Performance Characteristics of Fluidic-Based Thrust Augmentation Using a Slot Jet for Unmanned Aerial Vehicle Propulsion

Abstract

Currently most small vertical takeoff and landing Unmanned Aerial Vehicles (UAV's) use a quadcopter design by utilizing four exposed blades rotating at high RPMs around a central array of components. The research performed in this thesis is focused on understanding the underlying fluid dynamics of a slot jet through the use of flow entrainment for thrust augmentation with the application to be integrated into a novel UAV system with no external moving parts. Current publicly available quadcopter rotor design type aircraft were used as a basis for the design target weight and power to estimate the amount of thrust needed to provide lift. The inclusion of the slot jet causes flow entrainment, thereby creating a turbulent jet downstream. The entrainment effects were studied to define how the flow field interacts within the airfoils. The airfoils were constructed utilizing 3-D printing and placed in multiple configurations varying spacing and angle of attack while laboratory shop air was used to control the slot jet exit velocity. In order to determine the effects of this turbulent flow on thrust, a large experimental envelope was created and tested with a Pitot probe experiment. The velocity profiles were recorded and thrust values were calculated. The experimental envelope was narrowed for the most prominent configurations and Particle Image Velocimetry (PIV) with a high speed laser camera setup was used to capture the flow upstream, midstream, and downstream along the airfoils cord length to examine the turbulent mixing and thrust characteristics within the flow field. The effects of slot jet velocity, confinement spacing, and aerodynamic effects were each singularly inspected for the effects on the flow field and thrust characteristics. The results illustrate that higher slot jet velocity along with inward angle and small confinement produce the greatest thrust although efficiency is maximized with a larger spacing. The thrust values produced indicate the feasibility of producing enough force to lift a UAV vertically off the ground.

Fluid Flow Characteristics of a Co-Flow Fluidic Slot Jet Thrust Augmentation Propulsion System

“…between the holes. Below in Figure 3.1 can be seen the completed experimental setup for the airfoil assembly [44]: The airfoils were attached to two pieces of Plexiglass Acrylic sheets using Scotch .75 in. Two-Sided tape to allow for alterations of the assembly for multiple experimental setups.…”

“…The main dynamic pressure line had an inner diameter of 2 mm. The two lines were then connected to a Supco DDM55 Dual Input Digital Manometer with LCD Display to measure the pressure differential in inches of water.The Pitot Probe testing setup can be seen below inFigure 3.4[44]:…”