Gas Turbine Nacelle Short Intake Diffuser Angle Optimization
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Solution Overview
Problem
Current gas turbine engines with low specific thrust require larger nacelles, increasing drag and mass, which in turn increase fuel consumption, and existing design methodologies are not suitable for short intakes, posing challenges in reducing nacelle length while maintaining aerodynamic performance.
Innovation Solution
A nacelle design with a short air intake featuring a diffuser angle between 0.1 and 12 degrees, a contraction ratio of 1.15 to 1.28, and an aspect ratio of 2 to 3, optimized for aerodynamic performance, including a highlight and throat structure with specific radii and lengths, to accommodate a fan while minimizing drag and mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the specific thrust is reduced to improve fuel consumption, then the bypass ratio increases, but the fan diameter and nacelle dimensions increase proportionally, resulting in increased drag and mass
Solution Approach 1:
The patent applies parameter changes by optimizing the diffuser angle (reducing it to minimize flow separation and drag) and adjusting the intake length and throat area ratios. These parameter modifications allow the nacelle to accommodate a larger fan diameter while minimizing the increase in drag and mass, thus resolving the contradiction between improved fuel consumption and increased nacelle weight
2Weight of moving object
If the nacelle length is reduced to minimize drag and mass, then the intake length becomes short, but conventional design methodologies are not applicable to short intakes
Solution Approach 1:
The patent establishes new design parameters specifically for short intakes, including a diffuser angle range of 5-15 degrees (lower than conventional designs), an intake length to highlight radius ratio of 0.6-0.8, and a throat area ratio. These parameter changes enable the design of short intakes that maintain aerodynamic performance without requiring conventional long-nacelle methodologies, thus reducing design complexity for short intake configurations
3Speed
If the nacelle dimensions are increased to accommodate a larger fan, then the fan diameter increases, but the nacelle drag and mass increase proportionally
Solution Approach 1:
The patent optimizes several parameters simultaneously: reducing the diffuser angle to minimize flow separation and drag, optimizing the intake length to highlight radius ratio, and adjusting the throat area ratio. These parameter changes enable the nacelle to accommodate a larger fan diameter while minimizing the proportional increase in drag, thus resolving the contradiction between increased fan size and increased nacelle drag
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 optimized design parameters result in a short intake nacelle with improved aerodynamic performance, suitable for underwing-podded aircraft engines, reducing fuel consumption and drag while maintaining optimal thrust efficiency.
Implementation Method 1
The diffuser includes a diffuser angle (θdiff) indicating a degree of divergence of the diffuser relative to the longitudinal centre line. The diffuser angle (θdiff) ranges from about 0.1 degrees to about 12 degrees.
Implementation Method 2
The throat includes a throat radius (Rth). Further, a contraction ratio (CR) is disclosed as the square of a ratio (Rhi/Rth)2 between the highlight radius (Rhi) and the throat radius (Rth). The contraction ratio (CR) ranges from about 1.15 to about 1.28.
Data Source
AI summary
A nacelle for a gas turbine engine having a longitudinal centre line. The nacelle includes an air intake disposed at an upstream end of the nacelle. The air intake includes, in flow series, an intake lip, a throat and a diffuser. The diffuser further includes a diffuser angle (θdiff), indicating a degree of divergence of the diffuser relative to the longitudinal centre line. The diffuser angle (θdiff) is from about 0 degrees to about 12 degrees.