An Extended Analytical and Numerical Design Method With Applications of Radial Fans

Abstract

The use of high speed radial impellers is very common in fans for industrial application. It is very common also to manufacture the radial impellers for these fans with circular arc blades. The design process is also almost always based on former impeller series and experimental data available. In this work a method is presented to improve the efficiency of radial impellers with a combined analytical and numerical method. This method is based on a new extended analytical formulation of the flow in radial impellers allowing optimizing efficiency in design stage. The blade shapes are computed with an inverse method. The design is then validated by means of CFD computation. Finally a prototype was built and measurements were carried out in a test rig. It is shown also that the design method delivered very good predictions leading to an efficiency increase of 13% of efficiency and a maximum flow rate increase of 11% absolute. The design point was also met. It is also shown that the numerical computations and measurements are in good agreement. An analysis of the CFD results is also presented, giving insight in the substantial flow information inside the old and the new impeller. The method presented is a combined analytical and numerical method suited to design high efficiency radial impellers without the need of a previous impeller series or knowledge of experimental data.

A theoretical derivation of the Cordier diagram for turbomachines

“…A second way to validate the theory is performing CFD computations. How well the design predictions fit to the CFD computations has been already done by the authors and presented in Epple [5] and Epple et al [13,14]. Here, it was confirmed for several practical cases that the design process and hence these simplified formulae, which do not take into account the viscosity, indeed capture the essential physics of the process, failing to lead to the exact value.…”