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1

Numerical investigation of the back pressure influence on urea-water-solution mixing performance in close coupled SCR system

Rogóż R., Bachanek J., Boruc Ł., Teodorczyk A.

Journal of KONES

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2018

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Vol. 25, No. 3

377--383

EN

The upcoming Euro 6d emission standard puts more even stringent requirements for diesel engine cars, especially in the case of nitrogen oxides (NOx) emission. The most widely used technique to meet tight standards is Selective Catalytic Reduction (SCR) with urea-water-solution (UWS) injection. One of the crucial factors is even ammonia distribution at the catalyst inlet; hence, very often product development is focused around this issue. The product development is supported by both experimental and numerical work. The common approach to measure cross section ammonia distribution on the SCR is using sampling system at catalyst outlet. Very often exhaust layout is opened just after the SCR catalyst, cutting off the rest part for instance tailpipe or Clean-up Catalyst. Therefore, a backpressure at SCR outlet resulting from the downstream part is also eliminated. This could significantly affect flow parameters as the density changes, thus ammonia distribution and wall film deposition may vary as well. Within this work, the influence of the backpressure at SCR outlet on the ammonia distribution and wall wetting was numerically investigated. The simulations were run under various boundary conditions for the Close Coupled SCR architecture. It was shown that depending on the operating point the boundary pressure affects both factors on the different level.

2

Numerical analysis of heat conduction influence on SCR aftertreatment systems EFF

Bachanek J., Rogóż R., Teodorczyk A.

Journal of KONES

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2018

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Vol. 25, No. 3

51--58

EN

Selective Catalytic Reduction (SCR) is well known method for reducing NOx emission in diesel engine exhaust gas. Urea-water solution (UWS) injected into hot stream decomposes due to thermolysis into ammonia and isocyanic acid which hydrolyses further into more ammonia and carbon dioxide. Resultant ammonia is the NOx reductor, producing water vapour and carbon dioxide from the reduction reaction. To provide sufficient NOx reduction efficiency, UWS needs to be properly atomized and mixed with exhaust gas. However, due to more and more restrictive emissions regulations provided by European Union and Close Coupled trend of aftertreatment systems in vehicles the design process is very complex and demanding. Computational Fluid Dynamics (CFD) simulations are integral part of product development, allowing save time and reduce costs of preparing prototypes for further tests. However, it is necessary to understand all the processes and problems connected with NOx reduction in SCR system. Strong turbulent flow of hot stream gas, urea-water solution spray injection, droplets interaction with wall, wallfilm generation are included. The objective of this work is to investigate the impact of heat transfer modelling inside mixing elements of SCR system on urea mixing uniformity and wallfilm deposit on the walls of the system. Simplified and more complex approach is compared with no heat transfer cases. All the simulations were conducted using AVL FIRETM software. Results showed that wall heat transfer might have an impact on mixing efficiency and wallfilm formulation. It is necessary to take into account the effect of mixing elements heat conduction in CFD simulations during the aftertreatment design process.

3

Laminar burning velocity predictions of single-fuel mixtures of C1-C7 normal hydrocarbon and air

Jach A., Żbikowski M., Teodorczyk A.

Journal of KONES

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2018

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Vol. 25, No. 3

227--235

EN

The numerical modelling of combustion phenomena is an important task due to safety issues and development and optimization of engines. Laminar burning velocity (LBV) is one of the most important physical properties of a flammable mixture. Knowing its exact value if crucial for assessment of flame stabilization, turbulent flame structure. It influences strongly safety, probability of knocking combustion and it is one of parameters used for assessment and development of detailed chemical kinetic mechanisms. Hence, the goal of this work is to develop models by means of Machine Learning algorithms for predicting laminar burning velocities of single-fuel C1-C7 normal hydrocarbon and air mixtures. Development of the models is based on a large experimental data set collected from literature. In total more than 1000, LBVs were accumulated for hydrocarbons from methane up to n-heptane. The models are developed in MATLAB 2018a with use of Machine Learning toolbox. Algorithms taken into account are multivariate regression, support vector machine, and artificial neural network. Performance of the models is compared with most widely used detailed chemical kinetics mechanisms’ predictions obtained with use of LOFEsoft. These kind of models might be efficiently used in CFD combustion models based on flamelet approach. The main advantage in comparison to chemical kinetics calculation is much shorter computational time needed for computations of a single value and comparable performance in terms of R2 (coefficient of determination), RMSE (root-mean-square error) and MAE (mean absolute error).

4

CFD simulations as a support of experimental research in a rapid compression expansion machine facility

Jach A., Pyszczek R., Kapusta Ł. J., Teodorczyk A.

Journal of KONES

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2018

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Vol. 25, No. 4

141--147

EN

The main aim of this study to reproduce methane combustion experiment conducted in a rapid compressionexpansion machine using AVL FIRETM software in order to shed more light on the in-cylinder processes. The piston movement profile, initial and boundary conditions as well as the geometry of the combustion chamber with a prechamber were the same as in the experiment. Authors by means of numerical simulations attempted to reproduce pressure profile from the experiment. As the first step, dead volume was tuned to match pressures for a non-combustion (air-only) case. Obtained pressure profile in air compression simulations was slightly wider (prolonged occurrence of high pressure) than in the experiment, what at this stage was assumed to have negligible significance. The next step after adjusting dead volume included combustion simulations. In the real test facility, the process of filling the combustion chamber with air-fuel mixture takes 15 s. In order to shorten computational time first combustion simulations were started after the chamber is already filled assuming uniform mixture. These simulations resulted in more than two times higher maximum pressure than recorded in experiments. It was concluded that turbulence decays quickly after filling process, what was also confirmed by next combustion simulations preceded by the filling process. Then the maximum pressure was significantly decreased but still it was higher than in the experiments. Based on the obtained results it was assumed that the discrepancy noticed in air cases is further increased when combustion is included. Moreover, the obtained results indicated that pre-combustion turbulence level is very low and suggested that either piston profile movement is not correct or there is high-pressure leak in the test facility.

5

Badania eksperymentalne i numeryczne detonacji mieszanin wodorowo-powietrznych

Żbikowski M., Dąbkowski A., Lesiak P., Bąk D., Dziechciarz A., Teodorczyk A.

Przemysł Chemiczny

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2017

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T. 96, nr 4

858--862

PL

Wyznaczono parametry detonacji mieszanin wodorowo-powietrznych w szerokim zakresie stężeń wodoru w powietrzu (15–60% obj.). Stanowisko eksperymentalne składało się z rury detonacyjnej o średnicy wewnętrznej 0,17 m i długości 9,0 m, zamkniętej z obu stron, sekcji napędzającej o długości 0,6 m, umieszczonej wewnątrz kanału, oraz systemu akwizycji danych (czujniki ciśnienia, sondy jonizacyjne). Do zmierzenia wielkości komórek detonacyjnych wykorzystano folię z naniesioną sadzą. Celem badań było znalezienie górnej i dolnej granicy spalania detonacyjnego, a także wyznaczenie charakterystycznych wielkości komórek detonacyjnych oraz prędkości propagacji fali detonacyjnej. Teoretyczne parametry detonacji (prędkość propagacji i czas indukcji) określono na podstawie modelu Zeldovicha, von Neumanna i Doringa (ZND). Badania eksperymentalne wykorzystano do walidacji symulacji numerycznej przeprowadzonej w programie OpenFoam. Wyniki obliczeń porównano z danymi eksperymentalnymi. Model bazował na równaniach Naviera i Stokesa uśrednionych metodą Reynoldsa (RENS) oraz równaniu transportu, w którym człon źródłowy odpowiadał za samozapłon mieszaniny.

EN

H₂-air mixts. (H₂ content 15–60% by vol.) were detonated to det. the wave propagation rate and induction time. The exptl. data were used for validation of a numerical simulation. A good agreement of the data was achieved.

6

Numerical simulations of n-heptane spray in high pressure and temperature environments

Smuga W., Kapusta Ł. J., Teodorczyk A.

Journal of Power Technologies

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2017

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Vol. 97, nr 1

1--6

EN

In this study n-heptane spray in supercritical environments was simulated using commercial CFD (Computational Fluid Dynamic) software AVL Fire. The numerical results were analyzed in terms of global spray parameter, and spray penetration. The results obtained were compared with experimental data available at Sandia National Laboratories. N-heptane spray simulations were performed in the same conditions as in the Sandia experiments. The goal of the study was to assess whether the Lagrangian approach performs well in engine relevant conditions in terms of spray global parameters. Not included in this assessment was the influence of supercritical mixing on liquid-gas interphase. The major element was the potential for practical application of the commercial CFD code in terms of properly representing global spray parameters and thus mixture formation in supercritical conditions, which is one of the core aspects in whole engine process simulation. The key part of the study was mesh optimization. Therefore, the influence of mesh density on both the accuracy of calculations and the calculation time was determined, taking into consideration detailed experimental data as initial conditions for the subsequent calculations. This served as a basis to select the optimal mesh with regard to both accuracy of the results obtained and time duration of the calculations. As a determinant of accuracy, the difference within a range of evaporated fuel stream was used. Using selected mesh the set of numerical calculations were performed and the results were compared with experimental ones taken from the literature. Several spray parameters were compared: spray tip penetration, temperature of the gaseous phase and mixture fraction in the gaseous phase. The numerical results were very consistent in respect of spray tip penetration. The other parameters were influenced by specific features of the Lagrangian approach. Nevertheless the results obtained showed that the Lagrangian approach may be used for engine relevant conditions.

7

LES numerical study on in–injector cavitating flow

Pyszczek R., Kapusta Ł. J., Teodorczyk A.

Journal of Power Technologies

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2017

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Vol. 97, nr 1

52--60

EN

In this paper a computational study on hexane flow in a fuel injector is presented. Large Eddy Simulation (LES) was used to capture the turbulent patterns present in the flow. The main aim was to investigate the cavitation phenomenon and its interaction with turbulence as well as the influence of injection pressure and backpressure on fuel mass flow and flow conditions. Analysis of the approach to define the outlet boundary conditions in terms of convergence time and fluid mass outflow oscillations formed a crucial part of the study. Numerical simulations were performed with AVL Fire CFD (Computational Fluid Dynamics) software. The Euler-Euler approach and multifluid model for multiphase flow modelling were applied. Injector needle movement was included in the simulation. Results show that the additional volumes attached to the nozzle outlets improved the convergence of the simulations and reduced mass outflow oscillations. Fuel mass flow at the outlets was dependent on inlet pressure, position of the needle and backpressure, while the influence of backpressure on fuel mass flow was negligible. The presence of the vapor phase at the exit of the nozzles did not affect average fuel mass flow. All the simulations showed interaction between the gaseous phase distribution and the turbulence of the flow.

8

The influence of the injection frequency on the urea selective catalytic reduction systems performance

Rogóż R., Jaworski P., Kapusta Ł. J., Teodorczyk A.

Combustion Engines

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2017

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R. 56, nr 3

73--77

EN

This study presents the influence of the UWS injection frequency on a close coupled SCR systems performance. The investigation was performed with the CFD tool AVL Fire. In the paper the analysis of four different UWS injection frequencies in the three different operating points of diesel engine was shown. The assessments of the system performance was referred to the ammonia distribution at catalyst intake and wall film formation inside the investigated geometry, as these are considered as crucial in such a configuration. The results showed that injection frequency affects both factors on different level depending from the flow conditions. In addition, the wall film crystallization risk was discussed basing on the obtained wall film characteristics.

9

The closed-cycle model numerical analysis of the impact of crank mechanism design on engine efficiency

Opaliński M., Teodorczyk A., Kalke J.

Combustion Engines

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2017

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R. 56, nr 1

153--160

EN

The research presents a review and comparison of different engine constructions. Investigated engines included crankshaft engines, barrel engine, opposed-piston engines and theoretical models to present possible variations of piston motion curves. The work comprises also detailed description of a numerical piston engine model which was created to determine the impact of the cycle parameters including described different piston motion curves on the engine efficiency. Developed model was equipped with Wiebe function to reflect a heat release during combustion event and Woschini’s correlation to simulate heat transfer between the gas and engine components.Various scenarios of selected engine constructions and different working conditions have been simulated and compared. Based on the results it was possible to determine the impact of different piston motion curves on the engine cycle process and present potential efficiency benefits.

10

Numerical investigation on low calorific syngas combustion in the opposed-piston engine

Pyszczek R., Mazuro P., Jach A., Teodorczyk A.

Combustion Engines

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2017

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R. 56, nr 2

53--63

EN

The aim of this study was to investigate a possibility of using gaseous fuels of a low calorific value as a fuel for internal combustion engines. Such fuels can come from organic matter decomposition (biogas), oil production (flare gas) or gasification of materials containing carbon (syngas). The utilization of syngas in the barrel type Opposed-Piston (OP) engine arrangement is of particular interest for the authors. A robust design, high mechanical efficiency and relatively easy incorporation of Variable Compression Ratio (VCR) makes the OP engine an ideal candidate for running on a low calorific fuel of various composition. Furthermore, the possibility of online compression ratio adjustment allows for engine the operation in Controlled Auto-Ignition (CAI) mode for high efficiency and low emission. In order to investigate engine operation on low calorific gaseous fuel authors performed 3D CFD numerical simulations of scavenging and combustion processes in the 2-stroke barrel type Opposed-Piston engine with use of the AVL Fire solver. Firstly, engine operation on natural gas with ignition from diesel pilot was analysed as a reference. Then, combustion of syngas in two different modes was investigated – with ignition from diesel pilot and with Controlled Auto-Ignition. Final engine operating points were specified and corresponding emissions were calculated and compared. Results suggest that engine operation on syngas might be limited due to misfire of diesel pilot or excessive heat releas which might lead to knock. A solution proposed by authors for syngas is CAI combustion which can be controlled with application of VCR and with adjustment of air excess ratio. Based on preformed simulations it was shown that low calorific syngas can be used as a fuel for power generation in the Opposed-Piston engine which is currently under development at Warsaw University of Technology.

11

Investigation of glycerol doping on ignition delay times and laminar burning velocities of gasoline and diesel fuel

Jach A., Cieślak I., Teodorczyk A.

Combustion Engines

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2017

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R. 56, nr 2

167--175

EN

Glycerol is a major by-product of biodiesel production. Per one tone of produced biodiesel, one hundred kilograms of glycerol is produced. Production of glycerol is increasing due to increase of demand for biodiesel. One of methods of glycerol utilization is combustion. Recent experimental studies with use of a diesel engine and a constant volume combustion chamber show that utilization of glycerol as a fuel results in lower NOx emissions in exhaust gases. It combusts slower than light fuel oil, what is explained by higher viscosity and density of glycerol. Glycerol has low cetane number, so to make combustion in a diesel engine possible at least one of the following conditions need to be fulfilled: a pilot injection, high temperature or high compression ratio. The aim of the paper is to compare glycerol to diesel and to assess influence of glycerol doping on gasoline and diesel fuel in dependence of pressure, temperature and equivalence ratio. The subject of this study is analysis of basic properties of flammable mixtures, such as ignition delay times and laminar burning velocities of primary reference fuels (diesel: n-heptane and gasoline: iso-octane). Calculations are performed with use of Cantera tool in Matlab and Python environments. Analyses of influence of glycerol on ignition delay times of n-heptane/air and iso-octane/air mixtures covered wide range of conditions: temperatures from 600 to 1600 K, pressure 10-200 bar, equivalence ratio 0.3 to 14, molar fraction of glycerol in fuel 0-1 in air. Simulations of LBV in air cover temperatures: 300 K and 500 K, pressures: 10, 40, 100, 200 bar and equivalence ratio from 0.3 to 1.9. Physicochemical properties of gasoline, diesel and glycerol are compared.

12

Prediction of gas mixture reactivity based on detonation pipe vibrations

Marcinkiewicz K., Żbikowski M., Lesiak P., Teodorczyk A.

Archivum Combustionis

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2017

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Vol. 37 nr 1

43--77

EN

The aim of this paper is to make an approach of creation a machine learning system predicting gas mixture composition being burned in a process pipe, based on pipe vibrations measurements. Task is divided into two parts: performing an experiment to get a necessary experimental data, and developing prediction algorithm. First, the basic principles of machine learning and signal processing are presented. Machine learning is the subfield of computer science that focuses on creating algorithms that can learn from provided data and perform predictions, either classification or regression. Signal processing is a general statement for all activities performed on information in form of a signal. In this particular work the emphasis is put on Fourier transform. After introduction, a brief description of the pipe response to internal detonation and pressure load is provided. It is of most significance, since the sensors used in the experiment base on pipe vibrations. Finally, the experimental part is described. The experiment consisted of performing a series of hydrogen-air explosion in pipes, with various hydrogen concentration. Measurement is performed with three sensors: piezoelectric sensor, knock combustion sensor - both measuring vibrations of pipe - and a pressure sensor, measuring pressure. This data is fed to a machine learning algorithm, that works as follows: first, measurement from a sensor is interpolated using b-splines. Then it transposes data from time domain to frequency domain using Fourier transform. Afterwards it is merged into one array. The set is divided into training and scoring sets, using cross-validation techniques. Training sets are used to feed classificator: SVM, SGD, naive Bayes, logistic regression, linear SVC, Ada Boost, perceptron. From this algorithm the prediction score of each classificator is derived and arranged with each other. It appears, that the algorithms used in conjunction with piezoelectric sensor give the score averaging to 50 %. The analysis of frequency spectrum is needless, since there is not enough features. The best classifiers are Perceptron, Naive Bayes and Support Vector Machine. Data from pressure sensor give much better results, with accuracy even up to 90 %. Fourier transform boosts the accuracy of classifiers. The best one is logistic regression. Therefore prediction of gas mixture reactivity based on detonation pipe vibration is possible.

13

Compression Auto-Ignition Control in a 2-stroke Barrel-type Opposed-Piston Engine

Pyszczek R., Mazuro P., Teodorczyk A.

Archivum Combustionis

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2017

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Vol. 37 nr 1

25--42

EN

The aim of this study is to investigate a possibility of Compression Auto-Ignition (CAI) control in a turbocharged 2-stroke barrel type Opposed-Piston (OP) engine fueled with a gasoline. The barrel type OP engine arrangement is of particular interest for the authors because of its robust design, high mechanical efficiency and relatively easy incorporation of a Variable Compression Ratio (VCR). A 3D CFD numerical simulations of the scavenging and combustion processes were performed with use of the AVL Fire solver that is based on a Finite Volume Method (FVM) discretization and offers a number of tools dedicated to numerical simulations of working processes in internal combustion engines. The VCR and water injection were considered for the ignition timing control. A number of cases was calculated with different engine compression ratios, different equivalence ratios and different amount of injected water. Results show that proposed measures should be appropriate for controlling the CAI combustion process. Furthermore, application of these solutions in the real engine can significantly contribute to increase in efficiency and decrease in emissions.

14

Numerical and experimental investigation of methane-oxygen detonation in a 9 m long tube

Malik K., Żbikowski M., Teodorczyk A., Lesiak P.

Journal of KONES

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2016

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Vol. 23, No. 4

311--318

EN

Numerical investigation of methane-oxygen detonation parameters was conducted with an OpenFoam code. Custom solver ddtFoam made especially for detonation problems was made use of. It uses the HLLC scheme to resolve the discontinuities and the subgridscale model to improve results on coarse meshes. Combustion model is based on progress variable equation, which contains two source terms. The first is the deflagrative source term and is modelled using the Weller correlation. The second is the detonative source term and it accounts for autoignition effects. Range of analysed gaseous mixture compositions was 20, 33 and 40% of methane in oxygen. The 2D calculation geometry was a 9 m long pipe with diameter 0.17 m. The mesh consisted of 382 500 hexahedral cells with the dimensions of 2x2 mm. Experimental results such as pressure profiles and detonation velocities are presented. Simulations were performed using LES turbulence model (k-equation-eddy-viscosity model) and compared with experimental data. Various dynamic parameters, like for example reaction lengths for methane-oxygen detonations, are estimated from the steady ZND analyses conducted in Cantera and SDToolbox libraries and based on GRI 3.0 kinetic mechanism of methane combustion. These lengths were then used in empirical formulas to obtain the characteristic cell sizes and assessed against experimental data.

15

Influence of exhaust gas on detonation propensity of a mixture of carbon monoxide, hydrogen and air

Jach A., Teodorczyk A.

Journal of KONES

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2016

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Vol. 23, No. 2

155--161

EN

A detonation is the strongest form of all gas explosions. The ease with which a flammable mixture can be detonated (detonability) commonly and traditionally is classified by a detonation cell width λ and an ignition delay time behind the detonation leading shock τ. Additionally, two more parameters were proposed 3 years ago – χ and RSB, which inform about regularity of a detonation structure. The problem of a detonation is significant in industry, in particular in power engineering, where restricted emission standard impose to introduce hydrogen-rich fuels, such as syngas. The most possible initiation of a detonation in industrial conditions is deflagration to detonation transition (DDT), where a deflagration under some conditions (obstacles, confinement, etc.) accelerates and a transition to a detonation takes places. In industry, this acceleration of a flame may progress in initially smoke-filled space. The goal of this paper is to analyse influence of exhaust gas on detonation propensity of a mixture of carbon monoxide and hydrogen. The analysis concerns the detonation cell width λ, ignition delay time τ, RSB and χ parameters. The composition of exhaust gas is calculated by setting it to a state of chemical equilibrium. Combustion temperature influence on exhaust gas composition is assessed. Species, which have the strongest influence on detonability, are assessed. Computations are performed with the use of Cantera tool.

16

Temperature effect on explosion parameters of hydrogen-air deflagrations in presence of water vapor

Grabarczyk M., Żbikowski M., Mężyk Ł., Teodorczyk A.

Challenges of Modern Technology

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2016

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Vol. 7, no. 3

39-44

EN

Results of investigation of hydrogen-air deflagrations phenomenon in closed vessel in various initial temperatures and volume fraction of water vapor are presented in following paper. Tests were performed in apparatus which construction complies with EN 15967 recommendations—20-litre sphere. Studied parameters were explosion pressure (Pex) and maximum explosion pressure (Pmax). Defining the influence of the initial conditions (temperature and amount of water vapor) on the maximum pressure of the hydrogen-air deflagration in a constant volume was the main aim. Initial temperatures were equal to 373K, 398K and 413K. Initial pressure was ambient (0.1 MPa). Hydrogen volume fraction differed from 15% to 80%, while humidity volume fraction from 0% to 20%. Ignition source was placed in geometrical center of testing chamber and provided energy between 10-20J from burnout of fuse wire with accordance to abovementioned standard. Common features of all experimentally obtained results were discussed. Maximum explosion pressure (Pmax) decreases with increasing the initial temperature. Furthermore, addition of the water vapor for constant initial temperature decreases value of Pmax and shifts the maximum peak to the direction of lean mixtures. Data provided in paper can be useful in assessment of explosion risk of industry installations working with hydrogen-air atmospheres with high water vapor addition.

17

Wpływ temperatury na ciśnienie wybuchu mieszanin izooktanu i izomerów alkoholu butylowego

Grabarczyk M., Teodorczyk A.

Bezpieczeństwo i Technika Pożarnicza

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2016

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Vol. 42, nr 2

65--79

PL

Cel: Celem artykułu jest przedstawienie wyników przeprowadzonych prac eksperymentalnych dotyczących wpływu temperatury na wybrane parametry wybuchowości, tj. ciśnienie wybuchu Pex oraz maksymalne ciśnienie wybuchu Pmax. Dodatkowo dokonany został przegląd literatury na temat wyżej wymienionych oraz dwóch dodatkowych parametrów tj. szybkości narastania ciśnienia wybuchu (dp/dt)ex oraz maksymalnej szybkości narastania ciśnienia wybuchu (dp/dt)max. Projekt i metody: Badania wykonano przy użyciu aparatury, której budowa jest zgodna z wytycznymi normy PN-EN 15967. Zbiornik badawczy stanowiła sferyczna komora o objętości 20 l, doposażona w dodatkowe układy o różnym przeznaczeniu, m.in. układ przygotowania mieszaniny paliwowo-powietrznej, układ akwizycji danych, układ bezpieczeństwa oraz układ stabilizacji temperatury. Źródło zapłonu umieszczone było w geometrycznym środku zbiornika badawczego i realizowane poprzez przepływ prądu przez prosty odcinek drutu topikowego włączonego między dwa metalowe pręty tak, aby wyzwalana energia mieściła się w zakresie od 10 do 20 J, ponieważ energia z tego zakresu nie wpływa w znaczący sposób na wielkości oznaczanych parametrów. Mieszaniny przygotowywano w oparciu o metodę ciśnień cząstkowych, która została omówiona w artykule. Ciśnienie początkowe badanych mieszanin palnych przed przyłożeniem źródła zapłonu było równe atmosferycznemu. Wyniki: W artykule zawarto wyniki prac eksperymentalnych z oznaczania parametrów maksymalnego ciśnienia wybuchu Pmax w funkcji temperatury oraz ciśnienia wybuchu Pex w funkcji temperatury oraz współczynnika ekwiwalencji (Φ), który jest odwrotnością współczynnika nadmiaru powietrza (λ). Badanymi substancjami były pary cieczy palnych, w tym: n-butanolu, sec-butanolu oraz izooktanu. Pomiary przeprowadzono zarówno dla ich samodzielnego występowania w atmosferze powietrznej oraz dla ich mieszanin binarnych (tj. dwuskładnikowych). Zebrane wyniki poddano ocenie oraz analizie. Każdy pomiar powtarzano od 3 do 5 razy. Wnioski: Otrzymane wyniki prac eksperymentalnych wykazują kilka wspólnych cech, w tym: obniżanie się wielkości Pmax wraz ze wzrostem temperatury; występowanie wielkości Pmax dla mieszanin o stężeniu bliskim stechiometrycznemu po stronie mieszanin bogatych w paliwo (1 < Φ < 1,5); zbieganie się trendów Pex w kierunku dolnej granicy palności (Φ < 1); występowanie szerszego zakresu wybuchowości, lecz niższych wielkości parametrów ciśnienia wybuchu po stronie mieszanin bogatych w paliwo (Φ > 1); brak symetrii trendu pomiędzy mieszaninami bogatymi (Φ > 1) a ubogimi (Φ < 1) w paliwo.

EN

Purpose: The main aim of the following paper is to present results from experiments regarding the influence of temperature on selected explosion parameters such as explosion pressure Pex and maximum explosion pressure Pmax. Morover literature was reviewed on the parameters mentioned above along with two additional parameters, ie. rate of the explosion pressure rise (dp/dt)ex and maximum rate of explosion pressure rise (dp/dt)max. Project and methods: The tests were performed using an apparatus, which was build according to the guidelines defined in PN-EN 15967. The test vessel was a 20 L spherical chamber equipped with additional systems for various purposes, including: fuel-air mixture preparation system, data acquisition system, security system and temperature stabilization system. Ignition source was placed in geometric center of the vessel and carried out by a current passing through a section of a straight fuse wire that was placed between two metal rods. The released energy was to be between 10 to 20 J, because this energy range does not substantially affect the value of the determined parameters. The mixtures were prepared according to the method of partial pressures explained in the paper. Initial pressure of flammable mixtures before applying the ignition source was ambient. Results: The paper contains the results of experiments regarding the maximum explosion pressure Pmax versus temperature and pressure explosion Pex versus temperature and fuel-air equivalence ratio (Φ), which is reciprocal of air-fuel equivalence ratio (λ). Tested substances were flammable liquids: n-butanol, sec-butanol and isooctane. Measurements were performed for their single-constituent mixtures with air and for their blends (binary mixtures) also with air. The collected results were preliminary assessed and analyzed. Each test was repeated from 3 to 5 times. Conclusions: The obtained experiment results indicate a number of common features including the following: decrease of Pmax value together with the increase of temperature; the presence of Pmax value for the mixtures with a concentration close to the stoichiometric one of fuel-rich mixtures (1 < Φ < 1,5); convergance of Pex trends towards the lower flammability limit (Φ < 1); the presence of a wider range of explosiveness, but a lower number of parameters of explosion pressure of fuel-rich mixtures (Φ > 1); no symmetry between the trend of mixtures fuel-rich mixtures (Φ> 1) and fuel-lean mixtures (Φ <1).

18

The influence of methane addition on the propagation of hydrogen-methane-air detonation in partially confined geometry

Cieślak I., Rudy W., Teodorczyk A.

Archivum Combustionis

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2016

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Vol. 36 nr 2

121--130

EN

The aim of this study was to perform the experiments of detonation propagating in stoichiometric hydrogen-methane-air mixtures in partially confined geometry. The experiments were done to examine the influence of the methane fraction in fuel on the ability of detonation to propagate. Four types of gaseous mixture composition were used: 0%, 2.5%, 5% and 10% of methane in fuel. The critical height h* was found for each mixture. Furthermore, by using the smoked-foil technique the detonation cell sizes λwere measured and the correlations h*/λ were calculated for each mixture. The results showed that detonation of hydrogen-methane-air mixture may propagate in partially confined geometry only when the channel height is at least equal to 1 cell size which is similar to the condition for planar detonation propagating in closed, rectangular channel. The research showed high influence of the boundary dividing the flammable layer from the air layer.

19

Numerical analysis of detonation propensity of hydrogen-air mixtures with addition of methane, ethane or propane

Jach A., Teodorczyk A.

Archivum Combustionis

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2016

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Vol. 36 nr 1

47--58

EN

The detonation propensity of hydrogen-air mixtures with addition of methane, ethane or propane in wide range of compositions is analyzed. The analysis concerned the detonation cell width, ignition delay time, RSB and χ parameters. Results are presented as a function of hydrogen molar fraction. Computations were performed with the use of three Cantera 2.1.1. scripts in the Matlab R2010b environment. The validated mechanisms of chemical reactions based on data available in the literature were used. Six mechanisms were assessed: GRI-Mech 3.0, LLNL, SanDiego, Wang, POLIMI and AramcoMech. In conclusion, the relation between detonation propensity parameters is discussed.

20

Numerical study on in-cylinder blending by means of a simultaneous direct injection of two liquid fuels in a heavy duty compression ignition engine

Kapusta Ł. J., Teodorczyk A.

Transactions of the Institute of Fluid-Flow Machinery

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2015

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nr 128

5--18

EN

Dual fuel combustion has been recently of high interest, mainly in terms of utilization of fuels different than diesel fuel in compression ignition engines. Depending on the properties of a fuel which is additional to diesel fuel, and the type of the additional fuel supply method the combustion process may be strongly modified comparing to single fuel combustion. Nowadays the modification of the combustion process becomes the reason for implementing the dual fuelling process. However, still the main reason for its implementation remains the utilization of nonconventional fuels in compression ignition engines. Among different types of dual fuel systems the one based on simultaneous direct injection of two fuels seems to be most flexible one. It allows to stratify the charge in the cylinder, blend two different fuels at any ratio and does not decrease volumetric efficiency. Therefore, this study aims at mixture formation in a heavy duty engine employing simultaneous direct injection of two different liquid fuels. Special attention was paid to spray breakup and simultaneous evaporation of two fuels which are the key processes in mixture formation.