Geared Gas Turbine Compressor Noise Reduction via Vane-Blade Ratio
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engines, particularly the low pressure turbine and compressor sections, generate significant noise due to fluid dynamic interactions between blade and vane rows, which is not effectively mitigated in existing designs, especially in geared engines with high corrected tip speeds.
Innovation Solution
The design incorporates a gear reduction system allowing the fan and low pressure compressor to operate at distinct speeds, with a vane-to-blade ratio of 1.8 or greater and a corrected tip speed of 480 ft/sec or more, facilitating noise reduction through the 'cutoff mechanism' by preventing the fundamental blade passage tone from propagating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the low pressure turbine drives the low pressure compressor at high speed, then power transfer efficiency is improved, but noise from fluid dynamic interaction between blade and vane rows increases
Solution Approach 1:
The patent changes the geometric parameters of the compressor stage by setting a specific vane-to-blade ratio (≥1.8) and corrected tip speed (≥480 ft/sec), which modifies the fluid dynamic interaction characteristics to reduce noise while maintaining power transfer efficiency
Solution Approach 2:
The patent utilizes the high corrected tip speed, which normally increases noise, but combines it with the specific vane-to-blade ratio to create a cutoff mechanism that actually reduces noise by preventing blade passage tone propagation
2Object-generated harmful factors
If a gear reduction is introduced to allow distinct speeds for fan and low pressure compressor, then noise reduction is achieved, but device complexity increases
Solution Approach 1:
The patent segments the power transmission system by introducing a gear reduction mechanism that allows the fan and low pressure compressor to operate at distinct speeds, separating their speed control and enabling independent optimization of each component
3Object-generated harmful factors
If the vane-to-blade ratio is increased to ≥1.8, then noise reduction through cutoff mechanism is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter values (vane-to-blade ratio ≥1.8 and corrected tip speed ≥480 ft/sec) that must be manufactured with high precision to achieve the desired noise reduction through the cutoff mechanism
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 approach significantly reduces noise from the low pressure compressor, achieving a higher power density and compact engine design while maintaining efficient power transfer, applicable to high-thrust engines like those producing 15,000 pounds of thrust or more.
Implementation Method 1
a gear reduction effecting a reduction in the speed of the fan relative to a speed of the low pressure turbine
Implementation Method 2
noise is produced by fluid dynamic interaction between the blade rows and the vane rows
Implementation Method 3
facilitating noise reduction through the 'cutoff mechanism' by preventing the fundamental blade passage tone from propagating
Implementation Method 4
the low pressure turbine for driving the low pressure compressor and the fan
Data Source
Figure 1
AI summary
A gas turbine engine (20) according to an exemplary aspect of the present disclosure includes, among other things, a fan (42), a compressor section (24) having a low pressure compressor (44) and a high pressure compressor (52), a combustor section (26), and a turbine section (28) having a low pressure turbine (46), the low pressure turbine (46) for driving the low pressure compressor (44) and the fan (42); a gear reduction (48) effecting a reduction in the speed of the fan (42) relative to a speed of the low pressure turbine (46) and the low pressure compressor (44); and at least one stage of the compressor section (24) having a ratio of vanes to blades that is greater than or equal to 1.8. The corrected tip speed of the blades is greater than or equal to 480 ft/sec at an approach speed.