Air Cycle Machine Bypass Duct for Self-Starting

Solution Overview

Problem

Environmental control systems for aircraft face reduced self-starting capabilities due to pressure drops caused by additional components like heat exchangers, which decrease the drive torque needed to overcome frictional drag in air cycle machines.

Innovation Solution

Incorporating a bypass duct and check valve system that diverts airflow around heat exchangers when starting, using a check valve to open the bypass duct when compressor inlet pressure is higher than turbine inlet pressure, thereby increasing drive torque by maintaining higher air pressure at the turbine inlet.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If additional components (heat exchangers) are added to the environmental control system, then the system's functionality and versatility are improved, but the pressure drop increases and drive torque decreases

Engineering Contradiction:

Improvesystem functionalityVSAvoiddrive torque

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The system is divided into two separate airflow paths: a primary path through the heat exchangers and a secondary bypass path. This segmentation allows the system to route air differently based on operational needs, enabling the air cycle machine to start and operate without requiring high pressure drops through all components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A bypass duct acts as an intermediary element that provides an alternative pathway for airflow. This intermediary structure allows air to circumvent the heat exchangers during startup, preventing excessive pressure drops and maintaining sufficient drive torque for the air cycle machine to overcome frictional drag.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If additional components (heat exchangers) are added to the environmental control system, then the system's functionality is improved, but the pressure drop increases

Engineering Contradiction:

Improvesystem functionalityVSAvoidinlet pressure

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The system is divided into two separate airflow paths: a primary path through the heat exchangers and a secondary bypass path. This segmentation allows the system to route air differently based on operational needs, enabling the air cycle machine to start and operate without requiring high pressure drops through all components.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A bypass duct acts as an intermediary element that provides an alternative pathway for airflow. This intermediary structure allows air to circumvent the heat exchangers during startup, preventing excessive pressure drops and maintaining sufficient drive torque for the air cycle machine to overcome frictional drag.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the air cycle machine uses self-starting capability, then the system's simplicity and reliability are improved, but the drive torque must overcome frictional drag without external assist features

Engineering Contradiction:

Improveself-starting capabilityVSAvoiddrive torque

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The bypass duct and check valve system performs a preliminary action during startup by routing air through the bypass path before the air cycle machine reaches full operating speed. This preliminary airflow path reduces pressure drops and builds sufficient drive torque to overcome frictional drag in the bearings and seals, enabling successful self-starting without external assist features.

Inventive Principle:

Principle #10Preliminary action

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 the air cycle machine can self-start without additional assist features by maintaining sufficient drive torque to overcome frictional drag, even with multiple heat exchangers, enhancing the system's ability to condition air for aircraft cabins.

Implementation Method 1

The check valve opens the first bypass duct when an air pressure in the compressor inlet is higher than an air pressure in the first turbine inlet

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Data Source

PatentUS12110900B2Air cycle machine bypass duct

Publication Date: 2024.10.08 HAMILTON SUNDSTRAND CORP

AI summary

An environmental control system includes a rotary machine, a first bypass duct, and a first check valve in the first bypass duct. The rotary machine includes a compressor section and a first turbine section. Each section of the rotary machine includes an inlet, an outlet, a duct extending between the inlet and the outlet, and an impeller in the duct. The rotary machine also includes a tie rod mechanically connecting the compressor impeller and the first turbine impeller. The first bypass duct is between the compressor section and the first turbine inlet. The check valve opens the first bypass duct when an air pressure in the compressor inlet is higher than an air pressure in the first turbine inlet.