Since 10/2/2016, I’ve been sedulously on the Propulsor Zero project!
What are the biggest so-far-passed milestones? Keep reading.
I developed a propulsor blade analysis program.
Using Python, and multiple traditional propeller blade analysis mathematics, I’ve created a propulsor blade analysis program. It is super tightly coupled with XFOIL, a fantastic airfoil section characteristics prediction program.
The program’s name is Sherlock: Study In Scarlett (Sherlock-Scarlett for short). The part of the program doing more heuristic / high-level computing is called Sherlock, and the actual blade analysis code is called Scarlett.
The basic control flow:
- Inputs: Span, Airfoils, Type of Run (how many sections), RPM, Altitude
- Inputs are interpolated at many discrete sections along the span of the blade.
- These sections are stuck into XFOIL, which spits out coefficients of Lift & Drag
- These coefficients are plopped into two individual analysis techniques for propeller blades – the blade element momentum theory, and Goldstein vortex theory.
- Outputs are mixed to output the most accurate estimates (empirically determined weights, compared with data from external sources)
- These final estimates of Thrust, Drag, and Torque are put into a big SQL Lite database with all the runs
It’s quite nice to have this SQL database, since I can do big selects through the data, to find the runs with the best convergence and best force efficiency (thrust/drag). Pretty cool to harken back to the hard work I did for Veritimo in SQL. Strangely nostalgic 🙂
I designed test stand and ordered all the parts.
To better verify the Sherlock-Scarlett program, it is time to actually test some stuff.
I designed a test stand, able to measure Thrust up to (& beyond) 1000N and Torques up to (& well beyond) 20Nm.
I bought a 1.5kW AC induction motor and a 2.6kW variac (voltage controller).
The stand will have the following additional features:
- AC Current Measurement up to 30A
- 2 Load Cells S-type per beam
- Steel construction
- Vibration Measurement
- Optical shaft encoding
I 3D printed four blades & a hub
Using PLA I printed 4 of the best performing blades (as predicted by the Sherlock-Scarlett program).
Polylactic Acid, or PLA, being one of the lowest tensile strength 3D print filaments, will need some reinforcements to be spun with high load @ 1800RPM!
Therefore, I’m fiberglassing the blades with 2 plies of alternating bi-directional fiber direction (0deg, 45deg).
Depending on the results of initial tests with 2 blades, I may go to 4 or 8 plies.
The airfoils are : E-63 at root, and Clark-Y at tip.
Stay tuned!
Jonny Hyman 