Pre-swirl Contours for Gas Turbine Fan Efficiency
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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 adequately addressed by existing reduction gearboxes that add complexity, weight, and expense.
Innovation Solution
Incorporating pre-swirl contours on the inner wall of the outer nacelle positioned forward of the fan blades, which pre-swirl the airflow to reduce separation and shock losses, allowing the fan to operate efficiently at high rotational speeds synchronized with the drive turbine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the fan rotates at high rotational speeds to improve drive turbine efficiency, then the drive turbine operates at high efficiency, but shock losses and flow separation occur over fan blades
Solution Approach 1:
The pre-swirl contours are positioned forward of the fan blades to pre-condition the airflow before it reaches the fan blades. This preliminary action imparts a swirl component to the incoming air, which reduces the angle of attack on the fan blades and prevents flow separation and shock losses that would otherwise occur at high rotational speeds.
Solution Approach 2:
The pre-swirl contours modify the flow parameters (velocity distribution and flow angle) of the air entering the fan. By changing the swirl angle and radial velocity profile before the air reaches the fan blades, the system maintains efficient operation at high rotational speeds while avoiding the harmful effects of flow separation and shock losses.
2Loss of energy
If reduction gearboxes are used to allow the fan to rotate slower than the drive turbine, then fan efficiency improves, but device complexity, weight, and expense increase
Solution Approach 1:
The invention extracts and eliminates the need for reduction gearboxes by using pre-swirl contours to directly modify the airflow. This removes the complex mechanical transmission system while achieving the same goal of improving fan efficiency at high rotational speeds through aerodynamic means rather than mechanical speed reduction.
Solution Approach 2:
The mechanical reduction gearbox system is replaced with an aerodynamic solution using pre-swirl contours. Instead of mechanically reducing the fan speed, the invention uses flow conditioning to allow the fan to operate efficiently at high speeds, substituting a mechanical system with an aerodynamic one.
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
The pre-swirl contours minimize efficiency penalties by reducing airflow separation and shock losses, enabling the fan to operate effectively at high tip speeds with a low fan pressure ratio, thus enhancing the overall efficiency of the gas turbine engine.
Implementation Method 1
an outer nacelle surrounding the plurality of fan blades and including an inner wall, the inner wall of the outer nacelle including a plurality of pre-swirl contours positioned forward of the fan blades of the fan along the axial direction and extending inwardly along the radial direction
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. The gas turbine engine also includes an outer nacelle surrounding the plurality of fan blades and including an inner wall, the inner wall of the outer nacelle including a plurality of pre-swirl contours positioned forward of the fan blades of the fan along an axial direction and extending inwardly along a radial direction.