Liquid Bipropellant Injector Senior Design Project
The purpose of this project was to inform the design of pintle injectors for the aerospace community at large by providing useful data describing spray cone behavior as a result of various normalized design parameters. Data in the aerospace community is proprietary and rarely shared between companies, which means that new players must develop their own knowledge base, effectively re-doing science that has been established for others for many years. In the age of New Space, basic rocketry data should be available to the community so more resources may be allocated to competition and innovation.
My team designed a modular LOX/Kerosene pintle injector and measured how the angle of the spray cone changed with varying tip geometry and propellant momentum ratio. The tip geometry is described by the term Blockage Factor, which is a ratio of the circumference of the tip covered in orifices through which fuel is radially ejected. The propellant momentum was described by the Total Momentum Ratio, which is the momentum flux ratio of the two liquid propellants.
I worked with two stellar individuals for this project, JT Blakely and Jacob Hogge (center and left in the image above). They are fantastic partners and contributed much in the specifics of feed system design and data analysis with Matlab and LabVIEW. My main responsibilities were component design and manufacturing.
We designed the pintle injector to be manufactured on the Haas mill that I was given access to through a separate research assignment from the Architecture department, which owns the mill. We designed the injector body to interface with various tips, also machined on the same mill using a 5-axis dual rotary addition. All dimensions were sized either from incompressible flow principles or tooling and stock constraints. The addition of an inner wall was found through ANSYS analysis to significantly improve pressure distribution around the annulis exit.
I learned to machine through this project purely by reading manuals online and consulting a Haas technician when needed. I used MasterCAM to program the Haas DM-1 Mill. Consistent tolerances of under +/- 0.002" were achieved, often under +/-0.001".
Enjoy the following gallery of pictures of the various injector components and feed system cart being manufactured.