| An investigation of a global reburning-NO reaction, which is the reduction pathway of nitric oxide (NO) by reaction with hydrocarbons, was conducted. The global reburning-NO rate expression and its rate constants were determined. This global reburning-NO rate constant can be expressed as 2.72 {dollar}times{dollar} 10{dollar}sp6{dollar}exp(-18,800/RT) (gmole/cm{dollar}sp3{dollar}s). This expression is applicable to atmospheric pressure, an equivalence ratio range of 1.0-2.08 for light hydrocarbon (CH{dollar}sb4{dollar}, {dollar}rm Csb2Hsb4{dollar}) reburning gases. To derive this reburning-NO rate expression and rate constant, several premixed hydrocarbon flames were simulated at atmospheric pressure with the equivalence ratio (o varied from 0.56 to 2.08. By sensitivity analysis, the global pathways of NO destruction and formation were identified. From these global pathways, the global reburning-NO rate expression was derived. The predicted species profiles obtained from time-resolved computer simulations were then used to deduce the rate constant for the reburning-NO rate expression. The reburning-NO mechanism, which the previous NO submodel didn't include, was integrated into a comprehensive code, PCGC-2. This method was demonstrated by independently deriving the previously measured global rate constants for the fuel-NO reaction HCN+NO {dollar}to{lcub}rm N{rcub}sb2{dollar}. The deduced rate was within about 5% of the values reported from the measurements for a temperature range of 1500 to 2250 K. In order to provide further data to evaluate this new reburning rate expression, concentration profiles for NO, HCN and NH{dollar}sb3{dollar} were measured in a laboratory reactor (CPR) with the variation of equivalence ratio, secondary swirl number and particle size. Measured data also included particle number density, particle velocity, particle temperature, and gas temperature. No substantial difference was observed between the predictions of the local and effluent NO concentrations from both the previous NO submodel and the advanced NO submodel because of the fuel-lean conditions in the CPR measurements. Predictions with the advanced NO submodel for a laboratory-scale combustor (UAVC) for air-staging showed improvement in both magnitude and trends of nitric oxide. Two reburning cases, which used the natural gas as the reburning agent, were also simulated for UAVC and the NO concentration profiles showed good agreement with the measurements provided. |
