Influence of Atmospheric Pressure Fluctuation on Air Leakage Rate of Airtight-wall

Transcription

1 Avilble online t Procedi Engineering (0) The 5 th Conference on Performnce-bsed Fire nd Fire Protection Engineering Influence of Atmospheric Pressure Fluctution on Air Lekge Rte of Airtight-wll SU Fu-peng *, ZHOU Xin-qun, WANG Yi Chin University of Mining & Technology(Beijing) Stte Key Lbortory of Col Resources & Sfety Mining, Beijing00083,Chin Abstrct Aiming t strengthening the irtight-wll tightness, reducing its lekge rte, so tht extinguishing the combustion in the burning re s soon s possible, this pper proposes the new ides tht the tmospheric pressure chnges is importnt ffecting fctor to irtight-wll lekge rte in irtight burning re. Adopting the comprehensive reserch method of theoreticl nlysis, field mesurement, nd numericl clcultion, this pper studies the influence lw of the periodicl chnge of the tmospheric pressure on the irtight-wll lekge rte, the results show tht: the curve of underground pressure is sinusoid pproximtely; the tmospheric pressure chnges is the min reson for the internl nd externl pressure difference of the irtight-wll; the gs exchnge cpcity of internl nd externl burning re is lrge, the gs exchnge cpcity of clcultion exmple is more thn 400m3 every dy. To reduce the firewll lekge rte, this pper proposes the specific solutions including building gs pressure blnce room, strengthening irtight-wll tightness, nd reducing the burning re volume, etc. 0 Published by Elsevier Ltd. Open ccess under CC BY-NC-ND license. Key words: seling burning re; irtight-wll; ir lekge rte; tmospheric pressure * Corresponding uthor. E-mil ddress: sfp08@63.com Published by Elsevier Ltd. doi:0.06/j.proeng Open ccess under CC BY-NC-ND license.

2 40 SU Fu-peng et l. / Procedi Engineering (0) Foreword The min function of burning re firewll is cut off the oxygen supply condition of col combustion, so tht control the flmes. Airtight-wll tightness directly ffects the seling burning re ir lekge rte, the higher tightness, nd the smller ir lekge rte []. Airtight-wll ir lekge rte lso reltes to the internl nd externl drught hed of firewll, the higher drught hed, nd the higher ir lekge rte, conversely the smller. The formtion of drught hed is ffected by vriety of fctors, the tmospheric pressure [, 3] chnges is very importnt fctor.. Mthemticl model of tmospheric pressure periodicl chnges Becuse of the tmospheric temperture periodicl chnges, the erth s surfce tmospheric pressure will then present cyclicl voltility, when the tmospheric tempertures rises, the tmospheric pressure lowers, when the tmospheric temperture drops, the tmospheric pressure rises[4]. The erth s surfce tmospheric pressure chnges cuse pressure distribution chnges within the rodwy of mine, this will cuse the internl nd externl pressure difference of the irtight-wll in burning re, nd led to inside ir leking out or outside ir inflowing, similr to the respirtion, this phenomenon is unfvorble to suffocte burning re nd prevent the fire from further development [5]. Given the tmospheric pressure chnge is the importnt resons tht cused seling burning re "brething" nd ir lekge of the firewll, studying the vrition lw of tmospheric pressure is very necessry. Vrious mterils [6-8] shows tht when the wether condition is reltively stble, the tmospheric pressure chnges follow certin rules. In order to convenient for study, estblish mthemtics model s follows: suppose the tmospheric pressure on fixed period nd mke sine wve, mplitude chngeless, s formul () shows: = p0 Δp τ cos(π ) Δ τ Δp p In the formul, P0 verge pressure; Δ τ cycle period; mplitude of pressure chnge 3. ir lekge clculte of firewll Assume the ir inside seling burning re is lminr flow, nd ir lekge direction is inflowing, it is nmely: = ( p p s ) R p In the formul, p ir pressure outside seling re, P; s ir pressure inside seling re, P; R totl wind drg of ir leking chnnel nd firewll, N min/m 5. Becuse when τ = 0, = 0 p s0 Δp Letbe = VR, b= π π. nd c= R Δτ Δ τ, solving over formul: bc b c = exp( τ )( 0 + ) + sin( cτ tg ) 3 + b ( + b ) In the formul, V totl ir volume inside seling re; P s0 initil ir pressure vlue within seling re Formul (3) is the reltionl expression of firewll ir lekge rte nd tmospheric pressure chnges. when τ : b c = sin( cτ tg ) ( + c ) 4 b ( + b ) is the mplitude of the cycle, c tg is phse difference between nd P

3 SU Fu-peng et l. / Procedi Engineering (0) So q = mx b ( + b ) Δp R p RV π Δτ π + Δτ s0 The totl ir lekge into or out of the seling burning re is q Δτ Q = mx 6 π 5 4. Atmospheric pressure mesurement results nd nlysis The tmospheric pressure mesurement experiment proceeded in Xing An Col Mine, He Gng Bureu of Mining Affirs, Hei Longjing Province, the specific loction is nerby the burning re in second level, whose elevtion is -97.8m. The instrument is CPD/0 mining portble ir pressure mesurement (developed by Aerospce Aerodynmic Reserch Institute nd Fu Shun Brnch of Chin Col Reserch Institute). Device prmeters is showed in reference[9].fixed point mesurement continuous 4 hours (every 5 minutes records the dt), obtined the tmospheric pressure chnges dt of 4 hours ner the burning re. The key experimentl dt is shown in tble. According to the experimentl dt nd grph, it cn be seen, from morning 8:40, tmospheric pressure continued to decline, nd rech the lowest 0058P t 3:40; then begn to rise grdully, until the next morning 6:0 reched the highest 00790P finlly; then begn to decline, nd lwys hs such cyclicl chnge. The experiment results bsiclly tllies with the estblished mthemticl model of tmospheric pressure chnges. 5. Anlyzing the influentil fctors of irtight-wll ir lekge From the formul (7), the min 5 fctors ffecting the irtight-wll ir lekge includes: ir pressure chnges Δp mplitude, firewll wind resistnce R, ir pressure chnge cycle Δ τ, initil pressure within burning re Ps0 nd burning re volume V, nd the ir pressure chnge cycle hs been determined fter the modeling, nd the initil pressure within the burning re is certin too, so just nother three fctors need be considered. Tble. Importnt Dt of Atmospheric Pressure Mesurement ime of experiment begin ime of experiment stop ime of Lowest ir pressure pper ir pressure lowest ime of highest ir pressure pper ir pressure highest verge of ir pressure mplitude of ir pressure m840 m8:40 m3:40 m 6:0

4 404 SU Fu-peng et l. / Procedi Engineering (0) Through dt sorting, mking grph s shown in figure Fig.. The 4 hours vrition curve digrm of tmospheric pressure nerby the fire zone of Xing n col mine 5.. Reltionship of ir pressure chnges mplitude nd mximum irtight-wll ir lekge rte On the influence nlysis of the ir pressure chnges mplitude to the irtight-wll ir lekge, other fctors tken fixed vlue, just the ir pressure chnges mplitude chnge the size, so tht the reltionship between them cn be clerly seen, the sme methods dopted in fter nlyzing. The experimentl dt shows tht the tmospheric Δp pressure chnges mplitude = 66 P, wind resistnce R= N min/m5, Δ τ =4 60 min, the initil pressure within seling burning re Ps0 05 P, totl volume of seling burning re V3 03 m3, set wind resistnce R, cycle Δτ, initil pressure Ps0, burning re volume V tking experimentl vlue, nd chnge the Δ p pressure mplitude, ccording to the formul (5) : Δp π π Δp R mx = R Δτ = Δτ 7 ps0 π ps0 π ( ) + ( ) ( ) + ( R) RV Δτ V Δτ Substituting the experimentl dt of R, Δ τ, Ps0, V, nd clculting, so Δp mx = This is the reltion formul of mx Δp nd, ccording to the reltion formul, mde grph s figure shows, it cn be clerly seen tht mximum firewll ir lekge rte nd pressure chnges mplitude is in liner reltion. 5.. Reltionship of wind resistnce nd mximum irtight-wll ir lekge rte so Δp Anlyzing s 4., ccording formul (8), substituting the experimentl dt of, mx = R [ R ] Δ τ, Ps0, V, nd clculting,

5 SU Fu-peng et l. / Procedi Engineering (0) mx This is the reltion formul of nd R, ccording to the reltion formul, mde grph s fig.3 shows, it cn be seen tht the biggest ir lekge rte mx nd wind resistnce R is similr in inverse reltionship, when wind resistnce is lesser, mximum ir lekge rte decreses rpidly with wind resistnce increses, when the wind resistnce is more thn 3 04 N min/m5, mximum ir lekge rte down slowly with wind resistnce increse Reltionship of burning re volume nd mximum irtight-wll ir lekge rte Δp Anlyzing s 4., ccording formul (8), substituting the experimentl dt of, R, Δ τ, Ps0, nd clculting, so 07.4 mx = V This is the reltion formul of mx nd V, mde grph s figure 4 shows, it cn be seen tht the mximum ir lekge rte nd the burning re volume is similr in exponentil reltionship, mximum ir lekge rte increses with burning re volume increses, when V is smller thn 500m3, rpidly increses with V increses, when V is more thn 500m3, q mx mx increse slowly with V increses. Fig.. The reltionship between the Mx ir lekge nd fluctution mplitude of pressure

6 406 SU Fu-peng et l. / Procedi Engineering (0) Fig. 3. The reltionship between the Mx ir lekge nd ventiltion resistnce Fig. 4. The reltionship between the Mx ir lekge nd the volume of fire zone

7 SU Fu-peng et l. / Procedi Engineering (0) Countermesures Seling burning re ims to reduce oxygen supply to fire belt, but the internl nd externl pressure difference of irtight-wll still cuses different degree of ir lekge. And ccording to the formul (5) nd the ctul experimentl mesurement dt, the ir lekge rte of irtight-wll is mx = 3.06 theory m3 / min; ccording to the formul (7), it cn be clculted tht the gs exchnge cpcity between burning re nd outside in one dy is Q = 40.6 m3, it reched lmost hlf of the burning re volume. Completely voiding ir lekge is unlikely, but resonble steps cn be tken to reduce ir lekge. According to the severl influence fctors of irtight-wll ir lekge mentioned below, the corresponding countermesures is put forwrd. () Estblish pressure blnce room, djust internl nd externl prtil pressure difference of irtight-wll. Pressure blnce room is setting the second irtight-wll close to nd outside the originl irtight-wll, nd instlling tube or pressure ventiltor on the second irtight-wll to djust the ir pressure difference of the spce between the first nd the second irtight-wll so tht it is equl to the ir pressure in the seling burning re. The specific methods nd ppliction prctices hs been introduced in mny litertures [0, ], nd no introduces in this pper. () Incresing irtight-wll tightness. There hve two kinds of methods cn improve the irtight-wll tightness, one is the technology, such s when building irtight-wll, using plstic scrub-brush insted of slice to pint surfce mortr, this cn increse the lekproofness nd durbility of firewll [5], the other is the mteril, dding fiberglss in mortr, this cn increse the strength nd viscosity of cement mortr nd be esier to smer. In ddition, some new mterils lso begin to use in col fire extinguishing, such s Luokexiu fom products []. (3) Decrese burning re volume. If when initilly building the irtight-wll considering security or terrin is urgent, wider rnge of burning re hs to be seled, nd wnt to compress the burning re fterwrds, the shrinkge seling method must be dopted, this is of some risk. But this cn be put the effects on the norml production to minimize, nd lso cn reduce the mximum ir lekge of irtight-wll, to extinguish burning re s soon s possible. 7. Conclusion () Put forwrd the tmospheric pressure chnges is importnt ffecting fctor to the firewll ir lekge, nd estblished the mthemticl model of tmospheric pressure sine wve, nd verified the rtionlity of the model by experiments in some degree, nd combining exmples clculted the ir lekge of burning re in cycle (one dy), the ir lekge of the exmple is lmost hlf of the volume of burning re. () Anlyzed the tmospheric pressure fluctution rnge, irtight-wll tightness, burning re volume, this three fctors influence on the mximum irtight-wll ir lekge rte. The mximum ir lekge rte increses with the ir pressure fluctution rnge nd the burning re volume increses, nd decreses with the increse of firewll tightness. Aiming t three influence fctors of mximum firewll ir lekge rte, proposes the specific solutions including building gs pressure blnce room, strengthening firewll tightness, nd reducing the burning re volume. Acknowledgements This work ws supported by Foundtion Project- th five-yer Science Technology Supporting Pln(007BAKB04) nd Ntionl Bsic Reserch Progrm of Chin(005CB500). References []ZHANG Qingsong, LIU Chowen, HAO Yu. The Building Technique of Closing Fire Zone Firewll [J] Sfety in Col Mine, []WANG Hining. Flow nd control of ir in mine[m]. Beijing. Metllurgicl Industry Iress, 007: [3] LU Yiyu, WANG Kejin, LI Xiohong. Ventiltion nd sfety in mine [M]. Chongqing. Chongqing University Press :3-6

8 408 SU Fu-peng et l. / Procedi Engineering (0) [4]YAN Binyi, QIN Yujin. The effect of ir pressure to working fce gs emission nd prevention mesures[j]. Sfety in Col Mine, 006.0: [5]ZHOU Xinqun, WU Bing. Fire disster relief theory nd prctice in mine[m]. Beijing: Col Industry Press, 996.: [6]K. W. Moloney, I. S. Lowndes. Comprison of mesured underground ir velocities nd ir flows simulted by computtionl fluid dynmics [J]. Trns. Instn Min. Metll. (Sect. A: Min. industry), 999:A05A4 [7]Chow w. k. simultion of tunne fire using zone mode. Tunneling nd underground nd spce technology [J]. 996, ()36 [8]QIU Yn, GAO Gungwei, LUO Hizhu. Mechnism of Pumping Inert Gs into Mine Fire Are for Inhibition of Methne Explosion[J]. Sfety in Col Mine. 003.:8- [9] [0] QI Yingmin etl. Col Mine Sfety Mnul(the Forth Series)[M], Col Industry Press,99 [] LI Bo, SHAN Yfei, ZHANG Jin, YUAN Yongguo, JIANG Gng. Appliction of the Technology on Connected Pipeline Pressure Chmber[J]. Express Informtion of Mining Industry, []QIU Chunling, ZHANG Xueto. Technology of Luokexiu Fom product Applied in Jining No. Mine[J]. Col Science nd Technology, [3]Pn Fuxing, Ding Ruijin. Appliction of positive ventiltion in fire fighting [J]. Fire Technique nd Products Informtion, 006 (8), 40-43