Jingjun Deng
Chinese Academy of Sciences
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Featured researches published by Jingjun Deng.
Ultrasonics Sonochemistry | 2014
Lixin Bai; Weilin Xu; Jingjun Deng; Chao Li; Delong Xu; Yandong Gao
The generation and control of acoustic cavitation structure are a prerequisite for application of cavitation in the field of ultrasonic sonochemistry and ultrasonic cleaning. The generation and control of several typical acoustic cavitation structures (conical bubble structure, smoker, acoustic Lichtenberg figure, tailing bubble structure, jet-induced bubble structures) in a 20-50 kHz ultrasonic field are investigated. Cavitation bubbles tend to move along the direction of pressure drop in the region in front of radiating surface, which are the premise and the foundation of some strong acoustic cavitation structure formation. The nuclei source of above-mentioned acoustic cavitation structures is analyzed. The relationship and mutual transformation of these acoustic cavitation structures are discussed.
Ultrasonics Sonochemistry | 2014
Lixin Bai; Jingjun Deng; Chao Li; Delong Xu; Weilin Xu
High-density controllable bubble structures are produced in the vicinity of radiating surface by artificially implant nuclei. Two kinds of typical cavitation structures produced by artificially implant nuclei are investigated. The focusing action and the physical origin of jet-induced cone-like bubble structure are analyzed. The sonochemical activity of cavitation structures is measured by using the standard method of potassium iodide dosimetry. The controllability of cavitation bubble cluster in the acoustic field is also discussed in this work.
Ultrasonics Sonochemistry | 2012
Lixin Bai; ChongFu Ying; Chao Li; Jingjun Deng
The structures and evolution of Smoker in a 20 kHz ultrasonic field were investigated experimentally with high-speed photography. The spine-plume structure of Smoker was discovered. A few large bubbles align themselves along the central line and form the spine of Smoker. Numerous small bubbles move towards the spine and form the plume structures. The size of large bubbles differs almost by an order of magnitude from that of small bubbles. The evolution of cavitation structure from Flare to Smoker was found. When a Flare appears near a Smoker, the Flare may merge into the plume structures of the Smoker, or form a double-tipped Smoker. A double-tipped Smoker seldom splits into two Smokers, while two separate Smokers tend to merge as one. The large bubbles (or dense plume structures) in the middle part of the two separate Smokers attract each other, driving the two Smokers to bend towards each other and merge.
Proceedings of Meetings on Acoustics | 2017
Delong Xu; Chao Li; Jingjun Deng; Weijun Lin; Lixin Bai
The high temperature, high pressure and high density inside a collapsed acoustic bubble are the mechanisms and the foundation of sonication in liquid. The development of acoustic cavitation in theory and in experiment is reviewed briefly from the first stage of the 20th century. The bottleneck problem of sonication in liquid on the industry scale is analyzed emphatically and up to now, it is still unsolved. In this paper, optimizing the spatial distribution of acoustic cavitation is investigated to overcome the bottleneck. The experiments show that it is feasible. Based on the experiments, an ultrasonic batch processing prototype of 10kW for reducing the viscosity of heavy crude oil is designed and developed. A pilot test is done in the oil field in the northwest of China. The pilot test shows that it can be used to reduce the viscosity of heavy crude oil for the practical production and transportation on the industrial scale. At last, the perspective of the acoustic processing is discussed.
Journal of the Acoustical Society of America | 2016
Delong Xu; Weijun Lin; Jingjun Deng; Chao Li; Lixin Bai; Yan Yang
With the global economical development, high pour point crude oil (HPPCO) is getting more and more attentions. Due to its higher pour point and worse fluidity when it is cold, more difficulties are faced for its extraction. Ultrasonic wave technology is investigated to reduce the pour point of Sudan HPPCO in this paper. First, an ultrasonic horn is proposed and made. Then, after processing for 3 min by the horn, a decrease of more than 3 of the pour point of Sudan HPPCO is obtained. Furthermore, compared with that without ultrasonic processing, the percentage of higher molecular weight constituents becomes more, while that of heavier molecular weight component is less. The mechanism that the pour point of HPPCO can be changed through ultrasonic processing is analyzed and investigated by an experiment that three types of paraffin wax whose molecular weights are different are processed by ultrasonic wave. The main advantage of the ultrasonic processing for HPPCO is economical and environmental and the decre...
Journal of the Acoustical Society of America | 2016
Lixin Bai; Weijun Lin; Jingjun Deng; Chao Li; Delong Xu; Pengfei Wu; Lishuo Chen
The cavitation bubble distribution (cavitation structure) is spatially inhomogeneous in ultrasonic field. A quasi-emulsion phenomenon of cavitation structure is reported in this paper. The inception process of cavitation bubble cloud in a thin liquid layer (the thin liquid layer is trapped between a radiating surface and a hard reflector) was investigated experimentally with high-speed photography. It is revealed that cavitation bubble cloud can be considered as a uniform fluid (cloud), and water without cavitation can be considered as another uniform fluid (water). The conversion from cloud-in-water emulsion to water-in-cloud emulsion occurs with the increase in the number of bubbles. The formation and stability of cloud-water emulsions is analyzed theoretically. It is found that surface tension of cavitation bubble cloud played a leading role. Findings of this research proved that cavitation bubble clusters can be considered and investigated as a whole. [This work was supported by the National Natural S...
internaltional ultrasonics symposium | 2015
Delong Xu; Jingjun Deng; Weijun Lin; Chao Li; Lixin Bai
Due to the shortage of the fossil fuel and with the increasing demand for it, heavy crude oil and ultra heavy crude oil whose density is less than 10API and 20API respectively are getting more attentions in the world. But their properties of heavier density, higher viscosity, and worse fluidity make it very difficult to produce and transport them. Ultrasonic wave technique is investigated to improve their rheological properties in lab and in the field in this paper. In lab, the viscosity of the emulsion of ultra heavy crude oil, water and viscosity reducer processed by ultrasonic wave has a more than 25% decrease of viscosity reduction and 20% less quantity of active macromolecule viscosity reducer is needed. When the initial temperature in not lower than 40°C, the uniformly-distributed emulsion can form when it is subjected to 10-30s ultrasonic irradiation. The mechanisms of effects of high intensity ultrasonic wave on the viscosity reduction are emphatically investigated. According to the experiments, an ultrasonic batch processing system with 4 ultrasonic horns whose basic frequency is 17 kHz is designed and installed in the Xinjiang oil field in the northwest of China. The pilots show that this system can be used to reduce the viscosity of ultra heavy crude oil for the practical production and transportation on the industrial scale.
Scientia Sinica Physica, Mechanica & Astronomica | 2012
Chao Li; ChongFu Ying; Lixin Bai; Jingjun Deng
In the present work,the cavitation bubble cloud and cavitation noise in the contraction-divergence channel have been investigated.With increasing the liquid speed,the bubbles state changes from discrete cavitation cloud to continuous cavitation cloud and the cavitation noise spectrum with broad peak changed to continuous spectrum.The central frequency and value of the peak in the noise spectrum changed with the liquid speed increasing.The integral of the cavitation noise spectrum in [0-50 kHz] shows that the integral valve increased sharply with the liquid speed increasing,and it can indicate the cavitation intensity.There are two kinds of cavitation situation,just like the acoustic cavitation which includes transient cavitation and stable cavitation.
Journal of the Acoustical Society of America | 2012
Chao Li; Jingjun Deng; Lixin Bai
The jet-edge system using a vibrating element (liquid whistle) was investigated experimental using high-speed camera. The vibrating element vibrated periodically with a few millimeters displacement and cavitaion bubbles were observed near the tip of the vibrating element. The acoustic emission of the system was measured with hydrophones in some place. The low frequency and shock signals were observed in the pressure signal, and whistle can be heard at the same time. In frequency field, the line and broadband spectrum exist. The foundation frequency f0 of the vibrating element and harmonics compose the line spectrum. The former 10 order harmonics can be seen obviously. As the flow velocity increasing, the frequency f0 and the harmonic do not change, but the intensity of the high order harmonics and broadband spectrum become strong. Base the experimental result, we consider that the f0 is the foundation frequency of the vibrating element, and the harmonics and the continuous spectrum is the bubble cavitatio...
Journal of the Acoustical Society of America | 2012
Lixin Bai; Jingjun Deng; Chao Li
Temporal evolution and spatial distribution of acoustic cavitation structures induced by a liquid jet in a 20 kHz ultrasonic field were investigated experimentally with high-speed photography. It is revealed that a large-scale flare structure is produced by a liquid jet shooting towards a transducer radiating surface. A few large bubbles and numerous small bubbles are formed on the interface of liquid jet. The size of large bubbles differs almost by an order of magnitude from that of small bubbles. The flare structure hits the radiating surface, spread and adhere. The liquid jet is arrested and a thin bubbly layer lying at the radiating surface is formed. The cavitation cloud will evolve from one structure to another without the interference of liquid jet. (a) Most bubbles move towards the center, and the bubbly layer will become thicker at the centre than at the periphery like a lens. (b) Large bubbles accumulate at the center and skip off the surface, and the lens structure becomes a conical structure. (c) Large bubbles align themselves along the axial line, and the conical structure becomes a fishbone structure. Many other interesting phenomena were observed. The liquid-jet method is useful for the investigation of cavitation structure. This work is supported by the National Natural Science Foundation of China (Grant No. 11174315) and the National Science and Technology Major Project of China (Grant No. 2011ZX05032-003).