A multi-copter which takes flight only by the careful balance of air pressure to provide thrust would be an interesting concept to see and could also have beneficial applications.
Advantages of the CAM (Compressed Air Multi-copter)
Removal on propellers, motors, speed controllers and replaced all by a high torque servo for each combo, significant and cost weight savings
No propellers spinning at thousands of rpms can be beneficial for safer commercial drones
With the majority of power being delivered to one motor and speed controller to provide power to an impeller, less power is being consumed compare to the original prop design, this has implications for prolonged flight times
Development of the MARK I prototype.
First steps are to test the feasibility of the project itself.
Initial CFD tests proved if a impeller RPM was maintained at 50000 rpm using the 1/8 scale brushless motor we could reach out goal of a mass inlet flow of 0.25kg/s.
All parts needed for the first prototype are SLA printed.
Final construction, however a problem pertaining clearance and gear meshing led to this prototype being unsuccessful for use.
A MARK II prototype in currently in development, this prototype will use the same implore however a different exhaust system for compressed air to be collected and split amongst the outlets.
Overview of the first prototype showing the impeller in a tight enclosure and 4 openings for exhaust.
Bottom view of the prototype showing the 1/8 scale DC Brushless motor connected to a 1:3 gear ratio.
Estimated idle rpm was ~20,000
Cross-section of air flow shows region of high air velocity which prove to be promising for the current design.
Development of the MARK II prototype.
Mark II Development
Initial testing of Mark I system yielded a unsuccessful design which could not be prototyped within the desired constraints.
A Mark II design was developed around the idea of using an EDF commonly found in high speed R/C planes. This allowed a system with high intake and a low number of moving parts.
Current state of the project is running CFD simulations to estimate possible thrust values based on air intake. Development of a 3D printed test apparatus is currently being assembled.
Side view of streamlines at 40m/s intake air speed. The purpose of this was to see the diffusion of air into the top and bottom valves and testing different diffusers.
Overall view of the streamlines through the entire distribution stage showing the increase in airspeed at exhaust points.
SLA 3D Printed test assembly of EDF stage to measure output air speed for CFD simulation data collection. Initial tests of EDF could only be taken to 30% throttle due to safety concerns. An average exit airspeed of 19m/s was recorded at this throttle level.