چكيده به لاتين
Butterfly valves are widely used in industrial applications for startup and shutdown of flow and flow rate control. When using these valves, careful attention should be paid on the cavitation occurrence conditions, as a decisive factor in the design of the valve. The most important effect of cavitation are intense decline in life expectancy of the valve and even downstream piping. Biplane butterfly valve is one of the latest design of butterfly valves. This valve is used primarily for startup and shutdown of flow in which low pressure drop is the noteworthy feature of this design. In this thesis, water flow through the disks of this type of valve, with a 250 mm diameter, has been numerically evaluated using Ansys Fluent 16 software package. The flow has been considered steady state and incompressible and in order to evaluate the effects of cavitation, the simulation has been carried out using homogeneous mixed two phase model and full cavitation model. Furthermore in these valves, the distance between the two disks effects the valve’s pressure drop and consequently the cavitation it causes. Due to this, by considering different distances between the two disks and simulating each case, the finest distance has been selected. It has been proved that for a biplane butterfly valve having a nominal diameter, D, and a distance between the two disks, L, at a dimensionless fraction L/D=2/25, it has the lowest pressure drop and cavitation. Also, using results from experiments on this valve, and comparing it with this research’s results, the validity of numerical modeling is assured.
