A study on the effect of different diluents on laminar burning velocity and flame stability of oxy-n-dodecane mixtures at elevated pressures and temperatures

N-dodecane is one of the primary surrogate species of many commercial liquid fuels. The objective here was to measure the unstretched laminar burning velocity (LBV) and burned gas Markstein length (Lb) of oxy-n-dodecane mixtures having high-flame temperatures safely by adding a third party inert species using the spherically outwardly propagating flame (SPF) method. (100-Z )% (n-C12H26 + (18.5 O2/& phi;)) + Z % (N2/CO2/H2O) mixtures were analysed at 400-450 K, 1-4 bar, & phi;= 0.6-1.4, and Z : (a) N 2 = 55-75%, (b) CO2/ H2O = 65%. N 2 diluted mixtures were subjected to predominant thermal effects, whereas H2O/ CO2 di-luted mixtures were affected by all the real-time effects like thermal & chemical, radiation and thermo-diffusive effects. The planar flame model in CHEMKIN was used to simulate LBV using You, JetsurF2.0, and PoliMi-1410 mechanisms. At 65% dilution, mixtures diluted with: (a) N 2 had the highest LBV due to the high-flame temperature, (b) CO2 suppressed the LBV the most due to the thermal and chemical effects. Predicted LBV with You and JetsurF2.0 mechanisms showed an excellent agreement with the present measurements. PoliMi's kinetic scheme always over-predicted the LBV in the rich mixtures. The effect of thermal radiation on the LBV of CO2/H2O diluted mixtures was quantified using a freely propagating planar flame model with YaoSK54 mechanism and SNBCK radiation model. The diluted oxy-fuel mixtures generated stable flames towards thermo-diffusive effects at all the studied conditions. At a given thermo-dynamic condition, the flame's stability to the thermo-diffusive effects was the highest for the mixtures diluted with steam and it was followed by N 2 and CO2 due to their respective Lewis numbers. If the flame temperature attained 2150 K or lower, the diluted oxy-n-dodecane mixtures at & phi;= 1.4 were affected by thermo-diffusive instability. The sensitivity of the chain termination reaction H + OH + M & LRARR; H2O + M showed a transition from negative to positive at 0% N 2 case.& COPY; 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The objective of this study was to measure the unstretched laminar burning velocity (LBV) and burned gas Markstein length (Lb) of oxy-n-dodecane mixtures using the spherically outwardly propagating flame (SPF) method. Mixtures with different compositions were analyzed under varying conditions, and the LBV was simulated using different mechanisms. The predicted results showed good agreement with the experimental measurements.