Showing papers in "Combustion, Explosion, and Shock Waves in 2005"

Correlating Aluminum Burning Times

Abstract: Characteristics of aluminum combustion are summarized in an overview of the subject, focusing on the burning time of individual particles. Combustion data from over ten different sources with almost 400 datum points have been cataloged and correlated. Available models have also been used to evaluate combustion trends with key environmental parameters. The fundamental concepts that control aluminum combustion are discussed, starting from a discussion of the D n law. The exponent in the D n law is shown to be lower than two, with nominal values of ≈1.5 to 1.8 being typical. The effect of the ambient medium on the burning time is considered, oxygen as an oxidizer being twice as effective as water and about five times more effective than carbon dioxide. The effect of pressure and initial temperature is minor.

Burning of Nano-Aluminized Composite Rocket Propellants

Abstract: Several aluminum nanopowders were examined and compared with the final goal to evaluate their application in solid rocket propulsion. A detailed investigation of pre-burning properties by the Brunauer-Emmet-Teller method, electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy was carried out. Ballistic properties and the combustion mechanism of several aluminized propellant formulations were investigated. In particular, aggregation and agglomeration of metal particles at and near the burning surface were analyzed by high-speed high-resolution color digital video recordings. All tested nano-powders are of Russian production; their physical characterization was carried out at the Istituto Donegani (Novara, Italy); ballistic studies were performed at the Solid Propulsion Laboratory (Milano, Italy) using laboratory and, for comparison, industrial composite propellants based on ammonium perchlorate as an oxidizer. Results obtained under a fair variety of operating conditions typical of rocket propulsion indicate, for increasing nano-Al mass fraction or decreasing nano-Al size, larger steady burning rates with essentially the same pressure sensitivity. While aggregation and agglomeration phenomena still occur, their significance may be reduced by using nano-Al instead of micro-Al.

Soot Formation in Combustion Processes (Review)

Abstract: A review is given of recent papers on the phenomenology, kinetics, and mechanism of soot formation in hydrocarbon combustion; the effects of various factors on the formation of polycyclic aromatic hydrocarbons, fullerenes, and soot, low-temperature soot formation in cool flames, combustion in electric field, and the paramagnetism of soot particles from an ecological viewpoint are considered.

Hexanitrohexaazaisowurtzitane (CL-20) and CL-20-based formulations (review)

Abstract: This paper reviews the research and development work on CL-20, the most powerful high-energy material of today, as well as CL-20-based formulations. Methods of CL-20 synthesis and processes for obtaining a desired particle size are discussed. Particular attention is paid to optimization of conditions for obtaining the most stable high-density polymorph. The Fourier Transform Infrared spectroscopy and X-ray diffraction appear to be effective means for distinguishing CL-20 polymorphs. The thermal decomposition pattern of CL-20 as well as the proposed decomposition and combustion mechanisms also form part of this manuscript. Investigations performed by various researchers show that its relatively high sensitivity needs special attention from the viewpoint of CL-20 preparation and processing of formulations based on this substance. Salient features of CL-20-based explosives and gun/rocket propellants studied are included into this review. CL-20 may be ranked as the most attractive compound for futuristic explosive and propellant formulations. The research activities performed by the authors on synthesis and characterization of CL-20 are briefly described.

Numerical Simulation of Single Aluminum Particle Combustion (Review)

Abstract: A two-dimensional, unsteady-state, kinetic-diffusion-vaporization-controlled numerical model for aluminum particle combustion is presented. The model solves the conservation equations, while accounting for species generation and destruction with a 15-reaction kinetic mechanism. Two of the major phenomena that differentiate aluminum combustion from hydrocarbon-droplet combustion, namely, condensation of the aluminum-oxide product and subsequent deposition of part of the condensed oxide onto the particle, are accounted for in detail with a submodel for each phenomenon. The effect of the oxide cap in the distortion of the species and temperature profiles around the particle is included into the model. The results obtained from the model, which include two-dimensional species and temperature profiles, are analyzed and compared with experimental data. The combustion process is found to approach a diffusion-controlled process for the oxidizers (O2, CO2, and H2O) and conditions treated. The flame-zone location and thickness are found to vary with the oxidizer. The result shows that the exponent of the particle-diameter dependence of the burning time is not a constant and changes from ≈1.2 for smaller-diameter particles to ≈1.9 for larger-diameter particles. Owing to deposition of the aluminum oxide onto the particle surface, the particle velocity oscillates. The effect of pressure is analyzed for a few oxidizers.

Thermal Decomposition and Combustion of Ammonium Dinitramide (Review)

Abstract: A comprehensive review of thermal decomposition and combustion of ammonium dinitramide (ADN) has been conducted. The basic thermal properties, chemical pathways, and reaction products in both the condensed and gas phases are analyzed over a broad range of ambient conditions. Detailed combustion-wave structures and burning-rate characteristics are discussed. Prominent features of ADN combustion are identified and compared with other types of energetic materials. In particular, the influence of various condensed- and gas-phase processes in dictating the pressure and temperature sensitivities of the burning rate is examined. In the condensed phase, decomposition proceeds through the mechanisms ADN → NH4NO3 + N2O and ADN → NH3 + HNO3 + N2O, the former mechanism being the basic one. In the gas phase, the mechanisms ADN → NH3 + HDN and ADN → NH3 + HNO3 + N2O are prevalent. The gas-phase combustion-wave structure in the range of 5–20 atm consists of a near-surface primary flame followed by a dark-zone temperature plateau at 600–1000°C and a secondary flame followed by another dark-zone temperature plateau at 1000–1400°C. At higher pressures (60 atm and above), a final flame is observed at about 1800°C without the existence of any dark-zone temperature plateau. ADN combustion is stable in the range of 5–20 atm and the pressure sensitivity of the burning rate has the form r b = 20.72p 0.604 [mm/sec] (p = 0.5–2.0 MPa). The burning characteristics are controlled by exothermic decomposition in the condensed phase. Above 100 atm, the burning rate is well correlated with pressure as r b = 8.50p 0.608 [mm/sec] (p = 10–36 MPa). Combustion is stable, and intensive heat feedback from the gas phase dictates the burning rate. The pressure dependence of the burning rate, however, becomes irregular in the range of 20–100 atm. This phenomenon may be attributed to the competing influence of the condensed-phase and gas-phase exothermic reactions in determining the propellant surface conditions and the associated burning rate.

Numerical Simulation of Formation of Cellular Heterogeneous Detonation of Aluminum Particles in Oxygen

Abstract: Formation of cellular detonation in a stoichiometric mixture of aluminum particles in oxygen is studied by means of numerical simulation of shock-wave initiation of detonation in a flat and rather wide channel. By varying the channel width, the characteristic size of the cells of regular uniform structures for particle fractions of 1–10 µm is determined. The calculated cell size is in agreement with the estimates obtained by methods of an acoustic analysis. A relation is established between the cell size and the length of the characteristic zones of the detonation-wave structure (ignition delay, combustion, velocity and thermal relaxation).

Continuous Spin Detonation in Annular Combustors

Abstract: An acetylene-oxygen mixture is burned in two annular chambers 100 mm in diameter in the spin detonation regime with supercritical and subcritical differences of oxygen pressure in the annular slot. By varying the flow rates of components of the mixture, width of the slot for oxidizer injection, point of fuel injection, and initial ambient pressure, the regions of existence and the structure of transverse detonation waves are studied, and the limits of existence of continuous detonation in terms of pressure in the chamber are determined. The losses of the total pressure in the flow in oxygen-injection slots and in fuel-injector orifices are estimated.

Novel Ultrahigh-Energy Materials

Abstract: This paper reviews the recent work carried out in the field of modern high-energy materials (HEMs) with the emphasis on homoleptic polynitrogen compounds A large volume of quantum-chemical investigations have predicted the possibility of existence of polynitrogen compounds not only as short-lived transient species but also in the form of isolable discrete molecules Despite the theoretical speculations, only a few polynitrogen ions are known today in addition to well-entrenched N 1− 3 discovered almost 100 year ago Extraordinary potential of these green molecules to deliver high amounts of energy in comparison with today’s and tomorrow’s most powerful HEMs, namely, hexanitrohexaazaisowurtzitane (CL-20) and octanitrocubane (ONC), has fuelled the imagination of propellant and explosive engineers and technologists Research activities are in progress in many quantum-chemical schools to explore the possibility of other promising polynitrogen compounds After the recent discovery of key synthons/building blocks Mg(N5)2, N 1+ 5 SbF 1− 6 , N 1+ 5 SbF11, N 1+ 5 , N 1+ 5 SnF6, and N 1+ 5 Sn(CF3)4, the wealth of polynitrogen compounds is just waiting to be harvested by the HEMs community There are ambitious plans all over the globe to realize N60, which only prove a eco-friendly dense powerhouse of energy

On the Hydrodynamic Thickness of Cellular Detonations

Abstract: The characterization of the detonation dynamic parameters (detonability limits, direct initiation energy, critical tube diameter, etc.) requires a characteristic length scale for the detonation wave in the direction of propagation. However, most detonations are unstable, their reaction zones are turbulent, and their structure departs significantly from the idealized one-dimensional Zel'dovich-Von Neumann-Doring model. It is argued that the most suitable length scale to characterize a turbulent detonation wave is the location of the sonic surface, which separates the statistically stationary flow of the reaction zone structure from the unsteady expansions behind the wave. Previous real and numerical experiments are reviewed in order to determine the relation between the global location of the mean sonic surface and the chemical, mechanical, and thermodynamic relaxation processes occurring in the detonation wave structure. Based on the experimental evidence, we postulate that the structure of turbulent detonations can be modeled in the one-dimensional Zel'dovich-Neumann-Doring framework, with the turbulence effects as source terms in the momentum and energy equations. These source terms involve the relaxation rates for the mechanical fluctuations, thermal fluctuations and the chemical exothermicity towards equilibrium. In the framework of the idealized one-dimensional structure with source terms, the sonic surface location is governed by the balance between the competing source terms satisfying the generalized Chapman-Jouguet criterion. We recommend that future work in detonation research should be focused at: 1) acquiring a large experimental database for the mean detonation properties (detonation velocity, location of sonic surface and mean reaction zone profiles); 2) the development of the appropriate source terms involving the turbulent fluctuations in the averaged equations of motion.

Shock Initiation of Energetic Materials at Different Initial Temperatures (Review)

Abstract: Shock initiation is one of the most important properties of energetic materials, which must transition to detonation exactly as intended when intentionally shocked and not detonate when accidentally shocked. The development of Manganin pressure gauges that are placed inside the explosive charge and record the buildup of pressure upon shock impact has greatly increased the knowledge of these reactive flows. This experimental data, together with similar data from electromagnetic particle velocity gauges, has allowed us to formulate the Ignition and Growth model of shock initiation and detonation in hydrodynamic computer codes for predictions of shock initiation scenarios that cannot be tested experimentally. An important problem in shock initiation of solid explosives is the change in sensitivity that occurs upon heating (or cooling). Experimental Manganin pressure gauge records and the corresponding Ignition and Growth model calculations are presented for two solid explosives, LX-17 [92.5% triaminotrinitrobenzene (TATB) with 7.5% Kel-F binder] and LX-04 [85% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazine (HMX) with 15% Viton binder] at several initial temperatures.

Specific Features of Synthesis of Detonation Nanodiamonds

Abstract: It is demonstrated that the Chapman-Jouguet parameters for high explosives used in nanodiamond synthesis are located in the region of liquid nanocarbon; therefore, the chemical reaction zone of the detonation wave involves formation of carbon nanodroplets, which are later crystallized into nanodiamonds on the segment of the isentrope of expansion of detonation products, passing through the region of stability of nanodiamonds in the pressure range of 16.5–10 GPa and the temperature range of 3400–2900 K. Soot in the resultant mixture is the product of amorphization of nanodroplets rather than graphitization of ultrafine diamonds. The influence of detonation conditions of high-explosive charges in an explosive chamber on nanodiamond synthesis is analyzed.

Burning of a Cotton Fabric Impregnated by Synthetic Zinc Carbonate Hydroxide as a Flame Retardant

Abstract: Zinc carbonate hydroxide [ZnCO3·Zn(OH)2] synthesized by means of the multiple-bath method was deposited onto a cotton fabric, and its uniformity was ensured by means of squeeze rolls. Prolonged burning was observed on treated specimens: 200.5 sec for 20.20% of ZnCO3·Zn(OH)2 added to 100 g of a dry fabric increased to 337.5 sec for a 45.39% addition. The ashes of the treated specimens were subjected to X-ray diffraction analysis, and the result was compared with data for zinc and zinc-oxide powders. The existence of zinc oxide was detected in the ashes, but no traces of the metallic zinc were discovered. Therefore, it can plausibly be assumed that a reduction-oxidation reaction occurs during the smoldering process.

High-Temperature Combustion Synthesis: Generation of Electromagnetic Radiation and the Effect of External Electromagnetic Fields (Review)

Abstract: A critical review of recent papers on mechanisms of generation of internal electromagnetic fields and the action of external electromagnetic fields on self-propagating high-temperature synthesis of heterogeneous systems is presented. Generation of an internal electromagnetic field is caused by different rates of diffusion of charged defects through the layer of the growing product in strongly nonequilibrium reactions. Possible emergence of residual magnetic fields is related to orientation of magnetic domains in the arising internal thermal and electromagnetic fields of the synthesis wave. The external electromagnetic action is characterized by thermal, magneto- and electrodynamic, and kinetic factors. The thermal factor is caused by the Joule effect, whereas the electro- and magnetodynamic influence is caused by electromigration, magnetic compression and changes in electrical conductivity of the condensed phase, and ion wind in the gas in pores. The kinetic factor is caused by generation of superequilibrium charge carriers in condensed particles (defects) and by emission of high-energy electrons into the gas surrounding the particles.

Combustion models for energetic materials with completely gaseous reaction products

Abstract: From a brief review of published combustion models for energetic materials, it follows that considerable modeling efforts have been directed toward a more accurate description of gas-phase processes. It is often assumed that gas-phase reactions play a dominant role in burning rate control. At the same time, more and more arguments have emerged suggesting a dominant role of condensed-phase processes for a number of the most widely used homogeneous propellants in the rocket range of pressures. However, serious problems remain in the modeling of such combustion regimes. A solution of these problems is proposed.

Computation of Dust Lifting behind a Shock Wave Sliding along the Layer. Verification of the Model

Abstract: The problem of dust lifting behind a shock wave is solved within the framework of the equilibrium model of mechanics of heterogeneous media. Verification of the model proposed is performed. It is shown that different flow patterns are formed in layers with different shapes of the edge and constant- or variable-amplitude shock waves. Allowance for turbulence of the mixture leads to origination of a high-velocity near-wall trickle at the edge of the layer, and the particles are lifted to a greater height.

Detonation Velocity of Emulsion Explosives Containing Cenospheres

Abstract: The detonation velocity of an emulsion explosive containing hollow alumosilicate microspheres (cenospheres) as the sensitizer is measured. The size of the microspheres is 50–250 µm. The relations between the detonation velocity and the charge density and diameter are compared for emulsion explosives containing cenospheres or glass microballoons as the sensitizer. It is shown that for a 55 mm diameter charge, the maximum detonation velocity of the composition with cenospheres of size 70–100 µm is 5.5–5.6 km/sec, as well as for 3M glass microballoons. The critical diameter for the emulsion explosive with cenosphere is 1.5–2 times larger than that for the emulsion explosive with glass microballoons and is 35–40 mm.

Phase Diagram of Nanocarbon

Abstract: In the phase diagram of carbon, the positions of the melting and thermodynamic-equilibrium curves of detonation nanodiamonds or ultrafine diamonds are found as functions of diamond particle size. The position of the set of triple points located in the ranges of pressure 13.5–16.5 GPa and temperature 2210–4470 K and determining the region of the liquid state of nanocarbon is determined. In the phase diagram of nanocarbon, the diamond region is divided into three parts according to the type of nanoparticles: nanodiamond, liquid nanocarbon (nanodrops), and amorphous nanocarbon.

Some Stability Aspects of Gas Combustion in Porous Media

Abstract: Some aspects of the stability of hot-spot and oblique gas-combustion fronts in porous media are considered using a thermal model. A general expression for the velocity of a curved wave front of filtration gas combustion is obtained taking into account the curvature and local slope of the front. It is shown that curvature always promotes stabilization of the front. The slope of the front, in principle, can have a destabilizing effect. However, because this effect is weaker than the curvature effect, it does not cause development of instability. The roles of convective heat and mass transfer between the hot spot and the ambient gas flow and selective diffusion in the development of local instability are analyzed. Criteria are found for the development of hot-spot instability, and the ranges of system parameters in which instability is possible are determined. The effect of variation in the length of the front during wave propagation on the development of instability of an oblique front is considered. Accounting for this factor gives a criterion for instability development that coincides with the experimental one.

Drag of Nonspherical Particles in a Flow behind a Shock Wave

Abstract: The early stage of velocity relaxation of nonspherical particles in a flow behind an incident shock wave is considered by the method of multiframe shadowgraphy. A procedure of processing the data on the motion of a free body for determining its acceleration is proposed; in combination with the diagnostic method used, the procedure forms something like a noncontact aerodynamic balance. Novel data on the drag of bodies of irregular shape in a flow behind a shock wave with Mach numbers of 0.5–1.5 and Reynolds numbers of ≈105 typical of dust explosions are obtained. It is found that the values of drag of a nonspherical bluff body and a sphere under these conditions are similar and exceed the drag of a sphere in a steady flow by a factor of 2 to 3.

Statistical Simulation of Aluminum Agglomeration during Combustion of Heterogeneous Condensed Mixtures

Abstract: A statistical model of aluminum agglomeration during combustion of solid composite rocket propellants is considered; the model describes the process dynamics, beginning from propellant heating in the combustion wave and ending by separation of agglomerates from the burning surface. An algorithm of computing the agglomeration process by the Monte Carlo method is proposed. A series of computations of aluminum agglomeration is performed; the density distribution functions for agglomerate sizes are derived; the dependence of the mean-mass size of agglomerates on the mean-mass size of ammonium-perchlorate particles is determined. The model proposed predicts power dependences of the mean-mass size of agglomerates on pressure and burning rate, which agrees with available experimental data.

Flame stability in a system with counterflow heat exchange

Abstract: Propagation of two flame fronts in a mixture of gases in adjacent channels with oppositely moving gas flows is described within the framework of a one-dimensional model. Stationary solutions of the problem are constructed, and their stability to small perturbations is examined. The ranges of problem parameters (level of heat losses, composition of the mixture, gas-flow velocity, etc.) that allow flame stabilization are found. Conditions for flame oscillations are identified. It is shown that extremely lean mixtures of gases can burn in such a system, even if the channel diameters are smaller than the critical value corresponding to the initial temperature.

Hot-spot combustion of heterogeneous condensed mixtures. Thermal percolation

Abstract: A model of combustion of heterogeneous condensed mixtures composed of reactive particles separated by an inert heat-conducting substance is considered. Propagation of the reaction in a one-dimensional periodic system of point reaction cells connected by inert thermal bridges is examined. The burning rate is determined as a function of the basic parameters of the system, and stability of the steady combustion mode is studied. It is shown that there exists a range of parameters in which the reaction propagates in an unstable manner. Combustion of the system in the instability domain is examined. It is shown that the reaction propagation loses its stability many times as the adiabatic temperature of the system decreases; in this case, the existing unsteady mode is replaced by another, more complicated mode, and the alteration of the regimes in the examined systems always proceeds as a period-doubling bifurcation. Beginning from a certain value of adiabatic temperature, the reaction-propagation process becomes stochastic. In the systems examined, there exists an ultimate adiabatic temperature, below which self-sustained propagation of the reaction in the system becomes impossible.

Selective Diffusion during Flame Propagation and Quenching in a Porous Medium

Abstract: The propagation of propane-air flames in an inert high-porosity medium with nitrogen dilution and oxygen enrichment of the mixture was studied experimentally. It is shown that variation in the nitrogen or oxygen concentration (in the gas phase) leads to a more significant variation in the flame propagation velocity than in the laminar burning velocity; with the addition of nitrogen, the rate of increase in the flame velocity with the initial pressure becomes lower and the concentration range of flame propagation becomes narrower. At the flame propagation limit, the Peclet number obtained from the laminar burning velocity of the initial mixture is not constant but depends on the fuel-to-oxidizer ratio and the nitrogen content in the mixture. The results are interpreted from a physical point of view based on the hypothesis of selective diffusion. It is shown that accounting for the effects of the Lewis numbers of the fuel and oxidizer allows flame propagation in inert porous media to be described quantitatively over wide parameter ranges using a unified relation. At the flame propagation limit, the Peclet number constructed from the laminar burning velocity taking into account these effects is a constant.

Activation of Chain Processes in Combustible Mixtures by Laser Excitation of Molecular Vibrations of Reactants

Abstract: The combustion kinetics of H2-air mixtures containing small amounts (<1%) of ozone is analyzed for the case of excitation of asymmetric vibrations of O3 molecules by CO2 laser radiation with a wavelength of ≈ 9.7 µm. It is shown that the irradiation leads to acceleration of the collisional dissociation of O3 molecules, activation of the chain ignition mechanism, and a decrease in the induction period and ignition temperature. The excitation of asymmetric vibrations of O3 molecules by the CO2 laser radiation is 10–103 times more effective than the currently used method of combustion initiation based on local heating of a medium by IR radiation.

Criterion for Selecting Composite Materials for Explosion Containment Structures (Review)

Abstract: Experimental data on the dynamic response and strength of simple shells of fiber composites are used to justify the choice of these materials for the load-bearing shells of blast-proof structures. It is shown that in such structures composites are preferred to homogeneous metal alloys (structural steels) to eliminate strong scale effects of an energetic nature. A criterion for selecting fibers is proposed and justified experimentally, and reinforcement patterns are determined to obtain optimal (in the strength-mass ratio) compositions for the load-bearing shells of blast-proof containers and chambers.

Magnetic-field amplification in metal shaped-charge jets during their inertial elongation

Abstract: This paper considers magnetic-field amplification in inertially elongating metal shaped-charge jets formed by explosion of a shaped charge with an axial field previously produced in the charge liner. The amplification is related to the effect of magnetic-field freezing in a conducting material and is due to the deformation of the jet material with particle elongation along the magnetic lines. The model of a uniformly elongating, conducting, incompressible, cylindrical rod was used to determine the nature of the field variation in the jet elements versus the magnetic Reynolds number determined by the electrical resistance of the material, the initial axial-strain rate, and the element radius. In high-gradient copper shaped-charge jets, the magnetic field can be amplified by more than a factor of five during elongation. It is shown that the joint action of the force and thermal factors accompanying field amplification in the jet material can lead to jet breakup with radial scattering of the material particles.

Combustion of Energetic Materials in an Acoustic Field (Review)

Abstract: The review summarizes the long-term experience in theoretical research of combustion of gasifying condensed systems with periodically varied pressure. Most results are obtained within the framework of the Zel'dovich-Novozhilov theory. The main properties of the linear function of the burning rate response to harmonically varied pressure are discussed. The concept of nonlinear response functions is introduced, which is illustrated by the explicit form of a number of second-order response functions. A new phenomenon is described: bifurcations of response functions with a varied amplitude or frequency of pressure oscillations. For the simplest gunpowder model containing three parameters only, the sequence of bifurcations of doubling of the burning rate oscillation period is studied, which finally leads to a random combustion regime. An analytical relation between the linear response functions to harmonically varied pressure and to an oscillating radiant heat flux is noted. An example of calculating the response function with allowance for thermal inertia of the gas phase is presented.

Mathematical simulation of heterogeneous detonation of coal dust in oxygen with allowance for the ignition stage

Abstract: A consistent physicomathematical model that describes ignition and detonation combustion of a gas suspension of coal-dust particles is developed. The model is based on the concepts of the two-velocity two-temperature continuum of mechanics of heterogeneous media with allowance for reduced reactions of pyrolysis, combustion of volatiles, and combustion of the coke residue. The model is verified with the use of available experimental data on the dependence of the detonation velocity on the initial concentration of the discrete phase and the dependence of the ignition delay on the Mach number of the incident shock wave. An analysis of ignition of the gas suspension of bituminous coal in shock waves shows that the stage of ignition proceeds under conditions of both temperature and velocity nonequilibrium. The influence of particle heating due to stagnation temperature on devolatilization dynamics and ignition delay is established. Examples of computed flow structures behind shock and detonation waves with allowance for the ignition stage are presented.

Combustion of sprayed liquid fuel in a swirling flow

Abstract: A physicomathematical model and results of numerical studies of aerodynamics and combustion of liquid fuel in a coaxial swirling flow of a gaseous oxidizer are presented. The characteristics of liquid-fuel spraying by a centrifugal injector were determined on the basis of experimental data obtained under isothermal conditions. The influence of flow swirling on the burner characteristics is analyzed.