Annular Passage Geometry for Compressor Stall Prevention
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Solution Overview
Problem
In turbomachines, the heating of air due to viscoelastic properties within the compressor rotor leads to cooling air reinjection, causing disturbances and potential stall phenomena, especially at blade corners, which existing geometries fail to adequately address, resulting in performance setbacks.
Innovation Solution
An annular passage geometry with a specific profile of revolution, featuring a junction arc connecting upstream and downstream segments, where the median axis forms an angle between 15° and 45° with the axis of rotation, and leading edges positioned upstream of the junction arc, reduces the impact of cooling air reinjection by facilitating a more progressive flow modification and minimizing separation at blade corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling air is radially reinjected into the primary stream to counteract heating, then the heating effect is reduced, but disturbances are generated that can generate stall phenomena
Solution Approach 1:
The patent converts the harmful parasitic flow that bypasses the sealing device into a beneficial cooling effect. By designing the annular passage to guide this previously harmful flow radially outward toward the blade leading edges, the patent transforms it into useful cooling air that prevents overheating without requiring additional cooling systems.
Solution Approach 2:
The patent changes the geometric parameters of the annular passage, specifically setting the angle between the median axis and the rotation axis between 15° and 45°. This parameter optimization ensures that the cooling flow is directed at the optimal angle to the blade leading edges, maximizing cooling effectiveness while minimizing flow disturbances that could cause stalls.
2Temperature
If the cooling air flow is increased to improve cooling effectiveness, then temperature control improves, but flow disturbances are amplified increasing stall risk
Solution Approach 1:
The patent optimizes geometric parameters including the passage angle (15°-45°), passage length, and the positioning of leading edges relative to the joining arc. These parameter changes ensure that cooling flow is delivered at optimal rates and angles, achieving effective temperature control while maintaining flow attachment and minimizing disturbances.
Solution Approach 2:
The patent replaces complex active flow control systems with a passive geometric solution. The annular passage geometry itself, with its specific angle and configuration, automatically directs the cooling flow in the optimal manner without requiring additional actuators, sensors, or control systems.
3Reliability
If the annular passage geometry is modified to reduce flow separation, then stability improves, but manufacturing complexity may increase
Solution Approach 1:
The patent employs curved surfaces in the annular passage design, particularly the joining arc that connects the upstream and downstream segments. This curvature ensures smooth flow transitions that prevent separation, while the revolution surface geometry can be efficiently manufactured using standard rotational forming processes.
Solution Approach 2:
The patent specifies particular parameter ranges (angle between 15°-45°, axial recession percentages) that balance performance and manufacturability. These optimized parameters achieve flow stability while remaining within standard manufacturing capabilities for turbomachinery components.
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 geometry optimizes turbomachine performance and stability by ensuring the primary flow adheres to the annular walls, reducing disturbances and preventing separation, thus enhancing operational efficiency and maintaining flow stability.
Implementation Method 1
The invention also aims to reduce stalling phenomena, particularly at blade corners... minimizing separation at blade corners
Implementation Method 2
During operation, the air enclosed in a turbomachine compressor rotor tends to heat up due to its viscoelastic properties
Data Source
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AI summary
The invention relates to a turbomachine assembly, in particular a low-pressure compressor for an aircraft turbojet engine. The assembly comprises an annular row of upstream blades (28) with trailing edges (42) extending radially from an upstream support (36); an annular row of downstream blades (30) with leading edges (40) axially aligned with the trailing edges (42) and extending radially from a downstream support (38); and an annular passage (48) delimited by the upstream support (36) and the downstream support (38). Externally, the downstream support (38) has a profile of revolution (71) with: an upstream segment (72) delimiting the annular passage (48) by forming an annular slide, a downstream segment (76) axially aligned with the downstream blades, and a connecting arc (74) linking the upstream segment. The joining arc (74) is placed downstream of the leading edges and the profile of the annular passage has a median axis forming an angle with the axis of rotation between 15° and 45°.An associated method for controlling the stability of a compressor is thus presented.