Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially C...Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio（0.2~2）.The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Fur-thermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of tem-perature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex be-haviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as ＂reference time＂,for example,to predict ignition delay time in turbulent reacting flow.展开更多
Combusting refuse for energy production is promising for their treatment and disposal. However, because of geographical constraints, there has not been a stable model for the energy utilization of refuse in low-oxygen...Combusting refuse for energy production is promising for their treatment and disposal. However, because of geographical constraints, there has not been a stable model for the energy utilization of refuse in low-oxygen plateau areas. This paper took Lhasa as an example to conduct gasification and incineration experiments on local representative combustible refuse,and relevant energy conversion laws were investigated. Results showed that under gasification and incineration modes, the energy conversion rate of any component of refuse can reach 75% and 85% in low-oxygen plateau areas at temperatures of 450 and 650 ℃, respectively, which were 5%–10% lower than those in plain areas. The regional distribution of energy conversion of refuse in Lhasa showed that the energy conversion rate under the gasification mode was 3%–5% lower than that of the incineration mode at 450 and 650 ℃. In terms of temperature, the energy conversion rates of refuse were 5%–10% lower at 450 ℃ than those at 650 ℃, but an energy conversion rate of more than 85% can still be achieved. Thus, gasification, incineration, or gasification-assisted secondary incineration at temperatures of at least 450 ℃ is suitable for energy recovery of refuse in low-oxygen plateau areas.展开更多
This study investigated the formation and emission characteristics of nitric oxide(NO) from flameless MILD(moderate or intensive low-oxygen dilution) combustion(MILDC) versus traditional visible-flame combustion(TC) i...This study investigated the formation and emission characteristics of nitric oxide(NO) from flameless MILD(moderate or intensive low-oxygen dilution) combustion(MILDC) versus traditional visible-flame combustion(TC) in a 30-k W furnace. Both combustion processes were experimentally operated successively in the same furnace, burning natural gas at a fixed rate of 19 k W and the equivalence ratio of 0.86. Numerical simulations of TC and MILDC were carried out to explain their distinction in the measured furnace temperature and exhaust NO emissions. Present measurements of the NO emission(XNO) versus a varying furnace wall temperature(Tw) have revealed, at the first time, that the relationship of XNO ~ Tw was exponential in both TC and MILDC. By analyzing the simulated results, the average temperature over the reaction zone was identified to be the common characteristic temperature for scaling NO emissions of both cases. Moreover, relative to TC, MILDC had a fairly uniform temperature distribution and low peak temperature, thus reducing the NO emission by over 90%. The thermal-NO formation was found to contribute more than 70%-80% to the total XNO from TC while the N2O-intermediate route dominated the NO emission from MILDC.展开更多
In order to reduce the content of oxygen and sulfur in steel, and produce low-sulfur and low-oxygen steel, study on slag has been carried out. Refining slag system of CaO-SiO2-Al2O3 is put forward with the considerati...In order to reduce the content of oxygen and sulfur in steel, and produce low-sulfur and low-oxygen steel, study on slag has been carried out. Refining slag system of CaO-SiO2-Al2O3 is put forward with the consideration of slag amount from converter, oxidizability of slag and activity of oxygen in molten steel. On this basis, refining slagging system for low-sulfur and low-oxygen steel has been developed combined with the modification of slag from converter and composition control of refining slag in LF treatment process. The results show that oxygen content is not more than 15×10-6, as well as sulfur content is as low as 0.005% in tube blank steel. And it achieves the production of low-sulfur and low-oxygen steel.展开更多
This paper investigates the effects of coflow O2 level and temperature on diffusion flame of a CH4/H2 jet in hot coflow （JHC） from a burner system similar to that of Dally et al. The coflow O2 mass fraction （ Yo2 ...This paper investigates the effects of coflow O2 level and temperature on diffusion flame of a CH4/H2 jet in hot coflow （JHC） from a burner system similar to that of Dally et al. The coflow O2 mass fraction （ Yo2 ） is varied from 3% to 80% and the temperature （Tcof） from 1200 K to 1700 K. The Eddy Dissipation Concept （EDC） model with detailed reaction mechanisms GRI-Mech 3.0 is used for all simulations. To validate the modeling, several JHC flames are predicted under the experimental conditions of Dally et al. [Proc. Combust. Inst., 29 （1）, 1147-1154 （2002）] and the results obtained match well with the measurements. Results demonstrate that, when Yo2 decreased, the diffusion combustion is likely to transform from traditional combustion to MILD （Moderate or Intense Low-oxygen Dilution） combustion mode. When Tcof is higher, the temperature distribution over the whole domain trends to be more uniform. Reducing yo2 or Tcof leads to less production of intermediate species OH and CO. It is worth noting that if Yo2 is high enough （ Yo2 〉80%）, increasing Yo2 does not cause obvious temperature increase.展开更多
基金Supported by the National Natural Science Foundation of China (50206014)the Shuguang Scholar Program of Shanghai Education Development Foundation (05SG23)
文摘Homogeneous mixtures of CH4/air under moderate or intense low-oxygen dilution（MILD） combustion conditions were numerically studied to clarify the fundamental effects of exhaust gas recirculation（EGR）,espe-cially CO2 in EGR gases,on ignition characteristics.Specifically,effects of CO2 addition on autoignition delay time were emphasized at temperature between 1200 K and 1600 K for a wide range of the lean-to-rich equivalence ratio（0.2~2）.The results showed that the ignition delay time increased with equivalence ratio or CO2 dilution ratio.Fur-thermore,ignition delay time was seen to be exponentially related with the reciprocal of initial temperature.Special concern was given to the chemical effects of CO2 on the ignition delay time.The enhancement of ignition delay time with CO2 addition can be mainly ascribed to the decrease of H,O and OH radicals.The predictions of tem-perature profiles and mole fractions of CO and CO2 were strongly related to the chemical effects of CO2.A single ignition time correlation was obtained in form of Arrhenius-type for the entire range of conditions as a function of temperature,CH4 mole fraction and O2 mole fraction.This correlation could successfully capture the complex be-haviors of ignition of CH4/air/CO2 mixture.The results can be applied to MILD combustion as ＂reference time＂,for example,to predict ignition delay time in turbulent reacting flow.
文摘Combusting refuse for energy production is promising for their treatment and disposal. However, because of geographical constraints, there has not been a stable model for the energy utilization of refuse in low-oxygen plateau areas. This paper took Lhasa as an example to conduct gasification and incineration experiments on local representative combustible refuse,and relevant energy conversion laws were investigated. Results showed that under gasification and incineration modes, the energy conversion rate of any component of refuse can reach 75% and 85% in low-oxygen plateau areas at temperatures of 450 and 650 ℃, respectively, which were 5%–10% lower than those in plain areas. The regional distribution of energy conversion of refuse in Lhasa showed that the energy conversion rate under the gasification mode was 3%–5% lower than that of the incineration mode at 450 and 650 ℃. In terms of temperature, the energy conversion rates of refuse were 5%–10% lower at 450 ℃ than those at 650 ℃, but an energy conversion rate of more than 85% can still be achieved. Thus, gasification, incineration, or gasification-assisted secondary incineration at temperatures of at least 450 ℃ is suitable for energy recovery of refuse in low-oxygen plateau areas.
基金support of National Natural Science Foundation of China(No.51776003)is gratefully acknowledged。
文摘This study investigated the formation and emission characteristics of nitric oxide(NO) from flameless MILD(moderate or intensive low-oxygen dilution) combustion(MILDC) versus traditional visible-flame combustion(TC) in a 30-k W furnace. Both combustion processes were experimentally operated successively in the same furnace, burning natural gas at a fixed rate of 19 k W and the equivalence ratio of 0.86. Numerical simulations of TC and MILDC were carried out to explain their distinction in the measured furnace temperature and exhaust NO emissions. Present measurements of the NO emission(XNO) versus a varying furnace wall temperature(Tw) have revealed, at the first time, that the relationship of XNO ~ Tw was exponential in both TC and MILDC. By analyzing the simulated results, the average temperature over the reaction zone was identified to be the common characteristic temperature for scaling NO emissions of both cases. Moreover, relative to TC, MILDC had a fairly uniform temperature distribution and low peak temperature, thus reducing the NO emission by over 90%. The thermal-NO formation was found to contribute more than 70%-80% to the total XNO from TC while the N2O-intermediate route dominated the NO emission from MILDC.
文摘In order to reduce the content of oxygen and sulfur in steel, and produce low-sulfur and low-oxygen steel, study on slag has been carried out. Refining slag system of CaO-SiO2-Al2O3 is put forward with the consideration of slag amount from converter, oxidizability of slag and activity of oxygen in molten steel. On this basis, refining slagging system for low-sulfur and low-oxygen steel has been developed combined with the modification of slag from converter and composition control of refining slag in LF treatment process. The results show that oxygen content is not more than 15×10-6, as well as sulfur content is as low as 0.005% in tube blank steel. And it achieves the production of low-sulfur and low-oxygen steel.
基金Supported by the National Natural Science Foundation of China （51276002）, and the Specific Research Fund for the Doctoral Program of Higher Education of China （20110001130014）.
文摘This paper investigates the effects of coflow O2 level and temperature on diffusion flame of a CH4/H2 jet in hot coflow （JHC） from a burner system similar to that of Dally et al. The coflow O2 mass fraction （ Yo2 ） is varied from 3% to 80% and the temperature （Tcof） from 1200 K to 1700 K. The Eddy Dissipation Concept （EDC） model with detailed reaction mechanisms GRI-Mech 3.0 is used for all simulations. To validate the modeling, several JHC flames are predicted under the experimental conditions of Dally et al. [Proc. Combust. Inst., 29 （1）, 1147-1154 （2002）] and the results obtained match well with the measurements. Results demonstrate that, when Yo2 decreased, the diffusion combustion is likely to transform from traditional combustion to MILD （Moderate or Intense Low-oxygen Dilution） combustion mode. When Tcof is higher, the temperature distribution over the whole domain trends to be more uniform. Reducing yo2 or Tcof leads to less production of intermediate species OH and CO. It is worth noting that if Yo2 is high enough （ Yo2 〉80%）, increasing Yo2 does not cause obvious temperature increase.
