Autoignition and combustion of water-fuel emulsion during its injection into heated air. III. Completeness of combustion of fuel oil M-40

The dependence of the completeness of combustion of liquid fuel during its pulsed injection into heated air on the parameters of the medium and delivery conditions was established experimentally and it is shown that emulsification of the fuel does not affect the integral completeness of combustion. Therefore, an increase of fuel economy of diesel engines on converting them to a water-fuel emulsion can be achieved only due to a favorable change in the dynamics of the cycle. Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 5, pp. 3–11, September–October, 1995.     

Autoignition and burning of a water-oil emulsion with its injection into heated air. I. Ignition lag of diesel fuel DL

The effect of the degree of emulsifying diesel fuel DL with water on the ignition lag with its pulsed high-pressure injection into heated air was studied experimentally. It is shown that with relatively small cyclic feed emulsification prolongs ignition and with large cyclic feed, when ignition lag of water-free fuel increases markedly, it accelerates it. The mechanism of cavitation dispersion of the liquid jet during exit from the spray nozzle, determining the flow of the fuel-air mixture, is examined for explaining certain characteristics of the autoignition process. Emulsification of fuel to a considerable extent intensifies cavitation dispersion and thereby affects the course of mixing and, consequently, ignition.Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 3–10, July–August, 1994.     

Experimental investigation of the autoignition process during fuel injection into a heated air flow

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 1, pp. 9–12, January–February, 1989.     

Ignition and combustion of a fuel of low volatility (hexadecane) in shock-heated air

The ignition and combustion of droplets of straight-chain hexadecane have been studied in shock-heated air, by recording the growth of pressure and the growth of radiation at two wavelengths, 520 and 310 nm. The onset of ignition and the ensuing combustion at the lowest shocked-gas temperatures were found to be controlled by evaporation of the hydrocarbon. At higher temperatures, ignition, which is marked by the appearance of chemiluminescence, is controlled by a chemical reaction, probably the breaking of a carbon-hydrogen bond. As ignition is followed by the establishment of a flame, the temperature coefficient of reaction rates, derived from emission and pressure delays, falls. Immediately preceding the establishment of the flame and during the passage of the flame front, radiation at 520 nm builds up. Radiation at this wavelength is attributed to particles of soot. The peak pressures measured correspond to the complete combustion of the charge of hydrocarbon, and the major exothermic reactions take place in about 0.3 ms.     

一次点火油煤混烧不成功的原因分析

针对XSZC公司一次点火油煤混烧不成功的原因进行了分析，主要原因是燃烧器调节不当、一次风机用风不当及油枪参数设置不合理。针对上述原因进行了改进，改进后点火升温过程中火焰始终稳定。     

Ignition and combustion of pyrotechnic compositions based on micro- and nanoparticles of aluminum diboride in air flow in a two-zone combustion chamber

This paper presents the experimental study of ignition and combustion of micro- and nanoparticles of aluminum diboride as part of pyrotechnic energy-saturated compositions in a gas generator with an air afterburner chamber and the thermodynamic calculations of combustion of pyrotechnic compositions based on aluminum diboride in air. The discharge of the combustion products from the afterburner chamber is recorded on video. It is shown that replacing micron aluminum diboride by powdered diboride with a mass-average diameter of particles equal to ≈270 nm in the pyrotechnic composition and increasing the pressure in the afterburner chamber cause the combustion efficiency in air to increase by 5–20%.     

Optimization of the combustion of blends of domestic fuel oil and cottonseed oil in a non-modified domestic boiler

This study characterizes combustion of blends of DFO (domestic fuel-oil) and refined cottonseed oil produced in Burkina Faso at different percentages in a non-modified DFO burner by determining its overall performance (consumption and thermal capacity) and gas emissions (CO, CO₂, O₂, NO, NO_x, SO₂). The physical and chemical characteristics of the different blends confer on each blend the status of a special fuel requiring specific adjustment of the burner. The influence of combustion parameters such as equivalence ratio and fuel pressure is studied. Results show that emissions of CO, NO_x and CO₂ are similar for all fuel blends at the operating point corresponding to 0.86 equivalence ratio and 20 bars fuel pressure. Whatever the fuel pressure is, SO₂ emission is increasing with DFO percentage in blends.Experimental emission results obtained with suitable adjustments for a blend containing 30% cottonseed oil and 70% DFO are compared to the calculated results obtained using a combustion equation based on a global chemical mechanism. The results show that there is a satisfactory match between the calculation and experimental results.     

Fireball during combustion of hydrocarbon fuel releases. I. Structure and lift dynamics

The formation, combustion, and thermal interaction of the fireballs which develop upon ignition of a cloud of hydrocarbon fuel near the Earth’s surface are simulated numerically. The axisymmetric nonstationary flow is described by a system of Favre averaged conservation equations invoking a (k−ε)-turbulence model, a model for turbulent combustion, and a global-kinetic scheme for formation and burnup of soot particles. The optical properties of the mixture of combustion products and soot are modeled by a weighted sum of gray gases. The radiation field is calculated using a combination of a volume emission approximation and a diffusion approximation. Calculations are done for fireballs formed during vertical releases of gaseous propane masses of 1 g to 10³ kg with ignition near the release point. The internal structure of a fireball is analyzed in detail at various stages of its evolution. The lift dynamics of a fireball is illustrated for release velocities corresponding to Froude numbers (defined as the square of the ratio of the linear outflow velocity to the characteristic velocity owing to buoyancy forces) ranging from 5–250. The temperature, concentrations, and reaction rates in the fireball are determined as functions of time. It is shown that for these ranges of fuel mass and release velocity, the dimensionless parameters introduced here can be used for scaling the results and using the calculated dependences obtained here in a unified fashion. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 7–19, May–June 1999.     

Numerical and experimental study of water/oil emulsified fuel combustion in a diesel engine

Numerical and experimental studies were made on some of the chemical and physical properties of water/oil emulsified fuel (W/OEF) combustion characteristics. Numerical investigations of W/OEF combustion's chemical kinetic aspects have been performed by simulation of water/n-heptane mixture combustion, assuming a model of a homogenous reactor's concentric shells. The injection and fuel spray characteristics are analyzed numerically also in order to study indirectly the physical effects of water present in diesel fuel during the combustion process. The experimental results of W/OEF combustion in the DI diesel engine are also presented and discussed. The results of engine testing in a broad field of engine loads and speeds have shown a significant pollutant emission reduction with no worsening of specific fuel consumption.     

Ignition,combustion, and agglomeration of encapsulated aluminum particles in a composite solid propellant. II. Experimental studies of agglomeration

The combustion characteristics of propellants containing AP, HMX, an energetic binder, and aluminum particles with various polymer coatings are studied at pressures of 0.15 and 4.6 MPa. It is found that the coatings influence the burning rate, the particle size distribution of condensed combustion products, and the completeness of aluminum combustion. It is shown that the agglomeration can be reduced by using aluminum with fluorine-containing coatings. The application of some coatings results in a reduction in the mass of the agglomerates with an insignificant increase in their size. The greatest effect was achieved when using aluminum coated with (CH₂=CH-CH₂-O)₂Si[OCH₂(CF₂-CF₂)₂H]₂ [bis(allyloxy)-bis(2,2,3,3,4,4,5,5-octafluoropentyloxy)silane]. For this coating, a size reduction is also observed for micron-size oxide particles. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 3, pp. 83–97, May–June, 2007.     

Self-ignition and mechanisms of interaction of coal with oxygen at low temperatures. 3. Changes in the composition of coal heated in air at 60 °C

The gradual changes in weight, in elementary composition, in content of oxygen functional groups and in spin concentration have been established for samples of black coal, brown coal and lignite heated in air for a maximum of 1200 h. An intensive oxidative dehydrogenation was found to occur after more than 300 h oxidation. The process was preceded by a decrease in weight and in oxygen content; its start was found to coincide with a sharp increase in the alcoholic content and in coal ability to exchange hydrogen with calcium acetate, and its rate was found to diminish simultaneously with this ability. The acidity ascribed to phenols decreases gradually but it was found to increase at the end of the experiment. A decrease in ignition temperature was established for oxidized black coal, as well as a change in the composition of low-molecular-weight hydrocarbons evolved during the subsequent gradual heating in air. Some of the changes in the composition during coal oxidation may be explained by acid catalysis.     

Influence of fuel and air/fuel equivalence ratio on the emission of hydrocarbons from a SI engine. 2. Formation pathways and modelling of combustion processes

A spark ignition engine was used to study the impact of fuel composition and of the air/fuel equivalence ratio on exhaust emissions of specific hydrocarbons. The fuel blends used contained eight main hydrocarbons and four oxygenated compounds. The identification of each exhaust pollutant fuel precursor is already done. After this identification, several models correlating the exhaust concentration of these pollutants with the fuel composition are presented on each air/fuel equivalence ratio. Based on the above findings, the main formation paths for the formation of each exhaust pollutant are proposed.     

Approximate flame temperature distribution during combustion of oil and a coal-oil mixture

The flame temperature field has been analytically determined and theoretically calculated for the cases where the air supply is uniform along the flame and supplied completely at the flame beginning. The two ways of determining the flame heating ability have been analysed, first formulated as a fraction of the local supply of the chemical energy of fuel, and second as a fraction of the local physical enthalpy of the flame substance passing through the flame cross section. The present analysis confirms practical observations that the more uniform the supply of combustion air, the more equalized is the temperature in the flame. Present calculation procedures can be applied to design or control the flame temperature field by using the proper distribution of combustion air delivered along the flame.     

Castor oil based interpenetrating polymer networks. II. Synthesis and properties of emulsion polymerized products

Polystyrene Latexes were synthesized using sodium ricinoleate (the ehief saponification product of castor oil) as the surfactant. Later sulfur, more sodium ricinoleate, and sometimes castor oil were added, and the emulsion heated to a temperature where the sulfur vulcanized the castor oil products, making a semi-interpenetrating polymer network. Stress-strain studies showed the presence of a well developed yield point and high elongation for some samples, indicating considerable toughening for slow rates of strain. Electron microscopy revealed a complex two-phased morphology. Usually polystyrene was the continuous phase. The rubbery phase domain size depended upon the amount of castor oil products added lzod impact strengths showed only modest improvements; probably because of the high glass transition temperature of the castor oil vulcanizate.     

Effect of distributed injection of air into the afterburning chamber of a ram-rocket engine on the efficiency of combustion of boron particles

A mathematical model of combustion of boron particles in a ram-rocket engine is developed. The boron combustion efficiency for one-stage and two-stage injection of air into the afterburning chamber is calculated. It is demonstrated that two-stage injection of air sometimes allows the time of complete combustion of boron particles to be significantly reduced (by a factor of 1.5–3); thus, the fuel combustion efficiency in the ram-rocket engine can be increased. The simulated results are consistent with available experimental data.     

Investigation of soot nanoparticles during combustion of liquid hydrocarbons with injection of a superheated steam jet into the reaction zone

The characteristics of soot particles formed during combustion of liquid hydrocarbons in a laboratory model of an original burner with injection of a superheated steam jet into the reaction zone are experimentally studied. The concentration and size distribution of soot particles formed in the burner flame are measured by a diffusion aerosol spectrometer. It is shown that the majority of the primary particles have sizes ranging from 20 to 60 nm. The particle concentration in the external flame rapidly decreases with distance from the burner exit from 10⁸ to 5 · 10⁶ cm^?3. The images obtained by transmission electron microscopy demonstrate a chain-branched (fractallike) structure of aggregates. The primary particles composing these aggregates have a union-like structure with the interplane distance between the layers smaller than 1 nm. Compact aggregates with sizes up to 500 nm are observed in cooled combustion products. The content of soot in combustion products is 35 mg/m³, and the mean particle mass is 7 · 10^?12 mg. Results obtained in the combustion modes with injection of a superheated steam jet and with injection of an air jet are compared.     

Self-ignition and mechanisms of interaction of coal with oxygen at low temperatures. 1. Changes in the composition of coal heated at constant rate to 250 °C in air

The changes in weight, in elementary composition, in content of oxygen functional groups and in spin concentration of lignite, brown and black coal samples heated in a stream of humid air at a rate of 1 °C/min to various temperatures have been determined I.r. spectra of oxidized and non-oxidized brown coal are recorded and the yields of CO, CO₂ and H₂O were measured. The mixtures of low-molecular-weight hydrocarbons evolved before self-ignition were analysed by gas chromatography, and the temperatures of self-ignition were determined in an oxygen stream using a Leitz microscope. A region of coal oxidation was identified where the hydrogen content remained invariable or increased, indicating an interaction of coal with water in the presence of oxygen. For the next region the atomic ratio H/C of the overall gaseous product was found to be high (6 to 10). Self-ignition was found to occur in this region. The results permit coal oxidation to be considered as a redox process. The aromatic part of coal is believed to act as an oxidizing agent in the region where hydrogen is less affected by molecular oxygen.