Articles written in Sadhana
Volume 45 All articles Published: 31 August 2020 Article ID 0222
Lean premixed combustion is a state-of-the-art technology to meet the stringent emission norms, especially to reduce the NOx emission. In the present study, we focus on the transition to lean blowout of premixed flames. The main objective of the study is to explore some important measures for prediction of leanblowout as the existing methods are not always suitable in early detection of blowout in case of premixed flames. We further consider different cases through which lean condition can be attained. For such cases, we first discussthe flame dynamics prior to blowout. Among different statistical measures, mean, median, root mean square and coefficient of variance of heat release rate fluctuations are found to be useful in blowout prediction. On the otherhand, skewness and excess of kurtosis do not show any predictive quality. We also observe that the flickering frequency defined in a specific manner also shows a significant variation near lean blowout. Further, the meanfrequency evaluated using Hilbert transform is found to show indication of LBO well before its occurrence. Therefore, the frequency analysis along with statistical analysis of the heat release rate oscillations is found to be very relevant in the context of blowout prediction and can be applied in the practical combustors.
Volume 45 All articles Published: 7 September 2020 Article ID 0230
In order to improve flame stabilization in small scale combustors, there have been many research works going on non-premixed as well as on premixed flame. The present experimental study characterizes colour and shape of the premixed and non-premixed flames through a laminar co-flow burner. Various flamebehaviors are observed and their stabilization limits are investigated at different fuel–air ratios. The spectroscopic approach becomes suitable method for the measurement of chemiluminescensce for both premixed and diffusion flames. Thus, we can predict the behavior of a combustion process. We observe also the intensity variation of chemiluminescence species, OH*, CH*, and C2* for different fuel-air flow combinations. Apart from that, we have an analysis of colour variance of the premixed flame for different flame locations