Turbine Tip Clearance Control via Dynamic Adjustment

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In gas turbine engines, the varying tip clearance between blades and the casing due to thermal and centrifugal loading affects efficiency and leads to potential tip rub, which reduces engine performance and shortens component life, as existing control systems either overshoot turbine speed or temperature limits, causing premature maintenance.

Innovation Solution

A method and system that measure turbine speed and temperature, calculate optimal tip clearance using a proportional-integral algorithm, and adjust the clearance to manage speed and temperature margins, allowing for closed-loop control and reduced data frequency requirements, utilizing existing sensors and actuators to maintain efficiency within limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If tip clearance is reduced to improve turbine efficiency, then working fluid leakage decreases and efficiency improves, but the risk of tip rub increases

Engineering Contradiction:

Improveworking fluid leakageVSAvoidtip rub risk

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The tip clearance control system dynamically adjusts the clearance gap between blade tips and casing based on real-time operating conditions (speed, temperature). The system transitions from a static clearance design to a dynamic control approach where the clearance is continuously modulated to maintain optimal values across different flight conditions, resolving the contradiction between minimizing leakage and preventing tip rub.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the physical parameter of tip clearance dynamically by controlling thermal expansion of the casing through cooling air flow. By adjusting the temperature of the casing (thermal parameter), the clearance gap is modified in real-time to match optimal values for different operating conditions, thereby reducing energy loss without causing tip rub.

Inventive Principle:

Principle #35Parameter changes

2Power

If turbine speed and temperature margins are increased to improve performance, then engine output increases, but component stress and deterioration accelerate

Engineering Contradiction:

Improveengine outputVSAvoidcomponent life

Core Design Contradiction:

PowerVSDuration of action of stationary object

Solution Approach 1:

The control system implements feedback by continuously measuring turbine speed and temperature, comparing them against optimal operating envelopes, and adjusting tip clearance accordingly. This closed-loop control enables the system to operate at maximum performance limits while automatically preventing excursions that would cause excessive stress or temperature, thereby extending component life.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system takes preliminary action by proactively adjusting tip clearance before the turbine reaches critical speed or temperature limits. By anticipating approaching limits and pre-adjusting clearance to manage thermal and centrifugal loading, the system prevents harmful conditions before they occur, balancing performance with component durability.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If tip clearance is minimized at all operating conditions, then turbine efficiency is maximized, but tip rub occurs during transient conditions

Engineering Contradiction:

Improveturbine efficiencyVSAvoidtip rub during transients

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system dynamically adapts tip clearance to transient operating conditions by detecting changes in speed and temperature rates of change. During transient phases (acceleration, deceleration, altitude changes), the system temporarily increases clearance to accommodate thermal and centrifugal expansion, then returns to minimal clearance during steady-state operation, thus maintaining efficiency without causing tip rub.

Inventive Principle:

Principle #15Dynamics

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 effectively manages turbine speed and temperature margins, maintaining efficiency while reducing the risk of tip rub and extending component life by optimizing tip clearance, thus improving engine performance and reducing maintenance needs.

Implementation Method 1

the blades and casing expand and contract at different rates to each other, due to thermal and centrifugal loading

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the blades and casing expand and contract at different rates to each other, due to thermal and centrifugal loading

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 3

cool air blown towards the casing to arrest its growth or shrink it radially

Methodology Applied

Scientific EffectConvection cooling: Convection

Data Source

PatentUS10890083B2Turbine tip clearance

Publication Date: 2021.01.12 ROLLS ROYCE PLC

AI summary

A method of controlling turbine tip clearance includes measuring turbine speed; measuring turbine temperature; measuring parameters indicative of current operating conditions; determining limits for the turbine speed and turbine temperature; calculating target tip clearance from the turbine speed, turbine temperature and parameters, to optimise turbine efficiency within the turbine speed and turbine temperature limits; and controlling turbine tip clearance apparatus to the calculated target tip clearance.