Volutes have a major effect on the performance of radial compressor, pumps, and turbines. They can affect the stage efficiency, surge and choke flow in compressors, vibration and unsteadiness in pumps. However, they are generally designed by using 1D methods based on conservation of mass and angular momentum.
There is a lot of evidence that the flow field (static pressure, radial and tangential velocity) at the inlet of the volute can vary strongly in the circumferential direction especially at higher design flow conditions. By using 1D methods it's difficult to design the volute to account for the circumferential variation in flow. Another major problem with design optimization of volutes is that the process of creating the CAD geometry from the 2D sections is a manual process which can take considerable work and hence difficult to create various geometries for design optimization.
TURBOdesign Volute
TURBOdesign Volute tries to address both of the above issues. Firstly, it's a 2D inverse design approach. In this method, the volute geometry is designed for a given distribution of circumferentially varying radial and tangential velocity at the volute centerline inlet. So the resulting area variation can be directly obtained from the actual flow field at the inlet of the volute. This approach can then help to remove the need for trial and error in the design of volutes and can help to optimize the volute area variation. Furthermore, TURBOdesign Volute can generate directly a good quality IGES file that can be mesh immediately.
Application of TURBOdesign Volute can result in significant reduction in volute losses as shown in the example below for a pump stage with RPM of 1760, Head of 29.7 m and Flow rate 0.1m3/s.
Comparison of the flow field in a volute designed by TURBOdesign Volute versus conventional design at different sections around the volute circumference.
Overhung Volutes
Originally TURBOdesign Volute was released for external symmetric and asymmetric volutes. However, in many applications such as turbochargers, overhung volutes are used to reduce total package size of the compressor. In TURBOdesign Suite 6.2, the functionality to design overhung volutes by using TURBOdesign Volute will be introduced and an example of this will be presented during the webinar on 17th of November.
An example of an asymmetric external (red) versus overhung (grey) volute for the same compressor stage.
Mehrdad Zangeneh
Mehrdad Zangeneh is Founder and Managing Director of Advanced Design Technology and professor of Thermofluids at University College London.
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