## Numerical simulation of heat transfer and hydrodynamics under transverse flow of compact bundles of tubes in shell-and-tube heat exchangers

Mathematical Modeling, Vol. 7 (2023), Issue 1, pg(s) 27-29

By using the application package ANSYS Fluent, the numerical simulation of heat and mass transfer processes in the channels of shell-and-tube heat exchanger with compact placement of tube bundles has been carried out. The fields of velocities, temperatures and pressures in the heat exchanger channel were obtained and the conditions of hydrodynamic flow in the channels and the processes of heat transfer in these channels were analyzed. A new construction of shell-and-tube heat exchanger with compact arrangement of tubes in tube bundles is proposed and developed.

## Optimization of the rubber forming process for the sheet metal part using numerical simulation

Mathematical Modeling, Vol. 6 (2022), Issue 2, pg(s) 51-54

This article focuses on the optimization of manufacturability for the aluminium cover produced by rubber forming. Aluminium Al6016 was considered as a material for the cover and its constitutive equations Hill 48 and Hollomon described its properties. The Mooney-Rivlin hyperelastic material model defined material properties for a punch made of rubber. Pam stamp software was used to create the simulation model and evaluation. Results were optimized from the view of thickness reduction and punch stroke when two different rubber hardness were selected.

## Numerical simulation prediction and validation two dimensional model weld pipe

Machines. Technologies. Materials., Vol. 13 (2019), Issue 10, pg(s) 447-450

This paper deals with Numerical Simulation to analyse the behaviour of residual stresses in welding pipe. This work aims to develop a validation model for the simulation of phase changing after welding in multi-pass welds using a hardness test and compare the results with numerical simulation. The simulation considers the local microstructure properties changes due to the thermal welding cycles. Finally, the challenge of this work is the welding of dissimilar materials, where a calibrated model will be applied and validated to predict the effect of welding residual stresses in welding pipe. A further aim is to develop a new procedure to simulate a typical welded pipe process.

• ## Numerical analysis of in-cylinder pressure and temperature change for naturally aspirated and upgraded gasoline engine

Trans Motauto World, Vol. 4 (2019), Issue 2, pg(s) 83-86

The paper presents numerical analysis of in-cylinder pressure and temperature change for naturally aspirated gasoline engine and two of its upgrades – upgrade with turbocharger only and upgrade with turbocharger along with air cooler. Numerical analysis was performed with 0D (zero-dimensional) numerical model. In-cylinder temperatures, for each engine rotational speed, are the highest for engine upgraded only with the turbocharger. The highest observed in-cylinder temperature of turbocharged engine was obtained at 5000 rpm and amounts 2542.4 °C. In-cylinder pressures are the highest for engine upgraded with turbocharger and air cooler for all rotational speeds except the highest one. The highest observed in-cylinder pressure of a turbocharged engine with air cooler was obtained at 5000 rpm and amounts 129.7 bars. Presented analysis showed that the selected air cooler can be improved at highest engine rotational speed.

• ## Material model parameters identification of blast environment

Security & Future, Vol. 2 (2018), Issue 3, pg(s) 142-145

In terms of designing or building new protective and security structures or equipment as a physical component of force protection, experimental verification of analytical or numerical calculations and vice versa becomes necessary. While the experiment can be performed on individual components, complex assessment of more complex variants or performing a parametric study is becoming more and more relevant in modelling and simulation domain. For this reason, there is a clear necessity to find the right connection between numerical simulation and experiment.
Fast, nonlinear processes require nonlinear material models to capture the rate of deformation and material behaviour under extreme loads such as the effect of explosions or the impact of a projectile, i.e. the effects, which the theories and practices of protection of the population and troops are trying to minimize. The important part of the accuracy of computational models is the correct identification of the parameters of material models used in the simulations.
This paper deals with the simulation of explosion and its effects and identification and optimization of material parameters of the environment in which the explosion and the shockwave propagates, with a focus on the soil material model. The inverse identification method is based on a combination of the experimental measurement data and the computational methods implemented in the finite element solvers and optimization programs. The simulation proceed from experimental measurement curves of blast effects. For measured parameter in the air overpressure at specific measuring points was chosen, while ground-propagating shock wave was evaluated by measuring
acceleration values. The numerical simulation took place in the LS-Dyna software environment interconnected with the Optislang optimization program.

## NATURALLY ASPIRATED GASOLINE ENGINE UPGRADE WITH TURBOCHARGER – NUMERICAL INVESTIGATION OF CHANGE IN OPERATING PARAMETERS

Machines. Technologies. Materials., Vol. 12 (2018), Issue 5, pg(s) 204-207

Numerical investigation of naturally aspirated gasoline engine main operating parameters and engine upgrade with a turbocharger is presented in this paper. Analysis is performed by using numerical 0D (zero-dimensional) simulation model. Turbocharging process with a selected turbocharger increases engine maximum torque for 62.58 % and also increases maximum engine effective power for 58.82 %. One of the main reasons of turbocharging process usage is reduction of engine brake specific fuel consumption. The highest decrease in brake specific fuel consumption for a turbocharged engine, in comparison with naturally aspirated one, is obtained at 4000 rpm and amounts 8.83 g/kWh (from 239.01 g/kWh for naturally aspirated engine to 230.18 g/kWh for a turbocharged engine). Turbocharging process brings several useful benefits to the analyzed gasoline engine, which is also a valid conclusion for internal combustion engines in general.

## THE INFLUENCE OF THE TOOTH PROFILE SHAPE ON THE STRESS-STRAIN STATE IN THE GEAR

Machines. Technologies. Materials., Vol. 12 (2018), Issue 4, pg(s) 153-156

The shape of the tooth profile affects the stress-strain state in the gear. In the case of a fatigue failure the stress state is a decisive criterion for the lifetime of the gear. The shape of the tooth flank affects the magnitude of the contact pressure in the contact of the meshing teeth. The consequence of which are surface cracks and pitting. The shape of the tooth root influences the magnitude of the root stress, which, when limit is exceeded, leads to root cracks and teeth breakage. Many different types of gearing are known, but in the practice most widely used is the involute one. Other types of gearing become interesting especially when polymer materials are being used. If the gears are injection molded the type of gearing does not affect the cost of the tool. In the case of metal gears, standardized tools for involute gearing make the use of other special types of gearing economically unjustified. Our research is focused on the S-gears, which got their name from the S-shaped path of contact. The paper presents the research of how the defining parameters of S-gears impact the stress-strain state in the gear. This was done using a numerical model which simulates gear meshing. The stress state of two different types of S-gears was compared with the stress state in an involute gear of the same dimensions (same module, number of teeth and width). It was found that with a proper choice of gearing type we can improve the load bearing capability of the gear pair. With use of our numerical model we have also analyzed the impact of the tip relief on the stress state. The numerical model was validated for the case of meshing steel involute gears, where we can compare the results of the model with the results according the ISO 6336 calculation. A good match between the results of the model and results according the standard was obtained. After validation the same numerical model was used for the calculation of the stress-strain state in S-gears. This was calculated then for metal and polymer (POM/PA) gear pairs.

## NUMERICAL MODEL FOR SIMULATION OF THE VELOCITY FIELDS FOR THE EXPLOSIVELY FORMED PENETRATOR

Mathematical Modeling, Vol. 1 (2017), Issue 4, pg(s) 199-202

The current paper presents numerical approach of velocity performances estimations for the EFP (Explosively Formed Projectiles). The proposed method mathematically develops velocities parameters of a particular segment for EFP liner propelled by explosive process. The numerical method is developed, to provide estimations about behavior of projectile vs. time in the EFP forming process powered by explosion. The model is valid for performances estimations of EFP warheads and design data for optimal EFP configuration. Simulations are supported by the software Autodyn for numerical modeling respectively. The obtained numerical results are compared with the available experimental data.

## SIMULATION AND SOFTWARE DEVELOPMENT FOR SOLVING INTERNAL BALLISTICS PROBLEMS

Science. Business. Society., Vol. 2 (2017), Issue 3, pg(s) 111-114

The problem of internal ballistics is considered, including basic pyrodynamic equation, law charge combustion, gasification law and equations of the projectile motion. A numerical method is used to solve a system of three algebraic and three ordinary differential equations. The software was developed and a number of computational experiments were made to analyze the influence of the charging parameter on the processes occurring during the projectile movement in the barrel channel. The problem of gunpowder burning and a finite-difference method to solve it are considered. The results of this work can be applied to the design of new types of trunks and charges.

## ENERGY ANALISYS AND WASTE HEAT RECOVERY POTENTIAL OF AN AUTOMOTIVE DIRECT INJECTION DIESEL ENGINE

Machines. Technologies. Materials., Vol. 11 (2017), Issue 7, pg(s) 332-335

The article presents a numerical analysis of energy balance of an automotive diesel engine and exergy analysis of exhaust gas and cooling systems. A model of the engine was built in advanced simulation code AVL Boost. In order to validate the model a comparison between estimated and real engine effective power was conducted at full load. Energy balance revealed a maximum engine efficiency of 42.1% at full load and 2000rpm. The highest quantity of lost energy contains the exhaust gas. The maximum estimated exhaust gas enthalpy is 108kW at 4000rpm. At the same operating point the cooling enthalpy more than twice lower – 40.2kW. At the engine speed lower than 2000rpm the lost energy in exhaust gas and cooling system has the same quantity. The exergy analysis revealed that waste heat recovery potential in exhaust gas is much higher than cooling system. The results obtained in this study will be further used in a Rankine-Hirn waste heat recovery system development due to increase overall engine efficiency.

## APPLYING A MODIFIED VARIATIONAL ITERATION METHOD TO THE PLUNGE GALLOPING EQUATION

Machines. Technologies. Materials., Vol. 11 (2017), Issue 6, pg(s) 311-314

The plunge galloping is a high-amplitude, low-frequency oscillation of a slender structure, such as iced conductors of a power transmission line or bridge decks, essentially perpendicular to the wind direction. In the paper, an idealized model for the plunge galloping is shortly reviewed and then a slight modification of the variational iteration method, applicable to weakly nonlinear problems, is employed to obtain a system of two amplitude-frequency equations that provide both the transitional and long-term behaviours. The approximate analytical results derived in the paper have been applied to a typical section model and the numerical results are contrasted with those provided by the direct integration of equation of motion.

## HAMILTONIAN – BASED TECHNIQUES FOR SOLVING PENDULUM – LIKE NONLINEAR OSCILLATORS

Machines. Technologies. Materials., Vol. 11 (2017), Issue 5, pg(s) 225-228

In the paper, HE’s energy balance method and HE’s Hamiltonian approach are used to derive simple approximate formulas for the dependence of the frequency of a pendulum-like nonlinear oscillator on its amplitude. Such kind of oscillators are frequently encountered in many fields of engineering and three examples from mechanical domain are given and utilized in the numerical simulations. By comparison with the exact solution, it is shown that obtained formulas lead to high accuracy for initial amplitudes lower than 900 (when the relative errors do not exceed 0.2%) and acceptable closeness for amplitudes well beyond the small-angle regime (here the relative errors are about 5-6% for amplitudes as high as 1500). Results furnished by energy balance method and Hamiltonian approach are contrasted with those provided by other techniques which generally need much more sophisticated procedures