Evaluation of the losses of efficiency owing to inaccuracy of the governor system of Kaplan turbines

Abstract

The governor system of Kaplan turbines should provide a relationship between the runnerblade angle and opening of the gate apparatus so that a maximum turbine efficiency for a given load is obtained.The governor mechanism used for this purpose at all Soviet hydrostations provides a static relationship only between the position of the servomotors of the gate apparatus and the runner of the Kaplan turbines~The magnitude of inaccuracy of realizing the prescribed governor relationship is determined by three components:i. inaccuracy of the governor mechanism (ime); 2. inaccuracy of the drive mechanism of the gate apparatus (iga) ; 3. inaccuracy of the drive mechanism of the runner blades.In conformity with the block diagram (Fig. I), the general expression for inaccuracy of the governor system reduced to the runner-blade angle has the form:where ig s is the inaccuracy of the governor system; A, inaccuracy of manufacturing the cam of the governor system; is, inaccuracy caused by the dead zone of transmission from the servomotor of the guide apparatus 1 to the cam roller of the governor system 2; ky, coefficient of transmission of motion from servomotor 1 to roller 2; ih, inaccuracy caused by the dead zone of transmission of the system correcting the wedge of the governor system with respect to the head 3; kh, coefficient of transmission of the wedge-correcting systems with respect to the head 3; kg, coefficient of transmission from the roller of the governor system to the main slide valve or the runner 4; kfb, coefficient of transmission of feedback of the hydromechanical servo system of the runner 4, 5, 6; kr, coefficient of transmission from the servomotor of the runner to the blades; iz, inaccuracy caused by the dead zone in feedback 5 of the hydromechanical servo system of the runner; ifb is the inaccuracy caused by the dead zone in the feedback 6 of the hydromechanica! servo system of the runner; kgl, coefficient of transmission of the governor linkage, determining the relationship between the runner-blade angle and opening of the gate apparatus; iy and i~ , inaccuracies of the drive of the gate apparatus; iy and i , inaccuracies of the drive of the gate apparatus 8 and runner blades 7; kry and kr~ , coefficients of transmission between the position of the gate apparatus and runner blades and active power.The inaccuracy of the governor mechanism (ime) is represented by the expression enclosed in brackets.St consists of two components:i. inaccuracy of the profile of the cam and its drive;2. inaccuracy of the hydromechanical servo system, consisting of a slide-valve system, runner servomotor, and direct feedback.To provide the required accuracy, of the indicated quantities the variable ones are, as a rule, the coefficients of transmission from the servomotor of the gate apparatus to the roller and from the latter to the main slide valve of the runner, and also the inaccuracy caused by the dead zone of the runner servomotor i z.At hydrostations that have been operating for a long time (Narva, Kakhovka, etc.) overlaps...