A design methodology for rotors of small multirotor vehicles

Abstract

A model is presented for the aerodynamic performance prediction of fixed-pitch rotors for small unmanned aerial vehicles. The method uses a blade element momentum theory based approach that is formulated specifically for small rotors operating in hover and edgewise flight. In order to validate the model, a rotor test stand is used to measure the performance of a commercially available rotor for several inflow angles and advance ratios. The predictions agree with measurements for operating conditions excluding conditions with suspected vortex ring state. The model is incorporated into a numerical optimization scheme to demonstrate its potential as a design tool. Designs are presented that minimize the power loading for single- and multi-point operating conditions. The optimized designs have hyperbolic twist distributions, higher solidities, and operate at lower tip-speeds than existing designs. A potential flow based model is also presented to predict the wake interactions between multiple rotors in configuration.

Low Reynolds Number Scaling Effects For Small-Scale Rotors

“…The experimental results are compared to a rotor performance prediction program based off of the blade element momentum theory. This is a code that was developed at Ryerson University by Tim Carroll [9] and was created to predict rotor performance for small quadrotor-like aircraft.…”

“…Carroll [9] and was created as a way to predict rotor and vehicle performance. The code predicts and outputs the rotor performance parameters for a range of flight conditions and vehicle configurations.…”

“…This drag force opposes the rotation of the motor and therefore increases the power required by the motor. Additionally, the portion of the retreating blade in reverse flow has an angle of attack of about 180 • relative to the flow direction causing the sectional lift coefficient to be approximately zero [9]. On the advancing side, lift is produced along the full span of the blade, which causes a difference in the lift between the advancing and retreating side also known as "dissymmetry of lift".…”

“…First the input parameters were specified, which included defining the rotor geometry and radius along with inputting the operating conditions, which in this case were the rotor RPM and freestream velocity. A uniform momentum with linear inflow method was chosen as this was the model most suited to edgewise flight [9]. With the preceding parameters specified, the program was run and the function on the left side of Fig.…”

Wind Tunnel Testing on Low Rise Bunkie Structures and Its Application as Affordable Storm Shelters

“…This subsonic WT has a closed loop with a test cross-section of approximately 1m x 1m. The wind tunnel is suitable for smooth flow (i.e., aerospace applications) with a maximum turbulence intensity of 0.5% (Carroll 2017, Barcelos 2015. This is significantly less than the turbulence intensities encountered by tall buildings which are engulfed in atmospheric Boundary Layer (BL) (ESDU 2001(ESDU -2002.…”