Heterogeneous catalysis effects in Mars Heterogeneous catalysis effects in Mars entry problementry problem

Valery LValery L. . KovalevKovalevMoscow State UniversityMoscow State University, , RussiaRussia

ERICE-SICILY:1-7 AUGUST 2005ERICE-SICILY:1-7 AUGUST 2005

Schematic of flow field with catalytic recombination, excited state production and quenching.

Calculated flux to MESUR spacecraft with various catalytic boundary conditions.

THREE TYPES OF SILICONIZED COATING MATERIALS

Coating I : the glassy coating of the <<Buran>> orbiter tile heat shield based on the SiO2 - B2O3 - SiB4 system

•Coating II: an oxidant — resistant carbonaceous coating based on alumina borosilicate glass with a MoSi2 admixture

•Coating III: a coating made up of a new composite material based on the Hf — Si — С — В system.

Nonequilibrium jet from plasmatron flowing around butt-end probe (Mach number)

Experimental regimes

Parameters 

Regimes 

1 

2 

3 

4 

5 

6 

Te, К 

3320 

4360 

5800 

6256 

6600 

6875 

Vs, m/s 

47,3 

76,1 

105,6 

118,0 

145,0 

164,0 

qfcW, Wt/cm2

 

4 6,4 

74,4 

103,7 

130,0 

175,0 

208,0 

N, kWt 

29 

37 

44 

52 

64 

72 

p, Pa 

10,5 

17,5 

24,5 

26,2 

33,75 

38,8 

CATALYTIC MECHANISM

chemical adsorption and desorption atoms

1. O + SV OS

Eley — Riddel reactions

2. OS + O SV + O2

3. OS +CO SV+ CO2

physical adsorption and desorption

4. О + FV Of,

diffusion to the nearest chemisorptions site

5. Of + SV ОS + FV

Lengmuir — Hinshelwood recombination

6. Of + OS O2 + FV + SV,

7. OS + OS O2 + 2 SV

MASS RATES OF SPECIES FORMATION IN HETEROGENEOUS CATALYTIC REACTIONS

j j j j

IR LH PhA A A AR R R R

Elementary rate coefficients

13 1

/ 4

exp( / ), 8 ,

4 exp( / )

10 ( 5 6), ( 7

m vi i

mi i

f sm m v v vi i i

j j j

m vDm Dm

mDm Dm D

k v N adsorbtion and Eley Reidiel reactions

k D Langmuir Hinshelwood reactions

A E RT v kT M N is N or N

k k K

D N E RT

c reactions and C v reaction

10 1 20 2 18 2

)

2,2 10 , 10 , 5 10f sv vDC m N m N m

DETERMINATION OF THE MODELPARAMETERS

SIMPLIFYING ASSUMPTIONads = const (1); Q (A-S) = QS (2)

VALUES OF THE MODEL PARAMETERS (Reaction 1-3)

 Curve

 a1

ER

 

 a3

ER

 

 a4

ER

 

 5

 

 7

 

 EO

ad

 ECO

ad

 E1

ER

 E3

ER

 

 E4

ER

 a 

0.015 

0.015 

0 

0.025 

0 

300 

0 

25 

15 

0 

b 

0.038 

0,038 

0 

0.025 

0 

280 

0 

25 

15 

0 

с 

0.018 

0.018 

0 

1.0 

0 

280 

0 

15 

10 

0 

d 

0.038 

0,038 

0.038 

0.025 

0.013 

280 

280 

25 

15 

25 

Coating II 

0.013 

0.016 

0 

0.016 

0 

380 

0 

20 

25 

0 

Coating III 

0.042 

0.042 

0 

0.025 

0 

400 

0 

10 

25 

0 

The r.m.s. deviation of the calculated heat fluxes from the measured ones did net exceed 5 %.

Temperature dependence of the heat fluxes to coating I at stagnation point

Temperature dependence of the effective coefficients of heterogeneous recombination for

coating I

Temperature dependence of the effective coefficients of heterogeneous recombination for

coating III

Experimental regimes

Parameters 

Regimes 

1 

2 

3 

4 

5 

6 

Te, К 

3320 

4360 

5800 

6256 

6600 

6875 

Vs, m/s 

47,3 

76,1 

105,6 

118,0 

145,0 

164,0 

qfcW, Wt/cm2

 

4 6,4 

74,4 

103,7 

130,0 

175,0 

208,0 

N, kWt 

29 

37 

44 

52 

64 

72 

p, Pa 

10,5 

17,5 

24,5 

26,2 

33,75 

38,8 

N Reaction A E Q Ref.

1 

O + SV OS

 

0,025 

0 

300 

[1] 

2 

.OS + O SV + O2

  

0,015 

25 

_ 

_ ,, _  3

 OS +CO SV+ CO2 0,015

 15 

_ 

_ ,, _ 

4 О + FV Of

  

0,5 

0 

20 

[2,3] 

5 

Of + SV ОS + FV

 

0,053 

0 

_ 

_ ,, _ 

6 

Of + OS O2 + FV + SV

 

0,053 

0 

_ 

_ ,, _ 

7  

OS + OS O2 + 2 SV

   

0,02 125 _ [4]

1,0 

500 

_ 

[5] 

Reactions with physical adsorptionatoms and model parameters

Heat fluxes on the surface taking into account processes with physical adsorbed atoms

Temperature dependences of effective

recombination probability of oxygen atoms

Heat fluxes on the surface taking into account the recombination of carbon atoms

Mini-probe forebode configuration and computational domain

Mole fraction CO2 distribution Temperature distribution. H = 51.84 km, (sizes on Figure are indicated in cm)

Free stream entry conditionsH, km 

V, m/s 

P, kg/m3

 T, К 75.92

 5800 

3.0110-6

 129 67.89

 5791 

9.5110-6

 130 59.87

 5769 

2.8910-5

 134 51.84

 5690 

8.3710-5

 140 43.82

 5536 

2.2710-4

 148 36.79

 5172 

5.8110-4

 158 28.95

 4539 

1.2310-3

 167 23.16

 3471 

2.2710-3

 174 17.89

 2549 

3.8410-3

 182 

Flight altitude dependence of the heat fluxes to different coatings at the stagnation point for

the Mars miniprobe

MARS miniprobe surface equilibrium temperature along the trajectory for different

coatings

Configuration of space vehicle MSRO

R b

R c

1

2 3

40

60 o

R n

L c

R s

Р и с. 1 . К о н ф и гу р а ц и я к о см и ч еск о го а п п а р а т а

The distribution of heat fluxes across the frontal

surface of MSRO

0 0.4 0.8 1.2 1.6 2S , м0

10

20

30

40

50

q w , В т/с м 2

1

3

4

2

Р и с . 2 . В л и я н и е г е т е р о г ен н ы х к а т а л и т и ч ес к и х п р о ц е с со в н а т еп л о в ы е п о т о к и к т еп л о з а щ и т н о м у э к р а н у

The distribution of heat fluxes across the bottom surface of MSRO

0 1 2 3S, м

0

1

2

3

q w , Вт/см 2 4

3

2

1

Р и с. 3 . В л и я н и е к ат ал и т и ческ и х свой ст в п о вер х н ост и н а т еп л о вы е п от оки к к о р м овой ч аст и ап п ар ат а

Surface equilibrium temperature across the bottom surface of MSRO

0 1 2 3S , м

200

400

600

800

1000

T w , К4

3

2

1

Р и с.4 . Р асп р едел ен и я р авн овесн ой р ади ац и он н ой т ем п ер ат у р ы к ор м овой ч аст и ап п ар ат а

Effect of physical adsorption for the bottom surface of MSRO

0 1 2 3S , м

0

0.2

0.4

0.6

0.8

1

qw , В т/см 2

1

2

5

2

Р и с.5 . Р асп р едел ен и я т еп л овы х п от ок ов к п овер х н ост и к ор м овой част и ап п ар ат а б ез у ч ет а ( к р и вая 2 ) и с у ч ет ом ( к р и вая 5 ) ф и зи ч еск ой а дсор б ц и и ат ом ов к и сл ор ода

Summary• On the basis of the Langmuir layer theory, a model of the

interaction of dissociated carbon dioxide mixture with a catalytic surface is developed. This model takes into account both chemical and physical adsorbed atoms.

• Comparison of the calculated heat fluxes with measured ones show that the model is able to predict heat-transfer in a wide temperature range, from 300 up to 2000 K.

• The performances of the ciliconized coatings are compared for the entry conditions of Mars Miniprobe and MSRO. The results obtained show they could be used in the thermal insulation system of the vehicle.

• It is established, in particular, that using the glassy coating of the <<Buran>> orbiter tile heat shield would result in a 2.5-fold reduction in the maximum heat flux to the vehicle nose along the entire trajectory as compared with an ideal catalytic surface and in a reduction of the maximum surface temperature could be 500 K.

Literature

1. Kovalev V.L., Afonina N.E., Gromov V.G. Catalysis Modeling for Thermal Protection Systems of Vehicles Entering into Martian Atmosphere. AIAA Paper 2001 - 2832. 2001.

2. Kim Y.C., Boudart M. Recombination of O, N, and H on Silica: Kinetics and Mechanism, Langmuir 1991. 7. 2999 -3005

3. Gordiets B.F., Ferreira C.M. Self-consistent modelling of volume and surface processes in air plasma. AIAA Paper 97 -2504. 1997.

4. Daiss A., Fruhauf H.H., Messerschmid E.W. Modeling of catalytic reactions on silica surfaces with consideration of slip effects. J. Thermophysics and Heat Transfer. 1997. 11, N 3, 346-352.

5. Nasuti F., Barbato M., Bnmo C. Material — dependent catalytic recombination modeling for hypersonic flows. J. Thermophysics and Heat Transfer. 1996. 10. N 1. 131-136.

6. Bykova N.G., Vasil’evskii S.A., Gordeev A.N., Kolesnikov A.F., Pershin I.S., Yakushin M.I. Determination of the Effective Probabilities of Catalytic Reactions on the Surface of Heat Shield Materials in Dissociated Carbon Dioxide Flows, Fluid Dynamics, Vol.32(1997), No.6, pp.876-886.

7. Kolesnikov A.F., Pershin I.S., Vaail'evskii S.A., Jakushin M.I. Study of quartz surface catalycity in dissociated carbon dioxide subsonic flows. AIAA Paper 98-2847. 1998.

Flight altitude dependence of the heat fluxes to coating I at the stagnation point for Mars

Miniprobe

Heat fluxes on the surface with the Langmuir-Hinshelwood recombination