Abstract

The characteristics of the downstream turbulent kinetic energy distribution were analyzed by large eddy simulation (LES) according to the operating load of a three-dimensional small-size helical axial fan (SSHAF). In an SSHAF, the curve of static pressure performance for each flow coefficient does not include an unstable region representing stall, but increases with increasing blade length. The peak value of the axial mean velocity component developed around the tip of the blade exists regardless of the operating load; it does not spread significantly to the periphery even if the operating load increases. Therefore, axial flow exists at all operating loads. As a result, regardless of the downstream distance, the turbulent kinetic energy generated at the tip of the blade is much smaller than that of the small-size axial fan (SSAF) at full flowrate; however, such energy develops largely as the operating load increases. Since this SSHAF is predicted to bring about a noise reduction effect at full flowrate, additional research is needed to confirm the noise effect by applying this SSHAF to the propulsion device of a ship or submarine that values noise.

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