Geared Turbofan Compressor Rotor Noise Reduction
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Solution Overview
Problem
Gas turbine engines produce noise frequencies sensitive to human hearing due to fluid dynamic interactions between turbine and compressor blade rows, which are typically mitigated by controlling the vane-to-blade ratio, but this approach increases weight and reduces aerodynamic efficiency.
Innovation Solution
A gas turbine engine design featuring a gear reduction system that allows the low pressure compressor blades to operate at a rotational speed such that the product of blade count and rotational speed is greater than or equal to 5500 Hz, reducing noise frequencies sensitive to human hearing without compromising efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the vane-to-blade ratio is controlled to be above a certain number (e.g., 1.5 or greater) to achieve acoustic cut-off and reduce noise, then noise frequencies sensitive to human hearing are reduced, but weight increases and aerodynamic efficiency decreases
Solution Approach 1:
The patent changes the operational parameters of the compressor rotor by controlling the product of blade count and rotational speed to be greater than or equal to 5500 Hz. This parameter change achieves noise reduction in the human hearing-sensitive frequency range without requiring an increased vane-to-blade ratio, thereby avoiding the associated weight penalty and aerodynamic efficiency loss.
2Object-affected harmful factors
If the vane-to-blade ratio is controlled to be above a certain number (e.g., 1.5 or greater) to achieve acoustic cut-off and reduce noise, then noise frequencies sensitive to human hearing are reduced, but aerodynamic efficiency decreases
Solution Approach 1:
The patent changes the operational parameters of the compressor rotor by controlling the product of blade count and rotational speed to be greater than or equal to 5500 Hz. This parameter change achieves noise reduction in the human hearing-sensitive frequency range without requiring an increased vane-to-blade ratio, thereby avoiding the associated aerodynamic efficiency loss.
3Object-affected harmful factors
If the number of compressor blades and rotational speed are increased to meet the formula (blades×rotational speed)/60 s≧5500 Hz, then noise frequencies sensitive to human hearing are reduced, but device complexity increases
Solution Approach 1:
The patent utilizes the dynamic operational characteristics of the compressor rotor by controlling the rotational speed in conjunction with the blade count. This dynamic approach allows the product of blades and rotational speed to meet or exceed 5500 Hz, achieving noise reduction without requiring a more complex physical configuration of the rotor itself.
Data Source
AI summary
A gas turbine engine has a fan and a turbine having a fan drive turbine rotor. The fan drive turbine rotor drives a compressor rotor. A gear reduction effects a reduction in the speed of the fan relative to an input speed from the fan drive turbine rotor that drives the compressor rotor. The compressor rotor has a number of compressor blades in at least one of a plurality of rows of the compressor rotor. The blades operate at least some of the time at a rotational speed. The number of compressor blades in at least one row and the rotational speed are such that the following formula holds true for at least one row of the compressor rotor turbine:(number of blades×rotational speed)/60 s≧5500 Hz,and the rotational speed is in revolutions per minute. A method of designing a gas turbine engine and a compressor module are also disclosed.