Geared Propulsor Blade Stagger Angle for Particulate Rejection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Gas turbine engines face damage from ingested particulate matter due to its inability to effectively reject foreign objects into the bypass flow, especially in geared turbofan architectures with high bypass ratios and low pressure ratios.

Innovation Solution

The design incorporates a propulsor with a staggered blade configuration and a geared architecture, where the propulsor is driven at a lower angular speed by a gear assembly, allowing for a reduced stagger angle that increases the likelihood of particulate matter being rejected into the bypass flow rather than entering the core flow, along with a variable area nozzle to control pressure ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the propulsor is driven at higher angular speed with severe stagger angle, then the engine can achieve higher power output, but particulate matter rejection into bypass flow decreases and core flow contamination increases

Engineering Contradiction:

Improveengine power outputVSAvoidparticulate matter ingestion into core flow

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by reducing the propulsor's angular speed through gear assembly, which changes the operational conditions to enable effective particulate rejection. The lower speed allows the reduced stagger angle to function properly, dynamically adjusting the system's operating parameters to resolve the contradiction between power output and particle rejection.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes key parameters including reducing the stagger angle from severe to reduced values, and lowering the propulsor angular speed through gearing. These parameter changes enable the propulsor to reject particulate matter into bypass flow while maintaining acceptable power output, resolving the technical contradiction.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If the stagger angle is reduced to improve particulate rejection, then particles are directed into bypass flow, but the propulsor requires lower angular speed operation which may reduce power density

Engineering Contradiction:

Improveparticulate matter rejectionVSAvoidpropulsor angular speed

Core Design Contradiction:

Object-affected harmful factorsVSSpeed

Solution Approach 1:

The gear assembly acts as an intermediary mechanism between the engine core and the propulsor. It mediates the speed relationship, allowing the propulsor to operate at lower angular speed with reduced stagger angle for effective particle rejection, while the engine core maintains its operational speed and power output characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If a geared architecture is introduced to reduce propulsor speed, then particulate rejection improves, but device complexity increases

Engineering Contradiction:

Improveparticulate matter rejectionVSAvoidengine architecture complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The geared turbofan architecture provides multi-functionality: the gear assembly not only reduces propulsor speed to enable particle rejection, but also allows independent optimization of core and bypass flows, and enables the use of reduced stagger angle geometry. This universal approach resolves the contradiction by making the additional complexity serve multiple beneficial functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances particulate rejection and propulsive efficiency, reducing the risk of engine damage and improving performance by ensuring that ingested particles are directed into the bypass flow, thereby protecting the core engine components.

Implementation Method 1

The blade stagger is typically apparent when viewing the fan axially from the front of the engine. The stagger angle is less than 10 degrees within an inboard 20 percent of a span of each propulsor blade

Methodology Applied

Scientific EffectAerodynamic flow direction control:

Implementation Method 2

a geared architecture, where the propulsor is driven at a lower angular speed by a gear assembly

Methodology Applied

Scientific EffectMechanical gear reduction: Gear

Implementation Method 3

along with a variable area nozzle to control pressure ratios

Methodology Applied

Scientific EffectPressure ratio control:

Data Source

PatentEP2543829B1Gas turbine propulsor blade with stagger angle for dirt rejection

Publication Date: 2022.10.26 RTX CORP

Figure 1
Figure 2
Figure 3~4

AI summary

A gas turbine engine (20) includes a spool (30), a turbine (46) coupled to drive the spool (30), a propulsor (42) coupled to be rotated about an axis by the turbine (46) through the spool (30), and a gear assembly (48) coupled between the propulsor (74) and the spool (30) such that rotation of the turbine (46) drives the propulsor (42) at a different speed than the spool (30). The propulsor (42) includes a hub (76) and a row of propulsor blades (74) that extend from the hub (76). Each of the propulsor blades (74) has a span between a root (68) at the hub (76) and a tip (80), and a chord (30) between a leading edge (82) and a trailing edge (84). The chord forms a stagger angle α with the axis (A), and the stagger angle α is less than 15° at a position along the propulsor blade (74) that is within an inboard 20% of the span.