Session: 04-13: Kinetics

Paper Number: 82269

82269 - Metamodelling of Ignition Delay Time for Natural Gas Blends Under Gas Turbine Operating Conditions 

Characterisation of autoignition risk is crucial for designing and optimising low-emission combustion systems as there is an increased demand for highly reactive and novel fuel mixtures such as hydrogen and hydrogen-enriched natural gas.  Achieving a residence time to prevent autoignition and obtaining an adequate mixing quality is a challenging trade-off for these fuels in lean-premixed combustion systems. The level of complexity increases further due to low-temperature chemical pathways and pressure-dependent reactions that strongly influence ignition delay at engine operating conditions. Detailed chemical kinetic mechanisms with hundreds of species and thousands of reactions are developed and employed to address this complexity and predict ignition delay accurately, especially for heavier hydrocarbons. However, direct implementation of these kinetic mechanisms is computationally prohibitive in high-fidelity CFD approaches such as large eddy simulation (LES) and stochastic simulation tools that require a large number of evaluations. Advanced stochastic methods are essential tools to quantify uncertainties due to the inherent variabilities in ambient, operating conditions and fuel composition on ignition delay time calculation for practical applications. This study introduces and implements a computationally efficient method based on metamodelling to predict ignition delay time over a wide range of operating conditions and fuel compositions for gas turbine combustion systems. A metamodel or surrogate model is an accurate and quick approximation of the original computational model based on a detailed chemical kinetic mechanism. Advanced methods such as polynomial chaos expansion (PCE) and Gaussian process (GP) are employed to build metamodels using a limited set of runs of the original ignition delay time model based on NUIGMech1.0 as the most detailed and state-of-the-art chemical kinetic mechanism. Developed metamodels for ignition delay time are valid over operating conditions of and for natural gas, C₁-C₇ and hydrogen-enriched natural gas, H₂/C₁-C₇  at stoichiometric condition. These metamodels provide a fast, robust, and considerably accurate framework instead of a detailed chemical kinetic model that facilitates (a) characterising ignition delay time at different operating conditions and fuel compositions, (b) designing and optimising premixers and burners and (c) conducting uncertainty quantification and stochastic modelling studies.

Presenting Author: Sajjad Yousefian National University of Ireland, Galway

Presenting Author Biography: Sajjad is a postdoctoral researcher in Mechanical Engineering at the National University of Ireland, Galway. He has five years of industrial experience in the field of gas turbine combustion systems. His research interests include uncertainty quantification, emissions modelling, CFD and machine learning.

Authors:

Sajjad Yousefian National University of Ireland, Galway
Gilles Bourque Siemens Energy Canada Ltd
Rory F. D. Monaghan National University of Ireland Galway