Additively Manufactured Turbine Engine Case for Clearance Control

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Solution Overview

Problem

Existing isogrid engine cases in gas turbine engines face challenges in managing thermal expansion and structural integrity due to differential thermal expansion between materials, leading to potential clearance issues and deformation under varying temperature conditions.

Innovation Solution

The use of a hybrid alloy structure comprising a titanium alloy for the wall and a dissimilar alloy, such as iron-nickel-cobalt or aluminum, for the ribs, combined with additive manufacturing to create hollow ribs with venting features, enhances thermal management and structural integrity by controlling thermal expansion and reducing stress concentrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single alloy material is used for both the wall and ribs in the isogrid structure, then manufacturing simplicity is maintained, but thermal expansion management and structural integrity under thermal loading are compromised

Engineering Contradiction:

Improvestructural integrityVSAvoidmaterial composition

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies composite materials by combining two different alloys in a single isogrid structure: a first alloy (e.g., titanium alloy) for the wall and a second alloy (e.g., aluminum alloy or iron-nickel-cobalt alloy) for the ribs. This composite approach allows each material to be selected for its specific thermal and mechanical properties, enabling differential thermal expansion management while maintaining structural integrity under thermal loading conditions.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent implements local quality by assigning different material properties to different parts of the structure. The wall and ribs have different alloy compositions tailored to their specific functional requirements: the wall material is optimized for its thermal and mechanical environment, while the rib material is optimized for its role in thermal expansion compensation and structural support. This localized material differentiation resolves the contradiction between reliability and complexity.

Inventive Principle:

Principle #3Local quality

2Reliability

If dissimilar alloys are used for wall and ribs, then thermal expansion compensation is improved, but manufacturing complexity and bonding difficulty increase

Engineering Contradiction:

Improvethermal expansion compensationVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies parameter changes by carefully selecting and controlling the material parameters (alloy compositions, thermal expansion coefficients, mechanical properties) of the dissimilar alloys used in the structure. By adjusting these parameters, the patent optimizes thermal expansion compensation while managing the challenges of manufacturing dissimilar metal joints. The specific selection of alloys with complementary thermal and mechanical properties helps resolve the contradiction between improved thermal performance and manufacturing complexity.

Inventive Principle:

Principle #35Parameter changes

3Weight of moving object

If traditional machining methods are used for the entire isogrid structure, then material uniformity is maintained, but weight and manufacturing time increase

Engineering Contradiction:

Improvestructure weightVSAvoidmanufacturing speed

Core Design Contradiction:

Weight of moving objectVSProductivity

Solution Approach 1:

The patent applies segmentation by dividing the manufacturing process into two distinct segments: traditional machining for the wall portion and additive manufacturing for the ribs. This segmentation allows each manufacturing method to be used where it provides the greatest benefit: machining for the monolithic wall structure and additive manufacturing for the complex rib geometry. This division enables weight reduction through material optimization in the ribs while maintaining manufacturing efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamics by combining two different manufacturing methodologies (subtractive machining and additive manufacturing) within a single structure. This dynamic approach allows the manufacturing process to adapt to the specific requirements of different structural components: using machining where material removal is efficient and additive manufacturing where material addition and geometric complexity provide advantages. This resolves the contradiction between weight reduction and manufacturing productivity.

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 provides improved thermal expansion compensation and structural robustness, maintaining clearance and preventing deformation, while offering weight savings and enhanced retention/bonding at material junctions.

Implementation Method 1

the second alloy has a coefficient of thermal expansion at least 10% less than a coefficient of thermal expansion of the first alloy

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS12460551B1Additively manufactured turbine engine case

Publication Date: 2025.11.04 RTX CORP

AI summary

An isogrid structure has a wall having a first face and a second face. An isogrid of hollow ribs is formed on the wall second face. The ribs of the isogrid have respective rib interiors. The wall comprises a first alloy and the ribs comprise a second alloy different from the first alloy. Junctions of the ribs are at bosses having an interior surface open to the rib interiors and an external environment.