Figu re 7。 Corr elat ion betwee n app ar ent an d comput ed soot accumu lat ion rat es。
Tab le 5。 Reac tio n Scheme and Kine tic P aramete rs Emp loyed in the Soot Oxidation
th ese res ults, it can be concluded that th e activat ion energy of 40 k J/mol provides an optimum linear fit with
reaction rat e law
activat ion energy Ei (k J/mol)
frequency factor Ai (mol‚K/m2‚s)
a very good corr elat ion coefficie nt of 0。989 。 This ap- proach ill ustrat es th e potent ial of combining measur e- ment s with modeling towar d providing at least a rough
C/O2 k1 ) A1 T e-E1/RT 125 2。8 × 10-2
C/NO2 k2 ) A2 T e-E3/RT 40 5。0 × 10-1
Tab le 6。 Kine tic P aramete rs and Corr elation
Coe ffici en ts in Sensitivity Ana lysis of Soot + NO2
Reac tio n
indicat ion of th e govern ing kinetics at real exhau st conditions。
Conc lud ing Rema rks
In th e prese nt ed work, engine expe riment s togeth er
activat ion
energy Ei
(k J/mol)
frequency
factor Ai
(mol‚K/m2‚s) fitt ing equat iona
corr elat ion coefficie nt R2
with math emat ical modeling ha ve bee n employed to- war d un derstan ding an d describi ng th e reaction phe- nomena involving NO2 un der realistic conditions。 The followed app roach ha s a num ber of advanta ges an d dra wbacks compar ed to usua l laborat ory practice。
In th e case of reaction stu dies with synth etic gas, it is very difficult to simu lat e exactly th e reaction condi- tions in regar ds to th e composition of th e real diesel exhau st。 Moreover, th e reactor param eters, including reside nce time, soot composition, an d packing condi-
a x: app ar ent car bon consum ption (g/h)。 y: comput ed car bon consum ption (g/h)。
perform ed th e complete set of simu lat ions using eight alternat ive sets of kinetic constant s, as shown in Table
6。 These sets ha ve bee n selected in order to tes t in tota l eight different activat ion energies ran ging from 10 to 80 k J/mol。 For each activat ion energy E, th e preexpo- nent ial factor A ha s bee n selected so that th e product Ae-E/RT is th e sam e for T ) 350 °C。 In th is way, all sets of kinetic param eters will be equivalent at th is temper- atur e only。 It is easy to show that higher activat ion energies will yiel d higher rat es at T > 350 °C an d lower rat es at T < 350 °C。 Exactly th e opposite will hold for lower activat ion energies。
Figur e 8 prese nt s a compar ison of th e app ar ent an d th e comput ed gross soot consum ption rat es due to th e C + NO2 reaction for four different sets of kinetic param eters。 The appar ent rat e is inferr ed by adding th e net appar ent consum ption rat e (as described above) with th e ra w engine soot emissions rat e。 The ideal fitt ing line (y ) x) is also give n in th ese gra phs for compar ison with th e respe ctive fitt ing curves to facilitat e judgment of th e optimum fit。 Additiona lly, Table 6 prese nt s th e linear fitt ing laws obta ined with different param eters set for activat ion energies ran ging from 10 to 80 k J/mol, together with the respe ctive corr elation coefficie nt。 From
tions, ar e rar ely rep rese ntat ive of th e real-world con di- tions in th e part iculat e filter。 Modeling of th e reaction kinetics in laborat ory con ditions is easier an d stra ight- forwar d by plott ing Arrh enius cur ves, but th e kinetic param eters cann ot be directly used in a complete part iculat e filter simu lat ion model。 柴油机碳烟氧化英文文献和中文翻译(15):http://www.youerw.com/fanyi/lunwen_99285.html