Two-Stage Downstream Fuel Injection for Gas Turbine Combustor
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Solution Overview
Problem
Gas turbines face limitations in increasing operating efficiency due to stringent NOx emission regulations at higher temperatures, which hinder advances in engine efficiency and require novel combustor designs that reduce emissions while enabling higher firing temperatures.
Innovation Solution
A two-stage downstream injection system is implemented in the gas turbine combustor, with each stage axially spaced and circumferentially positioned to optimize air and fuel injection, reducing reactant residence time and NOx emissions while maintaining efficient combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher operating temperatures are used to improve engine efficiency, then engine efficiency is improved, but NOx emissions increase
Solution Approach 1:
The injection system is divided into multiple stages (primary injection and downstream injection) with distinct functions. The primary injection system provides initial fuel delivery, while the downstream injection stages (first and second stages) are positioned at different axial locations to sequentially introduce additional fuel and air, allowing temperature and emission control through staged combustion zones
Solution Approach 2:
The injection system extends beyond the traditional single-plane approach by positioning injectors at multiple axial locations along the combustor length. This axial dimensionality allows fuel and air to be introduced at different stages of the combustion process, enabling independent control of combustion zones to reduce residence time at high temperatures while maintaining overall combustion efficiency
2Power
If higher firing temperatures are implemented to increase pressure ratio cycle efficiency, then pressure ratio cycle efficiency is improved, but NOx emission levels increase
Solution Approach 1:
The downstream injection system is positioned and configured based on anticipated combustion flow characteristics upstream of the first stage. This preliminary positioning allows the system to pre-establish injection patterns that will achieve desired temperature distribution and minimize NOx formation before combustion products reach the turbine
Solution Approach 2:
The circumferential positioning of injectors in both stages is determined based on anticipated combustion flow characteristics and the expected effects of injection on downstream flow. This feedback-based positioning optimizes mixing and combustion to reduce residence time at high temperatures, thereby lowering NOx emissions while maintaining efficient combustion
3Object-generated harmful factors
If downstream injection stages are added to reduce NOx emissions, then NOx emissions are reduced, but device complexity increases
Solution Approach 1:
Multiple injection stages are merged into a coordinated system where primary injection and downstream injection (with first and second stages) work together as an integrated combustion control system. The stages are axially spaced and circumferentially positioned to complement each other, achieving emission reduction through combined action rather than requiring separate independent systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The two-stage injection system effectively reduces NOx emissions, allows for higher combustor firing temperatures, and improves engine efficiency by minimizing reactant residence time within the combustion zone, while also optimizing CO and UHC burnout.
Implementation Method 1
a combustor coupled to a turbine that together define an interior flowpath, the interior flowpath extending rearward about a longitudinal axis from a primary air and fuel injection system
Implementation Method 2
each injector of which is configured to inject air and fuel into a combustion flow through the interior flowpath
Data Source
AI summary
A method for use in a gas turbine engine. The method includes the steps of: configuring a downstream injection system within the interior flowpath that includes two injection stages, a first stage and a second stage, wherein the first stage and the second stage are each axially spaced from the other; and circumferentially positioning the injectors of the first stage and the second stage based on: a) a characteristic of an anticipated combustion flow occurring just upstream of the first stage during a mode of operation; and b) the characteristic of an anticipated combustion flow just downstream of the second stage given an anticipated effect of the air and fuel injection from the first stage and the second stage.