Blade system for wheel of hydraulic turbine

FIELD: turbine engineering.

SUBSTANCE: blade system comprises blades whose inlet and outlet edges are made so that the working section of the inlet blade edge adjacent to the hub prevents against cavitation.

EFFECT: enhanced efficiency and reliability.

2 cl, 5 dwg

 

The invention relates to the field of power engineering, specifically hydrocarbonate, in particular to a device of guide vanes of the impeller radial-axial turbines (like Francis).

In the prior art it is known that traditionally used the design of the blades, guide vanes of the impeller of the turbine type Francis, including rim, hub and blades with input and output edges, characterized by the fact that in relation to the direction of rotation of the impeller inlet edge of each blade, as a rule, is ahead compared to the location of the attachment points on the input flange to the rim or located on the same radial plane with this point, while the output edge of each blade is usually ahead of the connection point of the output flange to the hub, or lies in the same radial plane with this point [Reference turbines: Directory / Webundies, Chabrowski and others; under the General editorship Nov. - L.: engineering, 1984, 496 pages].

Usually voznikaem problem in the operation of the turbines with impeller type Francis is the development of a strong cavitation at the inlet edges of the blades, and the strongest in areas connecting the input edges of the blades to the rim. A consequence of the development of cavitation are the two who is the erosion of the edges and surfaces of the blades and their destruction.

Known technical solution to reduce the intensity of cavitation erosion at the inlet edges of the blades of the impeller and providing a device intake of atmospheric air into the cavitation zone. However, it is not effective enough, and, in addition, the implementation of such decisions on the units that must operate in synchronous condenser mode, requires a sophisticated device turbines due to the necessary use of locking devices on the rotating shafts of the units, which lowers the degree of reliability of the turbine unit (RF Patent for the invention №2166121 published BI from 27.04.2001,).

Known technical solution to reduce the intensity of cavitation erosion at the inlet edges of the blades of the impeller radial-axial turbines and consisting in the installation of barrier ribs on the side of the low pressure surface of the blade in the direction downstream of the input edge (RF Patent for the invention №2157465 published BI from 10.10.2000,).

However, it is not effective enough, because it can lead to reduced efficiency of the turbine due to the effect of "shock" of the leakage flow on set of ribs.

Closest to the proposed device in conjunction with the social characteristics and selected as a prototype is a device of guide vanes of the impeller of the turbine type Francis, which contains a rim, a hub, blades, directly connected with the rim and the hub, whereby the surface of each blade is curved and provided with input and output edges with defined relationships of the diameters of the location of the connection points of a trailing edge of the blades to the hub and the rim, and the input edge of each blade on the said plot is made with a deviation in the direction of flow of the incoming stream is less than the deviation of the area of a trailing edge of the same blade, and the point of connection of the input edges of the blades to the rim is ahead of the point connecting the input edge of the blade to the hub, and a connection point of a trailing edge of the blades to the rim located in front of the attachment point of a trailing edge of the same blade to the hub, the latter is lower than a certain middle point located on the desktop portion of the input edge of the blade (U.S. Patent US 6135716, priority dated 24.10.2000,, PCT application WO No. 98/05863, the priority of the applicant (Norway) from 02.08.1996 year).

A noticeable reduction in the level of cavitation erosion at the inlet edges of the blades of the impeller on the main operating modes of the turbine is ensured by the fact that the slope of the input edges from the hub to the rim in the direction of rotation of the impeller on the prototype reduces the speed of flow I is de in the impeller at the rim and thereby reduce the dynamic pressure reduction at the inlet edges of the blades near the rim, and also on the surface area of the rim near the input edges.

For reasons that impede the achievement of specified following technical result when using the known device the prototype, is that the device guide vanes of the turbine prototype does not exclude the possibility of pulsations of flow when the turbine in a wide range of loads and costs and is characterized by a greater magnitude of the pressure pulsation of the flow when the turbine in partial or incomplete loads compared to the blade apparatus of traditional design with the inlet edges of the blades, inclined from the hub to the rim against the course of the rotation.

The technical problem solved by the invention is the design of guide vanes of the impeller radial-axial turbines, which will virtually eliminate the cavitation phenomena and their consequences on the input edges of the blades, to ensure optimum hydrodynamics and stability of current flow in the flow area of the turbine as partial, and in a wide range of permanent working loads up to the maximum possible, significantly increase the value achieved when the turbine efficiency and significantly expand the range of loads, characterized by reliable operation of the GI is aturbine, extend turnaround and thereby significantly reduce operating costs.

To achieve the desired technical result of the proposed device guide vanes of the impeller radial-axial turbines, containing rim, hub, blades, directly connected with the rim and the hub, each of which has input and output edges of a curved profile, the working parts are made with certain deviations in relation to the connection points of the input and output edges of each blade to the hub and the rim, characterized by the fact that the profile of the input edges of each blade section from the point of attaching the blades to the hub to a point M located on the entrance edge at the maximum distance from a plane parallel to the axis of rotation of the wheel and passing through the connection point of the input edges of the blades to the rim and the hub, is made with a slope away from the hub to the rim along the rotational direction so that the connection point of the input edges of each blade to the hub is located in front of the direction of rotation of the impeller with respect to the point M and the point of connection of the input edges of each blade to the rim, is located behind, in the direction of rotation, the connecting points of the input edges of the blades to the hub or lying down with her on one radial the second plane, the plot of the input edge of each blade is located between the point M and the point of connection between the input flange to the rim is made with a slope away from the hub to the rim in the direction of rotation of the impeller so that the connection point of the input edges of the blades to the rim is located ahead of the point M and the point of connection of a trailing edge of the blades to the rim is in the direction of rotation of the impeller front attachment point off the edge to the hub or lying down with her in the same radial plane, and the profile of a trailing edge formed in such a way that the point K is located on the output edge, he has the maximum distance from a plane passing through the connecting points of the trailing edge to the hub and the rim and parallel to the axis of rotation of the wheel. Thus the spatial position of the point M on the input edge of each blade is defined by the distance Hmbetween the connection point of the input edge of the blade to the rim of the impeller and the point M, and the value of Nmis 10-40% of the size of the input edges of the blade Hi and angle ϕmformed by a radial plane passing through the point M on the input edge of each blade and a radial plane passing through the point of connection of the input edges of each blade, and defined by the formula:

ϕm =(5°-20°)·b0/D1,

and the spatial position of the point K on the output edge of each blade is defined by the distance Htobetween the connection point of a trailing edge of the blades to the rim of the impeller and the point K, and the value of Ntois 10-40% of the size of a trailing edge of the blade, and the angle ϕtoformed by a radial plane passing through the point K on the output edge of each blade and a radial plane passing through the point of connection of a trailing edge of each blade, and defined by the formula:

ϕto=(5°-20°)·b0/D1,

where b0- the height of the guide vanes of the turbine, a D1the magnitude of the diameter on which are the connection points of the input edges of each of the blades of the impeller to the rim.

The essence of the invention lies in the fact that by mathematical modeling and taking into account the results of model tests of full-scale prototypes of the impeller is defined profile settings input and output edges of each of the blades, which are made so that the working portion of the input edge of the blade adjacent to the hub, made with certain spatial parameters that are optimal from the point of view of solving the invention on the basis of what some tasks, profile and has a slope away from the hub to the rim along against the rotation of the impeller turbines. The plot of the input edges of the blade adjacent to the rim, also made with certain spatial parameters, has the opposite with the given parameters, the slope in the direction from the hub to the rim in the direction of rotation of the impeller. Profile of a trailing edge formed in such a way that the points on the output edge is removed in an optimal way from the plane passing through the connecting points of the trailing edge to the hub and the rim and parallel to the axis of rotation of the wheel. At this point of junction of the trailing edge of the blade to the rim is in the direction of rotation of the impeller front attachment point off the edge to the hub or lying down with her in the same radial plane. In General, formed by the present invention, the surface profile of each of the blades of the impeller has a so-called sickle-shaped configuration. This allows the proposed construction of optimal spatial profile of the blades of the impeller without the effects of cavitation on the inlet edges of the blades and to provide optimal hydrodynamics and stability of current flow in the flow area of the turbine as partial, and in a wide range of constant workloads.

Based on on the izania device guide vanes of the impeller radial-axial turbines and his work can be concluded, the proposed invention for the first time solved the problem almost complete elimination of the causes of cavitation processes on the edges of the blades in the emerging stream flowing in megapascal area in blade apparatus turbines. Moreover, when implementing the invention in situ sample of guide vanes have been able to provide the highest value for the efficiency of the turbine in comparison with the known from the prior art and most effective designs of blades of the water turbine type Francis. This is because the portion of the input edge of the blade adjacent the hub to a much greater extent than the area of the blade adjacent to the rim, formed of hydrodynamic parameters of the flow in the Central part of the draft tube located behind the impeller, and determined the development of the Central vortex sheet is responsible for the occurrence of undesirable flow pulsations, usually occur at partial loads turbines. Traditionally performed the inclination of the blades in this area provides a good hydrodynamic stability turbines at partial loads. The portion of the input edge of the blade adjacent to the rim almost completely determines the velocity distribution of the incoming flow in this area and, as a consequence, from atstone for the emergence and development of cavitation process in areas of the input edges of the blades.

By the invention the inclination of the blades in said zone in the direction from the hub to the rim in the direction of rotation of the turbine eliminates the peak dynamic pressure reduction on the entrance edge and, consequently, to eliminate the cause of the phenomenon of cavitation on the inlet edge of the blade on the main operation modes of the turbine.

The obviousness of design decisions determined by a new set of essential features of the proposed device, which defines the spatial parameters of the input and the input edges, areas of surfaces of the blades of the impeller turbines that are optimal from the point of view of solving the invention technical problem. This allows you to get previously not achievable technical result, namely: at the same time, virtually eliminate cavitation and its effects on the input and output edges of the blades of the impeller of the turbine, the optimum hydrodynamics and stability of current flow in the flow area of the turbine as partial, and in a wide range of permanent working loads up to the maximum possible, significantly increase the value achieved when the turbine efficiency, and also to increase the load range, which is characterized by reliable operation of the turbine, to increase the turnaround time of samples of the ha and thereby significantly reduce operating costs.

Below are figures 1-6, explaining the essence of the invention. Device guide vanes of the impeller radial-axial turbine consists of the following elements: figure 1 shows a Meridian projection of the impeller, which shows the rim 1, the hub 2, the pen of one of the blades 3, United with the rim and the hub. Each blade has an input 4 and output 5 edges. Pen blades 3 characterized by the fact that the portion of the input edges between the connection point pen blades to the hub C1and some most remote against the direction of rotation parallel to the axis of rotation of the wheel plane And passing through the connecting points of the input flange to the rim and the hub (respectively B1and C1), point M is the slope from the hub to the rim against the direction of rotation.

Figure 2 schematically shows a top view of the pen blades 3. As can be seen from the drawing point C1located ahead in the direction of rotation from the point m and the point In1in the direction of rotation is behind the point of the C1or lies in the same radial plane with her. Accordingly, the portion of the input flange located between point M and point B1has a tilt from the hub to the rim in the direction of rotation, i.e. point B1attach the inlet edges of the blades to the rim raspolojeniea in the direction of rotation from the point M

You can also see that the point In2connection of a trailing edge of the blades to the rim is located ahead in the direction of rotation from C2compounds of this edge to the hub or lies in the same radial plane with her. When this output edge 5 at the point To, as far from the plane d-D, parallel to the axis of rotation of the wheel and passing through point C2and B2.

The figure 3 presents a view of the impeller on the side.

The figure 4 shows a plot of pressure pulsations on the draft tube wall model turbine with impellers according to the prior art (curve a) and on the proposed technical solution (curve "b"). As can be seen from figure 4, the impeller is made according to the proposed technical solution that provides a much smaller ripple of the stream than the prototype.

The figure 5 shows the pattern of distribution of pressure on the low pressure side of the pen blades, obtained on the basis of the decision task 3-dimensional flow in the turbine mode, the maximum efficiency of the turbine for the prototype.

The figure 6 shows the same picture drafts for the device according to the invention.

As can be seen from the data of figures 5 and 6, in both cases, the pressure of the stream at the inlet edge 4, is substantially higher than the pressure in the pen area of the blade, close to the output edge 5. This clearly proves the replacement of the giving opportunities for the development of cavitation on the inlet and outlet edges of the blades of blades of the turbine in accordance with the device according to the invention.

The proposed device guide vanes of the impeller radial-axial turbine operates as follows.

The incoming flow of water (working fluid)that has passed through the guide apparatus of the turbine, provided with a guide blade goes to the blade apparatus of the impeller by the invention of the structure. In blade apparatus thread interscapular space is formed under the influence of rotating blades with optimum spatial profile of the work zone input 4 and output 5 edges, and the surface of each pen blades 3. During the rotation of the impeller, the slope of the input edges 4 of each of the blades 3 provides increased speed of the input stream in the middle part of the height of the zone pen blades 3 for the inlet edges of the blades and the lowering of the flow velocity at the entrance to the impeller at the rim and hub, thus reducing the dynamic pressure drop at the inlet edges of the blades near the bottom of the rim and on the surface of the rim near the input edges and thereby achieve a high efficiency of preventing cavitation at the inlet edges of the blades.

Thus, when the turbine at partial load mode, characterized by low flow rates of the incoming flow, due to the increase of its speed in certain areas and pen blades 3, gidrodinamicheskie parameters flow inlet edges of the blades in the area of medium-height part of the surface of the pen blades, made with defined in accordance with the invention, the spatial profile parameters close to the parameters of the incoming flow stream with a flow rate corresponding to the operation of the turbine at the optimum and/or maximum mode the load of the turbine. Zone surface pen blades 3, located in the middle section of the blade to a greater extent than areas in the section immediately adjacent to the hub 2, determine the value developed by the turbine efficiency and hydrodynamic stability of flow of the working fluid in the flow area of the turbine. Therefore, when the turbine at partial load profile pen blades made according to the present invention, provides increased efficiency up to 1% compared with the value of efficiency is reached when the water turbine type Francis with currently known designs of blades.

Made in accordance with the invention the profile of the input edge 4 of the blade 3 in the area from point m to the point of attaching the blades to the rim of the impeller can significantly reduce the speed of the rolling surface of the blade flow of the working fluid. The pressure of the flow in the zone of suction pen blades 3, which is formed in the vicinity of the input edge, increases to such an extent that when et is m totally excluded reasons usually causing cavitation process. The latter also provided the opportunity for increasing the value of the efficiency of the turbine during operation, optimum and/or maximum possible load.

The exception cavitation, respectively, leads to the exclusion of the probability of erosive wear on input 4 and output 5 edges and directly adjacent areas of the surface of each pen blades, guide vanes of the turbine, but also greatly extends the range of loads, characterized by reliable operation of the turbine and substantially reduce the amount of operating costs while extending turnaround and service life of blades.

1. Blade apparatus of the impeller radial-axial turbines, containing rim, hub, blades, directly connected with the rim and the hub, each of which has input and output edges of a curved profile, the working parts are made with certain deviations in relation to the connection points of the input and output edges of each blade to the hub and the rim, characterized in that the portion of the input edges of each blade from the point of attaching the blades to the hub to a point M located on the entrance edge to the maximum distance from a plane parallel to the axis of rotation of the wheel prohodjashei through the connecting points of the input edges of the blades to the rim and the hub, made with a slope along from the hub to the rim against the direction of rotation so that the connection point of the input edges of each blade to the hub is located in front of the direction of rotation of the impeller with respect to the point M and the point of connection of the input edges of each blade to the rim is behind in the direction of rotation of the impeller and connection points of the input edges of the blades to the hub or lying down with her on the same radial plane, and the portion of the input edge of each blade is located between the point M and the point of connection of the input edge to the rim, made with a slope from the hub to the rim in the course in the direction of rotation of the impeller so that the connection point of the input edges of the blades to the rim is located ahead of the point M and the point of connection of a trailing edge of the blades to the rim is located in the direction of rotation of the impeller front attachment point off the edge to the hub or lying down with her in the same radial plane, and the profile of the work area of a trailing edge formed in such a way that the point K is located on the output edge, it has the maximum distance in the direction against the rotation of the plane passing through the connecting points of the trailing edge to the hub and the rim and parallel to the axis of rotation of the wheel.

2. Blade apparatus of the impeller pop, characterized in that the spatial position of the point M is determined by the distance Hmbetween the connection point of the input edge of the blade to the rim of the impeller to the point M and the value of Nm10%-40% of the value of the size of the input edges of the blade Hithe spatial position of the point K is defined by the distance Htobetween the connection point of a trailing edge of the blades to the rim of the impeller to the point K, and the value of Ntois 10-40% of the size of a trailing edge of the blades Hand.

3. Blade apparatus of the impeller according to claim 1 or 2, characterized in that the spatial position of the point M on the input edge of each blade is characterized by the angle ϕmformed by a radial plane passing through the point M on the input edge of each blade and a radial plane passing through the point of connection of the input edges of each blade to the hub, and defined by the formula

ϕm=(5°-20°)·b0/D1,

and the spatial position of the point K on the output edge of each blade is characterized by the angle ϕtoformed by a radial plane passing through the point K on the output edge of each blade, and a radial plane passing through the point of connection of a trailing edge of each is opasti to the hub, and defined by the formula

ϕto=(5°-20°)·b0/D1,

where b0- the height of the guide vanes of the turbine; D1the magnitude of the diameter on which are the connection points of the input edges of each of the blades of the impeller to the rim.



 

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