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Design and Experiment on Aircraft Electromechanical Actuator Fan at Different Altitudes and Rotational Speeds
ISSN: 1946-3855, e-ISSN: 1946-3901
Published June 07, 2019 by SAE International in United States
Citation: Wu, W., Lin, Y., Gyasi, E., Kizito, J. et al., "Design and Experiment on Aircraft Electromechanical Actuator Fan at Different Altitudes and Rotational Speeds," SAE Int. J. Aerosp. 12(1):57-75, 2019, https://doi.org/10.4271/01-12-01-0003.
For electromechanical actuators (EMAs) and electronic devices cooling on aircraft, there is a need to study cooling fan performance at various altitudes from sea level to 12,000 m where the ambient pressure varies from 1 to 0.2 atm. As fan static pressure head is proportional to air density, the fan’s rotational speed has to be increased significantly to compensate for the low ambient pressure of 0.2 atm at the altitude of 12,000 m. To evaluate fan performance for EMA cooling, a high-rotational-speed, commercially available fan made by Ametek with a diameter of ~82 mm and ~3 m3/min zero-load open cooling flow rate when operating at 20,000 rpm was chosen as the baseline. According to fan scaling laws, this fan was expected to meet the cooling needs for an EMA when operating at 0.2 atm. Using a closed flow loop, the performance of the fan operating in the above ambient pressure range and at a rotational speed between 15,000 and 30,000 rpm was evaluated. Unexpectedly, at 0.2 atm, the Ametek fan was able to produce only about one-third of the static pressure head predicted by the fan scaling laws at a flow rate of 1 m3/min. The purpose of the present effort is to modify the Ametek design by using a standard optimization procedure with the aid of computational fluid dynamics (CFD). The final blade designs were manufactured by three-dimensional (3D) printing. The results and performances of these fan designs were confirmed experimentally which showed the new designs meet the cooling requirements by providing the necessary static pressure head and flow rates at the low ambient pressure of 0.2 atm. It is concluded that the new blade designs are able to yield a much better performance over the ranges of altitudes and rpm for aircraft EMA cooling. Thus, this study establishes a sound blade design method which can reduce the cost associated with expensive experimental investigation by using CFD tools.