A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology

doi:10.1016/j.cjche.2020.09.053

Chinese Journal of Chemical Engineering ›› 2021, Vol. 32 ›› Issue (4): 108-118.DOI: 10.1016/j.cjche.2020.09.053

• Fluid Dynamics and Transport Phenomena • Previous Articles Next Articles

A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology

Mengqian Xie^1,2, Fangqin Dai^1,2, Yaojie Tu³

1 The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China;
2 Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China;
3 School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Received:2020-05-22 Revised:2020-08-25 Online:2021-06-19 Published:2021-04-28
Contact: Yaojie Tu
Supported by:
Yaojie Tu gratefully acknowledges the financial support from the National Natural Science Foundation of China (52006077) and Innovation Research Foundation of Huazhong University of Science and Technology (5001120031).

A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology

Mengqian Xie^1,2, Fangqin Dai^1,2, Yaojie Tu³

1 The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China;
2 Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, China;
3 School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

通讯作者: Yaojie Tu
基金资助:
Yaojie Tu gratefully acknowledges the financial support from the National Natural Science Foundation of China (52006077) and Innovation Research Foundation of Huazhong University of Science and Technology (5001120031).

Abstract

Abstract: Moderate or intense low-oxygen dilution (MILD) combustion has become a promising low-NO_X emission technology, while the delayed mixing of reactants and slower oxidation rate could potentially cause ignition instability in some scenarios. This paper proposes a new idea for enhancing the ignition stability for methane MILD combustion by combining with off-stoichiometric combustion (OSC), and its performances have been numerically assessed through a comparison against the original MILD combustion burner. The results reveal although non-premixed pattern has the lowest NO emission, it suffers from a larger liftoff distance, thus less ignition stability. Contrarily, both partially-premixed and fully premixed patterns exhibit excellent ignition stability. Among the considered OSC conditions, the pattern of Inner ultra-rich and Outer lean produces the lowest NO emission while maintains a high ignition stability. Furthermore, the enhancement of the combustion stability by implementing OSC to the original MILD combustion burner is shown by comparing the operational range of furnace wall temperature (T_f), CO and NO emissions, as well as the evolution of chemical flame. The comparison reveals that OSC can extend the lowest operational T_f from 900 K to 800 K. More importantly, OSC can significantly improve the ignition stability in the whole range of T_f as compared to the original MILD combustion burner.

Key words: MILD combustion, Off-stoichiometric combustion, NO emission, Ignition instability, Burner design

摘要： Moderate or intense low-oxygen dilution (MILD) combustion has become a promising low-NO_X emission technology, while the delayed mixing of reactants and slower oxidation rate could potentially cause ignition instability in some scenarios. This paper proposes a new idea for enhancing the ignition stability for methane MILD combustion by combining with off-stoichiometric combustion (OSC), and its performances have been numerically assessed through a comparison against the original MILD combustion burner. The results reveal although non-premixed pattern has the lowest NO emission, it suffers from a larger liftoff distance, thus less ignition stability. Contrarily, both partially-premixed and fully premixed patterns exhibit excellent ignition stability. Among the considered OSC conditions, the pattern of Inner ultra-rich and Outer lean produces the lowest NO emission while maintains a high ignition stability. Furthermore, the enhancement of the combustion stability by implementing OSC to the original MILD combustion burner is shown by comparing the operational range of furnace wall temperature (T_f), CO and NO emissions, as well as the evolution of chemical flame. The comparison reveals that OSC can extend the lowest operational T_f from 900 K to 800 K. More importantly, OSC can significantly improve the ignition stability in the whole range of T_f as compared to the original MILD combustion burner.

关键词: MILD combustion, Off-stoichiometric combustion, NO emission, Ignition instability, Burner design

Mengqian Xie, Fangqin Dai, Yaojie Tu. A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology[J]. Chinese Journal of Chemical Engineering, 2021, 32(4): 108-118.

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A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology

A numerical study of accelerated moderate or intense low-oxygen dilution (MILD) combustion stability for methane in a lab-scale furnace by off-stoichiometric combustion technology

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