Blade system of impeller of radial axial hydraulic turbine

FIELD: engines and pumps.

SUBSTANCE: blade system of impeller of radial axial hydraulic turbine includes rim 1, hub 2 and blades 3, each of which is connected to rim 1 and hub 2 and provided with inlet and outlet edges 4 and 5 of bent shape and smoothly changing thickness in the direction from inlet edge to outlet edge and from hub 2 to rim 1. Blades 3 of blade system have thickened part near inlet edge 4. Maximum thickness of blade 3 in its section with hub 2 is more than maximum thickness of blade 3 in its section with rim 1. Optimum intervals of values of parameters are determined: maximum thickness of section of blade 3 with hub 2, maximum thickness of section of blade 3 with rim 1, as well as their location places along straightened middle line of the appropriate section.

EFFECT: preventing flow separation after inlet edges of blades at operation of hydraulic turbine in modes with increased heads and modes with partial loads in the whole range of working heads.

10 dwg

 

The invention relates to the field of hydrocarbonate and can be used in the design of impellers radial-axial turbines to ensure stable and reliable operation at elevated pressures and at partial load throughout the range of operating pressures.

It is known that for these modes turbines characterized by large values of the hydrodynamic angle of attack, causing separation of the flow at the inlet edges of the blades. Conducted by the applicant on lab benches model tests of impellers radial-axial turbines, as well as three-dimensional numerical flow modeling revealed that separation of flow at the inlet edges of the blades takes the form of a vortex, which occurs on the low-pressure side of the blade in close proximity to the input edges in adjunction to the hub of the impeller and develops megapastor channel from the hub to the rim towards the outer edge. Also, these studies showed that the flow area of the blade adjacent to the rim, occurs without interruption of the stream for input edge. Thus, the low-pressure side of the blades near the output edges of the dissipation takes place (scattering) of vortices and collapse ("collapse") contained steam p is the frequency. Due to the above-described process is the loss of energy of a moving fluid stream, there are high-frequency pressure pulsations in the flow and cavitation erosion on the low-pressure side of the blade near the trailing edge. As a result, when the turbine at elevated pressures and at partial loads are sharp decrease in efficiency of the turbine, the instability of the flow and a more intensive process of cavitation erosion of the blades of the impeller.

Optimization of the surface profile of the blade is one of the key tasks in the development of guide vanes of the impeller, as the geometric characteristics of the profile of the blade thickness distribution in the direction from the input edge to an output, the value of the maximum thickness and its location) have a significant impact on energoeffektivnye features working wheels.

In hydrocarbonate known that the thickening of the blade while maintaining constant all other parameters entails increasing flow velocities, flow over the blade, which, in turn, leads to reduction of pressure on the concave and convex sides of the profile, and consequently, to reduce energoeffektivnyh characteristics of the impeller. Usually to achieve a higher energoeffektivnyh indicators is she the thickness of the cross section of the blade choose the lowest possible based on the conditions of providing the necessary structural strength.

The value cavitation factor can be changed also by moving the position of the point of maximum thickness of the cross section along the median line of the cross section of the blade (at the same value of the maximum thickness of the section).

Under the middle line of the cross section of the blade refers to the section line, equidistant from the working surface and the back surface of the blade.

It is known that the displacement of the point of maximum thickness to the output edge causes thickening of the cross-section of the blade in the zone of maximum discharge and leads to a decrease energoeffektivnyh characteristics. On the other hand, moving the point of maximum thickness of the cross section to the input edge always can significantly improve the cavitation quality, but in this case, there are certain design limitations.

It should also be noted that known airfoils with strongly thickened head part along the entire height of the blade used in the design of aircraft and can withstand a large range of angles of attack, flow, up to 40 degrees, without separation of the boundary layer. However, the experience of the design and operation of hydraulic turbines shows that hydrocarbonate the use of this type of profile is impractical for two reasons. Strong thickening of the head part of the profile around the unwinding diameter is at the blades from the hub to the rim leads to increased hydraulic energy losses and reduce the efficiency of the turbine at high relative velocities of flow at the entrance to the impeller, and also to the deterioration of the cavitation characteristics of the turbines on most operating modes. In addition, the solutions applied in aerodynamics, is not applicable in hydrocarbonate due to the different nature of the flow separation on the flight aerodynamic profile of the aircraft and on the blades of the radial-axial turbines: on the aerodynamic profile of the wing flow separation is characterized by the occurrence periodically separated from the input edge vortices, the axis of which is parallel to the input edge of the wing and which extend across the width (span) of the wing, and on the blades of the guide vanes of the impeller radial-axial turbines the main part of the stable vortex rotates, the axis it quickly deviates from the position parallel to the input edge, and approaches a position parallel to the line of intersection blades with the rim, while the unstable state of the vortex occurs in the tail part of the output stream from megapastor channel.

The traditional design of guide vanes of the impeller used in the radial-axial turbines, includes a hub, rim, rotor blades, each of which is executed with the input and output edges, and the body of the blade, enclosed between the hub, the rim, the input and output edges, has a variable thickness. Thus, according to the recommendation of who, based on the results of research of influence of parameters, including the geometry of the profiles of the blades, the hydrodynamic performance of the impeller, the cross sectional profile of the blade relative to the flattened median line of the cross section is convex, and the location of the point of maximum thickness of the profile cross-section is taken at a distance from the input edge (25÷35)% of the length of midline section [Awhustowski, Austalian. Theory and hydrodynamic calculation of the turbines. L.: engineering, 1974, s-357].

It should be noted that consideration of the thickness distribution of the cross section flattened along midline gives a better view of the shape of the profile section. Therefore, the applicant uses the concept of a flattened midline section of the blade and then discusses the profile of the blade relative to the flattened median line.

The above-described conventional implementation guide vanes is by far the most common in hydrocarbonate.

As the closest to the claimed technical solution is proposed to choose the blade apparatus of the impeller radial-axial turbines aimed at improving the efficiency and improve the cavitation erosion and pulsation characteristics at partial loads [the author is the certificate of the USSR No. SU 1659679, F03B 3/12 published 30.06.1991,]. Blade apparatus of the impeller includes an upper rim, which is the Central part (hub) of the impeller, and the lower rim (rim), and fastened between the blades. According to the ratios of the geometric parameters, in accordance with which made the surface of each blade, the input and output edges of each blade are curved profile and a variable thickness, gradually changing in the direction from the input edge to an output edge and from the hub to the rim. Analysis of the geometrical parameters of the surface of the blade shows that in this case is the traditional solution, in which the cross sectional profile of the blade relative to the flattened median line section is made convex, the thickness of the section from the input edges increases, reaching a maximum value, then decreases to the trailing edge, and the point of maximum thickness of the cross section of the blade is from the input edges within (25÷35)% of the length of the median line of the section, and the maximum thickness of the blade does not practically change the height of the blade from the hub to the rim.

The application of the above technical solutions in the development of impellers radial-axial turbines is not possible when operating at elevated pressures, and n is the partial load throughout the range of operating pressures to avoid separation of the flow at the inlet edges of the blades, guide vanes of the impeller and the formation of vortices in megapath channels, therefore these modes is increased hydraulic losses in the flow, there is a more intensive process of cavitation erosion of the blades and the emergence of high-frequency pressure pulsations in the flow.

The technical result, which directed the claimed technical solution is to prevent separation of the flow at the inlet edges of the blades when the turbine operates at an elevated pressure, and the partial load throughout the range of operating pressures, which allows to reduce hydraulic losses while reducing the instability of the flow and the reduction of cavitation erosion on the blades of the impeller.

To achieve the technical result serves blade apparatus of the impeller radial-axial turbines, containing rim, hub and blades, each of which is connected with the rim and the hub and is made with the input and output edges curved profile, and the thickness of the blades continuously varies in the direction from the input edge to an output and in the direction from the hub to the rim.

Thus, according to the invention, the profile of the blade surface of the hub relative to the flattened midline cross-section has a convex section, starting from the input edges, the thickness of which is wow first increase and then decreases. For the above-mentioned convex portion of the profile section should be concave section. The thickness of the cross section of the blades, the hub surface gradually increases from the input edge and reaches a maximum value at a distance from the input edge component (8÷16)% of the length of the median line of the cross section of the blade surface of the hub, after which the thickness of the cross section gradually decreases to the trailing edge. The maximum thickness of this section is (2,7÷4,5)% of the nominal diameter of the impeller turbines.

The profile of the blade surface of the rim relative to the flattened median line section is made convex. The thickness of the cross section of the blade surface of the rim from the input edge gradually increases and reaches the maximum value at a distance from the input edge component (12÷34)% of the length of the median line of the cross section of the blade surface of the rim. Then the thickness of this section gradually decreases to the trailing edge. The maximum thickness of the cross section of the blade surface of the rim is (1,4÷2,2)% of the nominal diameter of the impeller turbines.

The proposed geometric characteristics of the shape of the paddle blade apparatus and the intervals of values of the parameters identified by the applicant as a result of the research and are optimal to achieve at asanoha above technical result.

Execution of blades blade apparatus with a thicker part near the input edges as described above, allows for modes with elevated pressures and at partial load throughout the range of operating pressures to expand the range of unstressed corners of the leakage flux and thereby avoid separation of the flow on the blades of the impeller and vortex formation in megapath channels, as evidenced by the results of the applicant's model and full-scale tests, and the results of the three-dimensional mathematical modeling of flow. Thus, the proposed solution provides a reduction of cavitation erosion on the blades of the impeller, eliminating high-frequency pressure pulsation flow in the flow part, the increase in value achieved by the turbine efficiency, which ultimately allows to significantly extend the range of loads, characterized by reliable operation of the turbine, and, most importantly, this result is achieved without sacrificing performance of the turbine under different modes of operation.

To achieve the above technical result is applied non-obvious to a person skilled solutions that are not explicitly derived from the prior art, namely, the execution of blades blade apparatus with a thicker part near the entrance to the OMCI, moreover, the maximum thickness of the blade root section (the cross section of the blades, the hub surface) is greater than the maximum thickness of the blade section of the surface of the rim.

While the applicant was shown above, the optimal values of the intervals of the following parameters: the maximum thickness of the cross section of the blades, the hub surface, the maximum thickness of the cross section of the blade surface of the rim, as well as their placement flattened along midline corresponding section.

Conducted model tests and three-dimensional mathematical modeling of flow confirmed that at specified intervals of the parameters at elevated pressures and at partial load throughout the range of operating pressures is provided to prevent separation of the flow at the inlet edges of the blades, guide vanes of the impeller and the formation of the vortex in megapath channels.

It should also be noted that in the above mentioned ratios of parameters of the blade design blade apparatus has the necessary strength and reliability, which is also confirmed by the results of calculations performed by the applicant and conducted model and field tests.

The essence of the proposed technical solution is illustrated by drawings.

what a figure 1 presents the Meridian section of the guide vanes of the impeller radial-axial turbines, which shows the rim 1, the hub 2, one of the blades 3 with an inlet 4 and outlet 5 edges.

Figure 2 - profile of the blade guide vanes surface of the hub (the root section of the blade) when flattened median line sections; shows the distribution of the thickness of the root sections of the blades flattened along midline AF.

Figure 3 - profile of the blade surface of the rim with a flattened median line sections; shows the distribution of the thickness of the cross section flattened along midline A F'.

Figure 4 shows the streamlines in megapastor channel on the hub of the guide vanes of the impeller with the traditional distribution of the thickness of the blades when the turbine at partial load mode (at the rate of 75% from the optimal consumption and the occurrence of the vortex behind the entrance edge of the blade.

Figure 5 shows the distribution of the vortex in megapastor channel guide vanes of the impeller with the traditional distribution of the thickness of the blades when the turbine at partial load mode (at the rate of 75% from the optimal consumption).

Figure 6 shows the streamlines in megapastor channel on the rim of guide vanes of the impeller with the traditional distribution of the thickness of the blades when the turbine at partial load mode.

7 - line current in megapastor channel on STU is itzá guide vanes, made according to the claimed technical solution, when the turbine at partial load mode.

On Fig - line current in megapastor channel in the rim of the blade apparatus made according to the claimed technical solution, when the turbine at partial load mode.

Figure 9 presents graphs of efficiency (%) turbine from a given flow Q1' (m3/s) for the model turbine with blade apparatus made according to the claimed technical solution (figure 1), and for the model of the turbine blade with the device executed with the traditional distribution of the thickness of the blade (figure 2). According to the above mode of operation of the turbine at high pressure, amounting to 112 % of the optimal pressure.

Figure 10 - graphs of efficiency (%) turbine from a given flow Q1' (m3/s) for the mode of operation of the turbine under reduced pressure, constituting 80% of the optimum pressure. Figure 1 - model of a turbine blade with a device made according to the claimed technical solution, figure 2 - model of a turbine blade with a device made according to the traditional solution.

Blade apparatus of the impeller radial-axial turbines contains (1) the hub 2 of the impeller, through to the second impeller attached to the shaft of the turbine (Fig. 1 not labeled), blade 3 is fixed on the hub 2 root sections and the rim 1, the connecting ends of the blades. Each blade has an input 4 and output 5 edges.

Given the results obtained when performing calculations and laboratory studies, the applicant was determined approach to shaping the blades of the guide vanes of the impeller, which consists in forming a thickened portion of the blade near the input edge that the maximum thickness of the blade at its root section (i.e. the section of the blades, the hub surface) is greater than the maximum thickness of the blade section of the surface of the rim, the thickness of the blade over the entire length in the direction from the hub to the rim gradually decreases.

The thickness distribution of the cross section of the blade surface of the hub (figure 2) flattened along midline section - segment AF is performed as follows.

The first plot (figure 2 labelled I - from point a to point S1) this section is relatively straight median line is made convex with a smooth increase in the thickness of the cross section from the input edges (from point a) to achieve the maximum thickness of this section Δmax(in point of S1at a distance X from the input edge component (8÷16)% of the length of the median line of the section.

The value of maksimalnaya root section of the blade Δ maxis (2,7÷4,5)% values of the nominal diameter of the impeller turbines.

The following plot (figure 2 marked II - point-S1to the point of S2) is also convex, but in this area the thickness of the cross section gradually decreases gradually, the thickness of the cross section at point S2exceeds the thickness of the trailing edge (point F).

Next, section III (figure 2: point-S2to the trailing edge at the point F) is made concave with gradually decreasing in thickness to the trailing edge.

The thickness distribution of the cross section of the blade surface of the rim (Fig. 3) flattened along midline section of a segment of A F' - is traditional and is implemented as follows.

The profile of the blade surface of the rim relative to the flattened median line from input to output edges (figure 3: from point a' to point F') is made convex.

The thickness of the section at site I' (from point a' to point S1') increases smoothly from the input edge (point a') and reaches the maximum value Δ'maxat point S1' distance X' from the input edge component (12÷34)% of the length of the median line of the considered section. Then, in the area II' (from the point S1' to the point F'), the thickness of the cross section gradually decreases to the trailing edge.

The maximum thickness of the cross section of the blade surface of the rim is'max is (1,4÷2,2)% values of the nominal diameter of the impeller turbines.

The thickness of the blade from the hub to the rim gradually decreases. For example, the blade blade apparatus may be designed so that the maximum thickness of the blade cross sections axisymmetric surfaces of the current D-D (figure 1) linearly decreases from the hub to the rim, i.e. the point of maximum thickness on the median lines of the cross sections of the blades axisymmetric surfaces of the current D-D smoothly, in particular, linearly, are removed from the input edges along the full length of the blade.

All of the above values of the parameter intervals defined by the applicant empirically and are optimal to achieve the technical result, which is confirmed by three-dimensional mathematical modeling of flow and conducted model tests.

Blade apparatus of the impeller radial-axial turbine operates as follows.

The flow of water after passing through the guide apparatus of the turbine is supplied to the blade apparatus of the impeller, where it is further formation under the influence of rotating blades 3 made with optimal spatial profile according to the claimed technical solution.

Incoming flow at the entrance to the impeller which surrounds the inlet edge 4 of each of the blades 3, are made according to the invention that by providing the et distribution of pressure gradients, allow at elevated pressures and partial loads, which are characterized by small costs flowing water and high angles of leakage flow at the inlet edges of the blades, to prevent separation of the flow at the input edges and the formation of the vortex in megapastor channel, to reduce the loss of energy in these modes of operation of the turbine, to improve the cavitation performance and stability of the stream.

By the applicant were conducted model tests two impellers with a diameter of 460 mm, the design of which the middle surface of the blades were made the same. When this blade apparatus for the first model was made according to the claimed technical solution, while for the second model according to the above prototype, with the traditional distribution of the thickness of the cross sections of the blade. Also for these wheels was performed three-dimensional mathematical modeling of the pattern of the flow stream for the same partial load mode when the flow of water 75% from the optimal flow.

The results of calculations and tests allowed us to conduct a comparative analysis of the characteristics of the working wheels.

Obtained on the basis of three-dimensional numerical simulation pattern of the flow stream for partial load operation (at the rate of 75% from the optimal consumption) turbines with blade up what Arat, performed by the present decision or according to the traditional approach, shown in figure 4-8.

Figure 4 and 5 shows the flow for the input flange on the hub of the guide vanes of the impeller with the traditional distribution of the thickness of the blade during operation of the turbine at partial load mode. These figures clearly shows the occurrence of the vortex behind the entrance edge of the blade in the area of contiguity to the hub and distribution of the vortex in megapastor channel impeller (when the turbine at partial load mode and the execution of the blades with the traditional distribution of thickness), and it is clear that traditional blade vortex becomes highly developed.

The distribution of the current lines presented on Fig.6, shows that for input edge portion of the blade adjacent to the rim, there is no separation of flow (when the turbine at partial load mode and the execution of the blades with the traditional distribution of thickness).

Thus, figure 4, 5, 6 show that the partial load operation of the turbine with the blade unit, the blade of which is made with the traditional thickness distribution for the input edges of the blades, a vortex appears and there is separation of the flow, and the vortex occurs in the immediate vicinity of the input edges in adjunction to the hub and developing is carried out in megapastor channel from the hub to the rim towards the outer edge.

Figure 7 presents a picture of the flow in the channels between the blades on the hub of the blade apparatus made according to the claimed solution, when the turbine at partial load mode. On Fig shows the line current in megapastor channel on the rim of blades, also made according to the claimed solution, under partial load of the turbine.

From Fig.7 and 8 it is seen that the blades made according to the proposed technical solution, flow separation and vortex formation on these modes are not available.

A comparison of figures 4-6 and figure 7-8 shows that when the same partial load mode of the claimed technical solution eliminates the vortex formation and serves to prevent separation of the flow at the inlet edges of the blades. This conclusion is confirmed by the results of model and full-scale tests conducted by the applicant.

It should be noted that similar results were obtained for both modes of operation of the turbine with high pressure.

The tests have shown that the performance blade apparatus according to the claimed technical solution allows to improve the characteristics of stability, cavitation erosion, increase the efficiency of the turbine in the flow range from 70% to 120% of the optimum flow rate, the pressure from 110% to 120% of the optimum voltage is RA, it does not reduce the efficiency of the turbine at the optimum pressure and at low pressure, the components of even less than 80% of the optimum pressure.

Comparison of efficiency of two models of impellers with a diameter of 460 mm (Fig.9, 10: schedule 1 - efficiency model of the impeller blade apparatus which is made by the present decision; figure 2 - efficiency model of the impeller blade apparatus which is made with the traditional distribution of the thickness of the blade) when the turbine mode of high pressure, amounting to 112% of the optimal pressure (Fig.9)shows that the partial charges (in the range from 70% to 90% of the optimal consumption) of the inventive solution provides increased efficiency of the turbine by the value from 1.7% to 2.5%, and at low pressure, comprising 80 % of the optimal pressure (figure 10), the application of the proposed technical solution provides increased efficiency at partial costs amount to 0.5%.

Increase efficiency for the considered modes is due to the lower sensitivity to angles of attack of blades blade apparatus made in accordance with the proposed technical solution.

Implementation guide vanes of the impeller radial-axial turbine according to the claimed technical solution allows to avoid the formation of vortices and flow separation at the input edges of the blades, to achieve a minimum level of relevant energy losses in blade apparatus and, thereby, reduce cavitation erosion on the blades of the impeller, the optimal hydrodynamics and stability of current flow in the flow area of the turbine, and a high level of efficiency in a wide range of operating modes of the turbine.

Blade apparatus of the impeller radial-axial turbines, containing rim, hub and blades, each of which is connected with the rim and the hub and is made with the input and output edges curved profile and smoothly varying thickness in the direction from the input to the output edge and in the direction from the hub to the rim, characterized in that the profile of the blade surface of the hub relative to the flattened midline section performed starting from the input edge of the convex section, the thickness of which first increases and then decreases, and the next concave section, the thickness of the cross section of the blade surface of the hub increases smoothly from the input edge, reaching a maximum value at a distance from the input edge component (8÷16)% of the length of the median line of the cross section of the blade surface of the hub, after which the thickness of the cross section of the blade gradually decreases to the trailing edge, and the maximum value of the thickness of the cross section of the blade is again the hub is (2,7÷4,5)% of the nominal diameter of the impeller of the turbine; the profile of the blade surface of the rim relative to the flattened median line section is made convex, the thickness of the cross section of the blade surface of the rim from the input edge gradually increases, reaching a maximum value at a distance from the input edge component (12-34)% of the length of the median line of the cross section of the blade surface of the rim, after which the thickness of the cross section of the blade gradually decreases to the trailing edge, and the maximum value of the thickness of the cross section of the blade surface of the rim is (1,4÷2,2)% of the nominal diameter of the impeller of the turbine.



 

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Unit // 2179260

The invention relates to the field of engineering, namely, hydraulic machines working in turbine mode

The invention relates to hydro - and wind energy, in particular, to devices for energy extraction fluid for converting it, for example, in electricity

Turbine // 2263814

FIELD: mechanical engineering; turbines.

SUBSTANCE: turbine is designed for converting kinetic energy of liquid or gas into mechanical work. Proposed turbine contains cylindrical housing, tangential intake branch pipe arranged over periphery of housing and axial discharge branch pipe arranged in center, and rotor installed on shaft. Rotor is made in form of sup closed at one end. Tangential intake branch pipe is furnished with axial spiral guide member to provide tangential delivery of working medium to cup wall near its open end face. Axial discharge branch pipe is arranged with its inlet hole in cup space. Intake branch pipe is rectangular in section, and discharge branch pipe is round.

EFFECT: simplified design of turbine.

2 cl, 2 dwg

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