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The jet impingement flash technology represents a paramount research subject in the domain of heat and mass transfer. To augment its commercial potential, the conjunction of annular multi‐aperture jet impingement with negative pressure flash evaporation is introduced in this study. The employment of an annular nozzle array is integral to the enhancement of the heat and mass transfer efficiency between the phases. The Realizable k‐ε model is used in this study. The negative pressure flash vaporization model was also developed by introducing a mass source term and an energy source term based on the Mixture model. The flow characteristics are characterized using numerical simulation. Additionally, the λ2 vortex identification criterion is investigated the vortex structure. The simulation results exhibit good agreement with experimental findings, demonstrating that a higher initial vacuum leads to a stronger flashing effect and a more chaotic movement of the flow group within the flow field. Thus, this study provides a reference method for the structural design and optimization of annular symmetric jet impingement negative pressure deammonia chemical equipment for engineering applications. [ABSTRACT FROM AUTHOR]

In order to determine the most suitable turbulence model for studying the aerodynamic performance of bus, the effects of different turbulence models on the aerodynamic characteristics of bus were investigated. A comparative analysis was conducted on five turbulence models (IDDES, DDES, DES, LES, URANS). The pressure distribution on the cross section at x=0 and y=0 is also analyzed for each model. The results reveal that IDDES accurately captures the negative pressure at the rear of the bus and predicts the pressure gradients more effectively than other models. IDDES also captures more vortices at the head of the bus and predicts the wake flow more widely than other models. DDES has obvious shedding phenomenon in the wake flow, while IDDES provides a relatively smooth airflow trajectory, but its prediction of airflow trajectory at a distance is less clear. Through quantitative and qualitative analyses of the aerodynamic characteristics of bus under different turbulence models, it can be concluded that IDDES is the most suitable turbulence model to study the aerodynamic characteristics of bus. [ABSTRACT FROM AUTHOR]

Hydrogen ejectors effectively utilize excess unreacted hydrogen. However, traditional ejectors have limited operational ranges and are only suitable for specific power ranges. This paper presents a dual-nozzle ejector aimed at broadening its operational range through different working modes. A simulation model, validated by experiments, is employed based on the working principles of ejectors. Spiral blades are installed at drive end to improve the recirculation efficiency. Flow characteristics, including streamwise and spanwise vortices at high power, are also investigated in different modes. Results indicate that optimal operating range for Ring-nozzle(RN) mode is between 31.1 and 124.4A. When output current exceeds 124.4A, it is necessary to switch to Central-nozzle (CN) or Double-nozzles (DNs) mode. Analysis of streamlines and velocity vectors reveals that installing spiral blades can modify directions of primary flow. Blades with appropriate distortion should be selected. In CN mode, when stack reaches 60% of rated power, installing 20° spiral blades has a minimal impact on stability of radial flow. Installing 30° or 40° spiral blades is suitable for full-load condition. In DNs mode, installing 30° spiral blades enhances acceleration of gas flow with lower influence from radial influx. This ejector provides assurance for upgrade of fuel cell stacks by incorporating recirculation technology. • A dual-nozzle ejector with spiral guide blades is designed, verified and evaluated. • Installed spiral blades change direction and gather kinetic energy of primary flow. • Advantageous working conditions of different modes with blades are discussed. • Flow mechanism of different blades under high power in two modes is analyzed. • Flow acceleration and losses should be balanced by changing the twist of blades. [ABSTRACT FROM AUTHOR]

In order to determine the most suitable turbulence model for studying the aerodynamic performance of bus, the effects of different turbulence models on the aerodynamic characteristics of bus were investigated. A comparative analysis was conducted on five turbulence models (IDDES, DDES, DES, LES, URANS). The pressure distribution on the cross section at x=0 and y=0 is also analyzed for each model. The results reveal that IDDES accurately captures the negative pressure at the rear of the bus and predicts the pressure gradients more effectively than other models. IDDES also captures more vortices at the head of the bus and predicts the wake flow more widely than other models. DDES has obvious shedding phenomenon in the wake flow, while IDDES provides a relatively smooth airflow trajectory, but its prediction of airflow trajectory at a distance is less clear. Through quantitative and qualitative analyses of the aerodynamic characteristics of bus under different turbulence models, it can be concluded that IDDES is the most suitable turbulence model to study the aerodynamic characteristics of bus.

Multi-principal element alloys (MPEAs) exhibit outstanding strength attributed to the complex dislocation dynamics as compared to conventional alloys. Here, we develop an atomic-lattice-distortion-dependent discrete dislocation dynamics framework consisted of random field theory and phenomenological dislocation model to investigate the fundamental deformation mechanism underlying massive dislocation motions in body-centered cubic MPEA. Amazingly, the turbulence of dislocation speed is identified in light of strong heterogeneous lattice strain field caused by short-range ordering. Importantly, the vortex from dislocation flow turbulence not only acts as an effective source to initiate dislocation multiplication but also induces the strong local pinning trap to block dislocation movement, thus breaking the strength-ductility trade-off. [ABSTRACT FROM AUTHOR]

We propose a method for calculating the kinetics of ultrasonic coagulation of PM2.5 during fine gas cleaning that provides an order of magnitude higher calculation performance. Increased productivity is achieved through the proposed and justified method of reducing the original three-dimensional problem to a two-dimensional one. The proposed reduction method is based on the fact that the time of complete rotation of vortex acoustic flows turns out to be much shorter than the characteristic coagulation time during fine gas cleaning. This makes it possible to present the fractional composition of aerosol particles as a function of two stream functions instead of three coordinates. Calculations carried out using the proposed method make it possible to identify the possibility of increasing the efficiency of coagulation in three-dimensional flows due to the following mechanisms: a local increase in concentration caused by the inertial transfer of particles to the periphery of three-dimensional vortices in the gas phase, increasing the frequency of particle collisions due to three-dimensional turbulent disturbances in ultrasonic fields with a high amplitude of oscillatory velocity (more than 10 m/s), and increasing productivity and ensuring the possibility of continuous implementation of the process in flow mode due to the transfer of particles between the streamlines of the main vortices initiated by ultrasonic vibrations as well as due to external flows perpendicular to the plane of the vortices in three-dimensional space. The developed set of programs for implementing calculations can be used in the design of gas cleaning equipment. [ABSTRACT FROM AUTHOR]