Lean Blowout Limit Prediction in a Combustor with the Pilot Flame

One of the important combustion chambers characteristic is the lean blowout (LBO) limits. There are several ways to expand LBO limits. One of them is using pilot flame. The present research relates to LBO modeling inside the combustor with the pilot flame. The simplified version of a power plant combustion chamber was used. The experimental data was used to validate the model. Experiments were conducted at the inlet air temperatures ranging from 373 to 575 K, and changing the relative flow rate of the pilot fuel from 0 to 1. Methane was used as the fuel. It was found that the minimum value of the φLBO can be achieved even when a portion of the fuel enters the pilot zone, and not only when the fuel is fully supplied to the pilot circuit. So φLBO can be reduced up to 4 times compared to supplying fuel only to main circuit. It is also shown that there is a correlation between φLBO and fuel/air equivalence ratio averaged over the surface of the recirculation zone φRF, that can be obtained as a result of RANS simulations without combustion. To generalize the collected data the φRF value, obtained for an arbitrary fuel distribution, was scaled to φLBO, obtained for supplying the fuel only in the main circuit. In this case φLBO value was calculated using LES approach for each air flow rate, pressure and initial temperature. As the result of the work, the methodology that allows to determine LBO limits of combustion chambers with the pilot flame was developed. The presented method is based on a series of steady and transient 3D simulations.