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CO + H 2 O CO 2 + H 2. =, to show that. Determine the equilibrium products for the reaction

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Qustion 1 For th rich hydrocarbon-air raction C x H y + a (O +.76 N ) b CO + c CO + d H O + H +.76a N, us th watr-gas shift raction CO + H O CO + H b. = x u =, to show that c. d with K ( G R T ) a b =
Qustion 1 For th rich hydrocarbon-air raction C x H y + a (O +.76 N ) b CO + c CO + d H O + H +.76a N, us th watr-gas shift raction CO + H O CO + H b. = x u =, to show that c. d with K ( G R T ) a b = ( K 1) + x ( K 1) + y [ a( K 1) + x + y K ( K 1)( ax x ) ( K 1) R u = 8.1 J/mol.K [1 marks Dtrmin th quilibrium roducts for th raction C H + O b CO + c CO + d H O + H at K, 1 atm rssur in an oxy-actyln burnr, using th watr-gas shift raction CO + H O CO + H g (, f CO K) = 95.9 kj/mol, g (, f H K) = kj/mol, g f ( CO,K) = 8.69 kj/mol, g f H O,K) = kj/mol ( R u = 8.1 J/mol.K [1 marks Pag 1 of 7 MEM1Combustion Fundamntals and Alications - May6.doc Qustion Considr th quilibrium raction O O + O in a stady flow actyln-air flam. Th flam racts actyln and air according to th raction C H +.5(O +.76 N ) a O + b O H O +.7 H +.55 H +.68 OH CO +. CO +.6 NO N Dtrmin th cofficints of O and O (a and b) in th roducts abov for T b = K, = 1 atm. g (, f O K) = kj/mol, ( O,K) = kj/mol, g f R u = 8.1 J/mol.K [1 marks Th hydrogn-oxygn xlosion curv is givn in Figur Q blow. Figur Q (i) (ii) Exlain th chmistry undrlying th scond xlosion limit, shown in Figur Q abov. [ marks Givn th hydrogn-oxygn combustion mchanism in th data sht, and th branching factor φ = k 1 - k 8 [M, rmin th scond limit critical rssur for xlosion at 55 o C. [1 marks Pag of 7 MEM1Combustion Fundamntals and Alications - May6.doc Qustion Considr th following chain-raction mchanism suggstd for th dry oxidation of carbon monoxid in oxygn: CO + O CO + O + M O + O +M CO + O CO + O + M k 1 CO + O k CO + M k O + M k CO + O + O k 5 CO + O + M Writ out xrssions for d [ CO, d [ O and d [ O. [6 marks Assuming th concntrations of O and O ar in stady-stat, show that: [ O ss = k1[ CO[ O ( k[ CO + k5[ CO[ M ) ( k [ CO + k [ CO[ M )( k [ CO[ M + k [ O [ M ) k k [ CO[ O [ M 5 [ [ [ (c) [ O k1k CO O M = ss k [ CO + k [ CO[ M k [ CO[ M + k [ O [ M k k [ CO[ O ( )( ) [ M 5 (d) Hnc show that d[ CO = k [ CO[ O k k 1 [ CO[ O ( k [ CO + k [ CO[ M )( k [ CO + k [ O ) 5 [9 marks Pag of 7 MEM1Combustion Fundamntals and Alications - May6.doc Qustion Ignoring th ffcts of flam strtch and arodynamic strain, th rat of xansion of a shrically xanding flam can b rlatd to th laminar flam sd through th aroximat rlation dr ρ =. Using th rsults obtaind ρ u SL b from th simlifid laminar flam analysis, stimat th rat of xansion of a shrically xanding, stoichiomtric iso-octan-air flam ignitd in a constant rssur vssl (T u = 7 K, = 15 bar). Not: S L ( iso-octan-air, ϕ = 1., T u = K, = 1 bar) = 5 cm/s. T b (iso-octan-air, ϕ = 1., T u = K, constant rssur) = 6 K. ( K T ).75 n ( n ) SL TuT Tb x 1598 b, n(iso-octan-air) = 1.75 Rlativ atomic wight M(O) = 16, M(N) = 1, M(C) = 1, M(H) = 1. [1 marks Dtrmin th rat of xansion of a shrically xanding stoichiomtric isooctan-air flam subjct to th conditions dscribd in abov, using Mtghalchi and Kck s mirical formula, givn blow. S L = S L γ β Tu, rf, γ =.18.8( ϕ 1), β =.16 +.( ϕ 1), Tu, rf rf S L, rf ( C8H18,98K,1bar) 7.6cm / s 78.cm / s( 1.1). = ϕ (c) A 7 l hydrogn bottl at bar is stord in a m x 5m x m storag room. Th flammability limits for hydrogn ar.15 φ.. If th bottl lakd out all of th stord hydrogn into th room at ambint conditions, rmin: (i) th man quivalnc ratio of th hydrogn-air mixtur in th room, (ii) whthr th hydrogn-air mixtur would b flammabl. [1 marks Pag of 7 MEM1Combustion Fundamntals and Alications - May6.doc Qustion 5 A laminar jt of than (C H 6 ) manats from a mm diamtr burnr nozzl into air at ambint conditions with an xit vlocity of.5 m/s. Using th laminar, isothrmal jt modl, rdict th flam hight for th jt manating from th burnr nozzl. y F J V& ( x,) = =, R = 87 J/kg.K, D = 1.59 x 1-5 m /s, 8πρ v Dx 8πDx LCV (than) = 7.89MJ/kg. [1 marks Exlain (using sktchs) th structur of a laminar non-rmixd jt flam. Includ in your xlanation th diffrncs btwn th rdictions rsulting from a siml non-racting laminar jt diffusion modl, and th obsrvd structur of th flam. [1 marks (c) (i) By analogy with th dfinition of th laminar burning vlocity, dfin th turbulnt burning vlocity v t for a turbulnt flam roagating through a turbulnt, rmixd ful-air mixtur. [ marks (ii) SL Atotal Hnc show that vt =. A [ marks Pag 5 of 7 MEM1Combustion Fundamntals and Alications - May6.doc Qustion 6 Considr th following chain-raction mchanism for th high tmratur formation of nitric oxid, i.. th xtndd Zldovich mchanism: O + N N + O k 1 NO + N k NO + O k N + OH NO + H Assuming [N is in stady-stat, and quilibrium concntrations for O, O, OH, N, H, and OH, show that (i) (ii) [ N ss k1[ O q[ N q =, [ marks k [ O + k [ OH d[ NO = k1[ O q[ N q. [ marks In an oil-fird owr lant roducing 7MW, th ful oil is fd into th furnac via oil sray injctors with th burnr manufacturrs claiming th following faturs: - raid mixing of ful, air and flu gass rior to ignition oint, - burnr gomtry that roducs a vry stabl flam, - introduction of flu gas rcirculation (FGR) to rduc ak flam tmratur. (i) Exlain why ths faturs would mak th burnr an attractiv choic to th lant orators. [6 marks (ii) What faturs may b usd in burnrs to incras mixing? [ marks (iii) To nsur NOx mission lvls comly with rgulatd limits; in addition to th low NOx burnr mntiond abov, th lant will b making us of ost combustion masurs. Suggst two ossibl masurs and giv a basic xlanation of ach. [6 marks (iv) Oil-fird lants roduc crtain lvls of articulat missions. Dscrib th flu-gas tratmnt that will rduc ths missions to rgulatd lvls. [6 marks Pag 6 of 7 MEM1Combustion Fundamntals and Alications - May6.doc Data Sht 1. Hydrogn-Oxygn Mchanism ****************************** **** * **** 1. H-O MECHANISM * **** * ****************************** A(mol,cm,s) b E a (kj/mol) **** 1.1 H-O CHAIN REACTIONS 1. O +H =OH +O.E H +O =OH +H 5.6E H +OH =HO +H 1.E OH +OH =HO +O 1.5E **** 1. RECOMBIN. REACTIONS 5. H +H +M' =H +M' 1.8E H +OH +M' =HO +M'.E O +O +M' =O +M'.9E **** 1. HO FORM./CONSUMPT. 8. H +O +M' =HO +M'.E HO +H =OH +OH 1.5E HO +H =H +O.5E HO +H =HO +O.E HO +O =OH +O 1.8E HO +OH =HO +O 6.E+1.. **** 1. HO FORM./CONSUMPT. 1.HO +HO HO +O.5E OH +OH +M' =HO +M'.5E HO +H =H +HO 1.7E HO +H =HO +OH 1.E HO +O =OH +HO.8E HO +OH =HO +HO 5.E+1.. ****. Roots of th quadratic quation ax + bx + c = x ± b ± = b ac a Pag 7 of 7 MEM1Combustion Fundamntals and Alications - May6.doc
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