Experimental set-ups

Isolated, tilting rotor test rig: The test rig is equipped with a load cell, an encoder, and can be fitted with electric motors in the range of 200W to 7kW for rotors with the diameter range of 6” to 20”. Flow measurements using PIV and hotwire can be conducted around the rotor to understand the changes to the incoming flow before interaction with the rotor plane, as well as the downwash, wake and tip flows.  The PIV and hotwire measurements can be synchronized with both the blade rotation phase (i.e., phase-locked) using the encoder fitted to the electric motor and with the far-field microphone arrays. 

Forward-flight propeller test rig: The test rig is equipped with a load cell, an encoder, a heat management unit, and an electric motor in the range of 200W to 7kW. The load-cell, encoder and motor are placed inside an aerodynamically designed nacelle and the heat within the nacelle is removed using a heat management unit. The test rig can be used in different wind tunnels for simple forward-flight, as well as boundary layer ingestion, turbulence interaction studies, etc. 

Tandem tilting rotor test rig: This test rig is made of two tilting rotor systems. Each rotor is equipped with a load cell, an encoder, and an electric motor in the range of 200W to 7kW. The relative position of each rotor with respect to another can be adjusted both vertically and horizontally to resemble different flight conditions (e.g., single tilting, in-plane and out-of-plane tilting). The motors can also be controlled individually. PIV and hotwire measurements can be carried out to study the flow field before the front rotor, within the gap area of the two rotors and the collective rotor wake. The test rig enables flow, acoustic and aerodynamic investigation of systems involving tandem rotors in hover or edgewise conditions.

Distributed electric propulsion system: The test rig consists of a leading-mounted puller system, with multiple propellers. The wing is a NACA0012 airfoil and can be set at different angles of attack. Each propeller is fitted with a load cell and an encoder. The blade rotation can be phase-locked through direct feedback control loop of the electric motors and encoders via LabView and the rotational speed of the motors can be controlled with a precision of 0.05%. 

Multi-rotor test rig: The multi-rotor system has a base of a 1.5m long with 2 to 4 arms extending to both sides of the longitudinal axis. The arms can be fitted with one or more rotor systems. Each rotor is fitted with an electric motor, an encoder and a load cell and every rotor system can be independently tilted using an axial actuator, delivering a range of distinct hover to forward-flight transition operations. The entire base rests on top of a tilting platform to enable full and synchronous tilting of the multi-rotor system. The test rig can be tested in large wind tunnels and outdoors.

Blade design and fabrication

BladeGen – An in-house blade design tool for generating user-defined blade geometries, highly versatile in blade-defining parameters, e.g., blade chord and span lengths, number of cross-sections and cross-sectional aerofoil profile, with customised profile twist, sweep and taper control. Additional inputs are enabled to define and modify the tip geometries based on conventional and non-conventional approaches. The generated blade geometry data can either be output into ACSII coordinates or CFD-ready formats. The coordinates can be directly imported into Matlab and Python to create STL model for CNC machining or rapid prototyping (3D printing). The CFD-ready formats can be coupled with in-house Vortex Lattice Method solvers for fast and accurate prediction of blade aerodynamic performance. See the videos for more details on the design concept and functions of BladeGen and STL Creation.

Blade manufacturing – At the University of Bristol, we have access to CNC machines for the manufacturing of metal propellers and advanced additive manufacturing facilities to 3D printing of blades.  The team has developed strong expertise in design, manufacturing, balancing and testing of different propeller designs as well as modelling of propeller performance using multi-fidelity numerical tools.