In attendance: Brian O’Neel
The first paraffin test grain was poured this afternoon. It was cast in place in the 2 inch diameter cardboard tube.
The paraffin (160 deg hurricane wax) was heated to 300 deg Fahrenheit in a crock-pot and 1% graphite powder was added as an opacifier. A 0.49” aluminum dowel was sealed into the nozzle blank with a small ring of putty then the cardboard tube and premix graphite sleeve was placed over the dowel, taped into place, and then molten paraffin was poured into the sleeve. The entire assembly was then put into the refrigerator for 15 minutes.
After 15 minutes the paraffin had shrunk approx. 10% and was partially solidified. More molten paraffin was added to bring the level within 0.5 inches from the top of the graphite premix chamber. The assembly was then placed back into the refrigerator and allowed to cool for 2 hours.
After 2 hours the paraffin grain was completely solidified and the aluminum mandrel was fairly easily twisted out with a pair of pliers.
The fuel grain looks good! Some minor changes could be made to the procedure to make it a bit less messy in the future but this grain looks good enough to test fire.
Also completed was several flange/chamber fillet weld mock-ups so that Brian can practice TIG welding on the appropriate thickness material before the final combustion chamber is welded.
Beyond welding the combustion chamber flanges on the main bulk of the work on the combustion chamber is done. There are still several things to do though among the highest priority are; safety analysis, nozzle design, and injector design:
There will be another hybrid meeting in 2 weeks. Hopefully more people will show :).
To Do List:
- Pressure vessel analysis
- Bolted connection analysis
- Weld analysis
- Nozzle design – Throat dia, exit dia., converging and diverging angles, O-ring placement
- Injector Design – Simple orifice, pintle, swirling, impinging doublet, (stainless steel or brass)?
- Calculate maximum flow rate give Cv for ’42 series’ Parker solenoid and Spartan Scientific solenoid valves.
- Research oxygen and nitrogen feed lines – Braided stainless steel? Look at different connectors and how they can adapt to the solenoid valves
Create plumbing diagram
- Formal write up and spread sheet used for preliminary design
- Safety analysis
- Practice TIG welding for combustion chamber
Need to add to website:
Information on initial fuel grain pour
Parts list and data sheets