatically without the use of special diagnostic equipment, such as pressure sensors and control means, to ensure the supply of a liquid medium to the area behind the exit slice of the impeller in the required quantity.

The claimed technical solution allows to reduce the intensity of the flow pulsations in the suction pipe in the area behind the exit section of the impeller of the hydraulic turbine and by automatically regulating the supply of a liquid medium (working medium of the turbine) into the area beyond the outlet section of the impeller to increase the stability of the radial-axis hydraulic turbines.

This problem is solved, and the technical result is achieved due to the fact that, according to the first embodiment, the device for increasing the stability of the radial-axial hydraulic turbine includes a nozzle for supplying a liquid medium to the suction pipe, in the area beyond the output cut of the impeller of the radial-axial hydraulic turbine, the nozzle is made in the wall of the suction pipe behind the exit cut of the impeller of the radial-axial hydraulic turbine and is communicated from the entrance to it by means of at least one bypass pipe wires with a downstream portion of the suction pipe along the flow of the working medium from a radial-axial hydraulic turbine, from the outlet cross-section side the nozzle is made in the form of an annular gap or holes in the wall of the suction pipe with the formation of an oblique cut of the nozzle exit section and a step on the wall of the suction pipe, along the flow in the suction pipe, the edge of the ledge, located closer to the impeller of the radial-axial hydraulic turbine, protrudes above the edge of the ledge, located further from the impeller of the radial-axial hydraulic the turbines.

The nozzle may be multi-tiered.

The angle of inclination of the axis of the longitudinal section of the nozzle to the plane of the cross section of the suction pipe is preferably from 0 to 60 ° in the direction of flow in the suction pipe.

The bypass line or bypass lines may span the suction pipe along a helix.

The bypass pipe in place of its communication with the suction pipe is preferably provided with a guide visor made on the inner surface of the suction pipe.

According to a second embodiment, a device for increasing the stability of a radial-axial hydraulic turbine includes a nozzle for supplying a liquid medium to the suction pipe into the region behind the outlet cut of the impeller of the radial-axial turbine, while the nozzle or nozzles are mounted on the wall of the suction pipe behind the outlet cut of the impeller - an axial hydraulic turbine and each nozzle is communicated from the entrance to it by means of a bypass pipe fixed to the wall of the suction pipe with a downstream section m draft tube downstream of it in the working environment of the Francis turbine.

The nozzle can be directed in the direction of rotation of the working medium in the suction pipe.

The inlet section of the bypass pipe is preferably directed tangentially towards the flow of the working medium in the suction pipe.

The bypass pipe or bypass pipes can be located on the surface of the suction pipe in the plane of the longitudinal section of the suction pipe or at an angle to the plane of the longitudinal section of the suction pipe.

The nozzle can be made in the form of a side hole in the wall of the bypass pipe.

In the course of the study, it was revealed that the operation of Francis hydraulic turbines and reversible radial-axis hydraulic turbines at partial load conditions leads to undesirable hydrodynamic phenomena when the impeller flows around a water stream. The most clearly indicated phenomena are manifested during the operation of hydraulic turbines far from the calculated operating point corresponding to the maximum value of efficiency. The consequence of the operation of the turbine in a purely non-design mode may be an emergency due to fatigue loads accumulated in the metal due to strong vibrations due to pulsations of the hydrodynamic pressure in the liquid. Pressure pulsations at the exit of the impeller and in the suction pipe (up to resonance phenomena) are caused, inter alia, by the presence and precession of the vortex bundle in the indicated region due to rupture of the continuity of the water flow. The formation of two-phase structures rotating in a bundle with a pronounced phase boundary in the central part of the channel determines the presence of complex, often counter-circulating fluid flows in the core and in the peripheral sections of the suction pipe. The implementation and transformation of these vortex zones occurs only due to the redistribution of energy inside the flow of working water of the turbine and its losses to maintain these "self-organizing" structures. The presence of a central vapor-gas precessing cavity is a consequence of the separation of the lighter fraction and its concentration in the middle part of the suction pipe due to the large centrifugal forces and the tangential components of the flow rates at the exit of the impeller. The values of these speeds increase as the operating point of the turbine moves away from its calculated value in the nominal mode.

The reason for the existence of a narrow range of stable operation of radial-axis hydraulic turbines is the presence of a precessing vortex bundle in the turbine suction pipe that appears in off-design operating modes due to flow continuity rupture under the action of large centrifugal forces and tangential components of the velocity vector in the suction pipe. The consequence of the presence of the bundle in the suction pipe is the strong vibrations of the turbine unit as a whole, which is the main reason for the unstable operation of the radial-axial turbine. The main cause of flow continuity rupture with the formation of a vortex rope in off-design turbine operating modes is a mass defect (compared to the design mode) and the presence of tangential components of the fluid velocity (working medium) at the exit of the impeller. (The tangential components of the velocity at the exit of the impeller are absent in the calculated mode.) This phenomenon is inherent only in radial-axial (RO) and reversible radial-axial (ORO) hydroturbines - when they operate under partial load conditions.

To expand the range of stable operation of the hydraulic turbine by eliminating the mass defect in the suction pipe and eliminating the flow swirl in off-design modes (partial hydraulic turbine power modes), the energy of the swirling flow at the outlet of the hydraulic turbine impeller is used to supply water from the lower region of the suction pipe to the upper region, which allows you to expand the range of stable operation of the turbine and eliminate the mass defect.

The execution of the nozzle with an oblique cut is used to increase the circulation speed by creating an additional vacuum directly in the oblique cut, and the final mixing is carried out behind the oblique cut in the flow of the working medium from the impeller. The additional mass of the working fluid — water — from the lower region of the suction pipe compensates for the mass defect in the off-design mode while expanding the range of stable operation of the radial-axial hydraulic turbine. The device is self-regulating using negative feedback embedded in the mechanism of ejection of the working medium from the lower region of the flow to the upper one, in this case, the kinetic energy of the swirling flow is partially converted to potential with the simultaneous movement of the working medium into the gap of the continuity of flow with the formation of a mixing zone located behind the output section of the nozzle or nozzles, and the flow of the working medium from the impeller running onto the nozzle or nozzles creates a vacuum in the vicinity of the exit cross section of the nozzle, where the working medium is sucked from the lower region of the working medium flow in the suction pipe. The mixture of media occurs in a common stream in the immediate vicinity of the outlet edge of the impeller at the beginning of the suction pipe.

The invention is illustrated by drawings.

Figure 1 shows a diagram of a first embodiment of a device with a suction pipe of a radial-axial hydraulic turbine with bypass pipelines and single-tier nozzles.

Figure 2 shows the suction pipe of a radial-axial hydraulic turbine with bypass pipelines and a multi-tiered nozzle.

Figure 3 shows a first embodiment of a step on the wall of the suction pipe.

Figure 4 shows a second embodiment of a step on the wall of the suction pipe.

Figure 5 schematically shows an embodiment of an annular multi-tiered nozzle.

6 schematically shows a suction pipe of a second embodiment of the device with bypass pipelines on the surface of the suction pipe.

In Fig.7 shows a bottom view (view K of Fig.6) on the suction pipe with bypass pipelines.

On Fig schematically shows a bypass pipe with a nozzle and an inlet section in the form of a side hole in the wall of the bypass pipe.

Figure 9 schematically shows the output section of the bypass pipe with a nozzle and a guide visor.

A device for increasing the stability of operation of a radial-axial hydraulic turbine according to the first embodiment includes a nozzle 1 for supplying a working medium to the suction pipe 2 in the area behind the output cut of the impeller 3 of the radial-axial hydraulic turbine. The nozzle 1 is made in the wall of the suction pipe 2 behind the outlet slice of the impeller 3 of the radial-axial hydraulic turbine and is communicated from the entrance to it by means of at least one bypass pipe 4 with a downstream portion of the suction pipe 2 along the working medium flowing from the working medium wheels 3 radial-axial hydraulic turbines. From the side of the outlet section, the nozzle 1 is made in the form of an annular slit or holes in the wall of the suction pipe 2 with the formation of an oblique cut of the outlet section of the nozzle 1 and the step 5 on the wall of the suction pipe 2, with the edge 6 of the step 5 located closer to the suction pipe 2 to the impeller 3 of the radial-axial hydraulic turbine, protrudes above the edge 7 of the ledge 5, located further from the impeller 3 of the radial-axial hydraulic turbine.

The nozzle 1 can be multi-tiered.

The angle α of inclination of the axis of the longitudinal section of the nozzle 1 to the plane of the cross section of the suction pipe 2 is preferably from 0 to 60 ° in the direction of flow in the suction pipe 2.

The bypass pipe 4 or the bypass pipes 4 may span the suction pipe 2 along a helix (not shown).

The bypass pipe 4 in place of its communication with the suction pipe 2 is preferably provided with a guide visor 8, made on the inner surface of the suction pipe 2 and placed in front of the nozzle and the inlet section 9 of the bypass pipe 4.

According to a second embodiment, a device for increasing the stability of a radial-axial hydraulic turbine contains a nozzle 1 or several nozzles 1 can be made, mounted on the wall of the suction pipe 2 and evenly distributed over the cross section of the suction pipe 2 behind the outlet cut of the impeller 3 of the radial-axial hydraulic turbine. Each nozzle 1 is communicated from the entrance to it by means of a bypass pipe 4 fixed to the wall of the suction pipe 2 with a downstream portion of the suction pipe 2 along the working medium flow from it from a radial-axial turbine.

The nozzle 1 can be directed in the direction of rotation of the working medium in the suction pipe 2, and the nozzle 1 can be cylindrical or tapering along the flow in it.

The inlet section 9 of the bypass pipe 4 is preferably directed in a tangential direction towards the flow of the working medium in the suction pipe 2.

The bypass pipe 4 or the bypass pipes 4 can be located on the surface of the suction pipe 2 in the plane of the longitudinal section of the suction pipe 2 or at an angle to the plane of the longitudinal section of the suction pipe 2.

The nozzle 1 can be made in the form of a side hole in the wall of the bypass pipe 4.

The crossover pipe 4 in cross section may be round, oval or in the form of a polygon.

A device to increase the stability of the radial-axial turbine works as follows.

The working medium leaving the impeller 3 of the hydraulic turbine enters the suction pipe 2 and flows around the nozzle 1, creating a vacuum in the outlet section of the nozzle 1, which causes a part of the working medium to flow from the downstream region of the suction pipe 2 to the nozzle 1 through the bypass pipe. The working medium received in the suction pipe 2 from the nozzle 1 is mixed with the working medium from the impeller 2, which allows, as mentioned above, to compensate for the mass defect in the off-design mode of operation of the turbine, which, in turn, allows to increase the stability of the turbine. The device is self-regulating using negative feedback embedded in the mechanism of ejection of the working medium from the lower region of the flow to the upper one, since the amount of working medium supplied from the lower region of the suction pipe to the upper one depends entirely on the flow regime of the working medium behind the impeller 3. If large discontinuities, then the flow rate in the region of the nozzle 1 increases, which leads to an increase in the flow of the working medium from the nozzle 1 due to the higher vacuum created for the output section of the nozzle 1 is a faster flow of the working medium in the suction pipe 2, and vice versa.

Claims (11)

1. A device for increasing the stability of the radial-axial hydraulic turbine, including a nozzle for supplying a working medium to the suction pipe into the region behind the output cut of the impeller of the radial-axial hydraulic turbine, characterized in that the nozzle is made in the wall of the suction pipe behind the output cut of the impeller of the radial axial hydraulic turbine and communicated from the entrance to it by means of at least one bypass pipe with a downstream portion of the suction pipe along the flow of the working medium from it from a non-axial hydraulic turbine, from the side of the outlet cross section the nozzle is made in the form of an annular gap or one or more holes in the wall of the suction pipe with the formation of an oblique cut of the outlet cross section of the nozzle and a step on the wall of the suction pipe, with the edge of the step located closer to the suction pipe to the impeller of the radial-axial hydraulic turbine, protrudes above the edge of the ledge located further from the impeller of the radial-axial hydraulic turbine. 2. The device according to claim 1, characterized in that the nozzle is multi-tiered. 3. The device according to claim 1, characterized in that the angle of inclination of the axis of the longitudinal section of the nozzle to the plane of the cross section of the suction pipe is from 0 to 60 ° in the direction of flow in the suction pipe. 4. The device according to claim 1, characterized in that the bypass pipe or bypass pipelines cover the suction pipe along a helical line. 5. The device according to claim 1, characterized in that the bypass pipe in place of its communication with the suction pipe is equipped with a guide visor made on the inner surface of the suction pipe. 6. A device for increasing the stability of a radial-axial hydraulic turbine, including a nozzle for supplying a working medium to the suction pipe into the region behind the output cut of the impeller of the radial-axial hydraulic turbine, characterized in that the nozzle or nozzles are fixed to the wall of the suction pipe behind the output cut of the impeller a radial-axial hydraulic turbine and each nozzle is communicated from the entrance to it by means of a bypass pipe fixed to the wall of the suction pipe with a downstream portion of the suction pipe s downstream of it the working fluid from the radial-axial water turbine. 7. The device according to claim 6, characterized in that the nozzle is directed towards the rotation of the working medium in the suction pipe. 8. The device according to claim 6, characterized in that the inlet section of the bypass pipe is directed in the tangential direction towards the flow of the working medium in the suction pipe. 9. The device according to claim 6, characterized in that the bypass pipe or bypass pipes are located on the surface of the suction pipe in the plane of the longitudinal section of the suction pipe. 10. The device according to claim 6, characterized in that the bypass pipe or bypass pipes are located on the surface of the suction pipe at an angle to the plane of the longitudinal section of the suction pipe. 11. The device according to claim 6, characterized in that the nozzle and the inlet section of the bypass pipe are made in the form of a side hole in the wall of the bypass pipe.

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