Session: 04-04: Combustion Modeling I

Paper Number: 82583

82583 - Turbulent Combustion Modeling of Swirl Stabilized Blended CH4/H2 Flames by Using Flamelet Generated Manifold 

Hydrogen has been identified as one of the key elements of the decarbonization initiatives. The level of maturity with different original equipment manufacturers (OEMs) varies significantly for 100% H2 gas turbine combustor. The typical standard short-term goal is to blend hydrogen with existing fuel as a promising alternative to meet regulatory standards for emission. A typical Dry Low NOx (DLN) combustion system can handle a certain level of hydrogen blending. However, due to fundamental differences between the properties of hydrogen and methane, existing designs of combustion systems are not capable of handling moderate to high levels of hydrogen blending. Therefore, prior knowledge of blend ratios that a given combustion system can handle is essential for the system's stable operation. Computational fluid dynamic (CFD) simulation can help study the effect of different blend ratios on flame stability, peak temperature, pollutants, etc., without affecting the hardware. Thus, helping in reducing the overall cost and time spent in deciding the allowable blend ratios. 
In this work, the accuracy and consistency of Flamelet Generated Manifold (FGM) with large eddy simulation (LES) have been assessed to model swirling turbulent combustion of CH4/H2 blends for gas turbine engine combustors. FGM characterizes the extent of reaction using a reaction progress variable typically defined as a weighted sum of some representative product species of hydrocarbon combustion like CO and CO2. With H2 blending, the mixture now has multiple heat release time scales, and the prevailing choices of reaction progress definition are not optimal. Therefore, the first and foremost task is to correctly describe the reaction rate by choosing a reaction progress variable with validity over a range of H2 blending ratios and equivalence ratios. Additionally, the variation in the laminar properties of the blended mixture, e.g., thermal conductivity and viscosity, is enhanced when H2 is added to the fuel. In this work, we have used kinetic theory to compute these properties accurately as a function of temperature and composition.  The flame used to validate FGM in this work is CH4/H2 swirl flame (SMH1). The SMH1 configuration belongs to a detailed and widely simulated database from Sydney Swirl Burner, with a CH4/H2 blend ratio of 1:1 (by volume). The FGM is constructed by generating flamelets from opposed flow diffusion flames and freely propagating premix flame configuration. The solution of both the FGM approaches is compared with Finite Rate detailed chemistry solution, and definitive advantages/disadvantages of each approach are identified based on computational speed and accuracy. The results are then compared with experimental data for velocity, temperature, major and minor species distribution to establish the computational accuracy of each approach. Together with the inclusion of modifications in the modeling framework and usage of detailed chemistry with FGM-LES, these results provide important insights into the simulation of hydrogen-blended methane flames.
 

Presenting Author: Ishan Verma Ansys

Presenting Author Biography: Ishan Verma is based in Pune, India, and has been with Ansys for 8+ years. He is a Senior R&D Engineer in the Application Development team within the Fluids Development group. He has got his Master's Degree from IIT Delhi in Energy. For the past years, Ishan has worked in Gas Turbine Combustion, IC Engines, Spray Systems, Emission Control, and High-Speed Flows. He has actively worked with OEM teams from GE, Honeywell, Pratt & Whitney, Ferrari, Bosch, etc., and delivered high-value CFD solutions for engineering configurations. His hobbies include cycling, hiking, and traveling different regions of the world.

Authors:

Ishan Verma Ansys
Rakesh Yadav Ansys Inc
Sourabh Shrivastava Ansys Inc
Pravin Nakod Ansys Inc