Research on smoke control in underground structures

Research on Smoke Control in Underground Structures H. Nakamura, T. Yamana, T. Matsushita, T. Wakamatsu and T. Wakamatsu

A b s t r a c t - - T h e purpose of the research described in this paper is to test smoke movement, to study the efficiency of smoke control by air control around the fire origin, and to determine control methods to protect evacuation zones from smoke. The four steps required to accomplish these aims are: (1) construction of mathematical models that describe the horizontal movement of smoke, the propagation velocity and heat loss of smoke; (2) a comparison between the mathematical models and full-size and scale models of an underground corridor; (3) a comparison between different ventilation systems and positions of fire origin in a scale model of an underground structure; and (4) simulation of the smoke movement of the underground structure using a one-layer zone model. A simulation model for evaluating the safety of underground structures is also proposed.

1. Introduction he ability to predict smoke movem e n t accurately is vital in planning fire safety in underground structures. Smoke m o v e m e n t and the efficiency of smoke control systems are not fully understood because of a general lack of experience with fires in u n d e r g r o u n d s t r u c t u r e s , combined with insufficient experimentation in this area. The ultimate goal of this study is to evaluate the fire safety of underground structures using simulation techniques on scale models of the underground structures. As the first step toward this goal, this research study aimed to test smoke movement and the efficiency of smoke control by air control around fire origins; and to define control methods for protecting evacuation zones from smoke. To accomplish these ~imA, the following steps have been taken: 1. Mathematical models have been constructed t h a t describe the horizontal movement, propagation velocity and heat loss of smoke.

T

Present address: Hiroyuki Nakamura, Research Eno~aeer, Construction Engineering Research Department, Institute of Technology, Shlmlzu Corpora-tion, 4-17, Etchujima 3-chome, Koto-lm, Tokyo, Japan.

mouvement de la f u m ~ d'~.dier l"effieaci~ d"un syst~me de c o n t r ~ cle fumg~e, par contr~le de l~dr aux enuirons de l'origine de l ' ~ et de ddterntiner des ra~thodes de contrSle poar prot~er les zones d'~vacuation. Les quatre c ~ e s ru~essalres pau r accomplir ~ s objeetifs sent les suivan~ : (1) construction de ~ m a t ~ qui ~ le mouvement horizontal de la f u m ~ la vitesse de propagation et la dissipation de chaleu r de la f u m ~ ; (2) une ~ n entre les mod~ les mat ~ m t b t u e s ainsi que les mod$1es a l'&heUe et en dimensions r ~ i e s d'un couloir seuterrain," et (3) une comparaison entre di~rvUs ~ de ventilation et positions d'origine de l'invendie darts un m o d ~ d l'&heUe d'une ~ souterralns; et (4) simulation du mouvement de f u m ~ dans un mod~le de stracture souterralns ne comportant qu'un seul nioeau. Un mo~ledesimalationpoarL, v a t u e r l a s ~ a r i t ~ d e s ~ s o u ~ ' m i n e s e~t aussi propas~ dans ce rapport.

Symbols a: b: g: h: h~ ua: q:

acceleration (in/s ~) width of corridor (m) acceleration of gravity (m/s 2) thickness (m) thickness of ceiling jet front (m) propagation velocity of ceiling jet front (m/s) heat loss to ceillng and walls (kJhn2s) area which the jet contacts with the ceiling and walls (m2) Cp: specific heat of air (kJ/kgK) Fb: buoyancy force (kgm/s =) Fi: force of inertia (kgm/s=) Fr: Froude number L: length (m) M~ m a ~ flow rate at the front (kg/s) Mo: mass flow rate at the inlet of the ceiling jet (kg/s) AP: pressure difference of the two fluids (Pa) Q: mass flow rate To: temperature of the ceiling jet at the inlet (°(2) T: temperature of the ceillng jet ('12) T: temperature of the ceiling and walls (*C) V: velocity (m/s) Vo: volnrnetric flow rate at the inlet of the ceil;-gjet (mVs) V: volume of the ceiling jet (ms) a: heat transfer coefficient (kca]/mzh~C) p: density fkg/ms) Po: density in the ceillng jet at the inlet of the esillng jet (kg/m3) p~ density at the ceiling jet front (kg/ms) p.: density in the ceiling jet (kg/ms) Ap: difference in density between the fluid adjacent to the jet and jet fluid (kg/ m s) Subscripts:

F: M:

Tunnellingand UndergroundSpace Technology,Vol. 7, No. 4, pp, 325-333, 1992. Printed in Great Britain.

P,A s ~ ' o b j e c t / T d e ta rseherehe d~cr/t darts ce rapportest de tester/e

Full scale Scale model

0886-7798/92 $5.00 + .00 Pergamon Press Ltd

325

Me=

Mo :~ Figure 1. A model of a ceiling jet front under the ceiling. 2. The mathematical models have been compared with full-size and scale models of an underground corridor. 3. Different ventilation systems and different positions of fire origin in a scale model of an underground structure have been compared. 4. Smoke m o v e m e n t in an underground structure has been simulated using a one-layer zone model.

2. The distribution ofvelocity in the ceilingjet is unlforn~ 3. The density in the ceiling jet is homogeneous. 2.2. Mathematical Model for the Propagation Velocity of a Ceiling Jet If we assume t h a t the pressure difference depends only on the density, the pressure difference is: AP = Apgh (2) Thus, the propagation velocity at any depth is given by eqs. (1) and (2): Uf = (2Apgh/ps) ys

=

p~ I he(2Apg/p,)~2hmdh

=

pr (2/3)b (2Apg/p,)mh~

(4)

If the thickness of the jet does not change rapidly, it can be assumed t h a t mass flows between the front and at any other section of the jet are almost equal. By the assumption above, the thickness of the front is: h r = (3/2) ~ (2Apg/p,) -'3 (p~)-~ M02~ = (3/2) ~ (2Apg/p,> -'s (p/pr" Vo/b) ~ (5) The m a x i m u m propagation velocity at the front is:

Ur~,~

= (2apgh/p,) ua

2. Constructing Mathematical Models for Smoke Movement 2.1. Mathematical Model for a Ceiling Jet Figure 1 shows a model of a ceiling jet front u n d e r the ceiling. To construct a mathematical model, the following assumptions were made: 1. The relationship between a pressure difference with ambient air and the propagation velocity of the ceiling jet front is: p U2/2 = A P (1)

prb I heu~lh

= {2Ap g(3/'2 )'~

(2..,,~og/p,,) ~

= a N(kpg/p

Mo/pb) m

(Mgpzb):~/p,} ~

= 1.44 ( k p g / p Mffpb) m

(6)

2.3. Effect of Heat Loss to Ceilings and Walls During Propagation The effect of a density change resulting from heat losses to the ceilings and walls during smoke propagation m u s t be considered. To calculate the effect, the following assumptions are made: 1. An average smoke density of the entire ceiling jet is employed. 2. Heat losses to the ceiling~and walls are: q = a(T- T) (7) 3. The temperature of the ceiling and walls is constant. 4. The jet exhibits non-compressible flow. Heat and mass balance for the entire jet are given by eqs. (8) and (9), respectively.

(3)

and m a s s flow in the front is:

d ( p ' V)/dt = PoVo d(Cp

p

V

(8)

T ) at = CppoV0Wo- q A

Therefore, the average smoke density is: C p p V dTJdt = C p p o V o ( T 0 - T ) / - A a ( T - T , )

(9) (10)

: The section used for the tests

The full scale underground corridor (section) £e

The full scale underground corridor (plan)

:II'!'I

Manhole "3"

Movablerake of anemometers

I

"B" staircase 200~ - 12000 r"

II

3O0 2

° )0

3 40.000

o : C-C thermocouples(9x20)

,,, : optical s m o k e d e n s i t y ( 2 x 2 , 3 x 1,4×2)

• : h o t - w i r e a n e m o m e t e r (8)

1

The sensor positions

Figure 2. Plan, section of the full-scale underground corridor and layout of the sensors in the corridor.

326 ~ L ~ G

ANDUNDEP,~ROUNDSPACETECHNOLOGY

Volume 7, N u m b e r 4, 1992

50

Table I. Test condition. Volumetric Flow Rate at the Inlet of the Ceiling Jet (I/s)

45 Temperature of the Ceiling Jet at the Inlet (°C)

Vo

T.

360 360 360

43 56 66

250 250

50 65

U

u. 40

as 30~" 2520-

lb 2b 3b The distance from the inlet [m]

4/D

Figure 3. Temperature decreasing in the ceiling jet from the inlet.

the ceiling jet and the distance from the inlet of the jet. The temperature in the jet decreases as the distance from the inlet increases. Figure 4 shows the same relationship as Figure 3, but differs with the time aRer the inlet was started. From the circles in Figure 4, it can be seen that propagation velocity decreases as the distance from the inlet increases. Figure 5 shows the relationship between the jet te~nperature and the time at theV o= 0.36 (mS/s). The white morks in Figure 5 indicate the distance covered by the jet front at various incrementa of the jet temperature. The black marks indicate the distance covered by the thermocouple rakes. The propagation velocity of the jet front by observation agrees well with the velocity sensed by the thermocouples. The gradient shows the degree to which the velocity is increased as the temperature and V o are increased.

3. S m o k e S p r e a d T e s t s a n d T e s t Results

3. I. Full-Scale Tests in an Underground Corridor F i g u r e 2 shows t h e full-scale underground corridor layout for the ceilingjet and the sensors, which monitor smoke temperature (by C-C thermocouples), density (by optical smoke density) and velocity (by hot-wire anemometer). A series of tests were carried out using the section between the "B ~ staircase and the hall in the corridor. The smoke emanates from a smoke generator (called a "smoke jet") placed in the "B" staircase. The generator can produce smoke having almost the same properties as real fire smoke, and can control the smoke temperature, the flow rate, and the outlet velocity. The outlet of the generator (or inlet to the corridor) was placed under the ceiling at the end of the corridor; the inlet is 120 cm wide and 30 cm deep. The jet from the outlet would h a v e r e c t i l i n e a r velocities produced by a rectifier installed in the outlet. Table 1 shows the temperature of the ceiling jet at the inlet (To) varying with different volumetric flow rates at the inlet of the ceillng jet (Vo).

U P

~

(14)

QM/QF = (LM/LF)~

(15)

3.4. Results of the 12/100.Scale Tests Figure 6 shows t h a t the jet in the scale model has the same tendencies with respect to distance and temperature as those shown in Figure 5. 3.5. Behavioral Tests in a 1~20-scale Underground Structure To test the efficiency of smoke control by air control around the fire origin

and to determine control methods to protect evacuation zones from smoke, 53 variations of behavioral testa for smoke movement were carried out. These tests represented combinations of(l) locations of air supply and smoke vent, (2) locations of the fire origin, and (3) methods of air supply and smoke venting. Figure 7 shows the plan view of a 1/20 scale model of the underground structure. Table 3 shows sensors and equipment for the tests, Table 4 shows conditions of the testa, and Table 5 shows the conditions of air supply and the smoke venting.

(11)

50 • 40 •

40

: the distance covered by the tbermocouple rakes ~vo-- ~0[v,I)

i.o1

2

i ["

(Q2/Ls) M = (Q2/LS)v

where L~/L z is a scale ratio (= 12/100).

The Fr number was assumed to be

= pLW2/ApLSg (constant)

(13)

I f LW = Q, then

the dominant factor affecting the scale and the full scale testa. Therefore, the inlet velocity of the jet in the scale model can be calculated using the following equations, as shown in Table 2. Fr = Fi/Fb = pL 3 a/ApLSg

v :120 × :96 • :72

~.~_.

(L4V~/L~)M= (L'VVL~)v

3.3. 12/100 Scale Tests in an Underground Corridor

3.2. Results of the Full-Scale Tests Figure 3 shows t h a t the relationship between the temperature decrease of

45

(pLrg2/ApLSg) M= (pL2VVApLSg)F (12)

l

....~ / O r ~ C ]

,.

vered by

,.,~.:.-a,EF/'~

thejet f,'on~To=44 |'cD

25

I' ~ ~ 20 10

20

311

40

The distance from the inlet [m]

Figure 4. Temperature decreasing in the ceiling jet from the inlet.

Volume 7, Number 4, 1992

0-~

l~

~:(To=~S['Cl, 2'4

~

4~

6b

7~

s~

9~

lds l~0 Time [sec]

Figure 5. Effects on the jet temperature at the inlet caused by varying distance and time.

TUN~.t.T,~G ANDUNDERGROUNDSPACETECHNOLOGY327

Table 2. Inlet velocity of the 12 / l O0-scale tests at the inlet calculated by Fr number.

~ ~ E ~ ~

oz~ od3 o~

E

Temp. of the Ceiling Jet at the Inlet (°C)

Inlet Velocity (I/s)

a~]

204 i

:~ l0

i

~

~- 0i

[ ] : Vo = 2.0 I1/sl, To = 44 ['Cl

~]

~

/~ : Vo = 2.0 [l/sh To = 56 ['C] O : Vo= 2.0[I/s],To = 77 ['C]

8

A

21

g

~

d Time[secl

Figure 6. The relationship between the distance by observation and the time in the 12 /100-scale model.

Vo-12/100 scale

To

Vo-12/100 scale

400 400 400

2.01 2.01 2.01

4.3 56 66

4.3 56 77

O : Thermocouplerake A : Hot-wireanemometer

[] : Staircase [] : Airsupplyorsmokevent n : Air-curtain

~ii~!!~]

Vo

Corridor" I " (ci)

I O Opensp~ace Qo

I

I

0

(D)

uH

1200

L ....

)9_67

OI ~~O

(E2)

ib~mlB~O

(A5)

(A4)

"

(El)

o

l Section

_ I

_

2350

__130q

2350

_

~

~7

. . 9234 . . . . . . . . . . . . . . .

]

j

Figure 7. Plan of 1/20 scale model of the underground structure.

Table 3. Sensors and equipment for the tests. Measurement

Table 4. Conditions of the tests. Test Pattern

Sensors and Equipment tor the Test Item to be tested

Temperature

Velocity of the ceiling jet

Copper-Constantan thermocouple Hot-wire anenometer (range: -20 to 200 [°C], response time: 0.1 [s])

Fan for air supply and smoke vent

DC CenterT M (47 [I/s], 7.5 [mmAq])

Smoke generator

Smoke JetT M

Area to be protected

Fire origin

Air supply and smoke vent Volumetric flow rate at the inlet of the ceiling jet

"A.

.

.

.

B"

Open space(D)

Fire room

Smoke generator (see Fig. 6)

(see Fig. 6)

Fixed

Controlled

(B)

2.6

(Vo[Vs]) Temperature of the ceiling jet at the inlet (To[°C])

328 TUNNF~U~OANDUNDERGROUNDSPACETECHNOLOGY

77

Volume 7, Number 4, 1992

(Note for Table 4: 1. Using eq. (15), the outlet volume shown in Table 4 is calculated from the outlet velocity (1.0 m/s) of the full-scale tests. 2. The temperature ofthe jet at the outlet is set as shown in Table 4, considering the temperature drop from 77°C of the fidl-scale tests to the temperature specified in the table in the duct between the smoke jet and the

Table 5. Conditions of air supply and the smoke vent. Test Pattern "A . Air Supply

.

Smoke Vent

.

B"

Air Supply

Smoke Vent

Air-curtain (El) Air-curtain (E2)

outlet.) 3.6. Results of the 1/20-scale Tests Tables 6 and 7 show smoke movement in allsections ofthe underground structure for the different air control methods, except for the results of the air curtain (El and E2 in Table 5). The test results indicate that smoke would penetrate the curtain. F r o m Tables 6 and 7, we m a y summarize the behavioral tests as follows: 1. The efficiency of the smoke vent will increase w h e n the distance betwsen the air supply and the smoke vent decreases. 2. The efficiency of the smoke vent will increase w h e n the distance between the smoke vent and the fire

.

Staircase ( C 1 )

Staircase(C2)

Staircase ( C 1 )

Staircase(C2)

Open space (D)

Corridor (A3)

Open space (D)

Corridor (A3)

Open space (D)

Staircase(C1)

Open space (D)

Staircase(C2)

Corridor (A2)

Corridor (A1)

Corridor (A2.)

Corridor (A3)

Open space (D)

Staircase(A3)*

Open space (D)

Corridor (A3)*

Open space (D)

Staircase (C2)

Corridor (A5)

Fir room (B)

Corridor (A5)

Fire room (B)°

*with open staircase (C1 + C2)

Table 6. Test results of srnoke control "Pattern A ~.

Air Supply Section of Underground Structure

Open Space + Corridor

Open Space + Corridor

Open Space + Staircase

Corridor + Corridor

Smoke Vent

Position

Method

C1

N N M M M M M M N N

D

N M M M M

Position

Method

C2

M M N N N N M M M M

A3

A2.

Open Space (D)

Cor. Cor. "3 . . . . 2"

N M

C1

M N

A2

N M M

At

M N M

Stair. (c2)

Cor. "v'

S S S S S S S S S S

S S S S S S S S S S

S S S S

S S S S

S S S S S

S S

S S

S S

S S S

S S

M N M N N

D

Stair. (cl)

S

S S S

S: Area contaminated by smoke N: Natural Ventilation M: Mechanical Ventilation

Volume 7, Number 4, 1992

TVNN~.~,X.~OAND U~'DEP~ROU~ SPACETECHNOLOGY329

Table 7. Test results of smoke control "Pattern B".

Section of U-g Structure

Air Supply

Pos.

C1

Staircase

Open Space + Corridor

Open Space + Staircase

D

D

Corridor +

A2

Corridor

Corridor + Fire Room A5

Corridor + Fire Room A4

M M N N

N M M M M M

N N N M M M N N M M M

N N N M M M M

M M M N N M M M

Fan Voltage Range

Open Space

Cor.

Pos.

Meth.

[v]

(D)

H3~q

6>

C2

M M N M M M

5.5> 6> >7.5 12> 11>

S S S S

S S S S S S

M N N M M M

>4.5 >5 >4.5 >8 >5 >4.5

M M M N M M

>8 >7 7> 12> >5 >4.5

M M N M M

12 12> 12> >6 6>

M M M N N M M

>7 >6 6> >7 7> >7 7>

N N N M M M M M

>11 >5 5> >6 6> >11 >6 6>

N N

Staircase +

Meth.

Smoke Vent

A3

C2

A1

B

B

S

Cor. "2"

Stair. (Cl)

Stair. (C2)

Cor. ,v1 o~

S S S S S S S

S S S S S S

S

S

S S S S S S

S S S S S

S S S S S

S S

S S S S

S S S S S

S S S

S S S S S S

S S S S

S

S S S S S

S

S

S

S

S

S

S

S

S

S S

S S

S

S

S

S

S

S

S

S

S

S

S S

S S

S

S

S

S

S: Area contaminated by smoke N: Natural Ventilation M: Mechanical Ventilation

3 3 0 TUNNE,LTJNG AND UNDERGROUND SPACE TECHNOLOGY

Volume 7, Number 4, 1992

between the simulation and behavioral tests in terms of air movement.

4. S i m u l a t i o n of S m o k e Movement

h Staircase(C2)/Top 2: Staircase(C2)/Bottom 3,5 & 10:Corridor 4: Crossing(A3)

Aone-layer zone modelwas employed for the simulation ofunderground struct u r e s because the model can calculate the conditions in many rooms at the same time, and considers only the steady-state of smoke movement in protecting safety or evacuation zones. The smoke density in a room is not a factor in these calculations.

6: Staircase(CI)/Bottom 7: Staircase(Cl)/Top 8: SmokeVent(A3) 9: SmokeInlet 11: OpenSpace(D)

Figure 8. The network for the onelayer zone model.

5.

4.1. One-layer Zone Model I n the model, rooms can be considered as nodes, and arc(s) between the nodes can be considered as route(s) where air and/or smoke go through door(s) or window(s). The network shown in Figure 8 can be considered to comprise the nodes and arcs of the underground structure shown in Figure 6. Table 8 shows the parameters for the simulation calculated from the data in Table 4, using the scallng rule.

origin decreases. Hence, the most effective smoke vent would be the vent installed in the room of fire origin. 3. W h e n conditions of "natural air supply + mechanical smoke vent" and ~mechanical airsupply + natural smoke vent" were compared, there was no obvious differencein the effiencyofthe smoke vent. The efficiency would be more affected by the position of the supply and the vent than by the type of ventilation. 4. The efficiency of the smoke vent in the case of "mechanical air supply and smoke vent" would be affected considerably by the balance of the volume at the supply and the vent. 5. In open staircases, it is important to choose and locate the vent and the air supply properly.

Discussion

5. I. Check of Fr Number with Smoke Propagation in the Full-scale Tests A comparison of the mathematical model (including heat transfer from the jet to the ceiling and walls) and the results from the full-scale tests will show the adequacy of the scale nile. Figures 11 and 12 show the comparisons; the black m n r k s i n the figures represent the distance from the inlet byobservation. Fromthe calculation, the heat transfer coefficient is employed from 0, when there is no heat transfer from the jet to the surrounding area, to 20, which is the upper value for HVAC design (including the effect of radiation). The results of these calculations can be seen in Figures 11 and 12. The comparison may be summarized as follows: 1. In general, the line calculated in the case of a = 0 does not fit with the distance obtained by observation. 2. In the first region, up to 15 or 20 m, the effect of heat loss is not apparent. After this region, however, the effect becomes apparent because of the decrease of the propagation velocity by observation. 3. After 20 m, the test results show good agreement with the curves of the model using a = 10 to 15.

4.2. Comparison between Simulation Results and the Behavioral tTests Figures 9 and 10 show the simulation and behavioral test results of a natural air supply to larger open spaces and mechanical smoke vents, and mechanical air supply to larger open spaces and natural smoke vents from a corridor. The results show good agreement

Table 8. The parameters for the simulation calculated from the data in Table 4 using the scaling rule.

Node No.

1

2

3

4

5

6

7

8

9

10

11

36

36

64

36

64

36

36

*

282

282

154 4

*

°

0.8

0.8

0.8

*

*

*

0.8

0.8

*

Parameters

Volume (cubic m)

Flowing factor: corridor - corridor

*

0.8

0.8

*

0.8

0.8

0.4

.

.

stair (top) - stair (bottom)

0.4

0.4

*

*

*

0.4

0.4

.

.

staircase - outside

0.4

.

corridor - staircase

.

.

.

.

.

Ceiling height (m)

4.8

Temperature (°C)

20

Heat release rate (Kw)

30

.

.

.

.

. .

.

.

*not specififed

Volume 7, Number 4, 1992

TUNN~.U.~GANDUNDERGROIfNDSPACETECHNOLOGY331

Mechanical

f~,,~Natural

s

~

m

pPly

A test result

A test result

7.2~

o

C,

15.2~/~

Natural

~l smoke vent ( ~ ~ . 2 6.3 . . ~ . ~ --'~,~ ~ ~P~ . . •

....

o

Smoke inlet ~ 5.5 " 4 ~

4.9~

~'"

: The area contaminated by smo~e unit: kg/s

Figure 9. The simulation and behavioral test results of natural air supply to larger open spaces and mechanical smoke vents from a corridor. 50

i

/

10-

~l~,f....,--

~

I4 ~

• : the distance from the inlet by observation

.~ s ~' ~lk,~ "

/

~Jbll~"~

J 0

Figure 10. The simulation results and behavioral test results of mechanical air supply to larger open spaces and natural smoke vents from a corridor. 50

/

/~I_I_I_I_~"'--

2'4 ~

- -

:

a

=

: a = 15

- .......

:

~

~

a

~

~/~11""

10-

= 20

- - - -

J 0

~ds t~o

1~

~

~

~

~

7~

u

I ime Isecl

Figure 11. The distance from the inlet by observation and calculated curves using different heat transfer coefficients. 5.2. Propagation of the Jet, Compared between Full and Scale Tests, Using Fr Number Figure 13 shows an example for the comparison between fulland scaletests using the Fr n11mher. The figureshows good agreement between the full and scale tests. Another scalingrule should be taken into account w h e n considering wall materials, because concrete was used on Rdl-scale tests and acrylic panel was chosen for the scaled tests. The thermometric conductivities (or thermal diffusivities)~/(pCp) are 4.96 x 10 6 for concrete and 1.20 x 10 -7for acrylic panel. The dominant factorof the rule would be ~oCp, which is 2.02 x 10 for concrete and 3.64x10 I foracrylicpanel. F r o m an index forthe rule (Tujimoto et al. 1989): ( ~ o C p ) M / ( ~ o C p ) F (L~/Lz.)~ (16) The value of the left side ofeq. (16) is 0.018; the value of the right is 0.042. The order is the same, despite the fact that the latter value is Almost three times as large as the former. For radiation heat, both materials can absorb almost all the heat, up to 300IC If the material under the sc~ilng rule described above is used, the propa----

,~. ~ ~' ~ °

: ~=10 : Ct=15 ........ : u=20 ( To = 65['Cl, Vo = 233[Ys] )

m

- -- -

4's 6b 7~

/ /

:a = 0

-- -

( To = 44['C], Vo = 40l[I/s] )

l~

v~v

: The area contaminated by smoke unit: kg/s

J

• : the distance from the inlet by observation

20-

air supply

®

7

--.,°,e, 5.5 m , l P ~

~4o_

I~0

Mec'll~ical

tds do Time [sec]

Figure 12. The distance from the inlet by observation and calculated curves using different heat transfer coefficients.

gation velocity of the jet can be predicted using small-scale tests.

5.3. Tendency of Smoke Movement in the 1/20-scale Underground Structure Based on the summaries given in Section 3.6,in the case of a natural air supply or smoke vent we must consider the effectsof outside conditions,which are extremely difficult to predict and can affect the air or smoke flow at the air supply or smoke vent. A mechanical air supply and smoke vent system can produce the most effective (or planned) air flow when the volume of the supply and the vent can be controlled. 5.4. One-layer Zone Model Figure 14 shows a calculationresult w h e n the outside temperature changes from 20°C to 10°C (compare Fig. 11 to Fig. 12). Figure 14 shows that the different air flow pattern changes the No. 4 opening from a smoke vent to an air supply. If we raise the No. 8 opening to the same height as the No. I and No. 7 openings, the airflow again changes from an air supply to a smoke vent, as shown in Figure 15. Hence,

332 TUNNRTJ,TNG AND UNDERGROUND SPACE TECHNOLOGY

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the higher the levelof the opening, the stronger the natural smoke vent force becomes. Figure 16 also shows the changing air flow at the nodes No. 1 and No. 7, where air flow changes the smoke vent to an air supply. Therefore, the initialconditions of the environment of the model would affect the entire air movement and, consequently, influence smoke movement, especiallyin the case of a natural smoke vent system The sensitivity of the model means that if adequate initial conditions can be set up, the simulation model can predict air (smoke) movement and, therefore, the efficiency of the smoke control system.

6.

Conclusions

The following conclusions may be drawn from the test results: 1. Regarding smoke movement between full-sizeand 12/100 scale models of the underground corridor: • Smoke movement in the scale model is subject to the Fr number as the scale factor. • When the Fr number is employed, smoke movement shows good agreement between the two models.

Volume 7, N u m b e r 4, 1992

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2. R e g a r d i n g smoke control in t h e 1/20 s c a l e u n d e r g r o u n d s t r u c t u r e model: * The 53 v a r i a t i o n s ofsmoke movem e n t tests, which a r e combinations of locations a n d t y p e s of a i r supplies a n d smoke vents, show t h e b e h a v i o r a l differences of t h e movements. 3. T h e c o m p a r i s o n b e t w e e n t h e 1/20 scale model a n d t h e one-layer zone model i n d i c a t e s t h a t : * The m o d e l c a n s i m u l a t e all o f t h e 53 v a r i a t i o n s u n d e r some ass u m p t i o n s of b o u n d a r y a n d envir o u m e n t a l conditions.

7.

Figure 14. A calculation results from the change in temperature from 20~C to 10°C of Figure 10.

Construction of more a~'urats ~m.L~-

tion models willprovide further study of: 1. The heat loss of smoke to ceiling and walls. 2. The flowing factor in the simulation model. 3. The smoke movement in multistory underground structure models.

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8. References ]~,mmoI~, H.W. 1985. The needed fire science. InProc. ofthe First lnternational Symp. on Fire Safety Science, 33-53. Nakamura, K, et al. 1991. Research of smoke control in u n d e r g r o u n d structures, part 2: experiments of smoke control using a scale model of underground structure. In Proc. of

Annual Meeting of Japan Assoc. for Fire Science and Engineering, 69-72. Tokyo: Japan Association for Fire Science and

F~gmeering.

Nakamura, I¢~ et aL 1991. Research of smoke control in underground structures, part 2: experiments of smoke control using a scale model of underground structure. In Summaries of

Technical Papers of Annual Meeting, Architectural Institute of Japan, 1137-

Further Studies

®

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Time [sec]

5.6 t /~

1~0

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0

Figure 13. A n example for the comparison between full and scale tests using Fr. number.

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1138. Tokyo: Architectural Institute of Japan. Tujimotoet aL 1989. Inllth UJNRonFire Research and Safety, 181-187. Wakamatsu, T. et al. 1991. Research of smoke control in underground structures, part 1: horizontal spread of smoke

In Summaries of Technical Papers of Annual Meeting,Architectural Institute ofJapan, in underground structures.

1135-1136. Tokyo: A r c h i t e c t u r a l Institute of Japan. W . k . m . t e u , T. et al. 1991. Research of smoke control in underground structures, part 1: horizontalspread of smoke in underground structures. In Proc. of

Annual Meeting of Japan Assoc. for Fire Science andEngineering, 65-68. Tokyo: Japan Association for Fire Science and

~gmeer~.

yamano, T. et al.1991. Research ofsmoke controlin underground structures,part 3:a studyby simulationofsmoke control. In Summaries of Technical Papers of Annual Meeting, Architectural Institute of Japan, 1139-1140. Tokyo: Architectural Institute of Japan. Ysmana, T. et al. 1991. Research of smoke control in underground structures, part 3: a study by simulation ofsmoke control. In Proc. of Annual Meeting of Japan Assoc. for Fire Science and Engineering, 73-74. Tokyo: Japan Association for Fire Science and Engineering.

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Volume 7, N u m b e r 4, 1992

Ttn~'R.LT.ma AND UNDERGROUND SPACE TECHNOLOGY 333