Canonical Validation of a Modeling Strategy for Carbon Monoxide Emissions in Staged Operation of Gas Turbine Combustors

Noah Klarmann,Thomas Sattelmayer

doi:10.33737/jgpps/127716

Abstract

Canonical validation of a holistic modeling strategy for the prediction of CO emissions in staged operation of gas turbine combustors is subject of this study. Results from various validation cases are presented. Focus is on operating conditions that can be considered typical for modern, flexible gas turbines that meet the requirements of the upcoming new energy age. Reducing load in gas turbines is usually achieved by redistributing fuel referred to as fuel staging. Fuel-staged operation may lead to various mechanism like strong interaction of the flame with secondary air leading to quenching and elevated CO emissions and is - due to technical relevance - stressed in this work. In the recent past, our group published a new modeling strategy for the precise prediction of heat release distributions as well as CO emissions. An extension to the CO modeling strategy that is of high relevance for the introduced validation cases is addressed by this work. The first part of this study presents relevant aspects of the overall modelling strategy. Furthermore, a validation of the models is shown to demonstrate the ability of precisely predicting CO in two different multi-burner cases. Both validation cases feature a silo combustion chamber with 37 burners. The burner groups are switched off at partial load leading to intense interactions between hot and cold burners. Major improvement in comparison to CO predictions from the flamelet-based combustion model can be achieved as the modeling strategy is demonstrated to be capable of predicting global CO emissions accurately. Furthermore, the model’s precision in fuel staging scenarios are demonstrated and discussed.

Highlights

Conventional power sources are anticipated to lose relevance due to a significant increase of renewables but will retain its major role in the overall energy mix
The proposed CO-modeling approach is introduced. It is based on the combustion model that was published by the authors in Klarmann, Sattelmayer, Geng et al (2016) and Klarmann, Sattelmayer, Zoller et al (2016)
CO is described by the combustion model only up to a certain point, which is denoted as the decoupling event

Summary

Introduction

Conventional power sources are anticipated to lose relevance due to a significant increase of renewables but will retain its major role in the overall energy mix. In order to prepare gas turbines for the challenges of tomorrow, reduction of emissions, increase of flexibility, efficiency, and reliability is of high technical relevance To fulfil their new role, modern gas turbines need to be able to perform fast load changes in a large operating window. It is important to note that a combustion model that is based on the flamelet assumption can only predict elevated CO emissions if the turbulent flame brush thickness is in the magnitude order of the combustion chamber or if the flamelets fluctutate to the outlet. The CO model was firstly introduced and validated in an atmospheric single-burner test rig in Klarmann et al (2018) In the following, this modeling strategy is extended to consider quenching effects that are demonstrated to play an important role in predicting CO emissions. Validation is performed using two multi-burner cases that differ in terms of pressure and the way fuel is staged in part load operation

Methodology

Findings

Summary and discussion