Rotorcraft Engine Inlet Plenum Gap Design

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Solution Overview

Problem

Existing rotorcraft inlet systems face challenges with elastomeric seals that are prone to damage, misalignment, and increased complexity due to relative motion between the engine and airframe, leading to inefficiencies and user dissatisfaction.

Innovation Solution

A hard-mounted engine inlet plenum system with a barrier filtration system integrated directly into the plenum assembly, eliminating the need for elastomeric seals and using an engine exhaust ejector to manage airflow, thereby reducing tolerance issues and complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If elastomeric seals are used to accommodate relative motion between engine and airframe, then adaptability is improved, but device complexity and reliability deteriorate due to seal damage and misalignment

Engineering Contradiction:

Improveaccommodation of relative motionVSAvoidseal integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The invention removes the elastomeric seal from the system entirely. The gap between the plenum inlet and cowl door assembly is left open without any sealing component, eliminating the reliability issues associated with seal damage and misalignment while still accommodating relative motion through the maintained gap.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The inlet system is segmented into distinct components (plenum assembly and cowl door assembly) that are allowed to move independently relative to each other. The gap between these segmented components accommodates their relative motion without requiring a flexible seal to connect them.

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If elastomeric seals are used to prevent foreign object ingress, then protection is improved, but device complexity increases due to additional sealing components

Engineering Contradiction:

Improveforeign object protectionVSAvoidsealing system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The elastomeric seal component is extracted from the system. Foreign object protection is achieved not by sealing the gap but by allowing the gap to remain open while using the engine exhaust ejector effect to manage airflow and prevent foreign object ingress through aerodynamic means rather than mechanical sealing.

Inventive Principle:

Principle #2Taking out (Extraction)

3Adaptability or versatility

If gap is maintained for relative motion, then adaptability is improved, but harmful factors worsen due to potential foreign object ingress

Engineering Contradiction:

Improverelative motion capabilityVSAvoidforeign object ingress risk

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The open gap, which could potentially allow foreign object ingress, is converted into a beneficial feature. The gap allows free relative motion between the plenum assembly and cowl door assembly without constraint, and the aerodynamic flow management through the engine exhaust ejector effect actually helps control what enters through the gap, turning a potential vulnerability into an advantage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

4Device complexity

If hard-mounted plenum system is used, then device complexity is reduced, but manufacturing precision requirements increase due to alignment tolerances

Engineering Contradiction:

Improveinlet system complexityVSAvoidalignment tolerance

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The design changes the critical parameter from alignment precision to gap dimensioning. Instead of requiring precise alignment between the plenum inlet and cowl door assembly, the system uses a deliberately sized gap that accommodates misalignment and relative motion. This parameter change from precision alignment to tolerance-friendly gap design reduces manufacturing precision requirements.

Inventive Principle:

Principle #35Parameter changes

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 decreases sealing and tolerance issues, simplifies the interface, and improves efficiency by allowing relative motion while preventing foreign object damage, resulting in a more reliable and cost-effective inlet system.

Implementation Method 1

an inlet flange defining an inlet to flow air into a barrier filtration system

Methodology Applied

Scientific EffectFiltration: Filter (physical)

Implementation Method 2

an engine exhaust ejector configured to be connected to the plenum assembly to manage air flow around the gap

Methodology Applied

Scientific EffectEjector effect: Injector

Data Source

PatentUS9574497B2Engine mounted inlet plenum for a rotorcraft

Publication Date: 2017.02.21 TEXTRON INNOVATIONS INC

AI summary

One example of an engine mounted inlet plenum for a rotorcraft includes an inlet flange, an outlet flange and a plenum duct that connects the inlet flange and the outlet flange. The inlet flange, which defines an inlet to flow air into a barrier filtration system, is configured to be substantially aligned with a closed cowl door assembly of the rotorcraft. In some implementations, the plenum duct is configured to extend to an outer mold line (OML) of the rotorcraft such that the inlet flange is aligned with the OML. The outlet flange defines an outlet to flow air filtered by the barrier filtration system into an engine of the rotorcraft. The plenum duct allows air to flow from the inlet to the outlet.