The Performance of Two Butterfly Valves Mounted in Series

The results of an experimental investigation concerning the operating characteristics of two similar butterfly valves mounted in series are reported. Emphasis is given to the influence of the upstream valve disk angle, the downstream valve disk angle, the relative valve orientation, and the spacing between the valves. The dimensionless pressure drop, the mass flowrate coefficient, and the aerodynamic torque coefficient of each valve are used to characterize the system performance. The results show that the operating characteristics are strongly tied to the combined effect of the two valve disk angles. With noted exceptions, the valve disk orientation and spacing are secondary influences.