Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Investigation on Aerodynamic Characteristics and Aerodynamic Performance Optimization of an Axial
Flow Lift Fan
Hubing Chu, Lingbo Zhuge, Haipeng Zhang, Kejie Chen,Genquan Zhang
Marine Design & Research Institute of China
Shanghai, China

the layout space demands. And the increase of rotating speed means theaxial flow fans can provide higher pressure, making them better meetthe pressure needs of the hovercrafts with higher cushion pressures.

ABSTRACT
In order to improve the aerodynamic performance of an axial flow lift
fan applied on a hovercraft, so as to better meet its pressure needs, theaerodynamic optimization work of the fan is carried out in this paper
based on the parametric modeling, numerical simulation and model test
methods. The results obtained in the paper reveal the relationshipbetween the internal flow quality and aerodynamic performance of thefan, which is helpful for guiding lift fans design on hovercrafts.

The aerodynamic performances of centrifugal and axial flow fans areclosely related to their impellers design and the internal flow qualities.
In order to obtain higher aerodynamic efficiency of the centrifugal andaxial flow fans, scholars have carried out lots of research works. Basedon the neural network and multi-objective genetic algorithm methods,Kim(2011) optimized the aerodynamic performance of an axial flow
fan and increased its pressure and efficiency at the design point. Basedon numerical simulation, Lee, Ahuja and Hosangadi(2011) carried outoptimization of the impeller lines of a centrifugal fan, which improved
the pressurization capacity and aerodynamic efficiency of the fan.

KEY WORDS: Axial flow lift fan; aerodynamic characteristic;
aerodynamic performance optimization;
numerical simulation; model test.

parametricmodeling;

INTRODUCTION
Hovercraft is a kind of high performance ship that uses the lift fans tolift up the hull off the water, so as to reduce the hydrodynamic
resistance and gain higher speeds(Yun and Bliault, 2000). During thenavigation, the lift fans of the hovercraft need to blow the air with highpressure to the apron continuously, ensuring the apron forming and lift
height, which are the basis for the overall performance of the hovercraft.
Hence, the aerodynamic performances of the lift fans are closely related
to the overall performance of the hovercrafts(Ma and Wu, 2012).
The types of lift fans on most hovercrafts are mainly the centrifugal
fans and axial flow fans(Wu, 2001). The advantages of the centrifugal
fans are that their structural form are relatively simple and the pressurelines are generally smooth, which is favorable for limiting themovement response when the hovercrafts sail at terrible sea states.
However, due to the limitation of structural strength, the rotating speedof the impeller at its tip generally can’t exceed 130m/s if the material ofimpeller is aluminum. And the rotating speed is directly related to thepressurization capacity of the fan. Therefore, conventional centrifugal
fans can hardly satisfy the pressure requirements of the hovercrafts
with higher cushion pressures.
The structural characteristics of the axial flow fans allow them to bearhigher rotating speed more than 170m/s(Zhang, Yi and Feng, 2011).
Therefore, under the same pressure demands, the axial flow fans can be
designed smaller than the centrifugal fans, which can effectively save3647

In this paper, the predictions of aerodynamic characteristics andinternal flow qualities of the axial flow lift fan on a hovercraft are firstcarried out to reveal the cause of low pressure near its design point.
Then the aerodynamic performance optimization work is conducted toimprove the pressurization capacity and aerodynamic efficiency of thefan, so as to better meet the pressure needs of the hovercraft.

CONSISTS OF THE AXIAL FLOW LIFT FAN
The axial flow lift fan studied in this paper adopts the scheme of front
guide vane + impeller + rear guide vane. The angles of the front guidevanes are variable, so the flow rate and pressure of the fan can be
adjusted by setting different deflection angles of the front guide vanes,
which can better meet the flow rate and pressure requirements of thehovercraft at different sea states and weights. The impeller is a rotating
component, it increases the pressure of the flow around it byconvection the energy to the flow. The rear guide vanes are mainly
used to rectify the fan wake and recover part of the energy to improve
the aerodynamic efficiency. And in order to further improve the outletpressure and aerodynamic efficiency, this axial flow fan adopts themeridian acceleration design (Chen, Tan and Liang, 2006), making theflow around the impeller gradually increase. In addition, to improve thestall characteristic of the axial flow fan at small flow rates, a recess
vaned casing treatment is installed near the top of the impeller and front
guide vanes (Chen, Chu, Zhang and Li, 2019). The structural form andmain components of the whole fan are shown in Fig.1.