Flow Analysis And Security Assessment Research Of Load Variation Transient Process For Hydraulic Unit

With the rapid development of national economy, the proportion of hydroelectric power in national electric energy will increase further as it is a high quality and non-pollution clean energy. The development of hydropower industry will keep growing in the future.In the operation of hydraulic units, it is hard to avoid load variation conditions which will cause the hydraulic transient process of diversion system and make the unit and system in poor operation state. Therefore, the flow analysis and security assessment research of load variation transient process is of great significance to the safe and stable operation for hydropower station.But the testing of this process has the characteristic of high risk, long period and low reliability. Improper handling would lead to some major accidents and endanger the personal safety. So, nowadays numerical simulation methods are widely used to analyze the change rule of dynamic parameters in transient process. This method can provide basis reference for security assessment of hydropower stations.The research object is mixed-flow hydraulic unit. And this paper has proposed a new kind of numerical algorithm called SE-ICNA based on internal characteristic to conduct the fluid analysis and security assessment in load variation transient process. Establish the mathematical security assessment models in transient process through fluid analysis, which are included three parts:pipe flow characteristic differential equation, turbine characteristic equation and rotational dynamics principle equation. Then assess the security of hydropower stations within the scope of different water levels and confirm the applicability and reliability of SE-ICNA algorithm. At last, analyze the fluid flow with CFD method under normal operation condition. Study the steady and unsteady simulation of whole flow passage respectively and analyze the pressure pulsation to complete the security assessment.Through this study, the phenomenon is found that SE-ICNA evaluation method shows a good computing performance in low water level and large load shedding conditions.This method can implement the security assessment of hydraulic unit in load variation transient process and has good engineering practice significance.