Fan: Series Fans, MRF Method

Series Fans CFD Simulation Using MRF Method in ANSYS Fluent

Introduction

This project investigates the steady-state airflow behavior between two 3-bladed series fans rotating at an angular velocity of 300 rpm using ANSYS Fluent, employing the Multiple Reference Frame (MRF) method to capture the rotational effects of the fan blades on the surrounding flow field.

Geometry and Mesh

The three-dimensional geometry of the dual fan assembly was designed in SpaceClaim, and the domain was meshed using ANSYS Meshing, resulting in a total element count of 1,914,000.

Methodology

The rotation of the fans generates air suction at the inlet boundary, with a volumetric flow rate of 2.95755 m³/s. Along the domain centerline, air velocity reaches values up to 25 m/s, while the maximum velocity in the entire domain, 47.05 m/s, occurs downstream of the first fan. Turbulent flow behavior throughout the domain was resolved using the RNG k-epsilon turbulence model.

Results and Conclusion

Two- and three-dimensional contours of pressure, velocity, velocity vectors, and streamlines were generated to characterize the flow field. Based on the calculated Fluent data, the air mass flow rate at the inlet equals 3.62019 kg/s. A comparison of the pressure drop across each fan reveals that the first fan produces a pressure drop roughly twice that of the second fan, at 500 Pa and 230 Pa, respectively. Negative gauge pressure is observed downstream of both fans, with the region downstream of the first fan reaching a value five times lower than that of the second fan, at -500 Pa compared to -100 Pa. Consistent with the higher pressure drop, the velocity magnitude downstream of the first fan is also higher, at 28 m/s, compared to 12 m/s downstream of the second fan, confirming that the first fan experiences a more significant aerodynamic loading within the series configuration.