The study was undertaken to investigate the properties of cassava starch and gum arabic bonded briquettes from the sawdust of Azadirachta indica. The briquettes were produced using a Jack press at an average pressure ...The study was undertaken to investigate the properties of cassava starch and gum arabic bonded briquettes from the sawdust of Azadirachta indica. The briquettes were produced using a Jack press at an average pressure of 10.7 kg.cm^-2. The sawdust and binders were mixed at ratios of 100：15, 100：25, 100：35 and 100：45 in weight, respec tively. The briquettes produced were subjected to physical and combustion tests. Both the physical and combustion properties of the briquettes vary with binder types and binder levels （p 〈 0.05）. The result shows that briquettes bonded with starch gave better performance based on density of 0.546 g.cm^-3, durability rating of 95.93%, heating value of 33.09 MJ.kg^-1, percentage of fixed carbon of 84.70% and low ash and volatile matter of 3.35% and 11.95%, respectively, while briquette bonded with gum arabic has density of 0.425 g.cm^-3, durability rating of 94.85%, heating value of 32.76 MJ.kg^-l, percentage of fixed carbon of 87.30% and low ash and volatile matter of 4.45% and 8.75, respectively. Since the aim of briquetting is to produce briquette that will serve as a good source of fuel and support combustion, the best briquette was produced when the sawdust-starch ratio and sawdust-gum arabic ratio was 100：25 and 100：35, respectively.展开更多
In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan ...In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.展开更多
The corrosion resistances of widely used X33CrNiMnN23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8 high-alloyed austenite valves steels in combustion engines have been compared. The comparison was performed ...The corrosion resistances of widely used X33CrNiMnN23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8 high-alloyed austenite valves steels in combustion engines have been compared. The comparison was performed on the basis of results of kinetic corrosion of the test steels in combustion gases from gasoline with 5% ethanol additive （v/v） and the combustion gases from propane-butane. The corrosion test was performed gravimetrically under thermal shock conditions by heating samples of the test steels from room temperature up to 1,173 K in exhaust gases from a combustion engine, and holding them at this temperature for 2 h and then cooling at room temperature for about 25 min. Then the same thermal shock was repeated and after every 10 to 20 such cycles the mass of the specimens was measured. This experiment simulated the working conditions of a highly thermal loaded exhaust valve in a spark ignited engine. The analysis performed shows that the corrosion resistances of X33CrNiMnN23-8 and X50CrMnNiNbN21-9 valve steels in an environment of combustion gases from propane-butane and in gases from gasoline with 5% ethanol additive （v/v） are comparable, whereas the corrosion resistance of X53CrMnNiN20-8 and X55CrMnNiN20-8 valve steels in an environment of combustion gases from propane-butane is slightly worse than in gases from gasoline with 5% ethanol additive （v/v）.展开更多
Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications, especially for the steel and refractory industry. Accurate turbulent flow and temperature fields are of major import...Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications, especially for the steel and refractory industry. Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields. The performances of the GRI-Mech 3.0 and the Jones and Lindstedt mechanisms are compared. Detailed chemistry is included with the GRI-Mech 3.0 and J-L kinetic mechanisms in combination with the laminar flamelet combustion model. The combustion system selected for this comparison is a confined non-premixed methane flame surrounded by co-flowing air The simulation results are compared with experimental data of Lewis and Smoot （2001）.展开更多
文摘The study was undertaken to investigate the properties of cassava starch and gum arabic bonded briquettes from the sawdust of Azadirachta indica. The briquettes were produced using a Jack press at an average pressure of 10.7 kg.cm^-2. The sawdust and binders were mixed at ratios of 100：15, 100：25, 100：35 and 100：45 in weight, respec tively. The briquettes produced were subjected to physical and combustion tests. Both the physical and combustion properties of the briquettes vary with binder types and binder levels （p 〈 0.05）. The result shows that briquettes bonded with starch gave better performance based on density of 0.546 g.cm^-3, durability rating of 95.93%, heating value of 33.09 MJ.kg^-1, percentage of fixed carbon of 84.70% and low ash and volatile matter of 3.35% and 11.95%, respectively, while briquette bonded with gum arabic has density of 0.425 g.cm^-3, durability rating of 94.85%, heating value of 32.76 MJ.kg^-l, percentage of fixed carbon of 87.30% and low ash and volatile matter of 4.45% and 8.75, respectively. Since the aim of briquetting is to produce briquette that will serve as a good source of fuel and support combustion, the best briquette was produced when the sawdust-starch ratio and sawdust-gum arabic ratio was 100：25 and 100：35, respectively.
基金Project(50576005) supported by the National Natural Science Foundation of China
文摘In order to study the slagging characteristics of boiler combustion liners during pulverized coal stream combustion, the slag samples on the surface of combustion liner were investigated by X-ray diffractometry, scan electron microscopy and energy dispersive X-ray analysis, and the transformation characteristics of the compositions and crystal phases were studied. The results show that the size of slag granules decreases as the slagging temperature increases; the crystallinity of coal ash I reduces to about 48.6% when the temperature is increased up to 1 350 ℃, and that of the coal ash II reduces to about 65% when the temperature is increased up to 1 500 ℃; the encroachment of molten coal ash to the combustion liner is strengthened. At the same time, the diffusion and the segregation of the compositions in combustion liners have selectivity, which is in favor of enhancing the content of crystal phases, weakening the conglutination among molten slag compositions and combustion liner, and avoiding yielding big clinkers. But the diffusion of the compositions in combustion liners increases the porosity and decreases the mechanical intensity of combustion liner, and makes the slag encroachment to the liner become more serious.
文摘The corrosion resistances of widely used X33CrNiMnN23-8, X50CrMnNiNbN21-9, X53CrMnNiN20-8 and X55CrMnNiN20-8 high-alloyed austenite valves steels in combustion engines have been compared. The comparison was performed on the basis of results of kinetic corrosion of the test steels in combustion gases from gasoline with 5% ethanol additive （v/v） and the combustion gases from propane-butane. The corrosion test was performed gravimetrically under thermal shock conditions by heating samples of the test steels from room temperature up to 1,173 K in exhaust gases from a combustion engine, and holding them at this temperature for 2 h and then cooling at room temperature for about 25 min. Then the same thermal shock was repeated and after every 10 to 20 such cycles the mass of the specimens was measured. This experiment simulated the working conditions of a highly thermal loaded exhaust valve in a spark ignited engine. The analysis performed shows that the corrosion resistances of X33CrNiMnN23-8 and X50CrMnNiNbN21-9 valve steels in an environment of combustion gases from propane-butane and in gases from gasoline with 5% ethanol additive （v/v） are comparable, whereas the corrosion resistance of X53CrMnNiN20-8 and X55CrMnNiN20-8 valve steels in an environment of combustion gases from propane-butane is slightly worse than in gases from gasoline with 5% ethanol additive （v/v）.
文摘Turbulent non-premixed combustion of gaseous fuels is of importance for many technical applications, especially for the steel and refractory industry. Accurate turbulent flow and temperature fields are of major importance in order to predict details on the concentration fields. The performances of the GRI-Mech 3.0 and the Jones and Lindstedt mechanisms are compared. Detailed chemistry is included with the GRI-Mech 3.0 and J-L kinetic mechanisms in combination with the laminar flamelet combustion model. The combustion system selected for this comparison is a confined non-premixed methane flame surrounded by co-flowing air The simulation results are compared with experimental data of Lewis and Smoot （2001）.
