Dual Mode Ramjet Ignition Using Hot Gas Accumulator
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Solution Overview
Problem
Dual mode ramjet and scramjet engines face challenges in restarting after blowout or unstart due to reliance on single-use pyrotechnic devices or high-energy plasma torches, which add complexity, weight, and cost, and require separate cold-start systems.
Innovation Solution
An ignition system that uses a solid propellant gas generator and insulated hot gas accumulator, with a three-way valve to direct hot gas between the engine and accumulator, enabling multiple restarts by storing and re-injecting residual hot gas for ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-use pyrotechnic device is used for engine ignition, then the engine can be started initially, but the engine cannot be restarted after blowout or unstart
Solution Approach 1:
The patent stores hot gas in an accumulator before it is needed for restart. The hot gas is generated during initial engine start and captured in the accumulator, preparing the restart capability in advance without requiring additional ignition devices. This preliminary storage of energy enables reliable restarts while avoiding the complexity of multiple pyrotechnic devices.
2Reliability
If multiple single-use pyrotechnic igniters are used for multiple restarts, then the engine can be restarted multiple times, but the complexity, weight, and cost of the system increase
Solution Approach 1:
The patent combines the ignition function with the exhaust gas handling system. The hot gas accumulator, which would otherwise be waste exhaust, is repurposed as the ignition energy source. This merging of functions eliminates the need for separate multiple pyrotechnic igniters, reducing weight while maintaining multiple restart capability.
Solution Approach 2:
The system uses its own exhaust gas to provide the ignition energy for restarts. The hot gas generated during normal operation or initial start is captured and reused for ignition purposes. This self-service approach eliminates the need for external multiple igniter systems, reducing weight and complexity.
3Reliability
If plasma torch or spark ignition systems are used for multiple restarts, then multiple restarts are possible, but large electrical energy input is required
Solution Approach 1:
The patent converts the hot exhaust gas, which would otherwise be wasted energy, into a useful ignition source. The thermal energy in the exhaust is captured and stored, then reused for ignition. This converts what was previously a harmful waste product into a beneficial resource, eliminating the need for high-energy plasma or spark systems.
Solution Approach 2:
The patent changes the ignition mechanism from electrical (plasma/spark) to thermal (hot gas). By storing hot gas at high temperature and directing it to the combustor, the system achieves ignition through thermal parameters rather than electrical energy input, significantly reducing power requirements.
4Reliability
If a separate cold-start system is used for hydrocarbon-fueled engines, then combustion can be sustained during cold-start, but the overall system complexity increases
Solution Approach 1:
The hot gas accumulator serves multiple functions: it provides ignition energy for initial start, enables multiple restarts after blowout, and supports cold-start operations. This single multi-functional component replaces what would otherwise require separate cold-start and restart systems, reducing overall complexity.
Solution Approach 2:
The system prepares hot gas in advance during initial operation or start, storing it in the accumulator before cold-start or restart is needed. This preliminary preparation eliminates the need for separate cold-start fuel systems, as the stored hot gas provides the necessary thermal energy to initiate and sustain combustion in cold conditions.
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 allows for reliable multiple restarts of dual mode ramjet or scramjet engines without a separate cold-start system, reducing complexity, weight, and power requirements, while maintaining engine operability by using stored hot gas for ignition and preventing lean blowout.
Implementation Method 1
A solid propellant gas generator, ignitable by the squib, produces hot gas
Implementation Method 2
An insulated hot gas accumulator is provided for storing the hot gas
Implementation Method 3
A three-way hot gas valve is in fluid communication with the jet, the solid propellant gas generator, and the insulated hot gas accumulator
Implementation Method 4
The hot gas is used to ignite the jet engine
Data Source
AI summary
An ignition system for a jet includes a squib. A solid propellant gas generator is ignitable by the squib and produces hot gas. An insulated hot gas accumulator is provided for storing the hot gas. A three-way hot gas valve is in fluid communication with the jet, the solid propellant gas generator, and the insulated hot gas accumulator. The three-way hot gas valve has a first condition establishing a first flow path from the solid propellant gas generator to the jet, a second condition establishing a second flow path from the solid propellant gas generator to the insulated hot gas accumulator, and a third condition establishing a third flow path from the insulated hot gas accumulator to the jet.