Effect of NO2 addition on the oxidation kinetics of n-pentane and natural gas blends with C1–C5 n-alkanes
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Bibliographic record
Abstract
This study presents new ignition delay time (IDT) data for NO 2 blended multi-component natural gas mixtures with methane as the major component including C 2 –C 5 primary n -alkanes in different concentrations. The data are measured using a high-pressure shock tube and a rapid compression machine at compression pressures of 20 and 30 bar in the temperature range of 715–1480 K for stoichiometric mixtures. This paper builds upon our previous work on the development of a C 1 –C 3 /NOx kinetic mechanism and focusses on understanding the interaction chemistry of heavier n- alkane/NOx mixtures by determining the IDT characteristics of various NO 2 blended n- C 5 H 12 /air combinations with 200, 400 and 1000 ppm concentrations of NO 2 present at compression pressures of 10, 20 and 30 bar. The newly measured IDT results and existing experimental data from the literature are used to improve model predictions for the oxidation of n- C 4 H 10 /NOx, n- C 5 H 12 /NOx, NG2/NOx, and NG3/NOx by updating NUIGMech1.2. The improvement in the performance of GalwayMech1.0 is attributed to updated rate constants for the n- C 5 H 12 + NO 2 ↔ Ċ 5 H 11 –1, -2, -3 + HONO reactions as well as the inclusion of Ṙ + NO 2 ↔ RONO reaction channels. The IDT decreased slightly when 1000 ppm of NO 2 is added to n- pentane, which contrasts with propane (C 3 H 8 ), where there was a significant decrease in the mixture reactivity as reported previously (A. A. E. S. Mohamed, A. B. Sahu, S. Panigrahy, M. Baigmohammadi, G. Bourque, H.J. Curran, The effect of the addition of nitrogen oxides on the oxidation of propane: An experimental and modeling study. Combust. Flame 245 (2022) 112306). This is because the competition between NO 2 and O 2 for 1-propyl radicals formed by H-atom abstraction from C 3 H 8 decreases mixture reactivity, while in the case of n- C 5 H 12 , although NO 2 and O 2 compete for 1-pentyl radicals, the increase in reactivity is facilitated by the availability of 2-pentyl radicals in the system which also leads to chain branching when they add to O 2 , unlike 2-propyl ( iso -propyl) radicals which ultimately do not lead to chain branching in the oxidation of propane.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it