Torque Induced by a Butterfly Valve Carrying a Compressible Flow

This paper relates to a model study of the aerodynamic torque and flow characteristics of a butterfly valve. The tests were done with a compressed air supply capable of choking the 6 in valve model up to an opening of 70°. This was important as the prototype valves are to be used in a high speed wind tunnel system, where compressibility is significant. Two valve disc designs were tested, each with one flat and one convex face. The most significant result was that much higher closing moments were observed if the convex face was directed into the flow. This is explained qualitatively in terms of flow geometry and shock wave dynamics. Comparison of the results was made with a simple theoretical model developed by the author.