Compressor Rotor Blade with Tip-Enhanced Camber
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Solution Overview
Problem
Conventional compressor rotor blades experience flow blockage and reduced stall margin due to tip vortex formation and weak endwall flow, leading to efficiency penalties and potential stall, despite existing casing treatments that only partially address tip leakage.
Innovation Solution
The design features a rotor blade airfoil with a normalized camber profile that increases towards the tip, combined with a dihedral leading edge and possibly trailing edge, to enhance endwall flow and reduce tip blockage, featuring a normalized camber greater than 2.2 in the outer span region and greater than 1.7 in the inner span region, along with a dihedral angle between −10 and +10 degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional compressor rotor blades are used with standard camber profiles, then the compressor can maintain simple blade design and manufacturing, but tip vortex formation occurs leading to flow blockage and reduced stall margin
Solution Approach 1:
The patent applies local quality by implementing a non-uniform camber distribution along the blade span, with specifically increased camber in the outer span region (normalized camber > 2.2) compared to the inner span region (normalized camber > 1.7). This localized variation in camber intensity addresses the tip vortex problem specifically at the outer span where it occurs, without unnecessarily complicating the entire blade structure.
Solution Approach 2:
The patent changes the camber parameter distribution along the blade span to resolve the contradiction. By increasing the normalized camber value in the outer span region to greater than 2.2 (compared to conventional uniform or decreasing distributions), the blade geometry is modified to strengthen endwall flow and reduce tip blockage, thereby improving stall margin while maintaining a manageable design complexity.
2Loss of energy
If casing treatments such as circumferential grooves are used to reduce tip leakage, then tip leakage flow levels are reduced, but efficiency penalties occur and remaining tip flow still creates losses and blockage
Solution Approach 1:
The patent changes the camber parameter distribution along the blade span to resolve the contradiction. By increasing the normalized camber value in the outer span region to greater than 2.2 (compared to conventional uniform or decreasing distributions), the blade geometry is modified to strengthen endwall flow and reduce tip blockage, thereby improving stall margin while maintaining a manageable design complexity.
Solution Approach 2:
The patent converts the harmful tip leakage flow into a beneficial effect by designing the cambered airfoil to strengthen endwall flow. The increased camber in the outer span region creates a pressure gradient that drives the tip leakage flow downstream more effectively, converting what was previously a harmful blockage into a controlled flow pattern that reduces losses and improves compressor efficiency.
3Productivity
If weak endwall flow is present near the endwalls, then the compressor can maintain simpler blade design, but vortices remain in the rotor tip region leading to blockage and reduced pressure rise
Solution Approach 1:
The patent applies local quality by implementing a non-uniform camber distribution along the blade span, with specifically increased camber in the outer span region (normalized camber > 2.2) compared to the inner span region (normalized camber > 1.7). This localized variation in camber intensity addresses the tip vortex problem specifically at the outer span where it occurs, without unnecessarily complicating the entire blade structure.
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 configuration strengthens endwall flow and pressure, reducing tip blockage and increasing throttle margin by over 5% with no loss in design point efficiency, as analyzed through Viscous 3-D CFD comparisons, by effectively convecting weak flow downstream and reducing vortex accumulation.
Implementation Method 1
the flow or pressure distribution of the air as it is being compressed through the stator vanes and rotor blades is a complex three dimensional flow field varying circumferentially around the compressor, radially along the span of the vane and blade airfoils, and axially along the circumferentially opposite pressure and suction sides of the airfoils
Implementation Method 2
The pressure difference between pressure side and suction side of the airfoil drives flow through the tip gap of the compressor rotor
Implementation Method 3
This tip flow can roll up into a vortex, which tends to collect on the pressure side surface of the circumferentially adjacent blade
Implementation Method 4
Weak endwall flow allows the aforementioned vortices to remain in the rotor tip region, rather than being convected downstream
Implementation Method 5
caused by cumulative effects of skin friction and secondary flows
Data Source
AI summary
A rotor blade having an airfoil for a compressor is described. The airfoil has an airfoil root, an airfoil tip located at a spanwise distance from the airfoil root, a leading edge extending from the airfoil root to the airfoil tip, an inner span region (“S1”) between the airfoil root and a first height location on the airfoil leading edge, a midspan region (“S2”) between the first height location and a second height location on the airfoil leading edge located radially outward from the first height location; an outer span region (“S3”) between the second height location and the airfoil tip, wherein the airfoil has a normalized camber profile such that the normalized camber increases in the outer span region in a spanwise direction towards the tip and is more than 2.2 in the outer span region.