Highly scalable large-eddy simulations of oxy-fuel combustors for direct-fired supercritical CO2 power cycles

Direct-fired supercritical CO2 cycles are an emerging energy conversion technology that promises to increase power plant efficiency while capturing all CO2 emissions. However, given the novelty of the concept, experience is scarce when it comes to the practical design of the respective components. Especially the design of the combustor is challenging at high operating pressures of 200-300 bars, affecting fluid thermodynamics, combustion chemistry, and potentially introducing interactions with turbulence that were less eminent at lower, conventional combustor pressures. How addressed: In order to address these issues, we propose to develop high fidelity low-dissipation simulation capabilities (large eddy simulation computational fluid dynamics) for real fluid reactive mixtures, that can be used to solve practical engineering and design questions for realistically complex geometries. Phase I: The Phase I project involved an extensive evaluation of available models for high pressure thermodynamics, and a study of the sensitivity with respect to the combustion mechanism. Phase I allowed us to demonstrate the successful implementation of real fluid simulation capabilities for high pressure injection on one hand, and reactive simulations of a representative complex swirl injector on the other, based on state-of-the-art models originally developed for rocket combustion chamber simulations. Phase II:The purpose of the Phase II project is to combine these capabilities into a numerical tool that allows practical evaluation on the component level, in a detail that is beneficial for the design and analysis of practical combustor implementations. We intend to pursue a three-pronged approach, based on developing a high fidelity solver using state-of-the-art models for design questions, analyzing sensitivity of chemical and thermochemical models and their impact on flow solutions and predicted combustor performance, and assessing and avoiding the impact of combustion instabilities on effective combustor operation for practical designs.Commercial and other benefits:We expect that the results will advance the state-of-the-art in a number of fields. The successful Phase II project will facilitate an efficient and reliable realization of a direct-fired supercritical CO2 combustor using simulations, thus reducing the number of expensive and potentially dangerous experiments. Specifically, high fidelity simulations are capable of capturing physical phenomena that may degrade combustor performance and reliability, such as peak temperature distributions, acoustics, and thermo-acoustic instabilities. The new model can furthermore be used as a baseline to analyze other high-pressure combustion systems, such as gas turbines, Diesel engines, and rocket engines. Finally, we expect to advance insight into the physical behavior of such combustors, which represent an interaction of flow physics, chemistry, turbulence, and thermodynamics.