CN1080363A

CN1080363A - Utilizing the unnecessary water yield of wet season to increase the water power plant exerts oneself

Info

Publication number: CN1080363A
Application number: CN92104973A
Authority: CN
Inventors: 贾福裕
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-06-20
Filing date: 1992-06-20
Publication date: 1994-01-05

Abstract

The invention belongs to hydraulic power generation technology, be used for the construction of hydropower stations and the technical innovation of existing water power plant, improve the wet season economic benefit.Mainly be to utilize the wet season head low, the advantage that unit operation cavitation safe margin is bigger, utilize the unnecessary water yield, improving flow velocity mends in the water turbine draft tube, increase degree of vacuum in the draft tube, promptly increased the water turbine effective head, increased unit output, improve streamflow regime simultaneously, improved the efficient of unit.Realize improving the purpose of wet season economic benefit of hydropower sta.

Description

Utilizing the unnecessary water yield of wet season to increase the water power plant exerts oneself

The invention belongs to hydraulic power generation technology, be used for the construction of hydropower stations and the technical innovation of existing water power plant, increase economic efficiency.Through consulting the relevant technologies data, the home and abroad does not still have technical data and the equipment identical with the present invention.

The waterpower resourses popular feature be the water yield with the difference in season, dry season and wet season flow differ greatly.This force resource development utilization of just feeding water brings great difficulty.The design in general water power plant is considered to utilize the advantage that may realize the high head operation in dry season, and by the operation of optimum efficiency operating mode, performance only has the optimum efficiency of flow.Drop into armamentarium in the wet season,, make full use of the water yield, obtain more electric energy by maximum capability operation.Dry season is little because of flow, and the wet season is low because of head, and output of power station is all lower.Having only low water and between the wet season, flow is moderate, can keep higher head, is the efficiently full good period of sending out of water power plant.

Determine the electric motor power in water power plant, need the factor of consideration a lot, but basic principle is: promptly will make full use of waterpower resourses, reduce investment again as far as possible.Increase electric motor power, can more make full use of the water yield of wet season, increase electric energy, can not make full use of but electric motor power increases investment increase electromechanical equipment.

The electric motor power in general water power plant, except minority has for many years the water power plant of balancing reservoir fully, the water yield is outside adjusting can all utilize, and most water power plants can not all utilize, and the wet season will be abandoned water.Along with the reservoir adjusting function weakens, wet season in dry season flow difference increases, and it is long to abandon the water time, abandons water yield increase.

For example the Ge Zhou Ba is the water power plant that does not have regulating power, 18.6 meters of design heads, as long as flow is enough, can completely send out 271.5 ten thousand kilowatts, but when 10.6 meters of minimum heads season appearred in abundance of water, flow was enough, can only send out 116.8 ten thousand kilowatts because of head is low, when 8.3 meters of special minimum heads occurring, the power station only can be sent 810,000 kilowatts.The abundant water yield can not be utilized and discard wet season, and output of power station descends again significantly.Not only the power station benefit is suffered a loss, and also brings very big difficulty for Operation of Electric Systems, and measure is unfavorable, and the power cuts to limit consumption loss is bigger.As seen research makes full use of the water yield of wet season, improves the wet season operating conditions, increases the wet season water power plant and exerts oneself, and is that a crucial problem the present invention mainly proposes to address this problem theoretical and concrete implementing measure in the hydraulic power generation technology.

Two characteristics that water turbine moves at the wet season low water head:

1, in the design of water turbine, design head is determined near the optimum efficiency district of combined characteristic.Optimum district is far away more when departing from, and decrease in efficiency is fast more.Accompanying drawing 1 is Francis turbine stator (item 1) and runner (item 2) relative position relation and turbine runner blade inlet velocity triangle (item 3) discharge velocity triangle (item 4).U in the inlet velocity triangle (item 3) ₁Be peripheral velocity, v ₁Be absolute velocity, w ₁Be relative velocity.During the low water head operation, generating unit speed is constant, peripheral velocity u ₁The size direction is constant, when guide vane opening is constant, and absolute velocity v ₁Direction is constant, and numerical value reduces, and becomes dotted line position, and promptly absolute velocity is v ₁' relative velocity is w ₁'.w ₁' numerical value reduces, direction also changes, and the runner bucket inlet side has been produced the negative angle of attack, and the disorderly current that make the runner bucket import produce the separation of flow and bump generation flow to a mouthful runner bucket, destroyed aerofoil profile and well streamed the blade hydraulic loss is strengthened, decrease in efficiency is faster.Item 4 is a discharge velocity triangle, u ₂Be the outlet peripheral velocity, generating unit speed is constant, and various operating modes are all identical, w ₂And v ₂Be outlet relative velocity and absolute velocity.When head reduces, w ₂Constant because of the constant direction of blade outlet angle, numerical value is corresponding to be reduced.Discharge velocity triangle changes to dotted line position, w ₂' and v ₂' be relative velocity and the absolute velocity after changing.Absolute velocity v ₂That has departed from design conditions axially goes out stream, has produced forward (turning to consistent with runner) circulation.Continue to descend with head, circulation is increasing, and circulation makes the decrease in efficiency of draft tube, produces the whirlpool band simultaneously, and the cavity cavitation increases the weight of, and pressure pulsation strengthens, and not only decrease in efficiency causes that also unit vibration strengthens, and influences unit and normally moves.

2, in the low water head operation, draught-height reduces, and the cavitation safe margin increases.In the water turbine design, for guaranteeing that good cavitation characteristics is arranged, be according to maximum head, various operating mode operations in the maximum capacity scope, the unit that unit requires minimum draught-height to determine is installed elevation.In wet season low water head operation, tailwater level is raised, draught-height further reduce (negative value increase) just draft tube inlet vacuum reduce.Tailwater level continues to increase, and draft tube inlet may become positive pressure.Very beneficial for runner bucket is not produced the aerofoil profile cavitation, just the safe margin of cavitation increases.Should be pointed out that as previously mentioned, the low water head operation, what aerofoil profile was good streams destroyed and the increase of cavity cavitation, and cavitation damage still exists.

Utilize the water power plant in the big advantage of wet season low water head operation cavitation safe margin, utilize the unnecessary water yield, improving flow velocity mends in the water turbine draft tube, increase the degree of vacuum in the draft tube, promptly increased the water turbine effective head, increase unit output, improved streamflow regime simultaneously, improved unit efficiency.

The water power plant head depends on the water levels of upstream and downstream height, with unit elevation is installed and is had nothing to do, and the water turbine effective head depends primarily on runner bucket front backside pressure difference.After unit installation elevation was determined, the pressure in runner bucket front depended on the upper pool elevation height, moves near the wet season upper pool elevation can remain on normal high water level (N.H.W.L.), and promptly face of blade pressure and dry season are close.Vacuum side of blade generally is to form vacuum (negative pressure) under the high-velocity flow effect, and draft tube top also is vacuum, and its size is directly related with the tailwater level height.The wet season tailwater level is raised and is made vacuum side of blade and draft tube inlet, and degree of vacuum reduces, and promptly the water turbine effective head reduces.The water yield that wet season is unnecessary improves flow velocity and mends into draft tube, and the phase Conversion of energy of making is a vacuum in the draft tube, has increased the pressure difference value at the face of blade and the back side, has increased the water turbine effective head, has promptly increased unit output.As seen increase to exert oneself what, depend on the size of cavitation safe margin and unnecessary flow at this moment.

Because the water turbine effective head increases, its operating conditions transforms to the high head operation, and accompanying drawing 1 import and discharge velocity triangle are to transform to solid line position from dotted line position, promptly close to design conditions optimum efficiency district, rotary wheel of water turbine import current improve, and loss reduces, and efficient improves.Circulation in the draft tube reduces, and has improved disorderly streamflow regime, and cavity cavitation and pressure pulsation all improve, and has increased the stability of unit operation.

As seen utilize the unnecessary water yield of wet season, not only can increase effective head and increase unit output, and improve the hydraulic turbine operation operating mode, improved efficient, increased electric energy, reduced pressure pulsation, increase unit operation stability.It is the good technology of killing three birds with one stone.

Accompanying drawing 2 is represented the position relation of rotary wheel of water turbine (item 1) draft tubes (item 2) tailwater levels (item 3), and 456 of items are the positions of introducing press water water pipe.4 is aqueducts that the Taper Pipe section is arranged along circle edge, and 5 is the aqueducts along height placement in horizontal proliferation section both sides, and 6 is the level aqueducts that diffuser arranges along the upper level direction that make progress.Partition packet is established the gate control water yield, makes streamflow regime better with control generation degree of vacuum size and adjusting.Principle is to mend into press water along perisporium, easily improves fluidised form, reduces pulsation.Aqueduct and draft tube wall construction mode such as accompanying drawing 3, item 1 is an aqueduct, item 2 is a draft tube.

The several problems that adopt present technique in water power plant design and water turbine design, should consider:

1, in water power plant design, under the possible situation, reduces unit as far as possible elevation is installed, increase the cavitation safe margin,, increase head, create advantageous conditions for utilizing unnecessary press water.

2, take the present technique turbine draft tube to exceed original function, should increase its height, length, with the resume speed ability behind the increase adding high-velocity flow.

3, mend the size of the pressure water yield, the amount of capacity of pressing unit, head size and the power vacuum value that needs to increase are determined, should consider in the calculating that the outlet velocity loss is bigger, allow some leeway.With good conditionsi pressing decided the model test of type and accurately determined.Mend the implantation site and press the strong and weak item 4 of effect,

item

5,6 application successively.

4, present technique can be used to solve the three gorges hydropower plant cofferdam phase and initial stage unit low water head operation stability problem, can increase benefit simultaneously.The three gorges hydropower plant initial stage water yield is very more than needed, presses the high head design, and almost erosion safe margin is also very big, and condition is sufficient.

5, draft tube and pressure diversion conduit all need increase the cavitation wear protective measures.

6, present technique is determined scheme with existing power plant retrofit by actual conditions, still can obtain big benefit.

Claims

The invention belongs to hydraulic power generation technology, be used for the construction of hydropower stations and the technical innovation of existing water power plant, increase economic efficiency.

Construction of hydropower stations ubiquity wet season tailwater level height, and head reduces, and exerts oneself and reduces the decline of 1.5 powers by head, and simultaneously big water gaging is discarded and can not utilize, and the wet season benefit is impaired.

Feature of the present invention is: utilize the wet season head low, the advantage that unit operation cavitation safe margin is big, utilize the unnecessary water yield, improve flow velocity and mend in the draft tube of water turbine, increase the true degree in the tail pipe, promptly increased the water turbine effective head, increase unit output, improve streamflow regime simultaneously, improved unit efficiency, increased the principle of water power plant wet season economic benefit.

For realizing the foregoing invention principle, proposition is mended organization plan into high-velocity flow to draft tube, it is characterized in that Taper Pipe section horizontal proliferation section at draft tube, mend into high-velocity flow along the tail water tube wall at level three positions of diffuser that make progress, the control of gate partition packet is established in water inlet, and control produces the degree of vacuum size and regulates inflow and distributes in order to the moisturizing scheme that obtains good streamflow regime.