XILUODU hydropower station

The world's fourth largest hydropower station and the world's first high arch dam power station with a capacity of tens of millions of kilowatts

Xiluodu hydropower station is located in Qinghai-Tibet Plateau, Yunnan-Guizhou Plateau to the Sichuan Basin transition zone, located in Xiluodu Gorge, where bordering Leibo County, Sichuan Province and Yongshan County, Yunnan Province, Xiluodu Hydropower Station is the largest of the four giant hydropower station on Jinsha River, Capacity quite with the Itaipu,the world's second largest hydropower station.total installed capacity is 12.6 million kilowatts, Annual generation capacity ranked third in the world,is 571.2 billion KWh, equal to Itaipu hydropower station, and three and a half of the Gezhou Dam, is the second largest hydropower station in China.

Jinsha river is upper stream of Yangtze river,total length 3364 kilometer, drainage area 473.2 thousand sq.km. Jinsha river has abundant water resources, reserves energy reached 112.4 million kilowatts, accounted for 1/6 of the total hydropower in China.

Xiluodu hydropower station is the closest key power of China “west to east power transmission project” on Jinsha river, also the largest hydropower station on Jinsha river.

The project use concrete double curvature arch dam,dam height 278m, normal storage water level 600m, total storage 11.57 billion cubic meters, Regulation storage 6.46 billion cubic meters, installed capacity 12.6 million KW, average annual generating capacity of 57.12 billion KWH, the project static investment 45.928 billion Yuan, total 79.234 billion Yuan. Project feasibility design finished on Dec. 2001, start building on Dec.2005, on Jun.2013, the first set of generator put into operation, and whole project completed on 2015.

Xiluodu Hydropower station use vertical Francis hydro turbine, manufacturer Voith, rated water head 197m, max. Head 229.4m, min. Head 154.6m, weighted average of the head 223.48m, rated flow 430.5 cubic meter per second, rated output power 784 Megawatt, rated speed 125 r/min,suction head HS=-10.81m, installation elevation 359m. Francis runner diameter is 7.4m, max. Outer diameter 7.755m, height 3.462m, each runner weight 179 ton. Material is stainless steel 0Cr13Ni4Mo.

the main parameter of hydro turbine: 

Overall structure and main parameters of the turbine

1. Rotator Parts- turbine runner

The runner is the core component of the turbine, and its function is to convert the energy of the water into the kinetic energy of the runner's rotation. The runner consists of an upper crown, a lower ring and 15 blades, all made of ZG06Cr13Ni4Mo. The blades are required to be cast using electric furnace steelmaking +VOD(or AOD) refining technology, and each piece is processed by numerical control and then assembled into a whole on the site. The dynamic and leak-stopping rings are directly set on the runner and are integrated with it.
The runner diameter D is 7.4m, the maximum outer diameter is 7.53m, height 3.462m, the runner is an integral structure, weighing approximately 240t as a whole, the upper crown, lower ring and blade are welded into a whole and processed and static balance tests are conducted on the construction site.Considering the overall performance, the runner is equipped with a long drainage cone. The material of the drainage cone is ZG06Cr13Ni4Mo, which is fixed under the runner by welding and joining.

 2.Turbine main shaft

The turbine main shaft is the power transmission component of the unit. The main shaft is of hollow force-welded structure, and the flange at the water turbine end of the main shaft is of middle flange structure. The generator end flange is an outer flange structure. The two flanges with part of the shaft body and the sliding rotor section shaft body are forged, made of ASTM A668 grade D forgings, and each piece is welded together as a whole with narrow gap welding. The outer diameter of the flange at the water machine end of the main shaft is 2.81m, the outer diameter of the flange at the generator end is 3.33m, and the outer diameter of the sliding rotor is 2.75m. The main shaft is 4.773m long and weighs about 110t. The main shaft and the runner are connected by bolts and torque is transmitted by pins and sleeves, and the main shaft and the generator shaft are connected by pins and bolts for torque transmission.

3. Top Cover

The outer diameter of the top cover is 10.70m, the inner diameter is 3.37m, and the height is 1.681m. It is a welded structure of steel plates, divided into 4 sections, and weighs approximately 290t as a whole.
As the turbine of the Xiluodu power Station is a water guide mechanism with a cylindrical valve, we paid special attention to the rigidity and strength of the top cover in its design. ASTM A516 Gr70-Z35 steel plate was used for the main flange of the top cover, and a middle shaft seat of Q345B material was set at the middle shaft diameter of the guide vanes. A ring plate, 170mm thick, was set at the corresponding position of the inner circular water guide bearing of the top cover to facilitate the transmission of the radial force of the water guide.

To reduce water leakage between the guide vanes and the top cover when the guide vanes are closed, the corresponding part of the top cover is equipped with a guide vanes end face seal, consisting of a bronze seal strip and a formed rubber strip on its back, relying on the elasticity of the formed rubber strip,And the water pressure that seeps into the space of the rubber strip achieves the purpose of sealing. The sealing strip and the formed rubber strip are mounted on the top cover by a stainless steel sealing pressure plate. Stainless steel anti-wear plates are set on the flow-through surface of the top cover.
Two G1/2 pressure measurement holes are set at the top cover area corresponding to the crown on the runner for measuring the water pressure in the crown cavity on the runner: 12 GI gas replenishment holes are set at the top cover area corresponding to the runner and guide vanes for forced gas replenishment (reserved) : Two G1/2 pressure measurement holes are set for measuring the water head behind the guide vanes; Four M30×1.5 holes are set at the fixed leak-stop ring for measuring the leak-stop ring gap between the runner and the top cover. A stainless steel fixed leak-stop ring of 0Gr18Ni9 is provided on the top cover, which is fastened to the top cover by welding to ensure its reliability.

4. Bottom Ring

The bottom ring is a cast-welded structure, that is, the upper and lower ring plates are welded to the lower shaft seat of the cast guide vanes. The outer diameter of the bottom ring is 9.716m, and the inner diameter is 7.202m, 0.515m high, structurally split into two segments. The total weight of the bottom ring is about 110t. To reduce the water leakage between the guide vanes and the bottom ring when they are closed, the corresponding components of the bottom ring are equipped with guide vanes end face seals, which have the same structure as the end face seals on the top cover, and stainless steel anti-wear plates are set on the flow surface of the bottom ring. To ensure the stable operation of the unit under certain special conditions, 12 G1 air replenishment holes are set at the corresponding bottom ring positions between the runner and the guide vanes for forced air replenishment (reserved).

5. Sub-bottom ring

A new type of secondary bottom ring was set up for the installation and adjustment of the replacement of the lower static drain ring. The secondary bottom ring is a welded structure. To ensure the rigidity of the secondary bottom ring and in combination with transportation conditions, the secondary bottom ring is an integral structure, which solves the problem of the leak-stopping ring type and reduces on-site construction difficulty. The stainless steel leak-stop ring material on the secondary bottom ring is inverted cabinet OCri8NI9, which is fastened to the secondary bottom ring by welding.

6. Guide vanes

The guide vanes are of uniform stainless steel mesh structure, made of ZG06Cr13N4Mo. The guide vanes are three-point negative curvature guide vanes with an upper axis diameter of 0.35m. The middle axis diameter is 0.39m, the lower axis diameter is 0.39m, the phase height of the guide vanes is 1.271m, the plastiform length is 1.18m, the total height of the guide vanes is 3.8m, the number of guide vanes is 24, each weighing approximately 3.8 ton.
The upper, middle and lower bearings corresponding to the three support points of the guide vanes, using self-lubricating sliding bearings, are respectively installed on the top cover and the bottom ring. High molecular polyurethane seals are installed at the middle and lower shaft sleeves to effectively prevent sediment and sealing water, and a special sleeve structure is installed at the middle journal position to facilitate the replacement of seals.

7.  Control Ring

The control ring is a welded structure of Ι-shaped steel plates. The upper ring plate is provided with two large ear holes connected to the relay, and the lower ring plate is provided with 24 small ear holes connected to the connecting rod in the guide vane operating mechanism. Maximum externality of the control ring 7.72m. Inner diameter 5.415m. Height 1.338m. Weight about 45t. Due to the size limitations of the transmission, the control ring adopts a segmented structure.
Self-sliding sliding bearings are arranged in the large and small ear holes. Side and bottom anti-wear plates made of self-lubricating material are set at the inner circle of the lower part of the control ring and the contact point between the bottom of the control ring and the top cover. A pressure plate is set between the top cover and the control ring to prevent the guide vane operating mechanism from being loaded onto the control ring due to uneven force.

8. Guide vane operating mechanism

The guide vane operating mechanism is composed of the guide vane arm, connecting plate, connecting rod, connecting rod pin, etc.
Two pins and an expansion pin sleeve are set between the guide vanes and the guide vanes arm to transfer the operating torque of the guide vanes. A thrust ring and a reverse thrust ring made of self-lubricating material are set between the guide vanes arm and the top cover to bear the weight of the guide vanes and to prevent the upward or downward water thrust acting on the guide vanes.
The connecting rod is a double-plate structure with eccentric pins, and the eccentricity of the eccentric pins is used to compensate for the positional error between the connecting parts caused by machining. A self-lubricating bearing is provided at the connection between the right connecting rod and the connecting plate. A scissor pin is provided between the guide vane arm and the connecting plate to ensure the normal operation of the other guide vanes when one guide vane is jammed by a foreign object.
A friction ring is set between the guide arm and the connecting plate to prevent the guide vanes from swinging repeatedly and rapidly after the shearing pin is disconnected and hitting the guide vanes limit block. A double guide vanes limit block is set on the top cover to prevent the guide vanes from rotating after the body is disconnected and hitting the adjacent guide vanes or the moving parts of the adjacent guide vanes. The limit range of the guide vane limit block is based on the maximum possible guide vanes The rotation Angle of the guide vane arm at the opening degree is taken as the standard.

9. Guide vanes servomotor

The function of the guide vane servomotor is to operate the water guiding mechanism according to the required oil pressure, so as to achieve the purpose of opening and closing the guide vanes. Xiluodu electric hydro turbine has two double guide straight cylinder guide vane servomotor in the +Y direction of the liner in the machine pit.
The diameter of the guide vane cylinder is 0.90m, the stroke is 0.560m, and the rated working oil pressure is 6.3MPa. The guide vane servmotor consists of a cylinder, cylinder head, cross cylinder (with rear cylinder head), piston, piston rod, piston ring, rod head, etc. The piston is connected to the piston rod by a retaining ring, and the piston rod is connected to the rod head by a threaded connection. Two leak-stopping combination rings are installed on the outer side of the piston to prevent oil leakage between the two chambers, and self-lubricating bearings for guiding and molded rubber sealing sides are installed on the front and rear cylinder heads of the servomotor. At the rear end of one of the servomotor, there is an oil pressure operation lock device to ensure that the turbine guide vanes are securely locked in the closed position and to prevent false start-up. At the same time, a limit device in the opening direction is set at the front end for manual opening restriction,.

10. Water guide bearing

The water guide bearing is the only shafting support component at the lower end of the hydroelectric generator set and plays a crucial role in the stable and reliable operation of the unit. The water guide bearing of Xiluodu Power Station is a thin oil stream sliding guide bearing, with a non-concentric block bearing arrangement, and the oil cooling system is an external circulation mode.
The structure allows for convenient inspection, adjustment and replace some components of the guide bearing from the upper part.  The bearing bush is made of Babbitt alloy and adopts non-concentric bearing bushing. There is no need to scrape the bearing bush at the construction site. The clearance adjustment of the bearing bush is accomplished by using wedge blocks, which is easy to adjust and reliable.

There are 24 bearing shells in the bearing. There is an oil level signal on the bearing to monitor the oil level in the bearing oil tank. There is an oil mixed water alarm device at the bottom of the bearing oil tank. There is one overflow gauge on each bearing shell. There are four moisture gauges in the bearing oil tank to monitor the oil moisture.

The water guide bearing oil cooler is set on the pit wall, with a total of 3 coolers, one of which is standby, and the coolers are arranged in a semi-coupling manner, and the circulating power of the oil is provided by the blowout rod pump, with a total of 2 screw pumps, One of them is on standby, and the cooling system parameters are as follows:

Heat exchange tube material:        T. Purple copper tube
Heat exchange tube diameter:       20mm
Total heat conversion power:        Greater than 100kW
Cooling water temperature:           20℃
Cooling water flow rate and pressure: 18m³, 0.4MPa
Cooling system inlet oil temperature:   50℃
Cooling system outlet oil temperature: Less than 35℃
Oil pump flow rate and pressure:          21m', 0.7MPa
Pressure resistance test of the cooler: 1.65MPa
Number of coolers:                              2 main units and 1 standby unit

11. Main shaft seal

The main shaft seal is divided (as shown in Figure 6) into maintenance seal and working seal, which are installed on the inner circular surface at the lower part of the top cover.

The maintenance seal uses an air band seal with an air pressure of 0.5 to 0.8MPa. When the unit is shut down, the band inflates and expands to closely adhere to the outer drawing of the lower flange of the main shaft, achieving the purpose of sealing.
The working seal is a movable lower end face seal. The working principle is as follows: The stainless steel sealing ring is fixed on the main shaft flange, the special composite material striking block fits onto the sealing ring, the sealing ring is installed inside the fastening ring, sliding contact is provided with a sealing ring, and during operation, it relies on the self-weight of the sealing ring, the spring force between the sealing ring and the fastening ring, and the water pressure in the sealing cavity. The sealing block is attached to the sealing ring to achieve the sealing effect.
The sealing ring and the sealing block have water holes. Clean water is used to lubricate and cool the contact surface between the sealing block and the sealing ring to prevent dry friction from burning the sealing block. Clean water pressure 0.5MPa. At the same time, because the sealing ring can move up and down, it can ensure the compensation for the gradual wear and tear of the seal and the normal sealing of the unit when the racket is used.

12. Embedded part

12.1 Seat ring

The overall weight of the seat ring is 390 tons. Considering manufacturing and transportation, it is divided into three sections, from top to bottom, are the support ring, the seat ring body, and the foundation ring. The seat ring body adopts a parallel straight transition plate and a guide ring welded structure, which is divided into 4 sections and welded on-site in sections. A temporary section is set on each half side of the section, and the section flange is provided. The upper and lower ring plates of the seat ring are made of S500Q-Z35 steel plate. The 23 fixed guide blades are made of S550Q steel plate. The transition plate and tongue plate are made of S500Q steel plate. The support ring is welded to the seat ring body at the construction site. The base ring is positioned with the stop mouth of the seat ring body and fastened with bolts. The seat ring needs to be machined to fit with the top cover, bottom ring and secondary bottom ring at the construction site, The fixed guide vanes are equipped with a simple valve guide copper bar, and the steel bar welding well is processed according to the size of the cylindrical valve. The screw holes of the top cover and the seat ring handle are made by reaming the iron thread with the reserved bottom hole in the factory.

12.2  Spiral case

The spiral case is an important water diversion component of the water turbine. Under the condition that the volute is designed without considering the combined force with concrete and with a pressure head of 2.87 MPa for pressure boosting, it adopts a full-circular cross-section and is directly hung and installed at the transition plate of the seat ring on the construction site. The material of the spiral case is B610CF steel plate. To meet the needs of on-site installation and adjustment, two compensating joints are provided on the spiral case. The inlet window of the compensating joint is 150mm, and the cutting allowance is provided. The extension section of the spiral case extends to 11m from the Y-axis line and is connected to the pressure pipe. The inner diameter of the inlet extension section is 7.74m. The net weight of the spiral case is approximately 520t.
The spiral case is buried by the local laying of cushion layer combination scheme. The cushion layer is designed according to the force transmission material. It is required that the cushion layer not only meets the required physical and mechanical performance indicators, but also has the characteristics of anti-aging, corrosion resistance, small plastic deformation and flame retardancy. After thorough analysis and research, polyurethane softwood is finally adopted as the outer covering cushion layer material of the spiral case.