JP4764244B2 - Bending suction pipe of hydraulic machine - Google Patents

Description

  The present invention relates to a bent suction pipe of a hydraulic machine.

  The bent suction pipe of the hydropower machine guides the running water from the runner vane outlet to the discharge channel, effectively uses the potential energy of the running water at the runner vane outlet, and at the same time rectifies while gradually expanding the running channel to reduce the flow velocity. Thus, it has a function of efficiently converting the velocity energy at the runner vane outlet to pressure energy.

  FIG. 9 is a conceptual diagram of a bent suction pipe of a general Francis type turbine. As shown in FIG. 9, the flowing water from the runner vane 11 passes through the upper draft 12 and the bent section inlet cross section 13, and after changing the flow direction by the bent section 14, the flowing water is decelerated by the enlarged section 15 to recover the pressure. Plan. The enlarged portion 15 is formed so that the cross-sectional area increases in the horizontal direction from the lowest point 16 in the suction pipe flow path toward the hydraulic machine center line X side toward the downstream side at a swing angle γ. Hereinafter, a cross section obtained by cutting a part having a suction pipe along a plane perpendicular to the direction of the axis (center line S) of the pipe line is referred to as a “cross section” at the part. In FIG. 9, Y is the rotation axis of the watermill machine, and F is the suction pipe depth.

  When the flow passage cross-sectional area of the enlarged portion 15 is wide, a center pier that separates the flow from the vicinity of the enlarged portion 15 is provided to effectively cancel the swirl direction component of the flow flowing from the runner vane and prevent a sudden increase in the cross-sectional area. By adding a flow rectifying effect, the pressure may be efficiently recovered.

  The cross-sectional area of the vertical section in a predetermined range upstream from the boundary with at least the bent portion of the upper portion of the suction pipe increases as the distance from the runner vane outlet increases, and the vertical section in the predetermined range The vertical width of the width is constant, the horizontal width of the vertical cross section at the bent portion is larger than the vertical width, the loss at the bent portion is reduced, and the amount of civil engineering excavation is reduced ( For example, see Patent Document 1).

Usually, since the suction pipe is buried, it is necessary to excavate the ground according to the shape of the suction pipe. In the bent suction pipe of the hydraulic machine having the angle γ where the enlarged portion 15 is swung up to the hydraulic machine center line X side, the amount of civil engineering excavation is small. Moreover, the amount of civil engineering excavation may be reduced by designing the suction pipe depth F shallow. There is one in which the working space between the suction pipe liner and the foundation concrete floor and the amount of excavation are reduced, and the construction cost is kept low in combination with the shortening of the construction period (for example, see Patent Document 2).
JP 2001-140741 A JP 2002-168171 A

  However, a bent suction pipe of a hydraulic machine is often designed to have a deep suction pipe depth for the purpose of high performance. In this case, the amount of civil engineering excavation increases. If the suction pipe depth is designed to be shallow, the pressure recovery by the suction pipe cannot be efficiently achieved, and the performance of the suction pipe deteriorates.

  FIG. 10 is a schematic view of the flow mechanism in the suction pipe. As shown in FIG. 10, when the suction pipe depth is reduced, the flow direction 17 of water indicated by an arrow changes abruptly in the vicinity of the bent portion outlet, so that the flow separation 18 occurs near the upper surface of the bent portion outlet and the upper surface of the enlarged portion. Will occur. As a result, the velocity energy at the outlet of the runner vane cannot be efficiently recovered, resulting in a deterioration in the performance of the suction pipe. This adverse effect significantly reduces performance during overload operation with a high flow rate compared to partial load operation with a low flow rate.

  An object of the present invention is to solve the above-described problems, and is to provide a bent suction pipe of a hydraulic machine that can suppress performance degradation even during overload operation of the hydraulic machine.

A bent suction pipe of a hydraulic machine according to the present invention connects a runner vane of a hydraulic machine that converts the positional energy of running water to rotational energy and a downstream discharge channel, and is connected to the outlet of the runner vane. In a bent suction pipe of a water turbine machine having an enlarged portion whose cross-sectional area increases toward the downstream side in the connecting horizontal direction, the suction pipe flow closest to the rotating shaft of the hydraulic machine is the lowest point inside the bent portion of the suction pipe Le is the distance from the rotation axis of the hydraulic machine to the lowest point in the suction pipe flow path closest to the rotation axis, which is present on the enlarged portion side of the cross section including the lowest point in the road, and the rotation axis of the hydraulic machine When the distance to the lowest point on the inside of the bent portion of the suction pipe is Lemin, 0.10 <(Lemin−Le) /Le≦0.85 .

According to the present invention, the lowest point on the inside of the suction pipe bent portion is on the enlarged portion side of the cross section including the lowest point in the suction pipe flow path closest to the rotation axis of the hydraulic machine . The curvature further extends in the direction of the enlarged portion. Therefore, it is possible to suppress the separation of the flow that is likely to occur on the upper surface of the suction pipe, and it is possible to suppress the performance degradation during the overload operation.

(First embodiment)
FIG. 1 is a conceptual diagram of a bent suction pipe of a hydraulic machine according to a first embodiment of the present invention. In FIG. 1, illustration of a hydraulic turbine and a pump turbine that are hydraulic machines is omitted. The side surface of the upper draft 12 is formed so as to increase as the distance from the runner vane outlet increases. The enlarged portion 15 is formed such that the lowest point 16 in the suction pipe flow path is flat in the horizontal direction. That is, of the lowest point 16 in the suction pipe flow path, the point 16a and later (downstream side) closest to the rotation axis Y of the hydraulic machine is flat in the horizontal direction.

  On the other hand, inside the bent portion of the suction pipe, it is expanded downstream with a predetermined swing angle toward the hydraulic machine center line X side. The lowermost point 19 on the inner side of the bent portion of the suction pipe is formed to be closer to the enlarged portion 15 than the cross section including the lowest point 16a in the suction pipe flow path closest to the rotation axis of the hydraulic machine.

  Now, let Le be the distance from the hydraulic machine rotation axis Y to the lowest point 16a in the suction pipe flow path, and Lemin be the distance from the hydraulic machine rotation axis Y to the lowest point 19 inside the bent part of the suction pipe. When the relationship of (Lemin−Le) / Le is shown, the characteristics shown in FIG. 2 are obtained.

  As shown in FIG. 2, it is understood that the loss of the bent suction pipe of the hydraulic machine is small when (Lemin−Le) / Le is in the range of 0.10 to 0.85. Therefore, the position of the lowest point 19 on the inner side of the bent portion of the suction pipe is determined so that 0.10 <(Lemin−Le) /Le≦0.85.

  According to the first embodiment, the lowest point 19 on the inside of the bent portion of the suction pipe is defined on the enlarged portion 15 side with respect to the lowest point 16a in the suction pipe flow path, so that the curvature inside the bent portion is further increased. The structure extends in the direction of 15. Therefore, it is possible to suppress the separation of the flow that is likely to occur on the upper surface of the suction pipe and to suppress the performance degradation during the overload operation.

(Second Embodiment)
FIG. 3 is a conceptual diagram of a bent suction pipe of a hydraulic machine according to the second embodiment of the present invention. In FIG. 3, illustration of a hydraulic turbine and a pump turbine that are hydraulic machines is omitted. This second embodiment has a straight portion 20 defined by an extension line on the side surface of the upper draft portion with respect to the shape inside the bent portion, compared to the first embodiment shown in FIG. .

  In FIG. 3, the side surface of the upper draft 12 is formed so as to increase as the distance from the runner vane outlet increases, and the enlarged portion 15 is formed so that the lowest point 16 in the suction pipe flow path becomes flat in the horizontal direction. Is formed. Further, inside the bent portion of the suction pipe, the suction pipe is expanded downstream at a predetermined swing angle toward the hydraulic machine center line X side, and the lowest point 19 inside the bent portion of the suction pipe is the suction pipe closest to the rotating shaft of the hydraulic machine It is formed so as to exist closer to the enlarged portion 15 than the cross section including the lowest point 16a in the flow path.

  For such a shape inside the bent portion, when taking a coordinate system in which the cross section including the point closest to the hydraulic machine rotation axis among the lowest points in the suction pipe flow path is taken as 90 degrees, along the cross section of the suction pipe bent portion The bent portion has a straight portion 20 defined by an extension line on the side surface of the upper draft portion up to a cross section of 40 degrees or more and 50 degrees or less. This is because the flowing water flowing through the bent portion recovers pressure by gradually expanding the cross-sectional area with respect to the flow direction, but the flow direction changes due to bending of the flow path, and loss occurs. This is to reduce the above.

  FIG. 4 is a characteristic diagram of the loss of the bent suction pipe of the hydraulic machine in a straight line shape from the 0 degree position of the bent portion to the lowest point 19 inside the bent portion of the suction pipe. As shown in FIG. 4, it can be understood that peeling at this portion can be suppressed and loss can be reduced by making the inside of the bent portion into a linear shape within a range from the 40 ° position to the 50 ° position or less of the bent portion. In addition, the suction pipe shape having a straight portion up to a position of 50 ° or more in the bent portion has an excessively large curvature on the inner side of the bent portion, so that flow separation tends to occur after the straight portion.

  On the other hand, in each part of the suction pipe, the angle formed by the bent portion inner straight portion 20 from the bent portion inlet cross section 13 and the vertical line of the hydraulic machine center line X is α, in the direction of the axis (center line S) of the pipe line. Of the suction pipe center line S obtained by connecting the center of gravity of the cross section obtained by cutting along a vertical plane, the curved portion inlet cross section 13 and the straight line connecting the curved portion inlet cross section 13 to the cross section at a 5 degree position are hydraulic machines. When the angle of the perpendicular of the center line is β, the suction pipe shape is defined as α> β. As a result, the flow direction of the outer peripheral side as well as the inner peripheral side of the bent portion is gently changed. Therefore, it is possible to reduce the collision loss on the outer periphery side of the bent portion, and it is possible to suppress the decrease in hydraulic performance during overload operation.

  According to the second embodiment, since the predetermined range inside the bent portion is linear and suppresses separation to reduce loss, it is possible to suppress flow separation during overload operation. It becomes possible to suppress the performance degradation during the overload operation of the bent suction pipe. By gently changing the flow direction on the outer peripheral side as well as the inner peripheral side of the bent part, collision loss on the outer peripheral side of the bent part can be reduced, and the deterioration of hydraulic performance during overload operation is suppressed. be able to.

(Third embodiment)
FIG. 5 is a conceptual diagram of a bent suction pipe of a hydraulic machine according to the third embodiment of the present invention. In FIG. 5, illustrations of a hydraulic turbine and a pump turbine that are hydraulic machines are omitted. In the third embodiment, the curvature ρi inside the bent portion, the curvature ρo outside the bent portion, and the channel height He of the cross section of the bent portion are predetermined with respect to the first embodiment or the second embodiment. The collision loss on the outer peripheral side of the bent portion is reduced by gently changing the flow direction on the outer peripheral side.

  In FIG. 5, the curvature inside the bent portion is ρi, the curvature outside the bent portion is ρo, and the flow path height of the cross section of the bent portion is He. FIG. 6 is a characteristic diagram showing the relationship between the loss of the bent suction pipe of the hydraulic machine and (1 / ρi + He) / (1 / ρo). As can be seen from FIG. 6, the loss of the bent suction pipe of the hydraulic machine is small in the range of 1.5 / 2.4 of (1 / ρi + He) / (1 / ρo). Further, when the value exceeds this range, the smaller the value, the larger the collision loss, and the larger value, the worse the pressure recovery rate, so the loss is large in either case.

  Accordingly, the shape of the bent portion of the suction pipe is determined so that 1.5 ≦ (1 / ρi + He) / (1 / ρo) ≦ 2.4 holds. Accordingly, the inner shape of the bent portion is a shape that is biased toward the outer periphery in each cross section after the straight portion.

  According to the third embodiment, since the direction of flow on the outer peripheral side is gradually changed, collision loss on the outer peripheral side of the bent portion can be reduced. Therefore, it is possible to suppress a decrease in hydraulic performance during overload operation.

(Fourth embodiment)
FIG. 7 is a conceptual diagram of a bent suction pipe of a hydraulic machine according to the fourth embodiment of the present invention. In the fourth embodiment, the flow path height Heo of the suction pipe at the 90-degree position of the bent portion 14 is within a predetermined range as compared with any of the first to third embodiments. It is defined as follows.

  Assuming that the suction pipe depth is F and the height of the suction pipe at the 90 ° position of the bend (the point 16a closest to the hydraulic mechanical rotation axis among the lowest points in the suction pipe flow path) is Heo / The flow path height Heo of the suction pipe is determined so that F falls within a predetermined range.

  FIG. 8 is a characteristic diagram showing the relationship between the loss of the bent suction pipe of the hydraulic machine and Heo / F. As can be seen from FIG. 8, the loss of the bent suction pipe of the hydraulic machine is small in the range of Heo / F 0.2 to 0.3.

  According to the fourth embodiment, the flow path height Heo of the suction pipe at the position 16a (90 degrees of the bent portion) closest to the hydraulic machine rotation axis among the lowest points in the suction pipe flow path is set within a predetermined range. Therefore, the loss of the bent suction pipe of the hydraulic machine can be reduced.

The conceptual diagram of the bending | suction suction pipe of the hydraulic machine concerning the 1st Embodiment of this invention. The characteristic view of the loss of the bent suction pipe in the first embodiment of the present invention. The conceptual diagram of the bending | suction suction pipe of the hydraulic machine concerning the 2nd Embodiment of this invention. The characteristic figure of the loss of the bending | suction suction pipe in the 2nd Embodiment of this invention. The conceptual diagram of the bending | suction suction pipe | tube of the hydraulic machine concerning the 3rd Embodiment of this invention. The characteristic figure of the loss of the bending | suction suction pipe in the 3rd Embodiment of this invention. The conceptual diagram of the bending | suction suction pipe of the hydraulic machine concerning the 4th Embodiment of this invention. The characteristic view of the loss of the bent suction pipe in the fourth embodiment of the present invention. Conceptual diagram of bent pipe of Francis turbine Schematic diagram of the flow mechanism in the suction pipe

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Lanna vane, 12 ... Upper draft, 13 ... Bending part inlet cross section, 14 ... Bending part, 15 ... Enlarged part, 16 ... Bottom point in suction pipe flow path, 17 ... Flow direction, 18 ... Flow separation, 19 ... Suction pipe bent part inside lowest point, 20 ... straight line part

Claims (3)

A bent section connected to the runner vane outlet connecting the runner vane of the hydraulic machine that converts the potential energy of running water into rotational energy and the downstream discharge channel, and a cross-sectional area that is connected to the bent section and that is connected to the bent section and that faces horizontally and faces downstream. In a bent suction pipe of a water turbine machine having an enlarged part with increasing
The lowest point on the inside of the bent portion of the suction pipe is present on the enlarged portion side from the cross section including the lowest point in the suction pipe flow path closest to the rotation axis of the hydraulic machine,
The distance from the rotation axis of the hydraulic machine to the lowest point in the suction pipe flow path closest to the rotation axis is Le, and the distance from the rotation axis of the hydraulic machine to the lowest point inside the suction pipe bent portion is Lemin. A bent suction pipe of a hydraulic machine, characterized in that 0.10 <(Lemin−Le) /Le≦0.85 . When the curvature inside the bent portion is ρi, the curvature outside the bent portion is ρo, and the flow path height of the cross section of the bent portion is He, 1.5 ≦ (1 / ρi + He) / (1 / ρo) ≦ 2.4. draft tube bending hydraulic machine according to claim 1, characterized in that. When the suction pipe depth is F, and the suction pipe flow path height at the cross-sectional position including the point closest to the rotation axis of the hydraulic machine among the lowest points in the suction pipe flow path is 0.2 ≦ Heo / The bent suction pipe for a hydraulic machine according to claim 1, wherein F ≦ 0.3 .

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