Turbofan Stator Vane Ridges Control Boundary Layer

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Solution Overview

Problem

Modern axial-flow compressors face limitations in further performance improvements, leading to asymptotic trends in efficiency and specific fuel consumption, necessitating innovative methods to minimize aerodynamic losses and expand the incidence range.

Innovation Solution

The implementation of an airfoil-shaped entrance stator with channels and ridges in turbofan engines, where high-pressure air is injected into the boundary layer to trip the flow from laminar to turbulent, reducing boundary layer separation and enhancing compressor efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional airfoil design is used in axial-flow compressors, then the design is simple and well-understood, but performance improvements have become asymptotic and further efficiency gains are difficult to achieve

Engineering Contradiction:

Improvecompressor efficiencyVSAvoidairfoil design complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by modifying the boundary layer characteristics through controlled trips (protrusions) on the airfoil surface. These trips change the flow regime from laminar to turbulent in specific regions, altering the boundary layer parameters to reduce separation losses and improve compressor efficiency beyond the asymptotic limits of conventional smooth airfoil designs.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements local quality by placing boundary layer trips at specific locations on the airfoil surface where flow separation is most likely to occur. The trips are strategically positioned on the suction surface and/or pressure surface to locally modify boundary layer behavior without requiring complete redesign of the entire airfoil geometry.

Inventive Principle:

Principle #3Local quality

2Loss of energy

If boundary layer control methods are implemented to reduce separation losses, then compressor efficiency improves, but the device complexity increases due to additional components like channels and ridges

Engineering Contradiction:

Improveaerodynamic lossesVSAvoidstator vane structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent extracts the boundary layer control function by incorporating dedicated trips (protrusions) and associated channels directly into the stator vane structure. These extracted elements are specifically designed to trip the boundary layer and prevent separation, isolating the control function from the main airfoil geometry while reducing overall aerodynamic losses.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the stator vane surface into distinct functional zones: regions with boundary layer trips, associated channels for flow management, and the main airfoil surfaces. This segmentation allows each component to be optimized for its specific function while working together to reduce separation losses and improve efficiency.

Inventive Principle:

Principle #1Segmentation

3Productivity

If vane loading is increased to improve compressor performance, then efficiency increases, but the operating range becomes more limited and stability decreases

Engineering Contradiction:

Improvecompressor performanceVSAvoidoperating range

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent applies dynamics by making the boundary layer control system adaptable to different operating conditions. The trips and channels are designed to dynamically respond to varying flow conditions, allowing the compressor to maintain optimal performance across a broader operating range while accommodating different vane loading requirements without sacrificing stability.

Inventive Principle:

Principle #15Dynamics

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

This approach increases vane loading, expands the compressor's operating range, reduces solidity, wetted area, and total weight, while minimizing losses and bleed mass flow rates, thereby improving overall system efficiency.

Implementation Method 1

high-pressure air is injected into the boundary layer to trip the flow from laminar to turbulent

Methodology Applied

Scientific EffectBoundary layer transition from laminar to turbulent flow: Boundary Layer

Implementation Method 2

trip the flow from laminar to turbulent

Methodology Applied

Scientific EffectTurbulence: Turbulence

Implementation Method 3

a channel with an opening on the pressure side, the channel extending from the opening to an exit on the suction side, with a pressure gradient between the opening and the exit

Methodology Applied

Scientific EffectPressure gradient driven flow: Pressure Gradient

Data Source

PatentUS10519976B2Fluid diodes with ridges to control boundary layer in axial compressor stator vane

Publication Date: 2019.12.31 ROLLS ROYCE CORP

AI summary

An entrance stator in a turbofan has an airfoil shape with a leading edge and a trailing edge connected by surfaces which define a suction side and a pressure side. The entrance stator has a channel with an opening on the pressure side, extending to an exit on the suction side, having a pressure gradient between the opening and the exit. The channels are preceded with a ridge. The channels and the ridges control the boundary layer, enabling higher efficiencies. The channels and ridges add energy to the boundary layer to prevent separation.