Combined Turbojet Ramjet Engine Using Liquid Hydrogen
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Solution Overview
Problem
Existing combined turbojet and ramjet engines face issues with the use of liquid oxygen, which increases safety concerns and on-board weight, and suffer from suboptimal turbine operation and degraded combustion due to hydrogen cooling, leading to inefficiencies and structural stress.
Innovation Solution
A combined turbojet and ramjet engine design that uses only liquid hydrogen, featuring a turbopump with a subsonic turbine driving a supersonic turbine to power the engine, with hydrogen injected directly into the combustion chamber for ramjet operation, eliminating the need for liquid oxygen and optimizing turbine performance by removing cooling heat exchangers and using regenerative heat exchangers for energy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If liquid oxygen is used in the gas generator cycle, then the engine can operate as a turbojet, but the on-board weight increases and safety concerns arise
Solution Approach 1:
The invention extracts and removes liquid oxygen from the system by using atmospheric air as the oxidizer instead. The engine uses only liquid hydrogen as propellant, eliminating the need for liquid oxygen storage tanks and handling systems, thereby reducing weight and safety concerns while maintaining turbojet operation capability through air intake during flight
Solution Approach 2:
The invention introduces atmospheric air as an intermediary oxidizer source. Instead of carrying oxidizer onboard, the engine uses the atmosphere as the oxygen source during turbojet operation, with the air inlet and compressor system serving as the intermediary mechanism to capture and process atmospheric oxygen
2Temperature
If hydrogen cooling is applied to turbine blades, then thermal protection is achieved, but combustion is degraded
Solution Approach 1:
The invention extracts and removes the hydrogen cooling system from the turbine blade structure. Instead of injecting hydrogen through the turbine blades for cooling, the design uses thermal barrier coatings and alternative cooling methods that do not involve hydrogen injection, thereby eliminating combustion degradation while maintaining thermal protection
Solution Approach 2:
The invention replaces the reusable hydrogen cooling system with thermal barrier coatings that can be applied as a protective layer. This approach uses a sacrificial thermal barrier rather than continuous hydrogen flow, reducing complexity and avoiding combustion interference
3Ease of operation
If subsonic turbines are used to drive compressors, then the engine can operate, but turbine performance is suboptimal
Solution Approach 1:
The invention changes the operating parameters of the turbine from subsonic to supersonic flow conditions. The turbine blades are designed with supersonic airfoils and the nozzle system accelerates the hydrogen-oxygen mixture to supersonic speeds before it impinges on the turbine blades, significantly improving turbine efficiency and power output
Solution Approach 2:
The invention introduces dynamic flow control through variable geometry nozzles and adjustable turbine blade angles. The nozzle system can adapt its expansion ratio and the turbine blades can adjust their pitch to optimize performance across different operating conditions, transitioning from static subsonic design to dynamic supersonic operation
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 design reduces weight and complexity, improves performance by eliminating liquid oxygen and optimizing turbine operation, achieving high specific impulse and simplified starting procedures, with operation up to Mach 5 and specific impulse of about 4000 seconds.
Implementation Method 1
a subsonic turbine driving a supersonic turbine
Implementation Method 2
using regenerative heat exchangers for energy delivery
Implementation Method 3
the combustion chamber defined inside the casing downstream from said central body
Data Source
AI summary
A combined engine includes a turbopump including a pump injecting hydrogen into a heater arranged in an outer casing downstream from a central body, and a subsonic turbine driving the pump, which turbine receives partially-expanded hydrogen collected at an outlet from the heater to apply the hydrogen to a supersonic turbine to operate the engine as a turbojet. The hydrogen from the supersonic turbine is collected in tubes inside the central body to be sent to a combustion chamber defined downstream from the central body, while the hydrogen that is partially expanded in the subsonic turbine is sent directly to the combustion chamber via injectors to operate the engine as a ramjet.