Propeller Design and Performance Evaluation with Partially Prescribed Velocity Distribution

Abstract

This research aims to provide an iterative propeller design approach for distributed electric propulsion (eDEP) systems with the example of improved cooling characteristics. This is achieved due to increased outflow velocity near the hub where a heat exchanger is placed. For this purpose, the in-house tool RAPID (Research Algorithm for Propeller Identification and Design) is presented. Its propeller design algorithm is based on the Blade Element Momentum Theory with Betz’ optimal displacement velocity ratio. Patterson’s approach for prescribed axial velocities is used for the modified cooling characteristics. The propeller design with modified near-root velocity distribution is presented for an eDEP propulsion unit of a 50 pax regional aircraft class. In the following, the on- and off-design performance of the design is shown. Subsequently, the improved cooling performance is discussed by applying an analytical fin heat exchanger model in the propeller outflow. It can be shown that the modifications result in a significant reduction in the required heat exchanger size of up to 3.86%. At the same time, the impact on propeller efficiency remains below 0.44% at take-off while it increases up to -2.41% at cruise.