Browse Topic: Gases
American drivers have long been accustomed to quickly filling up at a gas station with plenty of fuel available, and electric vehicle drivers want their pit stops to mimic this experience. Driver uncertainty about access to charging during long trips remains a barrier to broader EV adoption, even as the U.S. strives to combat climate change by converting more drivers
To understand effect of thermal hazards of LIBs during TR event, it is important to study flame propagation behaviour of LIBs during storage and transport applications. The process of flame propagation involves complex phenomena of gas phase behavior of LIBs. Present paper attempts a numerical investigation to portray this complex phenomenon. This paper investigates 18650 lithium cell considering two different chemistries NMC and LFP. A 3D numerical CFD model has been constructed to predict the gas phase behavior, threshold internal pressure, and cell gas venting of an 18650-lithium cell under thermal runaway conditions. The gas phase processes are modelled using the 4-equation thermal abuse model, while the cell's venting mechanism is modelled using Darcy's equation. Present work is divided into two parts: 1) Venting gas Internal pressure prediction 2) modeling thermal runaway event. Both procedures are implemented on two different cell chemistries to understand and evaluate following
If an external force with changing amplitude acts on an elastic medium such as a gas, a liquid or a solid, an undulating propagation of pressure and density fluctuation occurs in space and time, starting from the point where the force is applied. This is known as sound. The frequency of sound waves ranges from a few hertz (Hz) up to several gigahertz (see Figure 1). Infrasound, the sound humans cannot hear, lies at frequencies below 16 Hz. It is followed by the hearing range, which reaches up to 20 kHz. Ultrasonic waves, which cannot be heard, lie in the frequency range from 20 kHz to 1.6 GHz, which equals 16 billion cycles per second. A prominent application example in medical technology is the use of ultrasound for diagnostic imaging techniques. In industry and research, ultrasound is mainly used in measurement technology, where sound waves with low power are used. The intensity of the sound describes the power that hits a certain surface. If it exceeds 10 W/cm2, we speak of power
The study demonstrates the possibility and in particular the method to derive the efficiency of the entire fuel cell power system by measuring specific data of the recirculation path of the anode circuit of a fuel cell system. The results demonstrate the capabilities of the existing test rig and enable investigations on the suitability of auxiliary components. This study focuses on the hydrogen recirculation path equipped with multiple sensors and a needle valve to enable the required operating conditions of the fuel cell. Running a startup load profile without reaching the equilibrium state at all steps, the dynamic of the system and the requirements to the sensor parameters, such as sampling rate and precision, was seen. Additionally, it became obvious that the recirculation pump used is oversized, but a load point shift compensated this artifact. In detail, the stoichiometry and the efficiency of the entire system was evaluated. It was seen that the hydrogen concentration is
Water removal from Proton Exchange Membrane (PEM) Fuel Cell (FC) mainly involves two phenomena: some of the emerging droplets will roll on the Gas Diffusion Layer (GDL), others may impact channel walls and start sliding along the airflow direction. This different behaviour is linked to the hydrophobic/hydrophilic nature of the surface the water is moving on. In this paper, the walls of the channel of a FC were characterized by applying optical techniques. The deposition of droplets on the channel wall led to an evaluation of the proper range for Contact Angle Hysteresis (CAH = 55° - 45°), and due to the high wettability of the surface, droplets dimension was defined with a dimensionless parameter B/H. Under high crossflow condition (15 m/s) a sliding behaviour was observed. The channel features determined through image processing were used as boundary conditions for a 2D CFD two phase simulation employing the Volume of Fluid (VOF) model to keep track of the fluids interface. A droplet
Small mobile robots carrying sensors could perform tasks like catching gas leaks or tracking warehouse inventory. But moving robots demands a lot of energy, and batteries, the typical power source, limit lifetime and raise environmental concerns. Researchers at the University of Washington have now created MilliMobile, a tiny, self-driving robot powered only by surrounding light or radio waves
Although progress has recently been made to characterise the transition of microscopic liquid fuel droplets from classical evaporation to a diffusive mixing regime, still little is known about the transition from one to the other under reactive conditions. The lack of experimental data for microscopic droplets at realistic operating conditions impedes the development of phenomenological and numerical models for droplet mixing, ignition, combustion and soot formation. In order to address this issue we performed systematic measurements using high- speed long-distance microscopy, for n-dodecane into gas at elevated temperatures (from 750 to 1,600 K) and pressures up to 13 MPa. We describe these high- speed visualizations at the microscopic level, including the time evolution of the liquid droplets, reaction wave, and soot distribution. Our measurements show that these parameters are influenced by the operating conditions (gas pressure, gas temperature, oxygen content) as well as the
A presentation of work comparing efficacy of a traditional IR method used as a standard within the U.S. Army Combat Capabilities Development Command (DEVCOM) and by international collaborators with that of an emerging technology, cavity ring down spectroscopy (CRDS). Army Combat Capabilities Development Command, Aberdeen Proving Ground, MD A threat in the form of chemical vapor may not be visible, but rapid detection is critical for preservation of life and property. In addition, understanding the surrounding environment informs the posture that the warfighter will need to take. The field of chemical vapor detection spans far beyond the warfighter and is rich in research. A search in SciFinder for “chemical vapor detection” provides over 400,000 results with over 3,000 books, 26,000 reviews, and nearly 300,000 journal articles. The focus of this document will be with an eye towards perimeter monitoring for a wide range of gas-phase chemicals. To accomplish such sensing, compound
This SAE Standard provides the testing and functional requirements guidance necessary for a leak detection device that uses any non-A/C refrigerant tracer gas, such as helium or a nitrogen-hydrogen blend, to provide functional performance equivalent to a refrigerant electronic leak detector. It explains how a non-refrigerant leak detector’s calibration can be established to provide levels of detection equal to electronic leak detectors that meet SAE J2791 for R-134a and SAE J2913 for R-1234yf
In this paper, an innovative EGR valve, containing an integrated self-cleaning function to mitigate the progressive buildup of carbon deposits, is described. Conventional EGR valves use Butterfly and Poppet mechanisms to open and close a round shaped exhaust gas port with limited ability to remove exhaust carbon deposits from the affected surfaces and mechanical elements. The self-cleaning EGR valve, instead, combining both rotational and linear motions, continuously sweeps its internal passages while delivering the gas flow, removing the carbon deposits before they can adhere to the internal surfaces
Ionospheric variability is a critical consideration for communication systems, GNSS, and space asset management. At high magnetic latitudes, the convergent magnetic field acts as a lens, focusing electromagnetic power originating from solar wind-magnetosphere interactions into a limited latitudinal range. The geometry and ensuing complex coupling processes result in extreme multi-scale time-dependent variations in the structure and composition of the ionized gases in Earth’s outer atmosphere. Understanding the mechanisms and technological consequences of these interactions benefits from distributed heterogeneous time-dependent measurements of the ionosphere-thermosphere-magnetosphere system, and their application as constraints on predictive space weather models
The main gases released by volcanoes are water vapor, carbon dioxide, and sulfur dioxide. Analyzing these gases is one of the best ways of obtaining information on volcanic systems and the magmatic processes that are underway. The ratio of carbon dioxide levels to those of sulfur dioxide can even reveal the likelihood of an impending eruption. Drones are employed to carry the necessary analytical systems to the site of activity. However, because of their size, transporting the drones to their operation sites has to date required significant expense
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