The effect of combustion chamber geometry layout on combustion and emission

In this paper some results concerning the combined effect of the fumble flow and combustion chamber geometry layout variations on flame front shape and its propagation through homogenous mixture of isooctane and air are presented Spatial distributions of NO in different combustion chamber geometries are presented as well. The basic combustion chamber geometry layout considered consists of the flat head with two vertical valves and a cylindrical bowl subjected to variations of depth and squish area. All results presented were obtained by dint of multidimensional modeling of reactive flows in arbitrary geometry with moving objects and boundaries with modified KIVA3 and KIVA3 V source codes. Two additional computer codes were applied to generate boundary conditions for KIVA3 V calculations with moving valves. The AVL TYCON code was used for the calculation of valve lift profiles, and A VL BOOST code was used for the calculation of relevant data set in the valve regions. Different combustion chamber geometry layouts generate different levels of squish, and the combustion effects in essence depend on the interaction of that flow with tumble. It was found that for particular combustion chamber shapes with different diameter/depth aspect ratios entirely different flame front shapes and propagation velocities were encountered primarily due to variations of fluid flow patterns in the vicinity of top dead center

Aerosol-assisted processing of hierarchically organised TiO2 nanoparticles

Hierarchically assembled TiO2 nanoparticles into larger spherical ones were obtained using aerosol-assisted processing method. Unagglomerated particles with the mean size of 440 nm were obtained from colloidal solution of TiO2 nanoparticles (~4.5 nm) using ultrasonic spray pyrolysis at 550°C. Their morphological complexity and structural polymorphism were investigated by using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED) analysis. Pronounced evolution of nanocrystalline TiO2(B) phase assembled together with the anatase building units (sized ~15 nm) in uniform submicrometric particles implicate their feasibility to be used in dye-sensitised solar cells and lithium ion batteries

Some Subtleties Concerning Fluid Flow and Turbulence Modeling in 4-Valve Engines

In this paper some results concerning the structure and evolution of fluid flow pattern during induction and compression in 4- valve engines with tilted valves were presented. Results were obtained by dint of multidimensional modeling of non-reactive flows in arbitrary geometry with moving boundaries. During induction fluid flow pattern was characterized with organized tumble motion followed by small but clearly legible deterioration in the vicinity of the bottom dead center. During compression the fluid flow pattern is entirely three-dimensional and fully controlled by vortex motion located in the central part of the chamber. In order to annihilate negative effects of tumble deterioration and to enhance swirling motion one of the intake valves was deactivated. Some positive and negative effects of such attempt were elucidated. The effect of turbulence model alteration in the case of excessive macro flows was tackled as well. Namely, some results obtained with eddy-viscosity model i. e. standard k-epsilon model were compared with results obtained with k-xi-f model of turbulence in domain of 4-valve engine in-cylinder flow. Some interesting results emerged rendering impetus for further quest in the near future

Some energetic and ecological aspects of different city bus drive systems

This paper presents the analysis and comparison of energy and environmental properties of various city bus systems: diesel and compressed natural gas internal combustion engines, trolleybus, and battery electric bus. It is based on experimental research on fuel and energy consumption of city buses with aforementioned propulsion systems carried out under similar driving conditions - on the same city bus lines in Belgrade and Novi Sad, and on evaluation of energy efficiency and CO2 emission of real electricity production in Serbia. In this way, "tank-to-wheel" and "well-to-wheel" energy consumption and CO2 emissions of considered bus driving systems have been evaluated and compared. The results show all complexity of the matter since benefits of application of different systems largely depends on bus exploitation conditions and even more of the conditions of electric energy production. The compressed natural gas internal combustion engine compared to the Diesel engine provides obviously benefit in harmful gas emissions. However, CO2 emissions are on a similar level, while energy efficiency is even less. Electric propulsion systems provide undoubtedly benefit in energy consumption, harmful gases and CO2 emissions if tank-to-wheel conditions are considered, but well-to-wheel characteristics strongly depend on the condition of electric energy production. © 2018 Society of Thermal Engineers of Serbia

Glassy carbon and boron doped glassy carbon electrodes for voltammetric determination of linuron herbicide in the selected samples

In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000A degrees C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E (p) ) of linuron oxidation in 0.1 mol dm(-3) H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm(-3) H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005-0.1 A mu mol cm(-3)) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds

The Effect of Bowl-In-Piston Geometry Layout on Fluid Flow Pattern

In this paper some results concerning the evolution of 3-D fluid flow pattern through all four strokes in combustion chambers with entirely different bowl-in-piston geometry layouts ranging from omega to simple cylinder were presented. All combustion chambers i. e. those with omega bowls, with different profiles, and those with cylinder bowls, with different squish area ranging from 44% to 62%, were with flat head, vertical valves, and identical elevation of intake and exhaust ports. A bunch of results emerged by dint of multidimensional modeling of non-reactive fluid flow in arbitrary geometry with moving objects and boundaries. The fluid flow pattern during induction and compression in all cases was extremely complicated and entirely 3-D. It should be noted that significant differences due to geometry of the bowl were encountered only in the vicinity of top dead centre. Namely, in the case of omega bowl all three types of organized macro flows were observed while in the case of cylinder bowl no circumferential velocity was registered at all. On the contrary, in the case of cylinder bowl some interesting results concerning reverse tumble and its center of rotation shifting from exhaust valve zone to intake valve zone during induction stroke and vice-verse from intake valve zone to exhaust valve zone during compression were observed while in the case of omega bowl no such a displacement was legible. During expansion the fluid flow pattern is fully controlled by piston motion and during exhaust it is mainly 1-D, except in the close proximity of exhaust valve. For that reason it is not affected by the geometry of the bowl

The Possibilities for Measurement and Characterization of Diesel Engine Fine Particles - a Review

This review paper considers possible instrumentation for diesel engine fine particles exhaust emission evaluation. The modern diesel engines have extremely low particles emission almost at the level of measurement error of existing gravimetric measurement method. Since coarse particles are eliminated by new engine technologies, fine particles, with very negative effects on human health, dominate in the emission of current diesel engine. Therefore, it is necessary not only to measure mass of emitted particles but also to investigate other important particle characteristics as: particles number, particle size, particle number and mass distribution, particle active surface, particle composition, etc. Therefore, existing measurement technologies used in aerosol science can be used also to study diesel engine particles properties. This most common instrumentation in aerosol technique is shortly reviewed in the paper with special attention on candidate instruments included in EU program on portable emissions measurement systems

Hydroxyapatite nano particles doped with Gd3+, Yb3+/Tm3+ and Eu3+ as lumino-magnetic multimodal contrast agents

Hydroxyapatite (HAp) has been widely used as bone reconstruction materials due to their similarity to bone tissue. The improvement of HAp properties was achieved by doping its crystal lattice with different ions. Lanthanides, i.e. Rare Earth Elements (RE) are also suitable for doping HAp. The aim of the presented research was to investigate the possibility of creating lumino-magnetic particles of HAp doped with gadolinium (Gd3+) ions and co-doped with ytterbium/thulium (Yb3+/Tm3+) or europium (Eu3+) ions for potential use in multimodal imaging (MI). Pure HAp (Ca5(PO4)3(OH)), magnetic HAp:Gd (Ca4.85Gd0.15(PO4)3(OH)), and lumino-magnetic HAp:Gd/Yb/Tm (Ca4.85Gd0.03Yb0.1Tm0.02(PO4)3(OH)) and HAp:Gd/Eu (Ca4.94Gd0.02Eu0.04(PO4)3(OH)) particles were synthesized using emulsification process and hydrothermal processing. All synthesized particles had an elongated shape and exhibited a paramagnetic behavior. Reduction of the unit cell volume as a result of replacement of Ca2+ ions by ions with a smaller ionic radius (Gd3+, Yb3+, Tm3+, Eu3+) confirmed by using XRD and Rietveld refined plots. The energy band gap values of the synthesized samples range from 4.93 to 3.18 eV and decrease in the following order: HAp:Gd >HAp>HAp:Gd/Eu>HAp:Gd/Yb/Tm. The results of photoluminescence emission spectra of HAp:Gd/Yb/Tm and HAp:Gd/Eu particles showed characteristic transitions of Tm3+ and Eu3+, respectively

Особенности функционирования жидкокристаллических ячеек с введенными наночастицами CoFe2O4

The first experimental results on the functioning of liquid crystal cells doped with CoFe2O4 nanoparticles are presented. Transmission spectra in the visible and near-infrared range, dynamic parameters of the Fredericks effect, refractive characteristics, as well as wetting angles of the mesophase sensitized surfaces have been obtained. The measured surfaces were the K8 Crown glass, the conductive ITO and the ITO treated with a surface electromagnetic wave. The experiment was performed in order to establish the prospect of using such reliefs as a novel liquid crystal composite orientator sensitized with CoFe2O4 nanoparticles. A color change of the liquid crystal matrix, its refractive coefficients alterations, and the variation of inclination angle of the sensitized liquid crystal droplets on the considered reliefs were established. The time reaction parameters and the medium relaxation parameters were measured. It was proposed that the liquid crystal composition is a kind of an immersion medium that preserves properties of the introduced nanoparticles, which expands their application scope in optoelectronics and biomedicine.В работе представлены результаты первых экспериментов по функционированию жидкокристаллических ячеек с введенными в мезофазу наночастицами CoFe2O4. Измерены спектры пропускания в видимом и ближнем ИК-диапазоне, динамические параметры по эффекту Фредерикса, рефрактивные характеристики, а также углы смачивания сенсибилизированной мезофазой поверхностей на основе стекла: Крон К8, проводящего покрытия ITO и ITO, обработанного поверхностной электромагнитной волной, – для перспективы использования такового рельефа в качестве ориентанта новой жидкокристаллической среды. Установлено изменение цвета жидкокристаллической матрицы, ее рефрактивных коэффициентов и угла наклона капель сенсибилизированного жидкого кристалла на рассмотренных рельефах; измерены временны́ е параметры реакции и релаксации среды. Предложено, что жидкокристаллическая композиция является своего рода иммерсионной средой, сохраняющей свойства введенных наночастиц, что расширяет области их применения в оптоэлектронике и биомедицине

Singlet oxygen generation by higher fullerene-based colloids

In this paper, the results of the synthesis and characterization of higher fullerene-based colloids is presented. The generation of singlet oxygen (1)O2 ((1)Delta g) by fullerenc water-based colloids (nC60, nC70 and nC84) was investigated. It was found by electron paramagnetic resonance spectroscopy that the generation of singlet oxygen was the highest by the nC84 colloid. The amplitude of the electron paramagnetic resonance (EPR) signal was two orders of magnitude higher than the amplitude of the EPR signals which originated from nC60 and nC70. The surface morphology and the structure of the particles of the water-based colloids were investigated by atomic force microscopy (AFM). The AFM study showed that the average size of the nC60, nC70 and nC84 were 200, 80 and 70 nm, respectively. In addition, the particle size distribution of the nC60, nC70 and nC84 colloids was determined by dynamic light scattering (DLS) measurements