The document discusses the design and testing of a coaxial swirl injector for liquid propulsion, highlighting its advantages such as improved atomization and efficiency. It includes a trade study comparing injector types, design parameters, and machining processes, emphasizing the need for reliability and safety. The budget and next steps for finalizing CAD, ordering parts, and initiating a testing campaign are also outlined.

1. Coaxial Swirl Injector PDR
Liquid Propulsion Laboratory
By: Nicholas Ilibasic
Michael Mastrangelo
Ryan George
March 4nd, 2020

2. • Introduction
• Motivation
• Trade Study
• Requirements
Agenda
Coaxial Swirl Injector
• Design process
• CAD model
• Injector sizing parameters
• Machining
• Testing Procedure
• Budget

3. What is a Coaxial Swirl Injector

4. Why do we need a new design?
• Provide the lab with new knowledge on injector types
• Minimal design change from gas-liquid to liquid-liquid
• Improved atomization, has reached 99% efficiency in tests
• Easy to iterate
Major changes:
• J&J injector will consist of a single coaxial swirl element
• Phenolic resin to cool injector face
Motivation

5. Injector Trade Study
Injector Type
Weight Criteria Showerhead Impinging Pintle Coaxial Swirl
1 Ease of Iteration 4 4 2 2 5 5 5 5
Rank (1-5)
0.8 Flexibility 4 3.2 5 4 5 4 5 4
0.5 Efficiency 1 0.5 4 2 3 1.5 5 2.5
0.9 Safety 5 4.5 5 4.5 4 3.6 3 2.7
0.7 Thermal Control 2 1.4 3 2.1 3 2.1 3 2.1
Totals 2.72 2.92 3.24 3.26

6. R1 Injector Requirements
1.1 Ability to be machined
1.2 Provide 400 psi of chamber pressure
1.3 Provide total mass flow of .4 kg/s
1.4 Combustion stability
Requirements
R2 Safety
2.1 Characterize oscillating waves
2.2 20% stiffness over injector
2.3 Thermal control
R3 Reliability
3.1 Multiple test cases
3.2 Ability for throttling

7. Firing Parameters
Propellant GOX/ RP-1 (Kerosene)
Chamber Pressure 400 psi
Chamber Temperature 3100 - 3350 K
Injector Pressure 480 psi
Total mass flow rate 0.4 kg/s
Burn time 6 seconds
O/F Ratio 2

8. Old Showerhead Design

9. • To build and test a shower head injector, the entire part must be printed
and machined
• A coaxial swirl injector's efficiency is directly linked the element's design
Overall design strategy is:
Design Strategy
Hot Fire Engine
Resasses Feasibility Switch GOX to LOX
Integrate Specific Element to Complete Injector
CAD Full Injector Implement Thermocontrol
Charaterize Element Flow
Design Swirl Element Design Test Article

10. Design I
• Heavlily inspired by the RD-0110 (upper stage
of Soyuz family)
• Note this design does not use a vortex chamber on the
fuel side

11. Design II – Gaseous Oxygen Element

12. Design II – Liquid Kerosene Element
Copenhagen Suborbitals

13. • First, look at the pressure
drop across the inlets to verify
stiffnesss
• Then, look at numerical results
for tangenetial velocity and
axial velocity
Figures: "Study of internal flow
of a bipropellant swirl injector of
a rocket engine"
CFD Analysis on Designs

14. Testing Article

15. Liquid kerosene swirl in center with impinging jet gaseous oxygen on side
Design III

16. GOX/RP-1 Coaxial Swirl Injector Uncertainty
Coaxial Swirl Method
Pros
● Increased efficiency
● Similar design for BASE 11/Spaceshot
Injector design
● Easy iteration
Cons
● Gaseous oxygen swirl more difficult to model
than liquid
● Gaseous oxygen flows along the walls of the
vortex chamber
● Few papers discussing design process
Kerosene Swirl with GOX Jet
impinging Method
Pros
● Easier to model
● Can still learn from using single kerosene
swirler element
Cons
● Lower efficiency
● More work needed to move towards coaxial
swirl injector

17. Testing Procedure
Calculate
injector
geometry
Machine
injector
element
Inspection
Run WFTS/
Nitrogen gas
cold flow
Analysis of
testing data
Set Injector
parameters (mass
flow rate, Pc, ΔP)
Feasibility
assessment
Design
Optimization

18. Injector Sizing Equations - Fuel
Radius of nozzle (mm) 17.14
Radius of inlet channel (mm) 3.94
Length of nozzle (mm) 34.26
Length of inlet channel (mm) 11.8
Radius of swirl vortex (mm) 29.34
MATLAB simulation on G drive

19. Injector Sizing Equations - Oxygen
diameter nozzle (mm) 16.525
diameter inlet (mm) 2.06
Length of inlet (mm) 3.09
diameter swirl chamber (mm) 18.590
Reynolds Number 274491

20. Interface with WFTS:
• ¾ inch swage
• Pressure transducers to measure pressure in the vortex chamber
• High speed camera to image cone angle and spray oscillations
• Use dye to distinguish between two cones
Testing Campaign

21. Machining
• Machine 20 elements
using different inlet and
nozzle radii.
• Testing article made of
aluminum parts. Held
together using fasteners and
O-rings to prevent leaks.
• Swirl elements placed inside
testing article

22. • Induction welding:
SILVER BRAZING PASTE
FLUX - Superior No. 6JB
Only for nonferrous
metals such as brass.
• MIG welding equipment
(USC facilities)
Welding

23. • Testing article: $100
• Welding: Free
• Elements: $40 for 20 elements
• Fasteners and sealing: $20 (8 Screws,
8 Nuts, 8 Washers) Assess the extra
already in lab
• Final injector design: $1200
1. Additively manufactured and post
machining: $1200 ($800 +$400)
Maraging steel (same material as J&J)
2. Machined
Labor $$
Budget

24. 1. Study oscillating waves formed at different cone angles.
2. How do we test and validate the design works?
3. Final injector design to be machined or additively manufactured?
Questions

25. • Finalize CAD of swirler elements
• Select sealing
• Order Parts
• Begin Machining
• Begin testing campaign on WFTS
• Send injector drawings to Machine Shop (current lead time ~ 3 weeks)
Next Steps