Abstract
A numerical model is presented for the precise prediction of carbon monoxide (CO) emissions in gas turbine combustors. All models are based on Computational Fluid Dynamics (CFD). This work starts with an introduction of fundamental mechanisms, which are responsible for CO emissions. As we will show, there is a need of CO-models as standard combustion models fail to predict CO-emissions precisely. For the purpose of validation, experiments are conducted. High ratios of secondary air is bypassing the burner in order to induce interaction of the flame front with secondary air, as the flame brush gets diluted and decreases in reactivity. Note, this is an important mechanism for elevated CO emissions in multi-burner systems with high staging ratio. Five operating points with each having a different adiabatic flame temperature were measured. They include equilibrium (complete burnout) and superequilibrium CO (incomplete burnout). In summary, it is shown that the prediction of CO with the presented models lead to a significant improvement as it captures the transition from equilibrium to superequilibrium CO. Furthermore, the strong underestimation of CO predicted by standard combustion models is shown.
Highlights
Extending the operational window is one of the main challenges in gas turbine development as operational flexibility is a key attribute to meet the requirements of tomorrow
Load decrease is limited by a sharp rise in carbon monoxide (CO)-emissions caused by critically low flame temperature
The objective of this work is a Computational Fluid Dynamics (CFD)-based model, which is able to predict CO in combustion systems operating at part-load conditions
Summary
Extending the operational window is one of the main challenges in gas turbine development as operational flexibility is a key attribute to meet the requirements of tomorrow. This work is using two different approaches to (1) model the combustion by modifying the reaction progress source term closure of FGM (φ~ 1⁄4 ~c) and (2) modeling CO (φ~ 1⁄4 Y~ CO) Both models are introduced in the following two sections. In the context of FGM, the transport equation for the reaction progress ~c is closed by the PDF-integrated source term obtained from one-dimensional flamelet calculations: ðð ω_ 0c 1⁄4 ω_ 0c (c, f )P(c)P(f ) dc df (2). As already discussed, they clearly overestimate burnout rates of CO. DaCO,crit should be chosen around unity as this marks the transition point when chemical timescales start exceeding turbulent timescales
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of the Global Power and Propulsion Society
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
