Partial Inlet Vanes for Transonic Fan Shock Loss Reduction
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Solution Overview
Problem
Transonic fans in turbofan engines face efficiency reductions due to shock losses and boundary layer separation, and are vulnerable to foreign object damage, particularly at the tip section of the fan blades.
Innovation Solution
The introduction of partial vanes in the inlet of the gas turbine engine, with adjustable stagger angles and heights, reduces the relative Mach number at the fan blade tips by swirling the air flow, thereby minimizing shock losses and enhancing structural support to prevent damage from foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transonic fans with high relative tip Mach number are used, then the fan can achieve higher speed and power output, but shock losses and boundary layer separation occur which reduce fan tip efficiency
Solution Approach 1:
The inlet guide vanes are positioned upstream of the fan blades to pre-condition the airflow before it reaches the fan. By adjusting the vanes, the airflow is swirled and the relative Mach number at the fan blade tips is reduced to Mach 1.3 or less before the air encounters the fan blades, preventing shock losses and boundary layer separation
Solution Approach 2:
The inlet guide vanes modify the flow parameters (velocity vector and Mach number) by introducing a swirl component. This changes the relative flow angle and reduces the relative Mach number at the fan blade tips, transforming the flow conditions to eliminate shock losses while maintaining acceptable power output
2Weight of moving object
If the fan blade tip section is designed with minimal structural support to reduce weight, then the blade can be lighter and more efficient, but the tip section becomes vulnerable to foreign object damage
Solution Approach 1:
The inlet guide vanes act as an intermediary protective element positioned between potential foreign objects and the fan blade tips. The vanes create a controlled airflow pattern that reduces the relative Mach number, thereby reducing the impact force of any foreign objects that might strike the fan blades, providing indirect protection to the lightly-supported blade tip sections
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 improves fan efficiency by reducing shock losses and rotor dynamic stress while providing protection against foreign object damage, leading to enhanced overall engine performance without altering the engine's cycle or structure.
Implementation Method 1
The vanes are configured to reduce a relative Mach number of the air flow to a value of Mach 1.3 or less at tips of the fan blades
Data Source
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AI summary
A turbofan engine including an axially extending inlet wall (28) surrounding an inlet flow path (30). A radial distance between the inlet wall (28) and an inner wall (42) adjacent the fan (12) defines a downstream height (H) of the inlet flow path (30). A plurality of vanes (50) are circumferentially spaced around the inlet, each of the vanes (50) extending radially inwardly from the inlet wall (28), a maximum radial distance between a tip (52) of each of the vanes (50) and the inlet wall (28) defining a maximum height (hmax) of the vane (50). The maximum height (hmax) of the vane (50) is at most 50% of the downstream height (H) of the flow path (30). In another embodiment, the maximum height (hmax) of the vane (50) is at most 50% of the maximum fan blade span (Smax).