Reversing Duct for Fluid Flow Machine Stability
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Solution Overview
Problem
Fluid flow machines, such as blowers, compressors, and pumps, face limitations in aerodynamic loadability and efficiency due to boundary layer growth and separation at the rotor and stator blade tip areas, leading to operational instability and inefficiency, particularly with existing casing treatments that consume space and compromise performance.
Innovation Solution
The implementation of a compact, aerodynamically designed reversing duct system within the annulus duct of fluid flow machines, which reroutes fluid upstream and back into the main flow path at a shallow angle, effectively managing the boundary layer and enhancing stability while minimizing space and energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional casing treatments (circumferential grooves, slots, or reversing ducts) are used to improve stability by managing boundary layers, then stability is improved, but efficiency is reduced due to space consumption and aerodynamic losses
Solution Approach 1:
The reversing duct is designed with a three-dimensional centerline that extends in multiple spatial dimensions, allowing the duct to route fluid upstream while maintaining a compact footprint. The centerline projection to the meridional plane forms specific angles with the main flow path, utilizing spatial arrangement to achieve both stability improvement and space efficiency.
Solution Approach 2:
The invention optimizes specific geometric parameters of the reversing duct, including the angle α (between 135° and 225°) that the centerline projection forms with the main flow path confinement, and the ratio h/b (less than 0.6) to control the duct's spatial compactness. These parameter changes enable effective boundary layer management while minimizing space consumption and aerodynamic losses.
2Ease of manufacture
If conventional casing treatments with simple shapes (e.g., parallelogrammic grooves) are used, then manufacturing is easier, but efficiency is limited and they are restricted to rotor blade row areas only
Solution Approach 1:
The reversing duct employs a dynamic centerline design where the projection to the meridional plane forms variable angles along its length. The angle α changes from 135° to 225° over at least 60% of the running length, allowing the duct to adapt to different flow conditions and positions, enabling application in both rotor and stator blade row areas while maintaining manufacturing feasibility.
3Stability of the object's composition
If reversing ducts are designed with extended spatial arrangement to effectively route fluid upstream, then boundary layer management is improved, but the machine occupies more peripheral space
Solution Approach 1:
The reversing duct is nested within the existing annulus duct structure, with its centerline strategically positioned to utilize available space efficiently. The duct's compact design allows it to be integrated into the machine's peripheral area without significant space penalty, while still achieving effective boundary layer control through its upstream routing capability.
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 significantly improves the stability and efficiency of fluid flow machines by effectively managing the boundary layer in the blade tip area, reducing operational instability and energy consumption, and allowing for a more compact design.
Implementation Method 1
fluid is tapped from the rim of the main flow path via an opening, oriented near the main flow path essentially in parallel with the main flow path confinement, routed upstream, opposite to the main flow direction, and, finally, rerouted by flow reversal into the main flow path
Data Source
AI summary
A fluid flow machine has a main flow path 2 which is confined by a hub 3 and a casing 1 and in which at least one row of blades 5 is arranged. A gap 11 is provided on at least one blade row 5 between a blade end and a main flow path confinement, with the blade end and the main flow path confinement performing a rotary movement relative to each other. At least one reversing duct 7 is provided in the area of the blade leading edge in the main flow path confinement at a discrete circumferential position. The reversing duct 7 connects two openings 12, 13 arranged on the main flow path confinement.