CFD Optimization of a Fan for Industrial Application

D2 - Theoretical & Numerical Methods for Centrifugal Fans

Energy consumption and operating ranges in industrial application of fans have grown in importance in the latest years and now, in order to be attractive for the market, the product must fulfill a number of requirements like:
(i) good efficiency inside all the operative range,
(ii) higher maximum flow rate,
(iii) minimum manufacturing and maintenance costs.
The design procedure for centrifugal fans with backward curved blades is well documented and experimental analysis had confirmed its reliability but in most cases these methods don't match the installation and process requirements (such as space constrains, electrical power limits, national and international directives in the field of health and safety). So the Computational Fluid Dynamic (CFD) can assist the design and optimization procedures in order to discover internal flow issues, to help conceiving new solutions and reducing the prototyping and experimental activity and in general the time to market.
In this article a CFD study, regarding three industrial centrifugal fans for low, medium and high pressure applications, will be carried out showing how the impact of design optimization on the meridional passage and blade shape changes according to the specific speed.
The meridional passage shape has the most influence in the low pressure fan because of the high passage area variation between the aspiration and the leading edge. The blade angle distribution has direct impact on the blade loading in all the three fans: increasing the blade angle means increasing the total pressure increase, the power consumption and in most cases also the efficiency. The increase in efficiency depends on the increase of the blade loading with same overall losses but often is not a suitable solution because of the consequent power consumption increase.
Experimental campaign on a limited number of the modified fans confirmed the overall design guidelines deducted from the CFD analysis allowing the the fulfillment of different demands such as energy saving, process and market requirements.