Development of OpenFOAM-based Frameworks for Numerical Studies of sCO2 Combustion and Catalytic Ammonia Combustion

Abstract

Recently, significant research focus in the power generation sector has shifted to the direct fired supercritical carbon dioxide (sCO2) power cycle and ammonia and/or blended am- monia/hydrogen combustion to meet carbon neutrality by 2050. The sCO2 power cycle is characterized by extreme operating conditions such that the turbine inlet temperature is typically maintained at 1100 to 1400 K and the pressure ranges from 200 to 300 bar. Experimental studies under such operating conditions have been restricted by limita- tions of available techniques except for a few experimental observations. The numerical investigation on this topic is also challenging due to limitations of the available Com- putational Fluid Dynamics (CFD) tools. For blended ammonia/hydrogen combustion, on-site hydrogen production through catalytic ammonia decomposition plays an impor- tant role. While many experimental studies on the hydrogen production from catalytic ammonia decomposition have been conducted, the numerical investigation on this field is limited due to lacking sufficient CFD packages to handle surface reactions occurring in catalytic processes. Therefore, objectives of this research are development and validation of predictive models or modeling approaches for numerical investigations of sCO2 com- bustion and catalytic ammonia combustion. The main goal is to combine good physical insights, appropriate numerical methods, and good software development to create suffi- cient frameworks in OpenFOAM platform, a free and robust open-source CFD package, providing powerful CFD tools for researchers working on these fields. The first stage of the research aimed to develop a new library encompassing various widely used real-fluid models. In this stage, a novel algorithm applicable for a mix- ture model incorporating various mixing rules in OpenFOAM was introduced. Based on the proposed algorithm, the thermophysicalModels library of OpenFOAM (version 6.0) was updated by implementing a set of real-fluid models such as the Soave-Redlich- Kwong/Peng-Robinson equation of state, Chung’s model for dynamic viscosity and ther- mal conductivity, mixture averaged model for mass diffusivity using Takahashi’s cor- rection for binary diffusion coefficients at high pressure. The new library was validated against experimental data and was further assessed for compressible reacting flows by per- forming two-dimensional numerical simulations of axisymmetric laminar non-premixed counterflow flames of CH4 /CO2-O2 and one-dimensional numerical simulations of pre- mixed CH4/air flames at high pressures. The developed library can be used for any reacting flow solver in OpenFOAM (version 6.0) that adopts a set of implemented real- fluid models. In the second stage of this study, a pressure-based solver named realFluidFoam was developed for simulations of subsonic turbulent non-reacting flows at transcritical and su- percritical conditions in OpenFOAM (version 6.0). The developed solver utilized unique algorithms available in the literature to enhance stability and convergency while taking into account real-fluid effects. The implementation details and its source code were pro- vided to facilitate a comprehensive understanding of integrating real-fluid models into fluid flow simulations in OpenFOAM. The realFluidFoam solver was validated against experimental data by performing large-eddy simulations (LESs) of liquid nitrogen in- jection and coaxial liquid nitrogen/preheated hydrogen injection under transcritical and supercritical conditions. The LES results showed a satisfactory agreement with the exper- imental data, verifying that the realFluidFoam solver can accurately simulate transcritical and supercritical turbulent fluid flows over the wide range of pressure, especially near the critical points. In the third stage of the study, a novel framework named realFluid3sSLFMFoam con- sisting of various libraries and solvers was introduced (based on OpenFOAM version 6.0) for simulations of turbulent non-premixed flames (in both RANS and LES contexts) us- ing three-stream steady laminar flamelet model under wide range of pressure conditions (i.e., from atmospheric to supercritical conditions). Its implementation details and source code were provided for public use. The developed code was validated against experimental data and a previous study. Particularly, the piloted Sandia flame D and HM3 flame were replicated. A satisfactory agreement between the numerical predictions from the devel- oped framework and benchmark data were observed, verifying that the implementation was proper, and suitable for simulating turbulent non-premixed flames with reasonable computational cost. The framework was then utilized to simulate a simplified gas turbine combustor of sCO2 power cycle. The results exhibited that the realFluid3sSLFMFoam is a powerful CFD tool for numerical investigations on sCO2 combustion. The final stage of the study focused on the development of a new framework for cat- alytic ammonia combustion investigation. Specifically, in this framework a novel library (based on OpenFOAM version 8.0) named surfaceChemistryModels was introduced. The developed library can handle several types of typical surface reaction rate models consist- ing of the basic Arrheninus form, sticking coefficient, and surface coverage dependence models. Along with this library, a new solver was also developed for simulations of catalytic combustion processes with the utilizations of detailed micro chemical kinetic models. The developed code was then validated against experimental data and previous studies by performing simulations catalytic ammonia decomposition in fixed packed-bed reactors. The results showed a good agreement between predicted and benchmark data, validating the accuracy and applicabilities of the developed framework for numerical in- vestigations on catalytic ammonia combustion. In summary, two OpenFOAM-based frameworks have been developed for numerical investigations of sCO2 combustion and catalytic ammonia combustion. Their source code and implementation descriptions were provided for public use, offering not only powerful CFD tools for numerical combustion investigations but also in-depth understanding on the numerical models that were implemented in this study.