TABLE OF CONTENTS Various fluids such as air and liquid are used as an operating fluid in a blower, a compressor, and a pump. The shape of flow channel often determines the efficiency of these machines. In this chapter, the flow structures in a diffuser and the channel with a butterfly valve are examined by using FLOTRAN which is an assistant program of ANSYS. A diffuser is usually used for increasing the static pressure by reducing the fluid velocity and the diffuser can be easily found in a centrifugal pump as shown in Figure 5.1.
Analyze the flow structure of an axisymmetric conical diffuser with diffuser angle 2 ? = 6 and expansion ratio = 4 as shown in Figure 5.2.
Shape of the flow channel:
Diffuser shape is axisymmetric and conical, diffuser angle 2 ? = 6 , expansion ratio = 4.
Diameter of entrance ofthe diffuser: D E = 0.2 m.
Length of straight channel for entrance: 4.5 D E.
Length of diffuser region: 9.55 D E.
Length of straight channel for exit: 50.0 D E.
Operating fluid: Air (300 K)
Flow field: Turbulence
Velocity at the entrance: 20 m/s
Reynoldsnumber: 2.54 10 5 (assumed to set the diameter ofthe diffuser entrance to a representative length)
Boundary conditions:
Velocities in all directions are zero on...
