ｽﾗｲﾄﾞﾀｲﾄﾙなし

BRI2002：
TWO LAYER ZONE SMOKE
TRANSPORT MODEL
 TANAKA Takeyoshi
DPRI, Kyoto University

YAMADA Shigeru
Fujita Corporation
CONTENTS
INTRODUCTION
1 OUTLINE OF THE MODEL
1. 1 CONCEPTUAL MODEL OF THE MODEL
1. 2 MATHEMATICAL DESCRIPTION OF ZONE PHYSICS
1. 3 COMPONENT PROCESS MODELING
1. 3. 1 Combustion and Heat Release
1. 3. 2 Species Generation Due to Combustion
1. 3. 3 Burning Rate Of Gasified Fuel
1. 3. 4 Opening Flow Rate
1. 3. 5 Fire Plume Flow Rate
1. 3. 6 Opening Jet Plume Flow Rate
1. 3. 7 Penetration Of Fire And Opening Jet Plumes Into Layers
1. 3. 8 Thermal Radiation Heat Transfer
1. 3. 9 Convective Heat Transfer
1. 3. 10 Thermal Conduction In Walls
1. 3. 11 Efficiency Of Mechanical Smoke Extraction
2 OUTLINE OF THE COMPUTER PROGRAM
2. 1
2. 2
2. 3
2. 4
2. 5
STRUCTURE OF THE PROGRAM
MAIN PROGRAM
DATA I/O SUBPROGRAMS
COMPONENT PHYSICS SUBPROGRAMS
NUMERICS SUBPROGRAMS
3 USE OF THE PROGRAM
3. 1
3. 2
3. 3
3. 4
EXECUTION OF THE PROGRAM
OUTPUT FILES
DATA INPUT FORMAT
SAMPLE CALCULATIONS
4 LIMITATIONS AND FUTURE ISSUES
4.1 LIMITATION ON PHYSICS
4.2 PROBLEMS IN APPLICATIONS
 It
is no more than recent 15 years since that a
variety of new smoke control methods, which are
not prescribed in the building codes, has begun to
be introduced into actual buildings in Japan.
 In
performance-based smoke control designs,
some engineering tool that can predict the smoke
behavior with a reasonable accuracy under a
prescribed design fire condition is indispensable.
 For
this purpose, two layer zone models,
particularly multi-story, multi-room
smoke transport model: BRI2 have been
extensively used.
 On
the other hand, more than 15 years have
already passed since the first version of BRI2
was made available from Building Center of
Japan.
 The
understanding has significantly progressed
in several aspects of fire owing to the active
research during this period.
 So
it is thought to be appropriate to take the
opportunity of reprinting the manual to revise
the model taking into account the new research
results and more convenience for users.
Mechanical smoke
extraction
Mechanical air supply
Upper layer
Fire plume
Room i
Opening jet
plume
Lower layer
Schematic of Two Layer zone Model
Room j
(a) any space in a building is filled with an upper
and a lower layers;
(b) the upper and the lower layers are distinctly
divided by a horizontal boundary plane
(discontinuity);
(c) each of the layer is uniform with
respect to physical properties by
virtue of vigorous mixing;
(d) mass transfer across the boundary
of a layer occurs only through a fire
plume, doorjets and doorjet plumes;
(e) heat transfer across a layer boundary occurs by
・the radiation heat exchange among the layers and
the boundary surfaces
・the convective heat transfer between a layer and
the wall surface contacting with the layer
as well as that associated with the mass transfer
referred in (d)
(f) all the heat released by a fire source is transported
by the fire plume, in other word, the flame
radiation loss is neglected.
(g) radiation heat transfer between rooms
is neglected.
 Zone
Conservation and State of Gas
(1) Conservation of mass
d
V  
dt
  m
ij
 m ji

j
(2) Conservation of species
d
Yl V     Yl mij  Yl , j m ji   l
dt
j
(3) Conservation of heat
d
c p VT   Q  Qh   c p  mijT  m jiT j 
dt
j
(4) State of gas
P

M
RT
Combustion product
Combustion
Residual char
TC

w
Gasified fuel
Tp
cchar dT
Ts : Residual char
Fuel at elevated temp
Tp : Gasification
(Pyrolysis)
H2O(v)
Gasification
Temp. rise
Tp

T0
c fuel dT
Original fuel
H2O
H2O(v)
m
100℃
100

T0
cvapor dT
T0 : Initial temp.
Model for species generation in incomplete combustion
Gasified Fuel
C
 C H H O O


r C C H H O O
1  r C
C
Complete Combustion

H H O O

1 r sC
C
H H O O
1  r 1  s C
C

H H O O



r  C CO 2   H H 2 O
2


1 r sC

C
H H O O
 Unburnted
Fuel
1  r 1  s 1  p1  p2  C CO 2 
1  r 1  s  p1 C CO 
1  r 1  s  p2 C C
Incomplete
Combustion
Species Generation Model
in Incomplete Combustion
1  r 1  s 1  q1  H H 2O
2
1  r 1  s q1  H H 2 
2
25
10
△ O 2実測値
○ H 2O 実測値
□ C O 2実測値
8
体積分率(%)
体積分率(%)
20
15
H 2O 予測値
ＣＯ2予測値
10
○ 未燃燃料実測値
△ C O 実測値
□ H 2実測値
未燃燃料予測値
6
4
C O 予測値
5
2
Ｏ2予測値
0
H 2予測値
0
0.0
0.5
1.0
1.5
Equivalence ratio (-)
2.0
0.0
0.5
1.0
1.5
Equivalence ratio (-)
2.0
In case that the pressure in room i is
higher than j at height z
the rate of flow mij between the height
(0<) Z1<z<Z2

2
mij  B 2 g i  i   j Z 23 / 2  Z 13 / 2
3

In case that the temperatures
of the both layers are same
mij  A 2  i pi 0  p j 0 Z 2  Z1 
B: width of opening
α:flow coefficient
 s, j SS
ji
 s,i
pi  z 
SSij
SAij
Z a, j
Z a, j
Ns a
N s a AA
ji
 a, j AAij
p j z 
Ns s
AS ji
N aa
a,i
Z a ,i
Z a ,i
Naa
pi 0 
Opening Flow Rate
p j 0
a) Initial region
m1 z   0.447  Dz 3 / 4
3.0
ｍ1
高さＺ(m )
z
*1 / 3
m2 z   0.21  gZv Z v2 Qzvf
Height
(m)
b) Turbulent flame region
Buoyant
ｍ2
region
Zt2
2.0
Turbulent
ｍ3
Zt1
region
1.0
Initial region
0.0
c) Far field region
0.0
m3 z   0.21  gZv Z Q
2
v
*1 / 3
zv
1.0
2.0
3.0
4.0
質量流量
Plume
massｍ (kg/s)
flow rate
(kg/s)
Fire Plume Flow Rate
plume
5.0
flame
プリューム温度分布
⊿ＴＣ
⊿Ｔ０
Ｚ
巻き込み
Ｑ
火源
Ｚ０
仮想点熱源
Penetration of Fire and
Opening Jet Plumes Into Layers
Wall surface 1  1 , T1 , A1
Layer 1(upper layer)
 G1 , TG1
Ad
Discontinuity
Layer 2(lower layer)
 G 2 , TG 2
 2 , T2 , A2
Wall surface 2
Radiation Heat Transfer
8.3  10 3

h   0.1Q *2 / 5
 40  10 3

Q 
Q


Q
*
c p  T gL L
2
対流熱伝達率（
W /㎡/K）

 2  10 3
2  10 3  Q *  0.1
0.1  Q *
*

 0.9  10
3
Q
HA
50
40
30
20
10
0
0
0.05
0.1
0.15
0.2
無次元発熱速度　Ｑ＊（-）
Convective Heat Transfer

M crit 
1.33

2
gZ
a
s Ta
Ts  Ta 
1/ 2
排
Ts
煙 1.0
効
Z s ,min

 M exTs
 
1.33 a



1/ 5



 / gTa Ts  Ta 



2
率
Reff
Reff
0
Ｚs,min
煙層厚さＺs
Z s / Z s ,min

1
0  Z s  1
1  Z s 
Efficiency of Mechanical Smoke Extraction
Heat Conduction in Wall
(a) Heat conduction equation
T
 2T
 2
t
x
(b) Boundary conditions
T
k
x
T
k
x
 q in t 
x 0
 t 
 q out
x l
q”out =0
BRI2002 does not chase
the heat transferred to
an adjacent room
through a wall
INITDT
初期値の
設定
データの
読み込み
BRI2002
時刻 t=0
BLDGDT 建物データの入力
OPENDT 開口部データの入力
FIREDT 火源・可燃物データの入力
TYWDAT 初期の温度・化学種・壁体データの入力
OUTDOR 外気データの入力
SMCLDT 機械煙制御データの入力
CRTXO2 判定点の酸素濃度の計算
WRITDT 入力データの出力
FRSOUC 現時点での火源条件の計算
入出力
ファイル
の定義
OPNSCH 現時点での開口条件の計算
SMCSYS 現時点での機械煙制御量の計算
LYRDIM 層厚、層に接する壁面積の計算
LYREMT 層内の混合ガスの輻射量の計算
ABSORB 混合ガスの輻射率を求める引用 PG
サブＰＧ
の
呼び出し
PROCES
EQIVRT 層内の酸素濃度から Equivalence Ratio の計算
BISEC 二分法のルーチン
SPECIS 単位燃料量当たりの燃焼速度及び
化学種生成速度の計算
HCONDT 壁体内熱伝導の計算
t=t+⊿
t
要素過程
の
計算
RHTRAN 室内側の輻射熱伝達の計算
CHTRAN 対流熱伝達の計算
FPLUME 火災プルームの計算
VENTLE 多数室間の換気計算
FLWRAT 開口部流量の計算
LINLU
連立一次方程式を解く汎用ルーチン
DOORJT
開口ジェットの計算
DJTSMC
機械給気による開口ジェットの計算
DPLUME 開口ジェットの流量計算
GPBRAT ガス化燃料の燃焼速度の計算
RESULT
RUNGE
BLOCK
DATA
（物性値等）
計算結果の出力
微分方程式を Runge-Kutta 法で解く
DFFUNC 微係数の計
算
LIMITATIONS AND FUTURE ISSUES
(1) LIMITATION ON PHYSICS
(1. 1) Entrainment of Fire Plume
The fire plume model integrated in this model is based on the
model by Zukoski et al. The entrainment coefficient of which is
basically from measurements in a calm environment, which can be
attained only with careful control of experimental conditions.
In more disturbed environment, which may be the case in
actual situation, the plume flow rate may be significantly greater
than the prediction. In fact, the increase of the plume flow rate due to
HVAC or blow down effect by an inflow door jet is reported by
Zukoski et al. and Quintiere et al.
In BRI2002, such an effect on plume entrainment is not
considered since it was not clear to what extent plumes from
realistic burning items, a chair for example, behave like the plume
from burner or pool fire sources.
(1. 2) Plume Penetration
The penetration of a plume, originated
from fire source or a door jet, through a layer
discontinuity is simplistically dealt with the
critical temperature difference in this model.
But it is suspected that not only
temperature difference but also plume
momentum is involved in this phenomenon.
Further investigations will be desired
in this respect.
(1. 3) Air-tightness of Spaces
The algebraic equation for pressure condition in
this model is based on the premise that the pressure build
up in fire is relatively small so that it does not affect the
gas density.
In addition, the room pressures are taken relative to
the pressure in an outdoor space.
So a completely air-tight space is not allowed but
any system of spaces to which this model apply must have
some leak that connect the system to outdoor space as the
sink of mass flow.
It is not necessary, however, that every room in the
system has a leak to outdoor but is sufficient that every
room is connected with outdoor whether directly of
indirectly via other rooms.
(2) PROBLEMS IN APPLICATIONS
(2. 1) On Fire Source Conditions
In this model, scheduled burning rate or heat
release rate of fire source is specified as a given
condition, the manner of which is considered to be
appropriate for most of practical applications.
But since the fire spread itself is not predicted,
input of fire source conditions is required to be realistic.
Particularly, due caution must be taken not to
input mass loss/heat release rate excessively large
compared with the size of room opening to outdoor,
or compared with the fire source area.
Both will limit the air supply for combustion so
result in excessive accumulation of gasified fuel in
the room to small ventilation rate in case of the former
and due to small entrainment rate in case of the latter.
For fire sources in a real fire, a large gasification
rate without a sizable combustion in a room is a
contradiction.
Furthermore, the latent heat of gasification is
automatically subtracted proportionally to the mass
loss rate in the heat conservation equation in this model,
so the drop of the fire room temperature will be
caused if large mass loss rate continues without enough
heat release in the room.
There is no telling what the appropriate range for
fire conditions is but tentative recommendations
are:
(a) maximum heat release rate < 1,500A√H (kW)
(A√H:opening factor)
or maximum mass loss rate < 0.1 A√H (kg/s)
(b) maximum heat release rate per fire source area
<1,000 (kW/m2)
(2. 2) Calculation Time Increment
An adequate calculation time increment
will depend on how fast the change of fire
phenomena are, however, a value about
0.5 -1.0 (sec)
seems to take care of most of the usual conditions,
though empirical.
(2. 3) On upper layer
This model assumes that upper layers exist at any
time from the beginning for the purpose of stability of
calculation.
Whether an upper layer is a real smoke layer or a
pseudo layer should be judged taking into account the
temperature, the species concentration etc.
In addition, a non-contaminated upper layer
can be developed by simple ventilation due to
temperature difference between rooms or between a
room and outdoor, or mechanical injection of air of
which temperature is higher than room temperature.
(2. 4) Pseudo Rooms
Like many other two layer zone model, uniform
temperature within a layer is assumed in this model.
In reality, this assumption may not be appropriate
for spaces laterally very long or wide.
Such a room may be divided into an adequate
number of pseudo rooms for which uniformity
assumption can be insisted to hold, however, this will
be only possible by well knowledged user since
additional consideration is needed on opening flow
coefficient etc.

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