Engine Inlet Inner Barrel Acoustic Perforation Without Thermal Damage
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Solution Overview
Problem
Conventional methods for forming perforations in acoustic structures, such as the inner barrel of a gas turbine engine, are complex, inefficient, and can cause damage due to mechanical drilling or high thermal conduction from laser drilling.
Innovation Solution
A forming system utilizing an ultrafast femtosecond laser that emits short pulse durations and high frequencies to create precise, uniform perforations without thermal conduction, enabling accurate and cost-effective noise reduction in acoustic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional laser drilling methods are used to form perforations, then the perforations can be created relatively quickly, but the high thermal conduction from the laser beams melts and burns the surrounding material
Solution Approach 1:
The patent applies periodic pulsed laser action instead of continuous laser drilling. The laser operates in pulses with specific duty cycles that allow the material to cool between pulses, preventing thermal accumulation and melting of surrounding material while maintaining efficient perforation formation through repeated thermal stress cycles.
Solution Approach 2:
The patent changes key laser parameters including pulse duration, peak power, and duty cycle to optimize the drilling process. By adjusting these parameters, the system achieves clean perforations without the thermal damage associated with conventional continuous laser drilling, resolving the contradiction between speed and material integrity.
2Ease of manufacture
If mechanical drilling methods are used to form perforations, then the process can be simple and straightforward, but it is time consuming, unreliable, and imprecise
Solution Approach 1:
The patent replaces the mechanical drilling system with a laser-based thermal field system. This substitution eliminates mechanical contact, tool wear, and positioning errors associated with mechanical drills, while providing non-contact, highly precise perforation formation with consistent dimensions and uniform spacing throughout the inner barrel.
3Ease of operation
If conventional laser drilling is used, then perforations can be formed without mechanical contact, but the process is relatively energy intensive and causes material damage
Solution Approach 1:
The patent optimizes laser energy parameters including pulse width, peak intensity, and repetition rate to minimize total energy consumption. By using short high-power pulses followed by cooling periods, the system achieves efficient material removal with lower overall energy input compared to conventional continuous laser drilling, while maintaining the non-contact advantage.
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 system effectively reduces noise by forming precise perforations that absorb noise without damaging the surrounding material, offering a more efficient and cost-effective process compared to conventional methods.
Implementation Method 1
A forming system utilizing an ultrafast femtosecond laser that emits short pulse durations and high frequencies to create precise, uniform perforations without thermal conduction
Data Source
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AI summary
A forming system (200) includes a femtosecond laser (202) and a control unit (204) that includes one or more processors operatively connected to the femtosecond laser (202). The femtosecond laser (202) is configured to emit laser pulses onto an inner surface (218) of a face sheet of an acoustic inner barrel (120). The acoustic inner barrel (120) includes an acoustic core (128) comprising an array of hexagonal cells (130) attached to an outer surface of the face sheet that is opposite the inner surface (218) . The control unit (204) is configured to control the femtosecond laser (202) to laser drill a plurality of perforations (150) in the face sheet via emitting laser pulses at pulse durations between about 100 femtoseconds and about 10,000 femtoseconds and at frequencies over 100,000 Hz such that the perforations (150) are formed without burning portions of the face sheet or the acoustic core (128) surrounding the perforations (150).