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The exhaust gas recirculation (EGR) valve regulates the exhaust gas flow between the engine exhaust manifold and the inlet one. This allows the inlet air to warm up, improving fuel evaporation and reducing the combustion temperature of the charge. Such a valve reduces the number of harmful substances in the exhaust gases. The valve tends to stick when too much sediment builds on the walls of the exhaust system, especially during driving in urban conditions or when leaks in the vacuum or exhaust pipes occur. A faulty valve causes the engine to run unevenly at idle speed and under light loads. The defective EGR valve weakens the inlet manifold capacity, increases combustion, causes clogging of the particulate filter and damage to the lambda probe. Blocked EGR valve may lead to engine immobilization as a result of its computerized control system operations. A model of an EGR valve for a selected diesel engine was developed to determine velocity distribution of the load flowing in it for different values of the degree of valve opening and the volume of deposits on the valve walls. The volume of accumulated carbon deposits on the walls of the EGR valve was measured using a real engine. Based on the recorded mileage of the vehicle, the assumed average speed of the car and the driving style of the driver and the intensity of deposition of carbon particles on the walls was estimated. [ABSTRACT FROM AUTHOR]

Biomass is an alternative and promising source for the sustainable production of energy and commodities such as hydrogen. For this, biomass can be converted into bioethanol through fermentation/hydrolysis that is reliably converted into hydrogen through steam reforming (SRE), and the performance of the most used catalysts for this process (Ni-based) is determined by the support components and preparation methods. In this work, three Ni-based catalysts have been compared for the SRE at 500 °C, steam/ethanol molar ratio of 3 and a low space-time of 0.025 h-1 in a fluidized-bed reactor: The catalysts tested were obtained upon reduction at 850 °C of a NiO/Al2O3 obtained by wetness impregnation (Ni-WI) and two spinel precursors (NiAl2O4 and NiMgAl2O4) prepared by co-precipitation (Ni-S and NiMg-S, respectively). The Ni-S and Ni-WI catalysts have similar performances with high ethanol conversion but unstable H2 yield over time on stream, whereas the NiMg-S catalyst has a higher and more stable H2 yield even with lower ethanol conversion, which proves differences in the prevailing reaction routes for the catalysts. The NiS and Ni-WI catalysts prompt the ethanol dehydration to ethylene (C2H4) on acid sites (which increases ethanol conversion) followed by its decomposition to carbon and H2, which are prevailing routes over SR reactions, thus producing significant amount of carbon deposits, although both carbon and H2 yield decrease suddenly after certain time on stream (TOS) due to deactivation of the C2H4 decomposition reaction. Conversely, the presence of MgO in the support of the NiMg-S catalyst neutralizes the acid sites and favors the ethanol steam reforming and ethanol dehydration to acetaldehyde (C2H4O), that is decomposed into CH4 and CO. An overall significant amount of carbon is also deposited upon NiMg-S catalyst (from CO and CH4 precursors) but it allows a stable behavior of the catalyst due to its filamentous nature. [ABSTRACT FROM AUTHOR]

The innovative system, which was developed for analysis and correction of motor management, is determined for the solution of practical problems concerning the operation of the piston combustion engines. Programming of the ignition curves and fuel maps without relevant feedback, namely, without information obtained from the engine operation, increases the risk of detonation combustion, which can destroy the combustion engine. However, the main application area of this system is the development of an algorithm, which is specified for control of the combustion process based on the HCCI technology (Homogenous Charge Compression Ignition). Nowadays, the functional principle of the HCCI engine is one of the most effective possibilities on how to reach higher operational efficiency of the gasoline engine, that is, closer to the efficiency level of the diesel driving units. [ABSTRACT FROM AUTHOR]

Methane is decomposed to carbon and hydrogen over Raney nickel catalyst in controlled manner in order to deposit carbon; and thereby NiC composite catalysts have been prepared. The catalysts have been analyzed by atomic emission spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The NiC catalysts are comprised of metallic nickel with superficial oxide and carbon. Electron density of Ni in the NiC catalysts is observed to be higher than that in the parent Raney nickel; this indicate partial charge transfer from carbon to nickel in the NiC catalysts. The NiC catalysts exhibite much better performance than the original Raney nickel catalyst in the selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde. They also exhibite stable performance in multiple reaction runs. [ABSTRACT FROM AUTHOR]

One of the most frequently implemented processes in the water treatment technology is filtration through a biosorption bed. The techniques based on biochemical processes involving bacteria result in obtaining high quality of water. There are a number of different materials used as the filler material for biological filters. Carbon deposits are the most popular, due to their high effectiveness. The problem with the use of this process is the leaching of microorganisms from the biofilm and the biological stability of water thus obtained. There is a need to develop quick methods to assess the microbiological quality of this water. Modern techniques for determining the amount of microorganisms, such as flow cytometry and luminometry may be the right tools. The water collected for testing came from the Water Treatment Station located in the Podkarpackie voivodeship. The microbiological tests carried out in the analyzed water samples collected after the filtration process on granular activated carbon. Both traditional culture method and modern techniques used to determine the number of microorganisms (flow cytometry, luminometric ATP assay) demonstrated an increase in the number of microorganisms in the examined waters (in the water after the filtration process and in the water introduced into the water supply network) after the incubation process for 3 and 7 days at 15 and 22°C. [ABSTRACT FROM AUTHOR]

Solid oxide electrochemical cells (SOCs) can store electrical energy in the form of chemical fuels with high efficiency by electrolysis of CO 2 and H 2 O . However, achieving commercially relevant lifetime is hindered by degradation mechanisms such as carbon deposition, which can even destroy the cell especially during electrolysis where carbon formation is electrochemically driven at the electrode-electrolyte interface. Here we used a three-dimensional multiphysics model to simulate a SOC performing CO 2 electrolysis and determine the operating conditions and locations in the porous nickel-based electrodes where carbon deposition is expected based on local conditions (gas composition, temperature and overpotential) crossing local thermodynamic thresholds. It is found that CO/ CO 2 gas diffusion gradients and cooling from the endothermic electrolysis reaction are important driving forces for carbon deposition to occur locally when it is not expected based on the outlet CO concentration. Furthermore, correlation with a set of experimentally determined threshold operating points indicates that carbon deposition occurs primarily by the Boudouard reaction rather than by direct electrochemical reduction of CO or CO 2 to carbon for the studied cell type. Variation of fuel electrode porosity and thickness shows that these methods of reducing gas diffusion limitations widen the operating window that avoids carbon deposition. [ABSTRACT FROM AUTHOR]

In this paper, the fractal dimension of carbon deposits from coke oven chamber is defined. The surface of the carbon deposit has been examined using a scanning electron microscopy. The images of surfaces of the carbon deposit are given. The analysis and measurements of fractal clusters images have been presented. The data on the actual density of the deposit and its electrical resistance is given. The sphere-like clusters of the fractal structures are layered bodies. The fractal dimension D of the carbon deposit that is formed in the cells of coke ovens is 2.925. [ABSTRACT FROM AUTHOR]

While dual fuel low temperature combustion (LTC) has been studied before, a detailed second law analysis of dual fuel LTC is not yet available in the open literature. To address this gap, a previously validated, closed-cycle, multi-zone, simulation of diesel-natural gas dual fuel LTC was used to perform a second law analysis. For the present study, a 2.4-l single-cylinder research engine operating at a nominal load of 6 bar BMEP and 1700 rpm was used. Zone-wise thermodynamic irreversibilities as well as total cumulative entropy generated and lost available work over the closed cycle were quantified. Subsequently, two convenient second-law parameters were defined: (1) the “lost available indicated mean effective pressure” (LAIMEP), which can be interpreted as an engine-size-normalized measure of available work that is lost due to thermodynamic irreversibilities (analogous to the relationship between indicated mean effective pressure and indicated work); (2) fuel conversion irreversibility (FCI), which is defined as the ratio of lost available work to total fuel chemical energy input. Finally, parametric studies were performed to quantify the effects of diesel start of injection, intake manifold temperature, and intake boost pressure on LAIMEP and FCI. The results show that significant entropy generation occurred in the flame zone (52–61 percent) and the burned zone (31–39 percent) while packets account for less than 6 percent of the overall irreversibilities. Parametric studies showed LAIMEPs in the range of 645–768 kPa and FCIs in the range of 32.8–39.2 percent at different engine operating conditions. Although the present study focused on dual fuel LTC, the conceptual definitions of LAIMEP and FCI are generally applicable for comparing the thermodynamic irreversibilities of IC engines of any size and operating on any combustion strategy. [ABSTRACT FROM AUTHOR]

Water table depth (WTD) effects on net ecosystem CO2 exchange of boreal peatlands are largely mediated by hydrological effects on peat biogeochemistry, and eco-physiology of peatland vegetation. Lack of representation of these effects in carbon models currently limits our predictive capacity for changes in boreal peatland carbon deposits under future drier and warmer climates. We therefore tested whether the effects of WTD variation on net ecosystem CO2 exchange of a Western Canadian boreal fen peatland could be modelled through a process-level coupling of a prognostic WTD dynamic, which arises from equilibrium between vertical and lateral water fluxes, with oxygen transport, which controls energy yields from microbial and root oxidation-reduction reactions, and vascular and non-vascular plant water relations in an ecosystem model ecosys. Ecosys successfully simulated a May-October WTD drawdown by ~ 0.25 m measured in the fen from 2004 to 2008, which was attributed to reduced precipitation relative to evapotranspiration, and reduced lateral recharge relative to discharge. This WTD drawdown hastened oxygen transport to microbial and root surfaces, enabling greater microbial and root energy yields, and peat and litter decomposition, which raised modelled ecosystem respiration (Re) by ~ 0.26 Āmol CO2 m-2 s-1 per 0.1 m of WTD drawdown. It also augmented nutrient mineralization, and hence root nutrient availability and uptake, which resulted in improved leaf nutrient (nitrogen) status that facilitated carboxylation, and raised modelled vascular gross primary productivity (GPP). This increase in modelled vascular GPP exceeded declines in modelled non-vascular (moss) GPP due to greater shading from increased vascular plant growth, and moss drying from near surface peat desiccation, thereby causing a net increase in modelled growing season GPP by ~ 0.39 Āmol CO2 m-2 s-1 per 0.1 m of WTD drawdown. Similar increases in GPP and Re left no significant WTD effects on modelled variations of net ecosystem productivity (NEP). These modelled trends were corroborated against eddy covariance hourly net CO2 fluxes (modelled vs. measured: R2 ~ 0.8, slopes ~ 1 ± 0.1, intercepts ~ 0.05 Āmol m-2 s-1), and against other automated chamber, biometric, and laboratory measurements. Modelled drainage as an analog for climate change showed that this boreal peatland would switch from a large carbon sink (NEP ~ 160 g C m-2 yr-1) to carbon neutrality (NEP ~ 10 g C m-2 yr-1) should water table deepened by a further ~ 0.5 m. Therefore, representing interactions among hydrology, biogeochemistry and plant physiological ecology on carbon, water, and nutrient cycling in global carbon models would improve our predictive capacity for changes in boreal peatland carbon sequestration under changing climates. [ABSTRACT FROM AUTHOR]

Inland navigation is of increasing economic and ecological interest, however its contribution to environmental quality is hardly known. We hypothesized that i) inland navigation emits considerable amounts of soot-Black Carbon (BC) as a product of incomplete combustion of diesel fuel, which is then deposited on soils along river valleys, that ii) improvement of fuel quality by sulfur reduction in 2011 decreased BC inputs to soil, and that iii) this provides a tracer for the spatial impact of inland navigation emissions. The spatial and temporal patterns of soil BC deposits from inland navigation were investigated yearly (2010–2013) working within transects perpendicular to the rivers Rhine, Moselle and Ahr, Germany (the Ahr Valley is free of shipping and served as a reference). In rural areas at inland waterways navigation likely represented the dominant BC emitter. Topsoils (0–10 cm depth) were sampled in vineyards. Their BC content and composition was determined via oxidation of bulk soil organic matter to benzene polycarboxylic acids (BPCAs). The highly trafficked Rhine Valley yielded only little more BC (64.7 ± 12 g BC kg −1 soil organic carbon (SOC) compared to 51.7 ± 9 at the Moselle, and 53.6 ± 6 at the reference Ahr Valley). At both inland waterways soil BC increased towards the river, following the simulated dispersal of ship-derived BC using a Lagrangian model. In the course of ship fuel regulation, soil BC deposits at the Rhine and Moselle waterways decreased significantly from 70.2 ± 3.2 to 47.9 ± 1.1 and 57.6 ± 1.3 to 41.7 ± 0.9 g BC kg −1 SOC within 3 years. Even more pronounced was the change in BC composition, i.e., the ratio of pentacarboxylated to mellitic acid increased from 0.75 to 1.3 (Rhine) and 1 to 1.4 (Moselle) during this time span. From this we calculated that ∼30% less BC was deposited by inland navigation likely due to reduced BC emissions after sulfur regulation in ship diesel. [ABSTRACT FROM AUTHOR]

The emissions from the Compression ignition (CI) engines introduce toxicity to the atmosphere. The undesirable carbon deposits from these engines are realized in the nearby static or dynamic systems such as vehicles, inhabitants, etc. The objective of this research work is to improve the performance and emission characteristics of a diesel engine in the modified re-entrant combustion chamber using a diesel and Jatropha methyl ester blend (J20) at three different injection pressures. From the literature, it is revealed that the shape of the combustion chamber and the fuel injection pressure have an impact on the performance and emission parameters of the CI engine. In this work, a re-entrant combustion chamber with three different fuel injection pressures (200, 220 and 240 bars) has been used in the place of the conventional hemispherical combustion chamber for diesel and J20. From the experimental results, it is found that the re-entrant chamber improves the brake thermal efficiency of diesel and J20 in all the tested conditions. It is also found that the 20% blend of Jatropha methyl ester showed 4% improvement in the brake thermal efficiency in the re-entrant chamber at the maximum injection pressure. Environmental safety directly relates to the reduction in the undesirable effects on both living and non-living things. Currently environmental pollution is of major concern. Even with the stringent emission norms new methods are required to reduce the harmful effects from automobiles. The toxicity of carbon monoxide (CO) is well known. In the re-entrant combustion chamber, the amount of CO emission is reduced by 26% when compared with the conventional fuel operation of the engine. Moreover, the amount of smoke is reduced by 24% and hydrocarbons (HC) emission by 24%. Thus, the modified re-entrant combustion chamber reduces harmful pollutants such as unburned HC and CO as well as toxic smoke emissions. [ABSTRACT FROM AUTHOR]

Burning off is the main method of carbon deposit removal from coke oven chambers. The heterogeneous reaction must be considered when the air blowing eliminates wall polycarbonate in the coke oven. In the three-dimensional problem of the burning off in the coke oven, the turbulent flow is induced by the interaction of the forced convection form the air inlet and natural convection from the high temperatures on the wall. This paper intends to show that the models can be generated by the solution of equations of conservation of mass, energy and spices in the boundary layer while lumping at the surface all the intraparticle effects. In order to understand the Sorect effect, there were three cases comparison. From the results, the Sorect effect is not clear, and P1 model has highly nonphysical behavior together with numerical instabilities inherent to the model. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel anodic alumina monolith was applied for DME hydrolysis. [•] The product distributions on different acidic catalysts were studied. [•] The novel monolith has an excellent resistance to carbon deposition. [ABSTRACT FROM AUTHOR]

Abstract: In order to research the failure mechanism of Solid Oxide Fuel Cell (SOFC), an unsteady state two-dimensional model that considers the carbon deposition is presented. Navier–Stokes (N–S) equations, heat transfer equation, mass transfer equation, electron and ion transport equation are solved by COMSOL 3.5. In the numerical model, with the operating temperature at 800°C, gas phase chemical reaction kinetics is used to predict the carbon deposition molar mass. Furthermore, the unsteady state variation of anodic porosity and the electrical conductivity that caused by carbon deposition is taken into account. From the numerical results, it can be found that the effect of the variation of anodic porosity on SOFC electronic performance is about 7%. Therefore, it is necessary to consider the variation of anodic porosity when come up against carbon deposition problems of SOFC. The increased inlet water/methane ratio could eliminate carbon deposition, but the current density would decline dramatically. [Copyright &y& Elsevier]

Carbonaceous deposits in automotive engines are the major problems associated with oil aging. Efficient detergents and dispersants have been used for several decades to solve this problem particularly in petroleum oils. But future lubricants and new engine hardware require development of new nontoxic detergent/dispersant additive technologies. Environmental concerns limit the formulation of the future lubricants. It requires not only the base oil to be ecofriendly but the additives also. In the present work, some of the potential ecofriendly chemical's molecules were identified. Specific detergents applications along with effects of chemical modifications were evaluated by Blotters Spot and Panel Coker Tests. Among the studied compounds, the PIB (polyisobutylene) succinimides are showing promising results at lower temperature, while at higher temperature piperazine derivatives citrate and oleate have the best potential to be develop as ecofriendly detergent/dispersant additives. [ABSTRACT FROM AUTHOR]

A multi-pulse injection strategy for premixed charge compression ignition (PCCI) combustion was investigated in a four-valve, direct-injection diesel engine by a computational fluid dynamics (CFD) simulation using KIVA-3V code coupled with detailed chemistry. The effects of fuel splitting proportion, injection timing, spray angles, and injection velocity were examined. The mixing process and formation of soot and nitrogen oxide (NOx) emissions were investigated as the focus of the research. The results show that the fuel splitting proportion and the injection timing impacted the combustion and emissions significantly due to the considerable changes of the mixing process and fuel distribution in the cylinder. While the spray, inclusion angle and injection velocity at the injector exit, can be adjusted to improve mixing, combustion and emissions, appropriate injection timing and fuel splitting proportion must be jointly considered for optimum combustion performance. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to evaluate the cylinder head carbon deposit from diesel engine fuelled by four samples of diesel fuel emulsions containing 0%; 5%; 10% and 15% vol. water and 20% Palm Oil Methyl Ester (POME) were subjected to thermogravimetric analysis (TGA/DSC) in air medium. The deposit build up processes were performed on a single-cylinder direct-injection diesel engine for period of 25h for each set of test fuel under constant speed 2500rpm. The TGA system was used and then correlated with elemental analysis as well as infrared spectra for microscopic observations. It has been found that, as the water increases in fuel, less aromatic and less reactive of deposits would be formed. Therefore, such method of analyses can be used as an indicator to verify the stability of carbon deposit inside the combustion chamber that could substantiate the applicability of a particular fuel to be accepted. [Copyright &y& Elsevier]

Abstract: Combustion chamber deposit has adverse effects on the performance and operation of various combustion devices, such as boilers, furnaces and engines. To study deposits by actually running combustion device for a long time to gather the deposit is very time and money consuming. In this investigation, we developed a deposit-forming technique by using a spray burner with water-cooled stagnation plate. The deposit could form on the stagnation plate readily and thus enabled us to investigate the formation of deposit under different operating conditions. We focused on the effect of the cooling water temperature and F/A ratio on the formation of deposit. In this paper, the temperature profile of the stagnation flow was measured for different F/A ratios to provide basic understanding of the thermal characteristics of two-phase flow burners. Then, the weight, formation area and H/C ratio of deposits were analyzed. It was found that the growth of deposit was faster for a lower cooling water temperature, i.e. lower surface temperature. The weight of deposit basically increased with time. H/C ratio showed a tendency to decline with the increase of F/A ratio. We also performed deposit formation tests on a CFR engine with 4 different fuel compositions. There was a qualitative correlation on weight of deposit between stagnation plate and CFR engine test. This study presents a simple experimental modeling on deposit formation. However, there are still some parameters relative to real engine conditions, such as pressure, turbulence to be considered in near future. [Copyright &y& Elsevier]

The problems of implementation of liquefied petroleum gas (LPG) supply systems are related with the fact that they are alternative systems used in engines constructed and optimized for work with other kinds of fuel. So assemblers of the systems have to evaluate power losses and at the same time ecological requirements. The experiment is devoted to the analysis of gas composition of engines working at different modes in order to specify the particularity of LPG system tuning and to obtain data for the evaluation of environmental pollution by numerical car dynamics models. It is estimated that the algorithms of current LPG systems balance between ecological requirements and optimization of external characteristics of engines, and the gas systems are characterized by a great inertia. Also, it is determined that more precise tuning algorithms must be constructed, and more tuning points and tuning, when an engine works in standard modes, must be foreseen. [ABSTRACT FROM AUTHOR]

CO2 reforming of methane was investigated with regard to carbon deposition on 4.5 wt% NiO/SiO2 catalyst at 1023 K, 1 atm and a CH4/CO2 ratio of 1.0 employing micro-fluidised- and fixed-bed reactors. A higher catalytic activity (by 20%) was observed in the initial stage (0.5 h) of the fluidised-bed reforming which may be attributed to lesser deactivation of the catalyst compared to fixed-bed operation. Only a limited amount of carbon was deposited in a period of 11 h on stream. In the case of the fixed-bed reactor, a much larger amount of carbon was found on the spent catalyst, particularly, when sampled from the bottom of the bed. TPO results suggest that carbon deposits on the catalyst samples from the fluidised-bed as well as the top of the fixed-bed are rather small and of similar nature. The carbon deposited at the bottom of the fixed-bed reactor contained two distinct species according to XPS results (corresponding to C–O and C–C bonds). [Copyright &y& Elsevier]