Tomáš Brestovič

Numerical simulation and experimental analysis of acoustic wave influences on brake mean effective pressure in thrust–ejector inlet pipe of combustion engine

This paper is focused on a numerical simulation and experimental analysis of acoustic wave influences on brake mean effective pressure in a thrust–ejector inlet pipe of a piston combustion engine. The experiment is based on a real racing motorbike, which is driven by a piston combustion engine, equipped with a newly developed and patented thrust–ejector inlet pipe. This new inlet pipe is able to eliminate problems concerning an insufficient charging of cylinder with a fresh mixture. The engine sucks the air by overpressure, which is directly related to increased performance and torque. The first part of this paper presents the analytical relations describing acoustic waves in an inlet pipe. The next part contains a numerical simulation performed by software Ansys CFX in order to obtain a detailed description of flowing air, which passes through the ejector into the air box. The experimental measurements were realised using the data–recording system EW&C.

THE EFFECT OF TEMPERATURE PYROLYSIS PROCESS OF USED TIRES ON THE QUALITY OF OUTPUT PRODUCTS

Abstract Pyrolysis together with gasification and combustion create a group of so called thermic processes. Unlike the combustion it is based on thermic decomposition of organic materials without any access of oxidative media. Within the pyrolytic process, three main fractions are created: solid residue, pyrolytic gas and organic liquid product - pyrolytic oil. The presented article examines the effects of pyrolysis operational conditions (above all, temperature) on gas products, solid residues and liquid fractions.

SOFTWARE SUPPORT DEVELOPMENT FOR NUMERICAL SOLUTION OF ANSYS CFX

Abstract The paper deals with possibilities to apply a new developed software support for simulation programme ANSYS CFX. A direct export of heat-transfer coefficients into variables used under edge conditions as well as of physical properties of gas mixtures into material properties during simulation solution of technical tasks means a significant saving of time. The paper summarizes in detail description of the software for calculation of heat-transfer coefficient during free convection (HTC-FC) and of material properties of gas mixture (MPGM) that enable to export calculated data directly into the text files which can be imported then into the programme ANSYS CFX.

Determination of Boundary Conditions and Optimalisation of the Graphite Electrode Cooling Circuit

The present paper describes the determination of boundary conditions of the 10 kVA plasma reactor graphite electrode cooling. The water cooler installed on the lid of the reactor, connected in open circuit, sustains the permissible service temperatures in the analysed area of the reactor. With the monitoring of the coolant flow and temperatures at the inlet and outlet of the cooler, the heat flux necessary for the design of a closed circulation cooling circuit was determined. Software support of HTC-FC (heat transfer coefficient – natural convection) and simulation software ANSYS CFX were used to solve the design and functionality of the proposed solution. This software is designed for the numerical calculation of differential equations describing fluid flow and heat conduction with the use of the finite volume method. With the application of time-dependent boundary conditions in the simulation tool ANSYS CFX, we acquired information about the temperature distribution of the cooling medium during the operation of the described technology and also about the change in the variation of heat flux between the environment and the proposed container.

SIMULATION OF HEAT TRANSPORT AT THE COOLING OF THE SUGAR SOLUTION IN A RECUPERATION EXCHANGER

The paper describes a mathematical model of the cooling process of a highly concentrated sugar solution in an exchanger with a specifically shaped heat exchanging surface of the cooling panels. An analysis of the individual parts of the stum cooling line is made, dealing with the cooling performance of the cooling panels located in the stum tanks, whose volume is 3230 litres or 1430 litres. One of the monitored parameters is the cooling performance of the JN30 aggregate. The article also deals with an appropriateness of the aggregate for cooling the stum of the total volume 78.21 m 3 , from the real operation temperature to 0 °C during 48 hours.

APPLICATION OF ANALYTICAL SOLUTION FOR EXTENDED SURFACES ON CURVED AND SQUARED RIBS

Abstract The presented article discusses how to increase heat transfer through ribbed surfaces and it is oriented to the mathematical representation of temperature fields and the total thermal flow. The complexity of solving for some types of ribs with variable cross-section requires the application of numerical methods, which are applied consequently to the planar rib as well. In this case there was chosen the finite- difference method (FDM). During solution of the cylindrical ribs the FDM method is preferably used directly with regard to the complexity of solving for infinite sums and improper integrals in Bessel functions. In conclusion is assessed the application suitability of the calculation procedure applied to curved ribs. This procedure is usually used to planar ribs. At the same time it is pointed out the possibility of using this method for calculation of the total thermal flow through cylindrical ribs, which have got the squared form.

Risk Related to the Application of Hydrogen Propulsion Technology in Cars

The introduction of hydrogen technologies in the automotive and energy industry requires research in all areas of its possible application including production of hydrogen, through its operation. All of these stages are burdened by the risk caused by interaction of hydrogen with the environment and technological subject. Security group risks represent significant risk of handling hydrogen due to the possibility of explosion. Based on the risk value, the safety level of the individual subsystems of hydrogen production and utilization process is subsequently assessed. Consequently, it is possible to assess the overall safety of the mobile system based on the final/resulting value of the risk. In case of improper handling, technical failure/incident or unexpected adverse event, there is a risk of hydrogen leak into the environment. With the wide range of explosive capacity of hydrogen-air mixture, it can represent a high risk of explosion with a relatively little energy initialization.

Measurement of Hydrogen Storage Capacity in Ca72Mg28 Alloy

This article discusses the measurement of hydrogen storage capacity in Ca72Mg28 alloy that has been produced by melt spinning. The alloy has an amorphous structure in which there is an assumption of hydrogen storage of acceptable concentration. The research is to analyse the possibility of desorption of the gas without recrystallization of the alloy. Subsequently, the problem of reversible hydrogen storage is examined at temperatures between 410–450 °C in the pressure range 0 to 3.5 MPa. This paper deals with the indirect determination of the amount of heat generated in the absorption of hydrogen by using the calorimetric method. In the conclusion there is a comparison of the storage capacity of hydrogen in the amorphous and crystalline structure of the alloy.

Model of heat losses from underground heat distribution system

The paper describes the linear density of the heat flow using dimensional analysis in the case of underground, pre-insulated piping. The methodology makes it possible to determine the heat loss based on a simple criterial relationship. Heat losses in the piping system were also calculated using numerical simulation. The difference between the experimentally detected losses and the values obtained from the model is −3.6% to 6.4%. The results of the numerical simulation at an ambient temperature of 25°C differ from the experiment by −1.7%. At an ambient temperature of −10°C the difference is −4.0%.The paper describes the linear density of the heat flow using dimensional analysis in the case of underground, pre-insulated piping. The methodology makes it possible to determine the heat loss based on a simple criterial relationship. Heat losses in the piping system were also calculated using numerical simulation. The difference between the experimentally detected losses and the values obtained from the model is −3.6% to 6.4%. The results of the numerical simulation at an ambient temperature of 25°C differ from the experiment by −1.7%. At an ambient temperature of −10°C the difference is −4.0%.

Simulation of Temperature Fields in the Transport Container

This article discusses the distribution of temperature in a transport container for spent nuclear fuel due to the generation of residual heat. ANSYS CFX simulation software was used to determine the temperature fields. The container is constructed of thick-walled carbon steel. Fins were provided on the outer casing of the container for better heat dissipation. Numerical simulations of temperature fields will be performed on the transport container with C-30 type designation. A container with a flow of water and nitrogen within the casket was considered during the performance of numerical simulation. The results of numerical simulations define the distribution of temperature fields, subject to adhering to storage conditions which prevent surface temperatures exceeding permissible values.