Heat Accumulator Screens for Thin Trailing Edge Casting

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Solution Overview

Problem

Current lost-wax casting techniques face challenges in achieving thin or very thin trailing edges for aircraft turbomachine bladed elements, leading to issues with material penetration and metallurgical health due to heat loss and shrinkage.

Innovation Solution

Incorporating heat accumulator screens and a thermal insulation coating within the ceramic shell to maintain high temperatures and reduce heat loss, ensuring better metal fluidity and penetration into thin cavities, while the thermal insulation coating provides a gradient to optimize casting precision and metallurgical health.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional lost-wax casting is used to manufacture bladed elements, then standard trailing edge thickness (0.7 mm) can be achieved, but thin trailing edges (0.5 mm or less) cannot be produced due to material not reaching the indentations

Engineering Contradiction:

Improvetrailing edge thicknessVSAvoidmaterial penetration

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the thermal parameters of the casting system by introducing heat accumulator screens that modify the temperature distribution within the mold. This enables the metal to maintain sufficient fluidity and penetration capability even in thin trailing edge regions (0.5 mm or less), resolving the contradiction between achieving thin dimensions and ensuring reliable material filling.

Inventive Principle:

Principle #35Parameter changes

2Temperature

If heat accumulators are positioned facing outwards as in prior art, then trailing edges of standard thickness can be formed, but heat loss prevents successful casting of thin trailing edges

Engineering Contradiction:

Improveheat retentionVSAvoidheat loss

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent inverts the conventional positioning of heat accumulators by orienting them to face inwards toward the shell interior rather than outwards. This reversal creates a heat reservoir effect that reduces heat loss and maintains elevated temperatures in the mold cavity, enabling successful casting of thin trailing edges that would otherwise fail due to premature cooling.

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If the shell interior space is left empty as in prior art, then simple manufacturing is maintained, but heat loss occurs and casting precision deteriorates

Engineering Contradiction:

Improvecasting accuracyVSAvoidshell structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent makes the shell interior space multi-functional by introducing heat accumulator screens that serve dual purposes: they act as heat reservoirs to maintain casting temperature and simultaneously function as structural elements within the mold. This eliminates the need for separate heating systems while improving casting precision, resolving the contradiction between simplicity and performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The solution effectively achieves thin trailing edges with improved casting precision and metallurgical health, reducing shrinkage and enhancing the ability to penetrate low-thickness cavities, thereby improving the performance of aircraft turbomachines.

Implementation Method 1

screens forming heat accumulators arranged in the interior space of the shell, opposite the trailing edge areas oriented towards the interior

Methodology Applied

Scientific EffectHeat accumulation: Thermal Energy Storage

Implementation Method 2

a thermal insulation coating (48) made using a plurality of thermal insulation strips covering at least a portion of the outer surface of the carapace

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentEP2806989B1Shell mould for manufacturing aircraft turbomachine bladed elements using the lost wax moulding technique and comprising screens that form heat accumulators

Publication Date: 2019.03.13 SAFRAN AIRCRAFT ENGINES SAS

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AI summary

The present invention relates to a shell mould (200) for manufacturing aircraft turbomachine bladed elements using the lost-wax moulding technique, and comprising: - shell mould bladed elements (1b) comprising a blade portion (2b) situated between a first end part (4b) delimiting the impression of a platform (8b) and a second end part (6b) delimiting the impression of another platform (8b), the blade portion comprising a trailing edge zone (30b); - a metal feeder (12b) having a central axis (14b) around which the bladed elements (1b) are distributed; and according to the invention, the shell mould is equipped with one or a number of screens (29b) that form accumulators of heat and are arranged in a shell mould interior space (28b) facing the inwardly-directed trailing edge zones (30b).