AARLITE:
AIR AUGMENTED ROCKET
with LARGE INDUCED
TURBULENCE ENGINE
Thesis Seminar
Allen Capatina
What is an Air Augmented Rocket?
• Mode of Rocket Based Combined Cycle (RBCC)
• “The idea is to install a simple, fixed geometry, lightweight shroud [or
duct] around a rocket engine.” – Foster
• Rocket engines normally burn fuel rich, meaning:
– Atmospheric air can mix and combust unused fuel
– Secondary combustion expands against shroud or mixing duct
– Secondary expansion produces additional thrust and increases Isp
• At high altitudes (little to no atmosphere), shroud acts as a nozzle extension
Shroud or
Mixing Duct
Rocket Engine
Source: R. W. Foster, Escher, W. J. D. and J. W. Robinson. Air Augmented Rocket Propulsion Concepts. Madison, WI: Astronautics Corporations of America
Technology Center, 1988. F04622-86-C-0094.
2/13
Why Study AAR’s?
• Make Single Stage To Orbit (SSTO) feasible
• Resurgent interest in Rocket Based Combined Cycle propulsion
Source: R. W. Foster, Escher, W. J. D. and J. W. Robinson. Air Augmented Rocket Propulsion Concepts. Madison, WI: Astronautics Corporations of America
Technology Center, 1988. F04622-86-C-0094.
3/13
Previous Cal Poly Research
• Kyle Johnson (March 2013) SCAARD
– Used in Aero 401 bi-prop engine lab
• SCAARD: +20 lbf at ~300psi
• SCAARD plus Ducts:
– Thrust with Straight duct: -0.62 lbf
– Thrust with Diverging duct: -0.74 lbf
• SCAARD created positive thrust but duct
negatively augmented the thrust
Source: Kyle Johnson. Axisymmetric Air Augmented Methanol/GOX Rocket Mixing Duct Experimental Thrust Study. Thesis project, Aerospace Engineering
Department, California Polytechnic State University, CA, March 2013.
Trevor Foster. Rectangular Ducted Methane/GOX Thruster. Aerspace Engineering, California Polytechnic University. San Luis Obispo: s.n., 2008. Master's
Thesis.
4/13
Old vs. New System Design
Primary flow
Secondary
flow
Primary flow
Combustion
Chamber
Combustion
Chamber
Steel Shell
Annular Cavity
Retainer
Mixing
Duct
Old System
New System
• Entrained secondary flow is faster than the ambient air and lower pressure
• Low pressure pulls down on the engine and up on the mixer/ejector
Source: Kyle Johnson. Axisymmetric Air Augmented Methanol/GOX Rocket Mixing Duct Experimental Thrust Study. Thesis project, Aerospace Engineering
Department, California Polytechnic State University, CA, March 2013.
5/13
New Engine Parameters and Duct Design
•
Primary Engine Parameters:
–
–
–
–
–
–
Chamber pressure:
Thrust:
Ethanol mass flow:
Oxygen mass flow:
Chamber length:
Chamber diameter:
– Throat diameter:
– Exit diameter:
•
• Importance:
𝑷𝑪 = 𝟏𝟎𝟎𝟎 𝒑𝒔𝒊
• Increased pressure ratio (Pc/Pamb)
𝑭 = 𝟏𝟎𝟎 𝒍𝒃𝒇
• Increased thrust for better
𝑚𝐹 = 0.118 𝑙𝑏𝑚/𝑠
measurement margin
𝑚𝑂𝑥 = 0.247 𝑙𝑏𝑚/𝑠
• Reduced outer diameter to reduce
𝑙𝐶 = 3.32 𝑖𝑛
dead area at end of engine
𝐼𝐷𝐶 = 1.14 𝑖𝑛
• Third duct tests a high pressure case
𝑶𝑫𝑪 = 𝟐. 𝟐𝟎 𝒊𝒏
𝐷𝑡ℎ = 0.282 𝑖𝑛
𝐷𝑒𝑥 = 0.844 𝑖𝑛
3 Ducts: 2 x Straight and 1 x Diverging
– Geometries based on Kyle Johnson and NASA reports:
• Inlet to throat area:
40/1
• Exit to inlet area for diverging:
2/1 otherwise 1/1
• Length to inlet diameter:
2/1
• Length to inlet diameter:
5/1
Source: Kyle Johnson. Axisymmetric Air Augmented Methanol/GOX Rocket Mixing Duct Experimental Thrust Study. Thesis project, Aerospace Engineering
Department, California Polytechnic State University, CA, March 2013.
Timothy D. Smith, Christopher J. Steffen Jr., Shaye Yungster, Dennis J. Keller, Performance of an Axisymmetric Rocket Based Combined Cycle Engine During
Rocket Only Operation Using Linear Regression Analysis. National Aeronautics and Space Administration Lewis Research Center. 1998. NASA Technical Paper.
NASA/TM-1998-206632.
6/13
Large Induced Turbulence
• Annular cavity at nozzle exit plane
– Enhances secondary combustion (a.k.a. afterburning)
– Cavity design is based on Yu and Schadow
• Conducted similar engine flow physics ground testing
– Verified visually with camera
Source: K. H. Yu, and K. C. Schadow. Role of Coherent Structures in Turbulent Compressible Mixing. Research and Technology Division, China Lake, California.
Elsevier Science, New York, Inc. 1997. 0894-1777.
7/13
Passive-flow excitation with an
open cavity at the exit of a
supersonic discharge
Flow
Rectangular
Cavity
• Above: Illustration of cavities and the dimensions, by
Yu and Schadow
• Right: Flow visualization over rectangular cavity.
Shows growth of vortex in shear layer, by Rossiter
Source: K. H. Yu, and K. C. Schadow. Role of Coherent Structures in Turbulent Compressible Mixing. Research and Technology
Division, China Lake, California. Elsevier Science, New York, Inc. 1997. 0894-1777.
Rossiter 1964 - Wind Tunnel Experiments on the Flow Over Rectangular Cavities at Subsonic and Transonic Speeds
8/13
Cavity Design
• Strouhal Number Equation:
– 𝑆𝑡 =
Flow
•
•
•
•
•
•
•
𝑓𝐿
𝑈
=
𝑚−𝛼
1
𝑀+𝐾
𝑐
𝛼 = 0.25 (empirical value)
𝐾𝑐 = 0.57 (empirical value)
𝑚 = 1, 2, 3, …
𝑀 = 3.18
𝑈 = 2675 𝑚/𝑠
𝛾 = 1.1922
𝑓 = 140 𝑘𝐻𝑧
– Solving for
𝐿 ⇒ 𝐿 = 𝟎. 𝟏𝟐𝟑 𝒊𝒏𝒄𝒉𝒆𝒔
– Let
Cavity of graphite:
0.123” x 0.123”
𝐿
𝐷
= 1 ⇒ 𝐷 = 𝟎. 𝟏𝟐𝟑 𝒊𝒏𝒄𝒉𝒆𝒔
9/13
Test Matrix (expected)
Test
Engine Thrust Mixer Thrust O/F
(lbf)
(lbf)
Ratio
Large
Inlet Dia. to
Induced
Length Ratio
Turbulence
Mixer Area
Ratio
Inlet to Throat
Area Ratio
0a
100
No duct
2.1
N
No duct
No duct
No duct
0b
99
No duct
2.1
Y
No duct
No duct
No duct
1
99
4
2.1
N
2
1
40
2
98
6
2.1
Y
2
1
40
3
102
7
1.5
N
2
1
40
4
101
9
1.5
Y
2
1
40
5
99
9
2.1
N
2
2
40
6
101
11
2.1
Y
2
2
40
7
98
4
1.5
N
2
2
40
8
100
6
1.5
Y
2
2
40
9
101
10
2.1
N
5
1
40
10
99
14
2.1
Y
5
1
40
11
12
102
100
11
16
1.5
1.5
N
Y
5
5
1
1
40
40
10/13
Schedule
•
•
•
•
Finish manufacturing by Winter
Cold flow test and calibrate in Winter
Test and analyze during Winter and Spring
Write report and defend at the end of Spring
11/13
Year:
Month:
Design and support
2015
2014
Past Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sep.
Project goals
Funding proposal
Research and understand system
Calculate engine parameters
Engine and test stand design
Finalize bill of materials
Purchase materials
Fabrication
Machine all components
Integrate engine
Route plumbing and instrument engine
Motor Testing
Pressure test engine, plumbing, and sensors
Cold flow test engine
Double check all subsystems
Static testing
Analyze test results
Final Report and Defense
Write report
Review eport
Present report
12/13
Thank you
Questions?
13/13
Backups…
References
1.
2.
3.
4.
5.
6.
R. W. Foster, Escher, W. J. D. and J. W. Robinson. Air Augmented Rocket Propulsion Concepts.
Madison, WI: Astronautics Corporations of America Technology Center, 1988. F04622-86-C0094.
Kyle Johnson. Axisymmetric Air Augmented Methanol/GOX Rocket Mixing Duct Experimental
Thrust Study. Thesis project, Aerospace Engineering Department, California Polytechnic State
University, CA, March 2013.
Trevor Foster. Rectangular Ducted Methane/GOX Thruster. Aerspace Engineering, California
Polytechnic University. San Luis Obispo: s.n., 2008. Master's Thesis.
Timothy D. Smith, Christopher J. Steffen Jr., Shaye Yungster, Dennis J. Keller, Performance of an
Axisymmetric Rocket Based Combined Cycle Engine During Rocket Only Operation Using Linear
Regression Analysis. National Aeronautics and Space Administration Lewis Research Center.
1998. NASA Technical Paper. NASA/TM-1998-206632.
K. H. Yu, and K. C. Schadow. Role of Coherent Structures in Turbulent Compressible Mixing.
Research and Technology Division, China Lake, California. Elsevier Science, New York, Inc.
1997. 0894-1777.
Rossiter 1964 - Wind Tunnel Experiments on the Flow Over Rectangular Cavities at Subsonic and
Transonic Speeds
Diagram of Ducts
Note: not
to scale
Short Straight
•
•
•
•
Long Straight
Inlet to throat area:
Exit to inlet area for diverging:
Length to inlet diameter:
Length to inlet diameter:
Short Diverging
40/1
2/1 otherwise 1/1
2/1
5/1
7/13
Entire System Integrated
Cross Section of AAR Engine
Spark Plug
Secondary flow
Primary flow
Mixing Duct
Annular
Cavity
Combustion
Chamber
Sealing and Nozzle Insert
Engine, Duct, and Test Stand Mockup
Injector Design and Fuel Selection
• Ethanol – Dave Lynch justification
Propellant Mass Flow Measurement
• Ethanol to the left
• Oxygen to the right
Oxygen Feed System
Ethanol Feed System
Control Box Design
CPConnect Proposal
• Awarded $4,700 from Cal Poly Connect
Interdisciplinary Project Program
• Current Team:
– Samantha Rawlins (Aero)
– George Georgiou (Aero)
– Kyle Rosenow (MatE)
– Daniel Johnson (Aero)
– Adam Whitmarsh (Aero)
– Steve Rieber (ME)