Research on characteristic chemical time scales for MILD combustion based on partition PCA method.

• A new method is proposed to calculate characteristic chemical reaction time scales by partition PCA method for MILD combustion. • The partition PCA method segments combustion regions based on reaction intensity and extracts characteristic chemical time scales for each region. • Revealed a closer alignment with the inherent nature of MILD combustion, by applying the method to a CH4/H2 mixture in both MILD and standard combustion processes. MILD combustion represents a more moderated reaction process in contrast to traditional combustion. The employment of hydrogen-containing syngas as fuel introduces a spectrum of intricate and diverse chemical reactions. This complexity renders traditional reliance on characteristic chemical timescales less appropriate for the analysis and modeling of Moderate or Intense Low-oxygen Dilution (MILD) combustion phenomena. In response to this inadequacy, a new technique named the partition Principal Component Analysis (PCA) method was developed. This method begins by segmenting combustion regions based on the reaction intensity, then extracts characteristic chemical time scales for each of these individual regions through the application of the PCA method. The innovative method was subsequently applied to investigate the chemical traits of the CH 4 /H 2 mixture in both MILD and standard combustion processes with respect to the time scale. The insights obtained from this novel approach demonstrate that the characteristic chemical time scales (τ c) deduced through this methodology exhibit a more accurate representation of the intrinsic characteristics of MILD combustion within the reaction region. This approach enhances the comprehension of the interplay between turbulence and chemistry in MILD combustion contexts. Furthermore, it establishes a solid groundwork for forthcoming research endeavors in the field of MILD combustion. Furthermore, the τ c calculations presented in this paper have been derived mathematically, confirming their widespread applicability. [ABSTRACT FROM AUTHOR]