TY - JOUR
T1 - Shock Tube Ignition Delay Data Affected by Localized Ignition Phenomena
AU - Javed, Tamour
AU - Badra, J.
AU - Jaasim, Mohammed
AU - Es-sebbar, Et-touhami
AU - Figueroa Labastida, Miguel
AU - Chung, Suk Ho
AU - Im, Hong G.
AU - Farooq, Aamir
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We would like to acknowledge the funding provided Saudi Aramco under the FUELCOM program and by King Abdullah University of Science and Technology (KAUST). We would like to thank Prof. Mani Sarathy (KAUST) for useful discussions on chemical kinetic mechanisms of n-alkanes.
PY - 2016/12/29
Y1 - 2016/12/29
N2 - Shock tubes have conventionally been used for measuring high-temperature ignition delay times ~ O(1 ms). In the last decade or so, the operating regime of shock tubes has been extended to lower temperatures by accessing longer observation times. Such measurements may potentially be affected by some non-ideal phenomena. The purpose of this work is to measure long ignition delay times for fuels exhibiting negative temperature coefficient (NTC) and to assess the impact of shock tube non-idealities on ignition delay data. Ignition delay times of n-heptane and n-hexane were measured over the temperature range of 650 – 1250 K and pressures near 1.5 atm. Driver gas tailoring and long length of shock tube driver section were utilized to measure ignition delay times as long as 32 ms. Measured ignition delay times agree with chemical kinetic models at high (> 1100 K) and low (< 700 K) temperatures. In the intermediate temperature range (700 – 1100 K), however, significant discrepancies are observed between the measurements and homogeneous ignition delay simulations. It is postulated, based on experimental observations, that localized ignition kernels could affect the ignition delay times at the intermediate temperatures, which lead to compression (and heating) of the bulk gas and result in expediting the overall ignition event. The postulate is validated through simple representative computational fluid dynamic simulations of post-shock gas mixtures which exhibit ignition advancement via a hot spot. The results of the current work show that ignition delay times measured by shock tubes may be affected by non-ideal phenomena for certain conditions of temperature, pressure and fuel reactivity. Care must, therefore, be exercised in using such data for chemical kinetic model development and validation.
AB - Shock tubes have conventionally been used for measuring high-temperature ignition delay times ~ O(1 ms). In the last decade or so, the operating regime of shock tubes has been extended to lower temperatures by accessing longer observation times. Such measurements may potentially be affected by some non-ideal phenomena. The purpose of this work is to measure long ignition delay times for fuels exhibiting negative temperature coefficient (NTC) and to assess the impact of shock tube non-idealities on ignition delay data. Ignition delay times of n-heptane and n-hexane were measured over the temperature range of 650 – 1250 K and pressures near 1.5 atm. Driver gas tailoring and long length of shock tube driver section were utilized to measure ignition delay times as long as 32 ms. Measured ignition delay times agree with chemical kinetic models at high (> 1100 K) and low (< 700 K) temperatures. In the intermediate temperature range (700 – 1100 K), however, significant discrepancies are observed between the measurements and homogeneous ignition delay simulations. It is postulated, based on experimental observations, that localized ignition kernels could affect the ignition delay times at the intermediate temperatures, which lead to compression (and heating) of the bulk gas and result in expediting the overall ignition event. The postulate is validated through simple representative computational fluid dynamic simulations of post-shock gas mixtures which exhibit ignition advancement via a hot spot. The results of the current work show that ignition delay times measured by shock tubes may be affected by non-ideal phenomena for certain conditions of temperature, pressure and fuel reactivity. Care must, therefore, be exercised in using such data for chemical kinetic model development and validation.
UR - http://hdl.handle.net/10754/623236
UR - http://www.tandfonline.com/doi/full/10.1080/00102202.2016.1272599
UR - http://www.scopus.com/inward/record.url?scp=85034666569&partnerID=8YFLogxK
U2 - 10.1080/00102202.2016.1272599
DO - 10.1080/00102202.2016.1272599
M3 - Article
SN - 0010-2202
VL - 189
SP - 1138
EP - 1161
JO - Combustion Science and Technology
JF - Combustion Science and Technology
IS - 7
ER -