Secondary Airflow Passage for Gas Turbine Stall Margin

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Solution Overview

Problem

Gas turbine engines face airflow distortion issues upstream of the compressor section, which can lead to stall conditions due to uneven airflow, reducing operability and requiring increased stall margin, often achieved by closing variable guide vanes at the cost of engine efficiency.

Innovation Solution

The implementation of a secondary airflow passage assembly with a movable door that allows bypass airflow to be routed into the engine airflow path based on real-time distortion assessments, using pressure measurements from integrated sensors to adjust airflow and mitigate distortion conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If variable guide vanes are closed to maintain stall margin, then compressor stall prevention is improved, but engine efficiency deteriorates

Engineering Contradiction:

Improvestall marginVSAvoidengine efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The airflow control is segmented into multiple independent pathways: the primary airflow path through the compressor and the secondary airflow passage that can be independently activated. This allows selective application of stall prevention measures only where and when needed, rather than uniformly restricting all airflow through the compressor inlet.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A secondary airflow passage acts as an intermediary pathway, introducing bypass airflow into the engine airflow path downstream of the compressor. This mediator airflow helps prevent stall conditions without requiring restriction of the main compressor inlet flow, thus avoiding the efficiency penalty associated with closing variable guide vanes.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If variable guide vanes are closed to increase stall margin headroom, then operability is improved, but airflow and pressure in compressor section are reduced

Engineering Contradiction:

Improvestall margin headroomVSAvoidairflow and pressure

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The secondary airflow passage is designed to introduce bypass airflow in advance of potential stall conditions. By preemptively adding this stabilizing airflow downstream of the compressor, the system creates stall margin headroom without needing to pre-restrict the main airflow through the compressor inlet.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the airflow parameters (adding bypass airflow) downstream of the compressor rather than modifying the compressor inlet conditions. This parameter change approach allows maintaining high compressor inlet airflow and pressure while still achieving the desired stall margin through downstream airflow modification.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If bypass airflow is routed into engine airflow path, then airflow distortion is reduced, but device complexity increases

Engineering Contradiction:

Improveairflow distributionVSAvoidsecondary airflow passage assembly

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The secondary airflow passage is positioned to address local airflow distortion issues at specific locations downstream of the compressor inlet. Rather than implementing a complex system throughout the entire airflow path, the solution applies localized airflow modification only where distortion problems occur, simplifying the overall device design.

Inventive Principle:

Principle #3Local quality

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 approach enhances the operability of the gas turbine engine by increasing stall margin headroom and improving airflow distribution, thereby reducing the likelihood of stall conditions without compromising efficiency.

Implementation Method 1

The door can allow at least a portion of the bypass airflow to flow through the airflow passage when in the open position

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 2

The door can restrict substantially all airflow through the airflow passage when in the closed position

Methodology Applied

Scientific EffectFlow control:

Implementation Method 3

using pressure measurements from integrated sensors to adjust airflow and mitigate distortion conditions

Methodology Applied

Scientific EffectPressure measurement:

Data Source

PatentUS20170284296A1Secondary airflow passage for adjusting airflow distortion in gas turbine engine

Publication Date: 2017.10.05 GENERAL ELECTRIC CO

AI summary

Systems and methods for adjusting airflow distortion in a gas turbine engine using a secondary airflow passage assembly are disclosed. A gas turbine engine can include a compressor section, a combustion section, and a turbine section in series flow and defining at least in part an engine airflow path. A casing can enclose the gas turbine engine and be at least partially exposed to a bypass airflow. The gas turbine engine can further include a secondary airflow passage assembly comprising a door and a duct, the duct defining an inlet located on the casing, the duct defining an outlet in airflow communication with the engine airflow path, the duct comprising an airflow passage extending between the inlet and outlet. The door can be moveable between an open and closed position to allow a portion of the bypass airflow to flow through the airflow passage to adjust airflow distortion.