A solid state H2S/air electrochemical cell having the configuration of H2S, (MoS2+NiS+Ag)/YSZ/Pt, air has been examined with different H2S flow rates and concentrations at atmospheric pressure and 750-850 ℃. Performa...A solid state H2S/air electrochemical cell having the configuration of H2S, (MoS2+NiS+Ag)/YSZ/Pt, air has been examined with different H2S flow rates and concentrations at atmospheric pressure and 750-850 ℃. Performance of the fuel cell was dependent on anode compartment H2S flow rate and concentration. The cell open-circuit voltage increased with increasing H2S flow rate. It was found that increasing both H2S flow rate and H2S concentration improved current-voltage and power density performance. This is resulted from improved gas diffusion in anode and increased concentration of anodic electroactive species. Operation at elevated H2S concentration improved the cell performance at a given gas flow rate. However, as low as 5% H2S in gas mixture can also be utilized as fuel feed to cells. Highest current and power densities, 17500mA·cm-2 and 200mW·cm-2, are obtained with pure H2S flow rate of 50ml·min-1 and air flow rate of 100ml·min-1 at 850℃.展开更多
Regarding the research on alternatives for monopropellant hydrazine, several so called green propellants are currently under investigation or qualification. Aside others, the DLR Institute of Space Propulsion investig...Regarding the research on alternatives for monopropellant hydrazine, several so called green propellants are currently under investigation or qualification. Aside others, the DLR Institute of Space Propulsion investigates a N20/C2I-I4 premixed green propellant. During the research activities, flashback from the rocket combustion chamber into the feeding system has been identified as a major challenge when using the propellant mixture. This paper shows the results of ignition experiments conducted in a cylindrical, optical accessible ignition chamber. During the ignition and flame propagation process, pressure, temperature and high-speed video data were collected. The high speed video data were used to analyze the flame propagation speed. The obtained propagation speed was about 20 rn/s at ignition, while during further propagation of the flame speeds of up to 120 m/s were measured. Additionally, two different porous materials as flame arresting elements were tested： Porous stainless steel and porous bronze material. For both materials Peclet numbers for flashback were derived. The critical Peclet number for the sintered bronze material was around 20, while for the sintered stainless steel the critical Peclet number seems to be larger than 40. Due to the test results, sintered porous materials seem to be suitable as flashback arresters.展开更多
Hydrogen, the cleanest and most promising energy vector, can be produced by solar into chemical energy conversion, either by the photocatalytic direct splitting of water into Hand O, or, more efficiently,in the presen...Hydrogen, the cleanest and most promising energy vector, can be produced by solar into chemical energy conversion, either by the photocatalytic direct splitting of water into Hand O, or, more efficiently,in the presence of sacrificial reagents, e.g., in the so-called photoreforming of organics. Efficient photocatalytic materials should not only be able to exploit solar radiation to produce electron–hole pairs, but also ensure enough charge separation to allow electron transfer reactions, leading to solar energy driven thermodynamically up-hill processes. Recent achievements of our research group in the development and testing of innovative TiO-based photocatalytic materials are presented here, together with an overview on the mechanistic aspects of water photosplitting and photoreforming of organics. Photocatalytic materials were either（i） obtained by surface modification of commercial photocatalysts, or produced（ii） in powder form by different techniques, including traditional sol gel synthesis, aiming at engineering their electronic structure, and flame spray pyrolysis starting from organic solutions of the precursors, or（iii） in integrated form, to produce photoelectrodes within devices, by radio frequency magnetron sputtering or by electrochemical growth of nanotube architectures, or photocatalytic membranes, by supersonic cluster beam deposition.展开更多
Fast depletion of fossil fuels with its resources already passed its mid depletion region and the pollution levels already reached unsafe levels which make it utmost necessity to search for alternative fuels to meet s...Fast depletion of fossil fuels with its resources already passed its mid depletion region and the pollution levels already reached unsafe levels which make it utmost necessity to search for alternative fuels to meet sustainable energy demand with minimum environmental impact. Among alternative fuels, hydrogen is considered as the near future, long term renewable, sustainable and non-polluting fuel. In the present paper, hydrogen fueled internal combustion engine fundamentals highlighted and presented relating to hydrogen combustion properties. A Mat lab programmed hydrogen temperature-entropy-energy chart is developed and presented for fresh charge and products of combustion at different excess air factors per mole combustion gases. The chart, then, used to represent a SI hydrogen-fueled fuel/air cycle analysis, which proved to be valuable design tool for engine sizing and for prediction of engine performance. Predictions carried out using the hydrogen F/A cycle analysis at different λ show low brake specific fuel consumption and low volume specific power compared with conventional SI engine.展开更多
Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5-1.5,preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of0%,20%,and...Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5-1.5,preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of0%,20%,and 50%.The measurements were conducted using a Bunsen burner and an optical schlieren system.The results show that the flame propagation speed and combustion stabilities of the premixed gases increase with increasing preheating temperature.The combustion stability is significantly improved under the 20%hydrogen volume fraction condition.For the NH_(3)/H_(2)mixtures with a hydrogen volume fraction of 50%,the flame propagation speed at 673 K with a stoichiometric ratio is approximately 4.85 times that at 298 K.The experimental results show that at 673 K,the flame propagation speed of the NH_(3)/H_(2)/air mixture increases by 7.8times when the hydrogen volume fraction increases from 20%to 80%.The numerical results predicted with the Mei,Shrestha,and Stagni mechanisms are compared with the experimental data.The mechanisms proposed by Shrestha and Stagni overestimate the flame propagation speed,especially at high preheating temperatures.The results predicted with the Mei mechanism are consistent with the available data.The concentrations of OH,H,O and NH_(2)are increased by the hydrogen addition;thus,the ammonia consumption is accelerated.展开更多
The oxidative polycondensation reaction conditions of 4-[（4-hydroxybenzylidene） amino] phenol （4-HBAP） were studied with H2O2, air oxygen and NaOCl in an aqueous alkaline medium between 50 and 90℃. The structures...The oxidative polycondensation reaction conditions of 4-[（4-hydroxybenzylidene） amino] phenol （4-HBAP） were studied with H2O2, air oxygen and NaOCl in an aqueous alkaline medium between 50 and 90℃. The structures of the obtained monomer and polymer were confirmed by FT-IR, UV-Vis, 1H- and 13C-NMR and elemental analysis. The characterization was made by TG-DTA, size exclusion chromatography （SEC） and solubility tests. At the optimum reaction conditions, the yield of poly[4-（4-hydroxybenzylidene amino） phenol] （P-4-HBAP） was found to be 48.3% （for H2O2 oxidant）, 80.5% （for air O2 oxidant） and 86.4% （for NaOCl oxidant）. According to the SEC analysis, the number-average molecular weight （Mn）, weight-average molecular weight （Mw） and polydispersity index （PDI） values of P-4-HBAP was found to be 8950, 10970 g tool^-1 and 1.225, respectively, using H202; and l l610, 15190 g tool^-1 and 1.308 respectively, using air 02 and 7900, 9610 g mol^-1 and 1.216, respectively, using NaOC1. According to TG-DTA analyses, P-4-HBAP was more stable than 4-HBAP against thermal decomposition. The weight loss of P-4-HBAP was found to be 49.27% at 1000℃. The highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO） values calculated from electrochemical measurement. Electrochemical energy gaps （Eg＇） of 4-HBAP and P-4-HBAP were found to be -5.46, -5.28; -2.26, -2.67; 3.20 and 2.61 eV, respectively. According to UV-Vis measurements, optical band gap （Eg） of 4-HBAP and P-4-HBAP were found to be 3.34 and 3.01 eV, respectively. Also, antimicrobial activities of 4-HBAP and P-4-HBAP were examined against selected some bacteria. The electrical conductivity of the polymer was measured after doping with iodine.展开更多
Ambient concentrations of H<sub>2</sub>S were determined by modeling the H<sub>2</sub>S emissions dispersion for three sites located in the surroundings of oil and gas maritime terminal at the ...Ambient concentrations of H<sub>2</sub>S were determined by modeling the H<sub>2</sub>S emissions dispersion for three sites located in the surroundings of oil and gas maritime terminal at the southeast of Mexico. Hazard quotient is reported for different age groups. Paraiso City in Tabasco State reported the highest values for over 19 years old group (0.49). It was concluded that there was no threat to human health due to H<sub>2</sub>S emissions derived from the maritime terminal for the studied sites.展开更多
基金Supported by the Natural Science Foundation of Guangdong Province (No. 031424).
文摘A solid state H2S/air electrochemical cell having the configuration of H2S, (MoS2+NiS+Ag)/YSZ/Pt, air has been examined with different H2S flow rates and concentrations at atmospheric pressure and 750-850 ℃. Performance of the fuel cell was dependent on anode compartment H2S flow rate and concentration. The cell open-circuit voltage increased with increasing H2S flow rate. It was found that increasing both H2S flow rate and H2S concentration improved current-voltage and power density performance. This is resulted from improved gas diffusion in anode and increased concentration of anodic electroactive species. Operation at elevated H2S concentration improved the cell performance at a given gas flow rate. However, as low as 5% H2S in gas mixture can also be utilized as fuel feed to cells. Highest current and power densities, 17500mA·cm-2 and 200mW·cm-2, are obtained with pure H2S flow rate of 50ml·min-1 and air flow rate of 100ml·min-1 at 850℃.
文摘Regarding the research on alternatives for monopropellant hydrazine, several so called green propellants are currently under investigation or qualification. Aside others, the DLR Institute of Space Propulsion investigates a N20/C2I-I4 premixed green propellant. During the research activities, flashback from the rocket combustion chamber into the feeding system has been identified as a major challenge when using the propellant mixture. This paper shows the results of ignition experiments conducted in a cylindrical, optical accessible ignition chamber. During the ignition and flame propagation process, pressure, temperature and high-speed video data were collected. The high speed video data were used to analyze the flame propagation speed. The obtained propagation speed was about 20 rn/s at ignition, while during further propagation of the flame speeds of up to 120 m/s were measured. Additionally, two different porous materials as flame arresting elements were tested： Porous stainless steel and porous bronze material. For both materials Peclet numbers for flashback were derived. The critical Peclet number for the sintered bronze material was around 20, while for the sintered stainless steel the critical Peclet number seems to be larger than 40. Due to the test results, sintered porous materials seem to be suitable as flashback arresters.
基金supported by Fondazione Cariplo through Grants 2009-2477 and 2013-0615
文摘Hydrogen, the cleanest and most promising energy vector, can be produced by solar into chemical energy conversion, either by the photocatalytic direct splitting of water into Hand O, or, more efficiently,in the presence of sacrificial reagents, e.g., in the so-called photoreforming of organics. Efficient photocatalytic materials should not only be able to exploit solar radiation to produce electron–hole pairs, but also ensure enough charge separation to allow electron transfer reactions, leading to solar energy driven thermodynamically up-hill processes. Recent achievements of our research group in the development and testing of innovative TiO-based photocatalytic materials are presented here, together with an overview on the mechanistic aspects of water photosplitting and photoreforming of organics. Photocatalytic materials were either（i） obtained by surface modification of commercial photocatalysts, or produced（ii） in powder form by different techniques, including traditional sol gel synthesis, aiming at engineering their electronic structure, and flame spray pyrolysis starting from organic solutions of the precursors, or（iii） in integrated form, to produce photoelectrodes within devices, by radio frequency magnetron sputtering or by electrochemical growth of nanotube architectures, or photocatalytic membranes, by supersonic cluster beam deposition.
文摘Fast depletion of fossil fuels with its resources already passed its mid depletion region and the pollution levels already reached unsafe levels which make it utmost necessity to search for alternative fuels to meet sustainable energy demand with minimum environmental impact. Among alternative fuels, hydrogen is considered as the near future, long term renewable, sustainable and non-polluting fuel. In the present paper, hydrogen fueled internal combustion engine fundamentals highlighted and presented relating to hydrogen combustion properties. A Mat lab programmed hydrogen temperature-entropy-energy chart is developed and presented for fresh charge and products of combustion at different excess air factors per mole combustion gases. The chart, then, used to represent a SI hydrogen-fueled fuel/air cycle analysis, which proved to be valuable design tool for engine sizing and for prediction of engine performance. Predictions carried out using the hydrogen F/A cycle analysis at different λ show low brake specific fuel consumption and low volume specific power compared with conventional SI engine.
基金supported by the China United Gas Turbine Technology Co.Ltd.(Grant number J920)。
文摘Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5-1.5,preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of0%,20%,and 50%.The measurements were conducted using a Bunsen burner and an optical schlieren system.The results show that the flame propagation speed and combustion stabilities of the premixed gases increase with increasing preheating temperature.The combustion stability is significantly improved under the 20%hydrogen volume fraction condition.For the NH_(3)/H_(2)mixtures with a hydrogen volume fraction of 50%,the flame propagation speed at 673 K with a stoichiometric ratio is approximately 4.85 times that at 298 K.The experimental results show that at 673 K,the flame propagation speed of the NH_(3)/H_(2)/air mixture increases by 7.8times when the hydrogen volume fraction increases from 20%to 80%.The numerical results predicted with the Mei,Shrestha,and Stagni mechanisms are compared with the experimental data.The mechanisms proposed by Shrestha and Stagni overestimate the flame propagation speed,especially at high preheating temperatures.The results predicted with the Mei mechanism are consistent with the available data.The concentrations of OH,H,O and NH_(2)are increased by the hydrogen addition;thus,the ammonia consumption is accelerated.
基金This work was financially supported by the TUBITAK Grants Commission for a research grant(No.TBAG-2451(104T062)).
文摘The oxidative polycondensation reaction conditions of 4-[（4-hydroxybenzylidene） amino] phenol （4-HBAP） were studied with H2O2, air oxygen and NaOCl in an aqueous alkaline medium between 50 and 90℃. The structures of the obtained monomer and polymer were confirmed by FT-IR, UV-Vis, 1H- and 13C-NMR and elemental analysis. The characterization was made by TG-DTA, size exclusion chromatography （SEC） and solubility tests. At the optimum reaction conditions, the yield of poly[4-（4-hydroxybenzylidene amino） phenol] （P-4-HBAP） was found to be 48.3% （for H2O2 oxidant）, 80.5% （for air O2 oxidant） and 86.4% （for NaOCl oxidant）. According to the SEC analysis, the number-average molecular weight （Mn）, weight-average molecular weight （Mw） and polydispersity index （PDI） values of P-4-HBAP was found to be 8950, 10970 g tool^-1 and 1.225, respectively, using H202; and l l610, 15190 g tool^-1 and 1.308 respectively, using air 02 and 7900, 9610 g mol^-1 and 1.216, respectively, using NaOC1. According to TG-DTA analyses, P-4-HBAP was more stable than 4-HBAP against thermal decomposition. The weight loss of P-4-HBAP was found to be 49.27% at 1000℃. The highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO） values calculated from electrochemical measurement. Electrochemical energy gaps （Eg＇） of 4-HBAP and P-4-HBAP were found to be -5.46, -5.28; -2.26, -2.67; 3.20 and 2.61 eV, respectively. According to UV-Vis measurements, optical band gap （Eg） of 4-HBAP and P-4-HBAP were found to be 3.34 and 3.01 eV, respectively. Also, antimicrobial activities of 4-HBAP and P-4-HBAP were examined against selected some bacteria. The electrical conductivity of the polymer was measured after doping with iodine.
文摘Ambient concentrations of H<sub>2</sub>S were determined by modeling the H<sub>2</sub>S emissions dispersion for three sites located in the surroundings of oil and gas maritime terminal at the southeast of Mexico. Hazard quotient is reported for different age groups. Paraiso City in Tabasco State reported the highest values for over 19 years old group (0.49). It was concluded that there was no threat to human health due to H<sub>2</sub>S emissions derived from the maritime terminal for the studied sites.
