Twisted Variable Inlet Guide Vanes for Compressor Noise Reduction
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Solution Overview
Problem
Compressors with axial inlet guide vanes in radial inlets often experience undesirable vortex whistle noise due to high IGV angles during low engine conditions, which affects low-speed operability and flow capacity.
Innovation Solution
The compressor employs twisted inlet guide vanes with a non-linear distribution of twist angles, varying from a smaller angle near the hub to a larger angle near the tip, to optimize swirl profiles and reduce vortex whistle by ensuring a more uniform swirl distribution at the rotor entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If axial inlet guide vanes are used in radial inlets, then the engine length is reduced, but vortex whistle noise increases during low-speed conditions
Solution Approach 1:
The inlet guide vane is designed with non-uniform twist distribution along its span, where different sections have different twist angles. The hub region has smaller twist angles while the tip region has larger twist angles, creating local variations in flow guidance that prevent uniform vortex formation and reduce whistle noise while maintaining compact engine length
Solution Approach 2:
The twist angle parameter of the inlet guide vane is varied non-linearly along the span direction. This parameter change creates a non-uniform swirl distribution at the rotor inlet, preventing the formation of coherent vortices that cause whistle noise, while still achieving the compact axial configuration
2Productivity
If high IGV angles are used during ground or flight idle conditions, then flow capacity is increased, but vortex whistle noise is generated
Solution Approach 1:
Different sections of the inlet guide vane (hub vs. tip) have different twist angles, creating localized flow control. This allows the vane to handle high flow capacity requirements while preventing uniform vortex formation that causes whistle noise during idle conditions
Solution Approach 2:
The non-uniform twist distribution is built into the vane geometry beforehand, preparing the flow to enter the rotor with an optimized swirl profile before the vortex whistle phenomenon can occur. This preliminary flow conditioning prevents noise generation while maintaining flow capacity
3Reliability
If uniform swirl profile is achieved at rotor entry, then compressor efficiency is improved, but device complexity increases
Solution Approach 1:
The vane geometry incorporates local variations in twist angle along the span, with the hub region having smaller angles and the tip region having larger angles. This local differentiation creates the desired uniform swirl profile at the rotor inlet while maintaining a relatively simple overall vane structure that can be manufactured using conventional methods
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 design reduces or eliminates vortex whistle, improves low-speed performance, and maintains high-speed efficiency by providing a cleaner flow and lower acoustic signature, enhancing compressor efficiency and operability.
Implementation Method 1
Variable inlet guide vanes (IGV) are used to introduce swirl into a compressor rotor to improve low speed operability as well as increase the flow capacity at high speeds
Implementation Method 2
An acoustic condition called Vortex Whistle has been found to occur in compressors with axial IGVs located in radial inlets. The twisted variable inlet guide vane reduces or eliminates vortex whistle
Data Source
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AI summary
A compressor for a gas turbine engine with variable inlet guide vanes (42) each defining an airfoil portion (48) twisted such that at each location of the airfoil portion (48) along the pivot axis (P), an angle (α) is defined between a respective chord extending between the leading and trailing edges (50, 52) and a same reference plane (54) containing the pivot axis (P) and extending radially with respect to the compressor. The angle, which is measured along a direction of rotation of the rotor, varies from a minimum value near the hub side wall (34) to a maximum value near the shroud side wall (36).