According to the 12th Five-Year Planning, there were about 30 giant hydropower projects with each installed capacity of over 3,000MW and total installed capacity of 196,875MW, accounting for more than 1/3 of the national hydropower potential. Giant hydropower projects possess the following significant features: remarkable comprehensive benefits of power generation, flood control, irrigation, water supply, navigation and tourism; complex project layout of flood discharge structures (in dam body or at river bank), water diversion structures for power generation, construction diversion structures, navigation structures, and fish passages; and prominent hydraulic problems of high water head, large flow and flood discharge, narrow valley and complex geological conditions for most projects locate in western alpine canyon regions. Related hydraulic problems of hydropower engineering construction were studied in many special subjects in the past. For example, there were 3-5 integral hydraulic physical models and more physical models of single unit. Hence, the existing problems include the results of various studies lack the overall and comprehensive experimental validation and the optimum overall effects may not be achieved while the best results could be obtained in special subject studies. In order to solve the problem of energy dissipation of flood discharge of giant hydropower projects, the research project put forward a new method of large scale hydraulic modelling, by which the rationality of pivot general layout, reliability of discharge energy dissipation design, hydraulic coordination of respective structures and security of discharge atomization and protection design of downstream river course were studied.
1. Major Innovative Achievements
1.1 A large scale hydraulic model test method has been innovatively proposed. A rational model scale was set out based on the similarity criterion of each single item, and then an integral hydraulic model was successfully developed with the largest scale in the world.
1.2 For the world's highest arch dam, the flood discharge proportion of dam body and spillway tunnels has been optimized via an integral hydraulic model with a scale of 1:50. The combination of discharge atomization and energy dissipation has been innovatively proposed for the energy dissipation pattern of non-collision flood discharge of the Jinping First-Cascade Hydropower Project suitable for the engineering characteristics of narrow valley and complex geological conditions of the bank slopes with advantages of small atomization and safe structure, which dramatically reduced the impact of discharge atomization on the stability of slopes of over 1,000 meters high and safeguarded the engineering safety operation.
1.3 With the help of type optimization of orifices and deep holes in the integral hydraulic model with a scale of 1:50, the basic symmetry of discharge water tongue droppoints has been realized under the arrangement of the asymmetric arch dam, solving the technical difficulty that the hydrodynamic pressure of the water plunge pool is hard to meet the standard requirements for extra-large discharge of the Baihetan Hydropower Station. Respective measures like fine simulation of hydropower station, inlets and outlets of discharge tunnels and their boundary conditions have been taken for the integrated optimization effects of engineering layout.
1.4 With the help of an integral hydraulic model with a scale of 1:40, the flow regime and vortex structural characteristics of 3 dimensional multi-layer and multi-strand jet flow of energy dissipation by hydraulic jump have been disclosed, and the hydrodynamic load proposed has provided an important scientific basis for the safety design of discharge energy dissipation structure in the Xiangjiaba Hydropower Station. The scheduling mode of orifices and middle holes proposed has reduced the vibration induced by discharge, solving the technical difficulty of discharge energy dissipation of the Xiangjiaba Hydropower Station with the largest energy dissipation by hydraulic jump.
1.5 The largest vacuum tank both at home and abroad has been transformed. For the first time, the cavitation of spillway orifices and stilling pool has been carried out, verifying the security of flood discharge through the dam, and the measures to improve the severe cavitation erosion of built dam surface raised. The invented high velocity and high pressure test device with a scale of 1:1 was used to solve the anti-cavitation of materials in the current of the ultra-high velocity of 50m/s.
2. Academic Outputs and Third Party Evaluation
15 utility patents have been authorized or under processing for the research project. The large scale integral hydraulic model and test method of vacuum tank have been applied in the Jinping First-Cascade Hydropower Project, Xiangjiaba Hydropower Project and Baihetan Hydropower Project, better solving a series of technical difficulties of giant hydropower stations and realizing the goals of engineering comprehensive optimization. The research findings won the Special Prize of NHRI 2015 Science and Technology Progress Award.
3. Application Promotion and Comprehensive Benefits
The research findings have been directly applied in the hydropower engineering, such as the Xiangjiaba Hydropower Station, the Baihetan Hydropower Station, the Jinping First-Cascade Hydropower Station, the Ahai Hydropower Station, the Fengman Hydropower Station, etc. A 1250px aerator has been added on the dam surface for the transformation of the Ahai Hydropower Station, eliminating the dam surface cavitation and guaranteeing the dam safety. The experimental results of the large scale model of the Xiangjiaba Hydropower Station have removed the worries about discharge energy dissipation safety over many years held by the insiders. The inverse tests of large scale model have played an important role in vibration reduction. With an optimized dispatching mode, the discharge over the dam reached 8,000-11,000m3/s in 2013, increased by 15%-55% of that in 2012, but the field vibration amplitude was reduced by 30%-70%. Compared with the traditional collision energy dissipation, the initiative non-collision energy dissipation applied in the Jinping First-Cascade Hydropower Station has reduced the atomization longitudinal length by 300m, elevation by 30m and rainfall intensity by 40%. The experimental results of the large scale model of the Baihetan Hydropower Station have reduced the hydrodynamic impact pressure of water column from the original design value of 22m to 12m, ensuring the safety of water cushion pond. Thanks to the atomization reduction of the Jinping First-Cascade Hydropower Station, the protection of high slopes has been reduced, resulting in the direct economic benefit of over 100 million Yuan.
