JP2007291874A - Axial flow hydro-turbine runner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axial flow hydro-turbine runner capable of reducing leak flow at an outer circumference part of runner blades and reducing collision loss at an inlet of runner blades and secondary flow loss at a pressure surface of the runner blades. <P>SOLUTION: The minimum wall thickness point of the runner blades 13 of the axial flow hydro-turbine runner 11 of which one end is attached on a boss 12 rotating around a center of a spindle and of which another end tip 40 is arranged to oppose to a discharge ring 15 is formed between the tip 14 and the boss 12, and wall thickness of a surface side of the runner blade 13 gradually gets thicker toward both ends of the tip 14 and the boss 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an axial-flow turbine runner having runner blades attached at one end to a boss rotating around a spindle and having the other end opposed to a discharge ring.

  In an axial water turbine such as a Kaplan turbine or a valve turbine, the water flow from the upper pond flows into an axial turbine turbine runner that is a rotating part through a guide vane that adjusts the flow rate. The axial flow turbine runner of this rotating part converts the energy of the water flow into rotational energy, the rotational energy recovered by the axial flow turbine runner gives rotational force to the main shaft, and the generator attached to the main shaft rotates to turn it into electric power. Converted.

  The water flow that passes through the axial water turbine runner flows out to the lower pond through the suction pipe. A narrow gap is provided between the outer peripheral end of the axial-flow water turbine runner of the rotating part and the discharge ring which is a stationary part, and a flow that does not pass between the runner blades is generated from this gap during the water turbine operation.

  Since the flow that does not pass between the runner blades flows without causing rotational energy to the axial flow turbine runner, the efficiency of the turbine is reduced. Moreover, since the flow in this gap part has a high flow velocity, it causes a pressure drop, which also causes cavitation. This cavitation also becomes a factor that limits the operation range of the turbine due to blade erosion, vibration, noise, and the like generated when cavitation collapses.

Therefore, in order to reduce such a leakage flow, there are those in which a fillet is installed at the outer peripheral end of the runner blade (for example, refer to Patent Document 1) and those in which the blade end of the runner blade is rounded (for example, Patent Document 2).
Japanese Utility Model Publication No. 61-76170 JP-A-4-246278

  However, since the water wheel is used in various operating states with different flow rates and heads, the water flow flowing into the runner blades varies greatly depending on the operating state. Cavitation may occur at the water inlet of the runner blade due to an increase in collision loss due to a mismatch between the runner blade angle and the flow angle or a pressure drop near the runner blade surface. Also, when operating on the lower head side than the design head, the flow velocity is relatively slow on the pressure surface side of the runner blades, so the flow is biased toward the outer periphery due to the centrifugal force and does not follow the design streamline. (Secondary flow) increases. Therefore, a loss occurs and the turbine efficiency is reduced.

  15 is a meridional view of a conventional axial water turbine runner, FIG. 16 is a cross-sectional view taken along line AA in FIG. 15, and FIG. 17 is a cross-sectional view taken along line BB and CC in FIG. . The axial water turbine runner 11 is formed by attaching one end of a runner blade 13 to a boss 12 that rotates about a spindle. The other end of the runner blade 13 is disposed as a tip 14 so as to face the discharge ring 15. FIG. 15 shows a case where the left side is the water inlet and the right side is the water outlet.

  As shown in FIG. 16, the fillet 16 is provided on the tip 14 on the back side of the runner blade 13, the runner blade thickness is maximized on the boss 12 side, and gradually toward the tip 14 side. It has a shape that reduces the wall thickness. This is because the runner blades 13 of the axial water turbine runner 11 have a mechanism that rotates around a spindle attached to the boss 12, so that it is necessary to ensure strength on the boss 12 side.

  As described above, the runner blade 13 on the boss 12 side is relatively thicker and gradually becomes thinner toward the tip 14 side. Therefore, as shown in FIG. The tip gradually becomes sharper toward the tip 14 side. Therefore, as shown in FIG. 18, the flow separation W <b> 1 is likely to occur in the water flow at the tip of the water inlet of the runner blade 13. Further, as shown in FIG. 19, the water flow flowing through the runner blades 13 becomes a flow W ′ that is biased toward the outer peripheral side. This is because the thickness of the runner blade 13 gradually decreases as the runner blade 13 moves from the boss 12 side to the tip 14 side.

  An object of the present invention is to provide an axial-flow turbine runner that can reduce the leakage flow at the outer periphery of the runner blade and reduce the collision loss at the inlet of the runner blade and the secondary flow loss at the pressure surface of the runner blade. That is.

  An axial-flow turbine runner according to the present invention is an axial-flow turbine runner having runner blades, one end of which is attached to a boss that rotates about a spindle and the other end of the tip is disposed to face a discharge ring. The minimum thickness point of the runner blade is formed between the tip and the boss, and the thickness on the surface side of the runner blade is gradually increased toward both ends of the tip and the boss.

  According to the present invention, the minimum thickness point of the runner blade is formed between the tip and the boss, and the thickness on the surface side of the runner blade is gradually increased toward both ends of the tip and the boss. Therefore, the leakage flow at the outer peripheral portion of the runner blade can be reduced, and the collision loss at the inlet of the runner blade and the secondary flow loss at the pressure surface of the runner blade can be reduced.

  Embodiments of the present invention will be described below. 1 is a meridional view of an axial-flow turbine runner according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a line taken along lines BB and CC in FIG. FIG. FIG. 1 shows a case where the left side is an inlet for water and the right side is an outlet for water. In the axial water turbine runner 11, one end of a runner blade 13 is attached to a boss 12 that rotates about a spindle. It is formed. The other end of the runner blade 13 is disposed as a tip 14 so as to face the discharge ring 15.

  As shown in FIG. 2, in the runner blade 13 according to the embodiment of the present invention, the minimum thickness position of the runner blade 13 is near the center of the tip 14 and the boss 12, and from the center to the tip 14 and the boss 12, The wall thickness on the surface side of the runner blade 13 gradually increases. A fillet 16 is provided on the tip 14 on the back side of the runner blade 13. Further, as shown in FIG. 3, when the shapes of the BB cross section and the CC cross section are compared, the tip of the runner blade 13 becomes blunt in the BB cross section, that is, the tip 14 side, and the blade at the end of the tip 14 The thickness is increased.

  FIG. 4 is an explanatory diagram of the tip shape on the tip side of the runner blade 13 of the axial flow turbine runner in the embodiment of the present invention. Compared with the flow diagram of the conventional runner blade 13 shown in FIG. 19, the flow W ″ of the water flow flowing through the runner blade 13 is suppressed toward the outer peripheral side. This is because the surface of the runner blade 13 becomes thicker from the vicinity of the center to the tip 14, so that the runner blade 13 becomes concave and difficult to flow from the vicinity of the center to the tip side. As a result, the turbine efficiency can be improved.

  Further, in the axial flow runner according to the embodiment of the present invention, the thickness of the runner blade 13 at the tip end is thicker than the conventional one, so that the clearance between the tip end of the runner blade 13 and the discharge ring 15 is as follows. Although not different from the conventional one, the sealing effect is increased by increasing the facing area, the leakage flow is reduced, and the turbine efficiency can be improved. Furthermore, since the tip shape of the runner blade 13 on the tip side is a blunt shape, the water flow W flowing through the runner blade 13 is less sensitive to changes in the flow angle, as shown in FIG.

  FIG. 6 is a pressure distribution diagram of the runner blade surface according to the embodiment of the present invention. The vertical axis represents the blade surface pressure coefficient Cp, and the horizontal axis represents the blade length L / L0. L is the length from the inlet of the runner blade 13 to a certain point in the outlet direction, and L0 is the total length of the runner blade 13. Further, the curve S is a pressure distribution curve by the runner blade 13 according to the embodiment of the present invention, and S ′ is a pressure distribution curve by the conventional runner blade 13. As shown in FIG. 6, the pressure drop due to the mismatch of the flow angle at the inlet of the runner blade 13 is alleviated. Therefore, the cavitation performance is improved.

  Next, the thickness shape of the runner blades 13 in the embodiment of the present invention will be described. FIG. 7 is an explanatory diagram of how to determine the minimum wall thickness position of the runner blade 13 in the embodiment of the present invention. When the length from the tip 14 of the runner blade 13 to the boss 12 is H0, and the length from the tip 14 to the point where the thickness of the runner blade 13 is minimum is H1, 0.3 ≦ H1 / H0 ≦ 0. A thick shape satisfying 6 is adopted.

  FIG. 8 is a characteristic diagram showing the relationship between the turbine efficiency η / η0 and the minimum wall thickness H / H0 of the runner blade 13 in the same operation state. Note that η is the actual turbine efficiency, and η0 is the turbine efficiency during rated operation. It can be seen that the effect of reducing the loss of the turbine efficiency η / η0 is large when the minimum wall thickness position H1 / H0 is in the range of 0.3 to 0.6.

  When H1 / H0 <0.3, the region for suppressing the secondary flow becomes small and the loss reduction amount is small. In addition, in H1 / H0> 0.6, when the thickness of the runner blade 13 on the tip 14 side is the same, the curvature of the surface of the runner blade 13 from the minimum thickness position of the runner blade 13 to the tip end side is relative. And the secondary flow suppression effect becomes relatively small. Therefore, the minimum point of the blade thickness is provided at a position satisfying 0.3 ≦ H1 / H0 ≦ 0.6. Thereby, it becomes possible to reduce the loss of the turbine efficiency η / η0.

  FIG. 9 is an explanatory diagram of how to determine the minimum wall thickness of the runner blade 13 according to the embodiment of the present invention. The thickness is such that 1.5 ≦ t1 / t0 ≦ 2.0, where t0 is the minimum blade thickness and t1 is the thickness distance of the runner blade 13 excluding the fillet 16 near the tip end. Further, when the tip end thickness including the fillet 16 of the tip 14 is t2, the thickness is set to satisfy 1.5 ≦ t2 / t1 ≦ 3.0.

  If the thickness of the runner blade 13 at the tip end is increased, the secondary flow from the center to the tip 14 side is suppressed and the leakage loss is reduced. However, if the tip end is excessively thick, the tip of the runner blade 13 is increased. The thickness at becomes large. Therefore, the cavitation performance at the inlet of the runner blade 13 is improved, but the collision loss is increased. In addition, the thickness t2 of the fillet 16 at the tip end can sufficiently reduce the leakage loss even in the range of 1.5 ≦ t2 / t1 ≦ 3.0 as the blade thickness in the vicinity of the tip end increases.

  FIG. 10 is a characteristic diagram showing the relationship between the turbine efficiency η / η0 and the wall thickness minimum width ratio t1 / t0 of the runner blade 13 in the same operation state. It can be seen that the effect of reducing the loss of the turbine efficiency η / η0 is great when the minimum thickness ratio t1 / t0 is in the range of 1.5 to 2.0. Therefore, the loss of the turbine efficiency η / η0 can be reduced by selecting the minimum wall thickness of the runner blade 12 so as to satisfy 1.5 ≦ t1 / t0 ≦ 2.0.

  FIG. 11 is an explanatory diagram of how to determine the curvature of the thick shape of the runner blade 13 according to the embodiment of the present invention. The surface shape of the runner blade 13 gradually increases from the minimum thickness portion of the runner blade 13 to the tip end, and the shape is formed by a straight line, a curve, or a combination thereof. Further, when the average radius of curvature is R, and the length of the runner blade 13 from the boss 12 to the tip end is H0, the thickness is set to satisfy R ≦ 2H0.

  FIG. 12 is a characteristic diagram showing the relationship between the turbine efficiency η / η0 and the curvature radius ratio R / H0. It can be seen that when the average radius of curvature R is smaller than 2H0, the effect of reducing the loss of the turbine efficiency η / η0 is great. When the curvature radius R is large, that is, when the curvature radius ratio R / H0 is larger than 2, the effect of reducing the secondary flow loss on the pressure surface of the runner blade is reduced. Therefore, by setting the curvature radius R so as to satisfy R ≦ 2H0, it is possible to reduce the loss of the turbine efficiency η / η0.

  FIG. 13 is an explanatory diagram of how to determine the range to which the thick shape of the runner blades is applied in the embodiment of the present invention. When the length of the runner blade 13 is L0 and the length from the inlet of the runner blade 13 to which the present invention is applied is L1, the range satisfies 0.5 ≦ L1 / L0 ≦ 0.8. That is, it applies only to the inlet side of the runner blade 13.

  FIG. 14 is a characteristic diagram showing the relationship between the turbine efficiency η / η0 and the application range L1 / L0. As shown in FIG. 14, it can be seen that the effect of reducing the loss of the turbine efficiency η / η0 is large when the application range L1 / L0 is 0.5 to 0.8.

  When the application range of the thick shape of the runner blade in the embodiment of the present invention is shortened, the effect of improving the cavitation performance at the inlet of the runner blade 3 is obtained, but the effect of suppressing the secondary flow and the effect of reducing the leakage flow are obtained. Will decrease. On the other hand, when it is applied up to the outlet end of the runner blade 13, the outlet end of the runner blade 13 becomes relatively thick, resulting in a large loss due to the wake. Therefore, the thickness shape of the runner blade in the embodiment of the present invention is applied in the range of 0.5 ≦ L1 / L0 ≦ 0.8. Thereby, it becomes possible to reduce the loss of the turbine efficiency η / η0.

  According to the embodiment of the present invention, the minimum thickness point of the runner blade is formed between the tip and the boss, and the thickness on the surface side of the runner blade is within a predetermined range toward both ends of the tip and the boss. Is formed so that the thickness of the runner blades gradually increases, so that the leakage flow at the outer periphery of the runner blades can be reduced, and the collision loss at the inlet of the runner blades and the secondary flow loss at the pressure surface of the runner blades can be reduced. Efficiency loss can be reduced.

The meridional view of the axial-flow water turbine runner concerning embodiment of this invention. Sectional drawing in the AA of FIG. Sectional drawing in the BB line of FIG. 1, and CC line. Explanatory drawing of the front-end | tip shape at the chip | tip side of the runner blade | wing of the axial flow turbine runner in embodiment of this invention. Explanatory drawing of the front-end | tip shape in the chip | tip side of the runner blade | wing of the axial flow turbine runner concerning embodiment of this invention. The pressure distribution figure of the runner blade surface in embodiment of this invention. Explanatory drawing of how to determine the position with the minimum thickness of the runner blade | wing in embodiment of this invention. The characteristic view which shows the relationship between the turbine efficiency (eta) / (eta) 0 in the same driving | running | working state, and the position H / H0 with the minimum thickness of a runner blade. Explanatory drawing of how to determine the minimum thickness of the runner blade | wing 13 in embodiment of this invention. The characteristic view which shows the relationship between the turbine efficiency (eta) / (eta) 0 in the same driving | running | working state, and the wall thickness minimum width ratio t1 / t0 of the runner blade | wing 13. FIG. Explanatory drawing of how to determine the curvature of the thick shape of the runner blade | wing 13 in embodiment of this invention. The characteristic view which shows the relationship between turbine efficiency (eta) / (eta) 0 and curvature-radius ratio R / H0. Schematic diagram explaining a conventional axial water turbine runner Trajectory diagram of blade surface in conventional axial water turbine runner A meridional view of a conventional axial water turbine runner Sectional drawing in the AA of FIG. Sectional drawing in the BB line of FIG. 15, and CC line. Explanatory drawing of the front-end | tip shape in the chip | tip side of the runner blade | wing of the conventional axial flow water turbine runner. The trace line figure in the blade | wing pressure surface at the time of the water turbine driving | operation of the conventional axial water turbine runner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Axle turbine runner, 12 ... Boss, 13 ... Runner blade, 14 ... Tip, 15 ... Discharge ring, 16 ... Fillet

Claims (8)

  In an axial water turbine runner having a runner blade having one end attached to a boss rotating around the spindle and the other end tip disposed opposite the discharge ring, the minimum thickness point of the runner blade is defined as a tip. An axial-flow turbine runner formed between the boss and formed so that the wall thickness on the surface side of the runner blade gradually increases toward both ends of the tip and the boss.   When the length from the tip of the runner blade to the boss is H0 and the length from the tip to the point where the blade thickness is minimum is H1, 0.3 ≦ H1 / H0 ≦ 0.6. The axial-flow water turbine runner according to claim 1.   2. The condition of 1.5 ≦ t1 / t0 ≦ 2.0, where t0 is the minimum thickness of the runner blade and t1 is the length between the front and back surfaces of the blade near the tip end. The described axial-flow turbine runner.   The length of the front and back surfaces of the runner blade near the tip end of the runner blade is t1, and the length of the tip end fillet is t2, and 1.5 ≦ t2 / t1 ≦ 3.0. The axial-flow turbine runner according to 1.   The axial flow turbine runner according to claim 1, wherein the shape of the blade surface between the portion where the thickness of the runner blade is minimum and the tip is formed by a straight line, a curved line, or a combination thereof.   6. The axial flow turbine runner according to claim 5, wherein R ≦ 2H0, where R is an average radius of curvature of the surface curve of the runner blade and H0 is a length from the boss of the runner blade to the tip end. .   An axial-flow turbine runner characterized in that the shape of any one of claims 1 to 6 is applied to a predetermined range on the inlet side of the runner blade. The predetermined range on the inlet side of the runner blade is 0.5 ≦ L1 / L0 ≦ 0.8 when the length of the runner blade is L0 and the length from the inlet of the runner blade is L1. The axial-flow water turbine runner according to claim 7,

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