Experimental investigation of an adjustable guide vane system in a Francis turbine draft tube at part load operation

Hydraulic turbines are increasingly used to regulate the electrical grid. They thus have operate more often at off-design conditions where instabilities may develop leading large pressure pulsations decreasing life of machines. In present study, an adjustable guide vane system in draft tube a single regulated hydraulic turbine is developed. The aim mitigate when operates part load operational regimes without significantly compromising efficiency turbine. system, named DTGV, composed three vanes. Each vanes comprise two individual hydrofoils. upper hydrofoil can rotate around axis up ±45°, and lower fixed. Therefore, adjustable. rotating vortex rope mitigation was investigated part-load 12 m head, a) Q/QBEP = 0.59, b) 0.71. results indicate that DTGV mitigates pulsations, thereby improving flexible operation best outcome for 0 GV configuration both operating conditions. effects better condition approaches BEP, mode tends go towards runner frequency (f/f0 1). found be marginally affected by operations improved point (Q/QBEP 1) high 1.21.