Lean Blow-Out analysis for the performance assessment of advanced burner designs operating under CO2-diluted air conditions using a high-fidelity CFD approach

Abstract

Amid the growing focus on sustainable industrial practices, Carbon Capture and Storage (CCS) systems are becoming increasingly essential for reducing the carbon footprint of Gas Turbine (GT) power generation. In this context, an efficient GT-CCS coupling can be achieved by employing high Exhaust Gas Recirculation (EGR) rates to boost CO₂ content at the CCS inlet. However, the reduced oxygen levels resulting from these operating conditions pose significant challenges to conventional combustion systems, limiting flame stability and, consequently, engine operability. Overcoming these challenges requires the development of novel technical solutions aimed at enhancing combustor performance under high EGR rates.

Computational Fluid Dynamics (CFD) is crucial in this endeavour offering detailed analysis of intricate flow behaviours, mixing process dynamics, flame structures, and stability thresholds within the combustor. Given the demand for extensive simulations to assess flame stability across various burner designs and operating conditions, balancing the necessity for high accuracy while keeping computational expenses in check is mandatory.

This study employs a high-fidelity CFD approach to perform a comprehensive Lean Blow-Out (LBO) analysis, with the goal of identifying burner designs that exhibit broader operability limits under highly CO₂-diluted air conditions, which emulate the effects of a real EGR system. All simulations utilise an extended Flamelet Generated Manifold (FGM) turbulent combustion model, whose accuracy and cost-effectiveness have been previously validated by the authors.

The numerical results demonstrate the capability of CFD to identify unique blow-off dynamics that are challenging to observe experimentally. Additionally, the findings highlight the most effective design strategy for extending the flame stability range under high EGR levels.