Original Research ARTICLE
Modelling pollutant emissions of Flameless Combustion with a joint CFD and Chemical Reactor Network approach
- 1Delft University of Technology, Netherlands
The Flameless Combustion (FC) regime has been pointed out as a promising combustion technique to lower the emissions of nitrogen oxides (NOx) while maintaining low CO and soot emissions, as well as high efficiencies. However, its accurate modelling remains a challenge. The prediction of pollutant species, especially NOx, is affected by the usually low total values that require higher precision from computational tools, as well as the incorporation of relevant formation pathways within the overall reaction mechanism that are usually neglected. The present work explores a multiple step modelling approach to tackle these issues. Initially, a CFD solution with simplified chemistry is generated (both the Eddy Dissipation Model as well as the Flamelet Generated Manifolds approach are employed). Subsequently, its computational cells are clustered to form ideal reactors by user-defined criteria, and the resulting Chemical Reactor Network (CRN) is subsequently solved with a detailed chemical reaction mechanism. The capabilities of the clustering and CRN solving computational tool (AGNES – Automatic Generation of Networks for Emission Simulation) are explored with a test case related to FC. The test case is non-premixed burner based on jet mixing and fueled with CH4 tested for various equivalence ratios. Results show that the prediction of CO emissions was improved significantly with respect to the CFD solution and are in good agreement with the experimental data. As for the NOx emissions, the CRN results were capable of reproducing the non-monotonic behavior with equivalence ratio, which the CFD simulations could not capture. However, the agreement between experimental values and and those predicted by CRN for NOx is not fully satisfactory. The clustering criteria employed to generate the CRNs from the CFD solutions were shown to affect the results to a great extent, pointing to future opportunities in improving the multi-step procedure and its application.
Keywords: Chemical reactor network (CRN), Flamelet generated manifolds, Flameless combustion, MILD combustion, NOx emission
Received: 30 Apr 2019;
Accepted: 04 Nov 2019.
Copyright: © 2019 A. V. Perpignan, Sampat and Gangoli Rao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Mr. André A. V. Perpignan, Delft University of Technology, Delft, Netherlands, A.A.V.Perpignan@tudelft.nl
Dr. Arvind Gangoli Rao, Delft University of Technology, Delft, Netherlands, A.GangoliRao@tudelft.nl