The bio-hill chart of a Kaplan turbine

Feasibility study for test rig assessments of fish passage conditions in a Kaplan turbine

“…P* decreased further during the short passage time through the guide vanes, with greater rates of pressure change observed towards the runner region. The entry to the runner (T2) was inferred based on the CFD-based outcome that minimum P* values (the nadir pressure for each passage) correlated well with a position below the runner blades [ 27 ]. Therefore, T2 was calculated as the time where nadir pressure occurred (from the sensor signal) minus the average residence time (from CFD-based streamlines) elapsed between the entrance to the runner region and the occurrence of the minimum (nadir) pressure.…”

“…This premise emerged from the assumption that flow conditions at BEP are hydraulically optimal, which in turn minimizes the risks to fish mortality associated with disrupted flow velocities patterns, high turbulent conditions, and extremely low pressures. Such premise was put to test [ 27 ] by estimating collision- and pressure-related risks of mortality at 26 operating points that were nearly uniformly distributed over the operating range of a large Kaplan turbine (runner diameter of 8.5 m, head range of 22 m–35 m, and discharge range of 250–800 m 3 /s). In relation to nadir pressure, passage survival of juvenile salmonids was higher in only four of the twenty-six examined operating points than at BEP.…”

“…2 present the values of n ED and Q ED over the entire operating range in a normalized manner (n ED * and Q ED *) with respect to the corresponding values at the best operating point (BEP). The tested operating points (OP1 and OP2) were defined near the cavitating region at high discharge because various studies have indicated that high discharges tend to give rise to hazardous pressures [ 27 ]. Furthermore, high discharges allowed for greater guide vane openings which minimized the likelihood that the SF Mini, which are relatively big for the guide vane passage gaps, were retained during distributor passage.…”