Shock tube experiments and numerical study on ignition delay times of ethane in super lean and ultra-lean combustion

Super lean (usually (1) < 0.5) and ultra-lean (usually (1) < 0.3) combustion are regarded as promising combustion techniques owing to high fuel economy and low emission. Ethane is one of the key compo-nents of natural gas. In the present study, the ignition delay times (IDTs) of ethane/oxygen/argon mixture were measured behind reflected shock waves at three equivalence ratios of 0.5, 0.1, 0.05, two pressures of 1.68, 9.0 atm, and in the temperature range of 1120 - 1351 K. The OXYMECH2.0, proposed in our pre-vious works, is modified in the present study by updating several elementary reactions. The modified OXYMECH is validated by ethane IDTs of super lean combustion measured in the present study, in high CO2 atmospheres and O2/Ar atmospheres from the literature as well as laminar flame speeds (LFSs) un-der O2/N2 and O2/CO2 atmospheres. Aramco3.0, San Diego, NUIGMech0.9, and CRECK-GB models are also evaluated by ethane IDTs measured in the present study, the results show that modified OXYMECH, NUIG-Mech0.9, and CRECK-GB models provide equally accurate predictions for experiments. The NUIG Mech0.9 and CRECK-GB are further evaluated using the ethane IDTs in high CO2 atmospheres and experimental LFSs of ethane under O2/N2 and O2/CO2 atmospheres, the results show that modified OXYMECH has good performance in predicting IDTs and LFSs of ethane. The detailed comparisons of IDTs and LFSs predic-tion between modified OXYMECH and CRECK-GB models are conducted. The effects of superabundant air, which is the air excess with equivalence ratio decreases from (1)1 to (1)2 , on the ignition in super lean combustion consist of the dilution and oxidation effects, which are studied in the present study in detail. It is very interesting that the dilution effects promote the ignition while the oxidation effects inhibit the ignition at (1) < 0.3 and P = 9.0 atm.(c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.