Wyniki wyszukiwania - Biblioteka Nauki

1

Computational study of a combustion process in a turbine engine combustor

100%

Gieras M.

Archivum Combustionis

|

2013

|

tom Vol. 33 nr 1

11--26

EN

A computational study of the combustion process in a GTD-350 turbine engine combustor is presented. The numerical grid generation process and the optimization of its density are described. For the assumed boundary conditions, numerical simulations of fuel dispersing, mixing and combustion process in the combustor were performed with the use of Fluent code. The numerical simulations were conducted for different cone angles of spraying fuel and for different mean droplet diameters of fuel spray. The work ends with the discussion of results, in particular concerning the quality and stability of the combustion process in the engine combustor.

2

Computational study of the impact of chosen geometry parameters on stability of recirculation zone in GTD-350 gas turbine combustor

100%

Gieras M.

Archivum Combustionis

|

2014

|

tom Vol. 34 nr 2

101--116

EN

The aim of this paper is to evaluate the impact of modifications of selected geometric parameters on the formation of the main recirculation zone in the combustion chamber of GTD-350 turbine engine. Changes were evaluated based mainly on the swirl number as a non-dimensional criterion to characterize the amount of rotation imparted to the axial flow. Geometric modifications include the changes in the angle of swirler vanes, as well as the changes in the position of holes along an axis of the chamber and its diameter. Moreover, a special modification which would cause an additional angular momentum of air flowing through the hole inlets on the outer side of the combustor liner has been proposed. This modification will improve the mixing process in the primary zone and may reduce the temperature pulsation of exhaust gas. The study presents 3-D numerical simulations of aerodynamic flow inside a GTD-350 turbine engine combustion chamber. The process of generating a numerical grid, determining boundary conditions and their properties are also described.

3

Mechanizm oddziaływania wody na płomień gazowy i pyłowy

100%

Gieras M.

Prace Naukowe Politechniki Warszawskiej. Mechanika

|

2006

|

tom z. 212

3-112

PL

W pracy przedstawiono wyniki kompleksowych badań autora nad oddziaływaniem kropel wody na płomień gazowy i pyłowy z uwzględnieniem wpływu średnicy, prędkości i liczby podawanych kropel. W pierwszym etapie prowadzono badania zachowania się w płomieniu pojedynczych kropel zawieszonych na igle kwarcowej lub swobodnie spadających w polu grawitacyjnym. Ważnym elementem rozważań było wyeksponowanie w badanym zjawisku faktu dwustronnego oddziaływania między płomieniem i kroplą wody: z jednej strony zespołu procesów związanych z działaniem płomienia na kroplę, a z drugiej strony - zespołu procesów związanych z działaniem kropli na płomień. W drugim etapie przeprowadzono badania strug rozpylonej wody, w celu uogólnienia procesów zaobserwowanych podczas pierwszego etapu. W celu lepszego poznania mechanizmów oddziaływania między kroplami a płomieniem przeprowadzono badania również dla cząstek stałych - obojętnych oraz czynnych chemicznie. Zakres pracy obejmował także właściwy dobór i projekt rozpylaczy niezbędnych do uzyskania odpowiednich parametrów rozpylanej strugi wody. Stwierdzono, że woda może być bardzo dobrym środkiem gaśniczym, jeśli jest w odpowiedni sposób dostarczona do płomienia. Zastosowana do aktywnego superszybkiego systemu tłumienia wybuchów pyłowych i gazowych (realizowanego po części w ramach tej pracy) może skutecznie tłumić nawet bardzo szybko propagujące wybuchy, natomiast źle dobrane parametry rozpylanej strugi mogą stać się źródłem bardzo gwałtownej, niebezpiecznej dla człowieka akceleracji płomienia do prędkości wielokrotnie przewyższającej jego prędkość początkową. Opracowano proste modele matematyczne pozwalające wyliczyć maksymalne średnice kropel najskuteczniej gaszących płomień gazowy i pyłowy oraz pozwalające wyliczyć minimalne ilości wody potrzebnej do zgaszenia płomienia. Przeprowadzono symulacje procesów gaszenia i turbulizacji płomieni gazowych i pyłowych przez rozpylone strugi wody lub strugi cząstek neutralnych z uwzględnieniem wpływu na ten proces średnicy, prędkości oraz liczby podawanych kropel lub cząstek. Przedyskutowane zostało pojęcie optymalnej średnicy gaszącej kropli rozpylonej wody i praktyczne znaczenie tego faktu. Porównano wyniki otrzymane z badań doświadczalnych i teoretycznych.

EN

The monograph contains the experimental and numerical results of the complex author's research into the interaction of water and other extinguishing media with propagating gaseous and dust flames. The research was focused on two main problems: the mechanism of interaction of single water droplets (fixed at the end of glass needle or free falling) with propagating flame and mechanism of flame quenching, or its acceleration, by water sprays. To gain a better understanding these problems the neutral sand particles and typical extinguishing powders were also used. Special dispersing nozzles were designed and constructed. Several different mechanism of water behaviour, during their contact with flame front, depending on droplet size and flame velocity, were observed and described. From conducted experiments, it appears that water sprays, when properly dispersed, can be very effective as the flame extinguishing agent. Experiments with tested active suppression system have shown that water is also very effective in suppression, even for very violent dust explosion. If the suppression systems are not able to deliver the required quantity of water of the appropriate dispersing spectrum to stop combustion, then the explosion can even propagate faster and can be more violent. Mathematical models of water droplet evaporation in flame front were made and the results from the calculation of the maximum diameter of a droplet which can completely evaporate in the flame front were plotted. The minimum quantities of water spray which can cause a totally quenching flame were presented. Also a simulation of the flame suppression process by water sprays or neutral particles were made for different droplets or particles size and velocity. The idea of an optimal water spray droplets extinguishing diameter was discussed.

4

Computational study of an aerodynamic flow through a turbine engine combustor

100%

Gieras M.

Archivum Combustionis

|

2013

|

tom Vol. 33 nr 1

27--40

EN

The study presents 3-D numerical simulations of aerodynamic flow inside a GTD-350 turbine engine combustion chamber. The process of generating a numerical grid, determining boundary conditions and their properties are described. For the assumed boundary conditions, there were performed numerical simulations of the aerodynamics of cold airflow through the combustion chamber (without fuel supply to the interior) using Ansys CFX code. A numerical experiment was also conducted for the assumed difference of pressure at the inlet to each of the air supplying pipes. The work ends with a discussion of the results, in particular concerning the loss of pressure in the combustion chamber and possible design changes to minimize them.

5

Studies on process of dust explosion suppression by water spray

100%

Gieras M.

Archivum Combustionis

|

2011

|

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.

6

Interaction of water droplets with propagating gaseous flames

100%

Gieras M.

Archivum Combustionis

|

2000

|

tom Vol. 20 nr 1-2

49-61

EN

Results are presented from experimental and analytical studies on the influence of single water droplets on premixed gaseous flame propagation. The research was focused on the mechanism of interaction of single water droples with propagating methane flame. Experimental data were obtained in vertical standard tube 1.2 m. in length and of 0.05x0.05 m2 in cross-section. Several different mechanisms of water droplets behaviour during their contact with flame front, depending on droplet size and flame velocity, were observed and described.

7

Interaction of water sprays with gaseous flame

100%

Gieras M.

Archivum Combustionis

|

2001

|

tom Vol. 21 nr 4

245-259

EN

The influence of water sprays on propagation process of gaseous flames is presented in the paper. Data were obtained in the vertical perspex tube of 0.7 m in length and 0.08 m in diameter. Example pictures showing flame quenching and flame acceleration by means of water sprays are shown. Furthermore simplified mathematical calculations of maximum diameter of water droplets providing the effective suppression of propagating gaseous flame are made. Experimental results and theoretical considerations show that only the water sprays with droplets which are able totally evaporate in the flame front can be the most effective in fire suppression.

8

Constant volume explosion of organic dust - air mixture at microgravity and normal gravity

100%

Gieras M.

Archivum Combustionis

|

2000

|

tom Vol. 20 nr 3-4

73-90

EN

Comparative studies of the dust explosion process at normal gravity and microgravity conditions for different kinds of dust , different dust concentrations and different levels of dispersion turbulence are presented. The research was carried out in the 13.5 dm3 cylindrical combustion chamber with L/D=1. Microgravity experiments were conducted in the drop tower. Influence of the initial turbulence as well as natural convection on the dust explosion development was determined.

9

Three-zonal Wall Function for k-ε Turbulence Models

63%

Chmielewski M. , Gieras M.

Computational Methods in Science and Technology

|

2013

|

tom Vol. 19, No. 2

107--114

EN

Most commercially available wall functions for k-" turbulence models base on the two-zonal near-wall flow division assumption. Viscous and log-law sublayers are distinguished. In this article the three-zonal wall function concept with a buffer sublayer is developed. The aim of this new wall function is to improve the mean streamwise U+ velocity profile. The proposed wall function is validated on backward-facing step experimental data. Physical implications of the model performance are also discussed.

10

Planck Mean Absorption Coefficients of H2O, CO2, CO and NO for radiation numerical modeling in combusting flows

63%

Chmielewski M. , Gieras M.

Journal of Power Technologies

|

2015

|

tom Vol. 95, nr 2

97--104

EN

The Weighted-Sum-of-Gray-Gases Model (WSGGM), based on temperature dependent weighting factors, is an efficient method of determining the absorption coefficients in numerical modeling of combusting flows. Weighting factors are obtained by polynomial fitting of experimental data for only two reagents (H2O and CO2) to the analytical equation for emissivity. In this article the use of Planck Mean Absorption Coefficients (PMAC) for H2O, CO2, CO and NO in combustion numerical modeling is proposed. The aim of the PMAC approach is to improve the initial solution of temperature and species mass fraction profiles in numerical modeling of non-premixed methane combustion. The proposed model is verified against the results of turbulent, non-premixed methane combustion experimental data. The implemented PMAC model represents the flue gas composition and temperature more accurately than the WSGGM.

11

Numerical investigation of heat transfer in fuel-water emulsion droplet

63%

Rodzewicz R. , Gieras M.

Archivum Combustionis

|

2018

|

tom Vol. 38 nr 1

1--10

EN

This paper aims to iiwestigate heat flow in fuel/water emulsion droplet using ANSYS Fluent code. A model was tested under different boundary conditions including various flow temperatures, velocities, droplet sizes, water contents, etc. The rate of a temperaturę increment was monitored inside dispersed phase droplets. The obtained results were compared to find out in which case boiling point was reached in all water droplets simultaneously. Such a temperaturę distribution is suspected to be the main condition for microexplosion occurrence. However, this should be confirmed experimentally. Simulations show that a higher temperaturę and a smaller droplet diameter may promote microexplosion. Also it appears that there exists an optimal flow velocity, when the difference of time of reaching boiling point for every water droplet is the smallest. The minor, but a very interesting observation concerns a negligible impact of water presence on heat distribution. It has been shown that treating an emulsion droplet as a continuum with an averaged specific heat of water and oil may result in an error less than 1%. It is an useful conclusion that enables the analytical approach to the problem. The obtained results provide a solid basis for further experimental research.

12

Numerical simulation of flow and combustion in spark-ignition piston engine

63%

Jasiński D. , Gieras M.

Archivum Combustionis

|

2013

|

tom Vol. 33 nr 4

207--214

EN

The The paper presents results of numerical simulations of combustion processes inside a piston engine with spark-ignition. The simulation was performed using ANSYS Fluent. For simulation of the combustion process, a new model of combustion, being an extension of a model available in the software, taking into account gas recirculation was proposed. This model was then implemented in the program Fluent by means of the User Defined Scalars and User Defined Functions. As the object of analysis, Fiat FIRE 1108 engine was used. Comparison of the basic engine parameters, obtained from the simulations with actual engine performance, indicates a fairly good agreement, and thus possibility of applying of this approach in a simplified simulation of spark-ignition engines.

13

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

63%

Gieras M. , Jasiński D.

Archivum Combustionis

|

2011

|

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.

14

Study of combustion efficiency and pollutant emissions in a miniature gas turbine with the combustion chamber of variable geometry

63%

Chmielewski M. , Gieras M.

Rynek Energii

|

2015

|

tom Nr 4

103--109

EN

The study presents the influence of changes in the geometry of the combustor liner dilution holes on miniature gas turbine combustion efficiency and emissions of harmful substances. Among the many measurable parameters essential attention has been given to the measurement of the total temperature at the outlet of combustion chamber and measurements of the emissions of nitrogen oxides (NOx) and carbon monoxide (CO). The dilution holes area is controlled by rotating band at the rear part of the combustor liner, which is a modification of the standard combustion chamber of miniature gas turbine GTM-120, manufactured in Poland. The research was conducted on the test stand of the miniature combustion chamber. The combustion chamber is supplied with LPG in the start-up phase and with kerosene in the later phase. The tests provided information concerning NOx /CO dependence, total temperature at the outlet of the combustion chamber as a function of the rotational speed and percentage of covering of dilution holes. The results are related to the corresponding measurement parameters for the baseline geometry of the combustion chamber and the results obtained on a turbine GTM-120 test bench. Three-dimensional maps show considerable sensitivity of the combustion efficiency and the level of emissions to the degree of covering of the dilution holes, which makes it possible to build a control system to optimize the combustion process for a wide range of turbine speeds.

PL

W artykule przedstawiono eksperymentalne badania wpływu zmian geometrii otworów rozcieńczających komory spalania miniaturowej turbiny gazowej na efektywność procesów spalania i emisje substancji szkodliwych. Skupiono się przede wszystkim na pomiarach takich parametrów jak: temperatura całkowita za komorą spalania oraz emisja tlenków azotu (NOX) oraz tlenku węgla (CO). Przekrój otworów strefy rozcieńczającej regulowany jest za pomocą obrotowego pasa znajdującego się w tylnej części komory, stanowiącej modyfikację standardowej komory spalania miniaturowej turbiny gazowej polskiej produkcji – GTM-120. Badania przeprowadzono na stanowisku badan miniaturowych komór spalania. Komora spalania zasilana była naftą lotniczą. W wyniku przeprowadzonych badań uzyskano zależności emisji NOX/CO i temperatury całkowitej za komorą spalania w funkcji prędkości obrotowej i procentowego przysłonienia otworów rozcieńczających. Wyniki odniesione zostały do pomiarów analogicznych parametrów dla komory spalania o geometrii podstawowej oraz badań stanowiskowych turbiny GTM-120. Trójwymiarowe mapy wykazują znaczną wrażliwość efektywność spalania oraz poziomu emisji substancji szkodliwych na przysłaniania otworów strefy rozcieńczającej, co daje możliwość zbudowania systemu sterowania w celu optymalizacji procesu spalania w szerokim zakresie zmian prędkości obrotowej turbiny.

15

Computational study of an aerodynamic flow through a micro-turbine engine combustor

63%

Gieras M. , Stańkowski T.

Journal of Power Technologies

|

2012

|

tom Vol. 92, nr 2

68--79

EN

The study presents 3-D numerical simulations of aerodynamic flow inside micro-turbine engine combustion chamber. The process of creation of a numerical grid and its properties are described, and then on the basis of gas-dynamic calculation of the theoretical engine cycle boundary conditions were specified. For the assumed boundary conditions, numerical simulations of aerodynamics of "cold" air flow through the combustion chamber (without fuel supply to the interior) were performed. Numerical experiment was also conducted, allowing the investigation of the influence of thermal energy supply into the combustion chamber on the aerodynamic flow through the chamber. The work ends with discussion of the results, in particular concerning the loss of pressure in the combustion chamber and possible design changes to minimize them.

16

Trzy dziesięciolecia Elektrowni Bełchatów

63%

Blikowski E. , Gieras M.

Energetyka

|

2005

|

tom nr 8

515-516

PL

W dużym skrócie przedstawiono trzy dziesięciolecia istnienia Elektrowni Bełchatów, której historia rozpoczęła się w latach sześćdziesiątych ubiegłego stulecia. Odkrycie gigantycznych, jak na polskie warunki, złóż węgla brunatnego rozpoczęło tzw. epopeję bełchatowską. Dziś Elektrownia Bełchatów wchodzi w skład Grupy BOT i jest elektrownią produkującą w XXI w. najtańszą w Polsce i czystą ekologicznie energię elektryczną.

EN

There is presented briefly thirty years of existence of Bełchatów powerstation, which history began in sixties of the previous century. Discoveryof gigantic, in Polish conditions, lignite resources began so called Bełchatów epopee. Bełchatów power station belongs to day to the BOT Group and it generate in the XXI century the cheapest and the cleanest electric energy.

17

Effectiveness of an active dust and gas explosion suppression system

63%

Gieras M. , Klemens R.

Journal of Power Technologies

|

2012

|

tom Vol. 92, nr 1

1-11

EN

The research aimed to test the effectiveness of gas and dust explosion suppression by means of a super fast explosion suppression system with a volume of 5 dm3. Smokeless powder as an explosive charge and sodium bicarbonate as a suppressing material were used. The experiments were carried out using a prototype device - a 5 liter steel container, closed by means of an aluminum membrane. Approximately 1.75 kg of extinguishing powder was placed in the container. The membrane was ruptured by exploding a specially developed charge located inside a perforated steel combustion chamber and mounted over the suppressing powder surface. The system was triggered by a signal from the protected volume, sent by a pressure transducer or by a photodiode reacting to a developing flame. The investigations into the efficiency of the active explosion suppression system were carried out in the 1.3 m3 explosion chamber. The explosion was initiated in a corn starch-air mixture of 0.2 kg/m3 concentration, or in a methane-air mixture of 7.5% and 8.5% CH4 concentration. The explosion suppression process occurred through the action of the extinguishing powder blown out from the extinguisher after the compressed combustion products perforated the membrane.

18

Small gas turbine GTM-120 bench testing with emission measurements

63%

Chmielewski M. , Gieras M.

Journal of KONES

|

2015

|

tom Vol. 22, No. 1

47--54

EN

The aim of this paper is to provide comprehensive bench testing results for small gas turbine engine with a strong focus on the flue gas emission measurements. After a short overview of small gas turbine GTM-120 design and working principles, the test bench developed at the Institute of Heat Engineering at the Warsaw University of Technology is presented. Capability and accuracy of the sensors used in test bench are discussed in detail. Data acquisition software based on LabVIEW is also presented. Five separate sections representing successive engine stations have been distinguished. Experimental set of data of pressure and temperature on all of the stations is presented for the whole range of engine rotational speeds. Additionally, the engine thrust and fuel consumption data is provided. Special attention is given to the engine NOx and CO content in the engine exhaust gas, since turbine engine emissions are of great concern due to their adverse impact on natural environment. Experimental results are followed by the engine cycle parametric study for real engine thermodynamic cycle. Finally, future work plans regarding variable combustor chamber utilization for emission reduction from small gas turbine are discussed.

19

Miniature gas turbine with Variable Area Nozzle

51%

Fulara S. , Gieras M. , Chmielewski M.

Archivum Combustionis

|

2017

|

tom Vol. 37 nr 2

127--138

EN

Current scientific knowledge related to miniature turbochargers and gas generators is still improving. Various concepts are being tested seeking performance enhancement. Variable Area Nozzle (VAN) system is one of them. It aims to optimize effective area nozzle controlling both: turbine entry temperature and mass flow rate. The article presents different variable geometry concepts and recent research on VAN applied to a miniature gas turbine at Warsaw University of Technology. VAN concept and related phenomena are discussed.

20

Tłumienie wybuchu metanu z wykorzystaniem wysokociśnieniowej gaśnicy

51%

Szkudlarek Z. , Klemens R. , Gieras M.

Przegląd Górniczy

|

2014

|

tom T. 70, nr 4

74--80

PL

W artykule przedstawiono wstępne badania laboratoryjne nad skutecznością tłumienia wybuchów metanu z wykorzystaniem wysokociśnieniowej gaśnicy. Jako materiału tłumiącego użyto proszku gaśniczego składającego się głównie z kwaśnego węglanu sodu (NaHCO3). Badania prowadzone były w komorach wybuchowych o pojemnościach 1,3 m3 i 10 m3, w których badano wpływ parametrów decydujących o procesie rozpylania i określano skuteczność tłumienia wybuchu metanu oraz na poligonie doświadczalnym, gdzie badano kształt i zasięg obłoku proszku gaśniczego wysokociśnieniowej gaśnicy. Przeprowadzone badania laboratoryjne pozwoliły na wyeliminowanie niedoskonałości w konstrukcji gaśnicy o objętości 10 dm3 oraz wykazały, że możliwe jest skuteczne tłumienie w początkowej fazie wybuchu metanu.

EN

This paper presents the initial laboratory tests on efficiency of suppression of methane explosion with the use of the high- -pressure fire extinguisher. Extinguishing powder consisting mainly of sodium bicarbonate (NaHCO3) was used. The tests were carried out in explosion chambers of capacity 1.3 m3 and 10 m3, in which the parameters decisive in powder spraying were tested as well as efficiency of suppression of methane explosion was determined. In addition, the shape and range of powder cloud ejected from high-pressure extinguisher were tested in the experimental field. The tests enable w eliminate any imperfections in the design of fire extinguisher of capacity 10 dm3 and have proved that it is possible to extinguish successfully methane explosion at its early stage.