Laminar flame speeds and ignition delay times for isopropyl nitrate and propane blends

Laminar flame speed and ignition delay time measurements are presented for blends of isopropyl-nitrate and propane. The laminar flame speeds were measured in a spherical bomb, with the majority of the experiments performed at 373 K and 1 bar, with equivalence ratios between 0.6 < Phi < 2.1; the fuel composition was 0%, 10%, and 100% isopropyl-nitrate. Additional experiments were performed at 300 K for pure propane as a fuel, and at 0.5 bar for pure isopropyl-nitrate as fuel. The ignition delay measurements were performed in a shock tube, with reflected shock temperatures between 1050 K and 1530 K and a nominal reflected shock pressure of 20 bar. Equivalence ratios of 0.5, 1.0, and 1.5 were considered for fuel blends with 0% and 1% isopropyl-nitrate in propane; additional experiments were performed with 10% isopropyl-nitrate at Phi = 1. In comparison with the pure propane flames, the pure isopropyl-nitrate have a similar peak flame speed ( S L0 = 60 . 3 cm/s at Phi = 1 . 09 for isopropyl-nitrate versus S L0 = 57 . 9 cm/s at Phi = 1 . 10 for propane), but the nitrate is considerably faster under fuel lean conditions, and it exhibits a much broader domain. The ignition delay times for 1% isopropyl-nitrate in propane are indistinguishable from the pure propane experiments for all three equivalence ratios. The 10% isopropyl-nitrate in propane mixture, in contrast, is significantly more reactive. Transition state theory calculations were performed for select RH + NO 2 reactions. These calculations were added to a recently developed mechanism for isopropyl-nitrate and propane. Detailed simulations of the experiments were performed in CANTERA . The agreement between the models and experiments is excellent. The largest discrepancies occur for the ignition delay times for 10% isopropyl-nitrate at T 5 < 1150 K and for the flame speeds for Phi > 1 . 8 , which suggests that further work needs to be done under these conditions. To the best of our knowledge, these data represent the first published results on the laminar flame speeds of any alkyl nitrate.(c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

This study investigates the laminar flame speed and ignition delay time of blends of isopropyl-nitrate and propane. The results show that under fuel-rich conditions, isopropyl-nitrate has a faster flame speed and a broader range. The ignition delay time of propane with 1% isopropyl-nitrate shows no significant difference compared to pure propane, while the addition of 10% isopropyl-nitrate exhibits higher reactivity.