Sergei Sazhin - Academia.edu (original) (raw)

Papers by Sergei Sazhin

International Journal of Heat and Mass Transfer, 2018

A new model for heating and evaporation of a multi-component liquid film, based on the analytical... more A new model for heating and evaporation of a multi-component liquid film, based on the analytical solutions to the heat transfer and species diffusion equations inside the film, is suggested. The Dirichlet boundary condition is used at the wall and the Robin boundary condition is used at the film surface for the heat transfer equation. For the species diffusion equations, the Neumann boundary conditions are used at the wall, and Robin boundary conditions are used at the film surface. The convective heat transfer coefficient is assumed to be constant and the convective mass transfer coefficient is inferred from the Chilton-Colburn analogy. The model is validated using the previously published experimental data for heating and evaporation of a film composed of mixtures of isooctane/3-methylpentane (3MP). Also, it is applied to the analysis of heating and evaporation of a film composed of a 50%/50% mixture of heptane and hexadecane in Diesel engine-like conditions.

Fuel, 2016

The US Department of Energy has formulated various sets of gasoline fuels, called fuels for advan... more The US Department of Energy has formulated various sets of gasoline fuels, called fuels for advanced combustion engines (FACE), which are consistent in composition and properties. The analysis of heating and evaporation of FACE A gasoline fuel (paraffin-rich) is studied by replacing the 66 components with 19 components to represent this fuel. The reduction in the number of components is based on merging components from the same chemical groups and having the same chemical formula, which have very close thermophysical properties; the components with the highest initial compositions are chosen to be the representative components. Modelling of heating and evaporation of FACE A gasoline fuel and various surrogates is carried out based on the effective thermal conductivity/effective diffusivity model (ETC/ED). The model takes into account the effect of finite liquid thermal conductivity, finite liquid mass diffusivity and recirculation inside the droplets due to their non-zero velocities relative to the ambient air. Four surrogates of FACE A found in the literature are used in the analysis. These surrogates include the five component surrogate chosen for its ability to match the ignition delay time of the FACE A gasoline fuel (Surr1), the primary reference fuel surrogate (PRF84) that matches the research octane number (RON) of FACE A, the one that matches *Manuscript Click here to view linked References hydrogen-to-carbon ratio (H/C), RON, density and distillation curve with FACE A (Surr2), and the one that matches the RON based on mole fraction linear blending (Surr3). It is shown that these surrogates cannot predict adequately the time evolution of surface temperatures and radii of FACE A droplets. New "physical" surrogates with 8, 7 and 6 components (Surr4, Surr5, and Surr6) are introduced to match the evaporation characteristics of FACE A. It is found that Surr5 (7 components surrogate) can predict droplet lifetime and time evolution of surface temperature of a FACE A droplet with errors of up to 5% and 0.25%, respectively. Also, the results show that the H/C, molecular weight and RON of the new surrogates are reasonably close to those of FACE A. These results allow us to recommend that FACE A gasoline fuel can be replaced by the 7 component surrogate that matches H/C, molecular weight, and the RON of FACE A, and adequately predicts the lifetime and surface temperatures of this particular fuel droplet.

International Communications in Heat and Mass Transfer, 2014

This document is the author's pre-print version, not incorporating any revisions agreed during th... more This document is the author's pre-print version, not incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

International Journal of Heat and Mass Transfer, 2014

This document is the author's post-print version, incorporating any revisions agreed during the p... more This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

This paper presents the application of the Discrete Component Model for heating and evaporation t... more This paper presents the application of the Discrete Component Model for heating and evaporation to multi-component biodiesel fuel droplets in direct injection internal combustion engines. This model takes into account the effects of temperature gradient, recirculation and species diffusion inside droplets. A distinctive feature of the model used in the analysis is that it is based on the analytical solutions to the temperature and species diffusion equations inside the droplets. Nineteen types of biodiesel fuels are considered. It is shown that a simplistic model, based on the approximation of biodiesel fuel by a single component or ignoring the diffusion of components of biodiesel fuel, leads to noticeable errors in predicted droplet evaporation time and time evolution of droplet surface temperature and radius.

Procedia IUTAM, 2013

Recently developed models, describing the disintegration of liquid jets and the dynamics of vorte... more Recently developed models, describing the disintegration of liquid jets and the dynamics of vortex ring-like structures at Diesel and gasoline engine-like conditions, are reviewed. The results of comparative analysis of modal and non-modal hydrodynamic instabilities of round viscous fluid jets are presented. Analytical formulae for vortex ring translational velocities, predicted by vortex ring models, are compared with the results of numerical solutions to the underlying equations and experimental data. A new approach to numerical simulation of two-phase two-dimensional flows, based on a combination of the full Lagrangian method for the dispersed phase and the vortex blob method for the carrier phase, is discussed.

Proceeding of the 6th International Symposium on Radiative Transfer, 2012

International Journal of Heat and Mass Transfer, 2010

A simplified model for bi-component droplet heating and evaporation is developed and applied for ... more A simplified model for bi-component droplet heating and evaporation is developed and applied for the analysis of the observed average droplet temperatures in a monodisperse spray. The model takes into account all key processes, which take place during this heating and evaporation, including the distribution of temperature and diffusion of liquid species inside the droplet and the effects of the non-unity activity coefficient (ideal and non-ideal models). The effects of recirculation in the moving droplets on heat and mass diffusion within them are taken into account using the effective thermal conductivity and the effective diffusivity models. The previously obtained analytical solution of the transient heat conduction equation inside droplets is incorporated in the numerical code alongside the original analytical solution of the species diffusion equation inside droplets. The predicted time evolution of the average temperatures is shown to be reasonably close to the measured one, especially in the case of pure acetone and acetone-rich mixture droplets. It is shown that the temperatures predicted by the simplified model and the earlier reported vortex model are reasonably close. Also, the temperatures predicted by the ideal and non-ideal models differ by not more than several degrees. This can justify the application of the simplified model with the activity coefficient equal to 1 for the interpretation of the time evolution of temperatures measured with errors more than several degrees.

International Journal of Engineering Systems Modelling and Simulation, 2010

Simple approximate formulae describing temporal evolution of diesel fuel droplet radii and temper... more Simple approximate formulae describing temporal evolution of diesel fuel droplet radii and temperatures predicted by the kinetic model are suggested. These formulae are valid in the range of gas temperatures relevant to diesel engine-like conditions and fixed values of initial droplet radii, or in the range of initial droplet radii relevant to diesel engine-like conditions and fixed values of gas temperature. During the time period before the hydrodynamic model predicts complete droplet evaporation, these approximations are based on the calculation of the correction to the prediction of the hydrodynamic model. At longer times, the approximations at the earlier times are extrapolated up until the total evaporation of the droplet, using quadratic fittings. The new approximations are shown to be reasonably accurate for predicting the temporal evolution of droplet radii and droplet evaporation times. The predictions of droplet temperature turned out to be less accurate than those of droplet radii, but this accuracy is believed to be sufficient for many practical applications.

International Journal of Engine Research, 2009

A phenomenological study of vortex ring-like structures in gasoline fuel sprays is presented for ... more A phenomenological study of vortex ring-like structures in gasoline fuel sprays is presented for two types of production fuel injectors: a low-pressure, port fuel injector (PFI) and a high-pressure atomizer that injects fuel directly into an engine combustion chamber (G-DI). High-speed photography and phase Doppler anemometry (PDA) were used to study the fuel sprays. In general, each spray was seen to comprise three distinct periods: an initial, unsteady phase; a quasi-steady injection phase; and an exponential trailing phase. For both injectors, vortex ring-like structures could be clearly traced in the tail of the sprays. The location of the region of maximal vorticity of the droplet and gas mixture was used to calculate the temporal evolution of the radial and axial components of the translational velocity of the vortex ring-like structures. The radial components of this velocity remained close to zero in both cases. The experimental results were used to evaluate the robustness o...

Fuel, 2014

Biodiesel fuel droplet heating and evaporation is investigated using the previously developed mod... more Biodiesel fuel droplet heating and evaporation is investigated using the previously developed models, taking into account temperature gradient, recirculation, and species diffusion within droplets. The analysis is focused on four types of biodiesel fuels: Palm Methyl Ester, Hemp Methyl Esters, Rapeseed oil Methyl Ester, and Soybean oil Methyl Ester. These fuels contain up to 15 various methyl esters and possibly small amounts of unspecified additives, which are treated as methyl esters with some average characteristics. Calculations are performed using two approaches: 1) taking into account the contribution of all components of biodiesel fuels (up to 16); and 2) assuming that these fuels can be treated as a one component fuel with averaged transport and thermodynamic coefficients. It is pointed out that for all types of biodiesel fuel the predictions of the multi-component and single component models are rather close (the droplet evaporation times predicted by these models differ by less than about 5.5%). This difference is much smaller than observed in the case of Diesel and gasoline fuel droplets, and is related to the

European Journal of Mechanics - B/Fluids, 2010

Analytical formulae, predicted by recently developed vortex ring models, in the limit of small Re... more Analytical formulae, predicted by recently developed vortex ring models, in the limit of small Reynolds numbers (Re), are compared with numerical solutions of the underlying equation for vorticity and experimental data. Particular attention is focused on the recently developed generalised vortex ring model in which the time evolution of the thickness of the vortex ring core L is approximated as at b , where a and b are constants (1/4 ≤ b ≤ 1/2). This model incorporates both the laminar model for b = 1/2 and the fully turbulent model for b = 1/4. A new solution for the normalised vorticity distribution is found in the form ω 0 + Re ω 1 , where ω 0 is the value of normalised vorticity predicted by the classical Phillips solution. This solution shows the correct trends in the redistribution of vorticity due to the Reynolds number effect, and it predicts the increase in the volume of fluid carried inside the vortex ring. It is emphasised that although the structures of vortex rings predicted by analytical formulae, based on the linear approximation, and numerical calculations for arbitrary Re are visibly different for realistic Reynolds numbers, the values of integral characteristics, such as vortex ring translational velocity and energy, predicted by both approaches, turn out to be remarkably close. The values of velocities in the region of maximal vorticity, predicted by the generalised vortex ring model, are compared with the results of experimental studies of vortex ring-like structures in gasoline engine-like conditions with a high-pressure (100 bar) injector. The data analysis is focused on the direct measurements of droplet axial velocities in the regions of maximal vorticity. Most of the values of these velocities lie between the theoretically predicted values corresponding to the later stage of vortex ring development between b = 1/4 (fully developed turbulence) and 1/2 (laminar case).

Atomization and Sprays, 2010

The results of modeling fluid dynamics, heat/mass transfer, and combustion processes in diesel en... more The results of modeling fluid dynamics, heat/mass transfer, and combustion processes in diesel engine-like conditions are presented with a view to establishing the effects of droplet heating and evaporation models on the prediction of spray penetration, in-cylinder gas pressure, and the amount of fuel vapor, O2, CO2, CO, and NO. The following models have been studied: the infinite thermal conductivity (ITC) and effective thermal conductivity (ETC) liquid phase models, the basic gas phase model, and the gas phase model suggested by Abramzon and Sirignano (1989). A modified version of the TAB (Taylor analogy breakup) model was used for modeling the droplet breakup process. It is pointed out that the ETC model leads to the prediction of shorter spray penetration, in agreement with experimental data, when compared with the ITC model. The effect of the liquid phase model on predicted gas pressure in diesel engines is shown to be relatively weak. The predicted amounts of fuel vapor, O2, CO2, CO, and NO are strongly affected by the choice of the liquid phase model but practically unaffected by the choice of the gas phase model.

Journal of Heat Transfer, 2007

The values of absorption coefficients of gasoline fuel (BP Pump Grade 95 RON ULG (research octane... more The values of absorption coefficients of gasoline fuel (BP Pump Grade 95 RON ULG (research octane number unleaded gasoline)), 2,2,4-trimethylpentane ͑CH 3 ͒ 2 CHCH 2 C͑CH 3 ͒ 3 (iso-octane) and 3-pentanone CH 3 CH 2 COCH 2 CH 3 have been measured experimentally in the range of wavelengths between 0.2 m and 4 m. The values of the indices of absorption, calculated based on these coefficients, have been compared with those previously obtained for low sulphur ESSO AF1313 diesel fuel. These values are generally lower for pure substances (e.g., iso-octane and 3-pentanone) than for diesel and gasoline fuels. The values of the average absorption efficiency factor for all fuels are approximated by a power function aR d b , where R d is the droplet radius. a and b in turn are approximated by piecewise quadratic functions of the radiation temperature, with the coefficients calculated separately in the ranges of droplet radii 2-5 m, 5-50 m, 50-100 m, and 100-200 m for all fuels. This new approximation is shown to be more accurate compared with the case when a and b are approximated by quadratic functions or fourth power polynomials of the radiation temperature, with the coefficients calculated in the whole range 2-200 m. This difference in the approximations of a and b, however, is shown to have little effect on modeling of fuel droplet heating and evaporation in conditions typical for internal combustion engines, especially in the case of diesel fuel and 3-pentanone.

Asian Journal of Scientific Research, 2013

· SAE International Journal of Fuels and Lubricants, 2010

ABSTRACT The results of recent developments of analytical vortex ring models and the applications... more ABSTRACT The results of recent developments of analytical vortex ring models and the applications of these models to interpretation of the experimentally observed dynamics of vortex ring–like structures in gasoline sprays, under non-evaporating conditions, are summarised. Analytical formulae in the limit of small Reynolds numbers (Re), are compared with numerical solutions. Particular attention is focused on the generalised vortex ring model in which the time evolution of the thickness of the vortex ring core L is approximated as , where a and b are constants (1 ≤ b ≤ 1/2). This model incorporates both the laminar model for b=1/2 and fully turbulent model for b=1/4. The values of velocities in the region of maximal vorticity, predicted by the generalised vortex ring model, are compared with the results of experimental studies of fuel droplets distributed in vortex ring-like structures in two gasoline injectors, under cold-start, engine-like conditions. Liquid iso-octane at a temperature of 22 °C was injected at a frequency of 1 Hz and a pressure of 100 bar (direct injection) and 3.5 bar (port injection) into air at atmospheric pressure and a temperature of 20 °C. Phase Doppler Anemometry was performed over a fine measurement grid that covered the whole spray. The decaying phase of fuel injection showed the most clearly defined vortex rings. The identification of their locations in each time step permitted the determination of the velocities of their displacement in the axial and radial directions. Although the radial component of velocity in both these regions is equal to zero, the location of both changes with time. This leads to an effective radial velocity component; the latter depends on b. Most of the values of the axial velocity of the vortex rings lie between the theoretically predicted values corresponding to the late stage of vortex ring development and b=1/4 (fully developed turbulence) and 1/2 (laminar case).

Atomization and Sprays

The fully Lagrangian approach (FLA) to the calculation of the number density of inertial particle... more The fully Lagrangian approach (FLA) to the calculation of the number density of inertial particles in dilute gas-particle flows is implemented into the CFD code ANSYS Fluent. The new version of ANSYS Fluent is applied to modelling dilute gas-particle flow around a cylinder and liquid droplets in a gasoline fuel spray. In a steady-state case, the predictions of the FLA for the flow around a cylinder and those based on the equilibrium Eulerian method (EE) are almost identical for small Stokes number, Stk, and small Reynolds number, Re, (Re = 1, Stk = 0.05). For the larger values of these numbers (Re = 10, 100; Stk = 0.1, 0.2) the FLA predicts higher values of the gradients of particle number densities in front of the cylinder compared with the ones predicted by the EE. For transient flows (Re = 200), both methods predict high values of the number densities between the regions of high vorticity and very low values in the vortex cores. For Stk ≥ 0.1 the maximal values predicted by FLA are shown to be several orders of magnitude higher than those predicted by the EE. An application of FLA to a direct injection gasoline fuel spray has focused on the calculation of the number densities of droplets. Results show good qualitative agreement between the numerical simulation and experimental observations. It is shown that small droplets with diameters dp = 2 µm tend to accumulate in the regions of trajectory intersections more readily, when compared with larger droplets (dp = 10 µm, dp = 20 µm). This leads to the prediction of the regions of high number densities of small droplets.

The paper presents a new approach to the modelling of heating and evaporation of dual-fuel drople... more The paper presents a new approach to the modelling of heating and evaporation of dual-fuel droplets with a specific application to blends of biodiesel (represented by the widely used soybean methyl ester, SME) and Diesel fuels in conditions representative of internal combustion engines. The original compositions, with up to 105 components of Diesel and biodiesel fuels, are replaced with a smaller number of components and quasi-components using the recently introduced multi-dimensional quasi-discrete (MDQD) model. Transient diffusion of these components and quasi-components in the liquid phase and temperature gradient and recirculation inside droplets are taken into account. The results are compared with the predictions of the case when blended biodiesel/Diesel fuel droplets are represented by pure biodiesel fuel or pure Diesel fuel droplets. It is shown that droplet evaporation time and surface temperature predicted for 100% SME, representing pure biodiesel fuel, are close to those ...

International Journal of Heat and Mass Transfer, 2018

Fuel, 2016

International Communications in Heat and Mass Transfer, 2014

International Journal of Heat and Mass Transfer, 2014

Procedia IUTAM, 2013

Proceeding of the 6th International Symposium on Radiative Transfer, 2012

International Journal of Heat and Mass Transfer, 2010

International Journal of Engineering Systems Modelling and Simulation, 2010

International Journal of Engine Research, 2009

Fuel, 2014

European Journal of Mechanics - B/Fluids, 2010

Atomization and Sprays, 2010

Journal of Heat Transfer, 2007

Asian Journal of Scientific Research, 2013

· SAE International Journal of Fuels and Lubricants, 2010

Atomization and Sprays

Previously developed droplet heating and evaporation models, taking into account temperature grad... more Previously developed droplet heating and evaporation models, taking into account temperature gradient, recirculation, and species diffusion within droplets, and their application to the analysis of commercial automotive fuel droplets are reviewed. It is shown that the most efficient analysis of Diesel fuel droplet heating and evaporation is based on the MDQD (multi-dimensional quasi-discrete) model, taking into account the contribution of all groups of hydrocarbons in automotive fuels. The main features of this model are summarised and its new application to the analysis of droplets in Diesel engine-like conditions, taking into account time-dependent velocities, is described. In the MDQD model, Diesel fuel is approximated by six groups of components: alkanes, cycloalkanes, bicycloalkanes, alkylbenzenes, indanes & tetralines, naphthalenes, and three characteristic components C19H34 (tricycloalkane), C13H12 (diaromatic), and C14H10 (phenanthrene). It is shown that errors in estimated temperatures and evaporation times in typical Diesel engine conditions, using the approximation of Diesel fuel by 15 quasi-components/components compared to the case when all 98 components are taken into account, are up to 1% and 3%, respectively. This is acceptable in most engineering applications. This approximation has also reduced CPU time by about 6 times compared with the case when the contribution of 98 components is taken into account. The approximations of Diesel fuel with n-dodecane (widely used in engineering modelling) and 20 alkane components lead to under-prediction of the evaporation time by over 50% and 22%, respectively.

"A detailed comparative analysis of transport and thermodynamic properties of biodiesel fuels and... more "A detailed comparative analysis of transport and thermodynamic properties of biodiesel fuels and
components of these fuels is presented. Five types of biodiesel fuels are considered: Palm Methyl
Ester, produced from palm oil; Hemp Methyl Esters, produced from hemp oil in the Ukraine and
European Union; Rapeseed oil Methyl Ester, produced from rapeseed oil in the Ukraine; and Soybean
oil Methyl Ester, produced from soybean oil. Up to 16 components (methyl esters in most cases) of
these fuels are considered. The results are applied to the analysis of biodiesel fuel droplet heating and
evaporation in conditions relevant to internal combustion engines, using the model described
elsewhere."

New results of the investigation of biodiesel fuel droplet heating and evaporation, using previou... more New results of the investigation of biodiesel fuel droplet heating and evaporation, using previously developed models, are presented. Temperature gradient, recirculation and species diffusion within the droplets are taken into account. The results of calculations, taking into account the contribution of all components of biodiesel fuels (up to 16) and assuming that these fuels can be treated as a one component fuel, are discussed. It is pointed out that there are serious problems with the application of the approach, based on the analysis of diffusion of individual components, to the modelling of heating and evaporation of realistic Diesel fuel droplets, as the latter include more than 100 components. In our earlier papers, a new approach to the modelling of heating and evaporation of multi-component droplets, suitable for the case when a large number of components are present in the droplets, was suggested. This approach was based on the introduction of quasi-components, and the model was called the 'quasi-discrete' model. It is pointed out that there are two main problems with the application of the quasi-discrete model to realistic Diesel fuels. Firstly, even if we restrict our analysis to alkanes alone, it appears not to be easy to approximate this distribution with a reasonably simple distribution function. Secondly, the contributions of other hydrocarbon families in addition to alkanes cannot be ignored in any realistic model of Diesel fuels. Some results of the development of the generalised multi-dimensional version of the quasi-discrete model and its application to realistic Diesel fuel droplets are presented.

Outline 2  Background  Motivation  Basic equations  Results  Conclusions 3  Ignition and co... more Outline 2  Background  Motivation  Basic equations  Results  Conclusions 3  Ignition and combustion Processes in the Combustion Chamber of an IC Engine Heating and evaporation processes preceding the onset of combustion in IC engines Secondary breakups Primary breakup Liquid fuel jet break-up  Droplet break-up  Heating of droplets  Evaporation of droplets 4  Temperature gradient inside droplets have been ignored;  Species diffusions inside droplets have been assumed to be infinitely large or multi-components fuels were approximated by single components;

The main features of the previously developed model for two-component droplet heating and evapora... more The main features of the previously developed model for two-component droplet heating and evaporation into a
neutral gas (nitrogen) are summarised. The results of functionality testing of this model for heat and mass transfer
between two parallel plates are reviewed. New results of the application of the model to the analysis of a twocomponent
(n-dodecane and p-dipropylbenzene) droplet’s heating and evaporation in a high pressure background
gas (nitrogen) in Diesel engine-like conditions are presented. As in the case of the previously developed similar
models, the model used in the analysis is based on the introduction of the kinetic region in the immediate vicinity of
the droplets and the hydrodynamic region. The model is tested for the analysis of heating and evaporation of a droplet
with initial radius and temperature equal to 5 μm and 300 K, respectively, immersed into gas with temperatures 1000
K and 700 K for several mixtures of n-dodecane and p-dipropylbenzene. It is shown that the increase in mass
fraction of p-dipropylbenzene and kinetic effects lead to the increase in predicted droplet evaporation time. It is shown
that the kinetic effects increase with increasing gas temperature and molar fraction of p-dipropylbenzene.