Preserved boreal zone forest massif mass estimation during fire extinguishing by liquid aerosol

This study contains results of experimental studies into establishing the principles of decreasing the model of fire source mass when extinguishing the ground cover of deciduous and mixed forests by liquid aerosol. The experiments were carried out with typical forest fuels - birch leaves and mixed non-living components of temperate forest. Densities of forest fuel samples in a model of fire source were variated in the corresponding real practice ranges: 20.26–54.70 kg/m{3} for birch leaves and 27.54–72.18 kg/m{3} for a mixed forest fuel. Dimensions of droplets generated by the nozzle amounted to 0.01–0.12 mm. It is consistent with modern aerosol fire extinguishing systems. The dependence of the initial forest fuel sample mass on the remaining mass after ending of the pyrolysis reaction was established

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

Heat and Mass Transfer at Hot Surface Ignition of Coal Particle

This paper describes the experimental investigations of the characteristics of heat and mass transfer during the conductive heating of a coal particle. We have established the boundary conditions of combustion initiation, and the conditions of thermal decomposition and solid fuel particles decay, characterized by the temperature of a heat source, and the duration of the respective stages

Igniting Soaring Droplets of Promising Fuel Slurries

High rates of environmental pollution by boilers and thermal power plants burning coal of different grades are the main reason for active research in the world aimed at the development of alternative fuels. The solution to the formulated problem acceptable in terms of environmental, technical and economic criteria is the creation of composite slurry fuels with the use of fine coal or coal processing and enrichment waste, water of different quality, and oil sludge additive. This study considers modern technologies of burning slurry fuels as well as perspective research methods of the corresponding processes. A model combustion chamber is developed for the adequate study of ignition processes. The calculation of the basic geometric dimensions is presented. The necessity of manufacturing the combustion chamber in the form of an object of complex geometry is substantiated. With its use, several typical modes of slurry fuel ignition are determined. Principal differences of ignition conditions of a single droplet and group of fuel droplets are shown. Typical vortex structures at the fuel spray injection are shown. A comparison with the trajectories of fuel aerosol droplets in real combustion chambers used for the combustion of slurry fuels is undertaken

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)

Secondary Atomization of Fuel Oil and Fuel Oil/Water Emulsion through Droplet-Droplet Collisions and Impingement on a Solid Wall

This paper presents findings from an experimental study investigating the secondary atomization of liquid fuel droplets widely used in the heat and power industry exemplified by fuel oil and environmentally promising fuel oil/water emulsion. The scientific novelty comes from the comparative analysis of the critical conditions and integral characteristics of the secondary atomization of the liquid and composite fuels with the greatest potential for power plants. Here, we used two fuel atomization schemes: droplet–droplet collisions in a gas and droplets impinging on a heated solid wall. The temperature of the liquids under study was 80 °C. The velocities before collision ranged from 0.1 m/s to 7 m/s, while the initial droplet sizes varied from 0.3 mm to 2.7 mm. A copper substrate served as a solid wall; its temperature was varied from 20 °C to 300 °C. The main characteristics of droplet interaction were recorded by a high-speed camera. Regime maps were constructed using the experimental findings. It was established that the critical Weber number was several times lower when water and fuel oil droplets collided than during the collision of fuel oil droplets with 10 vol% of water. The secondary atomization of fuel oil/water emulsion droplets by their impingement on a heated solid wall was found to reduce the typical sizes of liquid fragments by a factor of 40–50. As shown in the paper, even highly viscous fuels can be effectively sprayed using primary and secondary droplet atomization schemes. It was established that the optimal temperature of the fuel oil to be supplied to the droplet collision zone is 80 °C, while the optimal substrate temperature for the atomization of fuel oil/water emulsion droplets approximates 300 °C

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)

Analysis of statistical data on drop collisions in an aerosol flow during experiments

The study presents a software code developed by using Mathematica. This code allows the automatic analysis of breakup consequences of heterogeneous drops. Moreover, we show how statistical data on drop collisions in a sprayed aerosol flow can be collected using this code. For this purpose, we have compared results of manual handling of video with automatic one