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1

Detonation Characteristics of a NOx-Free Mining Explosive Based on Sensitised Mixtures of Low Concentration Hydrogen Peroxide and Fuel

Araos M., Onederra I.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 4

759--774

EN

Mining explosives based on ammonium nitrate(V) are safe and effective, however, the risk of NOx fume production during blasting is still present. In 2013, a project to eliminate NOx fumes from blasting began and hydrogen peroxide was chosen to replace ammonium nitrate(V) as the oxidiser. Previous work in this area demonstrated that hydrogen peroxide/fuel-based mixtures were able to detonate, provided that they are initiated under a situation of high confinement and also using hydrogen peroxide at relatively high concentrations. In contrast, a comprehensive study was conducted to determine the detonation properties of hydrogen peroxide/fuel-based mixtures that used hydrogen peroxide at lower concentrations (below 50 wt.%), detonated in unconfined conditions and used void sensitisation to achieve an efficient detonation reaction. This article presents the results of the influence of the density, water content, critical diameter and type of void sensitisation on the velocity of detonation (VOD) of hydrogen peroxide/ fuel-based explosive mixtures. The results indicate that the mixtures can achieve a different VOD which depends on the size of the sensitising voids and more importantly, the mixtures behave as non-ideal explosive, similarly to ammonium nitrate-based explosives, but with the advantage of being a NOx-free explosive.

2

Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments

Surała W., Sadowski M. J., Kwiatkowski R., Jakubowski L., Żebrowski J.

Nukleonika

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2016

|

Vol. 61, No. 2

161--167

EN

The paper reports results of the recent experimental studies of pulsed electron beams and soft X-rays in plasma-focus (PF) experiments carried out within a modifi ed PF-360U facility at the NCBJ, Poland. Particular attention was focused on time-resolved measurements of the fast electron beams by means of two different magnetic analyzers, which could record electrons of energy ranging from about 41 keV to about 715 keV in several (6 or 8) measuring channels. For discharges performed with the pure deuterium fi lling, many strong electron signals were recorded in all the measuring channels. Those signals were well correlated with the fi rst hard X-ray pulse detected by an external scintillation neutron-counter. In some of the analyzer channels, electron spikes (lasting about dozens of nanoseconds) and appearing in different instants after the current peculiarity (so-called current dip) were also recorded. For several discharges, fast ion beams, which were emitted along the z-axis and recorded with nuclear track detectors, were also investigated. Those measurements confi rmed a multibeam character of the ion emission. The time-integrated soft X-ray images, which were taken side-on by means of a pinhole camera and sensitive X-ray fi lms, showed the appearance of some fi lamentary structures and so-called hot spots. The application of small amounts of admixtures of different heavy noble gases, i.e. of argon (4.8% volumetric), krypton (1.6% volumetric), or xenon (0.8% volumetric), decreased intensity of the recorded electron beams, but increased intensity of the soft X-ray emission and showed more distinct and numerous hot spots. The recorded electron spikes have been explained as signals produced by quasi-mono-energetic microbeams emitted from tiny sources (probably plasma diodes), which can be formed near the observed hot spots.

3

Recent measurements of soft X-ray emission from the DPF-1000U facility

Surała W., Sadowski M. J., Paduch M., Zielinska E., Tomaszewski K.

Nukleonika

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2015

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Vol. 60, No. 2

303--308

EN

Soft X-ray imaging is a very useful diagnostic technique in plasma-focus (PF) experiments. This paper reports results of four experimental sessions which were carried out at the DPF-1000U plasma-focus facility in 2013 and 2014. Over 200 discharges were performed at various experimental conditions. Measurements were taken using two X-ray pinhole cameras with a line of sight perpendicular to the z-axis, at different azimuthal angles (about 20° and 200°), and looking towards the centre of the PF-pinch column. They were equipped with diaphragms 1000 μm or 200–300 μm in diameter and coated with filters of 500 μm Al foil and 10 μm Be foil, respectively. Data on the neutron emission were collected with silver activation counters. For time-resolved measurements the use was made of four PIN diodes equipped with various fi lters and oriented towards the centre of the PF-column, in the direction perpendicular to the electrode axis. The recorded X-ray images revealed that when the additional gas-puff system is activated during the discharge, the stability of the discharge is improved. The data collected in these experiments confi rmed the appearance of a filamentary fi ne structure in the PF discharges. In the past years the formation of such fi laments was observed in many Z-pinch type experiments. Some of the recorded X-ray images have also revealed the appearance of the so-called hot- -spots, i.e. small plasma regions of a very intense X-ray emission. Such a phenomenon was observed before in many PF experiments, e.g. in the MAJA-PF device, but it has not been investigated so far in a large facility such as the DPF-1000U. The time-resolved measurements provided the evidence of a time lapse between the X-ray emission from plasma regions located at different distance from the anode surface. The formation of distinct ‘hot-spots’ in different instants of the DPF-1000U discharge was also observed.

4

Wprowadzenie do zjawisk nieliniowych występujących w strefie kontaktu okładziny ciernej z tarczą hamulcową pojazdów szynowych

Sawczuk W.

Logistyka

|

2015

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nr 3

4310--4316, CD 1

PL

Niezawodność działania układu hamulcowego danego pojazdu uzależniona jest w dużej mierze od współpracy elementów hamulcowych stanowiących parę cierną np. tarcza hamulcowa-okładzina cierna. Niestabilność pracy wynika między innymi z wahania chwilowego współczynnika tarcia, co wpływa na obniżenie sprawności procesu hamowania. W praktyce oznacza to, że podczas hamowania pojazdów występujący zmienny w czasie opór tarcia może być powodem nierównomiernego przebiegu procesu hamowania. Skutki tych zmian zgodnie z pracą [10] mogą objawić się w postaci zmiennego opóźnienia od momentu rozpoczęcia aż do zatrzymania pociągu oraz drganiami przenoszonymi na pojazd. W konsekwencji wpływa to również na pogorszenie komfortu jazdy. Celem artykułu jest wprowadzenie do zagadnień zjawisk nieliniowością występujących w styku okładziny ciernej z tarczą hamulcową w czasie hamowania pojazdów szynowych.

EN

The reliability of the operation of the braking system of the vehicle depends to a large extent on the cooperation of the brake components forming a pair of friction e.g. brake disc-friction pad. Work instability arises by the occurrence of instantaneous changes to the coefficient of friction, which affects the lower efficiency of the braking process. In practice, this means that, during braking the vehicles currently alternative at a time of friction resistance may cause uneven braking process. The effects of these changes in accordance with the work [10] may be revealed in the form of no linear braking delay and vehicle vibrations. As a consequence, it also to the adversely affects on ride comfort. The purpose of the article is an introduction to the issues of nonlinear phenomena of the contact friction pads with disc during braking of the rail vehicles.

5

Foci for Determining the Insensitivity Features of Nanometer RDX: Nanoscale Particle Size and Moderate Thermal Reactivity

Wang Y., Song X., Song D., Zhang J., Song K.

Central European Journal of Energetic Materials

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2015

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Vol. 12, no. 4

799--815

EN

In this paper, the reasons why nanometer RDX showed lower sensitivity than micro RDX is discussed. Herein we supposed two factors affect the sensitivity of nanometer RDX. Firstly, according detonation physics models, a nanometer particle size results in small hot spots and a high critical temperature. These features suggested high safety for nanometer RDX based on the hot spot theory. A further factor is the thermal reactivity of nanometer RDX, which considerably affects the safety of nanometer energetic materials. Employing the Kinetic Compensation Effect, we calculated the kinetic parameters of micro and nanometer RDX. The results indicated that there was no obvious distinction between the activation energies of micro and nanometer RDX, which implies almost the same reactivity of micro and nanometer RDX. Incorporating the results of small hot spots, high critical temperature, and the unchanged reactivity of micro and nanometer RDX, we concluded that nanometer RDX should exhibit low sensitivity as an intrinsic feature.

6

Analitical criteria of homogeneous and heterogeneous detonation of liquid energetic materials

Kaim S.

Materiały Wysokoenergetyczne

|

2013

|

T. 5

5--13

EN

Statistical theory of liquids is used to investigate mechanism of detonation initiation on fronts of flat shock waves in homogeneous liquid and in liquid containing spherical nanopores. We calculated thermodynamic parameters of liquid methane sufficient for shock dissociation of molecules at a front of a shock wave. Calculations of the average single-particle force potential show that at high pressures and temperatures atoms and molecules get emitted from the surface into a nanopore with hyper-thermal speeds. Implosion of spherically symmetric stream of molecules may lead to destruction of the molecules at impact. We explained existence of top and bottom bounds for pressure during detonation initiation in heterogeneous energetic materials. In terms of pair interaction potentials and correlation functions there are formulated criteria for boundary values of thermodynamic parameters which are required for initiation of homogeneous and heterogeneous detonations based on the "hot spot"’ mechanism.

7

Irregular ignition events in TC GDI engines: phenomenology, analysis and engine development

Hirsch A., Kapus P., Philipp H., Winklhofer E.

Silniki Spalinowe

|

2010

|

R. 49, nr 4

23-30

EN

Gasoline engine development has to respond to requirements for fuel efficient and clean combustion. In meeting such targets, the automotive industry has responded with the introduction and continuous improvement of turbocharged gasoline direct injection (TC GDI) combustion systems. Specific challenges to such engines include irregular ignition and combustion events which are rarely met in conventional engines. The paper describes ignition phenomena and mechanisms relevant for the development of such TC GDI engines. Focus then is given to combustion measurement techniques applied for the identification of these spontaneous and riskfull combustion events. As analysis of such ignition events must be done in real, high load multicylinder engine operation, suitable sensors together with measurement and analysis procedures are described. The paper concludes with analysis examples derived from various engine testing situations.

PL

Rozwój silników benzynowych musi podążać za zmieniającymi się wymaganiami dotyczącymi efektywności i czystości spalania. Aby sprostać tym wymaganiom przemysł samochodowy wprowadza ciągłe zmiany i ulepszenia procesów spalania w silnikach benzynowych z wtryskiem bezpośrednim i z turbodoładowaniem. Szczególnym wyzwaniem w konstruowaniu tych silników są zjawiska nieregularnego zapłonu i spalania stukowego rzadko występujące w silnikach konwencjonalnych. Ten artykuł opisuje zjawiska towarzyszące zapłonowi oraz inne mechanizmy istotne z punktu widzenia rozwoju tych silników. Dużo uwagi poświecono technikom pomiaru spalania stosowanym do opisu przypadków niebezpiecznych ze względu na ryzyko niekontrolowanego spalania stukowego. Analiza takich przypadków nieprawidłowego zapłonu musi być dokonana podczas rzeczywistej pracy wielocylindrowego silnika przy dużych obciążeniach. W artykule opisano odpowiednie do tego celu czujniki wraz z metodami pomiaru i analizy danych. W części końcowej artykułu przedstawiono analizę przykładów zaczerpniętych z różnych badań silnikowych.

8

Electric Spark Sensitivity of Nitramines. Part II. A Problem of "Hot Spots"

Zeman S., Pelikán W., Majzlík J., Kočí J.

Central European Journal of Energetic Materials

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2006

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Vol. 3, nr 3

45-51

EN

Attention was focused on the influence of grain size upon the electric spark sensitivity of 1,3,5-trinitro-1,3,5-triazinane (hexogen) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (octogen). Also the dependence of this sensitivity is monitored upon the addition of hard and fine admixtures (crushed glass or diamond dust) to these compounds and sample of ?-HNIW. It was found that this artificial introduction of the said admixtures decreases the electric spark sensitivity of corresponding mixtures because the number of intergrain contact points of the nitramines grains in the volume unit is decreased by implementation of the foreign particles. It was also suggested that dislocations in the crystals should play some role here. It is stated that an impact component absents in relevant electric discharge.

9

Dislocation - Assisted Initiation of Energetic Materials

Armstrong R. W.

Central European Journal of Energetic Materials

|

2005

|

Vol. 2, nr 3

21-37

EN

The role of dislocations in assisting initiation of (explosive) chemical decomposition of energetic materials has connection with the known influences for crystals and polycrystals of dislocations facilitating permanent deformations and phase transformations. X-ray topographic observation of relatively few dislocations in solution-grown crystals relates to the influence of large Burgers (displacement) vectors that are characteristic of molecular crystal bonding. Both model evaluations of the load dependence of cracking at hardness indentations and the derived hardness stress-strain behaviors show that dislocation movement is difficult whether in the indentation strain fields or at the tips of indentation-induced cracks. Thus, energetic crystals are elastically compliant, plastically hard, and relatively brittle [1]. Nevertheless, cracking is shown to be facilitated by the shear stress driven, normally limited, dislocation flow that, on molecular dynamics and dislocation pile-up model bases, is shown to be especially prone to producing localized hot spot heating for explosive initiations. Such model consideration is in agreement with greater dropweight heights being required to initiate smaller crystals. The crystal size effect carries over to more difficult combustion occurring for compaction of smaller crystals. The total results relate to dual advantages of greater strength and reduced mechanical sensitivity accruing for the development of nanocrystal formulations. In consequence, also, several levels of dislocation-assisted modeling are described for initiation mechanisms under shock wave loading conditions.

10

Mantle plumes and dynamics of the Earth interior : towards a new model

Cwojdziński S.

Przegląd Geologiczny

|

2004

|

Vol. 52, nr 8/2

817-826

EN

Seismic tomography provides reconstructions of thermal-density structure of the Earth's mantle as deep as the mantle/core boundary (CMB). For the first time, a direct image of dynamic processes, occurring inside the globe, was obtained. Existing plate-tectonic models of modern geodynamics lead to a number of discrepancies. Most important are: stationary position of mantle plumes as the assumption of the convection process in the Earth's mantle, mantle convection versus data on both its viscosity and the existence of global seismic discontinuities, possibility of horizontal displacements of lithospheric plates above the discontinuous LVZ zone which disappears under deep-seated continental "roots", the model of radially growing distance between mid-oceanic ridges and Africa (also Antarctica), the growing separation between hot spots occur in neighbouring plates with time, geophysical data indicative of considerable input of energy and material from the Earth's core into the mantle, uncompensated by any exchange between the lower and upper mantle. New models (multi-layered convection or a plate-tectonic hybrid convection model) intend to explain tomographic image with taking into consideration geochemical data but with miserable results. The nature of mantle convection still remains controversial. The phenomenon of stationarity of hot spots relative to the accepted plate movements and the absence of evidence indicating deformations of mantle plumes by the convection system are also unclear and controversial. The presented model of the expanding Earth's offers a reasonable solution to these discrepancies and paradoxes.

11

Compression of gas bubble with inertial coating

Włodarczyk E.

Journal of Technical Physics

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2003

|

Vol. 44, no 1

3-17

EN

The compression problem of the polytropic gas bubble coated by the layer of an ideal incompressible liquid has been solved in the closed form. The simple algebraic formulae, which determine the velocity and pressure fields in the liquid layer, as well as the critical (minimal) radius of the maximally compressed bubble, have been derived. The adiabatic and isothermal gas compressions were examined. The time of the compression process was determined. The general solution of the problem was achieved. The solutions, known in the literature of the similar but simplified problems, result from our solution as particular cases.

12

Spatio-temporal decay 'hot spots' of stranded wrack in a Baltic sandy coastal system. Part I. Comparative study of the pattern : 1 type of wrack vs 3 beach sites

Jędrzejczak M. F.

Oceanologia

|

2002

|

No. 44 (4)

491-512

EN

The significance of distance along the beach-dune transect and different moisture conditions as regards the decay of Zostera marina leaf litter was investigated in simple field experiments in three temperate, medium- to fine-quartz-sediment, sandy beaches of the Gulf of Gdansk in Poland. 1800 replicate litterbags of freshly stranded Zostera marina leaves were placed in beach sediments at different strata and levels on each of the beaches. The litterbags were sampled after 5, 10, 50, 100 and 150 days in the field and the remaining material was then dried and weighed. Under similar conditions of sediment composition, salinity and wave inundation, ANOVA tests revealed significant differences in breakdown through time and site. Thus there were some differences in the decay process between the low and high beach. In the former, degradation proceeded rapidly in the initial stages and then stabilised, while in the latter it remained linear throughout the study period. Matter loss in each stratum was also seasonally dependent. This may, however, be more closely linked to successional changes in the chemistry and/or microflora of the beach wrack than to its physical breakdown. Differences between organic matter degradation in the high and low beaches may be explained by differences in the moisture regime and nutrient status, and not by differences in the decay processes themselves. Therefore, two decay centres were found in the beach-dune system: the low beach together with the strandline (wrack consumption 12-21% day-1 in the warm season, and 4-10% day-1 in the cold season) and the dune (active consumption 2-6% day-1 in the warm season only).

13

Sources and concentration of organic pollutants in the Odra river

Zygmunt B., Wolska L., Namieśnik J.

Chemia i Inżynieria Ekologiczna

|

2001

|

Vol. 8, nr 8-9

973-980

EN

The Odra basin includes the areas of the highest environrnental nuisance. Very likely culprits of pollution are industry and also agriculture and forestage. The study was conducted to localise sources of polluting the basin with organic compounds including volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides. They were analysed in water and sediments sampled along Odra and its tributaries. Individual pollutants and total parameters were determined in water and sediment sampils; while toxicity tests were made only for water samples. The studies were conducted in 1997-1998 including post-flood samples. Extensive database was compiled to assess this area pollution. Hot spots were localised and attempts were made to correlate toxicity with concentration of individual compounds and with total parameters.

PL

Przeprowadzono badania nad zlokalizowaniem źródeł zanieczyszczenia Odry i jej dorzecza typowymi zanieczyszczeniami organicznymi obejmującymi wielopierścieniowe węglowodory organiczne, lotne związki organiczne, polichlorowane bifenyle i pestycydy. Zanieczyszczenia te oznaczano w wodzie i osadach dennych pobieranych na całej długości Odry i jej dorzeczu. Przeprowadzono pomiary indywidualnych przedstawicieli wymienionych klas zanieczyszczeń dla próbek wód i osadów dennych. Przeprowadzono także testy toksyczności dla próbek wodnych. Pomiary obejmowały okres 1997-1998, w tym próbki pobrane tuż po powodzi 1997 r. Na podstawie uzyskanych danych oceniono stopień skażenia, zlokalizowano najbardziej niebezpieczne punkty zanieczyszczeń i podjęto próbę skorelowania toksyczności próbek z zawartością zanieczyszczeń organicznych.