Flash Boiling Research Articles

EXPERIMENTAL STUDY ON FLASH BOILING SPRAY OF HIGH-PRESSURE LIQUID AMMONIA JET WITH ROUND AND ELLIPTICAL HOLE NOZZLES

Ammonia is an ideal alternative fuel for mitigating carbon emissions. High-pressure direct injection of liquid ammonia (LNH<sub>3</sub>) offers significant advantages in enhancing energy efficiency and minimizing emissions. Due to the high saturation vapor pressure, the injection of LNH<sub>3</sub> is susceptible to flash boiling. In this study, we used high-speed micro-imaging technology with backlight lighting to establish a high-pressure common-rail LNH<sub>3</sub> jet experimental platform and investigate the flash boiling spray characteristics of nozzles with round and elliptical holes. The results demonstrated that under non-flash boiling conditions, the residual LNH<sub>3</sub> in the sac chamber and nozzle can rapidly corrode the acrylic material of the nozzle, leading to deformation and failure of the nozzle structure. Under flash boiling conditions, LNH<sub>3</sub> ejected from the hole will produce spherical macroscopic spray morphology. Then, the spray gradually transitions from an elliptical profile to a conical profile as the back pressure increases. Compared to nozzles with round holes, nozzles with elliptical holes exhibit higher flow velocity, which enhances oil-gas mixing and promotes more pronounced flash boiling phenomena. Flash boiling occurs at an earlier stage with an increase in the spray cone angle, thereby improving the atomization characteristics under both flash and non-flash boiling conditions. The tail jet of nozzles with elliptical holes terminates earlier while exhibiting a higher decrease rate in the average gray value, which improves the atomization quality in the tail spray stage and meets the requirements of timing, quantification, and precise control of the fuel injection system.

ABOUT THE MORPHOLOGY OF FLASH BOILING LIQUID NITROGEN SPRAYS

ABOUT THE MORPHOLOGY OF FLASH BOILING LIQUID NITROGEN SPRAYS

CRYSTALLIZATION OF A NaCl SOLUTION IN A VACUUM CENTRIFUGAL FILM DISTILLER

Проблематика. Использование центробежных сил в теплообменных аппаратах обеспечивает высокую эффективность процессов тепломассообмена и позволяет создать аппараты, которые работоспособны в условиях микрогравитации, характерных для космических аппаратов. Малое время контакта раствора с теплообменной поверхностью предупреждает отложение растворенных веществ при повышении концентрации раствора. В результате центробежный дистилляционный аппарат может работать в режиме кристаллизатора, что обеспечивает увеличение коэффициента регенерации воды в системах жизнеобеспечения пилотируемых космических аппаратов. Цель исследования. Исследование работы одноступенчатого центробежного дистиллятора взрывного вскипания при концентрировании раствора NaCl. Методика реализации. Экспериментальные исследования на опытном образце центробежного вакуумного одноступенчатого дистиллятора. Результаты исследования. Получены результаты при концентрировании раствора NaCl, в т.ч. в режиме кристаллизации (когда начинается выпадение растворенных кристаллов NaCl). Определена физико-химическая температурная депрессия в зависимости от концентрации раствора и давления в аппарате с контролем качества полученного дистиллята. Проведено сравнение полученных результатов с данными других авторов. Показано хорошее совпадение. Использование фильтра в горячем контуре позволяет работать в режиме кристаллизатора без появления отложений на конструктивных элементах аппарата. Выводы. Интенсивный теплообмен в центробежном аппарате обеспечивает полное срабатывание перегрева раствора, что позволяет использовать его для изучения физико-химической температурной депрессии растворов при разных давлениях. При этом качество дистиллята не зависит от концентрации растворенных веществ в горячем контуре (в т.ч. в режиме кристаллизации). Использование фильтра в горячем контуре обеспечивает возможность работы системы в режиме кристаллизатора до забивания фильтра. После замены фильтра процесс может быть продлен.

Flash Boiling in Sprays: Recent Developments and Modeling

This study aims to cover the modeling of flash boiling effects in the sprays. There is a lack of an economical and computationally efficient methodology to analyze this complex phenomenon. Flash boiling being an essential phenomenon in combustion engines is the cause of change in the spray structure, cone angle, liquid penetration length, droplet distribution, etc. The paper revisits various models used to capture the effect of the flash boiling phenomenon and identifies the drawbacks and challenges, respectively. The whole phenomenon is divided into various stages and discussed stepwise. It tries to address the issues related to the gaps in modeling.

Initiation of Flash Boiling of Multicomponent Miscible Mixtures with Application to Transportation Fuels and Their Surrogates

This paper presents methodologies to predict thermodynamic conditions that initiate flash boiling by spontaneous nucleation of liquids consisting of hundreds of miscible liquids and their lower order surrogate mixtures. The methods are illustrated with a kerosene-based fuel and a seven-component surrogate for it. The predictions are compared to measurements of nucleation temperatures obtained from a pulse-heating technique that rapidly heats a microscale platinum film immersed in a pool of the test fluid. Nucleation temperatures are predicted using a generalized corresponding states principle (GCSP), and a modification of classical nucleation theory that considers the mixture as a pseudo single component fluid (PSCF). The intent is to offer a simple means to predict the initiation of flash boiling that can have important consequences for fuel efficiency in combustion engines. We show that contact angle has a strong effect such that predicted and measured spontaneous nucleation temperatures agree for a giv...

A Summary of Findings of the Subcooled Liquid Flash Boiling Cycle and its Applications to Automotive Waste Heat Recovery.

A Summary of Findings of the Subcooled Liquid Flash Boiling Cycle and its Applications to Automotive Waste Heat Recovery.

CFD Simulation of Flash Boiling of Supercritical Pentane during Asphalt Granulation

We consider a technology for granulation of asphalt from its mixture with supercritical pentane and construct a mathematical model for the process. We compare two nozzle designs intended for spraying the mixture and flash boiling of pentane. We show that a nozzle with a conical section is not susceptible to clogging by the asphalt. The pentane vaporization rate and the fraction of vapor phase increase owing to the presence of the asphalt phase.

Flash Boiling: Easy and Better Way to Generate Ideal Sprays than the High Injection Pressure

Flash Boiling: Easy and Better Way to Generate Ideal Sprays than the High Injection Pressure

4830 DME減圧沸騰噴霧特性に関する研究 : 第2報:臨界温度・圧力以上の噴霧特性(J10-3 次世代燃料及び潤滑油のためのエンジン適合技術(3),J10 次世代燃料及び潤滑油のためのエンジン適合技術)

4830 DME減圧沸騰噴霧特性に関する研究 : 第2報:臨界温度・圧力以上の噴霧特性(J10-3 次世代燃料及び潤滑油のためのエンジン適合技術(3),J10 次世代燃料及び潤滑油のためのエンジン適合技術)

The Influence of Orifice Size on the Mass Flow During Flash Boiling of HCFC-22 From a Small Vessel

An experimental investigation was conducted to study the flash boiling process and the influence of the exiting restriction (orifice) size on the mass flow during flash boiling of HCFC-22 in a glass pressure vessel. An apparatus was built and a combination of tests were run with three interchangeable exiting orifices (1.59, 3.18, and 5.56 mm diameters). The flashed vapor was vented from a 1110-mL vessel to a large “semi-infinite” tank initially set at 120 kPa. Calculations revealed that the refrigerant flow exiting the vessel was choked, depending on the orifice size. Smaller orifices were choked longer, had slower depressurization rates, and reduced mass flow rates. The depressurization rates were greater for tests large offices which enabled the liquid to become more highly superheated, up to 41°C for one test case, and ultimately vaporize more refrigerant.