Characterisation of two-stage ignition in diesel engine-relevant thermochemical conditions using direct numerical simulation

Journal Article · Tue Aug 30 00:00:00 EDT 2016 · Combustion and Flame

DOI:https://doi.org/10.1016/j.combustflame.2016.06.010· OSTI ID:1326054

Krisman, Alex  ^[1]; Hawkes, Evatt R. ^[2]; Talei, Mohsen ^[3]; Bhagatwala, Ankit ^[4]; Chen, Jacqueline H. ^[4]

---

1. Sandia National Lab. (SNL-CA), Livermore, CA (United States); The Univ. of New South Wales, Sydney, NSW (Australia)
2. The Univ. of New South Wales, Sydney, NSW (Australia)
3. The Univ. of Melbourne, Melbourne, VIC (Australia)
4. Sandia National Lab. (SNL-CA), Livermore, CA (United States)

With the goal of providing a more detailed fundamental understanding of ignition processes in diesel engines, this study reports analysis of a direct numerical simulation (DNS) database. In the DNS, a pseudo turbulent mixing layer of dimethyl ether (DME) at 400 K and air at 900 K is simulated at a pressure of 40 atmospheres. At these conditions, DME exhibits a two-stage ignition and resides within the negative temperature coefficient (NTC) regime of ignition delay times, similar to diesel fuel. The analysis reveals a complex ignition process with several novel features. Autoignition occurs as a distributed, two-stage event. The high-temperature stage of ignition establishes edge flames that have a hybrid premixed/autoignition flame structure similar to that previously observed for lifted laminar flames at similar thermochemical conditions. In conclusion, a combustion mode analysis based on key radical species illustrates the multi-stage and multi-mode nature of the ignition process and highlights the substantial modelling challenge presented by diesel combustion.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Combustion Energy Frontier Research Center (CEFRC); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC04-94AL85000; SC0001198
• OSTI ID: 1326054
• Alternate ID(s): OSTI ID: 1358971
• Report Number(s): SAND-2016-5708J; 643523
• Journal Information: Combustion and Flame, Vol. 172, Issue C; ISSN 0010-2180
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

97 MATHEMATICS AND COMPUTING
33 ADVANCED PROPULSION SYSTEMS
diesel-relevant
autoignition
edge flame
cool flame
negative temperature coefficient
direct numerical simulation