Method for transforming a hydroelectric station axial fixed-paddle unit into an axial variable-pitch unit

Abstract

The application belongs to the technical field of hydroelectric power generation, and particularly discloses a method for transforming an axial fixed-paddle type unit of a hydroelectric power station into an axial rotating-paddle type unit, and the transformation of the runner chamber of the axial fixed-paddle type unit into the axial rotating-paddle type unit: the cross section of the runner of the axial fixed-paddle type unit is transformed into a nearly spherical shape; after the transformation of the runner chamber is completed, a margin is left in the processing of the runner, and after the installation of the runner chamber is completed, the gap fit precision of the runner of the axial fixed-paddle type unit and the runner chamber is ensured by taking the original unit concentric and coaxial runner chamber inner diameter as a reference and turning the runner outer diameter; the transformation of the axial fixed-paddle type unit into the axial rotating-paddle type unit includes the transformation of the generator, the transformation of the water turbine, the transformation of the main shaft of the generator and the water turbine; and the hub is oil-free. The application greatly reduces the operation and maintenance difficulty and the operation and maintenance workload, completely eliminates the problem of oil leakage of the runner pitch control part polluting the river, and greatly reduces the engineering cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydroelectric power generation, in particular to a method for transforming an axial fixed-blade unit into an axial variable-pitch unit in a hydroelectric power station. BACKGROUND

[0002] The axial variable-pitch unit has high efficiency and is suitable for hydroelectric power stations with large changes in water head and flow rate, and is a more advanced type of axial unit. However, this type of unit has a complex structure, is difficult to maintain, is prone to oil leakage in the runner body, pollutes the river, and has a high cost. For technical and economic reasons, low-head hydroelectric power stations generally do not choose this type of unit, and instead choose axial fixed-blade units with low cost, simple structure, and easy operation and maintenance, at the expense of efficiency and operational flexibility. A small number of large-capacity hydroelectric power stations use axial variable-pitch units, but the oil leakage in the pitch control circuit often occurs and is difficult to maintain, and the oil leakage in the pitch control circuit is often difficult to solve. In severe cases, 2 to 3 large barrels of oil are added to the pitch control circuit every month, and the oil pollution of the environment reaches a very serious level. The present application uses corresponding technical measures to realize oil-free operation of the hub in the axial variable-pitch unit, and greatly simplifies the technical complexity of the most complex runner pitch control part. The mechanical efficiency of this part of the equipment is improved, the operational and maintenance difficulty is greatly reduced, the internal runner body is basically not maintained, the operational and maintenance engineering is greatly reduced, the engineering cost is greatly reduced, and the problem of oil leakage and pollution of the river by the runner pitch control part is completely eliminated, which has significant environmental protection benefits. Due to these significant technical and economic advantages, the pitch control circuit of the early axial variable-pitch unit is transformed, the oil pollution of the environment is completely solved, the maintenance difficulty of the axial variable-pitch unit is greatly reduced, the maintenance period is shortened, the loss of shutdown and power failure is reduced, and the labor intensity of maintenance is reduced. At the same time, the great advantages of the transformed axial variable-pitch unit enable early large-capacity axial fixed-blade units to be transformed into axial variable-pitch units, so that these old and inefficient units can adapt to large changes in the water head and flow rate of the river section of the hydroelectric power station, can be flexibly adjusted in time, and can run at a high efficiency point under different water head and flow rate conditions, so that the average efficiency of the unit is greatly increased, the vibration and swing of the unit are reduced, the average output is increased, the power generation capacity is increased, and the economic benefits can be greatly improved. With the progress of science and technology and the development of the times, outdated production equipment is eliminated, the potential of existing equipment is tapped, the operational performance of existing equipment is further improved, hidden dangers are eliminated, efficiency is improved, and economic benefits are improved, which is the basic starting point for the transformation of old and outdated equipment in the hydroelectric industry under the new situation. SUMMARY

[0003] The present application aims to provide a method for transforming an axial fixed-blade unit into an axial variable-pitch unit in a hydroelectric power station, to solve the technical problems presented in the background.

[0004] In order to achieve the above object, the application provides a method for transforming a fixed-paddle axial-flow unit of a hydropower station into a variable-pitch axial-flow unit, which adopts the technical scheme as follows.

[0005] The method for transforming a fixed-paddle axial-flow unit of a hydropower station into a variable-pitch axial-flow unit comprises the following steps.

[0006] The transformation of the runner chamber of the fixed-paddle axial-flow unit into the variable-pitch axial-flow unit comprises the following steps.

[0007] After the transformation of the runner chamber is completed, a margin is left in the processing of the runner, and after the runner chamber is installed, the margin is removed by turning the outer diameter of the runner, so as to ensure the gap fit precision of the fixed-paddle axial-flow unit runner and the runner chamber.

[0008] The transformation of the fixed-paddle axial-flow unit into the variable-pitch axial-flow unit comprises the following steps.

[0009] The hub is oil-free.

[0010] Further, the transformation of the cross section of the fixed-paddle axial-flow unit runner into a spherical shape comprises the following steps.

[0011] The original steel lining of the spherical runner chamber is positioned and marked, the height of the original runner chamber steel lining to be removed is determined, the corresponding part of the original runner chamber steel lining is cut off, and the concrete is struck on the basis of retaining the original steel bars to form a working surface for installing new steel lining.

[0012] The steel lining with a spherical cross section of the variable-pitch runner is pre-processed as new steel lining, a plurality of tie bars (to prevent deformation after cutting) are welded on the inner surface of the new steel lining, and the new steel lining is divided into three parts.

[0013] Based on the working surface, the new steel lining divided into three parts is hoisted into the runner chamber and spliced into a whole ring.

[0014] Further, the hoisting of the new steel lining divided into three parts into the runner chamber and splicing into a whole ring based on the working surface comprises the following steps.

[0015] In the case that the center point of the steel lining coincides with the center point of the seat ring, the center of the spliced steel lining is corrected based on the center of the unit seat ring, and is fixed by spot welding and anchor rod reinforcement, and welding points are added around the steel lining.

[0016] After the steel lining is fixed with the runner chamber and the draft tube and the center positions coincide, symmetrical welding is performed to complete the welding of the whole runner chamber steel lining and ensure that no deformation and center point displacement occur during the welding process.

[0017] Supplemental encryption anchor rod, drill a hole in the runner steel lining, implant an expansion bolt in the hole and fasten it as a reinforcing pull between the steel lining and the concrete behind the steel lining, the end of the expansion bolt is lower than the inner plane of the steel lining, and the end of the expansion bolt is tightly welded with the steel lining by surfacing method;

[0018] Open a hole in the upper part of the circumference of the steel lining and keep the small pieces of circular steel material cut off; fill high-strength concrete behind the steel lining from the hole in the steel lining and compact it by vibrating;

[0019] Based on the small pieces of circular steel material, close the opened steel lining hole from bottom to top by surfacing method, fill high-strength mortar or epoxy resin concrete chemical leakage stopping agent into the hole at the upper part of the hole, and finally close the grouting port, polish the runner chamber weld scar, and polish the lining and anchor rod weld to be smooth.

[0020] Further, the modification of the generator specifically includes:

[0021] The stator and rotor of the generator remain unchanged, and the insulation of the stator and rotor is replaced from the original B-grade insulation to F-grade insulation.

[0022] Further, the modification of the water turbine specifically includes:

[0023] The original water turbine fixed embedded parts remain unchanged, including the water turbine draft tube, air supplement cross, bottom ring, seat ring, support cover, top cover, fixed guide vane, and movable guide vane;

[0024] Customize a runner integration that cooperates with the original water turbine fixed embedded parts according to the requirements of the axial flow variable pitch unit, including the modification of the runner hub, runner blade, runner paddle rotating shaft, paddle driving support, and paddle driving booster of the variable pitch unit.

[0025] Further, the modification of the generator and water turbine main shaft specifically includes:

[0026] The original large shaft of the axial flow fixed pitch hydro-generator unit is modified into the large shaft of the axial flow variable pitch unit.

[0027] Further, the modification of the original large shaft of the axial flow fixed pitch hydro-generator unit into the large shaft of the axial flow variable pitch unit specifically includes:

[0028] Remove the original welded closed part at the end of the original large shaft and modify it into a hollow shaft.

[0029] Further, the oil-free hub specifically includes:

[0030] Move the original pitch adjusting booster arranged in the upper part of the runner body to the top of the generator;

[0031] The push-pull rod is connected between the pitch adjusting ring and the pitch adjusting servomotor in a rigid structure.

[0032] The present application has the following advantages:

[0033] The present application uses corresponding technical measures to transform the axial fixed-pitch unit into an axial variable-pitch unit, improves the characteristics of the hydroelectric generating set to adapt to the large changes in the local river water head and flow, greatly improves the efficiency of the water turbine, thereby increasing the output of the unit and increasing economic income. During the transformation, the runner pitch adjusting circuit is revolutionarily improved, thereby greatly simplifying the technical complexity of the pitch adjusting part, greatly reducing the operation and maintenance difficulty, greatly reducing the operation and maintenance workload, completely eliminating the problem of oil leakage pollution of the river by the runner pitch adjusting part, and greatly reducing the engineering cost. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0035] Fig. 1 : Schematic diagram of a conventional axial variable-pitch hydroelectric generating set pitch adjusting mechanism;

[0036] Fig. 2 : Schematic diagram of the installation of the structure principle of a conventional axial variable-pitch hydroelectric generating set pitch adjusting servomotor;

[0037] Fig. 3 : Schematic diagram of the transformation of an axial fixed-pitch into an axial variable-pitch hydroelectric generating set. DETAILED DESCRIPTION

[0038] The embodiments of the present application will be described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the present specification. The present application can also be implemented or applied by different specific embodiments, and the details in the present specification can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict.

[0039] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples.

[0040] The application relates to the technical field of hydropower generation, and particularly relates to the transformation of old and low-efficiency axial flow fixed-paddle type units into hydropower stations suitable for the great change of water head and flow of local river channels, and the corresponding great improvement of unit efficiency, economy, environmental protection and other performances.

[0041] Based on this, the application provides a method for transforming an axial flow variable-paddle type unit into an axial flow variable-paddle type unit, the axial flow fixed-paddle type unit is transformed into the axial flow variable-paddle type unit by adopting corresponding technical measures, the characteristics of the water-turbine generator unit suitable for the great change of water head and flow of the local river channel are improved, the efficiency of the water turbine is greatly improved, thereby the unit output is improved, and the economic income is increased.

[0042] Specifically, please refer to Figs. 1-3 The application is a method for transforming an axial flow fixed-paddle type unit into an axial flow variable-paddle type unit. Due to technical reasons, the water power industry adopts a large number of axial flow type units for low water head (several meters to 20 water head sections), which are divided into axial flow variable-paddle type and axial flow fixed-paddle type units, and in recent years, bulb tubular type units are also used. The axial flow variable-paddle type unit has high efficiency and is suitable for hydropower stations with great change of water head and flow, and is a relatively advanced type of axial flow type unit. However, the structure of the unit is complex, maintenance is difficult, the runner body is prone to oil leakage and pollution of the river, and the cost is relatively high. Generally, low water head hydropower stations do not dare to choose this type of unit due to technical and economic reasons, and sacrifice efficiency and operation flexibility to choose low-cost, simple-structure and easy-to-maintain axial flow fixed-paddle type units. With the passage of time and the development of the times, technical transformation of old equipment is carried out to eliminate hidden dangers, improve efficiency and economic benefits, which has become the development direction of technical transformation of the water power industry in recent years. The patent is urgently needed for the technical transformation of the industry under the new situation.

[0043] The transformation of the axial flow fixed-paddle type unit into the axial flow variable-paddle type unit includes transforming the hub of the variable-paddle type unit, the runner blade, the runner blade rotating shaft and the blade driving support, the blade driving servomotor and the like. That is, the runner of the axial flow variable-paddle type unit is newly produced in a water-turbine generator manufacturing factory.

[0044] The large shaft of the original axial fixed-blade hydro-generator unit is changed into the large shaft of the axial variable-blade unit. The large shaft (also called main shaft) of the hydro-generator bears the important role of transmitting torque, has high strength, high material quality requirement, is generally a forged hollow shaft structure, and has very high cost. The axial fixed-blade unit only bears the role of transmitting torque, so the end of the large shaft is often welded and closed to form a solid shape after the forging process is completed. The large shaft of the variable-blade unit is hollow after the forging is completed, because the high-pressure oil pipe of the pitch adjusting servomotor is arranged in the central hole of the large shaft in addition to transmitting torque. When the axial fixed-blade unit is transformed, whether the main shaft should be kept or transformed or replaced should be studied. If there is no large-scale expansion, only the original capacity of the axial fixed-blade unit is changed into the variable-blade unit, the stress of the main shaft does not change greatly, the original large shaft can be kept, the original large shaft couplings, snap rings, shaft attachments, shaft collars and oil inlet holes at both ends of the large shaft are kept, and only the original welded and closed part at the end of the large shaft is turned. This method keeps the original large shaft and only needs a small amount of simple processing, which can save a large amount of cost.

[0045] Transformation of runner chamber of axial variable-blade unit

[0046] Because the cross section of the runner of the axial fixed-blade unit is trapezoidal and the cross section of the runner of the axial variable-blade unit is approximately spherical, the cross section of the runner of the axial fixed-blade unit needs to be transformed into a spherical shape, which is an important work that must be done and has great difficulty in transforming the old axial fixed-blade unit into the axial variable-blade unit. When the variable-blade unit operates, the blades rotate with the large shaft in the horizontal plane of the runner chamber and the blades also rotate with the blade shaft in the radial direction of the large shaft, so the blades have the composite motion of the above two motions. The end of the blade needs to keep a gap of about 5 mm with the wall of the runner chamber at any position in the composite motion, which cannot be too large or too small, cannot be rubbed or cannot be collided. If the gap is too large, water leakage will be serious and the efficiency will be affected. Therefore, the concentricity, roundness and center elevation of the runner chamber with the main unit have high requirements in the transformation of the cross section of the spherical runner chamber, and great attention should be paid in the transformation process.

[0047] Special work before installation of runner of axial variable-blade unit

[0048] Due to the requirement of high-precision cooperation between the runner chamber and the runner and the process of hoisting, centering and leveling of the runner chamber, errors are inevitable. In order to reduce the influence of errors in the work process, appropriate allowance should be left in the processing of the runner, and the runner is finally turned for finishing after the runner chamber is installed and checked carefully according to the results. That is, the inner diameter of the runner chamber is used as the reference to turn the outer diameter of the runner to accurately ensure the gap cooperation accuracy between the runner of the axial fixed-blade unit and the runner chamber. (See detailed description below).

[0049] After the implementation of the foregoing hub oil-free technology, the improved unit top cancels the rotary oil distributor, the impeller servomotor driven by the runner body no longer uses hydraulic drive, and there is no high-pressure hydraulic pipeline and corresponding sealing device for driving and opening, closing and oil return of the servomotor, and there is no high-pressure oil. After the transformation, the complex drive paddle part in the runner body does not need to be replaced and sealed (the pressure pipe channel connected with the servomotor sealing rubber part needs to be replaced frequently due to rotation wear or aging; this part is installed in the runner body, the runner body is installed at the lower part of the hydro-generator shaft, and the hydro-generator set needs to be completely disassembled, the generator needs to be completely removed and lifted out of the pit, the rotary oil pipe needs to be completely removed and lifted out of the pit, and the hydro-turbine shaft needs to be removed and lifted out of the pit to perform the operation of maintaining and replacing the servomotor oil circuit sealing; after the sealing is replaced, the disassembled equipment needs to be reassembled with high precision, and the run-in and test are re-performed. Each replacement of the servomotor circuit sealing is an extensive overhaul, which consumes more than one month, causes a power generation loss of more than one month, and makes the maintenance personnel very hard. This is a great technical advantage and economic advantage of the present application for the hydropower station using this type of machine.

[0050] After the transformation, there is no high-pressure oil in the runner body, and there is no oil pipe and sealing, so the problem of servomotor circuit leakage of the pump turbine unit is completely eliminated. This has a special important environmental protection effect on the power station downstream of the river channel requiring city water supply. This is a great environmental protection advantage of the present application for the hydropower station using this type of machine.

[0051] The servomotor and oil distribution system transformation in the present application is suitable for the servomotor system transformation of the existing axial flow servomotor unit and the axial flow fixed paddle transformation into the axial flow servomotor unit.

[0052] Application example:

[0053] Axial flow fixed paddle transformation into axial flow servomotor technology transformation of Zhangjiabridge power station of Pingguo management office in Pingshan County, Sichuan Province

[0054] 1. Project overview:

[0055] Zhangjiabridge power station of Dongfengqu management office is located in Xia'an and Fangbei village of Anjing township in Pingshan County, and is about 1.0 km away from the water inlet of Dongfengqu main canal. The power station was built and put into operation in 1995, with a designed installed capacity of 2x1500kW, an original rated water head of 5.5m, a designed reference flow of single machine 32.5m3 / s, and an axial flow fixed paddle type unit. The power station is connected to the grid through 1 back 10kV line in Xindu district Dafeng transformer substation.

[0056] The Zhangjiaqiao Power Station has been in operation for 21 years. The equipment is outdated and aging, and there are many potential safety hazards in the operation of the power station. The unit output is severely insufficient, and technical improvement is urgently needed. In the technical improvement, we adopted the method of not changing the hydraulic structure of the power station, not increasing the water level of the front pool, and not changing the flow passage of the unit. We transformed the water turbine into an axial flow propeller runner to improve the unit output. This approach has been quite successful.

[0057] 2. Transformation process

[0058] 2.1 Analysis of the reasons for the severe insufficient output of the power station

[0059] Through in-depth site visits and careful observation and analysis, we found that the power station is not only a power station but also a key water pipeline station. By comparing the daily water inflow and daily power generation over the past 10 years, we found that the unit output was severely insufficient. That is, under the condition of a certain hydraulic structure and water head, the power station has flowed through so much water, and the unit power generation has been reduced by about 50%.

[0060] Following this line of thought, we continued to explore whether the water was leaking. The distance from the intake gate to the pressure front pool of this power station is only about 500m, and there is no trace of seepage or leakage on the back slope of the canal embankment. The possibility of water leakage by 50% is very small. The channel end connects the pressure front pool, and the intersection angle between the channel center line and the front pool center line is small, and the corner is relatively smooth, so the water loss will not be large.

[0061] 2.2 Problems with the original unit

[0062] Through careful inquiries with several station directors, we learned that there was a strange phenomenon in the operation of the unit of this power station. That is, during the dry season when the river water inflow is small, the operation is difficult. When the river water inflow is less than 20m 3 / s, the unit output is very small, and it can only carry a load of tens of KW. Moreover, the unit also vibrates quite severely when the load is small. The irrigation area management department stipulates that all power stations on the Dujiangyan Canal system cannot block water during the dry season. Of course, the head of the East Canal main canal power station like Zhangjiaqiao Power Station must lead the way to implement the regulations of the water dispatching department. Since the water inflow is too small to operate stably, the front pool discharge gate is simply opened, and the unit does not generate electricity. The water is directly discharged from the previous pool to the downstream tail channel to ensure continuous flow in the downstream. At first glance, it seems correct for the water dispatching department to comply with the water dispatching department, and it seems correct to directly discharge water without generating electricity. After careful calculation, the problem is big. The original Zhangjiaqiao Power Station has two 1500KW units, both of which are ZD560A-LH-275 axial flow fixed propeller units, with a single machine rated flow of 32.5m 3 / s. Generally, axial flow fixed propeller units may not operate stably when the water inflow is less than 50% of the rated flow; while 20m / s is greater than 50% of the rated flow of this unit, 16.25m / s.3 / s, even if the operation is unstable can take 700KW or so load, not just a few kilowatt load! So this power plant unit output problem who can not solve, has been dragged down for a long time, the power plant has been running for more than 20 years. In fact, the main reason is that the water quantity and water head of the power station are often changed with the water quantity of the irrigation area and the water quantity of the downstream. The blade angle of the original selected axial fixed blade runner is a fixed value, which cannot be adjusted with the water quantity and water head. The lower edge of the fixed blade runner blade extends out of the runner chamber, and the counter-jet unit loses the constraint of the runner chamber and cannot form a reaction force to work. The water directly leaks to the tail water, resulting in low efficiency and serious output shortage!

[0063] 2.3 Modification requirements

[0064] Due to the expansion of the Dujiangyan Irrigation Area, the irrigation area management department has carried out precise water distribution, that is, the size of the total canal flow (that is, the flow through the power station) changes more frequently. The small flow (15-20m 3 / s) control time accounts for more than 5 months per year. After capacity expansion, the rated flow of the single machine of the power station is 35m 3 / s, that is, the unit flow changes from 15 to 35m 3 / s, which requires the unit to run stably and efficiently under the conditions of water head change from 4 to 5.5m. Obviously, only the axial flow variable pitch unit can meet the requirements. If it is a newly built power station, the axial flow variable pitch unit can be directly selected. The problem is that the power station is now being technically improved. It is impossible to completely rebuild the current situation under the condition that the water conservancy building and the upstream and downstream water level have been solidified. The only way is to adopt the method of transformation! The runner and runner chamber of the water turbine are the heart of the water turbine. The heart must be very cautious during surgery. In order to reduce the risk, we adopted the safe method of feeling the stones while crossing the river, and decided to use the axial fixed blade type for the 1# unit and the axial flow variable pitch type for the 2# unit. In addition, only one machine is needed during the dry season, which can run stably for a long time. There is no need to make both axial flow variable pitch and spend more money. Re-select the unit type: 1# ZD660-LH-275 (axial fixed blade), 2# ZD660-LH-275 (axial flow variable pitch)

[0065] 2.4 Axial fixed blade type unit to axial flow variable pitch type unit runner chamber transformation

[0066] Because the cross section of the axial fixed blade type unit runner is trapezoidal, the cross section of the axial flow variable pitch type unit runner is spherical, and the cross section of the axial fixed blade type unit runner needs to be transformed into spherical shape. This is a difficult work that must be done for the transformation of the old axial fixed blade type unit to the axial flow variable pitch type unit.

[0067] The specific method is: first, prepare the original steel lining at the lower part of the runner chamber where the ball-shaped runner chamber is to be transformed, and accurately position the line, determine the height of the original runner chamber steel lining to be removed, then cut off the part of the original runner chamber steel lining, and knock off about 15 cm deep concrete (when knocking off the concrete, the original steel bars need to be reserved) to form a working surface for installing new steel lining. Before the installation of the new steel lining, the manufacturer processes the steel lining with a spherical cross-section of the runner in a numerical control lathe (because the integrally processed runner chamber lining can be integrally hoisted when the power plant is newly built, but when the unit is transformed, the upper structure of the plant, the generator layer and the water turbine layer have already been built, and the integrally processed runner chamber lining cannot be hoisted into the runner chamber through the small hole of the generator pier. Therefore, the lining with a spherical cross-section of the runner chamber is first accurately processed on the numerical control lathe to ensure the accuracy), then a plurality of tie bars are welded on the inner surface of the lining, and the processed lining is cut into three pieces, and the cutting part is carefully marked for easy reassembly. The purpose of welding a plurality of tie bars in the lining is to ensure that the lining is not deformed during transportation, installation and assembly. The reason for dividing the lining into three pieces is that the lining can only be divided into pieces to be hoisted into the runner chamber through the small hole of the generator pier; and the three pieces are hoisted into the runner chamber, and then the three pieces are assembled into a complete runner chamber. It is noted that the three-piece lining is transported to the site after the original runner chamber steel lining is removed and the concrete is knocked off, and then the three pieces are hoisted into the runner chamber and welded into a complete circular ring, and the verticality, roundness and flatness of the upper and lower parts meet the requirements; then the center of the welded steel lining is corrected based on the center of the unit seat ring, and is fixed by spot welding and anchor rod, and then the welding points are added around the steel lining, and the center point of the steel lining is checked and calibrated to coincide with the center point of the seat ring at any time during the process; after the steel lining and the runner chamber and the draft tube are basically fixed and the center positions coincide, the welding is strictly symmetrical to complete the welding of the entire runner chamber steel lining to ensure that no deformation and center point displacement occur during the welding process. Then, the anchor rods are supplemented and added; the runner steel lining is in the shape of a plum blossom, and Φ20-25 drill bits are used to drill holes inward, with a hole depth of about 30 cm; expansion bolts are implanted in the holes and tightened to serve as steel lining reinforcement and tie bars, and the end of the expansion bolt should be slightly lower than the inner plane of the steel lining, and the end of the expansion bolt is tightly welded with the steel lining by means of surfacing; then, about 10 cm of a hole opener is used to open a circle of holes on the upper part of the circumference of the steel lining (attention should be paid to the small round steel pieces cut by the hole opener), and the hole distance is about 30 cm; high-strength concrete is poured from the holes in the steel lining and vibrated and compacted; the round steel pieces cut before are used to close the holes in the steel lining from bottom to top by means of surfacing, high-strength mortar or epoxy resin concrete chemical leakage stopping agent is poured into the hole at the upper part of the hole opening to seal the hole, and finally the pouring port is sealed, the welding scar of the runner chamber is polished, and the lining and the anchor rod hole are polished to be smooth and flat. The inner scaffolding of the draft tube is removed, and the unit is prepared for reassembly.

[0068] 2.5 Special work before installation of the axial flow Francis turbine unit runner

[0069] The runner of the modified axial flow variable pitch unit cannot be completely processed before delivery as the new unit production, and sufficient processing allowance should be left in the outer diameter direction when the runner blade is made. After the new runner chamber is installed, the roundness, center, and elevation are carefully checked, and the installation elevation and center of the generator are checked. Although the steel lining of the runner chamber has been completely processed in the factory before construction, it cannot be lifted into the machine pier orifice as a whole, but can only be divided into three parts and lifted into the lower part and connected into a whole. This process of division and assembly will inevitably cause deviations in roundness, diameter, and axis, affecting the precision of the runner and the runner chamber. Therefore, the runner cannot be processed at one time, and the size of the runner chamber after installation must be guaranteed to match the size of the runner. Therefore, the last processing turning allowance of the runner chamber must be left for the first factory processing. After the installation and inspection of the runner chamber are completed, the final inspection results are returned to the production factory, and the production factory will finally process the runner according to the actual size of the runner chamber on site. After accurate matching, the last turning is performed to ensure that the new runner chamber and the runner are strictly matched. Finally, the runner is transported to the site for installation. This small experience needs special attention!

[0070] 2.6 Modification method of axial flow fixed pitch unit to axial flow variable pitch unit

[0071] 2.6.1 Modification of the generator part

[0072] The stator and rotor of the generator remain unchanged, and only general maintenance is performed. If necessary, the stator and rotor insulation is replaced from the original B-class insulation to F-class insulation; the withstand temperature of the original B-class insulation is 105 O C, and the withstand temperature of the F-class insulation is 155 OC.In one aspect, the generator set fixed rotor insulation has gradually aged over the years. According to the regulations, the set should be regularly replaced after 15-20 years of use. In recent years, with the improvement of generator insulation technology, the F-class insulation temperature resistance has been improved, so that the output of the modified unit will increase by 7%-10% due to the improvement of efficiency and the optimization of the unit to water head flow. If the optimization of runner selection and the optimization of power station water head and flow channel cleaning are combined, the unit output can increase by more than 15%. By increasing the insulation, i.e. increasing the temperature resistance of the insulation, the generator output increases by 15-20, and the generator current increases with the increase of the output. The temperature of the generator is higher than before, but the temperature after the increase is still within the allowable range of F-class insulation. In addition, the insulation performance of F-class insulation is better than that of the original insulation, and the thickness of the insulation material is much thinner than that of the original insulation. The rotor conductor plus the insulation layer has more space in the original wire slot, which can be used to appropriately increase the conductor cross section at the same time of replacing the insulation, so as to achieve just full slot in the stator and rotor wire slot, increase the coil tightness in the wire slot, and improve the mechanical stability. At the same time, the flow capacity of the stator and rotor is increased, i.e. the capacity of the generator is increased. In combination with the replacement of the stator and rotor insulation, the stator and rotor wire slot, core, stator core compression screw, stator and rotor ventilation channel are repaired and fixed, and the original unit base is also reinforced and strengthened. After the above measures are comprehensively adopted, the unit output can be increased by 15%-20% after operation, and the operating temperature can be reduced by several degrees compared with the original. The vibration, runout, temperature and noise of the unit after operation are much better than before.

[0073] 2.6.2 Transformation of the water turbine part

[0074] The original water turbine fixed part is kept unchanged (except the runner chamber), i.e. the water turbine draft tube, air supplement cross, bottom ring, seat ring, support cover, top cover, fixed guide vane, movable guide vane, etc. are not changed; the runner hub, runner blade, runner paddle rotating shaft and paddle driving support, paddle driving booster, etc. are integrated and customized in a professional factory according to the requirements of the axial flow and paddle type unit, i.e. the runner is re-produced in the water turbine generator manufacturing plant according to the runner of the axial flow and paddle type unit.

[0075] 2.6.3 Transformation of the generator and water turbine main shaft part

[0076] The large shaft of the original axial flow fixed-blade hydro-generator unit is changed into the large shaft of the axial flow variable-blade unit. The large shaft (also called main shaft) of the hydro-generator bears the important role of transmitting torque, has high strength, high material requirement, is generally a forged hollow shaft structure, and has very high cost. The axial flow fixed-blade unit only bears the role of transmitting torque, so the end of the large shaft is often partially welded and closed to form a solid shape after the forging process. The large shaft of the variable-blade unit has the high-pressure oil pipe of the pitch adjusting servomotor arranged in the central hole of the large shaft in addition to transmitting torque, so the large shaft of the variable-blade unit is not welded and closed after the forging process but has a hollow structure. When the axial flow fixed-blade unit is modified, whether the main shaft should be retained or modified or replaced should be studied. If there is no large-scale expansion and only the original capacity of the axial flow fixed-blade unit is changed into the variable-blade unit, the stress on the main shaft does not change greatly, so the original large shaft can be retained, the original shaft couplings, retaining rings, and shaft attachments such as shaft collars on the ends of the original large shaft are retained, and only the original welded and closed parts at the ends of the large shaft are removed to change the large shaft into a hollow shaft. This method retains the original large shaft and only needs a small amount of simple processing, which can save a large amount of cost.

[0077] 2.7 Adoption of oil-free technology for the hub

[0078] 2.7.1 Problems of the original axial flow variable-blade unit

[0079] The axial flow variable-blade unit has one more set of blade adjusting mechanism than the axial flow fixed-blade unit. At present, the blade adjusting part of all variable-blade units has the blade servomotor arranged in the upper part of the runner in the runner body, passes out from the top of the generator shaft through two connected two-layer oil pipes with three channels (the inner space of the first oil pipe, the space between the first and second oil pipes, and the three oil flow channels formed by the outer wall of the second oil pipe and the inner wall of the main shaft), and is connected with the rotating oil distributor. The variable-blade unit has four blades, and there are four blade shafts driven by the blade drive adjusting ring. The blade drive servomotor, three-layer oil pipeline, and blade drive ring are all arranged in the hollow runner body hub. There are many elements, and the structure is very complex. It is very difficult to manufacture, install, and maintain. There is also a major problem with this structure, i.e., the sealing of the runner body, the sealing of the connecting shafts, and the sealing of the connecting oil pipes often leak oil. The oil leaked from the runner body into the tailwater section causes serious oil pollution to the downstream river water.

[0080] 2.7.2 Main advantages of the original axial flow variable-blade unit

[0081] The axial flow variable-blade unit has so many difficult problems in the pitch adjusting circuit, but this type of unit has high efficiency and can adapt to large changes in water head and flow, so it is widely used. It can be said that since this type of unit was born, it has been in this structure. People have accepted the advantages of this type of unit, as well as the various difficulties and complexities of manufacturing, installation, maintenance, and maintenance, and the serious oil leakage.

[0082] 2.7.3 Hub oil-free technology for axial flow variable pitch turbine

[0083] How to break the traditional thinking to simplify the structure of the unit, reduce the complexity of the unit, reduce the pollution of oil leakage to the environment? The specific method is to move the pitch regulating gear originally arranged in the upper part of the runner to the top of the generator, that is, the earliest position of the generator exciter; the pitch regulating ring is unchanged, and a rigid and simple push-pull rod is used to connect the pitch regulating gear and the pitch regulating ring. That is, the pitch regulating gear still directly drives the pitch regulating ring. The pitch regulating gear is moved out of the runner body and connected to the pitch regulating ring in the runner body by a push-pull rod. After using this modification method, the large shaft of the water turbine and the large shaft of the generator do not need the oil pipe with two layers of pipes and three oil paths, and the large shaft and the hub no longer have oil, so the oil supply pipe connection is no longer required, and the sealing is no longer required. There is no oil in the hub and the large shaft, so there is no sealing and oil leakage problem, and the problem of oil leakage pollution that has existed for many years is solved.

[0084] After years of research and modification, the key equipment installation layout of the hydraulic drive paddle booster on the top of the generator was completed. The generator was replaced with a new set of stator and rotor coils, the insulation was replaced with F-grade insulation, the water machine was modified to ZZ660-LH-275 model, the pitch governor was added and matched with the pitch booster on the top of the generator, the pitch governor and guide vane governor were linked and operated in stages, and the runner chamber was modified from trapezoidal section to spherical section. The installation, debugging and finally the completion of the modification work of the axial flow fixed-paddle to axial flow variable-paddle unit were completed. The test results show that the single machine can run stably at 500KW at low load from small flow, and the single machine can run stably at 1750KW at high load from large flow. Through on-site comparison and operation, it can be seen that under the same conditions of the same power station, two units with the same capacity and runner diameter, one unit is an axial flow fixed-paddle unit and the other unit is an axial flow variable-paddle unit, under the same water level of the front pool and tail water and the same guide vane opening, the output of the axial flow variable-paddle unit is 80-200kW higher than that of the axial flow fixed-paddle unit at small, medium and large openings. When the output of the two units is the same, the guide vane opening of the axial flow variable-paddle unit is 5%-8% smaller than that of the axial flow fixed-paddle unit, indicating that the axial flow variable-paddle unit consumes less water under the same output. After modification, the annual power generation capacity is increased from 9 million kwh to 10 million kwh to 15 million kwh to 16 million kwh, which is very significant. Moreover, the vibration, runout, temperature rise of the unit during operation are much better than those of the original unit. The technical improvement project started in 2012 and went through ten stages of scheme proposal, scheme approval, national approval, bidding, construction preparation, construction, trial operation, formal operation, completion acceptance, and national formal completion acceptance. The formal efficiency expansion and formal completion acceptance were completed before the end of last year, indicating that the axial flow fixed-paddle unit modified into an axial flow variable-paddle unit has very good operation effect and economic effect.

[0085] The above embodiments are only used to illustrate the present application, but not to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all equivalent technical solutions belong to the scope of the present application, and the patent protection scope of the present application should be defined by the claims.

Claims

1. A method for converting a Francis turbine into a Francis pump, characterized in that, The method comprises the following steps: The runner chamber of the axial fixed-pitch unit is changed into a runner chamber of the axial variable-pitch unit, and the cross section of the runner of the axial fixed-pitch unit is changed into a spherical shape; After the runner chamber is changed, a margin is left in the processing of the runner, and after the runner chamber is installed, the gap between the runner of the axial fixed-pitch unit and the runner chamber is ensured to be accurate by turning the outer diameter of the runner and taking the inner diameter of the runner chamber of the original unit as a reference; The method for changing the axial fixed-pitch unit into the axial variable-pitch unit comprises the following steps: The hub is oil-free; The cross section of the runner of the axial fixed-pitch unit is changed into a spherical shape, and the method comprises the following steps: A line is drawn on the original steel lining of the runner chamber to determine the height of the original runner chamber steel lining to be removed, and the corresponding part of the original runner chamber is cut off, and the concrete is struck on the basis of the original steel reinforcement to form a working surface for installing the new steel lining; The steel lining with a spherical cross section of the runner of the variable-pitch unit is pre-processed as the new steel lining, a plurality of tie bars are welded on the inner surface of the new steel lining, and the new steel lining is divided into three parts; The new steel lining divided into three parts is hoisted into the runner chamber based on the working surface and is spliced into a whole ring; The new steel lining divided into three parts is hoisted into the runner chamber based on the working surface and is spliced into a whole ring, and the method comprises the following steps: The center of the spliced steel lining is corrected based on the center of the unit seat ring, and the center is fixed by spot welding and is further fixed by anchoring and reinforcing, and welding points are added around the upper and lower parts of the steel lining; After the steel lining is fixed with the runner chamber and the draft tube and the center positions coincide, the whole steel lining of the runner chamber is welded by symmetrical welding, and the center point is ensured not to be displaced during the welding process; The anchoring and reinforcing is further strengthened by punching holes in the steel lining, implanting expansion bolts in the holes and fastening the expansion bolts, the expansion bolts are used as reinforcing tie bars of the steel lining and the concrete behind the steel lining, the end of the expansion bolt is lower than the inner surface of the steel lining, and the end of the expansion bolt is tightly welded with the steel lining by the surfacing method; A plurality of holes are formed on the upper part of the circumference of the steel lining, and the cut-off circular steel pieces are reserved, high-strength concrete is poured into the holes of the steel lining and is vibrated and compacted, and the holes are finally closed. The method for changing the axial fixed-pitch unit into the axial variable-pitch unit comprises the following steps: The hub is oil-free; The cross section of the runner of the axial fixed-pitch unit is changed into a spherical shape, and the method comprises the following steps: A line is drawn on the original steel lining of the runner chamber to determine the height of the original runner chamber steel lining to be removed, and the corresponding part of the original runner chamber is cut off, and the concrete is struck on the basis of the original steel reinforcement to form a working surface for installing the new steel lining; 2. The method of converting a Francis axial fixed-blade hydroelectric generating unit into an axial variable-pitch hydroelectric generating unit as claimed in claim 1, wherein, The steel lining with a spherical cross section of the runner of the variable-pitch unit is pre-processed as the new steel lining, a plurality of tie bars are welded on the inner surface of the new steel lining, and the new steel lining is divided into three parts; The new steel lining divided into three parts is hoisted into the runner chamber based on the working surface and is spliced into a whole ring; 3. The method of converting a Francis axial fixed-blade hydroelectric generating unit into an axial variable-pitch hydroelectric generating unit as claimed in claim 1, wherein, The new steel lining divided into three parts is hoisted into the runner chamber based on the working surface and is spliced into a whole ring, and the method comprises the following steps: The center of the spliced steel lining is corrected based on the center of the unit seat ring, and the center is fixed by spot welding and is further fixed by anchoring and reinforcing, and welding points are added around the upper and lower parts of the steel lining; After the steel lining is fixed with the runner chamber and the draft tube and the center positions coincide, the whole steel lining of the runner chamber is welded by symmetrical welding, and the center point is ensured not to be displaced during the welding process; The anchoring and reinforcing is further strengthened by punching holes in the steel lining, implanting expansion bolts in the holes and fastening the expansion bolts, the expansion bolts are used as reinforcing tie bars of the steel lining and the concrete behind the steel lining, the end of the expansion bolt is lower than the inner surface of the steel lining, and the end of the expansion bolt is tightly welded with the steel lining by the surfacing method; A plurality of holes are formed on the upper part of the circumference of the steel lining, and the cut-off circular steel pieces are reserved, high-strength concrete is poured into the holes of the steel lining and is vibrated and compacted, and the holes are finally closed. The method for changing the axial fixed-pitch unit into the axial variable-pitch unit comprises the following steps: The original shaft flow fixed-blade hydro-generator set large shaft is transformed into a shaft flow variable-pitch set large shaft.

4. The method of converting a hydroelectric plant fixed-pitch axial flow propeller unit into a variable-pitch axial flow propeller unit as claimed in claim 3 wherein, The original shaft flow fixed-blade hydro-generator set large shaft is transformed into a shaft flow variable-pitch set large shaft, and specifically comprises the following steps. The original welded closed part at the end of the original large shaft is removed, and the large shaft is transformed into a hollow shaft.

5. The method of converting a Francis hydroelectric axial fixed-blade unit into an axial variable-pitch unit as claimed in claim 1, wherein, The hub is oil-free, and specifically comprises the following steps. The original pitch adjusting gear arranged in the upper runner body of the runner is moved out of the runner body and arranged on the top of the generator. The pitch adjusting ring is kept unchanged, and a rigid structure push-pull rod is arranged between the pitch adjusting gear and the pitch adjusting ring.

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