Computational analysis of the preflow phase during start-up …rschmehl.home.xs4all.nl/CV/presentations/wsa07_prese… · · 2009-05-17• Chamber pressure in cryogenic Vulcain

Dr.-Ing. Roland SchmehlPropulsion and Aerothermodynamics Division

Wärmetechnisches SeminarLehrstuhl für Wärme- und Stoffübertragung,

RWTH Aachen, 12. Juli 2007

Computational analysis of the preflow phase during start-up of ARIANE 5’s upper-stage engine AESTUS

Slide 1

Dr.-Ing. Roland SchmehlPropulsion and Aerothermodynamics Division Outline

1. Ariane 5 and flight 142 anomaly

2. Upper stage ignition

3. Thermophysical properties of propellants

4. Computational approach

5. Development of physical models

6. 3D-Flowfield simulation and analysis

7. Parametric variation of injection temperature

8. Parametric variation of initial size spectrum

9. Conclusions and Outlook

Slide 2


Introduction

Ariane 5 fact sheet

• Development started in 1987, first flight was 1996

• Total development costs: 7 billion USD

• Commercial provider for 180 million USD per launch

• Achieved > 50% market share of satellite launches to GSO

• Launch mass: 750 to 780 t, heigth: 47 to 57 m

• GTO lift capacity: 6.9 to 10 t

• Maximum thrust: 1200 to 1300 t

• Chamber pressure in cryogenic Vulcain engine: 11 MPa

• Vulcain 2 generates power equivalent to nuclear reactor

• Vulcain engine burn time: 10 min

• Solid boosters burn 2 min and provide 90% of lift-off thrust

Slide 3


Introduction

Ariane flight 142

ˆ

Upper stageignition

Main stageseparation and burnout

Payloadfairingjettisoned

Solid rocketboosterseparation

50 km

100 km

150 km

200 km

Satelliteseparation

Main stagebreakup

• Launched on 12-07-2001 from Kourou

• Payload: ARTEMIS and BSAT-2b telecommunications satellites

• Orbital injection with 9065 m/s at an altitude of 1732 km (planned)

Slide 4


Introduction

Flight 142 anomaly

• Anomaly at ignition of storable-proppelant AESTUS upper-stage engine

• Pressure in start-up phase (∆t = 400 ms) rises twice as fast as normal

• Pressure peak followed by high frequency combustion instability lasting for 4 s

• Combustion chamber overheats and MMH in regenerative cooling system starts to boil

• Reduced MMH flow rate leads to overconsumption of nitrogen tetroxide

• Increased thermal flux due to off-design mixture ratio punctures chamber cooling lines

• Propellant loss decreases thrust by 20 %, engine shut down after 904 s (planned: 980 s)

• Lower orbit than expected (orbit of ARTEMIS restored using its ion propulsion system)

Image source: Chemische Raumfahrtantriebe – Oberstufen, Begleitmaterial zur Vorlesung WS 2006/2007, Institut für Raumfahrtsysteme, Universität Stuttgart

Slide 5


Introduction

Central question

What was the reason for the fast pressure rise in the combusti on chamber?

• Propellant thermodynamics?

• Flow dynamics (is preflow phase long enough, ...)?

• Combustion chemistry (pre-ignition reaction products, nitric acid, ...)?

• Pre-ignition accumulation of propellant (condensation, ...)?

• Dynamic coupling of internal hydraulic circuits and supply lines?

• Pressure dependence of mixture preparation (pressure-swirl type atomizers)?

Slide 6


Introduction

Project framework

AESTUS malfunction on ARIANE 5 flight 142

Inquiry board report

AESTUS complementary CQ kick-off meeting, Ottobrunn

AESTUS HF workshop meeting, Roissy

Workshop on droplet vaporization & breakup, Ottobrunn

Fuel dome analysis (J. Steelant / ESTEC)

Combustion chamber preflow analysis (R. Schmehl / ESTEC)

Continued

SMART code development (EADS-ST)

TRP Multiphase Flow Models (ONERA)

Space Launcher Liquid Propulsion, Liege

ICLASS 2003, Sorrento

AIAA-JPC, Huntsville

Space Propulsion 2004, Sardinia

07 08 09 10 11 12 01 02 03 04 05 06 07 08 09 10 11 12 01 02 03 04 05 06 07 08 09 10 11 12 01 02 03 04 05 06 07 08 09 10 11 12 01 02 03 04

2002 2003 2004 2005

AIAA-JPC, Fort Lauderdale

Slide 7


Upper stage ignition

AESTUS engine fact sheet

• Hypergolic propellants MMH/N2O4

• Multiple re-ignition in vacuum

• Regenerative cooling by MMH

• Multiple point injection

• Engine dry mass: 1.2 t

• Total propellant usage: 10 tons

• Vacuum thrust: 3 tons

• Tank pressure: 1.8 MPa

• Chamber pressure: 1.1 Mpa

• Chamber temperature: 3000 K

Slide 8



Physical phenoma during preflow

Flash-atomization of liquid oxidizer ........................Vapour phase dissociationFlash-evaporation of spray dropletsSpray-wall deposition / evaporationTransient chamber wall heating

Secondary droplet breakup

Homogeneous nucleation + condensation

Slide 9



Purpose of oxidiser preflow

167 ms

178 ms

187 ms

194 ms

Contact ignition in model combustorLecourt & d’Herbigny (2002)

0 50 100 150 2000

50

100

150

200

250

∆t i

[ms]

p [kPa]

Pressure dependence of ignitiondelay of MMH/N2O4 mixture atT = 300K

• Preflow pressure level of p = 28kPa limits ignition delay to∆ti < 150ms

• Avoids excessive accumulation of propellants in enginestart-up phase

• Stable ignition of engine (no hard start)

Slide 10



Basic thermodynamic analysis

200 250 300 350 400103

104

105

106

107

T [K]

p[P

a]

s

l

g

N2O4 phase diagram

Storage

Chamber

Oxdome

SubcooledvapourSuperheated50 µm-droplet

Storagep = 1.8MPaT0 = 300Km = 9.5kg/s

Chamberp = 28kPaTb ≈ 269K

p→ 0Pa

Tw ≈ Tb

Global enthalpy balance:

hl (T0) = α hg (Tb) + (1−α) hl (Tb) => α ≈ 13.7% evaporated N2O4 in chamber flow

Slide 11


Propellant properties

Dissociation of nitrogen tetroxide

260 280 300 320 3400

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

T [K]

Mol

esof

N2O

4di

ssoc

iate

d

500

100

28

10

1

p [kPa]

preflow conditions

Endothermic dissociation reaction

N2O4⇋ 2NO2 , ∆h0r,g = 57120

Jmol

Equilibrium constant

Kp =p2

NO2

pN2O4=

X2NO2

XN2O4p =

4ξ2

1− ξ2p

logKp = −2692

T+1.75logT +0.00483T −7.144·10−6T2

+3.062

Slide 12



Constant property data

Property Symbol N2O4 NO2 Unit References

Molar mass M 0.0920160 0.046008 kg/mol Schley (1988), Dadieu et al (1968)

Critical temperature Tc 431.35 431.4 K Schley (1988), VDI-Wärmeatlas (1991)

Critical pressure pc 99.299e5 101.3e5 Pa Schley (1988), VDI-Wärmeatlas (1991)

Special gas constant Rs 90.358 180.71661 J/(kgK) Schley (1988), VDI-Wärmeatlas (1991)

Diffusion volume∑

V 33.3 16.65 − VDI-Wärmeatlas (1991)

Boiling temperature Tb,1bar 294.25 294.15 K VDI-Wärmeatlas (1991)

Enthalpy of vaporization hv,1bar 414000 314000 J/kg VDI-Wärmeatlas (1991)

Standard formation enthalpy ∆h0f ,l −19560 J/mol NIST Chemistry WebBook (2003)

Standard formation enthalpy ∆h0f ,g 9080 33100 J/mol NIST Chemistry WebBook (2003)

Acentric factor ω 0.843 0.834 Schley (1988)

Acentric factor for SRK eq. ωS RK 0.8573 0.8634 Reid et al. (1987)

Rackett constant ZRa 0.3665 0.2413 Reid et al. (1987)

Critical real gas factor Zc 0.4629 0.473 Schley (1988), Reid et al (1987)

Dipole moment m 0.55 0.4 Debye Dadieu et al (1968), Reid et al (1987)

Characteristic length σ 4.74 3.90 Å Coffin and O’Neal (1958)

Characteristic energy ε/k 383 230 K Coffin and O’Neal (1958)

Slide 13



Variable property data

260 280 300 320 340 360 3801250

1500

1750

2000

2250

2500

2750

3000

3250

T [K]

c p,l

[J/(k

gK)]

VDI97 N2O4VDI97 NO2Dadieu68 N2O43rd-order polynomialShomate equation

Liquid heat capacity

• 3rd order polynomial accounts for

dissociation

260 280 300 320 340 3600.08

0.09

0.10

0.11

0.12

0.13

0.14

0.15

T [K]

λl[W/(m

K)]

Dadieu682nd-order polynomial

Liquid thermal conductivity

Slide 14




200 250 300 350 400 450 500-400

-300

-200

-100

0

100

200

300

T [K]

h l[k

J/kg

]

JANAF714th-order polynomialIntegrated Shomate eq.

Liquid Enthalpy

260 290 320 350 380 4100

1

2

3

4

5

T [K]

p va

p[M

Pa]

Dadieu68Antoine equationKolle

Liquid-gas vapor pressure

Slide 15




250 300 350 400 45050

100

150

200

250

300

350

400

450

T [K]

∆h v

[kJ/

kg]

VDI97h−hl 4th-ord. pol.Wright

Heat of vaporization

• Correlation by Wright accounts for

reaction energy of dissociation

260 280 300 320 3400.015

0.020

0.025

0.030

0.035

T [K]

σ[N/m

]

Dadieu68Tomkins91Macleod and Sugden2nd-order polynomial

Surface tension

Slide 16




280 320 360 400 440 480 5201.0

1.5

2.0

2.5

3.0

3.5

4.0

T [K]

ρ[k

g/m

3 ]

Tomkins91Tabachnikov70Ideal gas N2O4Ideal gas NO2

Gas density

200 400 600 800 1000400

600

800

1000

1200

T [K]

c p[J/(k

gK)]

VDI97 N2O4VDI97 NO2Dadieu68 N2O43rd-order pol. N2O43rd-order pol. NO2

Gas heat capacity

Slide 17




250 300 350 400 450 5001E-05

2E-05

3E-05

T [K]

µ[k

g/(m

s)]

AirLiquide762nd-order polynomial

Gas dynamic viscosity

250 350 450 550 6500.00

0.04

0.08

0.12

0.16

0.20

T [K]

λ[W/(m

K)]

Dadieu68AirLiquide76Bilyk74VDI97 NO2linearlinear CNES

Gas thermal conductivity

• Data by Bilyk (1974) accouts for re-

action energy of dissociation

Slide 18




250 500 750 10000

100

200

300

400

500

600

700

800

900

T [K]

h[k

J/kg

]

JANAF714th-order polynomial

Gas enthalpy

Conclusions:

• All relevant thermopysical property data

available

• Data covers mechanical and thermal

flow phenomena

• Data also accounts for spontaneous dis-

sociation

Slide 19


Computational approach

Iterative Euler-Lagrange method

Vapour flow field• p,u,v,w,h,k, ε

Spray source terms• S md,S ud,S vd,S wd,S hd

Finite volume method• 50850 finite volumes• k-ε turbulence model• 100solver iterations/cycle• compressible SIMPLEC

Droplet tracking method• Stochastic initial conditions• Stochastic dispersion model• 70000 trajectories/cycle

Liquid wall deposit• No transport

General transport equation:

aφPφP =∑

nb

aφnbφnb+S Cφ +S φd , φ = p′,u,v,w,h,k,ε

Spray source terms:

S m,d =

N∑

k=1

fk(

mind −mout

d

)

= S p′,d

S φ,d =N∑

k=1

fk(

mind φ

ind −mout

d φoutd

)

, φ = u,v,w,h

Slide 20


Computational approach

Treatment of spray source terms

S φd = S Pφd φ + S C

φd

• S Pφd < 0 : Subtract S P

φd from aφP and add S Cφd to right hand side of transport equation (implicit treatment)

• S Pφd > 0 : Add full source term S φd to right hand side of transport equation (explicit treatment)

φ0φ∗

S φd

S Cφd

φ

SS φd(φ)

S φd(φ)

S Pφd

1

Linearization scheme

450 460 470 480 490 500 51010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

Cumulative solver iterations /100

||R/R

ref||

p′-Systemh-System

S φd updated every 100 iterations S φd constant

Residual history of Euler-Lagrange method Slide 21


Atomization model

Spray visualization

N2O4 atomization at 0.1 MPa N2O4 flash-atomization at 20 kPa

Image source: Lecourt & d’Herbigny: MMH/NTO Injection and Ignition in Vacuum Downstream from an AESTUS Single Injection Element, 4th International

Conference on Launcher Technology "Space Launcher Liquid Propulsion", Liège, Belgium, 2002

Slide 22


Atomization model

Single injector

θmax

0 100 200 30

D63 D32

50 31.2

100 62.4

150 91.7 Dro

plet

volu

me

D [µm] 100 200 300

Laser light sheet visualization Trajectory model, θ = N(µ,σ) Initial droplet size distribution

• Initial trajectory angle θ from clipped normal distribution using µ = 0◦, σ = 45◦ and θmax = 50◦

• Initial droplet velocity cd,0 = 20m/s derived from jet exit velocity

• Initial droplet size D0 from Rosin-Rammler distribution with fixed width parameter n = 2.4

• Parameter study on diameter parameter D63

Slide 23


Atomization model

Injector array on baseplate

70 individual injectors

20 droplet size classes

50 stochastic samples

70000 trajectories per spray computation

Representative trajectories originating

from central injector

Slide 24


Flash-evaporation model

Extension of classical D 2 theory

mvap

mvaph(T )

4πr2λdTdr

Td

Ts ≤ Tb(p)

Tg, p

Qi

• Quasisteady vapor phase

• Spherical symmetric transport

Net energy flux in ambient vapor:

Q = mvap h(T ) − 4πr2λdTdr, rd ≤ r <∞

Energy balance of droplet:dHd

dt= md cp,l

dTd

dt− mvap hl(Tb) = −Q

Superheat energy flux provided by droplet:

Qi = 4πr2d αs (Td −Tb)

Flash evaporation rate:

mvap, f =Qi

∆hv(Tb)

Slide 25



Model equations

Total evaporation rate (implicit formulation):

mvap = 2πrd Nu∗λre f

cp,re fln

1+BT

1−mvap, f

mvap

, BT =cp,re f (Tg−Tb)

∆hv

Convective correction (Frössling 1938, Aggarwal & Peng 1995):

Nu∗ = 2 + 0.552 Re12 Pr

13 , Re= ρ∞crelD/µre f , Pr= µre f cp,re f /λre f

Model balance equations:

dmd

dt= −mvap ,

dTd

dt=

[

mvap − 4πr2dαs

cp,l

]

Td −Tb

md

Slide 26



Empirical heat transfer coefficient

0 10 20 30 40 500

10

20

30

40

50

60

∆T [K]

αs

[kW/(m

2K

)]

αs,minD = 5µm

D = 10µmD = 100µm

0 3 6 9 12 15 18268

272

276

280

284

288

292

25

50

100150

D0 [µm]

TdTbT∞

t [ms]

T[K

]

Adachi et al (1997), Zuo et al (2001):

αs =

760∆T0.26 , 0 ≤ ∆T ≤ 5 ,

27∆T2.33 , 5 < ∆T ≤ 25 ,

13800∆T0.39 , 25< ∆T

Physical lower limit (size-dependent):

αs,min = λl/rd

Slide 27


Secondary spray effects

Aerodynamic droplet breakup

Low relative velocities

Free oscillations

Forced deformations

Moderate to extreme relative velocities (top to bottom)

Bag breakup

Bag-plume breakup

Shear breakup

Catastrophic breakup

Slide 28



Trajectory simulation

• Reduced droplet size spectrum

• Increased spray dispersion

• Intensified spray evaporation

Bag breakup D0 = 400µm 13<We< 18

Slide 29



Droplet-wall interaction

0 0.02 0.04 0.06 0.08x [m]

Deposition at Tw < T ∗w, Re< 24La0.419:

Splashing at Tw < T ∗w, Re> 24La0.419:

Nucleate boiling at T ∗w < Tw < T ∗L:

Reflection at T ∗L < Tw:

Droplet splashing on chamber wall at Tw = Tb Interaction mech anisms

• Majority of droplets is still superheated upon wall contact

• Chamber wall temperature will drop rapidly once spray impingement occurs

• Remaining superheat energy of droplet, mdcp,l(Td −Tb), consumed immediately by vapourisation

Slide 30


Results

Two-phase flow field

Simulation

parameters

min j 9.5kg/s

Tin j 292K

D63 100µm

n 2.4

αrelaxation 3%

Ncoupling 500

tCPU 14days

200 210 220 230 240 250 260 270 280

M=1

T [K]

0 10 20 30 40 50 60 70 80

D32[µm]

Slide 31


Results

Vapour temperature distribution

280

270

260

250

240

230

220

210

200

T [K]

Slide 32


Results

Sauter Mean Diameter distribution

80726456484032241680

D32 [µm]

Slide 33


Results

Spray deposit on chamber and nozzle wall

0 0.1 0.2 0.3 0.4 0.5 0.60

0.1

0.2

0.3

x [m]

mN

TO,l

[kg/

s]

Cylindrical part Convergent part Total deposit Total injection

m [kg/s] 2.273 2.534 5.155 9.500

m [kg] after 160ms 0.364 0.405 0.825 1.520

Slide 34


Results

Effect of injection temperature

275 280 285 290 295 300260

265

270

275

280

285

Tstat @ thermocouple TTC12

Simulation - equilibrium Tw ≈ Tstat

Simulation - isothermal Tw = Tin j

Comparison indicates cooling of chamber wall

surface during preflow from Tin j to Tstat

Tst

at[K

]

Tin j [K]Slide 35


Results

Temperature drop in chamber

250 260 270 280 290 3000

0.01

0.02

0.03

0.04

0.05

0.06

Tstat @ thermocouple TTC12pstat @ pressure sensor PT12

Tstat

Tin j

T [K]

p sta

t[M

Pa]

Slide 36


Results

Transient evolution of the spray

Isosurfaces of liquid volume concentration vc = 1%

t = 5ms

10ms

15ms

20ms

Slide 37


Results

Evaporation transfer function

0 5 10 150

1

2

3

4

5

6

7

8

9

10

11

12

13

14

mev

ap/m

inj[%

]

t [ms]

Injection temperature controls initial flash-evaporation of liquid

Tin j = 274K

D63= 100µm

280 K

290 K

300 K

Slide 38


Results

Mean droplet size along axis

0 0.1 0.2 0.3 0.4 0.5 0.60

10

20

30

40

50

60

70

80

90

100

D63,0 = 50µm

100µm

150µm

Size reduction due to

secondary breakup

x [m]

D32

[µm

]

Slide 39


Results

Effect of initial droplet size variation

50 60 70 80 90 100 110 120 130 140 1500.021

0.023

0.025

0.027

0.029

0.031

p sta

t[M

pa]

D63,0 [µm]

Secondary effectsNo secondary effects

50 60 70 80 90 100 110 120 130 140 150263

264

265

266

267

268

269

270

271

Tst

at[K

]

D63,0 [µm]

Secondary effectsNo secondary effects

Slide 40


Results

Evaporation transfer function

0 5 10 150

1

2

3

4

5

6

7

8

9

10

11

12

13

14

mev

ap/m

inj[%

]

t [ms]

D63,0 = 150µm

D63,0 = 100µm

D63,0 = 50µm

Tin j = 292K

Slide 41


Results

Effect on vapour temperature distribution

D63,0 = 150µm

200 210 220 230 240 250 260 270 280

M=1

T [K]

D63,0 = 100µm

M=1

D63,0 = 50 µm

M=1

Slide 42


Results

Effect on droplet size distribution

D63,0 = 150µm

0 10 20 30 40 50 60 70 80

D32=30µm

D32[µm]

D63,0 = 100µm

D32=30µm

D63,0 = 50 µm

D32=30 µm

Slide 43

Dr.-Ing. Roland SchmehlPropulsion and Aerothermodynamics Division Summary and conclusions

1. Validated 3D-CFD methodology for low-pressure preflow regi mes

- Extensive physical modelling framework

- Iterative Euler-Lagrange methodology

2. Two-phase flow field and wall deposition analyzed

- Thermodynamic conditions in chamber close to equilibrium

- Considerable accumulation of liquid oxidizer next to base plate

3. Highly accurate transfer functions for system level analys is

- Dynamic modelling

- Coupling with extended system

4. Analysis applicable to a variety of bipropellant systems

AESTUS II S400-20 S400-1 S22-02 AVUMSlide 44

Dr.-Ing. Roland SchmehlPropulsion and Aerothermodynamics Division Vacancy at ESTEC-ESA

What: ESA Internal Research Fellowship

Where: Propulsion and Aerothermodynamics Division, ESTEC-ESA, Noordwijk

When: ASAP

Duration: 2 years

Topic: Combustion modelling with emphasis on ignition delay

Who: PhD researchers (with or without final degree)

Contact: Roland [email protected]@propulsion.esa.int

Slide 45

Documents

Computational analysis of the preflow phase during start-up …rschmehl.home.xs4all.nl/CV/presentations/wsa07_prese… · · 2009-05-17• Chamber pressure in cryogenic Vulcain