thortek expander cycle engine presentation - 15 slides 1 design of an expander cycle engine with j-2...

Thortek Expander Cycle Engine Presentation - 15 Slides

1

Design of an Expander Cycle Engine with J-2 Equivalent Thrust

AIAA 2009-4908

45th AIAA/ASME/SAE/ASEE

Joint Propulsion Conference Denver, Colorado

Douglas G. Thorpe

Thortek Labs, Inc., Irvine, Kentucky

Morehead State University, Space Science Center

August 2-5, 2009


2

Pump Engine Cycles -Simplest to Most Complex

Expander Cycle Gas Generator Staged Combustion

•Least complex

•Great Isp

•Thrust limited

•More complex

•Least Isp

•Great thrust

•Most complex

•Great Isp

•Great thrust


3

Problem with Expander Cycle Engine• Square Cubed Rule –A term to represent the relationship

between the area and volume of an object; – as the size of a box doubles in size, its surface area will increase by 4 (2

square) while its volume will increase by 8 (2 cubed).

• For rocket engines - the square cube rule dictates that as the circumference (& surface area) of an engine doubles; it will obtain 4 times (2 square) in heat energy; but engine thrust will increase by a factor of nearly eight (2 cubed).

• Since propellant pump power requirements are directly related to thrust and since heat energy to drive the turbine is directly related to the engine surface area, then a point is quickly reached where insufficient heat energy exists to drive the turbines and therefore the pumps.


4

Extreme Example of Expander Cycle Engine

• The Ariane 5 Vinci engine - An extreme example of an expander cycle engine

• Extra long combustion chamber designed for maximum regeneration

• Maximum thrust – 40,460 lbf


5

TVC & Hydraulic Plumbingfor Ares 1st stage – RE: scale/size


6

TVC & Hydraulic Systems for Shuttle SRB – RE: complexity

•Shuttle SRB have two 150 hp hydraulic TVC per booster with worst case demand of 50 hp.

•Each TVC actuator can push 65,000 lbf and move 6 deg/sec or 5 inch/sec at that load.


7

Problems with contemporary vehicle attitude control

• Vehicle attitude control (pitch, yaw, and roll) and power are just as significant for launch operational costs

• Hydraulic actuators are a tremendous source of processing problems since they add enormous amount of support hardware– hydraulic pumps, accumulators,

hypergolic APU, hypergolic purge

systems, cooling systems, and GSE • Pictured: RS-68 roll control is via

movable turbine exhaust duct


8

Carbon Jet Vanes on Redstone Missile• Purpose of jet vanes were to guide vehicle during first seconds of flight

•Jet vanes were designed to ablate away, then allow fins to guide vehicle

•Jet vanes were actuated by 1 hp chain-driven electric motors

•Jet vanes can control pitch, yaw AND ROLL

•If jet vanes were symmetrical, very little force would be needed to rotate and hold vanes in non-zero position

Picture obtained from:

Redstone Missile Jet Vanes, http://farm3.static.flickr.com/2351/1740796971_449233260a.jpg?v=0


9

Cross-View of Regenerative Nozzle showing temperature gradient from center of jet stream to outside of nozzle

Figure obtained from: Sutton, pg 99

•Boundary layer protects the nozzle inner wall from seeing full temperature of hot gas.

•But, it also reduces heat flux into cooling media.

•Top of jet vane will see total temperature of hot gas & must be constructed of material such as Titanium.


10

Rocket Engine Energy Balance

Figure obtained from:

Sutton, George P, “Rocket Propulsion Elements”, Wiley-Interscience Publication, 4th edition, 1976, pg 40

Energy available to

drive proposed expander

cycle engine


11

J-2 Gas Generator

engine vs J-2 Equivalent Expander

Cycle Engine

Engine TypeEngine Cyclepropellant type LOX LH2 LOX LH2Thrust-vacuum (lbs)Isp-vacuum (seconds)

pressure increase in pump (psi) 1,069 1,220 1,069 1,854Head increase in pump (ft) 2,172 38,337 2,172 58,258Flow rate (lb/sec) 467.7 84.2 467.7 84.2Shaft speed (rpm) 8,698 27,167 8,698 27,167Efficiency (%) 80% 73% 80% 73%Shaft Power (hp) 2,302 8,587 2,302 13,049Required NPSH (ft) 42.3 176 42.3 176

Shaft Power (hp) 2,302 8,587 n/a 15,351Inlet Pressure (psi) Total 89.3 652 n/a 1,200Pressure ratio 2.65 7.2 n/a 1.12Outlet Pressure (psi) 33.7 90.6 n/a 1,069Shaft speed 8,698 27,167 8,698 27,167Inlet Temperature (F) 768 1,200 n/a 1,200Efficiency (%) 47% 60% n/a 60%

Total Flow Rate (lb/sec) n/a n/aMixture ratio (oxidizer/fuel) n/a n/aFlow Rate (lb/sec) 3.41 3.63 n/a n/a% of Pump Flow Rate (%) 0.73% 4.31% n/a n/a

7.040.94

Gas Generator

232,250421

J-2 ExpanderExpander Cycle

Gas Generator

Turbine

Pump

232,250

J-2


12

Thermodynamic Comparison between J-2 GG vs Expander Cycle

J-2 Gas Generator J-2 Closed Expander

Turbine Inlet Steam (lbs/sec) 3.836 0Turbine Inlet GH2 (lbs/sec) 3.204 84.2Turbine Inlet Pressure (psi) 652 1,119Turbine Inlet Temperature (F) 1,200 1,200Turbine Inlet Enthalpy - Steam (Btu/lbm) 1,627 0Cp @ Inlet Temp (btu/lbm*F) 3.52 3.52

Turbine Outlet Pressure (psi) 89.3 1,069Turbine Outlet Temperature (F) 768 1,164Turbine Outlet Enthalpy -steam (Btu/lbm) 1,414 0Cp @ Outlet Temp (btu/lbm*F) 3.49 3.52

Total Power from steam (Hp) 1,154.9 0.0Total Power from GH2 (Hp) 6,859.5 15,302.5Total Turbine Power (Hp) 8,014.4 15,302.5


13

OEPSS – Operationally Efficient Propulsion System Study

1. Enclosed Compartments2. LOX tank forward3. Side Mounted Boosters4. Hypergolic Systems5. Hydraulic Systems6. Pneumatic Systems7. Pressurization Systems8. Multiple Propellants

9. Pre-Conditioning10. Excessive Subcomponent Interfaces11. High Maintenance Turbopumps12. Ordnance Systems13. Retractable Umbilical Carrier Plates14. Engine Gimbal Systems15. Ocean Recovery & Refurbishment

OEPSS was a study based on lessons learned on operational processing of launch vehicles and their ground support equipment.

Out of the 15 top design concerns delineated in OEPSS, the proposed engine with jet vanes will eliminate 5 concerns


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Further Study is needed• To determine the optimal performance

characteristics of a J-2X equivalent expander cycle engine,

• To determine the true manufacturing and processing costs of engines & power systems, – What design parameters or techniques should be changed in order

to obtain an engine under $1M • To determine the optimal size of the jet vanes to

power the J-2X equivalent expander cycle engine,• To determine optimal materials and design of jet

vanes.


15

Conclusion• Much more heat energy is available from regeneratively

cooled jet vanes vs extending the nozzles – Jet vanes stick in the center of jet flow – Whereas an insulating boundary layer builds up along the nozzle

wall

• Jet vanes require far less force to operate than TVCs.– Less force = less power = smaller electric motors = smaller

batteries

• Up to 57% of the total fuel energy could be available to power the expander cycle turbines via the jet vanes.

• Compare this 57% vs 2% available for regeneratively cooled nozzle and combustion chamber.

thortek expander cycle engine presentation - 15 slides 1 design of an expander cycle engine with j-2...

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