Hybrid Turbojet-Turboprop Engine with Precooler
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Solution Overview
Problem
Existing single-stage to orbit (SSTO) vehicles face challenges in achieving high payload fraction and efficient propulsion due to the need for a high oxidant mass, particularly liquid oxygen, which increases vehicle mass and fuel demands in hybrid aerospace propulsion engines.
Innovation Solution
The engine design incorporates both rocket and air-breathing combustion chambers that can operate independently, using compressed air as an oxidant at lower velocities and switching to onboard oxidants at higher velocities, with a heat exchanger system to manage temperature and fuel delivery systems to optimize fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a rocket engine is used for take-off, then high velocity to achieve orbit can be obtained, but a high payload of oxidant (liquid oxygen) is required which adds considerable mass to the vehicle
Solution Approach 1:
The engine dynamically switches between air-breathing mode at lower velocities and rocket mode at higher velocities. The compressor operates at lower speeds to compress atmospheric oxygen, while the rocket combustion chamber activates at higher speeds when atmospheric oxygen is insufficient. This dynamic operation allows the vehicle to use free atmospheric oxygen during the mass-intensive take-off phase, reducing the need to carry oxidant payload.
Solution Approach 2:
The compressor acts as an intermediary device that captures and compresses atmospheric oxygen during the take-off phase. This compressed oxygen is then supplied to the combustion chamber, serving as a substitute for carrying liquid oxygen payload. The intermediary compressor system enables the vehicle to utilize free atmospheric resources rather than carrying all necessary oxidant from the ground.
2Device complexity
If air is compressed to high pressure (approximately 150bar) for rocket operation, then a common combustion and nozzle system can be employed in both propulsion modes, but the delivery temperature must be kept below 800K which requires significant cooling
Solution Approach 1:
The cooling function is extracted as a separate, dedicated system rather than being integrated into the combustion process itself. A specific cooling subsystem is implemented to remove excess heat from the compressed air before it enters the combustion chamber, allowing the main combustion and nozzle system to remain simple and common to both operating modes.
Solution Approach 2:
A cooling intermediary system is introduced between the compressor and combustion chamber. This intermediary cooling system manages the temperature of the compressed air, ensuring it remains below 800K before entering the combustion chamber, while allowing the combustion and nozzle system to operate independently of the cooling process.
3Use of energy by moving object
If a hybrid engine with both rocket and air-breathing modes is used, then fuel requirements can be reduced, but the engine structure becomes more complex with separate combustion chambers and fuel delivery systems
Solution Approach 1:
The engine is segmented into distinct functional components: a compressor for air-breathing mode and a rocket combustion chamber for rocket mode, with separate fuel delivery systems for each. This segmentation allows each subsystem to be optimized for its specific operating mode, improving overall fuel efficiency while maintaining manageable complexity through modular architecture.
Solution Approach 2:
The engine employs universal elements that serve multiple functions: the nozzle system is common to both air-breathing and rocket modes, and the fuel delivery system is designed to supply both the compressor and rocket combustion chamber. This multi-functionality reduces the need for completely separate systems, balancing the benefits of hybrid operation with controlled structural 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 reduces fuel requirements, allows for efficient take-off using air, and transitions seamlessly between air-breathing and rocket modes, enhancing the vehicle's payload capacity and reducing maintenance needs.
Implementation Method 1
the delivery temperature must be kept within practical limits (below 800K) and to minimize the compressor work required
Implementation Method 2
a rocket combustion chamber for the combustion of fuel and oxidant; an air-breathing combustion chamber for the combustion of fuel and oxidant
Data Source
Figure 1A~1C
Figure 2
Figure 3
AI summary
The present disclosure relates to an engine having two modes of operation— air breathing and rocket— that may be used in aerospace applications such as in an aircraft, flying machine, or aerospace vehicle. The engine's efficiency can be maximized by using a precooler arrangement to cool intake air in air breathing mode using cold fuel delivery systems used for the rocket mode. By introducing the precooler and certain other engine cycle components, and arranging and operating them as described, problems such as those associated with higher fuel and weight requirements and frost formation can be alleviated.