TY - GEN
T1 - Effects of thermal and compositional gradients and turbulence transport on detonation formation
AU - Zhang, Tianhan
AU - Sun, Weiqi
AU - Wang, Liang
AU - Ju, Yiguang
N1 - Funding Information:
Figure 5 The pressure and temperature distributions along the centerline for Case 1, Case 2, Case 3 and Case 4. For Case 1 and Case 2: 1: 385 μs, 2:386 μs, 3: 387 μs, 4: 388 μs. 4. Conclusion The effects of thermal and fuel stratification and turbulent transport on knocking formation are numerically modeled in the negative temperature coefficient region using dimethyl ether/air mixtures with a detailed chemistry. The critical conditions of detonation formation with thermal and fuel concentration gradients are examined. The effects of turbulence timescales on knocking development and knocking strength are explored. The results show that either a thermal gradient, concentration gradient, or combine gradients can initiate knocking. A unified criterion and diagram for detonation formation including coupled thermal and fuel concentration gradients as well as the normalized length scale of gradient fields is demonstrated. The results show that turbulence transport can delay knocking/detonation transition and dramatically reduce detonation strength due to turbulent mixing. It is found that when turbulence timescale is much shorter than the ignition delay time of the gradient field, the knocking formation will be inhibited. The present research provides important insights of knocking formation and control of knocking using stratifications and turbulence in the real engines. 5. Acknowledgement The authors would like to thank the grant support from the Army Research Office with grant number W911NF-16-1-0076. Reference [1] R. H. Thring, “Homogeneous-Charge Compression-Ignition (HCCI) Engines,” in SAE Technical Paper, 1989. [2] S. L. Kokjohn, R. M. Hanson, D. a. Splitter, and R. D. Reitz, “Fuel reactivity controlled compression ignition (RCCI): a pathway to controlled high-efficiency clean combustion,” Int. J. Engine Res., vol. 12, no. 3, pp. 209–226, Jun. 2011. [3] L. Manofsky, J. Vavra, D. N. Assanis, and A. Babajimopoulos, “Bridging the Gap between HCCI and SI: Spark-Assisted Compression Ignition,” in SAE Technical Paper, 2011. [4] G. T. Kalghatgi, “Developments in internal combustion engines and implications for combustion science and future transport fuels,” Proc. Combust. Inst., vol. 35, no. 1, pp. 101–115, 2015. [5] Y. Zeldovich, “Regime classification of an exothermic reaction with nonuniform initial conditions,” Combust. Flame, vol. 39, no. 2, pp. 211–214, Oct. 1980.
Publisher Copyright:
© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2019
Y1 - 2019
N2 - The effects of thermal and fuel stratification and turbulent transport on knocking formation are numerically modeled in the negative temperature coefficient (NTC) region using dimethyl ether/air mixtures with a detailed chemistry. The critical conditions of knocking formation with thermal and fuel concentration gradients are examined. The effects of turbulence timescales on knocking development and knocking strength are explored. The results show that either a thermal gradient, concentration gradient, or combine gradients can initiate knocking. A unified criterion and diagram for knocking formation including both thermal and fuel concentration gradients as well as the normalized length scale of gradient fields is demonstrated. The results show that turbulence transport can delay knocking/detonation transition and dramatically reduce detonation strength due to turbulent mixing. It is found that when turbulence timescale is much shorter than the ignition delay time of the gradient field, the knocking formation will be suppressed. The present research provides important insights of knocking formation and control of knocking using stratifications and turbulence in the real engines.
AB - The effects of thermal and fuel stratification and turbulent transport on knocking formation are numerically modeled in the negative temperature coefficient (NTC) region using dimethyl ether/air mixtures with a detailed chemistry. The critical conditions of knocking formation with thermal and fuel concentration gradients are examined. The effects of turbulence timescales on knocking development and knocking strength are explored. The results show that either a thermal gradient, concentration gradient, or combine gradients can initiate knocking. A unified criterion and diagram for knocking formation including both thermal and fuel concentration gradients as well as the normalized length scale of gradient fields is demonstrated. The results show that turbulence transport can delay knocking/detonation transition and dramatically reduce detonation strength due to turbulent mixing. It is found that when turbulence timescale is much shorter than the ignition delay time of the gradient field, the knocking formation will be suppressed. The present research provides important insights of knocking formation and control of knocking using stratifications and turbulence in the real engines.
KW - Concentration gradient
KW - Knocking and detonation
KW - Temperature gradient introduction
KW - Turbulent transport
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U2 - 10.2514/6.2019-0188
DO - 10.2514/6.2019-0188
M3 - Conference contribution
AN - SCOPUS:85083941978
SN - 9781624105784
T3 - AIAA Scitech 2019 Forum
BT - AIAA Scitech 2019 Forum
PB - American Institute of Aeronautics and Astronautics Inc, AIAA
T2 - AIAA Scitech Forum, 2019
Y2 - 7 January 2019 through 11 January 2019
ER -