59777 - Prediction of Pressure Rise in a Gas Turbine Exhaust Duct Under Flameout Scenarios While Operating on Hydrogen and Natural Gas Blends 

In recent years, there is a growing interest in blending hydrogen with natural gas (NG) fuels to produce low carbon electricity. It is important to evaluate the safety of gas turbine packages under these conditions, such as the late-light off and flameout scenarios. However, the assessment of the safety risks by performing experiments in full-scale exhaust ducts is a very expensive and, potentially, risky endeavor. Computational simulations using a high fidelity LES CFD model provide a cost-effective way of assessing the safety risk. In this study an LES model for a three dimensional, compressible and unsteady simulation of a reacting flow in a gas turbine exhaust duct was validated against the test data obtained at simulated conditions in a representative geometry. Due to the enormous size of the geometry, especial attention was given to the discretization of the computational domain and treatment of boundary conditions. Various chemistry models and turbulent flame models were tested, and the parameters were selected for better comparison of the numerical predictions and test data. The paper presents the comparisons of test data and results of the LES simulations. Then, the predictions of pressure rise in typical gas turbine exhaust systems in the late light off and flameout scenarios using the LES model are presented and discussed.