scholarly journals Modeling and Simulation of Janus-like Nanoparticles Formation by Solid-Gas Exothermic Reactions

2021 ◽  
Vol 23 (3) ◽  
pp. 133
Author(s):  
A.A. Markov ◽  
K.S. Martirosyan
Keyword(s):  
Formation Rate ◽  
Initial Porosity ◽  
Combustion Model ◽  
Gas Temperature ◽  
Exothermic Reactions ◽  
Carbon Combustion ◽  
Two Phases ◽  
Experimental Values ◽  
Micro Structures ◽  
Expansion Effect

Theoretical model for the simulation of synthesis of Janus-like particles (JP) consisting two different phases using the Carbon Combustion Synthesis of Oxides (CCSO) is presented. The model includes the variation of sample initial porosity, carbon concentration and oxygen flow rate used to predict the formation of JP features. The two temperature (2T) combustion model of chemically active submicron-dispersed mixture of two phases including ferroelectric and ferromagnetic was implemented and assessed by using the experimentally estimated activation energy of 112±3.3 kJ/mol and combustion temperature. The experimental values allowed to account the thermal and concentration expansion effect along with the dispersion by the slip-jump simulation for high Knudsen numbers. The model predicted that the smaller initial porosity of the combustion media creates higher formation rate of Janus-like particles. The simulation of slippage and jumps of the gas temperature allowed the scale-bridging between macro- and micro- structures.

Analysis of Incylinder Pressure and Temperature Variation in a Four-Stroke S. I. Engine Using Wiebe’s Combustion Model

2014 ◽  
Vol 984-985 ◽  
pp. 957-961
Author(s):  
Vijayashree ◽  
P. Tamil Porai ◽  
N.V. Mahalakshmi ◽  
V. Ganesan
Keyword(s):  
Heat Release ◽  
Combustion Process ◽  
Pressure Variation ◽  
Spark Ignition Engine ◽  
Working Fluid ◽  
Combustion Model ◽  
Cylinder Pressure ◽  
Crank Angle ◽  
Experimental Values ◽  
Release Model

This paper presents the modeling of in-cylinder pressure variation of a four-stroke single cylinder spark ignition engine. It uses instantaneous properties of working fluid, viz., gasoline to calculate heat release rates, needed to quantify combustion development. Cylinder pressure variation with respect to either volume or crank angle gives valuable information about the combustion process. The analysis of the pressure – volume or pressure-theta data of a engine cycle is a classical tool for engine studies. This paper aims at demonstrating the modeling of pressure variation as a function of crank angle as well as volume with the help of MATLAB program developed for this purpose. Towards this end, Woschni heat release model is used for the combustion process. The important parameter, viz., peak pressure for different compression ratios are used in the analysis. Predicted results are compared with experimental values obtained for a typical compression ratio of 8.3.

scholarly journals Modelling of Moisture Sorption by Cfrp Rebars with Vinylester Matrix

2004 ◽  
Vol 13 (6) ◽  
pp. 096369350401300 ◽  
Author(s):  
Olesja Starkova ◽  
Andrey Aniskevich
Keyword(s):  
Moisture Sorption ◽  
Sorption Process ◽  
Suggested Model ◽  
Sorption Data ◽  
High Anisotropy ◽  
Three Phase ◽  
Anisotropy Effect ◽  
Diffusion Character ◽  
Two Phases ◽  
Experimental Values

The results of experimental investigation and modelling of moisture sorption by CFRP rebars and vinylester matrix are presented. Experimental values of the rebar diffusion coefficients essentially differ from those predicted using structural approach. Essential anisotropy of sorption process in longitudinal and transverse directions is observed. Quasi three phase model is suggested for description of the CFRP rebar sorption. The model is based on consideration of sorption process of the diffusion character in the composite consisted of two phases: resin and microplastic, which includes fibres and fibre-resin interphase. The suggested model describes the experimental sorption data quite satisfactorily and explains high anisotropy effect.

scholarly journals Thermodynamic Features of the Intensive Formation of Hydrocarbon Hydrates

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3396
Author(s):  
Anatoliy M. Pavlenko
Keyword(s):  
Gas Hydrate ◽  
Formation Rate ◽  
Phase Interface ◽  
Boundary Surface ◽  
Hydrate Formation ◽  
Water Medium ◽  
Gas Temperature ◽  
Mixing Processes ◽  
Gas Hydrate Formation ◽  
Bubble Sizes

This paper presents the results of a study on the influence of pressure and temperature of the gas–water medium on the process of hydrocarbon gas hydrate formation occurring at the phase interface. Herein, a mathematical model is proposed to determine the optimum ratios of pressure, gas temperatures, water, and gas bubble sizes in the bubbling, gas ejection, or mixing processes. As a result of our work, we determined that gas hydrate in these processes is formed at the gas–water interface, that is, on the boundary surface of gas bubbles. Moreover, there is a gas temperature range where the hydrate formation rate reaches its maximum. These study findings can be used to optimize various technological processes associated with the production of gas hydrates in the industry.

Calculation of Two-Phase Flow in Gas Turbine Combustors

1995 ◽  
Vol 117 (4) ◽  
pp. 695-703 ◽  
Author(s):  
A. K. Tolpadi
Keyword(s):  
Gas Turbine ◽  
Gas Phase ◽  
High Power ◽  
Liquid Droplet ◽  
Frame Of Reference ◽  
Curvilinear Coordinates ◽  
Combustion Model ◽  
Gas Temperature ◽  
Two Phase ◽  
Phase Calculation

A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-ε turbulence model, and a combustion model comprising an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. This two-phase model was applied to a real piece of combustion hardware in the form of a modern GE/SNECMA single annular CFM56 turbofan engine combustor. For the purposes of comparison, calculations were also performed by treating the fuel as a single gaseous phase. The effect on the solution of two extreme situations of the fuel as a gas and initially as a liquid was examined. The distribution of the velocity field and the conserved scalar within the combustor, as well as the distribution of the temperature field in the reaction zone and in the exhaust, were all predicted with the combustor operating both at high-power and low-power (ground idle) conditions. The calculated exit gas temperature was compared with test rig measurements. Under both low and high-power conditions, the temperature appeared to show an improved agreement with the measured data when the calculations were performed with the spray model as compared to a single-phase calculation.

Numerical Investigations of NOx Emissions of a Partially Premixed Burner for Natural Gas Operations in Industrial Gas Turbine

2014 ◽  
Author(s):  
Alessandro Innocenti ◽  
Antonio Andreini ◽  
Andrea Giusti ◽  
Bruno Facchini ◽  
Matteo Cerutti ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Turbulent Combustion ◽  
Fuel Injection ◽  
Formation Rate ◽  
Operating Conditions ◽  
Combustion Model ◽  
Nox Emissions ◽  
Air Concentration ◽  
Partially Premixed ◽  
Industrial Gas Turbine

In the present paper a numerical analysis of a low NOx partially premixed burner for industrial gas turbine applications is presented. The first part of the work is focused on the study of the premixing process inside the burner. Standard RANS CFD approach was used: k–ε turbulence model was modified and calibrated in order to find a configuration able to fit available experimental profiles of fuel/air concentration at the exit of the burner. The resulting profiles at different test points have been used to perform reactive simulations of an experimental test rig, where exhaust NOx emissions were measured. An assessment of the turbulent combustion model was carried out with a critical investigation of the expected turbulent combustion regimes in the system and taking into account the partially premixed nature of the flame due to the presence of diffusion type pilot flames. A reliable numerical setup was discovered by comparing predicted and measured NOx emissions at different operating conditions and at different split ratio between main and pilot fuel. In the investigated range, the influence of the premixer in the NOx formation rate was found to be marginal if compared with the pilot flame one. The calibrated numerical setup was then employed to explore possible modifications to fuel injection criteria and fuel split, with the aim of minimizing exhaust NOx emissions. This preliminary numerical screening of alternative fuel injection strategies allowed to define a set of advanced configurations to be investigated in future experimental tests.

Enabling Air-Path Systems for Homogeneous Charge Compression Ignition (HCCI) Engine Transient Control

2009 ◽  
Author(s):  
Fengjun Yan ◽  
Junmin Wang
Keyword(s):  
Cost Effective ◽  
Combustion Model ◽  
Gas Temperature ◽  
Independent Control ◽  
Variable Geometry Turbocharger ◽  
Hcci Engine ◽  
Engine Simulation ◽  
Hcci Combustion ◽  
Transient Control ◽  
Path System

This paper explores the possibility of using a cost-effective air-path system that includes a dual-loop (exhaust gas recirculation) EGR and a (variable geometry turbocharger) VGT to achieve independent control of the main in-cylinder charge conditions (i.e. in-cylinder oxygen, inert gas amounts, and gas temperature at the intake valve closing) for HCCI engine combustion transient operation. An engine simulation model consisting of the air-path system and a HCCI combustion model was developed and synthesized to evaluate the control authority of the air-path system on the in-cylinder charge conditions as well as their effects on combustion. A variety of simulations unveiled that such an air-path system can enable independent control of the main in-cylinder charge conditions and active compensation of the effects of the wall temperature variations on HCCI combustion.

scholarly journals Larde-Eddy Simulation of Flame Dynamics During the Ignition of a Swirling Injector Unit and Comparison with Experiments

2020 ◽  
Author(s):  
Karl Toepperwien ◽  
Felix Collin-Bastiani ◽  
Eleonore Riber ◽  
Benedicte Cuenot ◽  
Guillaume Vignat ◽  
...  
Keyword(s):  
Sudden Expansion ◽  
Combustion Model ◽  
Positive Pressure ◽  
Rapid Reduction ◽  
Volumetric Expansion ◽  
Eddy Simulation ◽  
Initial Penetration ◽  
Lift Off ◽  
Two Phases ◽  
Injection Unit

Abstract During the ignition of a swirled single-injector combustor, two phases have been identified experimentally. In the first, the flame penetrates the injection unit, while in the second the flame lifts off after a substantial delay before stabilizing at a distance from the injector. This transient phenomenon is investigated using Large Eddy Simulations based on an Euler-Lagrange description of the liquid spray, an energy deposition model to mimic ignition and the thickened flame combustion model. It is shown that the initial penetration of the flame in the injector unit is linked with the positive pressure excursion induced by the rapid volumetric expansion of burnt gases. This sudden expansion is itself due to the fast increase in heat release rate that occurs during the initiation of the process. The corresponding positive and negative pressure disturbances induce a rapid reduction of the mass flow rate through the injector, followed by an acceleration of the flow and a return to the nominal value. It is also shown that the flame root disappears after another delay, which results in the flame edge lifting and stabilization at a distance from the injector exhaust corresponding to steady operation of the device. The relatively long delay time before this lift-off takes place is found to correspond to the residence time of the cooled burnt gases in the vicinity of the chamber walls, which are ultimately entrained by the internal recirculation zone and quench the lower flame foot.

scholarly journals The Three Hundred project: the stellar and gas profiles

2020 ◽  
Vol 495 (3) ◽  
pp. 2930-2948 ◽  
Author(s):  
Qingyang Li ◽  
Weiguang Cui ◽  
Xiaohu Yang ◽  
Elena Rasia ◽  
Romeel Dave ◽  
...  
Keyword(s):  
Formation Rate ◽  
Analytical Models ◽  
Radial Dependence ◽  
Gas Temperature ◽  
Self Similarity ◽  
Density Profiles ◽  
Hydrodynamic Simulations ◽  
Cluster Centre ◽  
Centre Region ◽  
Stellar Density

ABSTRACT Using the catalogues of galaxy clusters from The Three Hundred project, modelled with both hydrodynamic simulations (gadget-x and gadget-music), and semi-analytical models (SAMs), we study the scatter and self-similarity of the profiles and distributions of the baryonic components of the clusters: the stellar and gas mass, metallicity, the stellar age, gas temperature, and the (specific) star formation rate. Through comparisons with observational results, we find that the shape and the scatter of the gas density profiles matches well the observed trends including the reduced scatter at large radii which is a signature of self-similarity suggested in previous studies. One of our simulated sets, gadget-x, reproduces well the shape of the observed temperature profile, while gadget-music has a higher and flatter profile in the cluster centre and a lower and steeper profile at large radii. The gas metallicity profiles from both simulation sets, despite following the observed trend, have a relatively lower normalization. The cumulative stellar density profiles from SAMs are in better agreement with the observed result than both hydrodynamic simulations which show relatively higher profiles. The scatter in these physical profiles, especially in the cluster centre region, shows a dependence on the cluster dynamical state and on the cool-core/non-cool-core dichotomy. The stellar age, metallicity, and (s)SFR show very large scatter, which are then presented in 2D maps. We also do not find any clear radial dependence of these properties. However, the brightest central galaxies have distinguishable features compared to the properties of the satellite galaxies.

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