JPS60153478A - Runner vane for propeller turbine - Google Patents

Abstract

PURPOSE:To improve the cavitation characteristic at the outlet of outercircumference of runner vane by providing a recess for suppressing leakage of water from high to low pressure face side along the vane profile in the outercircumferential end face of runner vane. CONSTITUTION:An elongated recess 12 is made longitudinally in the outercircumferential face of runner vane 11 while predetermined gap is maintained between the outercircumferential face of runner vane and discharge ring 3. The leak flow S flowing along the high pressure face side 11a of runner vane will drop the pressure through increase of flow path resistance caused by the recess 12 made in the outercircumferential end face of runner vane to suppress leakage to the low pressure face side 11b. Consequently, the turbine efficiency is improved to suppress cavitation at the outlet of outercircumference of runner vane.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a runner blade for a propeller water turbine formed by a plate-shaped body having an airfoil cross section. This is designed to suppress the leakage of running water.

[Prior art and its problems]

In general, propeller water turbines are high specific speed water turbines that are applied to low heads of about 90 m or less, and there are two types: vertical shaft structures and horizontal shaft structures. For those with a vertical shaft structure, a spiral casing similar to a 7 Rancis turbine is used for a head of about 20 m or more, and a semi-spiral casing is often used for a head of about 20 m or less. The horizontal shaft structure is applied to low heads of about 20 m or less, uses a cylindrical casing, and is generally called a tubular water turbine. In this horizontal shaft structure, the generator is also generally provided within the casing.

The launch is provided with 4 to 10 runner blades and no runner band. Launch vanes are often of a movable structure, and the opening degree of the guide vanes and runner vanes can be changed in response to changes in load and head. In this case, the interrelationship of the opening degrees is kept constant by the cam l provided in the speed governor so that the water turbine can always operate at the best efficiency.

In many cases, the runner blades are opened and closed automatically using pressure oil, similar to the guide blades. This type of self-adjusting movable blade propeller water turbine is also called a Kabran water turbine.

In a propeller-turbine with such a structure, cavitation occurs near the outlet of the outer periphery of the runner blades, reducing the efficiency of the turbine or causing abnormal damage to the runner blades or discharge ring. It is desired to reduce this.

FIG. 1 shows a conventional example of the main part of the runner blades of a propeller water turbine with a horizontal shaft structure. It is supported by the runner boss 2 and has a structure that allows the opening degree to be changed. Reference numeral 3 denotes a discharge ring, which is a part of the above-mentioned cylindrical casing and serves as an outer circumference of the runner blade 1 connected to the upstream side of the suction pipe (not shown). Water flows as indicated by arrow A, runner 10 rotates as indicated by arrow B, and a constant gap δ is maintained between the outer circumferential surface of runner blade 1 and the inner circumferential surface of discharge ring 3. ! Fig. 2 is an enlarged cross-sectional view taken along line B-B in Fig. 1. During operation of the water turbine, water flowing from the high-pressure side 1a of the runner blade leaks to the low-pressure side 1b through the gap δ as shown by arrow P. In addition to reducing the efficiency of the water turbine, cavitation occurs near the outlet of the outer circumference of the launch blade 1, resulting in abnormal damage to the inner circumferential surface of the runner blade 1 or discharge ring 3.

[Purpose of the invention]

In view of the above points, the present invention has a simple structure that suppresses leakage of flowing water from the high pressure side to the low pressure side of the launch blade, increases the efficiency of the water turbine, and improves the cavitation characteristics at the outlet of the outer peripheral part of the runner blade. The purpose of the present invention is to provide a runner blade for a propeller water turbine that can

[Key points of the invention]

According to the present invention, the above object is achieved by providing a runner blade of a propeller water turbine formed as a plate-like body with an airfoil cross section with a recess along the airfoil shape on the outer peripheral end face of the launch blade.

[Embodiments of the invention]

The present invention will be described below based on drawings showing embodiments. 3 and 4 show an embodiment of the present invention, FIG. 3 is a plan view of the launch blade, and FIG. 4 is a cross-sectional view taken along line C-C. Components that are the same as those in the figures are given the same reference numerals and their explanations will be omitted. Lunch feathers 1
1 is formed as a plate-like body with an airfoil-shaped cross section, and is provided with an elongated recess 12 in the longitudinal direction of the airfoil on its outer peripheral surface. Also, a constant gap δ is maintained between the outer circumferential surface of the runner blade 11 and the discharge ring 3, and water flows into the inlet end of the runner blade 11 at an appropriate angle, and the water flows as shown by arrow Q along the airfoil shape. forming a flow.

In such a structure, a labyrinth effect occurs between the runner blade 11 and the discharge ring 3, and the leakage flow as shown by the arrow S of the flowing water flowing along the high pressure side 11a of the runner blade is caused by the outer peripheral end surface of the launch blade. The pressure decreases due to the increase in flow path resistance due to the recess 12 provided on the low pressure side 11.
It becomes difficult to leak to b.

This increases the efficiency of the water turbine and suppresses the occurrence of cavitation at the outlet of the outer circumference of the launch blade.

In the above-mentioned embodiment, the runner blade 11 has one elongated recess 12 in the longitudinal direction of the airfoil shape on the outer circumferential end surface of the runner blade 11, but in addition, the runner blade 5- is a plate-shaped runner blade with a large blade span. A plurality of elongated recesses 12 may be provided in parallel to the blade span, and in this case, the leakage flow of flowing water from the high pressure side to the low pressure side of the launch vane can be further reduced. .

〔Effect of the invention〕

As described above, the present invention provides a launch vane for a propeller water turbine which is formed as a plate-like body with an airfoil cross section, by providing an elongated recess in the longitudinal direction of the airfoil on the outer peripheral end surface of the runner blade. This structure suppresses leakage of flowing water from the high-pressure side of the launch blade to the low-pressure side, increases turbine efficiency, and improves cavitation characteristics at the outlet of the outer circumference of the launch blade.
Damage to the launch blade or discharge ring can be prevented.

[Brief explanation of the drawing]

Figures 1 and 2 show a conventional example of the main part of the runner blade of a horizontal propeller water turbine. Figure 1 is its configuration, Figure 2 is a sectional view taken along line B-B in Figure 1, and Figure 3 4 shows an embodiment of the present invention, FIG. 3 is a plan view of the main part of the runner blade, and FIG. 4 is a sectional view taken along the line C--C. 11 Runner blade, lla...high pressure side, 12b...
Low pressure side, 12... recess.

Claims (1)

[Claims] 1) In a runner blade of a propeller water turbine formed as a plate-shaped body having a wing-shaped cross section, a recess is provided on the outer peripheral end face of the runner blade to suppress leakage of flowing water from the high-pressure side to the low-pressure side of the launch blade. A launch blade of a propeller water turbine, characterized in that: a launch blade of a propeller water wheel is formed along the airfoil shape.