Flame Stability Characteristics of Two-Dimensional Trapped Vortex Combustor

ABSTRACT

Flame stability characteristics of a two-dimensional (2D) trapped-vortex combustor (TVC) are investigated experimentally by considering two injection strategies, namely: (i) Inj-1 and (ii) Inj-2, for certain operating conditions. Injection strategy 1 (Inj-1) reinforces the shear driven stream-wise vortex flow structure within the cavity, whereas for Inj-2, a counter stream-wise vortex is established within the cavity. The study indicates that for a particular injection strategy, mainstream Reynolds number (Re_ms) and mainstream equivalence ratio (Φ_ms), the cavity fuel-flow rates have to be increased with the primary airflow rate for sustaining cavity flame. Besides this, for the same operating condition, Inj-1 has a wider flame stability limit as compared to that of the Inj-2 case. For the Inj-1 case, fuel-air distribution within the cavity is almost near stoichiometric; however, for the Inj-2 case, the cavity region is found to be fuel lean. Analysis of this result also indicates that cavity equivalence ratio (Φ_c) at the flame blowout condition increases with MFR up to a critical value, beyond which it drops down. This critical MFR value demarcates two physical situations, namely: (i) non-merged and (ii) merged cavity flames. Besides this, an attempt has been made to bring out the phenomenology of flame blowout by analyzing the natural luminosity images near blowout condition. Furthermore, a plausible mechanism for flame blowout is proposed for 2D TVC. A semi-empirical correlation for the flame blowout data in terms of Da and MFR is obtained in this work, which can be useful for the design and development of TVC in the future.

KEYWORDS:

• Flame blow out limit
• Static flame stability
• Trapped vortex

Acknowledgments

The authors are grateful for the support provided by graduate students, Combustion Laboratory, IITK in conducting experiments and members of the staff, Combustion Laboratory, IITK in fabricating the experimental setup.

Funding

The authors gratefully acknowledge the financial support (AE/DST/20100202) provided by the Department of Science and Technology (DST), New Delhi, India.

Additional information

Funding

The authors gratefully acknowledge the financial support (AE/DST/20100202) provided by the Department of Science and Technology (DST), New Delhi, India.