Geared Turbofan Compressor Rotor Noise Reduction

Solution Overview

Problem

Gas turbine engines produce noise frequencies sensitive to human hearing due to fluid dynamic interactions between blade and vane rows, which are often 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 turbine and compressor to operate at higher speeds, with a formula of (number of blades × rotational speed)/60 ≥ 5500 Hz, reducing noise sensitivity to human hearing without compromising efficiency.

Engineering Contradictions & Design Principles

VSEngineering 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 sensitivity to human hearing, then noise sensitivity is reduced, but weight increases and aerodynamic efficiency decreases

Engineering Contradiction:

Improvenoise sensitivity to human hearingVSAvoidcompressor rotor weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent changes the operational parameters (rotational speed and number of blades) rather than the structural ratio (vane-to-blade). By increasing rotational speed and/or number of blades to satisfy (number of blades × rotational speed)/60 ≥ 5500 Hz, the design achieves noise reduction without being constrained by fixed vane-to-blade ratios, thereby avoiding the weight and efficiency penalties associated with traditional acoustic cut-off designs

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic operation where the compressor rotor operates at variable high speeds. The gear reduction system enables the low pressure compressor to operate at speeds significantly higher than the fan speed, allowing the noise frequency condition to be satisfied dynamically through speed modulation rather than through fixed geometric ratios

Inventive Principle:

Principle #15Dynamics

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 sensitivity to human hearing, then noise sensitivity is reduced, but aerodynamic efficiency decreases

Engineering Contradiction:

Improvenoise sensitivity to human hearingVSAvoidaerodynamic efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent changes the operational parameters (rotational speed and number of blades) rather than the structural ratio (vane-to-blade). By increasing rotational speed and/or number of blades to satisfy (number of blades × rotational speed)/60 ≥ 5500 Hz, the design achieves noise reduction without being constrained by fixed vane-to-blade ratios, thereby avoiding the weight and efficiency penalties associated with traditional acoustic cut-off designs

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic operation where the compressor rotor operates at variable high speeds. The gear reduction system enables the low pressure compressor to operate at speeds significantly higher than the fan speed, allowing the noise frequency condition to be satisfied dynamically through speed modulation rather than through fixed geometric ratios

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If a gear reduction system is introduced to allow distinct speeds for fan and low pressure compressor, then noise frequency control becomes possible, but device complexity increases

Engineering Contradiction:

Improvenoise frequency sensitivityVSAvoidgear reduction system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The gear reduction system acts as an intermediary mechanism between the low pressure turbine and the fan/compressor. This intermediary allows independent speed control of the fan and low pressure compressor, enabling the compressor to operate at speeds that satisfy the noise frequency condition while the fan operates at its optimal speed, thus decoupling their speed constraints

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8632301B2Low noise compressor rotor for geared turbofan engine

Publication Date: 2014.01.21 RTX CORP

AI summary

A gas turbine engine has a fan, a compressor section having a low pressure portion and a high pressure portion, a combustor section, and a turbine having a low pressure portion. The low pressure turbine portion drives the low pressure compressor portion and the fan. A gear reduction effects a reduction in the speed of the fan relative to a speed of the low pressure turbine and the low pressure compressor portion. At least one of the low pressure turbine portion and low pressure compressor portion has a number of blades in each of a plurality of rows. The blades operate at least some of the time at a rotational speed. The number of blades and the rotational speed are such that the following formula holds true for at least one of the blade rows of the at least one of the low pressure turbine portion and/or the low pressure compressor sections: (number of blades×rotational speed)/60≧5500. The rotational speed is an approach speed in revolutions per minute.