38 research outputs found

    Droplet Vaporization Law in Non-Dilute Sprays

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    Numerical Simulation of an Aerothermopressor with Incomplete Evaporation for Intercooling of the Gas Turbine Engine

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    Numerical Simulation of an Aerothermopressor with Incomplete Evaporation for Intercooling of the Gas Turbine Engine / H. Kobalava , D. Konovalov, R. Radchenko, S. Forduy, V. Maksymov // Integrated Computer Technologies in Mechanical Engineering – 2020 : ICTM 2020. Lecture Notes in Networks and Systems, vol. 188 / M. Nechyporuk, V. Pavlikov, D. Kritskiy. – Kharkiv, Ukraine, 2021. – P. 519–530.Complex cycles with cyclic air intercooling are used to increase the energy efficiency of gas turbines. A modern and widespread way to improve the cooling process is to humidify the working fluid (cyclic air). The efficiency of wet compression primarily depends on the intensity of evaporation and heat exchange of droplets with the air flow, which begins to increase sharply when the effective diameter of droplet spraying decreases to 20 lm. It is proposed to use a contact heat exchanger to obtain a finely dispersed flow of water in the flow path of a gas turbine. The operation of such contact heat exchanger called aerothermopressor was investigated in this paper. CFD simulation of the water droplet evaporation process in the aerothermopressor airflow was carried out. Calculations were carried out for three variants of evaporation of water injected into the air flow: complete evaporation of water droplets in the evaporation chamber, additional evaporation of water droplets in the diffuser and incomplete evaporation, with obtaining smaller droplets at the outlet of the aerothermopressor diffuser. Efficiency of the aerothermopressor application in the gas turbine circuit for contact cooling of cyclic air is analyzed. It has been revealed that the aerothermopressor allows increasing the cyclic air pressure between the compressor stages by 2–10%, which will lead to a decrease in the compression work in the compressor stages and makes it possible to increase the gas turbine engine efficiency by 1–2%

    Lagrangian measurements of the fast evaporation of falling diethyl ether droplets using in-line digital holography and a high-speed camera

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    International audienceThe evaporation of falling diethyl ether droplets is measured by following droplets along their trajectories. Measurements are performed at ambient temperature and pressure by using in-line digital holography. The holograms of droplets are recorded with a single high-speed camera and reconstructed with an ''inverse problems'' approach algorithm previously tested (Chareyron et al. New J Phys 14:43039, 2012). Once evaporation starts, the interfaces of the droplets are surrounded by air/vapor mixtures with refractive index gradients that modify the holograms. The central part of the droplets holograms is unusually bright compared to what is expected and observed for non-evaporating droplets. The reconstruction process is accordingly adapted to measure the droplets diameter along their trajectory. The diethyl ether being volatile, the droplets are found to evaporate in a very short time: of the order of 70 ms for a 50-60 lm diameter at an ambient temperature of 25 C. After this time, the diethyl ether has fully evaporated and droplets diameter reaches a plateau. The remaining droplets are then only composed of water, originating from the cooling and condensation of the humid air at the droplet surface. This assertion is supported by two pieces of evidence: (i) by estimating the evolution of droplets refractive index from light scattering measurements at rainbow angle and (ii) by comparing the evaporation rate and droplets velocities obtained by digital holography with those calculated with a simple model of evaporation/condensation. The overall results show that the in-line digital holography with ''inverse problems''approach is an accurate technique for studying fast evaporation from a Lagrangian point of view
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