Student: C1C Tim BrownAdvisor: Maj. Lydon

Fast Burning Hybrid Fuels

Preview Motivation Fuel Burning Theory Objectives Predictions Cavitating Venturi Experimental Test Set-Up Results Conclusions

Motivation

There is growing emphasis on safety, environmental cleanliness, low cost, and safety .

Hybrids suffer from low regression rates

Advantages over solids

Advantages over liquids

Throttling Simpler

Safety Cheaper

Restart/Shut-down

Fuel burning theory

Humble, R. W., Henry, G, N., Larson, W, J., Space Propulsion Analysis and Design, Space Technology Series, McGraw-Hill Companies, Inc.,1995.

Objectives Vary oxidizer mass flow rates to find any

oxidizer mass flow dependency

Test the hypothesis that paraffin wax offers high regression potential due to droplets which readily escape from a liquid layer on the surface into the flame zone where they can react with hydrogen peroxide

Calculate a and n from the following equationn

oxGar .

Predictions

0

50

100

150

200

250

300

0 5 10 15O/F Ratio

Sp

ec

ific

Imp

uls

e (

s)

A thermochemistry computer code provided our starting point.

Assume: frozen flow, exit pressure of 82.7 kPa, 90% pure HTP, 95% paraffin wax and 5% carbon black

One test for each different chamber pressure

Gave optimum O/F ratio and predicted Isp GuiPep, Arthur J. Lekstutis, Traxel Labs Inc., Revision 0.04

Predictions Thrust is adjusted to optimize fuel geometry.

Oxidizer mass flow rate is calculated from:

c* is calculated from the thermochemistry computer code where Isp is greatest.

Chamber pressures are based on oxidizer mass flow rates

Length is calculated from cylinder geometry:

0

.

gT

Im sp

total fueltotalox mmm...

)(

)/(22

if

fuelfuel

rr

mL

FO

mm

totalfuel

/1

..

trrr if .

tmm fuelfuel .

Predictions

Motor Number 1 2 3 4 5

Initial Mass (kg) 0.462 0.5 0.614 0.625 0.823

Initial inner port diameter (cm) 2.54 2.54 2.86 2.54 2.54

Length (cm) 8.41 8.41 10.5 10.6 13.8

Chamber Pressure (kPa) 2068.4 2068.4 3447.4 3447.4 4826.3

O/F ratio 5.8 5.8 5.8 5.8 6.31

Isp (s) 240.5 240.5 255.4 255.4 262.6

Thrust (N) 384.8 384.8 524.9 524.9 660.6

mdot ox (kg/s) 0.14 0.14 0.18 0.18 0.22

c* (m/sec) 1622 1622 1622 1622 1622

Cavitating Venturi

To ensure that the mass flow rates of oxidizer were as desired during the experiment the cavitating venturi was calibrated at varying pressures using H20. 01759.0004.22

.

Pm OH

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 100 200 300 400 500 600 700 800

Upstream Pressure (psi)

H2O

2 M

ass

Flow

Rat

e (lb

s./s

)

Experimental Test Set-up

2,000 psi nitrogen tank

Water-cooled nozzle

Purge system Oxidizer

Fuel cartridges easily exchanged

Spacer

Data acquisition at 1,000 Hz

Experimental Test Set-Up

Pressure transducers were inserted pre-CV, post-CV, and chamber

The nozzle had a 1.1075 square inch exit area and a .1104 square inch throat area yielding an expansion ratio of 10.03.

Results

Results

Results

2/)(

.

fi portport

ox

avgox AA

mG

)(2

))/)(4(( 2.

if

iiffi

tt

DDLmm

t

rr

0

1

2

3

4

5

6

7

70 90 110 130 150 170 190

Oxidizer Mass Flux, kg/m^2-sec

Reg

ress

ion

Rat

e, m

m/s

ec

paraff in/Goxsystem forcomparisonparaff in/HTPregression rate

5% mass loss

9593..

0344. oxGr

Results

.*

m

APc Tc

actual

0

.

gm

TI sp

ltheoretica

actual

c

c

Motor Number 1 2 3 4 5

Final Mass (kg) 0.303 0.359 0.479 0.366 0.538

Final inner port diameter (cm) 4.46 4.42 5.12 4.17 4.9

Chamber Pressure (kPa) 2120 1774 2698 2179 3114

O/F ratio 2.7 3.95 4.03 1.89 3.22

Isp (s) 97 103 151 101 136

Thrust (N) 175 170 276 220 340

mdot ox (kg/s) 0.135 0.135 0.149 0.144 0.194

c* actual (m/sec) 819 749 1032 704 872

Efficiency 0.505 0.462 0.636 0.434 0.538

rdot (mm/s) 4.43 3.5 2.87 5.28 3.63

rdot using web thickness (mm/s) 2.63 2.22 2.65 2.22 2.5

rdot assuming 5% loss of final mass

(mm/s) 4.12 3.16 2.31 5.01 3.38

Gox (kg/m-s^2) 131.19 131.89 111.62 154.31 162.4

Conclusion Similar tests conducted by Stanford

University using gaseous oxygen as the oxidizer achieved regression rates around 2.6 mm/sec for values of 130 kg/m^2-sec. Our regression rate is closer to 3.23 mm/sec for the value of 130 kg/m^2-sec. The hypothesis that paraffin is capable of a high regression rate, especially with hydrogen peroxide, was validated.

Conclusion The main shortcomings were lower than

expected , , and c*.

Difficulty of recovering specimen’s weight after firing as well as calculating web-thickness. Therefore included a 5% loss regression result which is still above expected

spI

Questions?