Options
Historical background of novel flameless combustion
Journal
Fundamentals of Low Emission Flameless Combustion and Its Applications
Date Issued
2022-01-01
Author(s)
Sharma, Saurabh
Kumar, Sudarshan
Abstract
This chapter sheds light on the historical development of the flameless combustion based on various numerical and experimental studies. The first section presents state of the art on discovering flameless combustion and preliminary investigations in industrial furnaces and burners. It is discussed that how a nonconventional combustion regime, achieved through specific flow and temperature conditions, helped lower the NOx emissions while maintaining the overall system efficiency. Modeling approaches for the flameless regime are discussed in detail using computational fluid dynamics. It is observed that both turbulence and chemistry equally drive the flameless regime, and hence, models accounting for better turbulence-chemistry interaction capture the flameless regime well. It is concluded based on the state-of-the-art survey that a standard/modified κ-ɛ model for turbulence works satisfactorily. For combustion modeling, the eddy dissipation concept with detailed chemical kinetics is required to capture the flameless combustion characteristics. This chapter also highlights the importance of the selection of combustor geometry and how it generates increased recirculation levels required to sustain flameless combustion conditions. Among the presented investigations, geometries based on a cyclonic flow field provide promising results regarding pollutant emissions. In the later sections of this chapter, flameless combustion's potential to burn low graded dirty fuels is discussed. It is presented how creating a heated and diluted environment can lead to clean burning of low calorific value fuels such as syngas, biogas, ammonia, coke oven gas, etc. It is observed that fuel flexibility is an inherent talent of this combustion regime, which is needed to be explored further in future studies. In the final section of this chapter, studies based on the applicability of flameless combustion in gas turbine engines are presented. The issues observed are high-pressure loss, narrow operational range, etc. Solutions in terms of fuel/air staging two-stage combustors are discussed.
Subjects