Numerical and Experimental Investigations for Flow Fields Under Non-Reacting and Reacting Conditions Through a Lean Premixed Fuel Nozzle

Abstract

Numerical methods coupled with experimental benchmarking approaches, are typically used as effective tools for solving engineering problems due to their significant time saving benefits. In this paper, the swirling flow through an industrial lean-premixed fuel nozzle as used in actual gas turbine combustors is numerically analyzed and compared with experimental observations. The analysis is performed under both non-reacting and reacting conditions for a specific Reynolds number. The reacting experiments were performed using compressed methane as the fuel and air as the oxidizer. A specific inlet Reynolds number flow was studied to understand the combustor flow field with an overall equivalence ratio of 0.65 and 6% pilot fuel. Steady state simulations were performed using Fluent solver using Realizable k-ε turbulence model. The reacting flow was simulated using Flamelet Generation Manifold (FGM) model to simulate partially premixed combustion. The non-reacting simulations predicted the combustor flow profiles with certain deviation from Particle Image Velocimetry (PIV) data within the central recirculation region. This deviation may be attributed to the inherent limitations of turbulence model in predicting the central vortex accurately. However, the simulated flow fields were in very good agreement with PIV data under reacting conditions. Additionally, the study was also extended to investigate the sensitivity of inlet swirl on the jet impingement location along the combustor wall. It was found that reaction significantly modifies the jet impingement location for lower inlet swirl angles and showed negligible impact under non-reacting conditions. The presented studies in this paper provide a comprehensive summary of modified flow features under non-reacting and reacting conditions and also demonstrates the sensitivity of inlet swirl changes on the location of liner wall impingement. This study is believed to offer a strong base for future studies involving heat transfer characterization along the combustor walls under reacting conditions; and also provide valuable information to the gas turbine combustor design community towards improved liner wall designs using simplistic numerical modeling approaches.