Voltage-controlled bimeron diode-like effect in nanoscale information channel

The magnetic bimeron, as the in-plane counterpart of the magnetic skyrmion, has potential applications in next-generation spin memory devices due to its lower energy consumption. In this work, the dynamic behavior of a current-driven bimeron in a nanotrack with voltage-controlled magnetic anisotropy (VCMA) is investigated. By adjusting the profile of the VCMA, the bimeron can display a diode-like unidirectional behavior in the nanotrack. The unidirectional behavior can be modulated by changing the driven current density and width of the VCMA region. The trajectory of the bimeron can also be controlled by the periodic VCMA region, which can enhance the stability of bimeron and realize a high-storage density bimeron-based information channel

Macroscopic and microscopic characteristics of a single-hole spray under low ambient pressure induced conditions

Flash boiling spray is a promising method to improve atomization, which subsequently affects the combustion phenomenon in engines. Therefore, an investigation on both macroscopic and microscopic characteristics of the flash boiling spray should be done to understand this behavior and mechanism. A mini-sac injector with a single hole was used under different injection pressures among 10, 15, and 20 MPa. Experiments were performed in a constant volume chamber with low ambient pressures varying from 5 to 100 kPa. First, macroscopic behaviors including morphology, spray tip penetration, spray angle, and spray cone angle were compared by a Mie scattering method. Then, microscopic characteristics of flash boiling spray were obtained with the help of particle image analysis technology. In order to analyze the droplet behaviors along the spray axis completely, a spray "slicer" was introduced to filter the spray. The influences of measurement location, injection pressure, and ambient pressure were discussed in detail. Results showed that although the injection pressure and measurement location have influences on the spray and atomization in both macroscopic and microscopic cases, the ambient pressure plays a more critical effect on it, indicating the low ambient pressure-induced flash boiling spray could improve the atomization much more efficiently

Macroscopic and microscopic characteristics of a single-hole spray under low ambient pressure induced conditions

Flash boiling spray is a promising method to improve atomization, which subsequently affects the combustion phenomenon in engines. Therefore, an investigation on both macroscopic and microscopic characteristics of the flash boiling spray should be done to understand this behavior and mechanism. A mini-sac injector with a single hole was used under different injection pressures among 10, 15, and 20 MPa. Experiments were performed in a constant volume chamber with low ambient pressures varying from 5 to 100 kPa. First, macroscopic behaviors including morphology, spray tip penetration, spray angle, and spray cone angle were compared by a Mie scattering method. Then, microscopic characteristics of flash boiling spray were obtained with the help of particle image analysis technology. In order to analyze the droplet behaviors along the spray axis completely, a spray "slicer" was introduced to filter the spray. The influences of measurement location, injection pressure, and ambient pressure were discussed in detail. Results showed that although the injection pressure and measurement location have influences on the spray and atomization in both macroscopic and microscopic cases, the ambient pressure plays a more critical effect on it, indicating the low ambient pressure-induced flash boiling spray could improve the atomization much more efficiently

Statistical variation analysis of fuel spray characteristics under cross-flow conditions

Owing to cavitation inside the nozzle, spray breakup, and complex flow fields in the cylinder of a spark ignition engine, a certain degree of cycle-to-cycle variation (CCV) remains in different spray cycles under the same operating conditions, thereby affecting the spark ignition engine significantly. Therefore, the effect of cross-flow on the cyclic variation of the spray characteristics is investigated in this work. The CCV of fuel spray characteristics is evaluated via the statistical analysis of 30 repeated experiments under atmospheric pressure. First, the coefficient of variation (COV) is used to assess variations in the spray penetration, area, and optical thickness. Moreover, the effects of injection pressure and cross-flow velocity on the statistical characteristics of the spray are analyzed at the end of injection (EOI). Finally, a dimensionless “Ins number”, which is defined as the parameter of any spray characteristic at a certain time divided by the average experimental value, is proposed to evaluate the spray variation characteristics under cross-flow conditions. Therefore, when the absolute value of the Ins number approaches 1, the CCV of the spray characteristic parameters is low. Results show that the COV of the spray penetration is the largest in the initial stage of injection and then decreases gradually. Meanwhile, the COV of the vertical penetration can be categorized into two stages. Furthermore, it is discovered that the variation in the horizontal penetration is enhanced by the cross-flow and injection pressure at the EOI. In addition, in terms of the COV of the optical thickness, the variation on the windward side is greater, and the cross-flow enhanced the variation in the spray tip region. Most of the Ins numbers of the spray characteristics range from 0.9 to 1.1 (±10%) in this study, and they can provide data support for improving the accuracy of empirical prediction equations and models

RIM Experiment on Fuel Adhesion Characteristics of Inclined-Wall-Impinging Spray under Cross-Flow Conditions

The impingement of fuel sprays on the piston surface significantly affects mixture formation, combustion performance, and pollutant emissions in Direct-Injection Spark-Ignition (DISI) engines. To better understand the fuel adhesion behavior, the fuel adhesion characteristics of fuel spray impinging on the flat wall under cross-flow condition were investigated in this work. Refractive Index Matching (RIM) were employed to observe the propagation of fuel adhesion. Then the area, mass, and thickness of fuel adhesion were evaluated under various cross-flow velocities. Also, the propagation mechanism and lifetime prediction of fuel adhesion under the cross-flow conditions were revealed. The experimental results can provide necessary guidance on the operating conditions of airflow inside the engine

Investigation on fuel adhesion characteristics of wall-impingement spray under cross-flow conditions

The impingement of fuel spray on the piston surface significantly affects the mixture formation, combustion performance, and emissions of a direct-injection spark-ignition (DISI) engine. Therefore, the fuel adhesion characteristics of wall-impingement spray were investigated under cross-flow conditions for in-depth understanding the fuel adhesion behavior in this work. Mie scattering and refractive index matching (RIM) were used to observe the propagation of fuel spray and fuel adhesion, respectively. Subsequently, the area, mass, and thickness of fuel adhesion were evaluated under various cross-flow velocities. The results demonstrated that the cross-flow enhanced the diffusion of fuel spray and fuel adhesion, exhibiting an ellipse propagation. Additionally, the cross-flow also accelerated the volatilization of fuel adhesion, so that the adhesion area and mass decreased with time. Furthermore, the average fuel adhesion thickness obviously decreased under the cross-flow conditions. The fuel adhesion was divided into thick and thin fuel adhesion regions based on the distribution of fuel adhesion. Moreover, the formation and propagation mechanism of the fuel adhesion under cross-flow conditions were revealed. The experimental results can provide an insight into the operating conditions of air-flow inside the engine

Statistical variation analysis of fuel spray characteristics under cross-flow conditions

Owing to cavitation inside the nozzle, spray breakup, and complex flow fields in the cylinder of a spark ignition engine, a certain degree of cycle-to-cycle variation (CCV) remains in different spray cycles under the same operating conditions, thereby affecting the spark ignition engine significantly. Therefore, the effect of cross-flow on the cyclic variation of the spray characteristics is investigated in this work. The CCV of fuel spray characteristics is evaluated via the statistical analysis of 30 repeated experiments under atmospheric pressure. First, the coefficient of variation (COV) is used to assess variations in the spray penetration, area, and optical thickness. Moreover, the effects of injection pressure and cross-flow velocity on the statistical characteristics of the spray are analyzed at the end of injection (EOI). Finally, a dimensionless “Ins number”, which is defined as the parameter of any spray characteristic at a certain time divided by the average experimental value, is proposed to evaluate the spray variation characteristics under cross-flow conditions. Therefore, when the absolute value of the Ins number approaches 1, the CCV of the spray characteristic parameters is low. Results show that the COV of the spray penetration is the largest in the initial stage of injection and then decreases gradually. Meanwhile, the COV of the vertical penetration can be categorized into two stages. Furthermore, it is discovered that the variation in the horizontal penetration is enhanced by the cross-flow and injection pressure at the EOI. In addition, in terms of the COV of the optical thickness, the variation on the windward side is greater, and the cross-flow enhanced the variation in the spray tip region. Most of the Ins numbers of the spray characteristics range from 0.9 to 1.1 (±10%) in this study, and they can provide data support for improving the accuracy of empirical prediction equations and models