There is a need for charging electric vehicles (EVs) wirelessly since it provides a more convenient, reliable, and safer charging option for EV customers. A wireless charging system using a ...double-sided LCC compensation topology is proven to be highly efficient; however, the large volume induced by the compensation coils is a drawback. In order to make the system more compact, this paper proposes a new method to integrate the compensated coil into the main coil structure. With the proposed method, not only is the system more compact, but also the extra coupling effects resulting from the integration are either eliminated or minimized to a negligible level. Three-dimensional finite-element analysis tool ANSYS MAXWELL is employed to optimize the integrated coils, and detailed design procedures on improving system efficiency are also given in this paper. The wireless charging system with the proposed integration method is able to transfer 3.0 kW with 95.5% efficiency (overall dc to dc) at an air gap of 150 mm.
The double-sided LCC topology provides a highly efficient compensation method for electric vehicle (EV) wireless charging systems. However, the two compensated coils occupy a large volume. In order ...to address the volume increase as well as to be compatible with unipolar coil structures, which are widely applied in EV wireless charging systems, an integration method is introduced in this paper. Aspect ratios of the compensated coils are studied to minimize the respective coupling effect. With the proposed integration method, the extra coupling coefficients are either eliminated or decreased to a negligible level. A wireless charging system with the proposed integration method is built and the experimental results show that the system resonates at 85 kHz and delivers 3.09 kW with a dc-dc efficiency of 95.49% at an air gap of 150 mm. Furthermore, a comparison with the integration method into bipolar coil structures is presented and the results demonstrate that the system with the proposed integration method is more immune to front-to-rear and vertical misalignments.
•Influence of phase-change on the collapse and rebound stages of spark-generated explosion bubbles was numerically studied.•A reasonable agreement of the bubble radius with the experimental data was ...obtained, particularly at the second cycle.•The condensation process had the highest influence and mainly occurred at the bubble interfaces with a thin boundary layer.•Secondary cavitation regions in the water field induced by rarefaction waves were observed.•The effects of source term by temperature changes on the bubble dynamics were estimated thoroughly.
Influences of phase-change are generally ignored by current numerical models that are used to study spark-generated cavitation bubble dynamics. However, this assumption was limited to predicting bubble behaviors only at the first expansion and collapse stages. In this study, we aimed to explore the phase-change effects on the cavitation bubble dynamics over multiple cycles. A combination of a two-phase homogeneous mixture model and interface-capturing method was adopted to simulate the bubble dynamics. The full compressibility of the water and vapor phases, heat transfer, condensation, and evaporation were involved in our numerical model. Phase-change processes due to pressure changes and temperature changes were evaluated to explore the major influence phenomenon on the bubble dynamics. By comparing with experimental data, a compatible bubble shape and radius evolution under a free-field condition was obtained, particularly at the rebound and collapse stages. Disturbance secondary cavitation regions in the water field induced by rarefaction waves were observed immediately after the second rebound stage. In addition, bubble dynamic behaviors were mainly affected by the condensation phenomenon. The condensation mass transfer rate increases, becomes extremely high at the final collapse stage, and decreases during the rebound stage. Moreover, the condensation phenomenon mainly occurs at the vapor–water bubble interfaces with a thin boundary layer. The evaporation phenomenon occurred purely inside bubbles with a uniform region. Finally, we discuss the effects of phase-change by temperature changes on the cavitation bubble dynamics. In general, these effects were sufficiently small during the first two-cycle bubble oscillations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An accurate SoC (state of charge) and SoP (state of power capability) joint estimator is the most significant techniques for electric vehicles. This paper makes two contributions to the existing ...literature. (1) A data-driven parameter identification method has been proposed for accurately capturing the real-time characteristic of the battery through the recursive least square algorithm, where the parameter of the battery model is updated with the real-time measurements of battery current and voltage at each sampling interval. (2) An adaptive extended Kalman filter algorithm based multi-state joint estimator has been developed in accordance with the relationship of the battery SoC and its power capability. Note that the SoC and SoP can be predicted accurately against the degradation and various operating environments of the battery through the data-driven parameter identification method. The robustness of the proposed data-driven joint estimator has been verified by different degradation states of lithium-ion polymer battery cells. The result indicates that the estimation errors of voltage and SoC are less than 1% even if given a large erroneous initial state of joint estimator, which makes the SoP estimate more accurate and reliable for the electric vehicles application.
•A data-driven parameter identification method is developed by RLS algorithm.•An adaptive multi-state joint estimator of the battery is developed by AEKF algorithm.•A data-driven SoC and SoP joint estimator is developed with the real-time measurement.•Robustness of the joint estimator is verified by different aging states of LiPB cells.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
To assess the role of in-flight transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we investigated a cluster of cases among passengers on a 10-hour commercial flight. ...Affected persons were passengers, crew, and their close contacts. We traced 217 passengers and crew to their final destinations and interviewed, tested, and quarantined them. Among the 16 persons in whom SARS-CoV-2 infection was detected, 12 (75%) were passengers seated in business class along with the only symptomatic person (attack rate 62%). Seating proximity was strongly associated with increased infection risk (risk ratio 7.3, 95% CI 1.2-46.2). We found no strong evidence supporting alternative transmission scenarios. In-flight transmission that probably originated from 1 symptomatic passenger caused a large cluster of cases during a long flight. Guidelines for preventing SARS-CoV-2 infection among air passengers should consider individual passengers' risk for infection, the number of passengers traveling, and flight duration.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•Compressible multiphase model based on a geometrical PLIC-VOF based simulation method.•Fully conservative hyperbolic system is solved based on a Riemann solver.•Reconstruction of the Riemann solver ...for oscillation-free behavior near contact discontinuity.•Dynamic behavior of bubble collapses, high-speed jets, and pressure loads.•3D bubble collapse near a free surface and an oblique wall.
The dynamic behavior of bubble collapses, water jets, and pressure loads during the collapse of the bubble near walls and a free surface were numerically investigated via a geometrical volume of fluid (VOF)-based simulation method. The numerical method is based on the compressible Navier–Stokes equations in a conservative form that describe the flow of compressible viscous fluids. The equations are discretized on a general curvilinear grid using an associated Godunov-type numerical scheme, and a reconstruction of a computational finite-volume Riemann solver is introduced for suppression of oscillation near the interface between fluids. The interface was tracked using the VOF reconstruction method. The VOF method is based on a geometrical tool and Lagrangian propagation of the interface reconstructed by a piecewise linear interface calculation (PLIC), resulting in strictly mass-conserving and sharp interface solutions. The numerical procedure was validated for capturing sharp interface and strong shock waves. For the simulation of bubble collapse, grid dependence studies of a spark-generated bubble were studies of both spherical and non-spherical bubbles were conducted. The results showed good agreement between the simulation and experiment of the bubble dynamics during the collapse process. Subsequently, an investigation of a single bubble near a wall with different standoff distances was performed. The pressure loads induced by the jets impacting the walls were calculated and analyzed. Furthermore, a more complex case of bubble collapse near an oblique wall and free surface was simulated. The resulting bubble dynamics with the jets and free surface shape were compared via photographs of the experiments.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•An unsteady natural cavitating flow around an axisymmetric projectile is numerically studied using fully compressible homogeneous multiphase approach.•Good agreement is obtained regarding the cavity ...structures and dynamics evolution with the experimental data.•Detailed mechanisms of the cavity shedding with periodic cavity–vortex–pressure interaction behaviors are revealed.•The cavity shape tends to be mushier with increasing water temperature under the same reference cavitation number and reynolds number.
Here, an unsteady natural cavitating flow around an axisymmetric projectile is computationally studied using a homogeneous multiphase approach. The numerical models used are based on a dual-time preconditioning method, an interface-capturing scheme, and a modified cavitation model, to capture unsteady cavitation structure behaviors. Full compressibility of two phases and an energy equation are used to determine the effects of temperature on a cavitating flow. First, the experimental data were validated at a cavitation number of σ = 0.435. Both quantitatively and qualitatively good agreements were achieved, including the evolution of the cavity shape, cavity length, and cavity thickness. Then, the key characteristics of an unsteady cavitation structure regarding the cavity growth, re-entrant jet, cavity shedding, and collapse were analyzed. In particular, the mechanism of the re-entrant jet inside the cavity, causing the periodic cavity shedding, was explored. Furthermore, detailed mechanisms of cavity shedding with periodic cavity–vortex–pressure interaction behaviors were analyzed. Finally, the influences of free-stream temperature on the cavitation structure behaviors were carefully investigated. It was found that both the cavity length and thickness increased with the free-stream temperature under the atmospheric pressure condition. The most sensitive effects occurred when the free-stream temperature approached its boiling point. In case of the same reference cavitation number and Reynolds number, the cavity shape tended to be mushier with increasing water temperature.
Evolution of the cavity shape of unsteady natural cavitating flow around an axisymmetric projectile with the cavitation number σ= 0.435. Special characteristic motions including cavity incipient, growth, re-entryre-entrant jet, shedding, and collapse are well captured with experimental images. Display omitted
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Clay brick waste powder can be used as a mineral addition in mortar.•Ceramic waste aggregate is a non-active aggregate in terms of alkali-silica reaction.•Decreased flow spread of mortar was ...observed.•A rough texture of ceramic waste aggregate improved compressive strength of mortar.•Clay brick waste powder improved compressive strength of mortar in long term.
This study investigates the potential use of clay brick waste powder (CBP) and ceramic waste aggregate (CWA) in mortar. Cement was replaced by CBP in the mortar mixtures at four ratios (10, 20, 30 and 40 wt%). Meanwhile, CWA was used as a substitute for river sand in the mortar at two levels (50 and 100 wt%). The results demonstrated that the flow spread of the mortars made of CBP and CWA declined sharply owing to the rough and multi-angle texture of their surface. The compressive strength of the mortars decreased slightly at early ages but noticeably improved long term.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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