Offset Core Nacelle Layout for Exhaust Heat Recovery and Steam Injection
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Solution Overview
Problem
Existing aircraft propulsion systems lose significant heat energy in exhaust gases, and existing heat exchangers are inefficient due to their large size relative to the engine, limiting the recovery of heat energy for steam generation and increasing engine efficiency.
Innovation Solution
An aircraft propulsion system with an offset gas generating core engine and nacelle-mounted heat exchangers, including a steam injection system to increase power output and intercooling, along with large flow-facing areas for heat exchangers within the nacelle to enhance thermal communication and space utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heat exchangers are made large to capture heat energy efficiently, then heat recovery efficiency is improved, but the heat exchanger size becomes large relative to the engine
Solution Approach 1:
The heat exchangers are nested within the engine nacelle structure, utilizing the available internal space of the stationary nacelle to accommodate large heat exchanger surfaces without increasing the overall engine footprint. This allows efficient heat recovery while maintaining compact engine dimensions.
Solution Approach 2:
The heat exchangers are positioned in the radial direction within the nacelle, extending outward from the core engine axis. This radial arrangement allows the heat exchangers to access the large surface area of the nacelle walls, effectively utilizing the nacelle's volumetric space to achieve large heat transfer areas without increasing engine length or diameter.
2Productivity
If steam injection is used to increase mass flow and efficiency, then engine efficiency is improved, but system complexity increases
Solution Approach 1:
The system uses the engine's own exhaust heat to generate steam, which is then injected back into the core flow. This self-contained steam cycle eliminates the need for external steam generation systems, reducing overall system complexity while maintaining the efficiency benefits of steam injection.
Solution Approach 2:
The system recovers waste heat from the exhaust gases that would otherwise be discarded, using it to generate steam for injection. This transforms a harmful waste product into a useful resource, improving efficiency without requiring additional energy input or complex external systems.
3Area of stationary object
If core engine size is reduced to free space for heat exchangers, then space for heat exchangers is improved, but engine power output may be reduced
Solution Approach 1:
The heat exchanger function is extracted from the core engine structure and placed in the nacelle. This separation allows the core engine to be optimized for power generation with minimal size, while the nacelle provides the space for large heat exchangers. The offset core configuration further enables this extraction by creating space in the nacelle for heat exchanger installation.
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 system achieves increased engine efficiency and power output by recovering heat energy for steam generation, reducing the core engine size, and providing additional space for larger heat exchangers, thereby enhancing overall system performance.
Implementation Method 1
Some heat energy may be recaptured and used to generate a steam flow that is injected into the core flow
Implementation Method 2
Efficient heat exchangers for capturing heat and generating steam have large flow facing areas
Implementation Method 3
The steam flow increases engine efficiencies by increasing mass flow without additional work required by the compressor section
Implementation Method 4
An offset core with side ejector nacelle nozzles... large flow-facing areas for heat exchangers within the nacelle to enhance thermal communication
Data Source
Figure 1
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Figure 4
AI summary
A propulsion system (20) for an aircraft includes a fan (22), a core engine (24) configured for generating a gas flow (36) utilized to generate shaft power for driving the fan (22), a nacelle (48) that surrounds the core engine (24) and the fan (22), a condenser (58) where water in the gas flow (36) is condensed into a liquid form, an exhaust duct assembly (52) where the gas flow (36) is directed to the condenser (58), an ejector duct (60) where a portion of a bypass airflow (38) is thermally communicated with the condenser (58) to cool the gas flow (36), and an evaporator assembly (54), that is in thermal communication with the exhaust duct (60), where water recovered by the condenser (58) is heated to generate a steam flow (56) that is subsequently communicated to the core engine (24).