The quest for lighter and shorter propulsion systems has led to the reduction of axial compressor and fan blade chord-lengths. Theoretical and experimental results show that the geometrical aspect-ratio criterion significantly affects the overall performance of axial flow compressors and fans. In conducting this review, it was found that the experimental results differ from one literature source to another. Highlighting that the way in which blade aspect ratio affects the performance of axial flow compressors and fans is still not fully understood. Nonetheless, the reviewed literature has still proven valuable for compressor and fan design. This paper focuses on creating a review of the available literature relating to how low aspect ratio blades may affect the performance of electrical axial compressors and fans.

The aim of this paper is to provide a method of estimating torque versus speed characteristics of single and dual-stage electrically powered Rim Driven Fans which are intended for aircraft propulsion. The methodology is based on the well-known Euler equation which considers the change in angular momentum of the air as it passes through the fan rotors. A derivation of the useful and versatile Specific Work parameter (Y) is provided along with its important relationship with the fan Work Co-efficient (ψ) and an explanation of the relevance of the Fan Flow Co-efficient () in determining the flow of air through the RDF device. An equation is derived which relates the fan torque to its rotational speed and a specimen calculation of a 200 mm inlet diameter RDF has been provided. Electrical performance graphs, generated with Motor-CAD LAB software, are included to illustrate an example of a suitably optimised RDF motor circuit. Finally, a thrust performance comparison is made between a theoretical dual-stage RDF and a commercially available fan-jet engine. It is demonstrated that the dual-stage RDF technology could offer a viable solution to power high-speed medium and large commercial transport aircraft, making them particularly suited to distributed thrust system architectures and blendedwing-body aircraft designs.

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This paper investigates the slotless winding characteristics of motors intended for aircraft electrical propulsion (AEP), together with a preliminary design study of a winding model derived from a Faulhaber configuration. Geometrical relationships and magnetic requirements driving the design, such as the width of each phase coil side, the skew angle, and the winding arrangement, are analysed. Finally, electromagnetic (EM) simulations were conducted to study the electromagnetic performance of the Faulhaber model and the influence of the stator conductor skewness. Upon analysis of the results, it is found that the skew angle should remain low to assure efficiency, while it should also be great enough to satisfy the geometric and magnetic requirements. In conclusion, the paper proposes a hybrid slotless winding configuration based on the Faulhaber structure, which is a trade-off between efficiency and end-winding length for a motor powering a rim driven fan.