Impingement Cooled Nozzle Tip for Gas Turbine Fuel Nozzles
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Solution Overview
Problem
Current fuel nozzle designs for gas turbines experience coking and high thermal stresses at the center body tip due to liquid fuel operation, leading to reduced durability and life expectancy, despite cooling mechanisms like air curtains.
Innovation Solution
A center body tip assembly with a radially extending impingement plate and cap that defines a cooling plenum, featuring angled cooling ports to enhance fluid communication and swirl the cooling air, reducing thermal stresses and coke formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid fuel cartridge is positioned close to the combustion zone for effective flame generation, then flame stabilization is improved, but thermal stresses and coking on the center body tip increase
Solution Approach 1:
A liquid fuel tip shield is introduced as an intermediary component between the liquid fuel cartridge and the combustion zone. The shield protects the center body tip from direct exposure to high temperatures and coking conditions while maintaining the liquid fuel cartridge's proximity to the combustion zone for effective flame stabilization. The shield acts as a protective barrier that separates the harmful thermal environment from the vulnerable center body tip.
Solution Approach 2:
The design modifies the thermal parameters at the center body tip by introducing cooling air flow through the tip shield. This changes the temperature distribution and thermal stress conditions, allowing the liquid fuel cartridge to remain close to the combustion zone without causing excessive thermal damage to the center body tip.
2Temperature
If cooling air is routed through the center body to cool the tip, then thermal stress is reduced, but cooling effectiveness is insufficient for high temperature operation
Solution Approach 1:
The cooling air flow path is extended into a third dimension by routing air through passages in the center body and then through the tip shield structure. This multi-dimensional cooling approach increases the surface area and duration of cooling contact, significantly enhancing cooling effectiveness compared to simple radial cooling paths.
Solution Approach 2:
The tip shield cooling system provides continuous cooling air flow through the center body and tip shield passages, maintaining constant thermal protection during operation. The cooling action is sustained throughout the high-temperature operation period, preventing thermal stress accumulation and coking formation.
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 solution effectively increases the cooling capacity and reduces thermal stresses on the tip assembly, enhancing the mechanical performance and durability of the fuel nozzle by optimizing flame stabilization and preventing coke deposits.
Implementation Method 1
The plurality of cooling ports extends through the impingement plate to provide for fluid communication between the cooling air flow passage and the cooling plenum
Implementation Method 2
heat from the combustion gases and/or heat due to heating during premix mode operation may damage the center body tip
Implementation Method 3
A plurality of cooling ports extends through the impingement plate to provide for fluid communication between the cooling air flow passage and the cooling plenum
Data Source
AI summary
A fuel nozzle for a combustor includes a burner tube and a center nozzle assembly disposed within the burner tube. The center nozzle assembly includes a center body that at least partially defines a cooling air flow passage through the center nozzle assembly. A premix flow passage is defined between the burner tube and the center nozzle assembly. A tip assembly is disposed at a downstream end of the center body. The tip assembly includes an impingement plate, and a cap that is disposed downstream from the impingement plate. The impingement plate and the cap at least partially define a cooling plenum therebetween. An insert passage extends through the impingement plate and a cooling flow outlet extends through the cap. A plurality of cooling ports extends through the impingement plate to provide for fluid communication between the cooling air flow passage and the cooling plenum.