Numerical simulation of water and water emulsion droplets evaporation in flames with different temperatures

The models of heat and mass transfer and phase transition for “water droplet – flame” system have been developed using non-stationary nonlinear partial differential equations. The system of differential equations was solved by the finite-difference method. The locally one-dimensional method was used to solve the difference analogous of differential equations. One-dimensional differential equations were solved using an implicit four-point difference scheme. Nonlinear equations were solved by the iteration method. The evaporation rates of water droplets (with sizes from 0.05 mm to 5 mm) in the flame zone (at the temperatures from 500 K to 1200 K) were determined. Theoretical analysis established essentially nonlinear (close to exponential) form of dependence of the water droplet evaporation rate on the temperature of the external gas area and the temperature of a droplet surface. In particular, the water droplet evaporation rate varies from 0.25 to 0.29 kg/(m2s), when the temperature of external gas area is about 1100 K. On the other hand, the water droplet evaporation rate does not exceed 0.01 kg/(m2s) when the temperature of external gas area is about 350 K. Besides, it has been found out that droplets warm up at different rates depending on their initial temperature and velocity. As a result, the integral characteristics of droplet evaporation can increase substantially, when droplets move through the external gas area at the same temperature. We performed a similar investigation or droplet streams with droplet concentration 0.001–0.005 m3 in 1 m3 of gas area (typical parameters for modern spray extinguishing systems)

Droplet evaporation in water jet at the motion through high temperature gases

Abstract. Heat and mass transfer model for the numerical investigation of the evaporation process of a single droplet in water jet when moving through high temperature gases was developed. The integral characteristics of the process under investigation were calculated. The macroscopic regularities of water droplet evaporation, as elements of jet, in the high temperature gas mixture (as exemplified by combustion products of typical condensed substances) were determined

Evaporation rates of water droplets with soluble and insoluble additives

The relevance. Caused by a wide practical use of water with typical soluble and insoluble additives in the following technologies. They are: thermal and fire purification of liquids, polydisperse fire extinguishing, combustion of waste-derived slurry fuels, cleaning of heat-loaded surfaces, creation of heat agents based on combustion products. Any change in liquid component composition leads to a change in its thermophysical properties, heating rates and phase transformations. So far, there is not enough experimental data on evaporation rates of water droplets with typical soluble and insoluble additives. The aim. Experimental determination of evaporation rate of water droplets with typical additives under various heating methods. The methods. To register sizes of moving droplets, optical registration methods based on a high-speed video camera were used. To register the temperature of combustion products, a measuring complex, consisting of an NI 9219 board and four chromel-alumel fast-response thermocouples, was used. The authors used four methods of droplet heating: in the flow of combustion products with the dominance of convective heat transfer, in a tubular muffle furnace with the dominance of radiative heat transfer, on a solid surface with the dominance of conductive heat transfer, and in a flame with the dominance of mixed (convective and radiative) heat transfer. The results. The authors have determined the ranges of change in evaporation rates of water droplets with typical (soluble and insoluble) additives for various heating methods with the dominance of convective, radiative, and conductive heat transfer. The effect of an additive type and concentration, heating method and heating medium temperature on of droplet evaporation characteristics was established

Water Droplet With Carbon Particles Moving Through High-Temperature Gases

An experimental investigation was carried out on the influence of solid inclusions (nonmetallic particles with sizes from a few tens to hundreds of micrometers) on water droplet evaporation during motion through high-temperature gases (more than 1000 K). Optical methods for diagnostics of two-phase (gas and vapor-liquid) flows (particle image velocimetry (PIV) and interferometric particle imaging (IPI)) were used. It was established that introducing foreign solid particles into the water droplets intensifies evaporation rate in high-temperature gas severalfold. Dependence of liquid evaporation on sizes and concentration of solid inclusion were obtained

A Fast Algorithm Finding the Shortest Reset Words

In this paper we present a new fast algorithm finding minimal reset words for finite synchronizing automata. The problem is know to be computationally hard, and our algorithm is exponential. Yet, it is faster than the algorithms used so far and it works well in practice. The main idea is to use a bidirectional BFS and radix (Patricia) tries to store and compare resulted subsets. We give both theoretical and practical arguments showing that the branching factor is reduced efficiently. As a practical test we perform an experimental study of the length of the shortest reset word for random automata with $n$ states and 2 input letters. We follow Skvorsov and Tipikin, who have performed such a study using a SAT solver and considering automata up to $n=100$ states. With our algorithm we are able to consider much larger sample of automata with up to $n=300$ states. In particular, we obtain a new more precise estimation of the expected length of the shortest reset word $\approx 2.5\sqrt{n-5}$.Comment: COCOON 2013. The final publication is available at http://link.springer.com/chapter/10.1007%2F978-3-642-38768-5_1

Modification of the cylindrical products outer surface influenced by radial beam of argon ions at automatic mode

Obtaining surface with high purity and good roughness is important for increasing the corrosion resistance and wear resistance of products working in corrosion-active environment. Installation ILUR-03 with the coaxial ion beam wide energy spectrum source for cleaning, polishing and surface doping of long cylindrical items has been developed. Upgraded installation ILUR-03 provides effective technological defects cleaning (abrasives after mechanical polishing, acid residues after chemical etching, adsorbed gases), surface polishing, film deposition by using magnetrons and surface doping by ion mixing method in one technological cycle

Using Sat solvers for synchronization issues in partial deterministic automata

We approach the task of computing a carefully synchronizing word of minimum length for a given partial deterministic automaton, encoding the problem as an instance of SAT and invoking a SAT solver. Our experimental results demonstrate that this approach gives satisfactory results for automata with up to 100 states even if very modest computational resources are used.Comment: 15 pages, 3 figure

Coulomb dissociation of N 20,21

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at