Blade-Platform Assembly Supersonic Flow Pressure Gradient
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Solution Overview
Problem
The modification of platform surfaces in turbine engine blade wheels to improve aerodynamic efficiency through circumferential depressions or bulges can lead to undesirable effects such as high pressure gradients and uneven fluid speed distributions, which are difficult to rectify without compromising efficiency.
Innovation Solution
The blade shape is modified by creating a raised skeleton curve above the linearized skeleton curve in the vicinity of the platform, which adapts to the flow changes induced by the circumferential depression, limiting fluid acceleration and restoring initial flow gradients, thereby maintaining aerodynamic efficiency and homogeneous speed distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the platform surface is modified with circumferential depression to improve aerodynamic efficiency, then the aerodynamic efficiency of the compressor stage is improved, but high pressure gradients are induced at the outlet of the blade wheel which are detrimental to the operation of the turbomachine
Solution Approach 1:
The blade skeleton curve is modified locally in the vicinity of the platform to create a raised portion that specifically addresses the pressure gradient issue at the blade outlet, while the rest of the blade maintains its original geometry for optimal aerodynamic performance
Solution Approach 2:
The raised skeleton curve is positioned upstream to preemptively counteract the adverse pressure gradients that would otherwise develop at the blade outlet, preventing the harmful flow patterns before they can form
2Productivity
If the platform surface is modified with circumferential depression to improve aerodynamic efficiency, then the aerodynamic efficiency of the compressor stage is improved, but disparities in the speed distributions around the blades are induced, particularly in the vicinity of the root
Solution Approach 1:
The skeleton curve modification is applied locally near the platform-blade interface where the speed distribution disparities occur, allowing targeted correction of the flow uniformity issue without affecting the overall blade aerodynamic design
3Object-generated harmful factors
If the geometry of downstream impellers is modified to remedy pressure gradient issues, then the pressure gradients are improved, but the gain in efficiency from platform surface modification is lost and additional complexity is introduced
Solution Approach 1:
The pressure gradient issue is addressed at its source by modifying the blade skeleton curve upstream near the platform, preventing the formation of harmful pressure gradients before they can develop, thereby eliminating the need for downstream corrections
Solution Approach 2:
The blade skeleton curve acts as an intermediary element between the platform surface modification and the fluid flow, mediating the interaction to produce beneficial aerodynamic effects while avoiding harmful pressure gradients
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 enhances aerodynamic efficiency and maintains pressure gradients and fluid speed distributions similar to those without the circumferential depression, ensuring optimal operation of the paddle wheel, especially in supersonic flows.
Implementation Method 1
for blades required to operate in a supersonic flow
Data Source
Figure 1~5
Figure 2
Figure 3A~3Bb
AI summary
Assembly comprising a blade (20) and a platform on which the blade can be mounted, the platform surface having, between the leading edge and the trailing edge of the blade, a circumferential depression (40) the most hollow cross section (41) of which lies in the upstream half of the blade. The curve of the variations of a skeleton angle (a) of the blade as a function of the position about the axis of the rotor is termed the skeleton curve (46) and the curve of the variations of an angle as a function of the position along the axis of the rotor which in a straight line connects the points representing the skeleton angle at 10% and at 90% of the axial extent of the blade measured from the leading edge respectively is termed the linearized skeleton curve (45). In the vicinity of the platform, the skeleton curve has a raised part that lies above the linearized skeleton curve (45).