Rotor Stator Clearance Control via Ventilation Modulation

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Solution Overview

Problem

Existing turbomachines face challenges in optimizing the radial clearance between the rotor and stator due to mechanical deformation and differential thermal dilations, which are not effectively addressed by current active clearance adjustment devices, particularly during cruise regimes where reduced cooling needs and stable operating conditions allow for a greater reduction in clearance.

Innovation Solution

A method and device that adjust the ventilation flow rate and temperature of air blown into the rotor cavity, using a partial closure valve in the ventilation duct to reduce the clearance between the rotor and stator, by increasing the rotor's temperature and diameter, while maintaining sufficient cooling and clearance retention through modulated ventilation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a high purge flow rate is maintained in the rotor cavity, then sufficient cooling of the rotor disks is guaranteed, but the rotor temperature remains low and clearance reduction is limited

Engineering Contradiction:

Improverotor temperatureVSAvoid rotor cooling sufficiency

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The ventilation flow rate to the rotor cavity is made dynamically adjustable through a control valve, allowing the system to transition between high flow rates for cooling and low flow rates for clearance reduction, adapting to different operational requirements

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the flow rate parameter of ventilation air to the rotor cavity, reducing it from high to low levels to allow rotor thermal dilation and clearance reduction while maintaining operational reliability through controlled modulation

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If cool air is blown at high flow rate into the rotor cavity, then rotor cooling is enhanced, but rotor thermal dilation and clearance reduction are suppressed

Engineering Contradiction:

Improveturbomachine efficiencyVSAvoidrotor temperature

Core Design Contradiction:

Loss of energyVSTemperature

Solution Approach 1:

The ventilation flow rate is periodically modulated between high and low states, allowing the rotor to experience alternating cooling and thermal dilation phases that optimize both cooling efficiency and clearance reduction at different times

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

Instead of maintaining continuously high cooling flow, the invention applies partial cooling action by reducing the ventilation flow rate to the level necessary for acceptable cooling while enabling sufficient thermal dilation for clearance reduction

Inventive Principle:

Principle #16Partial or excessive action

3Length of stationary object

If the ventilation flow rate is reduced for clearance reduction, then rotor thermal dilation increases and clearance reduces, but rotor cooling may become insufficient

Engineering Contradiction:

Improveclearance between rotor and statorVSAvoidrotor cooling effectiveness

Core Design Contradiction:

Length of stationary objectVSTemperature

Solution Approach 1:

The control system monitors rotor conditions and adjusts the ventilation flow rate accordingly, providing feedback control that maintains cooling effectiveness while achieving clearance reduction through dynamic flow modulation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The control valve acts as an intermediary element that mediates between the conflicting requirements of cooling and clearance reduction, selectively regulating the ventilation flow to balance both objectives

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

This approach allows for a more precise adjustment of clearance distribution along the turbine, achieving a greater reduction in clearance during cruise regimes and maintaining acceptable clearances during transient conditions, enhancing turbomachine efficiency and performance.

Implementation Method 1

the gas flow rate being adjusted in particular by being reduced for cruise conditions with respect to other conditions, particularly a takeoff condition, of the aircraft, the adjustment of the flow rate of gas in the partial closure state of the valve allowing an increase in the diameter of the structure of the rotor so as to reduce the clearance with the stator

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

ventilation of the rotor, this additional ventilation being adjustable, with the intention of obtaining heating (or reduced cooling) of the rotor

Methodology Applied

Scientific EffectConvection cooling: Convection

Data Source

PatentUS11149577B2Method and device for adjusting the clearance between a rotor and a concentric stator of an aircraft turbine engine

Publication Date: 2021.10.19 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A device for controlling the clearance between a rotor and a stator surrounding same, which is carried out by modifying the delivery flow carried in a rotor recess in order to provide a bleed flow that prevents the gases from the flow section from penetrating into the recess. A valve can partially close the delivery circuit, thus reducing the cooling of the rotor structure and allowing the expansion thereof and the reduction of the clearance with the stator, for certain operating speeds including cruise operating speeds. In addition, the delivery air is heated more at a lower flow rate, especially if it is made to follow a bypass provided with meanders in the hottest portions of the circuit.