PEAK TORQUE CHARACTERISTICS OF BUTTERFLY VALVES.

The moment distributions resulting from the disk surface static pressure measurements for the two-dimensional flat plate model produce torque characteristics representative of the general torque characteristics of three-dimensional prototype butterfly valves. At a fully open position, the net torque is approximately zero. In addition, at large angles the net torque also approaches zero. The net torque increases to a maximum at some intermediate angle which appears to be associated with flow separation and reattachment on the downstream valve disk surface.