Design
What: The Contra-Rotating Ducted Fan Propulsion System was originally designed to be the main source of thrust for my personal project ‘Humming Bird’.
How: The system uses two contra rotating propellers to counteract the torque affect the system would have on a functional vehicle. The two propellers were powered by two separate motors with dedicated batteries.
Manufacturing: The system was almost entirely 3D printed with PLA filament and joined using screws. The motors were controlled by electrical speed controller which were connected to a micro controller.
Results
To determine the effect nozzle convergence ratio has on thrust I printed and tested 3 cases of convergence ratios: 1 (No Nozzle), 1.25, and 1.35. I initially predicted that as I decrease throat area, thrust will increase until the pressure at the throat is too high which will cause the flow to be pushed back up through the duct thereby decreasing thrust. The testing confirmed my hypothesis and the results can be viewed in the table below.
| Convergence Ratio | Maximum Thrust (grams) |
| 1 – (No Nozzle) | 680 |
| 1.25 | 815 |
| 1.35 | 770 |
Igor Khalip 