Design of a Double-Suction Fan Stage

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Introduction


Design Targets

Analysis of an existing double-suction fan stage including inlet ducts, connecting channels, impeller and volute and redesign of fan impeller for improved aerodynamic efficiency.

Deliverables

Redesigned impeller geometry.

Impact

The stage efficiency was improved by up to 4 points.

Our client is one of the leading turbomachinery manufacturers. In this project they asked ADT to perform a complete stage analysis of a double-suction fan stage, then redesign the fan impeller using the inverse design code TURBOdesign1 in order to improve the aerodynamic performance.

The impeller and casing geometry of the existing double-suction fan was provided by our client. In the first part of the project ADT performed a complete CFD analysis of the fan stage in order to obtain a clear understanding of the flow field in the double-suction fan stage; including the suction ducts, fan impeller and exhaust volutes therefore identifying major sources of aerodynamic loss which could be improved in the redesign. A parametric study was performed using TURBOdesign1 in order to find the effects of the design parameters on the fan performance.

 

2D Streamline flow in the double suction fan stage
2D Streamline flow in the double suction fan stage

 

Stage analysis of the double-suction fan with the final redesigned impeller showed significant improvement in efficiency.

In the second part of the project, a final design of the impeller fan was completed for optimum aerodynamic performance at design and off-design conditions while meeting the other geometrical and mechanical constraints as specified by the client.

The geometrical constraints were to reduce manufacturing costs and included a constant thickness (airfoil shape was not acceptable), straight filament blade geometry and low to moderate stacking shape. These constraints could be easily satisfied in TURBOdesign1 through specification of appropriate blade thickness and stacking condition in the code.

Stage analysis of the double-suction fan with the final redesigned impeller showed significant improvement in the efficiency (about 4 points at design point) and improved stall performance as shown below.

Normalised total to total efficiency of the fan stage
Normalised total to total efficiency of the fan stage

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