PIV-Validated RANS Turbulence Modeling for Buoyant Supercritical CO2 Flows

At supercritical conditions, CO2 behaves in very complex ways. As a result, there is a lack of confidence in existing computational fluid dynamics approaches to simulating flows of supercritical CO2. Current models were developed for other physical simulations and either do not include the correct physics or are not validated for CO2 flows in the supercritical regime. As supercritical CO2 is increasingly being considered for use in power plants across the country, high fidelity, validated modeling methods are in high demand. The goal of this project is to develop a cost-effective turbulence model specifically designed for supercritical CO2 flows in direct-fired Brayton cycles. The model will build on existing knowledge of the mathematical structure and physical applicability of existing models to produce accurate simulations of flows including the phenomena most important to supercritical CO2 flows. Combustion processes induce strong changes in temperature and, there- fore, density. In order to address this, the model will focus on the effects of buoyancy in regions of heavy mixing. Computational fluid dynamics simulations will be set up to explore an advanced supercritical CO2 experimental apparatus. Various existing turbulence models will be used in order to gain insight into their effectiveness. Based on these studies a new turbulence model will be designed to specifically address the complexities of the flow. Concurrently, a feasibility study of using particle image velocimetry to measure flow through the supercritical CO2 facility will be conducted. A plan to implement the measurements during Phase II will be formulated and a study of required equipment performed. Commercial Applications and Other Benefits: The experience developed by this project will establish the company as leading experts in supercritical CO2 flows and fluid simulations in general. The company will then be well-positioned to compete for engineering services and engineering consultation contracts, benefiting the American public by contributing to better designed, safer, and affordable products and services from American companies. American competitiveness in power cycle engineering, which is being increasingly challenged by European and Asian markets, would additionally be bolstered. This project will also serve American interests through the production of high quality, curated experimental data for supercritical CO2 flows, which will incubate the domestic production of improved simulations and turbulence models by providing a route to validation.