60232 - Comparison of Performance of Flamelet Generated Manifold Model With That of Finite Rate Combustion Model for Hydrogen Blended Flames 

International Air Transport Association (IATA) sets a target of a 50% reduction in 2005 CO₂ emissions levels by 2050, with no increase in net emissions after 2020 [1]. The association also expects that the global aviation demand to double to 8.2 billion passengers per year by 2037. Both these issues have prompted the aviation industry to strongly focus on the adoption of sustainable aviation fuels (SAF). Further, reduction in CO2 emission is also an active area of research for land-based power generation gas turbine engines, and fuels with high hydrogen content or hydrogen blends are regarded as an important part of future power plants. Clean hydrogen and other hydrogen-based fuels are, therefore, expected to play a key role in helping the reduction of greenhouse gas emissions in the future. However, the large difference in the physical properties of hydrogen compared to hydrocarbon fuels, ignition and flashback issues are some of the major concerns at present and a detailed understanding of combustion characteristics of hydrogen for the conditions at which gas turbines operate is needed. Numerical combustion analyses can play an important role in the exploration of the combustion performance of hydrogen as an alternative gas turbine engine fuel. While several combustion models are available in the literature, two of the most preferred models in recent times are the flamelet generated manifold (FGM) model and finite-rate combustion model. FGM combustion model is computationally economical compared to the detailed/reduced chemistry modeling using a finite-rate combustion model and therefore, the objective of this paper is to understand the performance of the FGM model compared to detailed chemistry modeling of turbulent flames with different levels of hydrogen blended fuels.

In this paper, a detailed comparison of different combustion characteristics like temperature, species, flow, and NOx distribution using FGM and finite rate combustion models is presented for three flame configurations including the dry-low-NOx hydrogen micro-mix combustion chamber [2],  DLR Stuttgart jet flame [3] and Swirling Methane/Hydrogen Flame [4]. One of the important parameters in the FGM model is to select an appropriate definition of reaction progress variable such that the reaction progress monotonically increases from the unburnt region to the burnt region. This is first studied using a 1D premixed flame with different blend ratios and then used for the actual cases. 3D simulations for the identified flames are performed using FGM and finite rate combustion models. Numerical results from both these models are compared with the available experimental data to understand the applicability of FGM and the results show that the FGM model performs reasonably well for pure hydrogen as well as hydrogen blended flames.

References:

1.     International Air Transport Association (2020) Climate Change https://www.iata.org/en/programs/environment/climate-change

2.     Funke, H., Keinz, J., Kusterer, K., Haj Ayed, A., Kazari, M., Kitajima, J., Horikawa, A., and Okada, K., 2015, “Experimental and Numerical Study on Optimizing the DLN Micro-mix Hydrogen Combustion Principle for Industrial Gas Turbine Applications,” ASME Paper No. GT2015-42043

3.     CH4/H2/N2 Jet Flames https://www.sandia.gov/TNF/DataArch/DLRflames.html

4.     Swirl Flows and Flames Database http://web.aeromech.usyd.edu.au/thermofluids/swirl.php

Keywords: Hydrogen Combustion, FGM Combustion Model, Jet Flames, Swirl Burner