Rotor Assembly Scoops Reduce Tip Vortices
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Solution Overview
Problem
Engine fan flutter caused by shocks at blade tips and tip vortices in rotor assemblies, such as gas turbine engines, is undesirable and challenging to mitigate effectively.
Innovation Solution
The implementation of a rotor assembly with concentric inner and outer walls and a plurality of scoops or wear members that deflect and reorient the flow to reduce tip vortices, minimizing the annular gap between the blades and the outer wall, and using scoops that form closed channels to transform the flow into a more laminar orientation upstream of the blades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the annular gap between blades and outer wall is minimized, then tip vortices and flow losses are reduced, but manufacturing precision requirements increase
Solution Approach 1:
Scoops are introduced as intermediary flow control devices positioned between the outer wall and blades. These scoops actively manage the flow in the annular gap region, transforming it into a more laminar flow pattern that reduces tip vortices without requiring the gap to be minimized to extreme precision.
Solution Approach 2:
The flow characteristics in the annular gap are changed by introducing scoops that modify velocity distribution and flow regime. By changing the flow parameters (introducing laminarizing elements), the harmful tip vortex effect is reduced without changing the geometric parameter (gap dimension) to extreme values.
2Stability of the object's composition
If scoops are added to deflect flow, then flutter and vibration are reduced, but device complexity increases
Solution Approach 1:
The flow control function is segmented into multiple discrete scoop elements arranged in a circumferential array. Each scoop handles a portion of the flow, and the collective effect of these segmented elements achieves comprehensive flow management while keeping individual components simple and manufacturable.
Solution Approach 2:
The scoop structure is designed to be stationary and fixed to the housing, allowing it to passively deflect flow without requiring active control systems. The flow itself interacts with the scoops to create the laminarizing effect, making the system self-regulating and reducing control complexity.
3Productivity
If scoops extend radially closer to blades, then flow deflection effectiveness increases, but risk of interference with blade path increases
Solution Approach 1:
The scoops are positioned to perform flow deflection and laminarization in advance, before the flow reaches the blade region. This preliminary action transforms the flow characteristics upstream of the blades, allowing the scoops to be positioned closer to the blades without causing direct interference, as the harmful flow patterns are already corrected.
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 solution reduces tip vortices, blade vibration, and flutter by minimizing flow losses and adverse pressure effects, enhancing the efficiency and stability of the rotor assembly.
Implementation Method 1
separating an outer portion of a flow through the annular flow path from a central portion of the flow
Implementation Method 2
transform the flow into a more laminar orientation upstream of the blades
Implementation Method 3
tip vortices created in the flow adjacent the blade tips
Implementation Method 4
minimizing flow losses and adverse pressure effects
Data Source
AI summary
A rotor assembly having a plurality of scoops disposed in a circumferential array, the scoops extending from an inner surface of the outer wall of the flow path along a radial distance smaller than a radial distance between the inner and outer walls of the flow path. Each of the scoops forms a closed channel from an inlet to an outlet with the inlet and outlet being axially spaced from one another, the outlet being upstream of and adjacent the annular blade path. A gas turbine engine and method of reducing tip vortices in a rotor assembly are also discussed.