Dome Diffuser Screen Varying Hole Spacing for Gas Turbine
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Solution Overview
Problem
Diffuser screens in gas turbine engines are prone to rupture due to high stress concentration factors at the periphery, which can lead to engine damage and operational issues during changes in rotational speed.
Innovation Solution
The design of the bleed assembly features a dome-shaped diffuser screen with increasing average nearest-neighbour spacing of through-holes towards the periphery, reducing stress concentration factors and peak stress levels, thereby minimizing the likelihood of screen rupture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the through-holes are uniformly spaced across the diffuser screen, then the manufacturing is simplified and the pattern is regular, but the stress concentration factors at the periphery remain high leading to screen rupture
Solution Approach 1:
The patent applies local quality by varying the spacing of through-holes based on their radial position. The average nearest-neighbour spacing increases with increasing radial distance from the centre, creating non-uniform local properties that reduce stress concentration at the periphery while maintaining structural integrity. This localized variation in hole spacing addresses the specific stress distribution pattern in the domed plate structure.
2Object-generated harmful factors
If the through-holes are closely spaced to improve mixing and noise attenuation, then the acoustic performance and mixing efficiency are enhanced, but the stress concentration increases and rupture risk rises
Solution Approach 1:
The patent implements local quality by differentiating the through-hole spacing based on radial position. In the central region, holes can be more closely spaced to achieve effective mixing and noise attenuation. Towards the periphery, the increased spacing reduces stress concentration factors, thereby preventing rupture while still maintaining adequate acoustic and thermal performance.
Solution Approach 2:
The patent applies parameter changes by modifying the spacing parameter of through-holes as a function of radial distance. The average nearest-neighbour spacing is not held constant but varies continuously or in steps with radial position, allowing optimization of both acoustic performance and structural reliability across different regions of the diffuser screen.
3Productivity
If the diffuser screen operates at high pressure ratios during compressor operations, then the engine performance is maintained, but the stress on the screen increases to critical levels during speed changes
Solution Approach 1:
The patent addresses the stress issue by implementing local quality in the through-hole pattern. The increased spacing at the periphery specifically targets the regions experiencing highest stress during pressure ratio changes and speed transitions, while the central region maintains adequate hole density for performance. This localized differentiation allows the screen to withstand critical stress conditions.
Data Source
AI summary
A bleed assembly for a gas turbine engine is provided. The assembly includes: a duct having an inlet and an outlet; a bleed valve that controls the flow of bleed fluid into the inlet; and a dome-shaped diffuser screen which covers the outlet. The diffuser screen has a plurality of through-holes for passage of the bleed fluid. Each through-hole has one or more nearest-neighbour through-holes at a nearest-neighbour spacing. At the periphery of the diffuser screen, the average nearest-neighbour spacing of the through-holes at a given radial distance from the centre of the diffuser screen increases with increasing radial distance.