Part-Span Inlet Guide Vanes for Gas Turbine Shock Loss Reduction
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Solution Overview
Problem
Gas turbine engines face inefficiencies due to high rotational speeds of the fan leading to shock losses and flow separation, which are not effectively mitigated by existing reduction gearboxes that add complexity, weight, and expense.
Innovation Solution
The implementation of part-span inlet guide vanes that pre-swirl airflow upstream of the fan blades, with specific configurations such as varying span, swirl angles, and solidity, to minimize these inefficiencies while maintaining high rotational speeds of the drive turbine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan rotates at high rotational speeds to improve engine efficiency, then the drive turbine operates at high efficient rotational speeds, but shock losses and flow separation occur over fan blades
Solution Approach 1:
The inlet guide vanes perform preliminary action by pre-swirling the airflow before it reaches the fan blades. This pre-swirl prepares the airflow in advance, reducing shock losses and flow separation when the air encounters the fan blades at high rotational speeds, thus resolving the contradiction between high speed efficiency and shock losses
Solution Approach 2:
The inlet guide vanes act as an intermediary element between the incoming airflow and the fan blades. By positioning the vanes upstream of the fan, they mediate the interaction by modifying the airflow characteristics before the main interaction with the fan blades occurs, reducing harmful shock losses and flow separation
2Loss of energy
If a reduction gearbox is used to allow the fan to rotate slower, then flow separation and shock losses are reduced, but complexity, weight, and expense increase
Solution Approach 1:
The invention extracts the speed reduction function from the mechanical gearbox and relocates it to the airflow control system. By using inlet guide vanes to pre-swirl the airflow, the system achieves the beneficial effects of slower effective fan speed without requiring a physical gearbox, thus eliminating the complexity, weight, and expense associated with gearbox components
Solution Approach 2:
The patent replaces the mechanical speed reduction system (gearbox) with an aerodynamic solution using inlet guide vanes. Instead of mechanically reducing the fan speed, the system uses pre-swirling vanes to modify the airflow characteristics, achieving the same beneficial effect through a non-mechanical, lighter, and simpler approach
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 configuration reduces shock losses and flow separation, allowing the fan to operate efficiently at high rotational speeds by pre-swirling the airflow, thereby offsetting efficiency penalties and enhancing overall engine performance.
Implementation Method 1
a plurality of part-span inlet guide vanes attached to the outer nacelle at a location forward of the plurality of fan blades along the axial direction. Each of the plurality of inlet guide vanes defines an IGV span along the radial direction
Implementation Method 2
rotation of the fan at relatively high rotational speeds can lead to inefficiencies, such inefficiencies stemming from, e.g., shock losses and flow separation of an airflow over fan blades of the fan
Data Source
AI summary
A gas turbine engine includes a turbomachine and a fan rotatable by the turbomachine. The fan includes a plurality of fan blades, each of the plurality of fan blades defining a fan blade span along a radial direction. The gas turbine engine further includes an outer nacelle surrounding the plurality of fan blades and a plurality of part-span inlet guide varies attached to the outer nacelle at a location forward of the plurality of fan blades along an axial direction. Each of the plurality of inlet guide vanes defines an IGV span along the radial direction, the IGV span being at least about five percent of the fan blade span and up to about fifty-five percent of the fan blade span.