Variable Flow Diaphragm for Turbojet Afterburner Cooling

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Solution Overview

Problem

Existing afterbody designs for aircraft turbojet engines have inefficient ventilation stream throughput due to a fixed diaphragm flow area, leading to suboptimal cooling in varying operating modes, as the throughput is excessive in modes other than full-throttle with afterburning.

Innovation Solution

A diaphragm-forming assembly with overlapping annular plates, where the thermal protection liner's expansion causes angular and radial displacement of the second plate, increasing the flow area defined by the apertures, allowing adaptive ventilation stream throughput based on temperature levels, eliminating the need for additional actuators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a fixed diaphragm flow area is used to ensure satisfactory cooling under full-throttle with afterburning conditions, then cooling effectiveness is improved, but ventilation stream throughput becomes excessively high in other operating modes leading to suboptimal air management

Engineering Contradiction:

Improveafterburner casing temperatureVSAvoidventilation stream throughput efficiency

Core Design Contradiction:

TemperatureVSProductivity

Solution Approach 1:

The diaphragm flow area is made variable through the relative movement between the first annular plate (fixed to afterburner casing) and the second annular plate (fixed to thermal protection liner). As the thermal protection liner expands thermally during different operating conditions, it moves radially outward, increasing the flow area dynamically to match the cooling requirements of each operating mode.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flow area parameter of the diaphragm is changed dynamically based on thermal expansion of the protection liner. The system automatically adjusts the ventilation stream throughput by varying the flow area according to temperature levels, transitioning from a fixed parameter system to a variable parameter system that adapts to operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the thermal protection liner is constrained to prevent thermal expansion, then structural stability is improved, but the ability to dynamically adjust flow area for optimal cooling in varying operating modes is lost

Engineering Contradiction:

Improvestructural stability of afterbodyVSAvoidadaptability of ventilation stream throughput

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The diaphragm is segmented into two separate annular plates that can move relative to each other. The first plate is fixed to the afterburner casing while the second plate is fixed to the thermal protection liner. This segmentation allows the protection liner to expand thermally without compromising the overall structural stability, as the expansion is accommodated through the relative movement between the two plates rather than constraining the liner itself.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If additional actuators are added to control the diaphragm flow area dynamically, then adaptability of ventilation throughput is improved, but device complexity increases

Engineering Contradiction:

Improveventilation stream throughput adaptabilityVSAvoiddiaphragm control system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system uses the thermal expansion of the protection liner itself as the driving mechanism for adjusting the flow area. The thermal energy from the operating conditions directly drives the relative movement between the two annular plates, eliminating the need for external actuators, motors, or complex control systems. The system is self-regulating based on the thermal state of the afterbody.

Inventive Principle:

Principle #25Self-service

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 solution ensures optimal cooling by increasing ventilation stream throughput during high temperatures and conserving air for other engine sections, improving afterburning performance by adjusting the flow area dynamically with thermal expansion, thus enhancing overall engine efficiency.

Implementation Method 1

the thermal protection liner being mounted on the afterburner casing by way of fastening elements which are designed to impose a direction of angular displacement on this thermal protection liner with respect to the casing when the liner expands under the effect of thermal stresses

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS7870740B2Turbojet engine comprising an afterburner duct cooled by a variable-throughput ventilation stream

Publication Date: 2011.01.18 SAFRAN AIRCRAFT ENGINES SAS

AI summary

An afterbody for a turbojet engine is disclosed. The afterbody includes an afterburner casing, a thermal protection liner, and a diaphragm-forming assembly interposed between the liner and the casing. The diaphragm-forming assembly defines a flow area which is traversed by a ventilation stream. The diaphragm-forming assembly includes two annular plates overlapping one another, each being perforated with a plurality of apertures and being mounted on the liner and the casing respectively. The apertures jointly define the flow area of the assembly. Furthermore, the assembly is designed such that the expansion of the liner causes an angular displacement of the plate with respect to the plate, leading to an increase in the size of the flow area.