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In the present work, Ag nanoparticles were added to polyurea coating in order to improve its antibacterial and electrochemical properties in sulfide-reducing bacteria-containing media. To this end, Ag nano-powder was mixed with two component polyuria, and then the antibacterial behavior of the nanocomposite coating was studied in sulfate-reducing bacteria (SRB)-containing medium. The results revealed the inhibitory effects of nanocomposite coating on the formation of SRB biofilms on the samples. Moreover, the SRB population decreased in contact with the Ag nanoparticles-mixed coating over 7 days. Investigation of the growth and activity of the bacteria represented the effective antibacterial properties of Ag nanoparticles in the polyurea matrix. Furthermore, EIS (electrochemical impedance spectroscopy) measurements indicated that the corrosion properties of the nanocomposite coating improved considerably over 7 days. The coating resistance increased 2 times by adding Ag nanoparticles after 1 day and 3.3 times after 7 days. In accordance with the same results, the charge transfer resistance increased 1.5 times and 1.1 times by adding Ag nanoparticles after 1 day and 7 days, respectively. The improvement in the protective properties of the nanocomposite coating are reflected in the increase in both film and charge transfer resistance.

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Injection strategy and piston bowl geometry play a very effective role in engine design. Hydrogen fuel in liquid or gaseous form is high in energy, and engine that burns pure hydrogen produces almost no exhaust emissions. In this article, influences of spray angle and bowl center depth on engine performance (indicated power and efficiency), fuel economy, and exhaust emissions (CO, CO 2 , NO, soot, and hydrocarbon) are investigated for a hydrogen (6%) + diesel dual fuel engine under 1500, 2000, and 3000 r/min speeds. Numerical simulation was performed using computational fluid dynamics code. To ensure validity of simulation, calculated in-cylinder mean pressure and rate of heat release were compared to experimental data, and the results specified a good accordance (for 1200 r/min and 70% load). The results of studies show that 160°spray angle is the best to achieve balanced emissions and more power and efficiency in comparison to other spray angles (120°, 130°, 140°, and 180°spray angles). It is found that taking into account the 160°spray angle in comparison to 120°spray angle, indicated power and efficiency increase by 25%, and the amount of exhaust CO, soot, and hydrocarbon reduces approximately by 76%, 71%, and 95%, respectively. It is determined that a deep bowl center depth leads to higher temperature (further NO emissions) and lower brake-specific fuel consumption. Three bowl center depths (5, 10, and 20 mm) were chosen for further investigation, and the 10-mm depth showed a suitable balance between exhaust emissions and power generated.

Application of methanol solvent for physical absorption of CO₂ and H₂S from CO₂/H₂S/CH₄ mixture in gas–liquid hollow fiber membrane gas absorber (HFMGA) was investigated. A computational mass transfer (CMT) model for simulation of HFMGA in the case of simultaneous separation of CO₂ and H₂S was developed. The membrane gas absorber model explicitly calculates for the rates of mass transfer through the membrane and components concentration profiles. Due to the lack of experimental data in the literature, the model was validated using available individual components’ water absorption data. The numerical predictions were in good agreement with the experimental data. The effects of operating conditions such as liquid velocity, gas velocity, temperature and pressure were analyzed. It is shown that methanol solvent can successfully be used for CO₂ and H₂S removal in membrane gas absorber. Also it is found that the concentration distribution of CO₂ and H₂S in the gas phase along the fiber length obeys plug flow model whereas in the methanol absorbent deeply affected by the interface concentration, absorbent velocity and diffusivity. In addition, it is shown that application of membrane gas absorber using methanol absorbents for H₂S removal and at higher flow rate is more efficient. Moreover, at operating pressures above 10 atm even at low absorbent rate, H₂S concentration depletion is relatively complete while at 1 atm this value is about 30%. This means that removal efficiency decreases with an increase in temperature and it is more important especially for H₂S