Online Particle Velocity Measurement in Multiphase Reactors
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Solution Overview
Problem
Current methods for measuring particle velocity in multiphase reactors face challenges such as low dynamic response, clogging issues, and complexity in instrument calibration, limiting their effectiveness in capturing high-frequency data and maintaining accuracy in unsteady turbulent fields.
Innovation Solution
An online multiphase measuring instrument combining multiple-exposure techniques and image processing methods, utilizing a package tube with LED lamps, a telecentric lens, and a CMOS or CCD camera, which captures double-exposure images to calculate instantaneous particle velocity with high accuracy by determining valid particles and their centroid coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pitot tube is used for velocity measurement, then the measurement is simple to operate, but the dynamic response frequency is low and cannot record high-frequency pulse information
Solution Approach 1:
The patent replaces the mechanical pitot tube measurement system with an optical measurement system using high-speed camera and image processing. The mechanical probe is substituted by optical fields (light sources and cameras) that capture particle motion without physical contact, thereby achieving high temporal resolution while maintaining ease of operation through automated image analysis.
2Ease of operation
If pitot tube is used for velocity measurement, then the measurement is simple to operate, but high viscosity liquid or fine solid particles will clog the pitot probe
Solution Approach 1:
The patent replaces the mechanical pitot tube probe with a non-contact optical measurement system consisting of light sources and high-speed cameras. This substitution eliminates the physical probe that would clog in high viscosity liquids or fine particle environments, while maintaining measurement capability through optical tracking of particle motion.
3Speed
If hot wire anemometer is used for velocity measurement, then the frequency response is high and sensitivity is large, but the probe and sensor are easily broken in strong vortex containing particles
Solution Approach 1:
The patent replaces the fragile hot wire anemometer probe with a robust optical measurement system. The delicate wire sensor is substituted by solid-state light sources and cameras that can withstand strong vortices and particle-laden environments without breaking, while maintaining high frequency response through high-speed imaging capabilities.
4Reliability
If hot film anemometer is used for velocity measurement, then the probe is solid and wear-resisting, but the frequency response is low
Solution Approach 1:
The patent replaces the hot film anemometer with an optical measurement system using high-speed cameras. This substitution overcomes the low frequency response limitation of hot film technology by using optical tracking that can capture high-frequency particle motion, while maintaining probe durability through non-contact measurement.
5Measurement precision
If LDV is used for velocity measurement, then the precision is high and response is fast, but strict requirements for concentration of measured particles or fluid tracer are needed and complex instrument calibration is required
Solution Approach 1:
The patent extracts the measurement function from complex calibrated instruments to a simpler system using standard high-speed cameras and LED lights. By using naturally occurring or easily added tracer particles with the high-speed imaging system, the patent eliminates the need for complex LDV calibration procedures while maintaining high measurement precision through direct optical tracking.
6Loss of information
If PIV is used for velocity measurement, then the instant information of the whole flow field can be obtained, but PIV technique is usually used only to measure the liquid phase velocity in multiphase flow due to complexity of tracer particles
Solution Approach 1:
The patent applies particle tracking velocimetry that segments and tracks individual particles or bubbles through their centroids in sequential frames. This segmentation approach allows measurement of velocity for different phases (gas bubbles, liquid droplets, solid particles) independently, overcoming the limitation of conventional PIV that averages all particles and cannot distinguish phases in multiphase flows.
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
Enables real-time measurement of particle velocity distribution with low invasive error, achieving accuracy less than 15% as validated by CFD simulation, and can measure bubble, droplet, or solid particle velocities in multiphase reactors.
Implementation Method 1
an illumination system for illuminating multiphase flow, including LED lamps and a brightness-adjustable light source connected with the LED lamps
Implementation Method 2
a photographic system for taking pictures, including a telecentric lens and an image sensor
Data Source
AI summary
The present invention provides an online measuring method of particle (such as bubbles, droplets and solid particles) velocity in multiphase reactor. The method based on an online multiphase measuring instrument includes the following steps: (1) the online multiphase measuring instrument is placed into the multiphase reactor, and then a particle image produced by two or more exposures are obtained; (2) the actual size of individual pixel in the particle image is determined; (3) valid particles are determined in the depth of field; (4) then the centroid coordinates are conversed to the actual length of the coordinates (xt,i, yt,i) and (xt+Δt,i, yt+Δt,i) using the actual size of individual pixel. Thus, the instantaneous velocity of particles can be calculated byVi=(xt+Δt,i-xt,i)2+(yt+Δt,i-yt,i)2Δt.The method can realize real-time measurement of the velocity distribution of bubbles, droplets or solid particles in a multiphase reactor, and the measurement accuracy is high.