Fan Blade Tips With Bonded Abrasive Coating for Heat Management
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Solution Overview
Problem
Erosion resistant coatings on fan blades in gas turbine engines tend to degrade due to frictional heating when the hard-anodized tips rub against abradable coatings, leading to potential damage from excessive heat.
Innovation Solution
Applying a bonded abrasive coating to the distal tip of the fan blade, which engages the abradable coating instead of the tip itself, using materials like zirconia and various bonding agents, and extending the coating onto the leading and trailing edges and sides to form corners or rounded edges, thereby reducing frictional heating and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hard-anodized fan blade tips are used to engage abradable coatings, then wear resistance is improved, but frictional heating causes erosion resistant coatings to degrade
Solution Approach 1:
A low thermal conductivity coating is applied to the fan blade tip to act as an intermediary layer between the hard-anodized tip and the abradable coating. This intermediary coating reduces the transmission of frictional heat to the erosion resistant coating, preventing degradation while maintaining wear resistance through the hard-anodized underlying structure.
Solution Approach 2:
The fan blade tip employs a composite structure combining hard-anodized aluminum (for wear resistance) with a low thermal conductivity coating material (such as ceramic or polymer composite). This composite approach allows the hard layer to provide abrasion resistance while the low thermal conductivity layer isolates the erosion resistant coating from frictional heating, resolving the contradiction between wear resistance and temperature control.
2Productivity
If abradable coatings are applied to liners, then clearance is reduced and efficiency is improved, but wear occurs on the fan blade tips
Solution Approach 1:
Different functional coatings are applied to different regions of the fan blade. The tip region receives hard-anodized coating for wear resistance and low thermal conductivity coating for heat protection, while other portions of the blade receive erosion resistant coatings. This local differentiation allows the blade to engage abradable coatings for improved efficiency while protecting the tip from excessive wear through localized hardening.
Solution Approach 2:
The physical and chemical parameters of the blade tip surface are modified through hard-anodization to change its wear characteristics. This parameter change (increased surface hardness) allows the tip to withstand the wear from engaging abradable coatings, enabling closer clearances and improved efficiency without sacrificing blade tip integrity.
3Reliability
If erosion resistant coatings are applied to fan blades, then protection is improved, but the coatings degrade due to frictional heating from abradable coating engagement
Solution Approach 1:
A low thermal conductivity coating is positioned as an intermediary layer between the erosion resistant coating and the hard-anodized tip surface that contacts the abradable coating. This intermediary layer acts as a thermal barrier, protecting the erosion resistant coating from frictional heating while allowing the tip to maintain its protective function.
Solution Approach 2:
The fan blade employs a multi-layer composite coating system where erosion resistant coating is combined with hard-anodized aluminum and low thermal conductivity material. This composite structure allows the erosion resistant coating to provide protection while the low thermal conductivity layer shields it from frictional heating, preventing degradation and maintaining reliability.
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
The bonded abrasive coating effectively reduces the temperature of the fan blade tips, preventing degradation of the erosion resistant coatings and maintaining the fatigue strength of the blades, while also adjusting clearance and distributing wear evenly across the blades.
Implementation Method 1
The distal tip may be coated with a bonded abrasive coating... as a hard-anodized fan blade tip rubs against the abradable coating of the liner, frictional heating causes the blade tip to get hot enough to degrade the polyurethane coating... The bonded abrasive coating effectively reduces the temperature of the fan blade tips
Implementation Method 2
The abradable coating may be designed to wear when engaged by the more abrasive fan blade tips, thereby reducing or limiting wear to the fan blade tips
Implementation Method 3
Abradable coatings may be used in gas turbine engines in the fan section where a minimal clearance is needed between the blade tips and the liner
Implementation Method 4
Typical abradable coatings include epoxy with a filler, such as glass microballoons, which reduce density and weight and also provide a low thermal conductivity coating... The bonded abrasive coating effectively reduces the temperature of the fan blade tips
Data Source
AI summary
A fan blade for a gas turbine engine is disclosed. The disclosed fan blade includes an airfoil having a leading edge, a trailing ling edge, a convex side, a concave side and a distal tip. The leading edge, trailing edge, convex side and concave side of the airfoil is at least partially coated with an erosion resistant coating. The distal tip of the airfoil is coated with a bonded abrasive coating. The bonded abrasive coating engages the abradable coating disposed on the fan liner and, because of its low thermal conductivity, reduces heat transfer to the distal tip of the fan blade. The reduction in heat transfer to the distal tip of the fan blade preserves the integrity of erosion resistant coatings that may be applied to the body or the airfoil of the fan blade.