Optical Steam Quality Measurement via Interference Fringes
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Solution Overview
Problem
Current methods for measuring steam quality in steam systems are inaccurate, particularly for two-phase steam, and fail to provide real-time, reliable data, leading to inefficiencies in heat transfer, equipment damage, and safety issues due to low steam quality.
Innovation Solution
An optical monitoring and measurement system using two coherent light beams intersecting at a specific angle, with detectors positioned off-axis to capture interference fringes, allowing for the determination of water droplet velocity, size, and shape, and subsequently, steam quality, through Phase Doppler Anemometry and Laser Doppler Velocimetry techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement methods (temperature, pressure, single-phase flow) are used, then measurements can be accurately derived, but they do not give accurate quality measurements for two-phase steam
Solution Approach 1:
The patent replaces traditional mechanical measurement methods (temperature, pressure, flow sensors) with an optical measurement system. The system uses coherent light beams that interact with water droplets in steam, employing optical phenomena (refraction, interference, Doppler effect) to measure steam quality. This substitution enables accurate two-phase steam measurement where mechanical methods fail, as the optical system can distinguish between vapor and liquid phases through light scattering and refraction patterns.
2Measurement precision
If a throttling calorimeter is used for steam quality measurement, then it is useful for certain measurements, but it is not suitable for wet steam or high pressures
Solution Approach 1:
The patent changes the measurement parameters from thermal-based (calorimeter temperature changes) to optical-based (light beam refraction, scattering, and Doppler shift). This parameter change allows the system to operate in conditions where thermal methods fail - specifically wet steam where liquid water droplets are present and high pressure conditions. The optical parameters (wavelength, intensity, phase) remain stable and measurable across these varying conditions, providing universal adaptability.
3Measurement precision
If flow meter and Bernoulli's principle are used, then volumetric flow rates can be calculated, but the method is not accurate and has issues of clogging and deposition
Solution Approach 1:
The patent replaces mechanical flow measurement devices (flow meters with moving parts or restrictive elements) with a non-contact optical measurement system. Coherent light beams pass through the steam flow without physical interaction, eliminating clogging and deposition issues entirely. The system measures flow characteristics through optical Doppler shifts and light scattering patterns, providing both accuracy and operational reliability in harsh steam environments.
4Measurement precision
If mass flow calculations are used by measuring BFW flow rate and dividing by blow down flow rate, then steam quality can be estimated, but the method is not accurate and does not indicate steam quality in each pass of the boiler
Solution Approach 1:
The patent divides the boiler steam generation process into discrete measurement zones corresponding to different passes. Multiple optical measurement points are positioned throughout the boiler, each providing independent steam quality data for its specific location. This segmentation transforms the single aggregate mass flow calculation into distributed, location-specific measurements, preserving information about steam quality variations in each boiler pass and enabling targeted process optimization.
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 system provides accurate, real-time measurements of steam quality, enabling effective control and improving the efficiency and safety of steam systems by overcoming limitations of existing methods.
Implementation Method 1
an emitter for launching two coherent light beams toward a convergence point within the internal volume
Implementation Method 2
a receiver for receiving a signal resulting from interference in space of light from the two coherent light beams after refraction from a droplet in the steam
Implementation Method 3
through Phase Doppler Anemometry and Laser Doppler Velocimetry techniques
Data Source
AI summary
A system and method for controlling steam based on a determination of steam quality include a steam conduit defining an interior volume of steam, an emitter for first and second coherent light beams, a receiver for signals resulting from an interference pattern of the first and second coherent light beams after refraction from a droplet in the steam at a convergence point, and a processor to determine steam quality based on the signals. There can be more than one receiver to account for phase differences related to droplet shape and size. The steam quality is also assessed by measuring droplet velocity by frequency of the interference patterns, and steam vapor and the refraction element of the scattering from the liquid droplet by absorption spectroscopy. The system can be utilized with on-line and real time measurements for on-line and real time determinations of steam quality.