Turbine Pre-mixing Apparatus with Segmented Zones for NOx Control
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Solution Overview
Problem
Gas turbine engines face challenges in achieving efficient combustion while minimizing nitrogen oxide (NOx) emissions, as higher temperatures increase efficiency but also NOx production, and existing mixing techniques like lean pre-mixed and direct injection combustors can lead to auto-ignition, flashback, and high NOx levels, with inert diluents being costly and ineffective when unavailable.
Innovation Solution
A pre-mixing apparatus with a main body and fluid delivery plenum, featuring multiple fluid delivery tubes with strategically placed openings for mixing fuel and air before combustion, allowing for selective mixing stages and diluent introduction to control NOx levels, including angled and varying cross-section tubes to enhance mixing and reduce flame holding potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If fuel is pre-mixed with air in a pre-mixing apparatus, then NOx levels are reduced, but auto-ignition and flashback may occur within the pre-mixing apparatus
Solution Approach 1:
The pre-mixing apparatus is divided into multiple zones (pre-mixing zone, transition zone, and combustion zone) with distinct functions. The pre-mixing zone performs fuel-air mixing while the transition zone manages flame propagation, segmenting the harmful effects and preventing auto-ignition and flashback in the pre-mixing zone.
Solution Approach 2:
A transition zone is introduced as an intermediary between the pre-mixing zone and combustion zone. This transition zone acts as a buffer that controls flame propagation and prevents flashback into the pre-mixing apparatus, while also preventing auto-ignition of the pre-mixed fuel-air mixture.
2Reliability
If fuel and air are introduced separately into a combustion liner (LDI concepts), then pre-mixing risks are avoided, but rapid and uniform mixing is difficult to achieve
Solution Approach 1:
Fuel and air are pre-mixed in the pre-mixing zone before being introduced into the combustion liner. This preliminary mixing action ensures rapid and uniform mixing is achieved before combustion, avoiding the mixing problems of LDI concepts while maintaining the benefits of controlled combustion.
Solution Approach 2:
Different regions of the combustion liner are designed with different mixing characteristics. The pre-mixing zone provides intensive mixing, while the combustion zone provides controlled combustion conditions. This local differentiation of mixing quality achieves both rapid mixing and reliable combustion.
3Object-generated harmful factors
If inert diluents are added to reduce NOx levels, then NOx production is reduced, but engine heat rate is adversely affected and costs increase
Solution Approach 1:
The invention changes the temperature parameter distribution within the combustion system by creating a controlled low-temperature zone in the transition area. This temperature parameter change reduces NOx formation through thermal mechanisms without requiring inert diluents, thereby maintaining engine heat rate and efficiency.
Solution Approach 2:
The invention converts the potentially harmful pre-mixed fuel-air mixture into a benefit by using it to create a controlled low-temperature combustion environment. This converts what could be a safety hazard (auto-ignition risk) into a useful mechanism for reducing NOx emissions without diluents.
4Temperature
If diluents are introduced downstream of the reaction zone, then gas stream temperature is controlled, but NOx levels are not significantly improved
Solution Approach 1:
The invention performs the temperature control and NOx reduction action in advance, within the transition zone before the main combustion products enter the turbine. This preliminary temperature management prevents NOx formation at its source rather than attempting to control it downstream, achieving both temperature control and NOx reduction simultaneously.
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 apparatus effectively controls NOx emissions by ensuring uniform fuel-air mixing, reducing auto-ignition and flashback risks, and allowing for adaptable fuel-air ratios, maintaining efficiency while meeting regulatory NOx limits without relying on inert diluents, thus optimizing engine performance and reducing operational costs.
Implementation Method 1
multiple fluid delivery tubes with strategically placed openings for mixing fuel and air before combustion
Implementation Method 2
ensuring uniform fuel-air mixing
Implementation Method 3
combust a fuel/air mixture which releases heat energy to form a high temperature gas stream
Implementation Method 4
reduces combustion temperatures and, as a consequence, also reduces NOx output
Data Source
AI summary
A pre-mixing apparatus for a turbine engine includes a main body having an inlet portion, an outlet portion and an exterior wall that collectively establish at least one fluid delivery plenum, and a plurality of fluid delivery tubes extending through at least a portion of the at least one fluid delivery plenum. Each of the plurality of fluid delivery tubes includes at least one fluid delivery opening fluidly connected to the at least one fluid delivery plenum. With this arrangement, a first fluid is selectively delivered to the at least one fluid delivery plenum, passed through the at least one fluid delivery opening and mixed with a second fluid flowing through the plurality of fluid delivery tubes prior to being combusted in a combustion chamber of a turbine engine.