MILD combustion of methane in a model combustor with an inverse-diffusion flame configuration

Yaojie Tu, Hao Liu, Yuqi Zhu, Thibault Guiberti, William L. Roberts

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


MILD (moderate or intense low-oxygen dilution) combustion is a promising technology for mitigating NOx emission from fuel combustion, but the combustion stability becomes an issue when using low-preheat air due to the slower reaction at the burner exit. In this study, an inverse-diffusion flame (IDF) burner configuration is proposed to enhance the combustion stability of MILD regime. The burner features an earlier preheat of fuel stream instead of usually adopted air stream, and can be also operated in traditional diffusion swirling combustion mode. Experiments are conducted in a model combustor to examine the effect of varying burner load (P) and equivalence ratio (φ) on flame topology, pollutant (CO and NO) emission performance, as well as flame emitting spectrum for this burner. It shows that increasing P can enhance the combustion stabilities of both swirling mode and MILD mode, and MILD combustion is found unable to be sustained when P is lower than 2 kW. Increasing φ enlarges the flame liftoff distance under swirling combustion, but has a much smaller effect on MILD combustion. Emission data shows a nearly 50 % reduction of NO by MILD combustion comparing to swirling combustion in all operating cases. Spectra analysis suggests a higher sensitivity of the flame response to the operating parameters under swirling combustion in respect to MILD combustion. A longer combustion chamber is found to produce a lower CO emission but has negligible effect on NO emission. Flow field and temperature distributions by further numerical simulation clearly demonstrate the effectiveness of fuel preheat by adopting IDF burner configuration for enhancing the flame stability when adopting normal temperature air in MILD combustion.
Original languageEnglish (US)
Pages (from-to)125315
StatePublished - Jul 19 2022

Bibliographical note

KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: The authors acknowledge the financial support from National Natural Science Foundation of China (Grant 52006077). Yaojie specially acknowledge Mr. Yongzhao Li for his assistance during experiment, and also Prof. Yan Xiong at University of Chinese Academy of Sciences for valuable discussion.

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Organic Chemistry
  • General Chemical Engineering
  • Fuel Technology


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