Thermal and performance analysis of a gasification boiler and its energy efficiency optimization

The purpose of this study was to determine a method for multi-parametric output regulation of a gasification boiler especially designed for heating or for hot water heating in buildings. A new method of regulation is offered, namely more parametric regulation via proportional-integral-derivative (PID) controllers that are capable of controlling the calculated values of pressure, temperature and fan speed. These values of pressure, temperature and fan speed are calculated in a completely new way, and calculations of setpoints for determination of optimal parameters lead to an increase in boilers efficiency and power output. Results of measurements show that changes at the mouth of the stack draft due atmospheric influences occur in times with high intensity and high frequency, while power parameters, or boiler power output amplitudes and fan speed automatically "copy" those changes proportionally due to instantaneous fan speed changes. The proposed method of regulation of the gasification boiler power output according to the technical solution enables a simple, cheap, express and continuous maintenance of high power output at low concentrations of the exhaust gases of the gasification boilers from the viewpoint of the boiler user, as well as from the perspective of development and production it allows a continuous control monitoring of these parameters.Web of Science107art. no. 106

Usporedba utjecaja različitih tehnologija rezanja materijala na kvalitetu reza konstrukcijskih čelika

The paper deals with a comparison of the most frequently used thermal cutting technologies applied to the structural, low carbon steel EN S355J0 in engineering enterprises with a focus on experimental measurement and evaluation of characteristics of the heat affected zone. It gives a mutual comparison of these technologies in terms of the achieved heat affected zone. The goal of this paper was to use the property changes in the used material (affected by laser, plasma arc and oxygen cutting) as the quality indicator of the cutting process.U radu se daje usporedba najčešće korištenih toplinskih postupaka rezanja, koje koriste proizvodne tvrtke, u primijeni na konstrukcijskom, nisko ugljičnom čeliku EN S355J0 s naglaskom na eksperimentalna mjerenja i vrednovanje svojstava zone utjecaja topline. Rad prikazuje usporedbu tih tehnologija u kontekstu dobivene zone utjecaja topline. Cilj ovog rada je korištenje spoznaje o promjenama svojstava korištenog materijala na površini reza (dobivene laserom, plazmom i plinskim rezanjem) kao pokazatelja kvalitete procesa rezanja

Statistical evaluation of impact of technological factors on surface texture of WPC composites

The paper aims at evaluating the impact of technological parameters of a drilling process on the parameter of surface roughness Rz (maximum height of roughness profile) of wood-based material (WPC – Wood Plastic Composite). During drilling with tools 3.0, 5.0 and 7.0 mm in diameter, the spindle speed nc and feed rate f were changed. The evaluation of statistical significance was performed using the ANOVA mathematical tool (two-way with repetition). Using a simple conversion, it is possible to assess which of the set parameters affects the final surface quality, which serves as supporting information for the work of an engineer.Web of Science52332932

Physico-mechanical properties and electrical conductivity of conductive plastic materials

The paper deals with the research of variety of non-standard samples of plastic material made by injection moulding. The samples were made of conductive plastic material (LNP Stat-kon Compound ZX05009). Brown Corundum F24 was used for blasting under different pressures. This conductive plastic material can be applied as a plastic electrode, it is therefore possible to make measurements and examination of electrical conductivity. The experiment is used in order to establish the extent, to which the pressure used at blasting measurably affects the electrical conductivity of plastic electrode.Web of Science51215215

Measurement of physical properties of polyurethane plaster

Fizikalna svojstva građevnih materijala mogu se definirati pomoću koeficijenata materijala kao što su srednja gustoća, specifični toplinski kapacitet, toplinska provodljivost i toplinska difuzivnost. U radu je prikazano ispitivanje fizikalnih svojstava novorazvijenog materijala (poliuretanske žbuke) nerazornim postupkom. Također je provedeno određivanja svojstava komparativnih uzoraka izrađenih od porobetona pri čemu je primijenjena ista metoda kao i isti uvjeti ispitivanja. Za određivanje toplinske provodljivosti i specifičnog toplinskog kapaciteta razvijena je i verificirana nova komparativna metoda za čije je provođenje razvijen novi kalorimetrijski uređaj.Physical properties of building materials can be defined by material coefficients. The material coefficients examined were: coefficient of mean density, coefficient of specific heat capacity, coefficient of thermal conductivity, and coefficient of thermal diffusivity. Physical properties of a newly-developed material (polyurethane plaster), were subjected to non-destructive analysis. The same method and same conditions of measurement were applied to measure the properties of comparative samples made of Ytong. In order to measure the coefficient of thermal conductivity and coefficient of thermal capacity, a new comparative method was designed and verified and also a new calorimetric apparatus was used

Proposition of a solution for the setting of the abrasive waterjet cutting technology

The submitted paper aims to clarify the abrasive waterjet technology, particularly from the point of view of produced surface topography. It provides a new insight into the deformation process caused by the effect of abrasive waterjet and into the possibilities of using the surface topography for solving the issues of optimization of the process. The subject of study is a system of cutting tool, material and final surface topography and optimization of their parameters. The cutting or disintegrating tool of abrasive waterjet technology is flexible. The trajectory of its cut traces is strictly determined here by disintegration resistance at critical moments of tool-material interaction. The physico-mechanical character of the interaction within the cut will manifest itself in the final surface condition. This process can be re-analysed by measuring the selected elements of topography and roughness on the final surface, namely depending on the depth of the cut, technological parameters of the tool and mechanical parameters of the material. The mentioned principle is the basis of the presented solution. It lies in the analytical processing and description of correlation interrelations between set technological and measured topographical quantities in relation to the depth of cut and the type of material.Web of Science13528527

ANSYS analysis of stress and strain after cones plastic deformation

The paper deals with study of stress and strain after cones plastic deformation by ANSYS software. There are shown the new results of FEM analysis, what is the base for the further experimental studies.Web of Science22250850

Method of maintaining the required values of surface roughness and prediction of technological conditions for cold sheet rolling

The paper is based on results obtained from topography of surfaces of sheets rolled from deep-drawing steel of the type KOHAL grade 697, non-alloy low-carbon structural steel EN 10263-2:2004 and aluminium. The presented results document correctness of the assumption that the rolling force Froll increases with the increasing reduction Δh and the quality of the rolled surface is improved at the simultaneous increasing of strength of rolled sheets and the decreasing of size of structural grains. The experiment was performed on the two-high rolling stand DUO 210 SVa, which enables only non-continuous technology in contrast to the rolling mill with continuous reduction on one sheet in several degrees on rolling trains, in consequence of which the obtained height parameters of the section are in close correlation with the predicted dependence. Contribution of the work consists in the creation of a mathematical model (algorithm) for predicting technological parameters of the two-high rolling stand DUO 210 SVa at change of the absolute reduction Δh, for example for a deep-drawing steel of the type KOHAL grade 697 and non-alloy lowcarbon structural steel PN EN 10263-2:2004 and aluminium, and also in the development of a method of calculation applicable to any material being rolled in general, because the authors have found that various materials can be differentiated by a derived analytical criterion IKP. This criterion is a function of ratio between the modulus of elasticity of reference material and that of actually rolled material. The reference material is here deep-drawing steel of the type KOHAL grade 697. Verification was carried out by measuring changes of final surface roughness profile and final strength of rolled sheets of the stated materials in relation to reductions and those were compared with theoretically predicted values. It is possible to identify and predict on the basis of this algorithm an instant state of surface topography in respect to variable technological conditions. On this basis it is then possible to calculate and plot individual main technological parameters.Web of Science14315114

Proposal for the identification of residual stresses after turning and hardening of bearing steel

Residual stresses are defined as the stresses that occur in the material without the application of an external load. Their occurrence is related to the technology of production and treatment of the material. This article proposes the identification of residual stresses in a steel material for bearing production, specifically 100Cr6 (1.3505) material. The identification consists in measuring the material by X-ray diffraction method, for which the Proto iXRD mobile diffractometer was chosen. The first measurement was carried out on turned bearing rings and a subsequent second measurement was carried out on the same rings after heat treatment, namely quenching and tempering. This article also proposes a measurement methodology for the bearing rings, where each ring is measured in 6 positions rotated 60° with respect to each other. The measurement results are compared with the individual manufacturing operations, i.e. turning and heat treatment. The results clearly show the expected increase in residual stresses after turning and subsequent decrease after heat treatment. The technological parameters of turning fundamentally influence the residual stresses and thus also affect the quality of the product in subsequent production operations

Artificial neural networks application in modal analysis of tires

The paper deals with the application of artificial neural networks (ANN) to tires’ own frequency (OF) prediction depending on a tire construction. Experimental data of OF were obtained by electronic speckle pattern interferometry (ESPI). A very good conformity of both experimental and predicted data sets is presented here. The presented ANN method applied to ESPI experimental data can effectively help designers to optimize dimensions of tires from the point of view of their noise.Web of Science13527827