Wyniki wyszukiwania - Biblioteka Nauki

1

Possibilities for the Application of Numerical Modelling to the Optimization of Combustion Processes and Gas Dynamics in Heating Furnaces

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Poskart M. , Nowak K. , Szecówka L. , Radomiak H.

Archivum Combustionis

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2008

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tom Vol. 28 nr 1-2

95-103

EN

The progressing development of industry and the associated increasing environmental pollution create the need for the intensification of combustion processes and the implementation of increasingly stringent environmental protection standards. Therefore, an intensive progress in scientific and research work is observed, and studies with the use of numerical methods are becoming an indispensable element of experimental research, enabling the optimization of combustion processes with the simultaneous evaluation of ecologic effects and, as a result, the development of new designs of burners and special, low-emission combustion technologies. This article presents possibilities for the numerical modelling of combustion processes and gas dynamics in heating furnaces. The chemistry of the combustion process was modelled using the software CHEMKIN version 4.02, while the gas dynamics of flue gas flow in the combustion chamber was modelled with the program FLUENT. Numerical computations were performed for both the experimental chamber and real facilities, namely a pusher furnace and a sheet hardening furnace.

2

Combustion of Biofuels Based on Sludge and Coal

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Kolat P. , Cech B. , Kadlec Z. , Raclavska H.

Archivum Combustionis

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2008

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tom Vol. 28 nr 1-2

85-94

EN

The article discuss the questions of thermal utilisation of mechanically drained stabilized sludge from the waste water treatment plants in the boiler with circulated fluid layer. The paper describes the thermal analysis of coal, sewage sludge and its mixtures, mud transport to the fluid bed boiler, effects on boiler efficiency, operational reliability of the combustion equipment, emissions and solid combustion residues.

3

Investigation of the Combustion of Calcium Siliide/polytetrafluoroethylene Mixtures

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Trzciński W. A. , Cudziło S. , Szala M. , Gut Z.

Archivum Combustionis

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2007

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tom Vol. 27 nr 3-4

69-79

EN

An attempt has been made to visualise the process of the growth of SiC nanofibres after the combustion of CaSi2/PTFE mixtures, using a CCD camera working in the a schlieren mode. Moreover, overpressure histories, mass of solid combustion products and heat of combustion were measured in a closed reactor and compared with the results of thermochemicaI calculations. The mechanism of the formation of SiC nanofibres is discussed.

4

The Effect of Combustion Energy Recuperation in an Annular Double-layer Catalytic Converter

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Budzianowski W. M. , Miller R.

Archivum Combustionis

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2007

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tom Vol. 27 nr 3-4

123-134

EN

The following contribution deals with catalytic combustion of lean gaseous fuels in an annular double-layer catalytic micro-converter with integrated exhaust energy recuperation. With the proposed design industrially preferred auto-thermal operation was attained for 112 ppmv propane content in adiabatic conditions with inlet temperature of 300 K. The miniaturized recuperative converter exhibited bifurcational changes for very low combustible content with extinction fold located below Tin = 300 K. The increase in fuel concentration enabled compensation of external cooling to certain level. For well insulated modular set of converters internal converter may be treated as adiabatic and external converters non-adiabaticity should be compensated by an additional increase in fuel concentration. For a given converter and fuel a strict range of gas velocities (or GHSV) should be specified. The low value of gas velocity was the key parameter in efficient heat recuperation. The high value of gas velocity led to higher combustion energy release. With too low value of gas velocity combustion energy release was too small with relation to wall heat conduction so as appropriate axial temperature gradient might not develop and higher temperature in the catalytic section of the converter was not attained leading to extinction. With too high value of gas velocity heat recuperation efficiency was too low and extinction was exhibited. To attain higher value of GHSV a more efficient recuperator should be applied, which may be attained with listed heat transfer enhancement techniques.

5

Gravimetric investigations of PM oxidation kinetics on catalytic coated silicon carbide bases

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Nagórski Z. , Makowski J.

Archivum Combustionis

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2011

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tom Vol. 31 nr 4

197-209

EN

The article contains analysis of kinetics of PM oxidation conducted on ceramic SiC bases with oxidizing catalytic layer. Tests were conducted on specially designed and developed prototype stand that enables to conduct experiments in environment similar to conditions in diesel engine exhaust system. Test were conducted in various process parameters: oxidizer temperature, oxygen fraction in the oxidizer and rate of the volumetric flow of oxidizer. A series of experiments were conducted to determine influence of test parameters on the oxidation process. From those experiments temperature characteristic of basic PM oxidation kinetic parameters such as activation energy and oxidation constant were determined.

6

Influence of breakup models on simulation results of mixture formation and combustion in direct injection spark ignition engine

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Jaworski P. , Ćwikowski P. , Teodorczyk A.

Archivum Combustionis

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2011

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tom Vol. 31 nr 1-2

43-54

EN

Nowadays the wide range of spark ignition (SI) engines with spray guided direct injection (SGDI) are in production. Spray development is playing a major role in advanced engine design with three-dimensional computational fluid dynamics (CFD). Nevertheless, there is still a need for improvement in CFD injection simulations because of high pressure injection. The high pressure influences the drop breakup, coalescence and evaporation, which are crucial for proper representation of simulated phenomenon. Computer codes, like FIRE, give a possibility to simulate the process of injection with various types of breakup models. In spite of the importance of atomization, the mechanisms of breakup are still not well understood. To obtain better understanding of breakup model s influence on combustion the simulations have been performed for the engine combustion chamber with inlet and outlet system and SGDI strategy. ECFM-3Z combustion model was used for ethanol fuel. Demonstration of the influence of different breakup regimes on the combustion processes is presented. Comparison was made for Wave, Tab (Taylor Analogy Breakup) and Reitz breakup models.

7

Comparison of standard k-ε and RNG k-ε models in flows in 2d model of HCCI engine cylinder

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Ahmadi P. , Wyszynski M.

Archivum Combustionis

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2011

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tom Vol. 31 nr 1-2

79-96

EN

A computational study of flows in 2D model of four-stroke homogenous charge compression ignition (HCCI) engine cylinder was conducted by standard k-? and renormalization group (RNG) k-? models in FLUENTŽ release 6.2. The primary objective was to evaluate the aforementioned turbulence models for simulation of in-cylinder flows. The engine model was a 2D geometry of a cross section of piston-cylinder assembly, passing through the centres of intake and exhaust valves and parallel to the cylinder axis. Simulation was performed for five consecutive engine cycles under cold-flow assumption and with air as the working fluid. It is generally believed that standard k-? model over-predicts the turbulence kinetic energy, k. The results obtained from the fifth engine cycle at bottom dead centre (BDC) of the intake stroke revealed that below the intake valve and in the near-wall region, standard model estimates up to 26% higher values of k. Overestimation of k by the standard model, results in prediction of higher and less accurate values of turbulent viscosity, ? by this model. Subsequently, in-cylinder flows exhibit large rates of flow deformation, and by definition, RNG model predicts more accurate values of ? in rapidly strained flows. Below the intake valve, ? is predicted up to 53% lower by the RNG model. Therefore, RNG model, in comparison to standard model, is a better approach for computational investigation of in-cylinder flows.

8

Two-dimensional analysis of hydrogen/oxygen cylindrical detonation using AUSMDV scheme

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Asahara M. , Tsuboi N. , Hayashi A. K. , Yamada E.

Archivum Combustionis

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2011

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tom Vol. 31 nr 3

177-186

EN

Many researchers have simulated detonation using a Harten-Yee upwind TVD scheme. Such scheme has a strong numerical diffusivity around calculating a discontinuity surface as shock wave. However, the numerical result of discontinuity surface using the Harten-Yee upwind TVD scheme is diffusive. To avoid this diffusivity, an AUSMDV scheme is used instead of the Harten-Yee upwind TVD scheme. As the results, we obtained a sharp cellular structure of cylindrical detonation in the maximum pressure histories like open-shutter photograph and smoked-foil record which are obtained experimentally. However, the irregular cells were observed because grid resolution was not enough for cylindrical detonation. In the future work, the grid density must be kept constant for each direction of shock propagation.

9

Analysis of possibility of fluent code application for simulation of combustion process in piston engines

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Gieras M. , Jasiński D.

Archivum Combustionis

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2011

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tom Vol. 31 nr 1-2

29-42

EN

The objective of the study was to carry out an analysis of Fluent numerical code in context of piston engine simulations. The work contains a survey of options and models of Fluent 12.1, that were created for modelling piston engines. The work also includes an analysis of combustion models that may be used for representation of processes in internal combustion engines. Verification of the numerical models was conducted for the engine of a Polonez 1500 car. The verification consists of geometry representation, numerical model preparation, comparison of results to the actual engine performance and a discussion of results.

10

A.K. Oppenheim contribution to combustion research in Poland

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Wolański P.

Archivum Combustionis

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2011

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tom Vol. 31 nr 3

159-166

EN

Contribution of A.K. Oppenheim to combustion research in Poland is summarized. Most of his activities were basically devoted to two subjects of improvement of combustion in Internal Combustion (IC) engines such as: Pulsed Jest Combustion (PJC) and to Controlled Combustion Engines (CCE). Additionally he strongly promoted research on explosive combustion in confined enclosures as well as detonation research. A short summary of this activities is given in the paper.

11

Transition to detonation after a 'Volume Explosion' Oppenheim's experiment validation with a numerical calculation

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Dzieminska E. , Fukuda M. , Hayashi A. K. , Tsuboi N.

Archivum Combustionis

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2011

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tom Vol. 31 nr 3

187-195

EN

Over many years of research Oppenheim's group performed a lot of experimental work concerning detonation. According to his notes the birth of detonation starts as a smooth-surfaced and spheric ally propagating flame which front wrinkles and accelerates. In a short time it produces compression waves that coalesce into a precursor shock which travels with some distance from the flame. Its structure eventually changes to a turbulent flame, while the surface creates so called 'tulip-shape' form. This phenomenon is associated with pressure waves' generation, which becomes slightly more intense in time as the flame becomes highly turbulent. They merge and form shock fronts. This leads to an 'explosion in the explosion' (appearing in the region of the accelerating flame) [1,2], which would be the last stage of the detonation wave birth, just before deflagration-to-detonation transition (DDT). In the first stages of propagation the reflections of the explosion from the back wall help the flame acceleration but later they have no significant meaning.

12

Studies on process of dust explosion suppression by water spray

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Gieras M.

Archivum Combustionis

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2011

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tom Vol. 31 nr 1-2

63-77

EN

Processes of dusty flame quenching and its acceleration by water sprays were investigated. For better understanding of these problems the neutral sand particles and typical extinguishing powders were also used. The study was carried out in the 1.25 m3 explosion chamber. A corn starch-air mixture was used in the explosion processes. It was shown that action of the water spray with the smallest droplets on the dust explosion suppression was the most effective. Also simulations of flame suppression process by water sprays with using the computer code FLACS were made for better understanding of the mechanism of flame acceleration and quenching processes (during dust explosion) caused by water sprays. An idea of optimal water spray droplets extinguishing diameter has been discussed. The obtained results confirmed that the water spray can be more effective as a dust explosion suppression medium than typical extinguishing powders.

13

Analysis of gaseous pollutants generated during natural gas and waste material combustion process

100%

Wilk M. , Magdziarz A. , Zajemska M.

Archivum Combustionis

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2011

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tom Vol. 31 nr 4

245-254

EN

Taking into account the obligations of Poland under Treaty of Accession concerning waste management order, the most important problem is the waste recovery and waste disposal. Sewage sludge is wastes which can be include to the biomass-based materials. The waste storage should be limited, because of obligations of the municipal waste reduction. The increasing charges of waste storage and limited possibilities of waste disposal in agriculture (caused by heavy metals) are the factors, which suggest searching new technologies. One of waste disposal method is the thermal utilization. The thermal utilization is an energy production method as well as a chemical waste utilization. This paper presents the numerical modelling of the possibilities of using sewage sludge in the combustion processes. The computer simulation makes possible to analyse complex phenomena which are otherwise difficult to observe. The aim of this work was modelling the natural gas combustion process with sewage sludge used as reburning fuel to predict the amount of pollutants generated (NOx, CO, SO2) in the exhaust gases. The numerical calculations were done using the CHEMKIN program. Results of calculations were done taking into account the influence of temperature, pressure and residence time.

14

Influence of mineral matter on NO formation during air-staged combustion of pulverised lignite

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Zacharczuk W. , Hardy T.

Archivum Combustionis

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2011

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tom Vol. 31 nr 1-2

5-15

EN

The evolution of NO during air-staged combustion of pulverized lignite has been studied with an electrically-heated drop-tube reactor, in wide temperature and stoichiometric ratio range. In order to investigate the effect of mineral matter in lignite on NO formation, raw, demineralized and Ca-loaded lignite samples have been used. The obtained results showed that some active components in mineral matter promote NO reduction during air staging under certain combustion conditions. The maximum benefits of the catalysts presence were observed at low stoichiometric ratio region and combustion temperatures where the emission level of NO from raw lignite was apparently lower in comparison with HCl washed lignite. A similar effect has been also found for individual calcium catalyst introduced into demineralized lignite by impregnation.

15

AKO's some scientific thoughts and related work at AGU

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Hayashi A. K.

Archivum Combustionis

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2011

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tom Vol. 31 nr 3

139-157

EN

Professor Antoni K. Oppenheim's memory is presented through his notes, book, and papers together with jet ignition and fundamental study of pulse detonation engine at Aoyama Gakuin University (AGU). These works at AGU are strongly related with the work done by Prof. Oppenheim. Paper presented at A.K. Oppenheim Memorial Seminar, August 2-3,2009 Warsaw University of Technology

16

The study on the effect of selected parameters of coal on its mass loss during combustion in a two-phase flow of inert material

100%

Pełka P.

Archivum Combustionis

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2011

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tom Vol. 31 nr 1-2

97-109

EN

The inspiration behind this research is the attempt to explain the mechanism of the loss of the mass of coal particles during the process of their combustion in a circulating fluidized bed. The subject of research is related to various types of Polish bituminous and lignite coal. On the basis of research carried out up to now it is well known that the process of erosion plays a significant role in the process of burning coal by changing its mechanism, as well as generating additional loss of mass. The aim of this research is to define the impact of the basic parameters of coal, i.e.: volatile matter, fixed carbon, ash content, carbon content and additionally the Hardgrove grindability index on the erosive loss of mass of the burnt particles. The combustion process in a two-phase flow of inert material modelling the conditions of fast fluidization in the dilute upper zone of the combustion chamber has been carried out. Clear correlation of mass loss of the tested particles with chemical composition of coal especially with volatile matter and ash content have been observed. The impact of the Hardgrove grindability index on the process under analysis was not however noted.

17

Oppenheim's gasdynamic perspective of combustion and explosion phenomena

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Kuhl A. L.

Archivum Combustionis

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2011

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tom Vol. 31 nr 3

135-138

EN

Perhaps the most important contribution of Antoni Kasimierz Oppenheim (Tony) to science was his gasdynamic perspective that he brought to the analysis of combustion and explosion phenomena. This perspective started with his two Ph.D. theses of 1944: "Investigation of High-Speed Flow of Gases in Channels [1]" (University of London) and "Some Applications of the Theory of Flow to Internal Combustion Engines [2]" (Imperial College of Science and Technology). The former provided a gas dynamic formulation for one-dimensional compressible flow of ideal gases (based on Busemann's Hand-Buch der Experimentalphyik), while the latter applied this theoretical formulation to improve the efficiency of internal combustion engines. This two-pronged theme dominated his research for more than 60 years.

18

Dynamic Error Correction as a Method for Improvement of Correlation of the Rate of Heat Release Results Measured with Various Test Methods

100%

Sychta K.

Archivum Combustionis

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2010

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tom Vol. 30 nr 4

463-470

EN

The measurements of heat release intensity of material should be treated as dynamic process and measurement should be dynamic accordingly. To validate the method of correction of dynamic error of the value of heat release intensity as measured accordingly to the method described in the ISO 5660-1 the special experimental set-up was designed and made. Experimental test apparatus with the basic element consisting the computer programmed gas burner with the possibility of choice of various functions and kinds of burning parameters is mounted on various test apparatuses. The consideration of dynamic parameters of test apparatus used for measurement of heat release rate of materials resulted in the improvement of precision of test results (reproducibility and correlation) of data for heat release intensity obtained with the various standard test methods, with no necessity of changes to the construction of the test apparatus with the only minor changes to the testing procedure.

19

Emission results of combustion process of fatty acids distillation residue in an oil boiler - comparison to heavy fuel oil

80%

Wasielewski R. , Glod K.

Przegląd Naukowy. Inżynieria i Kształtowanie Środowiska

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2020

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tom 29

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nr 1[87]

20

An investigation of the presence of uncontrolled combustion phenomenon in spark ignition single cylinder optical engine

80%

Luszcz P. , Xu H. , Wyszynski M. , Tsolakis A. , Frąckowiak M.

Journal of KONES

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2006

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tom Vol. 13, No. 2

281-290

EN

The objective of this paper is to investigate appearance of surface ignition - postignition experienced inside the engine cylinder and correlate it with the nature of the spark ignition combustion prior to the onset of surface ignition. The test engine used to carry out all experiments was a Jaguar optical single-cylinder engine, operating in spark-ignition mode, although with negative valve overlap. The optical configuration of the engine allows characterizing and analyzing combustion process based on the processing of captured images in correlation with in-cylinder pressure and other parameters recorded with regard to instantaneous engine operating conditions. Results of the experiments covered in this publication focus on flame propagation and development as well as reveal occurrence of abnormal combustion processes. Experimental observations, especially the captured images show a relationship between the nature of normal combustion process initiated by spark discharge and the existence of abnormal combustion phenomena. All tests were performed under fixed engine conditions - constant speed and single component hydrocarbon fuel. Because the nature of fuel can shape the combustion process, a brief discussion and a proposed correlation of anti-knock, auto-ignition, and resistance to surface ignition qualities of a few single- and multi-component fuels is presented. Finally the publication leads to provide an indication of possible solutions concerning the problem of uncontrolled post-ignition events in optical engines.