Axial Compressor End-Wall Sinusoidal Profiling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Axial flow compressor blading experiences significant aerodynamic losses due to corner separation and secondary flows, which reduce mass flow and efficiency, and existing methods like three-dimensional leaning have mechanical and manufacturing limitations, as well as inefficiencies at high aerodynamic loading.
Innovation Solution
The use of sinusoidally shaped end walls with perturbations at specific axial positions, matching the pitch of the aerofoils, and smooth transitions between these perturbations to control the boundary layer and reduce corner separation, achieved through spline curves and amplitude adjustments, effectively managing the static pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If three-dimensional leaning of aerofoils is applied to control corner separation, then aerodynamic efficiency and surge margin are improved, but mechanical stress and manufacturing complexity increase
Solution Approach 1:
The invention transitions from three-dimensional aerofoil leaning (which requires complex structural modifications) to two-dimensional end-wall profiling. By shaping the end wall surface in the radial direction with bumps and hollows, the patent achieves corner separation control without compromising aerofoil structural integrity, thus improving aerodynamic efficiency while avoiding increased mechanical stress on rotating blades
Solution Approach 2:
The end wall surface acts as an intermediary element that mediates between the boundary layer flow and the aerofoils. By modifying the end wall geometry with specific bump and hollow patterns, the invention indirectly controls corner separation and secondary flows without directly altering the aerofoil structure, thereby avoiding the mechanical stress issues associated with three-dimensional leaning
2Object-generated harmful factors
If three-dimensional leaning with sweep and dihedral is applied, then corner separation is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The invention applies local geometric modifications to the end wall surface through bumps and hollows with specific dimensions and positions tailored to control boundary layer behavior. This localized approach to flow control is simpler to manufacture than global three-dimensional aerofoil leaning, as it involves modifying the end wall surface rather than complex aerofoil geometries
Solution Approach 2:
By moving the flow control mechanism from the aerofoil (three-dimensional leaning) to the end wall (two-dimensional profiling), the invention simplifies manufacturing. The end wall can be shaped with bumps and hollows using conventional machining or forming processes, avoiding the complex tooling and assembly required for three-dimensional aerofoil construction
3Object-generated harmful factors
If axial lean components are added to adjacent blade rows, then corner separation is controlled, but machine length and weight increase
Solution Approach 1:
The invention extracts the axial lean function from the aerofoil geometry and relocates it to the end wall profiling. By taking out the flow control mechanism from the rotating blade rows and placing it on the stationary end wall, the patent eliminates the need for additional axial length to accommodate leaned adjacent rows, thus reducing overall machine length and weight
4Power
If high aerodynamic loading is applied to increase compressor performance, then pressure ratio increases, but corner separation and flow reversal worsen
Solution Approach 1:
The bumps and hollows on the end wall are positioned upstream of the corner region to preemptively control boundary layer development. By acting in advance on the boundary layer through pressure gradient modification, the invention prevents corner separation from occurring under high loading conditions, enabling higher compressor pressure ratios without the detrimental effects of separation and flow reversal
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 significantly reduces corner separation and flow reversal, enhancing aerodynamic efficiency and compressor performance without the drawbacks of existing methods, by optimizing the surface curvature and pressure distribution within the blade passage.
Implementation Method 1
Friction on the annular walls of the blade passages creates a boundary layer of slower moving air
Implementation Method 2
the pressure gradient between the lower and upper surfaces of adjacent blades
Implementation Method 3
All aerofoils, whether in compressors or in turbines, use surface curvature to change the static pressure of the flow and thus provide lift
Implementation Method 4
The flow over the convex curvature (of the humps) experiences relative acceleration and the static pressure falls locally
Implementation Method 5
the flow over the concave curvature (of the hollows) experiences relative diffusion and the static pressure rises locally
Implementation Method 6
The slow boundary layer airflow is over-turned (that is, turned further than the design angle) and rolls up into vortices
Implementation Method 7
a region of separated flow will form in the corner between the aerofoil suction surface and the end wall
Data Source
AI summary
An axial compressor has at least one circumferential row of aerofoil members (30a, 30b, 30c) in which at least one of the two end walls (37) between adjacent blades is given a non-axisymmetric profile, defined by circumferentially-extending sinusoids at a number of axial positions (AA, BB, CC). Corresponding points on the successive sinusoids are joined by spline curves, so that the curvature of the end wall is smooth. This end-wall profiling modifies the boundary layer flow at the wall, reducing or eliminating the corner separation and reversed flow associated with known arrangements.