CFD Simulations to Predict the Energy Efficiency of an Axial Fan for Various Casing Configurations

D3 - Design and Optimisation

The implementation of the Energy Related Products Regulation applied to fans (ErP Lot 11), which is now entered into force, fixes minimum energy efficiency requirements for fans from 1 January 2013. The target energy efficiency is based on the electrical input power of the motor at the best efficiency point of the fan, either static or total overall efficiency according to the installation category.
Fan manufacturers may have difficulty to comply with this European regulation, which forces them to improve some of their fans. To help manufacturers in this task, the objective of this paper is to assess the ability of a CFD numerical method (stationary RANS equations with standard k- turbulence model) to predict the fan impeller efficiency with reasonable accuracy.
The study has been carried out on a low-pressure axial flow fan of 630-mm diameter, 12 blades, hub/tip ratio of 0.33, running at 1450 rpm. Various casing configurations such as long or short casing, with or without inlet bellmouth, have been studied with the same impeller design. The influence of the installation category A or D has also been examined in this work. The use of flow simulations is indeed beneficial to predict the performance of variants of an initial design as it is generally quicker and less expensive than making tests on various test set-ups, especially when the number of variants is important.
The CFD calculations are compared to the measured performance and efficiency curves for all the tested configurations. The agreement between the numerical and experimental results is satisfactory for the purpose of the present work. Detailed information on the simulations and experiment will be provided in the paper.