Impact of the Tip Clearance and the Inflow Nozzle Shape on the Performance of Low-Pressure Axial Fans
Fritsche M, Epple P, Delgado A (2023)
Publication Language: English
Publication Type: Conference contribution
Publication year: 2023
Publisher: American Society of Mechanical Engineers (ASME)
Series: ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Pages Range: V008T10A006
Conference Proceedings Title: Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 8: Fluids Engineering; Heat Transfer and Thermal Engineering
Event location: Columbus, OH
ISBN: 9780791886700
Abstract
Low-pressure axial fans have a very wide range of applications in the field of heating, ventilation and air conditioning as well as refrigeration (HVAC&R). Due to stricter legal requirements, increasingly higher fan efficiencies are required. Due to legal regulations, more efficient machines are becoming increasingly important. A small gap, the so-called tip clearance, is necessary between the rotating impeller and the stationary shroud due to manufacturing tolerances and structural-mechanical expansion as well as thermal expansion. However, this tip clearance has a strong impact on the performance of the fan. Due to the gap between the blade tip and the shroud wall, a circulation volume flow rate occurs depending on the operating point. This can have a strong influence on the inflow condition, for instance a standing vortex can develop at lower volume flow rates in front of the impeller at the tip region. Overall, this affects the operating behavior and the performance characteristics, i.e. the integral pressure characteristics as well as the efficiency characteristics. In the present investigation, an axial impeller was designed and optimized for this purpose. The impeller blades were designed as flat sheet metal blades with a constant thickness. This axial impeller was modeled with ANSYS Blade Modeler and simulated with the commercial CFD solver ANSYS CFX. In the first simulation study, the tip clearance was varied and analyzed. As a reference case the impeller was simulated also with no gap. Since the tip clearance effectively makes the blade shorter, the influence of the shortened blades was compensated considering the similarity theory of fans. Second, the shape of the inflow nozzle, i.e. the radius and the length, was varied, simulated and evaluated. In order to determine the influence of the tip clearance and the shape of the inflow nozzle, the integral characteristics such as the pressure characteristic and the efficiency characteristic were compared. In addition, the flow field around the blade tip as well as in the inflow nozzle were analyzed and areas of flow detachment were evaluated. For the inflow nozzle the meridian and circumferential velocity was evaluated and compared in different sections in the inflow nozzle. Finally, the study showed that for the present application of the low-pressure axial fan, the tip clearance has a significant impact on the performance of the fan. An optimal compromise between manufacturing costs and acceptable losses due to tip clearance was sought. The method and the results are presented and discussed in detail.
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APA:
Fritsche, M., Epple, P., & Delgado, A. (2022). Impact of the Tip Clearance and the Inflow Nozzle Shape on the Performance of Low-Pressure Axial Fans. In Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 8: Fluids Engineering; Heat Transfer and Thermal Engineering (pp. V008T10A006). Columbus, OH, US: American Society of Mechanical Engineers (ASME).
MLA:
Fritsche, Manuel, Philipp Epple, and Antonio Delgado. "Impact of the Tip Clearance and the Inflow Nozzle Shape on the Performance of Low-Pressure Axial Fans." Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition, IMECE 2022, Columbus, OH American Society of Mechanical Engineers (ASME), 2022. V008T10A006.
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