Heat Exchanger Bypass Ejector for Aircraft Propulsion
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Solution Overview
Problem
Conventional aircraft turbine engines face challenges in achieving improved engine efficiencies due to the pressure drop across heat exchangers, which reduces propulsive thrust and overall efficiency.
Innovation Solution
The aircraft propulsion system incorporates an ejector that increases the pressure of the exit flow from the heat exchanger using a motive flow taken from the core flow path, thereby matching the pressure of the exhaust gas flow bypassed around the heat exchanger, and directing both flows through a nozzle for enhanced thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a heat exchanger is placed in the exhaust gas flow path to improve engine efficiency, then thermal energy recovery is improved, but pressure drop increases reducing propulsive thrust
Solution Approach 1:
The exhaust gas flow is divided into two separate streams: one portion passes through the heat exchanger for thermal energy recovery, while another portion bypasses the heat exchanger to maintain high pressure for thrust generation. This segmentation allows simultaneous achievement of heat recovery and pressure maintenance.
Solution Approach 2:
An ejector is introduced as an intermediary device that uses a motive flow (taken from the core flow path) to pressurize the low-pressure exit flow from the heat exchanger. The ejector mixes the motive flow with the heat exchanger exit flow, raising its pressure to match the bypassed high-pressure exhaust flow, thereby enabling both heat recovery and thrust maintenance.
2Use of energy by moving object
If exhaust gas flow is directed through a heat exchanger to recover thermal energy, then energy efficiency is improved, but propulsive thrust is reduced due to pressure loss
Solution Approach 1:
The exhaust gas flow is segmented into two paths: one through the heat exchanger for energy recovery and another bypassing it for thrust generation. This allows the system to capture thermal energy while preserving the high-pressure flow needed for propulsive force.
Solution Approach 2:
The ejector acts as a mediator that restores pressure to the heat exchanger exit flow by mixing it with high-pressure motive flow. This pressure restoration enables the recovered thermal energy flow to contribute to propulsive thrust without suffering from the original pressure loss.
3Stress or pressure
If the ejector uses motive flow from the core flow path to pressurize heat exchanger exit flow, then pressure recovery is improved, but engine complexity increases
Solution Approach 1:
The ejector utilizes existing high-pressure motive flow from the core flow path, which would otherwise be wasted or used for other purposes. This multi-functional use of available resources achieves pressure recovery without requiring additional independent compression systems, thereby limiting the increase in engine complexity.
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 configuration compensates for pressure drops across the heat exchanger, enhancing engine efficiency and propulsive thrust by ensuring that the exit flow from the heat exchanger is pressurized to match the bypassed flow, thereby improving overall engine performance.
Implementation Method 1
An ejector is configured to increase a pressure of the exit flow from the heat exchanger with a motive flow taken from the core flow path
Implementation Method 2
A heat exchanger is in communication with a first portion of the exhaust gas flow
Implementation Method 3
an exhaust gas flow that is expanded through a turbine to generate shaft power
Implementation Method 4
a compressor section where an inlet airflow is compressed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An aircraft propulsion system (20) includes a core engine (22) for generating an exhaust gas flow (48) that is expanded through a turbine (42,44) to generate shaft power. A heat exchanger (46) is in communication with a first portion (58) of the exhaust gas flow (48) and an exit flow (50) is emitted from the heat exchanger (46). An ejector (52) is configured to increase a pressure of the exit flow (50) with a motive flow (54) taken from a core flow path (C).