Experimental and numerical investigation of MILD combustion in a pilot-scale water heater

Ghasem Khabbazian, Javad Aminian and Ramin Haghighi Khoshkhoo

Energy, 2022, vol. 239, issue PA

Abstract: In the present study the effects of air preheating and dilution on stabilizing MILD (Moderate or Intense Low-oxygen Dilution) combustion of natural gas in a 100 kW jacket type water heater are investigated experimentally. The effects of FGR (flue gas recirculation) and flame heat loss on the self-ignition and extinction temperatures are analyzed numerically using a non-adiabatic WSR (Well-Stirred Reactor) model in the CHEMKIN software. Experimental results showed that the mechanical-process retrofitting techniques were successful to reach positive characteristics of the flameless combustion; e.g. uniform temperature distribution, improved efficiency (>10% increase), and lower NO emission (̴ 13% decrease), without the need to replace the conventional burner with modern flameless type or retrofitting the structure of combustion chamber. Based on the simulation results, a new combustion regime map for practical conditions encountering heat loss is developed. The new T-FGR-heat loss regime map shows that as heat loss increases the quasi-MILD region expands, whereas the MILD and MILD-like regions shrink and beyond a specific heat loss the HTC (high temperature combustion) zone disappears. The method of numerical visualization of experimental conditions on the combustion regime map is a simple powerful numerical tool to design practical flameless systems or retrofitting conventional devices.

Keywords: Flameless combustion; Non-adiabatic well-stirred reactor (WSR); Heat loss; Flue gas recirculation (FGR); Combustion regime map; Pollutant reduction; Fuel saving (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:239:y:2022:i:pa:s0360544221021368

DOI: 10.1016/j.energy.2021.121888

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