Boundary Layer Ingestion Fan Blade Blockage Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current aircraft propulsion systems face inefficiencies due to downstream wake and jet mixing losses, particularly in conventional tube-and-wing aircraft, where fuselage boundary layer ingestion (BLI) is the most feasible but requires aerodynamic design optimization to enhance propulsive efficiency without increasing weight or drag.
Innovation Solution
A boundary layer ingestion fan system is designed with a nacelle and fan configuration that includes a hub with rotating blades, optimized blade geometry, and specific blade blockage ratios to tolerate distortion and improve propulsive efficiency by preventing dissipation that would otherwise occur in the wake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If boundary layer ingestion is implemented to improve propulsive efficiency, then propulsive efficiency increases, but weight and drag may increase
Solution Approach 1:
The patent applies parameter changes by optimizing blade geometric parameters (chord length, span, inlet angle, thickness distribution) and operational parameters (rotational speed, inlet velocity) to achieve efficient boundary layer ingestion. The blade blockage ratio is specifically set between 0.2-0.4 to balance efficiency and distortion tolerance, representing a deliberate parameter optimization to resolve the contradiction between efficiency improvement and system complexity/weight
2Use of energy by moving object
If boundary layer ingestion is implemented to improve propulsive efficiency, then propulsive efficiency increases, but drag may increase
Solution Approach 1:
The patent converts the harmful boundary layer (which normally causes drag and wake losses) into a beneficial resource by ingesting it through the fan. The depressed inlet velocity boundary layer is transformed into useful flow that passes through the rotor, reducing downstream wake and jet mixing losses while generating thrust, thus converting drag-inducing flow into efficiency-enhancing flow
3Reliability
If blade blockage is increased to tolerate distortion, then distortion tolerance improves, but efficiency may decrease
Solution Approach 1:
The patent optimizes the blade blockage ratio parameter to a specific range (0.2-0.4) that balances distortion tolerance and efficiency. This parameter optimization allows the fan to handle the distorted boundary layer flow while maintaining acceptable aerodynamic performance, resolving the contradiction between reliability and efficiency
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 fan system enhances propulsive efficiency by reducing losses and increasing the ratio of thrust to power input, achieving efficiencies beyond unity by effectively managing inlet and jet velocities, thereby improving aircraft performance.
Implementation Method 1
a blade lift coefficient, Cl, for each span position; wherein the blade geometry is defined such that the fan exhibits the requisite distortion tolerance encountered in such an installation
Implementation Method 2
Boundary layer ingestion (often abbreviated to BLI) is a technique that may be used to improve aircraft propulsive efficiency by reducing downstream wake and jet mixing losses
Data Source
AI summary
A boundary layer ingestion fan system for location aft of the fuselage of an aircraft is shown. It comprises a nacelle defining a duct, and a fan located within the duct. The fan comprises a hub arranged to rotate around a rotational axis (A-A) and a plurality of blades attached to the hub. A blade blockage, which is the ratio of the blade thickness to the product of the circumferential pitch and the cosine of a blade inlet angle (t/s·cosβ1), is 0.25 or greater at the 0 percent span position.