Simulation Of Technological Processes Research Articles

Mathematical Research of the Phase Transformation Kinetics of Alloyed Steel

Regulation of the process parameters allows obtaining the required properties of the metal. A computer simulation of technological processes with allowance for structural and phase transformations of the metal forms the basis for the proper choice of those parameters. The purpose of the paper is to study the main diffusion and diffusion-free transformation processes in alloyed steels during heating and cooling using the methods of mathematical modeling. A comparative analysis of the kinetic equations of phase transformations including the Kolmogorov–Avrami and Austin–Rickett equations that describe in different ways the dependence of the diffusion transformation rate on the time and the attained degree of transformation is carried out. It is shown that the Austin–Rickett equation is equivalent to the Kolmogorov–Avrami equation with a smooth decrease of the Avrami exponent during the transformation process. The advantages of the Kolmogorov–Avrami equation for modeling the kinetics of ferrite-pearlite and bainite transformations and the validity of this equation for modeling the kinetics of martensite transformations during tempering are shown. The parameters for describing the tempering process of steel 35 at different temperatures are determined. The proposed model is compared with equations based on the Hollomon–Jaffe parameter. The diagrams of martensitic transformation of alloyed steels and the disadvantages of the Koistinen–Marburger equation used to describe them are analyzed. The equations of the temperature dependence of the degree of transformation, similar to the Kolmogorov–Avrami and Austin–Rickett equations, are derived. The equations contain the minimum set of the parameters that can be found from published data. An iterative algorithm for determining parameters of the proposed model providing the minimum rms deviation of the constructed dependence from the initial experimental data is developed. The dependence of the accuracy of approximation on the temperature of the onset of transformation is presented. The complex character of the martensitic transformation development in alloyed steels is revealed. The advantage of using equations of the Austin–Rickett type when constructing models with a limited amount of experimental data is shown. The results obtained make it possible to extend the approaches used in the modeling of diffusion processes of austenite decomposition to the description of the processes of martensite formation and decomposition in alloyed steels.

SudoDEM: Unleashing the predictive power of the discrete element method on simulation for non-spherical granular particles

This paper presents a novel open-source discrete element code, SudoDEM, for efficient modeling of both 2D and 3D non-spherical particles under a GPL v3 or later license. Built upon a popular open-source code YADE, our code inherits the core of a classic DEM framework empowered by OpenMP acceleration, and further offers unique features of a rich library of prime particle shapes, including poly-superellipsoids, superellipsoids, cylinders, cones, polyhedrons for 3D and disks and superellipses for 2D. Unlimited choices of more complex particle shapes can be readily generated by clumping these prime shapes. Efficient modeling of complex shaped particles hinges on contact detection. In SudoDEM, we have developed three generic and efficient contact detection algorithms, the parametric common normal (PCN) algorithm, the Gilbert–Johnson–Keerthi (GJK) algorithm, and the hybrid PCN–GJK algorithm, to handle contacts among complex-shaped particles during a typical DEM simulation. The new DEM code is validated and further showcased by multiple examples, including granular packing, triaxial compression, and landslide, its robustness, efficiency and versatility in providing realistic solutions to granular mechanics problems. The project is hosted at an open-source page at https://sudodem.github.io, while the source codes are freely available at a GitHub repository (https://github.com/SudoDEM). We foresee a great capability and potential for SudoDEM in advancing future progress in granular physics and granular mechanics and in fostering advanced simulations of critical engineering and industrial processes pertaining to granular media. Program summaryProgram title: SudoDEMCPC Library link to program files:https://doi.org/10.17632/brpk4g28zn.1Developer’s repository link:https://github.com/SudoDEM/SudoDEM, https://sudodem.github.ioLicensing provisions: GNU General Public License 3Programming language: C++, PythonNature of problem: Grain shape underpins important aspects of the physical and mechanical behaviors of granular media. The inability of realistic and robust modeling of particle shape has been a major obstacle for discrete-based numerical methods in solving practical problems of granular materials.Solution method: SudoDEM implements three generic algorithms of contact detection among non-spherical particles in Discrete Element Method, which provides a rich library of particle shapes available for DEM modeling of granular media.

Analysis of Radial Compressor Performance at Low Pressure Ratios and Compressor Choke

Abstract Strong transient engine load steps can result in low pressure ratio (ΠC) compressor operation for single stage turbocharged (TC) systems. For conventional full load TC engine matching using one-dimensional (1D)-engine process simulation, these operating points are of limited relevance and are consequently less studied. However, for the layout of sequential turbocharging systems, low pressure ratio compressor operation has to be thoroughly understood. Therefore, in this paper, three-dimensional (3D)-computational fluid dynamics (CFD) simulations will be presented, which analyze the stationary compressor behavior at low pressure ratios. Operating points at ΠC<1 are investigated by reducing the compressor outlet pressure. The simulation results are validated against measurement data acquired at a stationary hot gas test bench. The compressor performance is quantified by a corrected compressor torque. Opposed to the well-known operation at ΠC>1, the compressor generates power close to zero speed for ΠC<1 (turbine operation). At higher mass flowrates and ΠC<1, the compressor consumes power. Pressure build-up in the wheel is overcompensated by losses in the diffusor and the volute resulting in a net pressure drop across the stage. The 3D-CFD simulations also allow a speed-dependent evaluation of the choking cross section inside the compressor. At low circumferential speeds, compressor choke occurs in the volute or at the wheel outlet. At higher speeds, choking is observed at the wheel inlet. This behavior must be accounted for compressor map extrapolation methods for 1D-engine process simulations in order to correctly predict the choking mass flowrate.

A holistic consideration of turbocharger heat transfer analysis and advanced turbocharging modeling methodology in a 1D engine process simulation context

The focus on transient engine operation will increase to fulfill future emission requirements in the commercial vehicle sector. Accordingly, the transient turbocharger matching process is becoming increasingly important. The one-dimensional fluid dynamics (1D-CFD) simulation is established as an important development tool for matching the exhaust gas turbocharger to a combustion engine. The optimization of the modeling methodology of the combustion process and the turbocharger modeling are two key parameters to improve the reliability of the dynamic engine process simulation. In this paper, the advanced turbocharger (TC) methodology is described. This includes the determination of the adiabatic turbocharger performance from conventional hot gas test stand (HGS) measurement data, the derivation of an one-dimensional (1D) turbocharger heat transfer model and a method to physically extend the turbine map range. The adiabatic efficiencies of the turbocharger are determined with a model-based heat transfer correction of the conventional measured efficiencies from HGS measurement data. These adiabatic efficiency maps were used as a baseline to extend the conventional TC model with a heat transfer model taking into account of the engine boundary conditions in terms of temperature, pressure and mass flow rate. To assess the temperature distribution and the thermal inertia of the TC main components, in both stationary and transient engine operations, the variable geometry turbine (VGT) turbocharger hardware, installed on a medium-duty diesel engine, was equipped with several thermocouples on all accessible surfaces to make comprehensive surface temperature surveys. A 1D lumped capacitance heat transfer model (HTM) of the VGT TC was developed and validated against the experimental data from the engine test bench. To complete the advanced TC modeling, the turbine map is extended using experimental measurement data, based on extended HGS measurements, in combination with mathematically supported extrapolation. The results from the advanced turbocharger simulation methodology significantly improves the prediction of the temperature drop over the turbine in comparison to the conventional adiabatic TC simulation methodology. The validated heat transfer model also allows the analysis of the heat flow breakdown of the turbocharger. Based on the advanced turbocharger model, a tool for the improved transient turbocharger-engine matching process is given.

МОДЕЛЮВАННЯ ХІМІКО-ТЕХНОЛОГІЧНИХ ПРОЦЕСІВ У SCADA ЗА ДОПОМОГОЮ ТЕХНОЛОГІЇ OPEN PLATFORM COMMUNICATIONS

The subject of study in the article are methods for integrating mathematical models of chemical-technological processes implemented in universal modeling programs into modern SCADA systems for developing and improving methods for controlling these processes. The goal is to develop a control system for the synthesis of acetylene in a kinetic reactor, based on a computer model created in universal modeling programs and integrated into SCADA using open platform communications (OPC) technology. Tasks: to create a mathematical model of the process of synthesis of acetylene based on the selected universal modeling program; to develop a way to integrate the resulting model into modern SCADA using OPC technology; to develop in SCADA a control system for the process of synthesis of acetylene according to a mathematical model as part of a functional human-machine interface and control subsystem algorithms; get transient graphs and prove the efficiency of the control system. Conduct a process study using a mathematical model. The methods used are computer simulation of technological processes; OPC technology; SCADA based management. The following results are obtained. A control system for the acetylene synthesis process based on SCADA Trace-Mode and a mathematical model implemented in the ChemCAD package has been developed, while the model - control system information exchange is implemented based on OPC technology. Checked and proved the efficiency of the resulting control system. A mathematical study of the process was carried out, an experimental dependence of the yield of the final product, acetylene, on the temperature, and consumption of raw materials at the inlet of the reactor was established. Conclusions. The novelty of the results is as follows. A new method is proposed for integrating mathematical models implemented in the ChemCAD modeling package into modern SCADA, based on OPC technology. A study of the process of acetylene synthesis by a mathematical model was carried out, experimental dependences of the acetylene yield on temperature and ethylene consumption at the inlet of the synthesis reactor were obtained. An analysis of the obtained experimental dependences showed the need to use cascade control algorithms to increase the efficiency of controlling the process of acetylene synthesis in a kinetic reactor.

Analytical study on the influence of valve pumping work on engine efficiency

Driving cycles like WLTP and the consideration of real driving emissions increase the relevance of load-dependent process losses for the prediction of engine efficiency based on engine process simulation. The contribution of valve pumping work to the total gas exchange losses of an internal combustion engine is usually neglected during engine conception. However, its share of the total gas exchange power losses increases with engine load. Within this paper, the variation of load, engine speed and valve timings on valve pumping work is investigated on a theoretical basis using 1D-CFD-simulation for a three-cylinder turbo-charged gasoline engine. Further, the influence of the valve lift curve design on valve pumping work is evaluated. The consideration of valve pumping work can increase the accuracy of the engine efficiency prognosis based on engine process simulations. A comparison with results from the literature points out that 3D-CFD-based evaluations of the valve gas forces can provide even more accurate results than the conventional calculation approach which is presented within scope of this publication. Hence, future works on this subject might include the improvement of the standard calculation approach on an either physical or empirical basis considering valve and seat ring design details as parameters.

Analysis and assessment of the integrated generation IV gas-cooled fast nuclear reactor and copper-chlorine cycle for hydrogen and electricity production

This paper proposes the conceptual integration of a Generation IV nuclear reactor, the gas-cooled fast nuclear reactor, and the thermo-electrochemical copper-chlorine cycle, a Brayton cycle, and a Rankine cycle for hydrogen and electricity production. This paper analyzes the developed system thermodynamically, and energy and exergy efficiencies are used to measure the system performance. Here, the four-step thermo-electrochemical copper-chlorine cycle produces hydrogen through thermochemical water decomposition, and electricity via the Rankine and Brayton cycles. The produced hydrogen is then compressed to reduce its storage volume. The proposed system uses a heat exchanger network, which is incorporated within the hydrogen producing copper-chlorine cycle. With the heat recovery network, the heat from the nuclear reactor is delivered to only two reactors of the four-step copper-chlorine cycle. The proposed system is modeled and simulated with engineering process simulation software (Aspen Plus). The overall energy and exergy efficiencies of the system are 14.1% and 20.7%, respectively.

A phenomenological modelling framework for particle emission simulation in a direct-injection gasoline engine

A phenomenological modelling framework is presented that allows the simulation of the engine-out particle emissions of direct-injection gasoline engines based on physical principles. It is applicable both at steady-state operating conditions and in transient driving cycles. Within the modelling framework, a multi-zone model with gas-phase reaction kinetics is coupled with a stochastic reactor model considering the soot formation dynamics. Both model parts are fed with inputs from an accompanying engine process simulation. Particle emissions from injector deposits and inhomgeneous gaseous mixture preparation are taken into account. Pyrolysis reactions are considered in a zone with remaining fuel film at the injector, whereas in gas-phase zones that arise from inhomogeneous mixture preparation, the reaction of the air–fuel mixture is calculated under sub-stoichiometric conditions. The setup of those mixture-induced zones is generated by an existing homogenisation sub-model. The modelling framework is evaluated by test bench measurements of the engine operating map, a variation of engine actuator settings and transient driving profiles. Hereby, an accuracy of less than 20% deviation for particle number and mass is achieved.

Mathematical research of the phase transformation kinetics of alloyed steel

Regulation of the process parameters allows obtaining the desired properties of the metal. Computer simulation of technological processes with allowance for structural and phase transformations of the metal forms the basis for the proper choice of those parameters. Methods of mathematical modeling are used to study the main diffusion and diffusion-free processes of transformations in alloyed steels during heating and cooling. A comparative analysis of the kinetic equations of phase transformations including the Kolmogorov – Avrami and Austin – Rickett equations which describe in different ways the time dependence of the diffusion transformation rate and attained degree of transformation has been carried out. It is shown that the Austin – Rickett equation is equivalent to the Kolmogorov – Avrami equation with a smooth decrease of the Avrami exponent during the transformation process. The advantages of the Kolmogorov – Avrami equation in modeling the kinetics of ferrite-pearlite and bainite transformations and validity of this equation for modeling the kinetics of martensite transformations during tempering are shown. The parameters for describing the tempering process of steel 35 at different temperatures are determined. The proposed model is compared with equations based on the Hollomon – Jaffe parameter. The diagrams of martensitic transformation of alloyed steels and disadvantages of the Koistinen – Marburger equation used to describe them are analyzed. The equations of the temperature dependence of the transformation degree, similar to the Kolmogorov – Avrami and Austin – Rickett equations, are derived. The equations contain the minimum set of the parameters that can be found from published data. An iterative algorithm for determining parameters of the equations is developed, providing the minimum standard deviation of the constructed dependence from the initial experimental data. The dependence of the accuracy of approximation on the temperature of the onset of transformation is presented. The complex character of the martensitic transformation development for some steels is revealed. The advantage of using equations of the Austin – Rickett type when constructing models from a limited amount of experimental data is shown. The results obtained make it possible to extend the approaches used in modeling diffusion processes of austenite decomposition to description of the processes of formation and decomposition of martensite in alloyed steels.

Application of a combined physical and data-based model for improved numerical simulation of a medium-duty diesel engine

The one-dimensional computational fluid dynamics (1D-CFD) simulation is an important development tool for improving the matching process of the exhaust gas turbocharger with a combustion engine. To meet future emission requirements of commercial vehicles, an increasing focus on transient operation conditions is given. For example, a faster boost pressure build-up allows higher exhaust gas recirculation rates during load steps—improving transient nitrogen oxides ($$\hbox {NO}_x$$) emissions. According to this, the matching process of the turbocharger focuses increasingly on the transient operation conditions of combustion engines. To increase the quality of the dynamic engine process simulation, the simulation model should be optimized with regard to the quality of the engine’s high-pressure process including emissions as well as the turbocharger modeling methodology. This paper focuses on the application of an approach that combines a data-based combustion model for the $$\hbox {NO}_x$$ and soot values and the high-pressure part of the working process with a physical description of the gas exchange. To generate the data for the combustion model, an extensive measurement campaign of all relevant parameters was carried out on a medium-duty diesel single-cylinder research engine. The developed model was integrated into a multi-cylinder engine (MCE) simulation environment and validated on the basis of corresponding MCE measurements. The sensitivities of the model were examined for the input parameters. The data-based combustion model demonstrates a high accuracy in emissions and high-pressure working process modeling both in the wide range of the engine map and under transient operating conditions as well as for different engine calibration strategies. As a result, a good baseline for the improved transient combustion simulation is provided.

Heat exchange simulation in energy zones of a rotarykiln with change of heat resistance of the body

The object of research is high-temperature thermal units – rotary kilns. Rotary kilns are used in various industries. The specified equipment has high energy consumption, which is due to the operating conditions of the kiln units in compliance with a number of technological requirements for thermal conditions. At the same time, the problem of high energy intensity is aggravated by the low level of useful energy resources. One of the most problematic places is the thermal and operational characteristics of rotary kilns, as well as the use of lining with increased thermal resistance.Physical and mathematical models are used. It is proposed to calculate a rotary kiln for the production of cement with a size of 5x185 m and a capacity of 75 t/h. A mathematical model is obtained for computer simulation of technological processes in rotary cement kilns. The possibilities of reducing fuel consumption by increasing the thermal resistance of the lining of a rotary kiln are considered. The most energy-intensive zones are determined and the effect on the thermal efficiency of using additional thermal insulation in various energy zones in a rotary kiln is analyzed. Calculations and the results of a numerical experiment are presented. The most rational areas for the use of lining with additional thermal insulation are determined. It is found that with the integrated application of the proposed method, fuel consumption in a thermal unit can be reduced by 9 %. And an increase in the thermal resistance of the lining installed in high temperature zones will increase the energy efficiency of the thermal unit. A significant advantage of this method is the fact that an increase in kiln productivity does not require additional fuel consumption, an increase in temperature, or an increase in the enthalpy of combustion products.In the future, it is planned to study the mechanism for establishing a heat-insulating layer in the refractories of the lining, determining their optimal thermal efficiency and stress-strain state to eliminate the possibility of destruction. As well as determining the optimal structural form of the refractory and the cell with thermal insulation.

Effect of burrowing crabs on retention and accumulation of soil carbon and nitrogen in an intertidal salt marsh

Ecosystem engineers that affect other organisms by creating, modifying, maintaining or destroying habitats have received widespread attention. Understanding natural ecosystems and the way in which ecosystem engineers shape the environment is important to ecological restoration based on key ecosystem processes. Increasing studies has shown that crabs in intertidal salt marsh can act as ecosystem engineers, affecting the geomorphological processes and spatial heterogeneity of tidal flat. In this study, field investigations and manipulative experiments were conducted to explore how crab burrowing activity affects intertidal microtopography and soil carbon and nitrogen in the intertidal salt marshes. The results showed that crab burrowing activity is one of the key factors influencing concave-convex microtopography, which could intercept plant detritus and subsequently influencing the retention and accumulation of soil carbon and nitrogen. When compared to areas of flat microtopography with few or no crab burrows, soil organic carbon content (SOC), soil inorganic carbon content (SIC), total carbon content (TC), and total nitrogen content (TN) in adjacent areas of concave-convex microtopography with high density crab burrows were all significantly higher. Artificial simulation of ecosystem engineering processes could also change the geomorphological features of tidal flats and improve the retention and accumulation of soil carbon and nitrogen, which could also attract more crabs to burrow and settle down, then generate and maintain the concave-convex microtopography. Taken together, the results of this study provide scientific and effective implication and guidance for the restoration of coastal salt marshes.

Математическая модель процесса горения жидкого органического энергоносителя

Simulation of technological processes involving the combustion of liquid energy products with an attempt to accurately describe their hydrodynamics is known to greatly complicate the model. In this article, we discuss the problem of effective use of organic energy products. A mathematical model describing the combustion process of liquid fuel is presented. The modelling is carried out using a number of justified simplifying assumptions, which permit the original model to be reduced to simpler dependencies between the parameters of the process. The constructed model includes a stationary model of the combustion process and that of liquid fuel burning in a furnace. Key factors affecting the character of the process are investigated. A formula for calculating the oxygen concentration at the reaction surface is obtained. The combustion rate under consideration was assumed to be determined not only by the oxygen concentration in the diffusion layer, but also by the total surface of unreacted particles, calculated taking into account the density of the particle distribution. The material balance of oxygen is drawn, which includes two equations, i.e. for the diffusion and dense parts. The results of the calculations are presented in the form of diagrams. An engineering computational model has been developed for calculating the energy characteristics of the combustion of liquid hydrocarbon fuel in an industrial furnace. The resulting combustion model can be used for predicting the extent and consequences of emergency situations.

Chemical engineering process simulation of brines using phase diagram and Pitzer model of the system CaCl2[sbnd]SrCl2[sbnd]H2O

The phase equilibria of the system CaCl2SrCl2H2O at 288.15 K were investigated with the isothermal dissolution equilibrium method. The Pitzer model for system CaCl2SrCl2H2O from 288.15 K to 373.15 K was constructed by combining the results from the literature. In the model for the ternary system, the solid solution formed at low temperatures was considered as ideal solid solution and the temperature dependence equations for the mixing parameters θCa,Sr and ΨCa,Sr,Cl were built over the temperature range 288.15–373.15 K. The model for mixed system gives a very good agreement with the experimental solubility data presented in this work and those in the literature. The phase diagram and Pitzer model were then used to conduct computer simulation of brine separation. The separation process route was demonstrated at single temperature 288.15 K and multiple temperatures. The salts SrCl2·6H2O and CaCl2·6H2O with high purity were separated from the brine by re-crystallization method with the model at 288.15 K. The salts SrCl2·H2O and CaCl2·6H2O were also separated from the solution at 288.15 K and 323.15 K.

Utilizing Simtronics, a chemical engineering process simulation software, in chemical engineering coursework to reduce the skills gap

AbstractTo connect theory taught in the classroom and practical skills required for the workforce, a new teaching methodology has been adopted in the Department of Chemical Engineering at the University of Pittsburgh at Johnstown. We have introduced Simtronics, a virtual chemical engineering process simulator, in chemical engineering coursework to teach students how to operate equipment and troubleshoot chemical processes often found in industrial settings. The students then learn the theories and calculations, and how to apply them to the studied processes at varying conditions. The analysis of these varying conditions provides the student with valuable hands‐on experience frequently sought after by employers.

Planning of numerical and physical experiment in simulation of technological processes

Technological processes are multifactorial. The choice of the most significant of them for the correct analysis of the object of research is an important task. For such a ranking of factors, researchers usually rely on their own experience or the opinions of specialists in this field, assessing their consistency in terms of mathematical criteria. However, when developing a new process, this approach can not be used. In this case, experimental methods of selecting factors are preferable. But the cost, duration, and sometimes impossibility of using this method is obvious. In this paper we use a different approach. It was considered that thermodynamic modeling is an experiment, but only numerical. Therefore, you can apply it to the method of mathematical design of the experiment, allowing for one calculation to take into account the effect on the objective function of more than a dozen factors. The partial dependencies of the process indices obtained in this case make it possible, without setting up physical experiments, to weed out insignificant factors and leave strong ones, estimating them by the methods of mathematical statistics. Another important advantage of its application is the ability to evaluate the dynamics of changes in phase and elementary products of smelting, process feasibility according to convection and temperature conditions with the control of and mathematical criterion of the acquired data. The method also allows the process to be controlled by all the factors involved, which cannot be met in everyday modeling. For demonstration, this approach was applied during the development of the ferroborone production technology by carbothermic method using local raw materials. Thermodynamic modeling was performed using pre-selected factors. They were also used in physical simulation of the process in a high-temperature furnace. The experiment confirmed significance of the factors, which were chosen theoretically. The use of the planning method also reduced the number of numerical experiments in 25, and physical – in 125 times for predefined data.Using this approach, the authors have made it possible to compare the obtained data with the results of physical experiment to develop measures to approximate practical results to equilibrium ones with the use of strongly acting factor.

Multizone Model Study for DI Diesel Engine Running on Diesel-Ethanol-Biodiesel Blends of High Ethanol Fraction

A multizone combustion model for closed cycle of a DI diesel engine is developed to interpret the experimental investigations on the utilization of diesel-ethanol-biodiesel blends of high ethanol fraction (DEB blends). A computer-based programming for engine process simulation is developed in MATLAB. The model is validated with the experimental values of cylinder pressure and heat release rate. Important information related to fuel injection and combustion inside the combustion chamber, is revealed through the model prediction which is normally difficult to get from the experiments. Model prediction shows that the rate of fuel evaporation is higher for DEB blends, than diesel fuel at any instant of time. The fuel combustion is started late for DEB blends compared to diesel fuel, however, once the combustion is started the burning rate is higher than the diesel fuel. The droplet size (Sauter mean diameter) is decreased for DEB blends which indicate improved fuel atomization. The mean temperature in the zone is significantly lower for DEB blends compared to diesel fuel. The equivalence ratio in the zone is decreased for DEB blends proving that engine runs leaner. The equivalence ratio trend is not uniform as it depends on the combination of the rate of fuel evaporation, rate of air entrainment and rate of burning. Soot density is remarkably decreased, and NOx formation is also drastically reduced for DEB blends at different instant of time. The predictions help to interpret the experimental results for DEB blends and its comparison with diesel fuel.

Моделирование микро- и наноструктуры поверхности для решения задач газовой динамики и тепломассообмена

This paper is devoted to the problem of modeling a rough surface to ensure calculations for a flow around aircraft by high-enthalpy gas. The surface layer’s geometric characteristics along with the material’s chemical composition affect the surface’s optical indices and catalytic properties, and, consequently, on the measured heat flux. The problem of construction a geometric model for micro-surface has both fundamental and applied aspects. The fundamental nature stems from the fact that considered processes arising from the interaction of gas atoms and molecules with the surface are very complex ones. In such a case the correct interpretation for results of aircraft fragments’ ground experimental method is required. The work’s applied significance is determined by the need to optimize tools for flows diagnostic in high-enthalpy installations, in which simulation of thermal load affecting the aircraft in flight is taking place, as well as simulation of technological processes for heat-shielding materials and coatings development. Effective way for modeling of undifferentiated surfaces for gas dynamics problems solving is the use of fractal methods accounting the roughness at the micro- and nano-scale. They are based on the assertion that the natural surface’s structure has the same fractality at all levels. The development of this hypothesis has led to the emergence of a whole direction – material engineering – allowing most adequately describe self-organizing structures. Also, with the development of nanotechnologies, fractal geometry has found its own place in solving problems related to obtaining certain materials properties. As has been shown in the paper, fractal theory is a good mathematical tool for study of rigid bodies’ surface geometry and mechanisms influencing on the obtaining surface structure.

Laminar flame properties of C1-C3 alkanes/hydrogen blends at gas engine conditions

The use of fuel blending is encouraged in order to achieve more flexibility in gas engines. In order to design such engines effectively, relevant information about the laminar flame speeds and laminar flame thickness are necessary. Hydrodynamic and thermo-diffusive instabilities at gas engine conditions prevent the acquisition of reliable data experimentally. One-dimensional numerical simulations with detailed chemistry can be a solution. A huge database of laminar flame speeds is generated covering a broad range of gas engine applications, pressure (p) 0.1–20 MPa, fresh gas temperature (Tu) 300–1100 K, air-fuel equivalence ratio (λ) 0.9–2.5, methane 100–60 vol%, ethane 0–40 vol%, propane 0–40 vol%, hydrogen 0–30 vol% and exhaust gas recirculation (EGR) 0–30 m%. The detailed reaction mechanisms GRI 3.0 and AramcoMech 1.3 are used for the generation of flame speed data for the mentioned conditions. A laminar flame speed correlation for 100% hydrogen extending up to elevated pressure and temperature conditions is developed. A blending law based on Le Chatelier’s rule is investigated. It is observed that the HC-ratio has a very determining effect for the laminar flame properties of different C1-C3 alkane blends. Based on this observation, it was possible to derive a very efficient correlation for both laminar flame speed and laminar flame thickness for the group of natural gas blends with methane, ethane, propane and hydrogen, and as well as including relevant EGR, which corresponds within 7% accuracy to the calculated database of about 73,000 points. The developed laminar flame speed correlation is incorporated in an engine process simulation code. It is validated with the measured in-cylinder pressure traces from the single cylinder research engine experiments for different gas blends and EGR ratios.

Multiple-criteria decision analysis of the transformable low-rise building technological construction process

One of the promising areas of improving the constructive and technological solutions of low-rise buildings is the fast-erecting systems. Increase of efficiency of the erection process of these systems can be implemented on the basis of the results of a multiple-criteria analysis of the organizational and technological processes by decomposing it into separate technological processes and operations and assessing their impact on the overall building erection process. The structure of a multiple-criteria model includes such indexes as the duration of separate technological processes and the operation of the overground part in the building erection. The subject of the study – technological operation parameters during the installation process of the transformable low-rise buildings with sandwich panel walls. Based on selection, classification, and systematization of the factors determining the resultant indicators, the relationship between the effective indicator (function) and the factors (arguments) was studied and their forms of dependence were determined based on the linkage modeling. The calculation of the influence of various factors and their assessment on the change in value of the effective indicator was performed. The selected factors include several parameters in the form of technological operations, which are expressed in hours. The simulation of technological process using a multiple-criteria model allows determining the efficiency reserves of the developed technology. Its application in installation control processes could help the construction industry with transformable low-rise building erection.