Abstract
Rising apprehensions regarding greenhouse gas emissions have spurred extensive investigations into novel power generation cycles facilitating the capture and sequestration of carbon dioxide. Among these, oxy-fuel combustion is a promising pathway, as it produces flue gases with high CO2 concentrations that simplify sequestration. However, combustion in pure oxygen generates extremely high flame temperatures, necessitating robust cooling strategies to ensure stable and efficient operation. This study addresses this challenge by introducing an innovative burner design that integrates frontal water injection with triple coaxial swirlers to regulate flame temperature and enhance combustion stability. The burner comprises three concentric inlets, each equipped with opposing swirlers to intensify fuel-oxidizer mixing, while three frontal nozzles directly inject liquid water into the flame zone for precise temperature control. A computational model based on the k-ω SST (shear-stress transport) turbulence model and volumetric species transport was validated against cold-flow experiments, with the inclusion of surface roughness reducing numerical-experimental discrepancies from 25 % to 10.5 % at 400 kPa. Additionally, the trajectory of the injected droplet encompasses distinctive phases, each governed by specialized laws and equations pertaining to heat transfer, which involve inert heating, vaporization, and boiling. Combustion simulations examined water injection rates ranging from 0.05 to 1.5 g/s. Results show that water injection reduces recirculation zones, enhances flow uniformity, and provides precise temperature control. The critical outcome is that an injection rate of 1.5 g/s of water achieves the target outlet temperature of 1100 °C, enabling the operation of the Negative CO2 Emission Gas Power Plant (nCO2PP).