Multi-nozzle Flow Diverter for Jet Engine Third Stream
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Solution Overview
Problem
Variable cycle aircraft engines face issues with the third air stream duct experiencing pressure drops due to heat exchanger placement, leading to cessation or reduction of airflow, especially at high power operations and low Mach points, resulting in potential stall conditions and hardware damage.
Innovation Solution
A flow diverter valve is introduced in the third duct to direct the third air stream to either the primary nozzle or a secondary nozzle, ensuring continuous airflow and optimizing thrust generation, while also providing cooling to heat exchangers and reducing inlet distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat exchangers are placed within the third air stream duct to utilize low temperatures, then cooling capability is improved, but pressure drop increases leading to airflow cessation or reduction
Solution Approach 1:
A flow diverter valve is introduced as an intermediary device in the third air stream duct to control and regulate airflow. The valve mediates between the heat exchanger requirements and the need to maintain sufficient airflow pressure, preventing cessation or reduction of air flow while still enabling effective cooling operation.
Solution Approach 2:
The flow diverter valve dynamically adjusts airflow parameters (flow rate, pressure distribution) based on operating conditions. By changing these parameters, the system can maintain adequate airflow pressure even when heat exchangers are installed, resolving the contradiction between cooling effectiveness and airflow quantity.
2Productivity
If the third stream air pressure is low (at low Mach points), then inlet efficiency is improved, but the ability to exhaust air through the duct is reduced due to insufficient pressure differential
Solution Approach 1:
The flow diverter valve acts as a mediator that actively manages pressure distribution in the third air stream duct. Even when inlet pressure is low, the valve can regulate flow to maintain sufficient velocity for effective exhaust, decoupling the direct relationship between inlet pressure and exhaust capability.
Solution Approach 2:
The flow diverter valve provides dynamic control over airflow characteristics, allowing the system to adapt to varying pressure conditions. The valve can adjust its position or opening to optimize airflow velocity and pressure differential across different operating regimes, maintaining effectiveness despite low inlet pressure at certain Mach numbers.
3Reliability
If a flow diverter valve is added to control third air stream flow, then airflow stability and thrust optimization are improved, but device complexity increases
Solution Approach 1:
The flow diverter valve is a relatively simple intermediary component that provides significant control benefits. Rather than redesigning the entire duct system, this single valve component delivers airflow stability and thrust optimization, representing a cost-effective solution to the complexity problem.
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 diverter valve ensures continuous airflow in the third stream duct, enhances thrust generation, extends hardware life, and improves engine efficiency by maintaining stable airflow and reducing stall margins, even at low pressure conditions.
Implementation Method 1
The flow diverter valve directs the third air stream to either the primary nozzle or to a secondary nozzle
Implementation Method 2
This third stream of air is pressurized by a blade-on-fan arrangement
Implementation Method 3
placement of heat exchangers within the third air stream in recent embodiments to take advantage of the low temperatures of the air flowing in the third stream duct
Data Source
AI summary
An exhaust system for a variable cycle aircraft engine. The exhaust system comprises a core exhaust for bypass air and hot gases of combustion. The core exhaust includes a convergent-divergent nozzle. The convergent-divergent nozzle is formed from a plurality of flaps and seals. The exhaust system comprises a third air duct for a third stream of air. The third stream of air is selectively exhausted from the third duct through a secondary nozzle or divergent slots in the convergent-divergent nozzle, or both depending upon the flight mode. A diverter valve is positioned in the third stream duct to selectively control the flow of third stream air through the secondary nozzle, the divergent slots and combinations thereof.