Conical-Flat Heat Shield Combustion Instability
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Solution Overview
Problem
Gas turbine engine combustors face challenges with high levels of noise and acoustic pressure oscillations due to combustion instability, particularly in low NOx emissions designs, which can lead to mechanical and thermal fatigue and hardware damage.
Innovation Solution
The implementation of conical-flat heat shields with an annular conical section and a flat section, featuring film cooling and a cylindrical transition section, mounted on the combustor dome to stabilize flames and reduce acoustic pressures through efficient airflow and heat management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If water or steam injection is used to achieve low emissions, then NOx emissions are reduced, but combustion instability and dynamic pressure oscillations increase
Solution Approach 1:
The patent changes the geometric parameters of the heat shield by introducing a conical section with a specific half-angle (5-15 degrees) and a flat section with specific dimensions. This geometric modification alters the flow patterns and flame stabilization characteristics, enabling the system to maintain low emissions while reducing combustion instability and pressure oscillations.
Solution Approach 2:
The patent applies a conical curved surface instead of a flat or cylindrical heat shield geometry. The conical section with its specific half-angle creates a curved flow path that stabilizes the flame and reduces vortex formation, thereby decreasing dynamic pressure oscillations while maintaining emission control benefits.
2Object-generated harmful factors
If lean premixed combustion is used to reduce NOx emissions, then flame temperatures are limited, but combustion acoustics and pressure pulses increase
Solution Approach 1:
The conical-flat heat shield structure is designed to preliminarily stabilize the flame before it enters the main combustion zone. The conical section creates a flame holder effect that anchors the flame, preventing subsequent vortex formation and pressure oscillations in the lean premixed combustion zone.
Solution Approach 2:
The heat shield acts as an intermediary element between the fuel injection system and the main combustion zone. It modifies the flow patterns and flame characteristics, serving as a buffer that reduces the transmission of acoustic waves and pressure pulses through the combustion chamber.
3Ease of manufacture
If conventional cylindrical heat shields are used, then manufacturing is simple, but they fail to effectively stabilize flames and reduce acoustic pressures
Solution Approach 1:
The heat shield is segmented into two distinct functional sections: a conical section for flame stabilization and a flat section for structural support and cooling. This segmentation allows each portion to be optimized for its specific function while maintaining manufacturability through standard machining operations.
Solution Approach 2:
The patent transitions from a symmetric cylindrical geometry to an asymmetric conical-flat geometry. The conical section with its specific half-angle provides superior flame stabilization capabilities compared to a cylindrical shape, while the flat section maintains ease of manufacture. This asymmetric design achieves better performance without significantly complicating the manufacturing process.
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 conical-flat heat shields effectively reduce combustion instability, acoustic pressures, and emissions of NOx, CO, and HC, enhancing the durability and operability of gas turbine engines by stabilizing flames and minimizing heat release-induced vortices.
Implementation Method 1
The conical-flat heat shields effectively reduce combustion instability, acoustic pressures, and emissions of NOx, CO, and HC, enhancing the durability and operability of gas turbine engines by stabilizing flames and minimizing heat release-induced vortices.
Implementation Method 2
The conical-flat heat shield may include film cooling means for cooling a downstream facing surface of the conical-flat heat shield upstream or forward of the flat section.
Implementation Method 3
The conical-flat heat shields effectively reduce combustion instability, acoustic pressures, and emissions of NOx, CO, and HC
Data Source
AI summary
A gas turbine engine combustor conical-flat heat shield includes an annular conical section extending upstream from and being integral with a flat section with a flat downstream facing surface which may be generally perpendicular to or canted with respect to a centerline. The flat section includes radially outer and inner edges at least one of which is circular and circumscribed about a centerline and circumferentially spaced apart clockwise and counter-clockwise radial edges having an origin on the centerline. A gas turbine engine combustor includes conical-flat heat shields in one or more circular rows arranged in a non-symmetrical or asymmetrical pattern. Two or more groups (A, B, C) of the conical-flat heat shields in the circular rows may be mounted on a domeplate and one or more of the conical-flat heat shields is different in one or more of the groups (A, B, C).