Session: 04-15 Combustor Design III

Paper Number: 153464

Effect of Finite Mixing Timescales in Nonpremixed Rich Relaxation Lean (NRRL) Combustors 

A novel Nonpremixed Rich Relaxation Lean (NRRL) combustor concept was recently introduced as a method to enable fuel- and operational-flexibility in gas turbines. To review, the multistage combustor starts with a non-premixed zone, modeled as a portion of the overall air and fuel initially burning stoichiometrically, and whose products then mix with the remaining fuel. This mixture ideally relaxes to a rich equilibrium and then the balance of air is added, resulting in a lean burning zone. The critical steps in this process are the nonpremixed flame – which is inherently fuel flexible – and the relaxation zone which prefers longer residence times and higher pressures to reach low rich equilibrium NOx levels. Previous work focused on the fundamental chemical kinetic behavior of the concept and its underlying chemical timescales, mechanisms, and sensitivities to staging levels, residence times, and operating conditions. The purpose of this paper is to show how finite-rate fluid mechanics affect system performance, especially the relaxation dynamics and pre-flame mixing in the lean zone. These are modelled by introducing entrainment and mixing models into the 1D Lagrangian chemical reactor network used previously.  These reduced order models show that system performance is highly dependent on model fidelity and accuracy. A given model’s NOx emissions are also highly sensitive to certain mixing timescales.

Presenting Author: Shivam Patel Georgia Institute of Technology

Presenting Author Biography: Shivam is a PhD candidate in Tim Lieuwen's research group at Georgia Tech's Ben T Zinn combustion lab. He focuses on evaluating the feasibility of novel combustor architectures by blending insights from experimental data and computational analyses.

Authors:

Shivam Patel Georgia Institute of Technology
Benjamin Emerson Georgia Institute of Technology