Papers by Author: Zhi Yong Ling

Abstract: Molecular dynamics simulations are carried out to explore the fluid flows in parallel-plate nanochannels. A “channel moving” pressure-driven model is utilized to study the planar Poiseuille flows. Considering the slip boundary conditions, relationships among the pressure gradient, mean flow velocity and the channel width are investigated to couple the atomistic regime to continuum. The results show that the mean flow velocity almost linearly increases with the increase of the pressure gradient. The slope of the linear relationship between the pressure gradient and the mean flow velocity is nonlinearly decreased with increasing the channel width. The results indicate that the approximate accuracy is reduced with decreasing the channel width while the pressure-driven flows confined in nanochannels are approximately described by the Navier-Stokes equations.

Abstract: A numerical study on the convective heat transfer characteristics of Cu-water nanofluid under the laminar flow condition was performed. The results show that the convective heat transfer coefficient increases with the increase of the volume fraction of the nanoparticles and the Reynolds number. There is a significant difference between the numerical simulation result and the result calculated from the Shah equation in the entrance region, but a small difference in full development areas. The numerical results agree well with that obtained from the Xuan equation when the Reynolds number and the volume fraction of the nanoparticles are small, but the errors between them increase as the increase of the Reynolds number and the volume fraction of nanoparticles.

Abstract: In this paper, conducting polypyrrole (PPy) films doped with p-toluene solfonate (pTS) was electrochemically synthesized. The chemical groups of the sample were analysed by FT-IR, an in situ nanotribolab system together with the four-probe instrument were employed to investigate the mechanical and conductivity of the prepared films. The surface morphology was studied by scanning electron microscopy (SEM). It demonstrates that the dopant anion was doped into the PPy while the overoxidation did not occur during the polymerization. The conductivity of PPy film is stable, during indentation, different loads were applied and hardness, elastic modulus were obtained. SEM images showed that the film is uniform. The characteristic microstructure of polypyrrole, the cauliflower-like, is appeared and the film is compact and homogeneous.

Abstract: In this paper, a micromixer used in micro thermo photovoltaic system (MTPV system) is simulated and fabricated. The optimal structure parameters were investigated by computational fluent dynamical software (CFD)，during the simulation, three main parameters n,τ and δ were introduced to studied on the influence of the mixing intensity . The simulation results show that the number of the static elements added in the mixing channel n should be more than 4, the side-length of the static elements should be half of the channel’s width and the static elements should be equidistant and interlaced distribution.

Abstract: The 3D entity model for the amplitude changing mechanism of boom system of certain 48 meters concrete pump vehicle was established by means of Pro/E software, and then it was imported into ADAMS/VIEW to find out the maximum load carrying capacity of hydraulic cylinder under various working conditions. Under the environment of ADAMS/VIEW, parametric model of boom system was built. Utilizing the measure of design evaluation tools (DET) in ADAMS, optimization design of the amplitude changing mechanism of boom system was commendably achieved. This method evidently minimized the maximum load carrying capacity of hydraulic cylinder, and greatly improved the working performance of boom system.

Abstract: A DLC/SEBS/A187/Si multilayer was prepared by self-assembled monolayer (SAM) method and pulse filtered catholic vacuum arc source (FCVA) technology. Microstructure and frictional properties of the film were investigated by using X-ray photoelectron spectroscopy (XPS), AFM, SEM and UMT-2MT tribometer. Results showed that the peaks appearing at 287.8eV for XPS demonstrated the successfully graft of SEBS on the couple agent(A187); The surface of the top DLC film was compactly and uniformly distributed; Friction coefficient of the prepared film was not sensitive to velocity under low load and the coefficient ranged from 0.1 to 0.15, but at high load, the tribological property of the film deteriorated with the increasing of sliding velocity, when the normal load was 2N and the sliding speed was 30 r/min, only the top DLC film was scratched out, but when the sliding velocity increased to 240 r/min, the whole prepared film was scratched out.

Abstract: Micro-flowing technique gained popular applications in microdevices of microelectromechanical systems (MEMS), and the performance of micro-devices is greatly determined by the properties of micro-flow. This paper studied the characteristics of different viscosity fluid flowing over microchannels with different diameters and lengths under low pressure driving, and the influence of scale effects on the flowing characteristics of low viscosity fluids was also examined. The experiments studied the flow rate–pressure characteristics of distilled water flowing over microchannels with diameter of 13 μm, 20 μm, and silicon oil flowing over microchannels with diameters of 50 μm, 100 μm. The results indicate that, when the diameter of micro-channel is more than 20 μm, the flowing characteristics of distilled water and silicon oil agrees well with conventional flow theory, and when the diameter of microchannels is 13μm, the flowing characteristics are related to the length of micro-channel. When the length is relatively shorter, the flowing characteristics are almost in agreement with the conventional flow theory. When the length reaches 100 mm, the flow rate is much higher than the values predicted by theoretical calculation when the length reaches 100 mm. It is obvious that scale effect arises when the length arrives to 100 mm and the velocity slippage results in the great increase of flow rate.