Investigation of the Extinguishing Features for Liquid Fuels and Organic Flammable Liquids Atomized by a Water Flow

The processes of heat and mass transfer were investigated experimentally while moving and evaporating the atomized water flow in high-temperature combustion products of typical liquid fuels and organic flammable liquids: gasoline, kerosene, acetone, crude oil, industrial alcohol. We determined typical periods of liquid extinguishing by an atomized water flow of various dispersability. Data of the discharge of extinguishing medium corresponding to various parameters of atomization and duration of using the atomization devices was presented. It is shown that U[m]≈3.5 m/s is a minimal outflow velocity of droplets during moving while passing the distance of 1m in the high-temperature gas medium to stop the combustion of organic liquid

Suppression of forest fuel thermal decomposition under the influence of liquid aerosol and water droplets with additives

This article presents findings of experimental research into suppressing the thermal decomposition of forest fuel (birch leaves, spruce needles, kindling wood and mixed forest fuel) under conditions of exposure water aerosol and single water droplets, as well as water with specialized additives. We used typical model of fire source with fixed height 0.04 m and varied diameter 0.02-0.1m. Water spraying process, as well as interaction between water and forest fuel was registered using highspeed video camera (recording frequency 6∙105 fps) and panoramic optical methods ("Particle Image Velocimetry", "Shadow Photography"). We established principles of water additions' influence on termination of combustion and thermal decomposition of fire source model

Temperature of gases in a trace of water droplets during their motion in a flame

The paper experimentally investigates the integral characteristics of the process¬es involved in the reduction of gas temperature by injecting the aerosol flow of water droplets into a counter flow of combustion products (period of steady low gas temperature, Tg', compared to the initial, Tg, range of temperature decrease (ΔTg = Tg - Tg'), rate of temperature recovery, the geometric dimensions of the temperature traces and their lifetime). We use the following recording devices: fast-response thermocouples (heat inertia less than 0.1 second), a multi-channel recorder, a high speed video camera (up to 105 frames per second), as well as a cross-correlation hardware and software package (with optical methods for re¬cording the front and trace of the aerosol). The temperature trace of an aerosol is defined as the area with the temperature Tg' lower than the initial Tg by at least 10 K. We determine how the following group of factors affects the characteris¬tics of temperature traces of water droplets: size (0.04-0.4 mm) and concentra¬tions (3·10-5-11·10-5 m3 of droplet per m3 of gas) of droplets in a pulse, the ini¬tial temperature of water (280-340 K), the duration of a pulse (1-5 seconds), the temperature (350-950 K) and velocities (0.5-5 m/s) of combustion products. The temperature in a trace of water droplets during their motion in a flame can be reduced due to rapid vaporization or heat exchange between the gases and water. The conditions are identified, under which the low temperature of gases in a trace of droplet aerosol can be preserved for a long time (20-30 seconds). Finally, we forecast the parameters of temperature traces under the conditions of actual fires with combustion product temperatures over 1000 K

Development of the mathematical model of heat and mass transfer for researching the processes of evaporation of inhomogeneous water droplets

On the basis of experimental date the heat and mass transfer models are developed in ANSYS Fluent software package for researching the processes of evaporation of inhomogeneous water droplets. The influence of the temperature of the gases (550-850 K) on the evaporation of inhomogeneous water droplets is estimated. Times of complete liquid evaporation from free surface of inhomogeneous water droplets and explosive vaporization of water droplets at different gas temperatures are established

Development of the mathematical model of heat and mass transfer for researching the processes of evaporation of inhomogeneous water droplets

On the basis of experimental date the heat and mass transfer models are developed in ANSYS Fluent software package for researching the processes of evaporation of inhomogeneous water droplets. The influence of the temperature of the gases (550-850 K) on the evaporation of inhomogeneous water droplets is estimated. Times of complete liquid evaporation from free surface of inhomogeneous water droplets and explosive vaporization of water droplets at different gas temperatures are established

The main reasons of rebound, coagulation, and explosive disintegration of the liquid drops in gas-vapor-droplet streams

We have reviewed the known data about mechanisms, conditions, reasons, and characteristics of rebound, coagulation, and explosive disintegration of drops in gas-vapor-droplet streams. The three main factors of altering a direction of motion, a velocity, a size and a concentration of droplets in a gaseous stream have been highlighted. Among of them are the thermal factor (heating and evaporation of drops), the aerodynamic factor (acceleration, reverse motion, and deceleration of drops due to their entrainment by gaseous stream), the dynamic factor (change in size, velocity, and direction of motion of drops after their collision). We have generalized the findings obtained by various authors in experiments with two drops, little group of drops, and aerosol. In addition, we have reviewed the published results about the fields of velocities and motion trajectories of drops in a flow, about the change in size and concentration of drops due to rebound, coagulation, disintegration (i.e. the complete destruction of the parent drops and the detachment of the liquid fragments of different size and volume from the surface)

Suppression of forest fuel thermal decomposition under the influence of liquid aerosol and water droplets with additives

This article presents findings of experimental research into suppressing the thermal decomposition of forest fuel (birch leaves, spruce needles, kindling wood and mixed forest fuel) under conditions of exposure water aerosol and single water droplets, as well as water with specialized additives. We used typical model of fire source with fixed height 0.04 m and varied diameter 0.02-0.1m. Water spraying process, as well as interaction between water and forest fuel was registered using high-speed video camera (recording frequency 6·105 fps) and panoramic optical methods (“Particle Image Velocimetry”, “Shadow Photography”). We established principles of water additions’ influence on termination of combustion and thermal decomposition of fire source model

The main reasons of rebound, coagulation, and explosive disintegration of the liquid drops in gas-vapor-droplet streams

We have reviewed the known data about mechanisms, conditions, reasons, and characteristics of rebound, coagulation, and explosive disintegration of drops in gas-vapor-droplet streams. The three main factors of altering a direction of motion, a velocity, a size and a concentration of droplets in a gaseous stream have been highlighted. Among of them are the thermal factor (heating and evaporation of drops), the aerodynamic factor (acceleration, reverse motion, and deceleration of drops due to their entrainment by gaseous stream), the dynamic factor (change in size, velocity, and direction of motion of drops after their collision). We have generalized the findings obtained by various authors in experiments with two drops, little group of drops, and aerosol. In addition, we have reviewed the published results about the fields of velocities and motion trajectories of drops in a flow, about the change in size and concentration of drops due to rebound, coagulation, disintegration (i.e. the complete destruction of the parent drops and the detachment of the liquid fragments of different size and volume from the surface)

Suppression of forest fuel thermal decomposition under the influence of liquid aerosol and water droplets with additives

This article presents findings of experimental research into suppressing the thermal decomposition of forest fuel (birch leaves, spruce needles, kindling wood and mixed forest fuel) under conditions of exposure water aerosol and single water droplets, as well as water with specialized additives. We used typical model of fire source with fixed height 0.04 m and varied diameter 0.02-0.1m. Water spraying process, as well as interaction between water and forest fuel was registered using high-speed video camera (recording frequency 6·105 fps) and panoramic optical methods (“Particle Image Velocimetry”, “Shadow Photography”). We established principles of water additions’ influence on termination of combustion and thermal decomposition of fire source model

Water drops with graphite particles triggering the explosive liquid breakup

We have established conditions for stable triggering of the explosive breakup for heterogeneous water drops induced by immersion in high-temperature gas (air) at more than 800 K. The water drop heating is enhanced by small graphite solid particles of 2 × 2 × 1 mm, 2 × 2 × 2 mm and 2 × 2 × 3 mm inserted into drops. The properties of the graphite such as porous and layered structure, moisture content, and surface roughness play determining roles. Experiments show that heterogeneous water drops can boil during a short time and produce clouds of tiny droplets. Heating times of heterogeneous drops until the breakup do not exceed a few seconds and usually last for less than three. We have identified the main stages and the mechanism of heterogeneous drop heating, as well as vaporization at the internal interface and at the free surface of a drop. A high-speed video camera and the TEMA Automotive Software with a number of tracking algorithms are used for measurements. The analysis of experimental results shows that during the fragmentation of large heterogeneous drops at high temperatures, more than 100 small droplets are formed. The obtained data are a basis for novel technologies of effective fire extinguishing that involve the multiple growth of water evaporation area in a flame.SCOPUS: ar.jinfo:eu-repo/semantics/publishe