Wear dependent virtual flow rate sensor for progressing cavity pumps with deformable stator

This contribution presents a novel wear dependent virtual flow rate sensor for single stage single lobe progressing cavity pumps. We study the wear-induced material loss of the pump components and the impact of this material loss on the volumetric efficiency. The results are combined with an established backflow model to implement a backflow calculation procedure that is adaptive to wear. We use a laboratory test setup with a highly abrasive fluid and operate a pump from new to worn condition to validate our approach. The obtained measurement data show that the presented virtual sensor is capable of calculating the flow rate of a pump being subject to wear during its regular operation.

Backflow Transformation for A=3 Nuclei with Artificial Neural Networks

A novel variational wave function defined as a Jastrow factor multiplying a backflow transformed Slater determinant was developed for A=3 nuclei.The Jastrow factor and backflow transformation were represented by artificial neural networks.With this newly developed wave function,variational Monte Carlo calculations were carried out for3H and3He nuclei starting from a nuclear Hamiltonian based on the leadingorder pionless effective field theory.The obtained ground-state energy and charge radii were successfully benchmarked against the results of the highly-accurate hypersphericalharmonics method.The backflow transformation plays a crucial role in improving the nodal surface of the Slater determinant and,thus,providing accurate ground-state energy.

Tectonic Evolution of the Himalayan Collision Belt

This paper discusses the tectonic divisions of the Himalayan collision belt anddeals with the tectonic evolution of the collision belt in the context of crustal accretion in thefront of the collision belt, deep diapirism and thermal-uplift extension and deep material flow-ing of the lithosphere-backflowing. Finally it proposes a model of the tectonic evolution-progressive intracontinental deformation model-of the Himalayan belt.

用扩散蒙特卡罗方法研究BH2、B（0H）2、BCl2和BCI的键离解能

采用扩散蒙特卡罗（DMC）方法计算了BH2、B（OH）2、BCl2和BCl的HB—H和HOB—OH的键离解能，同时也研究了轨道选择和Backflaw变换对DMC计算结果的影响．在Slater-Jastrow DMC（SJ—DMC）计算方法中，当采用B3PW91轨道时得到的HB—H和HOB-OH键离解能分别是359．1±0．12和98．2±0．12kJ／mol；用B3LYPSJ—DMC计算键离解能得到r与用B3PW91SJ—DMC方法类似的结果．通过BF—DMCf即在DMC中引入backflow修正）计算得到的HB—H键离解能为369．6±0．12kJ／mol，也得到了更加接近实验值的HOB-OH键离觯能为446．0±1．84kJ／mol．由DMC的计算结果可以断定HB—H的键离解能的实验值为375．8kJ／mol．另外还给出了BCl2和BCl的键离解能的计算结果．

Three-dimensional distinct element modeling of fault reactivation and induced seismicity due to hydraulic fracturing injection and backflow

This paper presents a three-dimensional fully hydro-mechanical coupled distinct element study on fault reactivation and induced seismicity due to hydraulic fracturing injection and subsequent backflow process,based on the geological data in Horn River Basin,Northeast British Columbia,Canada.The modeling results indicate that the maximum magnitude of seismic events appears at the fracturing stage.The increment of fluid volume in the fault determines the cumulative moment and maximum fault slippage,both of which are essentially proportional to the fluid volume.After backflow starts,the fluid near the joint intersection keeps flowing into the critically stressed fault,rather than backflows to the wellbore.Although fault slippage is affected by the changes of both pore pressure and ambient rock stress,their contributions are different at fracturing and backflow stages.At fracturing stage,pore pressure change shows a dominant effect on induced fault slippage.While at backflow stage,because the fault plane is under a critical stress state,any minor disturbance would trigger a fault slippage.The energy analysis indicates that aseismic deformation takes up a majority of the total deformation energy during hydraulic fracturing.A common regularity is found in both fracturing-and backflow-induced seismicity that the cumulative moment and maximum fault slippage are nearly proportional to the injected fluid volume.This study shows some novel insights into interpreting fracturing-and backflowinduced seismicity,and provides useful information for controlling and mitigating seismic hazards due to hydraulic fracturing.

An Improved Three-Dimensional Non-Equilibrium Mixing Pool Model

This paper presents an improved three-dimensional non-equilibrium mixing pool model.It is a simplified form of the original model and is more practical for applications.The simulation re-sults show that the industrial scale distillation tray columns can be described closely by the improvedmodel.The effects of model parameters,such as the number of mixing pools,the point efficiencyand flow pattern,on separation are analyzed quantitatively.

Research on active arc-ignition technology as a possible residual-energy-release strategy in electromagnetic rail launch

In order to solve the problem of the original residual energy release strategy being unsuitable for high-energy and fast-firing electromagnetic rail launch,this work has explored the applicability of active arc-ignition technology(AAT).The results obtained from the comparison of launching experiments show that AAT has no influence on the acceleration of the armature and is capable of quickly releasing the residual energy.Based on the theory of magnetohydrodynamics,this work has also made numerical simulation of the muzzle arc,analyzed the influence of AAT on the muzzle arc flow field,electromagnetic(EM)field and temperature field,and evaluated the performance of AAT according to the projectile initial disturbance,the EM impact on guidance devices and the rail ablation.The results show that AAT is now one of the most practicable strategies for residual energy release.

Numerical simulation of liquid core reduction in thin-slab continuous casting

Thin-slab continuous casting and rolling technology is a process integrating casting and plastic deformation. In this study,targeting actions such as slab deformation and liquid core flows during the process of liquid core reduction on thin-slab continuous casting, suggests the fluid-solid coupling method should be used to research the characteristic and patterns of slab deformation during the liquid core reduction process, as well as research liquid core backflows. A material model of the slab shell was obtained through the high-temperature compression test of the cast steel. The analysis of the fluid-solid coupling simulation for liquid core reduction shows that slab deformation concentrates on the narrow side due to the existence of the liquid core. Meanwhile,the stress and strain increases with the increase of the reduction rate and slab thickness. The changing trends of stress and strain are identical under various conditions. The results demonstrate that using greater reduction at the upper part of the slab, which has a higher temperature and thinner slab,is beneficial to the quality of the slab. Moreover,the liquid core is extruded as the reduction is implemented. The quantity of the extrusion increases with the increase of reduction rate and the thickness of thinner shell, which leads to fluctuation of the mould level, making the operation more difficult.

Backflow of Migrant Workers in Urbanization: Place Selection and Influencing Factors

Backflow of migrant workers is an essential part of rural surplus labor transfer. 425 valid samples from Haicheng,Taian and Xiuyan cities of Liaoning Province were analyzed and place selection and influencing factors were discussed. The study indicated that in backflow migrant workers,43. 16% returned to counties and towns,while 56. 84% returned to rural areas. Place selection was significantly influenced by years of migrant work,training,times of migration,migration distance,age,land area in hometown,and living preference.

Hydraulic fluctuations during the pump power-off runaway transient process of a pump turbine with consideration of cavitation effects

A runaway transition after the pump power interruption and the simultaneous guide vane servomotor failure is one of the most dangerous and complex transitions for a pumped storage power system(PSPS).This paper analyzes the fluctuation behavior and mechanism of a PSPS during a runaway transition caused by the pump power interruption.The transient cavitation flow in the PSPS is simulated by using a one-dimensional and three-dimensional coupling flow simulation method for the runaway transition.Subsequently,the effects of the transient fluctuation of the radial hydraulic thrust on the runner and transient pressures are analyzed using the short-time Fourier transform method.Finally,the mechanisms are analyzed based on the analysis of the internal flow field.This study suggests that the extreme fluctuation generally occurs near the critical transformation points between the two operation modes.In addition,the extreme fluctuation behavior is primarily related to the local backflow near the runner inlet and the unstable cavitation phenomena in the runner and the draft tube.This finding helps for optimizing the runner design to resolve the instability problems of a PSPS.

Numerical simulation of hydraulic force on the impeller of reversible pump turbines in generating mode

The hydraulic force on the reversible pump turbine might cause serious problems（e.g., the abnormal stops due to large vibrations of the machine）, affecting the safe operations of the pumped energy storage power plants. In the present paper, the hydraulic force on the impeller of a model reversible pump turbine is quantitatively investigated through numerical simulations. It is found that both the amplitude of the force and its dominant components strongly depend on the operating conditions（e.g., the turbine mode, the runaway mode and the turbine brake mode） and the guide vane openings. For example, the axial force parallel with the shaft is prominent in the turbine mode while the force perpendicular to the shaft is the dominant near the runaway and the turbine brake modes. The physical origins of the hydraulic force are further revealed by the analysis of the fluid states inside the impeller.

Quantum super-oscillation of a single photon

Super-oscillation is a counterintuitive phenomenon describing localized fast variations of functions and fields that happen at frequencies higher than the highest Fourier component of their spectra.The physical implications of this effect have been studied in information theory and optics of classical fields,and have been used in super-resolution imaging.As a general phenomenon of wave dynamics,super-oscillations have also been predicted to exist in quantum wavefunctions.Here we report the experimental demonstration of super-oscillatory behavior of a single-quantum object,a photon.The super-oscillatory behavior is demonstrated by tight localization of the photon wavefunction after focusing with an appropriately designed slit mask to create an interference pattern with a sub-diffraction hotspot(~0.45λ).Such quantum super-oscillation can be used for low-intensity far-field super-resolution imaging techniques even down to single-photon counting regime,which would be of interest to quantum physics and non-invasive and label-free biological studies.

Comparison on Hydraulic Characteristics Between Orifice Plate and Plug

Orifice plate energy dissipater as well as plug energy dissipater, as a kind of effective energy dissipater with characteristics of simple structure, convenient construction and high energy dissipation ratio, has become welcomed more and more by hydraulics researchers. The two kinds of energy dissipaters with sudden reduction and sudden enlargement forms are similar in energy dissipation mechanism, but there are differences in energy dissipation characteristics and cavitation characteristics. In the present paper, the differences between orifice plate and plug in energy loss coefficient, relating to their energy dissipation ratio, in the backflow region length, relating to their energy loss coefficient, and in the lowest wall pressure coefficient, relating to their cavitations risk, were analyzed by numerical simulations and physical experiment, and their features in above three aspects were also revealed. The results of research in the present paper demonstrate that the backflow region length of orifice plate is longer than that of plug at the same contraction ratio, the lowest wall pressure coefficient of plug is smaller than that of orifice plate at the same contraction ratio, and the energy loss coefficient of orifice plate is bigger than that of plug, which illustrates that plug is superior to orifice plate in resistance cavitation damage at the same contraction ratio.

Numerical investigation of the effect of T-shaped blade on the energy performance improvement of a semi-open centrifugal pump

The tip leakage flow formed by the tip clearance of a semi-open centrifugal pump adversely affects the energy performance and the energy waste. A T-shaped blade is proposed to be used to improve the energy characteristics. The internal flow field is simulated via the shear stress transport turbulence model to analyze the influence of the T-shaped blade on the performance of a centrifugal pump. It is shown that with the T-shaped blade, the hydraulic loss can be reduced, the Euler head can be increased, and the external characteristics can be improved. The maximum head and efficiency improvements are 3% and 1.6%, respectively. The relative flow angle near the tip clearance of the T-shaped blade decreases, and the strength of the backflow region is remarkably weakened. The area of the high entropy production region decreases, and the trend of the upstream diffusion is restrained under the design condition. The T-shaped blade can help to inhibit the diffusion of the high entropy production region to the hub under the low flow rate condition, but the entropy production and the mixing losses at the tip clearance are slightly increased. This research provides a new method for improving the energy performance of the semi-open centrifugal pump.

NUMERICAL SIMULATION ON EMERGENCY TUNNEL FIRES WITH TRANSVERSE VENTILATION

In case of an emergency fire in vehicle tunnel, the ventilation system should be operated effectively to control the thermal fume and smoke inside tunnel. However, it is quite difficult to predict every kind of emergency fire by fire tests because the actual movement of thermal fume and smoke is affected by many factors such as ventilation system, structure of the tunnel, etc., especially for tunnels equipped with transverse ventilation system on which rare experimental and numerical studies have been found so far. In this paper, a three dimensional numerical simulator using LES turbulence model is developed to simulate the movement of thermal fume induced by emergency fire in vehicle tunnel. The SMAC method is employed to calculate the pressure and velocity fields. The upwind differnece scheme with the third order accuracy is applied for the discretization of convection terms of the governmental equations. As the applications of the present simulator, the behavior of thermal fume induced by emergency fire in a vehicle tunnel with two direction traffic is analyzed. It is confirmed that the partial transverse ventilation system is more effective than the longitudinal ventilation system under large and small velocities of longitudinal bulk flow inside tunnel. Simulation result also shows that remaining the velocity of longitudinal bulk flow near zero around fire source can provide the best working condition for partial transverse ventilation system.