TY - JOUR
T1 - Role of low-temperature oxidation in non-uniform end-gas autoignition and strong pressure wave generation
AU - Terashima, Hiroshi
AU - Nakamura, Hisashi
AU - Matsugi, Akira
AU - Koshi, Mitsuo
N1 - Funding Information:
This study was supported by JSPS KAKENHI Grant No. JP17K06939 and by the research association of automotive internal combustion engines (AICE). This study was also carried out under the collaborative research project No. J19I072 and No. J20I045 of the Institute of Fluid Science, Tohoku University. The first author appreciates the support from Mr. T. Nogawa and Mr. K. Keta of Hokkaido University.
Publisher Copyright:
© 2020 The Combustion Institute
PY - 2021/1
Y1 - 2021/1
N2 - This study highlights the importance of heat release rate in low-temperature oxidation (LTO) on non-uniform end-gas autoignition and strong pressure wave generation, which are substantially relevant to knocking combustion. The simulations are conducted using the compressible Navier–Stokes equations with detailed transport and chemical kinetics models in a one-dimensional constant-volume reactor. Four fuel/air stoichiometric mixtures, n-butane, i-octane, n-heptane, and dimethyl ether (DME)/air mixtures, are simulated. The results show that larger knocking intensities are produced with n-heptane and DME in their negative temperature coefficient (NTC) regimes because of the stronger non-uniformity of end-gas autoignition. The non-uniformity of end-gas autoignition is enhanced by a pressure wave disturbance that is caused by the rapid temperature rise of the end-gas region in LTO. In particular, the high heat release rate with the DME/air mixture generates a distinct pressure wave disturbance in the reactor, which considerably enhances the non-uniformity of end-gas autoignition through the reflection of the wave at the wall. In contrast, the heat release rate in the n-heptane case is milder than that in the DME case, and therefore, the knocking intensity in the n-heptane case is smaller compared to that of DME due to less enhancement of the non-uniform end-gas autoignition. No large knocking intensities are produced with n-butane and i-octane, which have weak NTC, because of the absence of a temperature rise in LTO. Thus, this study concludes that the high heat release rate in LTO and the generated pressure wave disturbance play a significant role in the generation of large knocking intensities through the enhancement of non-uniform end-gas autoignition.
AB - This study highlights the importance of heat release rate in low-temperature oxidation (LTO) on non-uniform end-gas autoignition and strong pressure wave generation, which are substantially relevant to knocking combustion. The simulations are conducted using the compressible Navier–Stokes equations with detailed transport and chemical kinetics models in a one-dimensional constant-volume reactor. Four fuel/air stoichiometric mixtures, n-butane, i-octane, n-heptane, and dimethyl ether (DME)/air mixtures, are simulated. The results show that larger knocking intensities are produced with n-heptane and DME in their negative temperature coefficient (NTC) regimes because of the stronger non-uniformity of end-gas autoignition. The non-uniformity of end-gas autoignition is enhanced by a pressure wave disturbance that is caused by the rapid temperature rise of the end-gas region in LTO. In particular, the high heat release rate with the DME/air mixture generates a distinct pressure wave disturbance in the reactor, which considerably enhances the non-uniformity of end-gas autoignition through the reflection of the wave at the wall. In contrast, the heat release rate in the n-heptane case is milder than that in the DME case, and therefore, the knocking intensity in the n-heptane case is smaller compared to that of DME due to less enhancement of the non-uniform end-gas autoignition. No large knocking intensities are produced with n-butane and i-octane, which have weak NTC, because of the absence of a temperature rise in LTO. Thus, this study concludes that the high heat release rate in LTO and the generated pressure wave disturbance play a significant role in the generation of large knocking intensities through the enhancement of non-uniform end-gas autoignition.
KW - Detailed chemistry
KW - End-gas autoignition
KW - Knocking combustion
KW - Low-temperature chemistry
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U2 - 10.1016/j.combustflame.2020.09.025
DO - 10.1016/j.combustflame.2020.09.025
M3 - Article
AN - SCOPUS:85092531016
VL - 223
SP - 181
EP - 191
JO - Combustion and Flame
JF - Combustion and Flame
SN - 0010-2180
ER -