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A.I. Karpov

Bio: A.I. Karpov is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Flame spread & Combustion. The author has an hindex of 9, co-authored 30 publications receiving 185 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a comprehensive experimental study of flame spread over the surface of horizontally placed slabs of four types of PMMA specimens in still air was presented, and the results revealed differences in the combustion character of the specimens investigated.

30 citations

Journal ArticleDOI
01 Jan 2019
TL;DR: In this article, a coupled model of heat and mass transfer involving two-dimensional elliptic conservation equations both for gas phase and solid fuel has been used with the fuel surface approximation of the samples burnout.
Abstract: This study presents the results of a comprehensive experimental investigation and numerical simulation of the downward flame spread over PMMA slabs. For the first time, in the case of downward flame spread over PMMA slab 9.6 mm thick, temperature and species concentration fields in the gas-phase flame, temperature profiles in the condensed phase and dependence of the heat flux to the burning surface on the distance from the flame front were obtained. A coupled model of heat and mass transfer involving two-dimensional elliptic conservation equations both for gas phase and solid fuel has been used with the fuel surface approximation of the samples burnout. This allowed us to state, for the indefinite intermediate mode (in terms of the sample thickness, which are not neither thermally thin nor thermally thick), a mathematical model ensuring good agreement between the experimental and calculated macro parameters of combustion. The results of comparing the experimental and calculated data allowed us to determine a number of facts, which, despite the satisfactory agreement between the simulation and the experimental data in the main macro parameters, indicate the necessity of further improvement of the model derived. Such facts are: the increasing disagreement between the calculation and the experiment in the position of the maxima of the temperature in the gas phase as the distance from the flame front grows; essential difference in the width of the MMA and O2 consumption zone between the calculation and the experiment; identification in the experiment of CO as an intermediate product. Further improvement of the model should be aimed at more detailed development of the combustion reaction mechanism, which should consider at least two steps.

24 citations

Journal ArticleDOI
TL;DR: In this article, a model of erosive burning of stick propellant is developed by considering correlations for turbulent heat transfer affected by combustion reaction in the flame zone and developing an expression for the averaged value of combustion reaction rate.
Abstract: A model of solid propellant erosive burning is developed. Reciprocal interaction of turbulence with chemical reaction is taken into account by considering correlations for turbulent heat transfer affected by combustion reaction in the flame zone and developing an expression for the averaged value of combustion reaction rate. A local-isotropic assumption is invoked to reduce the full transport equations for turbulent fluctuations to simple formulas. Erosive burning of stick propellant is studied numerically by a boundary-layer approach. Satisfactory agreement with measurements is obtained using the proposed model both with the full transport equation and with the local-isotropic assumption. A new physical mechanism of negative erosive burning (decrease of propellant burning rate under blowing of burning surface) is proposed and confirmed by numerical investigations of stick propellant burning by using a mathematical model that is described by two-dimensional Navier-Stokes equations.

22 citations

Journal ArticleDOI
TL;DR: In this paper, a coupled analysis involving gas phase and solid fuel is considered using unsteady two-dimensional conservation equations describing the self-sustained flame propagation, which is focused on the mechanism of flame suppression at the flame leading edge.
Abstract: A CFD model has been developed to predict the behavior of the flame spread over solid fuels in water mist environment. A coupled analysis involving gas phase and solid fuel is considered using unsteady two-dimensional conservation equations describing the selfsustained flame propagation. Due to the analysis is focused on the mechanism of flame suppression at the flame leading edge, which is explicitly exposed to the mist, finite-rate chemical reaction is taken into account. The equations for water mist and vapor mass fractions are added to the basic flame spread statement, which includes corresponding term describing energy consumption due to water evaporation. Horizontal flame spread over thick fuel beds of polymeric material (PMMA) under water mist suppression has been investigated. The results have shown that self-sustained energy balance in the heat release zone in the flame is highly sensitive to the external energy loss, which in this case is due to water droplet evaporation. Thus, flame struggles against the presence of water mist on the flame leading edge and either continues to propagate with almost the same velocity (as of without water mist), or complete extinction occurs. The extinguishing characteristics of fine water mist with the droplet diameter of the order of 30 microns are investigated. A critical concentrations of initial water mist mass fraction required for extinguishment have been achieved for the various conditions of flame spread phenomenon.

19 citations

Journal ArticleDOI
TL;DR: In this paper, a coupled model of heat and mass transfer describing the feedback between gas-phase flame and solid fuel has been defined by non-stationary two-dimensional elliptic equations applied both for gas phase and liquid fuel.

17 citations


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Book
01 Dec 1988
TL;DR: In this paper, the basic processes in Atomization are discussed, and the drop size distributions of sprays are discussed.Preface 1.General Considerations 2.Basic Processes of Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.AtOMizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index
Abstract: Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

1,214 citations

Journal ArticleDOI
TL;DR: In this article, the activation energy, preexponential factor, and pre-exponential energy were obtained of a one-step pyrolysis reaction in supposition of a first-order reaction using simple mathematical fitting and an iso-conversion method.

52 citations

Journal ArticleDOI
TL;DR: In this article, the integral characteristics of evaporation of single water droplets in their motion through high-temperature combustion products have been carried out with a setup incorporating a high-speed measuring PIV system.
Abstract: An experimental study of the integral characteristics of evaporation of single water droplets in their motion through high-temperature combustion products has been carried out with a setup incorporating a high-speed measuring PIV system. The characteristic rates of change in the mass of the water droplets during passage through a flame of fixed height have been determined. Numerical evaluation of the evaporated liquid mass has been performed.

45 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide a detailed discussion of relevant work on the multidimensional computational simulation of heterogeneous solid propellant combustion, focusing on composite solid propellants and plastic-bonded explosives.
Abstract: H ETEROGENEOUS solid energetic materials are widely used in the aerospace and defense industries in rockets, explosives, and diverse pyrotechnic devices. Their basic microstructure consists of oxidizer particles embedded in a polymeric binder. Two important classes of energeticmaterials are solid propellants and plastic bonded explosives. A typical composite solid propellant is composed ammonium perchlorate (AP) particles embedded in a polymer such as hydroxyl-terminated polybutadiene (HTPB) or polybutadiene acrylonitrile. A common variation is the addition of metal particles (e.g., aluminum) to raise the combustion temperature. Plastic bonded explosives consist of a heterogeneous mixture of high-explosive crystals (such as cyclotetramethylenetetranitramine or cyclotrimethylenetrinitramine) and a polymeric binder. Here, the discussion is restricted to composite solid propellants. The intent of the present survey is to provide a highlighted discussion of relevant work on the multidimensional computational simulation of heterogeneous solid propellant combustion. Routine numerical simulations are now being carried out, in which many of the physical characteristics of real propellants are mimicked, including random packing of oxidizer particles in a fuel binder, unsteady three-dimensional heat conduction within the solid, unsteady regressionof thenonplanar propellant surface, andcoupling with an unsteady three-dimensional combustion field sustained by reactantfluxes from the surface. Such computations require the use of massively parallel supercomputers, and even then there are limitations onwhat physics can be included. The ultimate goal is to develop a truly predictive simulation tool that can assist in design and optimization of propellant microstructures and propellant grain designs for internal solid rocket motors. Modeling and simulation of composite propellants will remain a vital task because solid rocket motors are critical to national defense, communications, space exploration, and eventually space tourism. The value of computational combustion is eloquently presented in a recent review paper [1]. II. Modeling

43 citations

Journal ArticleDOI
TL;DR: In this article, a pyrolysis model capable of predicting materials' fire behavior as a function of concentration was developed for an intumescent flame retardant system: poly(lactic acid) (PLA) blended with melamine (MEL) and ammonium polyphosphate (APP).
Abstract: A pyrolysis model capable of predicting materials’ fire behavior as a function of concentration was developed for an intumescent flame retardant system: poly(lactic acid) (PLA) blended with melamine (MEL) and ammonium polyphosphate (APP). The model was developed through inverse analysis of data obtained from bench-scale pyrolysis experiments wherein a 0.07-m-diameter disk-shaped sample was exposed to well-defined radiant heating in an anaerobic environment. Sample back surface temperature, sample shape profile and burning rate were measured simultaneously. A numerical pyrolysis modeling framework, ThermaKin2Ds, and a previously developed semi-global thermal decomposition reaction mechanism were employed in the inverse analysis to determine material properties that define the heat and mass transport inside the pyrolyzing solids. The final pyrolysis model was found to predict materials’ fire behavior for a variety of thermal exposures and material compositions. The model construction process revealed that a reduction in gas transfer coefficients helped to reproduce certain features of the burning rates profiles. Idealized cone calorimetry scenarios were simulated to study the influence of additives on materials’ fire behavior, and the results demonstrated that the blend with 5 wt % MEL and 25 wt% APP was found to be the most effective system with a 69% reduction in the average heat release rate comparing to that of PLA. A similar significant reduction has been reported in the literature, supporting the accuracy of this model. This work demonstrates a methodology that enables intelligent design of intumescent flame retardant materials tailored for specific applications, where low flammability is required.

38 citations