SCALING COMP~TMENT FIRES - REDUCED- AND FULL-SCALE ENCLOSURE BURNS

Transcription

1 SCLNG COMP~TMENT FRES - REDUCED- ND FULL-SCLE ENCLOSURE BURNS by Nelon? Bryner,Erik L; Johnon, and William M. Pitt Building and Fire Reearch Laboratory National ntitute of Standard and Technology Gaitherbu~ MD 2899 nternational Conference on Fire Reearch and Engineering, September 1-15,1995. Orlando, FL Proceeding. Sponored by National ntitute of Standard and Technology (NfST) and Society of Fire Protection Engineer (SFPE). D. Peter Lund and Elizabeth. ngel], Editor. Society of Fire Protection Engineer, Boton, M& NOTE Thi paper i a contribution of the National ntitute of Standard and Technology and i not ubject to copyright.

2 Scalirw Comt)artmcnt Fire - Reduced- and Full-Scale Encloure Burn - Nel&t F! Brvrter, Erik L. Johnon, and William M. Pitt Building and Fire Reearch Laboratory National ntitute of Standard and Technology Gaitherburg, MD ntroduction n extenive erie of over 14 natural ga fire in a 2/5th-cale model of a tandard room ha been previouly reported [1]. Thi work extend the earlier reduced-cale encloure (RSE) tudy to a full-cale encloure (FSE) and focue on comparing the ga concentration and temperature of the upper layer and the ventilation behavior of the two compartment. Both tudie are part of a larger reearch effort [23] which i deigned to develop a better undertanding and a predictive capability for the generation of carbon monoxide, the major toxicant in firex+[4$,6,7]. The finding will be incorporated into realitic fire model and ued in the development of trategie for reducing the number of death attributed to carbon monoxide. Experimental The FSE i a tandard room a decribed by SO/STM [8,9] which i 2.44 m wide by 2.44 m tall by 3.67 m deep with a.76 m wide by 2.3 m tall door centered at the bottom of the front wa1. The room conit of a heet metal tud framework which wa lined with three layer of 1.27 cm thick gypum wallboard and a ingle layer of 1.27cm thick calcium-ilicate board. Two trcea of 33 bare chromel-alumel thermocouple were utilized to monitor temperature wilhin the encloure and a third tree often apirated thermocouple wa ued to track temperature vertically acro the doorway. The inide tree were placed 5 cm from a ide wall and 5 cm from the front and rear wall. Two additional platinum-rhodium thermocouple were incorporated after ome of the temperature were dicovered to have exceeded the upper range of chromelalumel (126 C). Cooled and uncooled extraction probe were poitioned at different location to allow individual CO, C2, and 2 ga analyzer to ample the upper combution layer, lower layer, and outide the doorway. lkmperature data from the apirated thermocouple are ued in tandem with inide thermocouple meaurement to calculate doorway ma flow uing a recently developed algorithm [1,11]. The 35 cm diameter burner, which wa caled to maintain the ame fuel exit velocitie a in the RSE, i centered in the encloure with the upper burner lip 3S cm above the floor. Fire ize wa controlled by etting the metered flow of the natural ga fuel. The reduced-cale encloure wa deigned to be a 4!%cale model of the tandard room and ha been previouly decribed [1]. Briefly, the overall dimenion of the RSE were caled geometrically from thoe for the FSE reulting in a RSE with internal dimenion of.98 m wide x.98 m tail x 1.46 m deep. The area for the doorway wa determined uing the h12 encloure ventilation caling parameter where i the geometrically caled total area of the ventilation opening and h i the height of the opening [1,12]. Thi reult in a.48 m wide x.81 m tall door for the RSE. The RSE teel frame wa firt lined with heet metal to form an airtight encloure before two layer of 1.27 cm thick calcium-ilicate board were added to become the inner wall. in the FSE, two thermocouple tree were utilized to monitor temperature within the encloure and a tree of five apirated thermocouple wa ued to track temperature verticdy acro the doorway. tree of even chromel-ahtmel thermocouple wa located in a rear corner, 2 cm from the ide wall and 2 cm from the rear wall. tree of 17 thermocouple wa poitioned in a front corner 2 cm from the ide wall and 2 cm from the front wall. Cooled and uncooled probe were poitioned at different location to allow individual CO, C2, and 2 ga analyzer to ampe the upper combution layer, lower layer, and outide the doorway. The doorway ma flowwere calculated uing the ame algorithm a the FSE. The 15 cm diameter burner wa centered in the encloure with the upper burner lip 15 cm above the floor. Both the FSE and RSE were located under large intrumented exhaut hood which allowed ga analyi and oxygen calorimetry [13,14] to be performed on the exhaut gae from the encloure. Each fire conducted in the RSE or FSE typically lated 15 to 2 minute. While over 14 fire with heat releae rate (HRR) ranging from 7 to 65 kw were burned within the RSE, a more limited erie of twelve fire ranging from 45 kw to 35 kw were completed within the FSE. Fire of greater than 2 kw and 14 kw HRR created DOSt-flaShOVer condition within the RSE and FSE, rcpectivey. Reult and Dicuion The data from the RSE and FSE allow comparion of the upper-layer ga concentration and temperature, a well a the ventilation behavior of the two compartment for ovewentilated, neartoichiometric, and undcrventilatcd condition. Each pair ot fire, one from the RSE and another from the FSE, have been choen to have roughly the ame global equivalence ratio (GER), defined a the ma in the upper layer derived from the fuel divided by the ma derived from the air normalized by the ma ratio for 9

3 toichiometric burning. The front and rear upper-layer ga concentration of CO and 2 are plotted for a pair of overvcntilated fire (Figure 1 and 2), a pair of near-toichiometric tire (Figure 3 and 4), and a pair of undervcntilated fire (Figure 5 and 6). Front and rear upper-layer temperature are alo plotted for each fire ize (Figure 7-9). The GER for the FSE and RSE for the different ventilation condition are included in Table 1. Scaling the RSE doorway via the hle ventilation parameter provccl to be very accurate. The M12 caling technique incorporate the quare of a geometric caling factor which wa.4 for the RSE. the ma flow rate are caled up from the RSE to the FSE, an increae by a factor of 6.25 (ie. (1/.4)2 ) i expected. hble 1 indicate, the increae in ma flow rate from the RSE to the FSE i conitently a factor of 6.6 or 6.7. Thee are equal to the prediction within experimental uncertainty. fter completing over 14 of the RSE burn, and before actually igniting any of the fire in the FSE, everal caling technique were ued to etimate the heat releae rate ufficient to jut undetventilate the FSE. The h12 ventilation parameter calculation predicted that the FSE would become underventilated at 125 kw. The oberved value wa 14 kw in the FSE where the oxygen concentration approached -- zero in both the front and rear of the upper layer. llible. 1. Fuel and ir Ma Flow nto the RSE and FSE leat Releae Fuel Ma ir Ma Total Ma Global Ratio of FSE Rate, kw Ftow Rate Ftow Rate Ftow Rate Equivalence Flow to RSE to Burner into Door into Encloure Ratio Flow Qy ) (g/) (g/) 1 (RSE) $5 (FSE) , (RSE) (FSE) (RS?) (FSE) Note Each ma flow rate wa averaged over a 66 econd time period. Ma flow rate algorithm ue an integrative approach which force the air and fuel ma flow rate into and the the ma flow rate out of the encloure to be equal [11]. For the overventilated condition in both encloure, the meaured concentration of CO (Figure 1) were uniformly low, le than.25%. The oxygen concentration (Figure 2) in the upper layer of the RSE dropped 1 about 7% in both the front and rear, but the upper layer of the FSE wa not a uniform with front and rear concentration of 2 dropping to 97 and 5%, repectively. the fuel flow rate were increaed, the RSE or the FSE became more and more underventilated and the oxygen in the upper layer decreaed until the oxygen concentration dropped to near zero for heat releae rate of around 2 kw and 125 kw, repectively. For both near-toichiometric tire (Figure 3 and 4), the upper-layer 2 concentration approached zero in the rear of the encloure. n the front of the encloure, the oxygen concentration were not completely depleted with 2% and 3% meaured in the RSE and FSE, repectively. The CO protile for the front and rear of the RSE upper layer averaged about 1%, but with a large amount of catter in the data. n the rear of the FSE upper layer, the carbon monoxide concentration lowly approached the value oberved in the RSE. The concentration of CO in the front of the FSE upper layer were.2%, ignificantly lower than the rear. For the mot underventilated condition, the upper layer of both the RSE and FSE were completely depleted of oxygen. The upper layer of both compartment had higher concentration of carbon monoxide a compared to the overvcntilated and near-toichiometric cae. The ditribution of CO within the upper layer wa very different for the two encloure with higher concentration oberved in the rear of the FSE and in the front of the RSE. The RSE upper layer concentration were 2.2 %and 1.8%, front and rear, while the correponding concentration for the FSE ranged from % and %,front and rear, repectively. The concentration of CO in the FSE upper layer were till increaing when the tire wa terminated. 1

4 . deally one would hope the quantitative concentration behavior of the combution gae would be imilar in the RSE and FSE. However, it i clear that the concentration of carbon monoxide and oxygen are not a WC1behaved a the ma flow rate. The good agreement with predicted ma flow and the correponding lack of agreement with ga concentration indicate that the generation of combution product i not cnlirely controlled by the ventilation behavior of the encloure. Temperature profile for both the RSE and FSE from chromcl-alumel thermocouple ocatcd in the upper layer are plotted in Figure 7 (ovcrventilated), 8 (near-toichiometric) and 9 (underventilated). Thee temperature were recorded 8 cm and 2 cm above the floor, for the RSE and FSE, repectively. The plot indicate that the FSE encloure upper-layer temperature were typically 1 to 2 C hotter than the reduced-cale compartment. Thee higher temperature arc probably due to the relatively larger door and reduced wall urface area in the RSE. The area of the doorway of the RSE i a larger fraction of the front wall than in the FSE and a higher fraction of the heat releaed within the encloure i lot via radiation through the opening. The RSE alo ha a relatively greater wall urface area to total volume ratio than the FSE, o a greater fraction of heat can be lot by conduction through the wall of the RSE. The temperature profile for both encloure demontrate that temperature in the front of the encloure were hotter than in the rear. The larget difference were for the RSE where temperature difference of up to 3 C were oberved. Since temperature in the upper layer of the FSE exceeded the upper range of chromel-alumel thermocouple, a pair of platinum-rhodium thermocoupk were intalled for 23 and 35 kw fire (not hown). n the 35 kw fire, front and rear temperature peaked at 12 C and 95 C, repectively. Slightly higher temperature were oberved in the front and rear, 13 C and 1 C, repectively, for the 23 kw fire. Thee higher temperature provide a poible explanation for the much higher concentration of CO oberved in the FSE a compared to the RSE. Pitt [15] ha ued detailed kinetic modeling to how that mixture of rich combution gae begin to come into thermodynamic equilibrium for temperature on the order of 11 C. t thee temperature the formation of CO i trongly favored over C2, and the production of CO i expected. The fact that the CO concentration (Figure 5) and temperature (Figure 9) eem to increae together upport thi concluion. lkmperature in the RSE are too low for the reaction reponible for bringing the combution gae into thermodynamic equilibrium to be important. Concluion The reduced-cale and full-cale encloure burn erie allow a comparion of the compoition and temperature of the upper ayer and the ventilation behavior for two geometrically imilar compartment. The h12 ventilation caling technique doe an excellent job of caling the ma flow into and out of the two encloure. The ventilation caling technique did not uccefully predict the compoition or temperature of combution product in the upper layer when attempting to cale-up from the maller cale to the larger compartment. The FSE burn generated ignificantly higher upper-layer carbon monoxide concentration than oberved in the RSE burn. Carbon monoxide concentration of about 6% were meaured in the front and rear of the FSE during higher HRR fire. Thee CO level are two time higher than the concentration oberved in the reduced-cale encloure burn and about three time higher than thoe reported by previou reearcher conducting idealized hood experiment [16,17,18]. Temperature in the upper layer of the FSE are ignificantly higher than in the RSE providing an explanation for the higher CO concentration oberved a compared to the RSE. The front portion of the upper layer in both the FSE and RSE have ignificantly higher temperature than the rear. Finding from thi invetigation a well a other have been ued to derive a engineering algorithm for predicting CO formation in encloure fire [19]. Reference 1. Bryner, N.P., Johnon, E.L., and Pitt, W.M., Carbon Monoxide Production in Compartment Fire - Reduced-Scale Encloure Tet Facility, Nat. nt. Std. and Tech. (U.S.) NSTR 556& 1994 December. 2 p. 2. Pitt, W.M., Executive Summary for the Workhop on Developing a Predictive Capability for CO Formation in Fire, Nat. nt. Std. and Tech. (U. S.) NSTR 89-49% 1989 pril. 68p. 3. Pitt, W.M., Long-Range Plan for a Reearch Project on Carbon Monoxide Production and Prediction, Nat. nt. Std. and Tech. (U. S.) NSTfR ; 1989 May. 4 p. 4. Harland, W.. and nderon, R.., Caue of death in fire. Proceeding Smoke and Toxic Gae from Burning Plati, January 6-7, 198 London, England. 15/1-15/ Hill..R., ncapacitation and fire: merican Journal of Forenic Medicine and Pathooy, 1(1):49-53,

5 , ~ Harwood, B., and Hall, J.R., What Kill in Fire Smoke nhalation or Burn? Fire J. 83(3): May/June. Bkky, M.M., Halpin, B.M., Capan, Y.H., Fiher, R. S., Mclliter, J.M., and Dixon,.M., Fire Fhtality Study; Fire and Material, 3(4): , 1979 December. Fke Tet - Full-Scale Tet for Surface Product. Draft nternational Standard SO/DS 975. ntcmational Organization for Standardization. Geneva, Switzerland; Propoed Method for Room Fke T=t of Wall and Ceiling Material and emblie. merican Society for T&ting and Material. Philadelphia, VG1982 November Janen, M., and %an, H., Data Reduction of Room Trot for Zone Model Validation, Journal of Fire Science, 1:528-55$1992. JohnSon, E.L., Bryner, N.R, and Pitt, W.?, Fire-nduced Ma Flow into a Redueed-Scale Encloure: to be ubmitted to Fke Safety Journal. Quintiere, J.G. Scaling pplication in Fire Reearch: Fire Safety Journa~ 15(1):3-2% Twilley, W.H., and Babrauka, V, Uer Guide for the Cone Calorimeter, Nat. Bur. Std. (U.S.) NBS Special Publication 745, ugut 1988, 118 p. krggett, C., Etimation of Rate of Heat Releae by Mean of Oxygen Conumption Meaurement; 4(2):61-65, 198 June. Fire and Material, P@ W.M., pplimtion of Thermodynamic and Detailed Chemical Kinetic Modeling to Undertanding Combution Product Generation in Encloure Fire., To appear in Fire Safety Journal. Beyler, C.L., Major Specie Production by Diffuion Flame in a Two-layer Compartment Fire Environment: Journal, , 1986 January. Fire Safety Toner, S.J., Zukoki, E.E., Kubota, T, Entrainment, Chemitty, and Structure of Fire Plume. Nat. Bur. Std. (U.S.) NBS-GCR-87-5a 1987 pril. 2p. Morehart, J.H., Zukoki, E.E., Kubota, X,Specie Produced in Fire Burning in Two-Layered and Homogeneou Vkiated Environment. Nat. nt. Std. and Tech. NST-GCR-9-585; 199 ugut. 2.59p. Pitt, W.M., n Engineering lgorithm for the Etimation of Carbon Monoxide Generation in Encloure Fire, Paper preented at the E&crn S@e ~ection Meeting of the Combution ntitute, ClearWater Florida, December 5-7, 1!% a al t w u N.4 -L 1 Cu m u ) m F a u-i to N (WM)%O UO!WJW39S$CX)3 (WM)% O UO!V3.SWXNtO~ () 12

6 , to r i d RSE 2kW Front 6 t. RSE 4kW Front o RSE 4kW Rear 5 FSE 27kW Front FSE 27kW Rear 1.5 t o Time, Figure 3. Upper layer carbon monoxide concentrate ion in tbe RSE and FSE for two near-tolcbiometric fire. 1 k o o Time, Figure 5. Upper layer carbon monoxide concentration in the RSE and FSE veru time for two underventilated fire RSE 2kW Front O RSE 2kW Rear Q FSE 125kW Front FSE 125kW 2 %. 1 o Time, Figure 4. Upper layer oxygen concentration in the RSE and FSE veru time for two near. toichiometric fire. u 1 * 5 e o ~ti.d o T[me, Figure 6. Upper layer oxygen concentration in the RSE and FSE veru time for two underventilated fire, - o

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