Gas Turbine Fuel Nozzle Tip Impingement Cooling
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Solution Overview
Problem
Fuel nozzles in turbomachines experience thermal stresses due to proximity to high-temperature combustion gases, leading to cracking or damage, necessitating an improved design to reduce or prevent such damage.
Innovation Solution
A fuel nozzle design featuring a nozzle tip with a solid aft wall and an impingement wall that directs fluid to impinge upon the aft wall, creating a plenum with outlets for post-impingement fluid, which enhances cooling and reduces thermal stress through convective cooling and impingement cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fuel nozzle is disposed in close proximity to high temperature combustion gases for effective fuel mixing and combustion, then the combustion efficiency is improved, but the nozzle experiences thermal stresses that cause cracking or damage
Solution Approach 1:
An impingement cooling system is introduced as an intermediary mechanism between the hot combustion gases and the fuel nozzle. Coolant fluid is delivered through coolant passages and discharged through impingement holes to directly impinge upon the nozzle surface, creating a protective cooling layer that mediates the thermal interaction between combustion gases and the nozzle structure
Solution Approach 2:
The patent utilizes fluid dynamics principles by introducing a coolant fluid through a network of coolant passages and discharge holes. The pressurized coolant fluid flows through the impingement cooling system, utilizing pneumatic and hydraulic mechanisms to deliver cooling effectiveness to the nozzle surface exposed to high-temperature combustion gases
2Reliability
If conventional cooling methods are used, then some thermal protection is provided, but the thermal stresses are insufficiently reduced and cracking or damage still occurs
Solution Approach 1:
The impingement cooling system applies cooling locally at the specific regions of the fuel nozzle that experience the highest thermal stresses. Coolant passages are strategically positioned and impingement holes are disposed at locations where thermal protection is most critical, providing concentrated cooling effectiveness precisely where needed rather than uniform cooling throughout the entire nozzle structure
Solution Approach 2:
The cooling fluid is delivered through coolant passages before the hot combustion gases can cause excessive thermal stress. The impingement cooling system is activated in advance to establish a protective thermal barrier on the nozzle surface, preventing the harmful thermal effects from occurring in the first place rather than attempting to remediate damage after it occurs
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 design significantly reduces thermal stress on the nozzle tip, preventing cracking and increasing hardware life by promoting efficient heat transfer and convective cooling, thereby enhancing durability.
Implementation Method 1
an impingement wall... defining a plurality of apertures configured to direct fluid to impinge upon the solid aft wall
Implementation Method 2
enhances cooling and reduces thermal stress through convective cooling and impingement cooling
Data Source
AI summary
A fuel nozzle includes a center body that extends from an upstream end to a downstream end. A nozzle tip, which is fixedly coupled to the downstream end of the center body, includes an outer annular wall that has a forward end and an aft end. A solid aft wall is disposed at the aft end of the outer annular wall. The solid aft wall and the outer annular wall at least partially define a plenum. A nozzle portion, which is disposed within the plenum, includes an inner annular wall and an impingement wall. The impingement wall is spaced apart from the solid aft wall and defines a plurality of apertures configured to direct fluid to impinge upon the solid aft wall. A plurality of outlets is defined in the outer annular wall forward of the solid aft wall to direct post-impingement fluid from the nozzle tip.