NO Flow Tagging Imaging with Single-Laser Hypersonic Fluorescence
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Solution Overview
Problem
Conventional methods for measuring flow parameters in hypersonic flows, such as Molecular Tagging Velocimetry (MTV), Femtosecond Laser Electronic Excitation Tagging (FLEET), and Picosecond Laser Electronic Excitation Tagging (PLEET), face limitations in seeding particles, require multiple lasers, or operate at suboptimal repetition rates, making them unsuitable for unsteady and turbulent flows.
Innovation Solution
The Nitric-oxide Ionization Induced Flow Tagging and Imaging (NiiFTI) technology uses a single sub-millijoule nanosecond laser pulse to resonantly ionize nitric oxide (NO) in hypersonic flows, transferring energy to molecular nitrogen (N2) for long-lasting fluorescence, enabling flow tagging and imaging with a time-gated camera, compatible with commercially available systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Molecular Tagging Velocimetry (MTV) is used for velocity measurements, then non-intrusive velocity measurements can be achieved, but multiple lasers are required increasing device complexity
Solution Approach 1:
The patent extracts the tagging function from the complex multi-laser MTV system and implements it using a single laser pulse that resonantly ionizes nitric oxide, which then transfers energy to molecular nitrogen for fluorescence tagging. This separation of functions allows simplified single-laser operation while maintaining measurement capability.
Solution Approach 2:
Nitric oxide serves as an intermediary substance that mediates between the laser and molecular nitrogen. The laser first ionizes NO, which then transfers energy to N2 molecules, enabling indirect tagging of the flow without requiring direct laser excitation of nitrogen, thus simplifying the laser requirements.
2Device complexity
If Femtosecond Laser Electronic Excitation Tagging (FLEET) is used for flow tagging, then single laser operation is achieved, but repetition rate is limited to kilohertz rates
Solution Approach 1:
The patent changes the fundamental parameters of the tagging process by using resonant ionization of nitric oxide followed by energy transfer to nitrogen, rather than direct electronic excitation. This parameter change enables operation at higher repetition rates while maintaining single-laser operation, as the ionization process can be rapidly repeated without the limitations of traditional FLEET.
3Productivity
If Picosecond Laser Electronic Excitation Tagging (PLEET) is used for flow tagging, then high repetition rates are achieved, but flow tagging effectiveness is reduced
Solution Approach 1:
By introducing nitric oxide as an intermediary that efficiently absorbs laser energy and transfers it to molecular nitrogen, the patent achieves both high repetition rates and effective flow tagging. The NO molecule acts as an energy bridge that enables rapid repeated excitation while maintaining strong fluorescent signal for effective tagging.
4Productivity
If Krypton Tagging Velocimetry (KTV) is used for flow tagging, then 100 kHz repetition rate is achieved, but krypton seeding and high-power narrow-linewidth ultraviolet laser are required
Solution Approach 1:
The patent replaces expensive krypton gas seeding and high-power narrow-linewidth ultraviolet lasers with a simpler system using nitric oxide (naturally present in hypersonic flows) and standard nanosecond laser pulses. This substitution maintains high repetition rate capability while dramatically reducing device complexity and cost.
Solution Approach 2:
Nitric oxide serves as a readily available intermediary in hypersonic flows that enables the tagging process without requiring expensive krypton seeding. The resonant ionization of NO provides an efficient energy transfer pathway to nitrogen molecules, achieving effective tagging with simpler, more accessible equipment.
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
NiiFTI allows for precise flow property measurements, including velocity and vorticity, with high repetition rates and simplified setup, suitable for supersonic and hypersonic environments, reducing complexity and enhancing measurement accuracy.
Implementation Method 1
resonantly ionize nitric oxide (NO) in hypersonic flows, transferring energy to molecular nitrogen (N2) for long-lasting fluorescence
Implementation Method 2
energy transfer processes from 'one plus one' two-photon resonantly ionized nitric oxide (NO) to electronically excited molecular nitrogen (N2)
Implementation Method 3
subsequent long 'red' phosphorescence
Implementation Method 4
The first positive fluorescence from molecular nitrogen lasts on the order of 10 s-100 s of microseconds in air
Implementation Method 5
tracking of the 'written' pattern with a time-gated camera
Data Source
AI summary
Nitric-oxide ionization induced flow tagging and imaging (NiiFTI) is described. In one embodiment a method for characterizing a flow of a gas containing an agent includes ionizing the agent by a source of pulsed light emitting at a frequency overlapping a resonant transition frequency of the agent. In response to ionizing of the agent, a fluorescence of the gas is generated. The method also includes capturing at least one time-delayed image of the flow of the gas, where the capturing is time-delayed with respect to a pulse of the source of pulsed light. The method includes determining at least one property of the flow of the gas by analyzing the at least one time-delayed image of the flow.