Aircraft Turbine Tip Clearance Control Under Rubbing Constraints

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Solution Overview

Problem

Existing active clearance control systems for aircraft engines do not adequately enhance engine performance and efficiency.

Innovation Solution

A method and system for controlling tip clearance between a turbine casing and blade tips using a clearance control valve, adjusting the flow of clearance control fluid to maintain optimal tip clearance based on engine parameters, and applying a limiting factor to prevent performance degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If flow cooling air is directed towards the turbine case to control tip clearance, then appropriate tip clearance is obtained, but engine performance and efficiency are not adequately enhanced

Engineering Contradiction:

Improvetip clearance controlVSAvoidengine performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The system dynamically adjusts the tip clearance parameter by controlling the flow of clearance control fluid to the turbine case, changing the radial displacement of the turbine casing to optimize clearance under varying flight conditions, thereby improving both reliability and engine performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The controller receives input from sensors measuring actual tip clearance and flight conditions, compares it with desired clearance values, and adjusts the clearance control valve accordingly to maintain optimal clearance, enabling adaptive optimization of engine performance

Inventive Principle:

Principle #23Feedback

2Loss of energy

If tip clearance is reduced to improve engine efficiency, then fuel economy improves, but risk of turbine rubbing increases

Engineering Contradiction:

Improvefuel economyVSAvoidturbine rubbing

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The system maintains a minimum safe clearance offset to prevent turbine rubbing before it occurs, while dynamically optimizing clearance to minimize energy loss and improve fuel economy under safe operating conditions

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The tip clearance is dynamically adjusted based on real-time flight conditions and turbine behavior, allowing the system to reduce clearance for efficiency when safe, and increase it when approaching dangerous limits, preventing turbine rubbing

Inventive Principle:

Principle #15Dynamics

3Productivity

If active clearance control is implemented to optimize tip clearance, then engine efficiency improves, but system complexity increases

Engineering Contradiction:

Improveengine efficiencyVSAvoidclearance control system

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The clearance control system integrates multiple functions including clearance control, performance optimization, and turbine protection within a single integrated control architecture, reducing overall system complexity while achieving multiple objectives

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The controller acts as an intermediary that processes sensor data, computes optimal clearance settings, and actuates the clearance control valve, simplifying the control architecture while enabling sophisticated clearance management for improved engine efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Improves engine efficiency and fuel economy by dynamically managing tip clearance, protecting the turbine from rubbing conditions, and ensuring stable engine operation across varying flight conditions.

Implementation Method 1

controlling a clearance control valve in flow communication with the turbine casing, the clearance control valve configured to control a flow of clearance control fluid towards the turbine casing

Methodology Applied

Scientific EffectFluid flow:

Implementation Method 2

for controlling a radial displacement of the turbine casing

Methodology Applied

Scientific EffectRadial displacement:

Data Source

PatentEP4119775B1Active clearance control system and method for an aircraft engine

Publication Date: 2026.01.07 PRATT & WHITNEY CANADA CORP

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AI summary

There is provided a system and a method (400) for controlling a tip clearance between a turbine casing and turbine blade tips of an aircraft engine. At least one operational parameter of the aircraft engine is obtained (402). Based on the at least one operational parameter, a current value of the tip clearance and a target value of the tip clearance are determined (404). A limiting factor to be applied to the target value of the tip clearance is computed (406). The limiting factor is applied (408) to the target value of the tip clearance to obtain a tip clearance demand for the aircraft engine. A tip clearance control apparatus of the aircraft engine is controlled (410) based on a difference between the current value of the tip clearance and the tip clearance demand.