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Measurement fundamentals and instrumentation
Published in Raymond F. Gardner, Introduction to Plant Automation and Controls, 2020
The simplest level measurements are gage glasses, sampling petcocks, and sounding tubes that use measuring tapes, as shown in Figure 1.26. With gage glasses, the level is directly observed. Sounding tubes use bobs attached to a measuring tape. A plumb bob directly measures the liquid height, where chalk may be applied to the tape to highlight wetting by clear fluids. The ullage bob is lowered using jerking motions, so that its cupped end makes a popping sound on the liquid surface, measuring the ullage distance, which is the clearance above the surface to the top of the sounding tube. Measuring ullages is good for messy fluids, such as oil. Petcocks or try cocks are used for harmless fluids, like water, by opening the valves until the fluid issues.
Subsonic Transport Aircraft
Published in G. Daniel Brewer, Hydrogen Aircraft Technology, 2017
The thermal model used in the concept screening phase was developed as a closed form type of solution which considers the heat transfer in both the liquid and vapor phases present in the tank as a function of liquid fraction, vapor and liquid-wetted wall heat fluxes, exterior temperature, and tank wall and insulation thermal properties. Net heat input to the liquid (the source of vapor generation) is a function of heat transfer across the liquid-wetted portion of the tank wall, through the liquid/vapor interface, and down the tank wall from the ullage to the liquid region. Radiation from the ullage portion of the tank wall to the liquid was also included. The model is illustrated in Figure 4–75.
Tanker Operations
Published in David House, Seamanship Techniques, 2019
The function of the gauge (Figures 19.3 and 19.4) is to register the ullage of the tank at any given time, in particular when the liquid level in the tank is changing during loading or discharging. The gauge is designed to record not only at the tank top, but also in a central control room, a transmitter being fitted to the gauge head for this purpose. A particularly useful addition to oil tankers with numerous tanks, it allows the reading of all tanks to be carried out at one central control room.
Experimental and numerical investigation of the aircraft fuel tank inerting system
Published in Australian Journal of Mechanical Engineering, 2023
The fuel tank inerting system operates throughout all stages of the aircraft’s flight envelope. During the ground preparation stage, NEA is introduced into the fuel tank for the initial inerting process. In this stage, the oxygen concentration within the fuel tank decreases from 21% to a level below the safe oxygen concentration. During the climbing phase, as the flight altitude increases, the pressure inside the fuel tank becomes higher than that of the ambient. Consequently, the gas inside the fuel tank begins to exhaust, causing a decrease in the pressure of the ullage. This will lead to the gas within the fuel escaping into the ullage. Since the escape rate of oxygen in fuel is higher than of nitrogen, the oxygen concentration in the tank increases. To maintain pressure and safe oxygen concentration, NEA needs to be supplemented. During the cruise stage, the pressure in the fuel tank ullage decreases with the consumption of fuel. Therefore, continuous supplementation of NEA is required to maintain the desired pressure and oxygen concentration within the fuel tank. During the descending stage, the ambient pressure continues to increase, surpassing the pressure inside the fuel tank. This pressure difference causes ambient air to flow into the fuel tank through the vent valve, resulting in an increased oxygen concentration of the tank ullage. In this stage, NEA should also be injected into the fuel tank to maintain a safe oxygen concentration level.
Burning characteristics and soot formation in laminar methyl methacrylate pool flames
Published in Combustion Theory and Modelling, 2020
Dakshnamurthy Shanmugasundaram, Selvaraj Muthu Kumaran, Stanislav A. Trubachev, Anna Bespalova, Oleg P. Korobeinichev, Andrey G. Shmakov, Vasudevan Raghavan
Multi-component diffusion along with thermal diffusion and diffusion energy source are included. Temperature and concentration dependent thermo-physical properties, SIMPLE algorithm and second-order upwind schemes are incorporated. A comprehensive chemical kinetic mechanism for MMA – air, consisting of 49 species and 376 reactions [11], is used. The mechanism is provided in the supplementary material. Since a given ullage is maintained by supplying the fuel at the rate with which it is burning, a quasi-steady burning regime is obtained. In this, the liquid-phase is not solved. Interface coupling conditions at the pool interface are solved iteratively to determine the MMA vapour velocity and mole fraction at the pool interface. Thermodynamic equilibrium is used and the mole fraction of the fuel vapour at the interface is obtained by Clausius–Clapeyron equation. Fick’s law considering convection and ordinary diffusion is used to model the transport of the fuel vapour from the interface to the gas-phase. The heat incident on the interface from the gas-phase through conduction feeds the latent heat required for the liquid to evaporate and internal heat conduction into the liquid, calculated using a bulk formulation considering the interface and bottom temperatures and the liquid height. The radiative heat transfer to the liquid pool has been neglected in this study since the liquid emissivity is low [18]. These coupled interface equations are presented in Equations (1–3).