Session: 01-08 Propellers and Open Rotors I

Paper Number: 151812

Development of a Wind Tunnel Dynamometer Assembly for Evaluating Unmanned Aircraft Co-Axial Propeller Performance 

Coaxial propellers, with their innovative design comprising of two superimposed propellers on top of each other, offer significant advantage in terms of high speed capability, maneuverability, and load-carrying capability. These systems hold particular promise in the field of unmanned aerial vehicles (UAVs), where space and performance efficiency are critical.   Despite the growing interest in co-axial propeller systems, the precise aerodynamic behavior of these configurations remains under-researched, particularly in terms of the complex interactions between the front and rear propellers. Prior studies have observed significant variations in thrust and power between the front and rear propellers, although these phenomena are not investigated in detail. This study aims to address this through the development of a specialized dynamometer assembly, housed in a subsonic wind tunnel, for systematic performance evaluation of co-axial propellers. One of the key features of the developed test-rig is independent control of each propeller of a coaxial system as well as independent measurement of thrust, torque, and power for each propeller. The developed dynamometer assembly features a co-axial shaft configuration, where a hollow shaft and a solid shaft work in tandem. The hollow shaft, with an inner diameter of 10 mm and an outer diameter of 14 mm, rotates the rear propeller, while the solid shaft, with a diameter of 5 mm, rotates the front propeller. The hollow shaft is connected to a through-hole motor and sensor system, while the solid shaft passes through this hollow shaft and the through-hole motor-sensor system. To capture precise aerodynamic loads, three types of sensors are employed to measure thrust and torque. The front propeller’s thrust is measured using a donut through-hole strain-gauge based load cell, and the torque of the front propeller is measured using another through-hole sensor. For the rear propeller, a bi-axial sensor has been placed at the back of the rear motor to measure both thrust and torque. The experimental setup is housed in a 3-foot by 3-foot subsonic wind tunnel, providing a controlled environment for testing. 

 

In the next phase, the  effects of various design parameters on the performance of the front and rear propellers, along with their mutual aerodynamic interference, will be investigated. To conduct this analysis, propellers with differing configurations and blade geometries will be tested at varying axial distances. For instance, propellers with various blade counts, solidity, diameter, pitch, blade twist and taper, while operating over a diverse range of rotational speed will be tested. These experiments will reveal the nature of coaxial interference between front and rear propellers in terms of thrust production and power consumption and the effect of several design parameters on these coaxial interference. The proposed study will be critical to understand the nature of aerodynamic interference in coaxial propeller system which could lead to more efficient propulsion designs, reducing energy consumption and enhancing the flight performance of Unmanned Aerial Systems (UAS). Future work will involve development of a physics-informed machine learning (PIML) algorithm that can utilize this data to accurately predict performance of a coaxial propeller.

Presenting Author: Samin Yaser Ahmed Oklahoma State University

Presenting Author Biography: Samin Yaser Ahmed is pursuing a Master of Science in Mechanical & Aerospace Engineering at Oklahoma State University, specializing in the development of physics-informed machine learning models for co-axial rotor systems. He earned his Bachelor of Science in Aeronautical Engineering from the Military Institute of Science and Technology, Bangladesh. Samin has hands-on experience in designing and constructing instrumented rotor test stands and conducting numerical analysis to improve rotor performance. He also contributed to optimizing propulsion systems during his time at Horyzn, TUM, Munich.

Samin’s technical skills include proficiency in Python, MATLAB, and SolidWorks. He has co-authored publications on helicopter rotor design and Kevlar-Epoxy composite laminates. Additionally, he actively participates in leadership roles, including serving as General Secretary of the Bangladesh Student Association at OSU.

Authors:

Samin Yaser Ahmed Oklahoma State University
David Coleman Texas A&M University
Tasfia Kamal University of Maryland
Nathan Wisniewski Oklahoma State University
Kurt Rouser Oklahoma State University
Atanu Halder Oklahoma State University