Turbomachine Casing Ventilation Shield Design

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Solution Overview

Problem

Existing ventilation devices for turbomachine turbine casings are inefficient in cooling due to hot air recirculation, which reduces the performance of the low pressure turbine by increasing the clearance between moving blades and abradable rings through thermal expansion, leading to decreased efficiency.

Innovation Solution

The proposed ventilation device features a shield with an elliptical shape surrounding the main ring, creating dead zones that thermally insulate the main ring and reduce the temperature of the cold air flow, while minimizing pressure drop and external bulk, with the shield being in intimate contact with the ramp and filled with air or argon to enhance cooling efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional ring-shaped ramps are used for ventilation, then the device structure is simple, but hot air recirculation occurs reducing cooling efficiency

Engineering Contradiction:

Improvestructural simplicityVSAvoidcooling efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The conventional single ring ramp is segmented into multiple discrete ramps arranged circumferentially around the turbine casing. Each ramp is separated from others, creating distinct cooling zones that prevent hot air recirculation between adjacent ramps, thereby improving cooling efficiency while maintaining manufacturing simplicity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A shield element is introduced as an intermediary component between the ramp and the turbine casing. This shield redirects the airflow to prevent hot air from recirculating back to the ramp inlet, acting as a mediator that improves cooling efficiency without significantly complicating the overall structure

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If cooling air temperature is reduced to improve cooling performance, then thermal expansion decreases, but the air flow requires more energy to maintain pressure

Engineering Contradiction:

Improveair flow temperatureVSAvoidenergy for air flow

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The hot air recirculation path is extracted and isolated from the cooling air flow path using the shield element. By removing the harmful hot air from the cooling air intake zone, the system can maintain lower cooling air temperatures without requiring excessive pressure, thus reducing the energy penalty while improving cooling performance

Inventive Principle:

Principle #2Taking out (Extraction)

3Productivity

If the clearance between moving blades and abradable rings is reduced to improve turbine efficiency, then performance increases, but the housing becomes more sensitive to thermal expansion

Engineering Contradiction:

Improveturbine efficiencyVSAvoidclearance stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The ventilation device applies preliminary cooling action to the turbine casing before thermal expansion occurs. By continuously supplying cooled air to the housing, the system preemptively counteracts thermal expansion that would otherwise increase clearances, maintaining stable clearances and high turbine efficiency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The cooling system creates a feedback mechanism where cooled air reduces housing temperature, which in turn maintains stable clearances between moving blades and abradable rings. This stable clearance configuration optimizes turbine efficiency while the continuous cooling provides feedback control to prevent thermal drift

Inventive Principle:

Principle #23Feedback

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 improves the cooling performance by reducing the temperature of the cold air flow and minimizing heat transfer from hot air recirculation, leading to increased efficiency and reduced thermal expansion, thus enhancing the performance of the low pressure turbine.

Implementation Method 1

creating dead zones that thermally insulate the main ring and reduce the temperature of the cold air flow, while minimizing pressure drop and external bulk

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

The pressurized air is projected through the perforations in the manifolds onto the external surface of the turbine housing, thereby cooling it

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentEP3350417B2Device for ventilation of a turbomachine turbine casing

Publication Date: 2023.06.21 SAFRAN AIRCRAFT ENGINES SAS

Figure 1
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Figure 4

AI summary

The invention relates to a ventilation device for a turbomachine turbine casing, comprising a plurality of line sets (16') configured to spray air over the turbine casing, the line sets being arranged next to one another, each line set comprising a main ring (161) in which air circulates, the main ring (161) comprising orifices (17') configured to spray a stream of air towards the turbine casing, the line set comprising a shield (162) configured to isolate the main ring (161) from a stream of air returning from the turbine casing towards the line sets after having been sprayed towards the turbine casing, the said shield (162) enveloping the main ring (161) and having orifices aligned with the orifices of the main ring (161).