共查询到20条相似文献，搜索用时 31 毫秒
1.
Based on the comprehensive forces balance model,a modified model of the formation of a single bubble in non-Newtonian fluid under constant flowrate was developed by taking account of the effect of the ingoing gas through orifice as well as its variation OH the radial expansion of bubble.The modified model involves the radial expansion equation of bubble surface and the forces balance equation in vertical direction of the bubble respectively.The shape variation of bubbles formed in polyacrylamide(PAM)aqueous solutions under various conditions was predicted numerically.The practical formation of bubbles was real-time visualized and recorded by a CCD camera and a computer by means of a special laser image measurement system.Results show that the predicted shapes of the bubbles by the present model agree well with experimental observation. 相似文献
2.
Ｔｈｅａｃｃｕｒａｔｅｍｅａｓｕｒｅｍｅｎｔｏｆｔｈｅｇａｓ ｌｉｑｕｉｄｉｎｔｅｒｆａ ｃｉａｌａｒｅａｓｉｓｏｆｇｒｅａｔｉｍｐｏｒｔａｎｃｅｔｏｅｓｔｉｍａｔｅｒｅｌｉａｂｌｙｔｈｅｔｒａｙｅｆｆｉｃｉｅｎｃｉｅｓａｎｄｏｐｔｉｍｉｚｅｔｈｅｄｅｓｉｇｎｏｆｄｉｓｔｉｌｌａｔｉｏｎｃｏｌｕｍｎｓ .Ａｖａｒｉｅｔｙｏｆｅｘｐｅｒｉｍｅｎｔａｌａｐｐｒｏａｃｈｅｓｈａｖｅｂｅｅｎｕｓｅｄｔｏｍｅａｓｕｒｅｔｈｅｉｎｔｅｒｆａｃｉａｌａｒｅａｓａｎｄｂｕｂｂｌｅｓｉｚｅｄｉｓ ｔｒｉｂｕｔｉｏｎｓ… 相似文献
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基于物理化学实验教材“最大气泡法测定液体的表面张力”实验中毛细管与液面相切难控制、毛细管鼓泡速率难控制的缺点提出了改进方案.由注射器代替滴管控制液体加入量,较容易使毛细管与液面刚好相切;采用带活塞的锥形瓶与注射器联用取代滴流瓶控制减压操作气泡形成的速率;用计算机取代人工处理实验数据和绘图.改进后的实验数据准确度和精密度均有所提高. 相似文献
4.
This paper presents ak-ε-k
p
multi-fluid model for simulating confined swirling gas-solid two phase jet comprised of particle-laden flow from a center
tube and a swirling air stream entering the test section from the coaxial annular. A series of numerical simulations of the
two-phase flow of 30 μm, 45 μm, 60 μm diameter particles respectively yielded results fitting well with published experimental
data.
Project is supported by Zheijiana Provincial Natural Science Foundation (No. 598017) 相似文献
5.
Xia Fengshun Li Wenpeng Guo Junheng Han You Zhang Minqing Wang Baoguo Li Wei Zhang Jinli 《天津大学学报(英文版)》2021,27(5):409-421
A pore-array intensified tube-in-tube microchannel (PA-TMC), which is characterized by high throughput and low pressure drop, was developed as a gas–liquid contactor. The sulfite oxidation method was used to determine the oxygen efficiency (φ) and volumetric mass transfer coefficient (kLa) of PA-TMC, and the mass transfer amount per unit energy (ε) was calculated by using the pressure drop. The effects of structural and operating parameters were investigated systematically, and the two-phase flow behavior was monitored by using a charge-coupled device imaging system. The results indicated that the gas absorption efficiency and mass transfer performance of the PA-TMC were improved with increasing pore number, flow rate, and number of helical coil turns and decreasing pore size, row number, annular size, annular length, and surface tension. The φ, ε and kLa of PA-TMC could reach 31.3%, 1.73 × 10−4 mol/J, and 7.0 s−1, respectively. The Sherwood number was correlated with the investigated parameters to guide the design of PA-TMC in gas absorption and mass transfer processes.
相似文献6.
Gas-solid two-phase turbulent plane jet is applied to many natural situations and in engineering systems. To predict the particle
dispersion in the gas jet is of great importance in industrial applications and in the designing of engineering systems. A
large eddy simulation of the two-phase plane jet was conducted to investigate the particle dispersion patterns. The particles
with Stokes numbers equal to 0.0028, 0.3, 2.5, 28 (corresponding to particle diameter 1 μm, 10μm, 30μm, 100μm, respectively)
inRe=11 300 gas flow were studied. The simulation results of gas phase motion agreed well with previous experimental results.
And the simulation results of the solid particles motion showed that particles with different Stokes number have different
spatial dispersion; and that particles with intermediate Stokes number have the largest dispersion ratio.
Project (No. G19990222) supported by the Special Funds for Major State Basic Research of China 相似文献
7.
In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq. (19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline. 相似文献
8.
改革开放以来,中国经济以前所未有的速度增长,取得了举世瞩目的成就。但在经济高速增长的大好形势下,必须清醒地看到某些泡沫经济状况已有滋生。为了防止泡沫的膨胀和破灭给国民经济带来的重大损失和危机,我们必须从现在就要对已经产生的房地产业和金融业领域的泡沫经济开始防范。本文正是在分析上述泡沫的表现、危害性和成因的基础上,探讨和提出了防范“泡沫经济”的若干对策和建议。 相似文献
9.
Numerical investigation of cavitating flow behind the cone of a poppet valve in water hydraulic system 总被引：2，自引：0，他引：2
Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using
advanced RNGk-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43000. The
working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model.
Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as
poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was
conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera.
The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good
agreement with the numerical result.
Project supported by the National Natural Science Foundation of China (No. 59835160) and Scientific Research Foundation for
Returned Overseas Chinese Scholars, State Education Ministry of China (No. 50175097) 相似文献
10.
CHANSON Hubert 《浙江大学学报(A卷英文版)》2006,7(8):1396-1405
INTRODUCTION A hydraulic jump is the sudden transition from a high-velocity, supercritical open channel flow into a slow-moving, sub-critical flow (Belanger, 1840; Bakhmeteff, 1932; Henderson, 1966; Chanson, 2004a). It is characterised by a sudden rise of the free-surface, with some strong energy dissipation and mixing, large-scale turbulence, air entrainment, waves and spray (Fig.1). Early experimental studies of air bubble entrainment were conducted in terms of the quantity of entrain… 相似文献
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采用超声波提取茶叶中的茶多酚,并应用高效液相色谱法对不同品种的茶叶及同一产地不同档次的茶叶中的茶多酚成份进行分析测定.结果表明,采用Hyper-sil ODS柱,超纯水、甲醇和0.36%的乙酸为流动相,梯度洗脱,流速为0.8 mL.min-1,柱温40℃,在280 nm波长处可对儿茶素进行检测,其线性范围为0.6~3.0 g.L-1,R为0.999 6~0.999 9. 相似文献
14.
In order to overcome the inconvenience of manual bubble counting, a bubble counter based on photoelectric technique aiming for automatically detecting and measuring minute gas leakage of cryogenic valves is proposed. Experiments have been conducted on a self-built apparatus, testing the performance with different gas inlet strategies （bottom gas-inlet strategy and side gas-inlet strategy） and the influence of gas pipe length （0, 1, 2, 4, 6, 8, 10 m） and leakage rate （around 10, 20, 30, 40 bubbles/min） on first bubble time and bubble rate. A buffer of 110 cm^3 is inserted between leakage source and gas pipe to simulate the downstream cavum adjacent to the valve clack. Based on analyzing the experimental data, experiential parameters have also been summarized to guide leakage detection and measurement for engineering applications. A practical system has already been successfully applied in a cryogenic testing apparatus for cryogenic valves. 相似文献
15.
Vortex-ring cavitation occurs when the pressure inside a torus-shaped core of a vortex ring falls below the vapor pressure of the ambient liquid. By generating a vapor bubble in a rigid tube, a toroidal cavity can be produced outside the tube. The pulsation and propagation behaviors of vortex-ring cavitation are studied using a high-speed video camera and a hydrophone. The experimental results show that the cavity continues to oscillate with a period that depends heavily on the maximal cross-section radius of the cavity and circulation of the vortex flow, under the influence of the surrounding vortex flow field. It is also shown that the cross-radial oscillation of the toroidal cavity can be measured both by a high-speed camera and hydrophone. Moreover, three different methods for estimating the circulation are compared to propose an accurate model of toroidal cavity oscillation. The phenomenon of a toroidal cavity impinging on a fixed wall is also investigated. 相似文献
16.
A high speed column-parallel CDS/ADC circuit with nonlinearity compensation is proposed in this paper.The correlated double sampling (CDS) and analog-to-digital converter (ADC) functions are integrated in a threephase column-parallel circuit based on two floating gate inverters and switched-capacitor network.The conversion rate of traditional single-slope ADC is speeded up by dividing quantization to coarse step and fine step.A storage capacitor is used to store the result of coarse step and locate the section of ramp signal of fine step,which can reduce the clock step from 2 n to 2 (n/2+1).The floating gate inverters are implemented to reduce the power consumption.Its induced nonlinear offset is cancelled by introducing a compensation module to the input of inverter,which can equalize the coupling path in three phases of the proposed circuit.This circuit is designed and simulated for CMOS image sensor with 640×480 pixel array using Chartered 0.18μm process.Simulation results indicate that the resolution can reach 10-bit and the maximum frame rate can reach 200 frames/s with a main clock of 10MHz.The power consumption of this circuit is less than 36.5μW with a 3.3V power supply.The proposed CDS/ADC circuit is suitable for high resolution and high speed image sensors. 相似文献
17.
生物样品中短链脂肪酸提取测定及其应用进展 总被引：2，自引：0，他引：2
综述了不同样品（尿液、血液、生物培养液等）中短链脂肪酸的测定方法,讨论了气相色谱、高效液相色谱、毛细管电泳、原子吸收分光光度测定方法的优缺点,并讨论了短链脂肪酸在营养生理、疾病以及肠道菌群中的应用研究进展. 相似文献
18.
Over the past decade, significant attention has been paid to flow in microtubes due to the develop- ment in micro fluidic devices and systems. The un- derstanding of flow characteristics such as pressure drop is important in the design and process control of microfluidic devices. However, experimental evidence indicates sig- nificant departure of flow characteristics from the predictions of conventional theory for smaller di- ameter microtubes. Pfahler et al.(1991) observed that as the channel… 相似文献
19.
Cu(In,Ga)Se2 (CIGS) precursor films were deposited on Mo/glass by electrodeposition, and then annealed in Se vapor. The annealing temperature ranged from 450 °C to 580 °C, and two heating rates were selected. The results showed that the crystalline quality of the CIGS films and formation of the Cu-Se compound could be strongly influenced by the selenization temperature and heating rate. Raman spectroscopy and X-ray diffraction (XRD) analysis showed that when the selenization temperature was increased from 450 °C to 550 °C, the amount of binary CuSe phase decreased and the amount of Cu2Se increased. After annealing at 580 °C, a minimum amount of Cu2?xSe compounds was obtained and the degree of CIGS film crystallinity was higher than in other samples. The relationship between the properties of the film and the heating rate was studied. XRD and Raman spectra showed a decrease in the Cu2?xSe phase with increasing heating rate. Scanning electron microscopy (SEM) and XRD showed a remarkable increase in the grain size of CIGS during rapid heating. 相似文献
20.
Kyle Potter Lawrence Lewandowski Laura Spenceley 《Assessment & Evaluation in Higher Education》2016,41(7):996-1007
Standardised and other multiple-choice examinations often require the use of an answer sheet with fill-in bubbles (i.e. ‘bubble’ or Scantron sheet). Students with disabilities causing impairments in attention, learning and/or visual-motor skill may have difficulties with multiple-choice examinations that employ such a response style. Such students may request and receive testing accommodations that intend to mitigate these impairments, such as circling responses in a test booklet, which contains both the questions and corresponding multiple-choice answers. The current study evaluated this test accommodation as compared to using a bubble sheet or Scantron on a multiple-choice vocabulary test. College students with (n = 25) and without (n = 76) disabilities completed a vocabulary test under both booklet (accommodated) and bubble sheet (standard) conditions. Results demonstrated that answering in a test booklet, a much preferred response mode, allowed students to attempt significantly more items than using a bubble sheet, improving their overall test scores. Booklet responding tends to improve overall performance, even for students without disabilities, calling into question the specificity and validity of this accommodation. 相似文献