Stability Analysis of Hydropower Stations With Complex Flow Patterns in the Tailrace Tunnel

Abstract

For some special tailrace tunnels in the hydropower stations, including the changing top-altitude tailrace tunnel and the tailrace tunnel with downstream reused flat-ceiling diversion tunnel, during normal operation and hydraulic transients, the flow patterns inside are relatively complex mainly including the free-surface pressurized flow and partial free flow if the tail water level is lower than the top elevation of tunnel’s outlet. These complex flow patterns have obvious effect on system’s stability, and can not be simulated accurately by the traditional models. Therefore, a characteristic implicit model is introduced to simulate these complex flow patterns for further stability analysis. In some special cases, the characteristic implicit model also fails to completely simulate the mixed free-surface pressurized flow in the flat-ceiling tailrace tunnel. A new method is presented based on both experimental research and numerical simulation, and then, system’s stability is analyzed by compared with traditional ordinary boundary condition. The results indicate that, with different simulation models for the complex water flow in the tailrace tunnel, system’s dynamic characteristic can be actually revealed with the consideration of the effect of complex flow patterns in the tailrace tunnel on system’s stability and regulation performance.

Numerical Modeling and Hydraulic Optimization of a Surge Tank Using Particle Swarm Optimization

“…The given generalized hydropower system is first analyzed numerically for gradual closure and opening of the valve respectively using the MOC. This method has been experimentally validated by several researchers in real world problems [6,11,14,[49][50][51]. In recent years, many model tests for the hydropower systems have been conducted in the laboratory, mainly including the hydraulic characteristics of the surge tank [49,50].…”

“…This method has been experimentally validated by several researchers in real world problems [6,11,14,[49][50][51]. In recent years, many model tests for the hydropower systems have been conducted in the laboratory, mainly including the hydraulic characteristics of the surge tank [49,50]. The models provided complete head loss coefficients for water flowing into or out of the surge tank, which revealed the complete hydraulic transient processes during load rejection or load acceptance, and also display great agreement with the results obtained by MOC.…”

A Review of the Hydraulic Transient and Dynamic Behavior of Hydropower Plants with Sloping Ceiling Tailrace Tunnels

“…Regarding Issue 5, it is discussed in References [39][40][41][42][43][44]. The stability of an HTGS directly relates to the stable operation of a hydropower plant.…”

“…The stability of an HTGS directly relates to the stable operation of a hydropower plant. In References [39][40][41][42][43][44], mathematical modeling, stability analysis methods, and stability performance regarding the stability of HTGSes with SCTTs were studied. Those research achievements are also systematic.…”

“…In Section 4, the numerical simulation of a transient process for HTGSes with SCTTs is described based on References [24,[33][34][35][36][37][38]. In Section 5, the stability of HTGSes with SCTTs is discussed based on References [39][40][41][42][43][44]. In Section 6, the transient process control of HTGSes with SCTTs is explained based on References [45][46][47][48][49][50][51][52].…”