IR Flow Velocity Measurement via Cross-Correlation
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Solution Overview
Problem
Existing methods for measuring the flow velocity of gas streams, particularly at high temperatures or with aggressive gases, face challenges in achieving high accuracy due to material limitations and increased wear.
Innovation Solution
A method and device utilizing time-resolved measurement of IR radiation parameters at two points outside the gas stream, calculating transit time via cross-correlation, and determining flow velocity, with IR radiation sensors operating at wavelengths of at least 780 nm and up to 6 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature-resolved measurement is performed inside the gas stream using conventional sensors, then measurement accuracy can be achieved, but material wear and chemical degradation increase significantly at high temperatures
Solution Approach 1:
The patent introduces an intermediary substance (tracer particles or gas) that carries the measurement signal through the harsh environment without being damaged. These tracers are injected into the gas stream and passively transported, allowing measurement of flow velocity without exposing sensors to high temperatures and aggressive conditions.
Solution Approach 2:
The patent replaces direct mechanical/thermal contact measurement with optical measurement. Instead of placing temperature sensors inside the hot gas stream, the system uses optical detectors to measure the movement of tracer particles or gas density variations, eliminating the need for materials to withstand extreme temperatures.
2Measurement precision
If measurement points are placed inside the gas stream for direct measurement, then measurement accuracy improves, but abrasive wear from solid particles increases
Solution Approach 1:
The patent uses tracer particles or gas as an intermediary that is specifically designed to be resistant to abrasive wear. These tracers are mixed with the gas stream and their movement is tracked optically, allowing the measurement system to remain outside the direct path of abrasive particles while still accurately measuring flow velocity.
Solution Approach 2:
The patent replaces direct mechanical measurement (sensors in contact with the gas stream) with optical measurement of tracer particle movement. This substitution eliminates the mechanical wear caused by solid particles, as the optical detection system remains external to the abrasive environment.
3Measurement precision
If conventional temperature measurement methods are used in aggressive gas environments, then measurement can be performed, but measurement uncertainty increases
Solution Approach 1:
The patent introduces tracer particles or gas as an intermediary that enhances the measurement signal. These tracers provide distinct optical characteristics that make them easily distinguishable from the background gas stream, improving the signal-to-noise ratio and reducing measurement uncertainty through techniques like image processing and correlation analysis.
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 approach allows for more accurate measurement of flow velocity with reduced measurement uncertainty, especially effective at high temperatures and in aggressive gas environments.
Implementation Method 1
a first IR radiation sensor for the time-resolved measurement of a first IR radiation parameter of IR radiation of the gas stream
Implementation Method 2
the IR radiation parameter is measured photoelectrically at a wavelength of at least 780 nm, especially 1.5 μm
Data Source
AI summary
The invention relates to a method for measuring a flow velocity (v) of a gas stream (14) featuring the steps: (a) time-resolved measurement of an IR radiation parameter (E) of IR radiation of the gas stream (14) at a first measurement point (P1) outside of the gas stream (14), thereby obtaining a first IR radiation parameter curve (Eg1,1(t)), (b)time-resolved measurement of an IR radiation parameter (E) at a second measurement point (P2) outside of the gas stream (14), thereby obtaining a second IR radiation parameter curve (Eg1,2(t)), (c) calculation of a transit time (τ1) from the first IR radiation parameter curve (Eg1,1(t)) and the second IR radiation parameter curve (Eg1,2(t)), in particular by means of cross-correlation, and (d) calculation of the flow velocity (vG) from the transit time (τ1), (e) wherein the IR radiation parameter (Eg1) is measured photoelectrically at a wavelength (g1) of at least 780 nm, and (f) a measurement frequency (f) is at least 1 kilohertz.