Effect of waste cooking-oil biodiesel on performance and exhaust emissions of a diesel engine

The ever increase in global energy demand, consumption of depletable fossil fuels, exhaust emissions and global warming, all these led to search about alternative fuels. Biodiesel was produced from waste cooking-oil by transesterification process. Blends of waste cooking-oil biodiesel and diesel oil were prepared in volume percentages of 10, 20 and 30% as B10, B20 and B30. Biodiesel blends have ASTM standards of physical and chemical characterization near to diesel fuel. Diesel engine performance and exhaust emissions were studied experimentally for burning waste cooking-oil blend with diesel fuel. This experimental was applied on a diesel engine at different engine loads from zero to full load. Thermal efficiencies for waste cooking-oil biodiesel blends were lower than diesel oil. Specific fuel consumptions of biodieselblends were higher than diesel fuel. Higher exhaust gas temperatures were recorded for biodiesel blends compared to diesel oil. CO₂ emissions for waste cooking-oil biodiesel blends were higher than diesel oil. CO, smoke opacity and HC emissions for biodiesel blends were lower than diesel fuel. NO_x emissions for biodiesel blends were higher than diesel fuel.     

Effect of biodiesel fuels on diesel engine emissions

Energy production is heavily dependent on fossil fuels that are not only diminishing, but also are considered the main cause of harmful emissions and global warming. Therefore using vegetable oils such as Jatropha, palm, algae and waste cooking oils as alternative fuels in diesel engines has drawn a great attention. Biodiesel from Jatropha, palm, algae and waste cooking oils has been produced using the transesterification process. Biodiesel from different feedstock is mixed with diesel oil in different proportions e.g. B10 and B20. Biodiesel physical and chemical properties are measured according to ASTM standards. A “single cylinder diesel engine” is employed as the test engine in the present work. Exhaust emissions such as CO, CO₂, NO_x, HC, and smoke are measured and compared with diesel oil. CO, HC, CO₂ and smoke emissions are lower for biodiesel mixtures B10 and B20 (Jatropha, algae and palm) compared “to diesel fuel”. CO₂ emissions from biodiesel blends B10 and B20 produced from waste cooking oil are higher compared to diesel fuel. NO_X emissions from all biodiesel mixtures B10 and B20 increases than diesel fuel for all biodiesel blend B10 and B20.     

操作变量对大型浆态床反应器流体力学特性的影响

研究了系统压力、表观气速和固体颗粒体积分数对浆态床反应器气含率、气泡直径及气液接触面积的影响 ,通过试验得出了气含率和操作变量之间的统计关联式 ,给出了在湍流条件下浆态床反应器中气含率和气体动量之间的关系     

α-Fe2O3 /(PVA + PEG) Nanocomposite films; synthesis,optical, and dielectric characterizations

Hematite (α-Fe₂O₃) nanorods with an average diameter of 40 nm were prepared using a template-free sol–gel method. These nanorods then mixed with polyvinyl alcohol (PVA)/polyethylene glycol (PEG) blend at concentrations of 0.0, 0.5, and 1.0 wt.%. The transmittance percentage (T%) of the films showed a decrease from 80.26 to 33.24 %. The direct optical band gap also decreased from 5.28 to 4.83 eV whereas the refractive index significantly increased with increasing the hematite content. The dielectric measurements were performed in the temperature range 303–413 K and frequency range 30 kHz–3.0 MHz. According to the temperature dependence of the dielectric constant (ε’), α _a -relaxation peaks observed in all films and assigned to the micro-Brownian motion of the polymer blend chains. The behavior of the ac conductivity, σ _ac (f), of the nanocomposite films indicated that the homogenous distribution of α-Fe₂O₃ nanorods allows the formation of conductive three-dimensional networks throughout the nanocomposite film. Also, indicated that the correlated barrier hopping is the most suitable conduction mechanism.     

The effect of different bonding protocols on the repair microshear bond strength of water-stored CAD/CAM resin composite

This study evaluated the repair microshear bond strength (μSBS) of water stored CAD/CAM resin composite under eight different surface treatments using a silane-containing universal adhesive in etch-and-rinse and self-etching modes. In total, 48 CAD/CAM resin composite slices were prepared from Lava Ultimate CAD/CAM blocks and stored in water for 6 months. The slices were assigned into 8 main groups, according to surface treatments (no treatment, no-treatment/silane, surface grinding, surface grinding/silane, sandblasting, sandblasting/silane, silica coating and silica coating/silane). Each main group was divided according to the universal adhesive application mode (either the etch-and-rinse mode or the self-etch mode). Each slice received 6 resin composite micro-cylinders (0.8 × 1 mm). Micro-shear bond strength was run at 0.5 mm/min crosshead speed until failure. Treated surfaces were examined using SEM. Bond strength data were statistically analyzed using Two-Way ANOVA/Tukey HSD post hoc test. Only ‘surface treatment’ significantly affected the repair μSBS (p ? 0.001). Parameters ‘Adhesive application mode’ and ‘surface treatment × adhesive mode’ showed no significant effect on μSBS (p = 0.458 and p = 0.286 respectively). Regardless of the adhesive application mode, silica coating showed the highest μSBS (21.6 ± 6.8 MPa), while sandblasting/silane showed the lowest μSBS (13.0 ± 6.1 MPa). Regardless of adhesive application mode, the use of silica coating to treat the water-stored CAD/CAM resin composite surfaces is crucial to improve the repair bond strength.     

Effect of mechanical and electrical activation on the combustion synthesis of Al3Ti

Titanium aluminides have attracted immense interest as lightweight intermetallic compounds that possess good high-temperature mechanical and corrosion properties. In the present work, titanium aluminides (Al₃Ti) have been reactively processed from elemental powder using a combined mechanical and electrical activation approach. The effect of mechanical activation and electric current intensity on the ignition and phase development is discussed. Ignition was not possible when powders were milled for a short time, while prolonged milling resulted in mechanical activation that promoted a self-propagating-type reaction. The time to engulfment of the compact with the reaction wave was found to decrease with an increase in current intensity. A secondary reaction occurred at the higher current intensity, which in turn increased the product homogeneity.     

A novel approach via combination of electrospinning and FDM for tri-leaflet heart valve scaffold fabrication

In this paper, a novel combination method of electrospinning and rapid prototyping (RP) fused deposition modeling (FDM) is proposed for the fabrication of a tissue engineering heart valve (TEHV) scaffold. The scaffold preparation consisted of two steps: tri-leaflet scaffold fabrication and heart valve ring fabrication. With the purpose of mimicking the anisotropic mechanical properties of the natural heart valve leaflet, electrospun thermoplastic polyurethane (ES-TPU) was introduced as the tri-leaflet scaffold material. ES-TPU scaffolds can be fabricated to have a well-aligned fiber network, which is important for applications involving mechanically anisotropic soft tissues. We developed ES-TPU scaffolds as heart valve leaflet materials under variable speed conditions and measured fiber alignment by fast Fourier transform (FFT). By using FFT to assign relative alignment values to an electrospun matrix, it is possible to systematically evaluate how different processing variables affect the structure and material properties of a scaffold. TPU was suspended at certain concentrations and electrospun from 1,1,1,3,3,3-hexafluoro-2-propanol onto rotating mandrels (200–3000 rpm). The scaffold morphological property and mechanical anisotropic property are discussed in the paper as a function of fiber diameter and mandrel RPM. The induction of varying degrees of anisotropy imparted distinctive material properties to the electrospun scaffolds. A dynamic optimum design of the heart valve ring graft was constructed by FDM. Fabrication of a 3D heart valve ring was constructed using pro-engineer based on optimum hemodynamic analysis and was converted to an STL file format. The model was then created from PCL which was sewed and glued with electrospun nanofibrous leaflets. This proposed method was proven as a promising fabrication process in fabricating a specially designed graft with the correct physical and mechanical properties.     

A soft tissue adhesive based on aldehyde-sodium alginate and amino-carboxymethyl chitosan preparation through the Schiff reaction

Sodium alginate and carboxymethyl chitosan have been extensively applied in tissue engineering and other relative fields due to their low price and excellent biocompatibility. In this paper, we oxidized sodium alginate with sodium periodate to convert 1,2-hydroxyl groups into aldehyde groups to get aldehyde-sodium alginate (ASA). Carboxymethyl chitosan was modified with ethylenediamine (ED) in the presence of water-soluble N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) to introduce additional amino groups to get amino-carboxymethyl chitosan (A-CS). Upon mixing the A-SA and A-CS aqueous solutions together, a gel rapidly formed based on the Schiff’s base reaction between aldehyde groups in A-SA and amino groups in A-CS. FTIR analysis confirmed the characteristic peak of Schiff’s base group in the hydrogel. It was confirmed that the gelation time be dependent on the aldehyde group content in A-SA and amino group content in A-CS. The fasted hydrogel formation takes place within 10 min. The data of bonding strength and cytotoxicity measurement also showed that the hydrogel had good adhesion and biocompatibility. All these results support that this gel has the potential as soft tissue adhesive.     

Effect of carbon nanotube (CNT) content on the mechanical properties of CNT-reinforced aluminium composites

The interest in carbon nanotubes (CNTs) as reinforcements for aluminium (Al) has been growing considerably. Efforts have been largely focused on investigating their contribution to the enhancement of the mechanical performance of the composites. The uniform dispersion of CNTs in the Al matrix has been identified as being critical to the pursuit of enhanced properties. Ball milling as a mechanical dispersion technique has proved its potential. In this work, we use ball milling to disperse up to 5 wt.% CNT in an Al matrix. The effect of CNT content on the mechanical properties of the composites was investigated. Cold compaction and hot extrusion were used to consolidate the ball-milled Al–CNT mixtures. Enhancements of up to 50% in tensile strength and 23% in stiffness compared to pure aluminium were observed. Some carbide formation was observed in the composite containing 5 wt.% CNT. In spite of the observed overall reinforcing effect, the large aspect ratio CNTs used in the present study were difficult to disperse at CNT wt.% greater than 2, and thus the expected improvements in mechanical properties with increase in CNT weight content were not fully realized.