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► VOLUTE  Diffuser
The geometry of the outlet diffuser (inlet diffuser for turbines) can be designed and calculated in this dialog box.
In general, 3 basic shapes are available:
Tangential diffuser 

Radial diffuser 

Splinediffuser 
The tangential diffuser is easier to manufacture, the radial diffuser has the advantage of minimizing tangential forces. The spline diffuser is similar to the radial but with extended flexibility.
Tangential diffuser
For the tangential diffuser the eccentricity can be specified:
The right side is parallel to the center line (perpendicular to the last spiral cross section). 

The diffuser opens to both sides (default). 

The left side is parallel to the center line (perpendicular to the last spiral cross section). 

The eccentricity can be specified manually. 
Radial diffuser
In the case of a radial diffuser, the angle ε between the outlet branch and the line connecting impellercenter and outlet branch center can be selected.
Spline diffuser
For the Splinediffuser the angle φ between connecting line impellercenter ↔ outlet branch center and diffuser start section has to be defined. Points 0 and 4 are start and endpoint of the middle line on the inlet and outlet cross section, point 2 is fixed by the intersection of appropriate perpendiculars of these sections. Position of points 1 and 3 influence the curve shape of the middle line.
By clicking on Default, you can return to the default values for the diffuser geometry.
The extension of the diffuser can be defined in panel Dimensions. Parameters in the x,yplane can be specified, as well as a rake of the diffuser in zdirection.
For all diffuser shapes the extension is defined by the diffuser height H, which is the distance from the diffuser outlet to a parallel line through the center point. The distance C from the Hline to the center point is displayed for information, both in the diagram and numerical in the Information panel. 
Additionally the starting position of the diffuser is defined by the angle φ0, whereas 0° is horizontal right. The whole volute can be rotated by this value. By using the button Vertical outflow direction the volute can be rotated for vertical direction of the pressure joint.
The diffuser bending in zdirection is described by the parameters shown in the sketch.
There exist 2 straight segments 1, 3 and a circular segment 2. The lengths L1, L2 and L3 are specified as percentage.
The curvature is defined by the radius R, the direction by the angle α.
The zbend is illustrated in the diagram by a green center line.
The end crosssection of the diffuser can be either round or rectangular. The diameter D can be directly defined or selected from standard tables. In the case of a rectangular end crosssection the height H and width B can be chosen.
The position of end shape specifies the percentage position along the diffuser, where the type of end cross section is reached (default = 100%). To reach certain cross section areas a scaling of those sections is necessary. Instead of just scaling uniformly in both directions (z and r) a scaling ratio (z/r growth) can be defined.
The choice of the area progression influences the scaling of the morphed cross sections.
Linear blending 
The morph between two different cross sections is linear which results in an quadratic area progression. (unscaled) 
Linear area 
The size of the morphed cross sections is scaled to achieve a linear area progression. 
Quadratic area 
The size of the morphed cross sections is scaled to achieve a quadratic progression from the diffuser inlet to the end shape position. The progression to diffuser outlet is linear again. 
Custom area 
The size of the morphed cross sections is scaled with respect to a Beziér curve. 
The position of splitter end defined the relative length of the splitter inside the diffuser.