Lactate metabolism promotes in vivo fitness during Acinetobacter baumannii infection.

Acinetobacter baumannii is one of the most prevalent causes of nosocomial infections worldwide. However, a paucity of information exists regarding the connection between metabolic capacity and in vivo bacterial fitness. Elevated lactate is a key marker of severe sepsis.

Impact of Ceramic Micropillar Array and Fiber Layer Composite Structure on Kinematic and Heat Transfer Characteristics of Single Droplet Impacting a Wall.

The well-known limitations of spray cooling on high-temperature solids at the Leidenfrost temperature point have been significantly improved by a composite structure of steel micropillar arrays and insulating thin films. However, the physical mechanism of a single droplet impact on the walls of high-temperature composite structures in spray cooling remains elusive. We have experimentally studied and quantified the kinematic and thermal transfer characteristics of a single droplet impacting high-temperature micropillar arrays with fiber membrane composite structures.

Effects of the Wall Temperature on Rarefied Gas Flows and Heat Transfer in a Micro-Nozzle.

When the satellite is in orbit, the thruster will experience drastic temperature changes (100-1000 K) under solar radiation, which will affect the rarefied gas flow state in the micro-nozzle structure of the cold gas micro-thruster. In this study, the effect of different wall temperatures on the rarefied flow and heat transfer in the micro-nozzle is investigated based on the DSMC method. The micro-nozzle structure in this paper has a micro-channel with a large length-to-diameter ratio of 10 and a micro-scale needle valve displacement (maximum needle valve displacement up to 4 μm).

Direct Simulation Monte Carlo Simulation of the Effect of Needle Valve Structures on the Rarefied Flow of Cold Gas Thrusters.

The needle valve, serving as the flow control unit of the thruster system, is a crucial component of the entire thruster. Its performance directly impacts the flow state of the rarefied gas in the micro-nozzle structure of the cold gas micro-thruster, thereby exerting a significant influence on the high precision and stability of the propulsion system as a whole. This study examines the impact of different needle valve structures on the flow and thrust in micro-nozzles using the DSMC method.

Numerical Study of Flow Boiling of ADN-Based Liquid Propellant in a Capillary.

During the operation of ADN (ammonium dinitramide, (NHN(NO)))-based thrusters, the ADN-based liquid propellant, a non-toxic green energetic material, tends to flow boil in the capillary tube due to heat transfer from the wall. A three-dimensional transient numerical simulation of the flow boiling of ADN-based liquid propellant in the capillary tube was carried out using the VOF (Volume of Fluid) coupled Lee model. The flow-solid temperature and the gas-liquid two-phase distribution and the wall heat flux at different heat reflux temperatures were analyzed.

Effect of Microwave Power and Gas Flow Rate on the Combustion Characteristics of the ADN-based Liquid Propellant.

As a new type of energy-containing material, Ammonium dinitramide based liquid propellant has the advantages of being green, having low toxicity, good stability, and high safety performance. Traditional catalytic combustion methods require preheating of the catalytic bed and deactivation of the catalytic particles at high temperatures, while microwave ignition methods can effectively solve these problems. To study the combustion characteristics of ADN-based liquid propellants during microwave ignition, the influence of microwave power and gas flow rates on the combustion process are analyzed using experimental methods.

Effect of Combustion Chamber Geometrical Parameters on the Decomposition and Combustion Characteristics of an ADN-Based Thruster.

In this paper, numerical simulations were used to study the decomposition and combustion processes inside the 0.2 N-class ADN-based thruster, and the effects of two geometrical parameters (length and diameter) of the combustion chamber on the combustion performance were evaluated. The decomposition and combustion processes of the thruster were simulated using a reduced chemical reaction mechanism with 22 components and 20 reactions steps.

Effects of Heat Reflux on Two-Phase Flow Characteristics in a Capillary of the ADN-Based Thruster.

During the working process of the ADN-based thruster, continuously, heat generated by the chemical reaction in the combustion chamber will transfer along the upstream capillary, the propellant in the capillary continuously absorbs heat under the effect of heat transfer from the wall and undergoes a phase change when the saturation temperature is reached. In this study, effects of the downstream heating temperature (623 K to 923 K) on mass flow rate and pressure change in the capillary were investigated based on the established test platform. Simultaneously, the VOF (volume of fraction) model, and the Lee phase transition model coupled with the Navier-Stokes method was utilized to simulate the spatial distribution of the gas-liquid propellant in the capillary.

Effect of Upstream Valve Opening Process on Dynamic Spray Atomization of Bipropellant Thruster Injector.

In order to develop a new generation of intelligent satellites, fast-response bipropellant thrusters are required to work in minimum impulse mode without limitation. When a valve is opening, the fluctuation affects downstream spray atomization at the injector, which determines the thruster's impulse performance, involving combustion efficiency and impulse repeatability. Accordingly, the spray atomization under impulse working condition was investigated to optimize the thruster's dynamic response.

Experimental Research on Microwave Ignition and Combustion Characteristics of ADN-Based Liquid Propellant.

Microwave ignition has attracted much attention due to its advantages of reliable ignition, large ignition area and cold-start capability. In this paper, the experimental method is used to explore the ignition ability of the microwave device to ADN-based liquid propellant. Additionally, we discuss the influence of the inlet power and rate of propellant injected into the ignition system on the height of the combustion jet and the combustion temperature.

Experimental Study on Microwave-Assisted Ignition and Combustion Characteristics of ADN-Based Liquid Propellant.

Microwave-assisted ignition is a new ignition method, which has the advantages of reliable ignition and high ignition energy and requires no preheating. In this study, experimental methods were used to study the microwave-assisted ignition and combustion characteristics of ADN-based liquid propellant, and the effects of microwave power and propellant flow rate on combustion flame structure, spectral emission characteristics, and flame temperature were investigated. In the experiment, a microwave-assisted ignition experimental device was established first.

Experimental investigation on the characteristics of supersonic fuel spray and configurations of induced shock waves.

The macro characteristics and configurations of induced shock waves of the supersonic sprays are investigated by experimental methods. Visualization study of spray shape is carried out with the high-speed camera. The macro characteristics including spray tip penetration, velocity of spray tip and spray angle are analyzed.