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The On-line Acoustic Sediment Concentration Instrument Developed for Model Yellow River
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Leng Yuanbao，Huang Jiantong and Wang Rui
Yellow River Hydraulics Institute, 45000 ,Shunhe Road 45#, Zhengzhou, Henan Province, China PR.
Abstract: This article briefly introduces the on-line acoustic sediment concentration instrument that developed for “the Model Yellow River”. The instrument is easy to install, use and maintain. It also can collect concentration information on-line. The output signal include RS-232 and/or analog current signal. This information will be transfer to the remote measurement and control system. The key technologies include the High-Speed Acoustic Consistency Sensor, calibration method etc. Keywords : Acoustic, Sediment Concentration, Model Yellow River
1. Background The Yellow River Conservancy Commission (YRCC) proposes a modern concept of “Three Yellow River” (“Prototype Yellow River”, “Model Yellow River” and “Digital Yellow River”). Model Yellow River is an important and irreplaceable part of “Three Yellow River”. Briefly, “the model Yellow River” is the Yellow River in the laboratory. “The model Yellow River” includes four models, i.e. the model of the Loess Plateau, the model of Reservoir, the model of channel and the model of the estuary. “The model Yellow River” reveals the inherent laws of “the Prototype Yellow River” by rehearsal, simulations and experiment of the natural phenomenon reflected from “the Prototype Yellow River”. “The model Yellow River” is used to propose the schemes of harnessing and developing and to offer physics parameters for the construction of “the Digital Yellow River”. [1] The sediment concentration is an important parameter for “the model Yellow River”. During any experiment, technicians must control the sediment concentration of the entry flow and measure the distribution of it. So it is obviously that the sediment concentration instrument is playing an important role in the applications of “the Model Yellow River”. The traditional method to measuring model flow’s sediment concentration is sampling by hand. Obviously, it is inefficient, imprecision and interferential. [2] Since long time ago, technicians all over the world have spent lots of time and fund on developing sediment instruments to replace the traditional manual method and several kinds of new instruments were made. The acoustic, the photoelectric and the isotopic are three main kinds of instruments. However, those instruments have a connatural shortage. The attenuation or dispersion of ultrasonic, ray and radial were affected by many factors including the component and particle diameters. So the measuring results are often incertitude and multiple valued[3]. Further more, all the existing instruments are not made for model use. [4] So the technicians of the Yellow River Hydraulics Institute (YRHR) developed a new on-line acoustic sediment concentration instrument. Some performance parameters are listed in Tab.1. Tab.1 Some Performance Parameters
2. Philosophy of Measurement When ultrasonic is transferring in suspended liquid, energy attenuation will happen. If the solid concentration of the suspended liquid is quite high, electrical and hydrodynamic interactions will happen between the suspended particles especially under the effect of the ultrasonic. Considering the attenuation, the interactions and other relationship, we can find the formula below: [5-6] CS ≈ C1(1+VC/2){1-VC(σ-1-0.7VC1/3)[Ψ2S2+(σ+ψτ-0.7VC1/3)(1+ψτ)]/[2(ΨS)2+(σ+ψτ-0.7 VC1/3)2] 2αS ≈ ωVC(1-VC) (σ+ψτ-0.7VC1/3)2ΨS/ C1[ (ΨS) 2+ (σ+ψτ-0.7 VC1/3)2] C1 =（β1ρ1）-1/2 Ψ = [1-3（6VC/π）1/3/4-（6VC/π）/4] –1 S = 9（1+1/βα）/4βα， τ = 1/2+9/4βα， β=（ρ1ω/2η）1/2 σ= ρ2/ρ1 CS--phase velocity of ultrasonic; αS--absorption coefficient; η-- viscosity coefficient of water β1-- compressibility factor of water; ρ1-- density of water; ρ2-- density of suspended particle; ω-- angular frequency of ultrasonic; VC-- volume concentration of suspended particle; α-- radii of suspended particle;
3. Key Technology 3.1 Sensor The sensor of this instrument is named High-Speed Acoustic Consistency Sensor (HSAC), a production of National “the 8th five-year plan”. Some parameters of the sensor are listed in Tab.1, compared with two kinds of import sensors. Tab.2 Compare between HSAC, MC-1200 & ZMSM400
From the compare we can conclude that the performance of HSAC is better than MC-1200 and ZMSM400, especially the Repeatability Precision and Repeatability Precision.
3.2 Calibration Calibration is a most important step before the instrument is brought into action. Calibration is completed in different situation. During the calibration, the specimen machine was fixed on a test-bed which simulated the real operational environment. The test-bed includes mixing pool, circulating piping and pumps etc. During the calibration, water and model material were mixed in mixing pool. The mixed liquor was send into circulating piping by pumps and passed the specimen machine and was measured. At the same time, the mixed liquor was manually sampled. The concentration of the samples was calculated and compared with the data that measured by the specimen machine. The concentration of the mixed liquor was from nearly 0kg/m3 to 800kg/m3.After experiments, lots of calibration curves were gained. Those curves indicated the relationship between instrument reading and concentration. Fig.1 is one of those curves.
3.3 Suppress Interference Acoustic theories indicate that the attenuation of ultrasonic is correlative with the particle diameter. And ray is much more hypersensitive than ultrasonic. So, how about this new acoustic sediment concentration instrument? Is it susceptible or is it suitable to measure the model flow? The particle diameter of model material is between 10μ to 30μ and average particle diameter is 17μ. The results of calibration indicate that the measuring data is steady. The bubbles are another fatal influential factor. The bubbles in mixed liquor will result in the aberrance of measuring data. This is the problem that all kind of acoustic instrument must face. Analogously, dry model material will also affect the measuring result. In order to avoid the effect, the mixed liquor should be beating up continuously to reduce the bubbles and dry model material.
4. Conclusion Today, measuring instruments are becoming more and more automated and accurate. This is irreversible. Automated instruments can complete the measuring mission more quickly, more efficiently and more intelligently. The acoustic sediment concentration instrument has been installed on the Xiaolangdi Reservoir Model and has finished the test-run. The performance of the instrument is satisfied and it has been an organic part of the Model Yellow River Measurement and Control System.
References Zhu Qingping. A Summary of ” Model Yellow River” Project Planning [J]. People’s Yellow River. 2004. 3:1-3. Jia Chunguan, Tang Maoguan. Study on utilizing ultra sonic for measurement of sediment concentration distribution [J]. Journal of Sediment Research. 1998 (1). Ren Yumin, An Fengling, Zhan Xiuling. The Infrared Silt Meter and its Application. Experiment Technologies and Management. 1999. Vol.16. No.3. New surveying equipment and techniques hydraulics research finds a way through the mud， D+PC, 2/90. Sun chengwei , Research for Acoustic property of high concentration suspended fluid , acoustic technology,1983.volume2,issue1. Chen jiaqin, Zhang nianfang, Yuan yizhi. Pattern and calculation of hanging-rope in uniform flow.
Source: www.yellowriver.gov.cn Editor:HuangFeng
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