Самопроизвольное (спонтанное) вскипание затопленных струй, генерируемых при коллапсе паровых пузырьков

The effect of secondary spontaneous boiling of submerged jets formed during the collapse of vapor bubbles during the bulk boiling of water subcooled to the saturation temperature at the end of a laser optical fiber is experimentally discovered.

Study of the working process of a diesel engine with modified fuel

The research objective is to reduce specific fuel consumption and emissions of exhaust fume pollutants. Specifically treated (modified) fuel is used to comprehensively improve the economic and environmental performance of the diesel operation process. Fuel treatment was carried out at a pilot plant using the process of fuel gas cavitation. During processing, high-molecular fuel compounds were broken down and the fuel was saturated with gas-vapor bubbles. The description of the pilot unit is given. The characteristics of the base distillate and modified fuel are studied. A mathematical model and the numerical study results of the fuel droplet development containing vapor-gas bubbles are presented. An experimental study of the work process in a 10.5/12 H diesel engine single-cylinder compartment when operating on various fuels was carried out. Diesel tests have shown that when using modified fuel, the specific indicative fuel consumption has decreased by 5-7 per g / kWh, the exhaust gas temperature has decreased by 5-8 degrees, the concentration of nitrogen oxides in the exhaust fumes has decreased by 32-46 ppm, the concentration of total hydrocarbons has decreased by 9-14 ppm, the smoke content has decreased by 1.2-1.7 times.

Collisions of Two-Phase Liquid Droplets in a Heated Gas Medium

The paper presents the experimental research findings for the integral characteristics of processes developing when two-phase liquid droplets collide in a heated gas medium. The experiments were conducted in a closed heat exchange chamber space filled with air. The gas medium was heated to 400–500 °C by an induction system. In the experiments, the size of initial droplets, their velocities and impact angles were varied in the ranges typical of industrial applications. The main varied parameter was the percentage of vapor (volume of bubbles) in the droplet (up to 90% of the liquid volume). The droplet collision regimes (coalescence, bounce, breakup, disruption), size and number of secondary fragments, as well as the relative volume fraction of vapor bubbles in them were recorded. Differences in the collision regimes and in the distribution of secondary fragments by size were identified. The areas of liquid surface before and after the initial droplet breakup were determined. Conditions were outlined in which vapor bubbles had a significant and, on the contrary, fairly weak effect on the interaction regimes of two-phase droplets.

Studying of the characteristics of a single bubble under subcooled liquid boiling

An experimental study of the characteristics of single (solitary) bubbles obtained by means of focused laser heating of the surface during the boiling of two subcooled liquids with significantly different properties: water and refrigerant R113 has been carried out. To obtain the most complete detailed information, the technique of synchronized high-speed video filming of the process in two mutually perpendicular planes with a frame rate of up to 150 kHz was used. It is shown that during the boiling of a subcooled liquid, the main mechanism of heat removal from the bubble dome into the surrounding liquid is an unsteady heat conductance. Differences in the behavior of solitary vapor bubbles in the case of boiling of two liquids (water and refrigerant R113) are shown.

Experimental Observation of Nucleate Boiling Entrainment in a Liquid Film

Many studies have been conducted on droplet entrainment in an annular flow regime, but little is known about droplet entrainment caused by nucleate boiling. In this report, visualization results of droplet entrainment caused by nucleate boiling are described. We observed two processes of droplet entrainment. The first one causes bubble bursting at a water surface. The second one causes filament breakup which occurs when the vapor bubble reaches and collapses at the interface between air and liquid. From comparison of the phenomena for the two processes, we found that the diameters of the droplets and vapor bubbles were considerably different. Using the results of this research allows the effect of forced convection to be taken into account. In the future, we plan to expand the amount of data and develop a boiling entrainment model under forced convection conditions.

Reconciling early Deccan Traps CO2 outgassing and pre-KPB global climate

A 2 to 4 °C warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the Cretaceous–Paleogene boundary (KPB) mass extinction at 66.05 ± 0.08 Ma and has been linked with the onset of voluminous Deccan Traps volcanism. Here, we use direct measurements of melt-inclusion CO2 concentrations and trace-element proxies for CO2 to test the hypothesis that early Deccan magmatism triggered this warming interval. We report CO2 concentrations from NanoSIMS and Raman spectroscopic analyses of melt-inclusion glass and vapor bubbles hosted in magnesian olivines from pre-KPB Deccan primitive basalts. Reconstructed melt-inclusion CO2 concentrations range up to 0.23 to 1.2 wt% CO2 for lavas from the Saurashtra Peninsula and the Thakurvadi Formation in the Western Ghats region. Trace-element proxies for CO2 concentration (Ba and Nb) yield estimates of initial melt concentrations of 0.4 to 1.3 wt% CO2 prior to degassing. Our data imply carbon saturation and degassing of Deccan magmas initiated at high pressures near the Moho or in the lower crust. Furthermore, we find that the earliest Deccan magmas were more CO2 rich, which we hypothesize facilitated more efficient flushing and outgassing from intrusive magmas. Based on carbon cycle modeling and estimates of preserved lava volumes for pre-KPB lavas, we find that volcanic CO2 outgassing alone remains insufficient to account for the magnitude of the observed latest Maastrichtian warming. However, accounting for intrusive outgassing can reconcile early carbon-rich Deccan Traps outgassing with observed changes in climate and atmospheric pCO2.

Insights from the Depths of Hawaii’s Kīlauea Volcano

One of the world’s best monitored and most active volcanos still has secrets to yield, and researchers are turning to vapor bubbles trapped in melt inclusions to find them.