- Email: [email protected]
02677 Numerical study on NO formation in CH4-O2-N2 diffusion flame diluted with CO2
10 Engines (power generation and propulsion, electrical vehicles) C3H6, C3Hs, EA, CHsOH, C2HsOH, CH3CHO, C2HsCHO, CH3COCH3, CH3OCH3, CH3COOCHCH2 and CH3COOH have been obtained by coupling microprobe sampling with gas chromatographymass spectrometry (GC/MS) analysis. A detailed kinetic mechanism has been developed to model the E A oxidation in these conditions. The kinetic scheme includes 23 oxygenated species involved in 142 reversible reactions. It takes into account the first steps of the EA oxidation and the oxidation processes of all the measured oxygenated intermediate compounds. The proposed mechanism globally well predicts the experimental results obtained in the methane/air flames even if some discrepancies are pointed out. Sensitivity analysis allows the determination of the main reactional pathways involved in the thermal degradation of EA.
05/02677 Numerical study on NO formation in CH4-O2-N2 diffusion flame diluted with CO2 Hwang, D.-J. et al. International Journal of Energy Research, 2005, 29, (2), 107-120. Numerical study with momentum-balanced boundary conditions has been conducted to grasp chemical effects of added COz, to either fuelor oxidizer-side on flame structure and NO emission behaviour in CH4O2-N 2 diffusion flames. Cautious investigation is made for the comparison among the behaviours of principal chain branching and important H-removal key reactions. This describes successfully the reason why flame temperatures for fuel-side dilution are higher than those for oxidizer-side dilution. The role of the principal chain branching reaction is also recognized to be important even in the change of major flame structure caused by chemical effects. The importantly contributing reaction steps to NO production are examined. The reduced production rates of thermal NO and prompt NO due to chemical effects are much more remarkable for fuel-side dilution. It is atso found that the reaction step, H + NO + M = H N O + M plays a decisive role of the formation and destruction of prompt NO.
05/02678 Process modeling for control of a batch heat treatment furnace with low NOx radiant tube burner Tiwari, M. K. et al. Energy Conversion and Management, 2005, 46, (1314), 2093-2113. In this first part of a two-part problem, a process model for control of a batch-type heat treatment furnace with low NOx radiant tube burner has been developed. The model considers coupling between the different components and the wide variation in time scales of the processes involved. The heat transport between the gas stream and the radiant tube is modelled by a conjugate convectio~radiation mode using an empirical correlation for the convection and an optically thin radiation model. The combustion is considered in a highly preheated and diluted mode with single step modelling of the chemical kinetics. The heat transfer between the radiant tube and the load is considered to be only through radiation. The model is used in a companion paper to generate optimal operating conditions for the desired performance and emission characteristics.
05•02679 Pyrolysis of blends of different types of sewage sludge with one bituminous coal Folgueras, M. B. et al. Energy, 2005, 30, (7), 1079 1091. Pyrolysis of sewage sludge samples from three Asturian urban wastewater treatment plants was carried out. One high volatile bituminous coal and its blends with 10 and 50 wt% of sludge were studied by thermo-gravimetry. The same operational conditions (a constant heating rate of 10°C/min in the temperature range 25-800°C and a Na flow of 200 cm3/min) were maintained throughout. The results indicate that sludge is formed by two organic fractions with different reactivity, whose devolatilization processes partially overlap. Both fractions are more reactive than coal, since they decompose and devolatilize at temperatures lower than coal. Under oxidizing conditions, the action of oxygen during pyrolysis depends on the conditioning of sludge. If sludge is treated with FeC13, oxidative pyrolysis takes place. The behaviour of sludge-coal blends is intermediate between those of the coal and the corresponding sludge, without interactions between both blend components. In addition, a kinetic analysis was performed to fit thermo-gravimetric data, the global processes being considered as a series of consecutive first order reactions. A reasonable fit to the experimental data was obtained for all materials and their blends.
05/02680 Soot formation in inverse diffusion flames of diluted ethene Lee, E. J. et al. Fuel, 2005, 84, (5), 543-550. Experimental measurements of flame structure and soot characteristics were performed for ethene inverse diffusion flames (IDFs). IDFs are considered as an ideal flow field for studying incipient soot because the soot particles do not experience the oxidation process. In this study, an laser-induced fluorescence image clarified the reaction zone of IDFs with OH signal and polyeyclic aromatic hydrocarbon distribution. A
laser scattering technique also identified the soot particles. To address the degree of soot maturing, the carbon to hydrogen ratio and morphology of the soot sample were investigated. From the measurements, the effect of flow residence time and temperature on soot inception could be estimated, and more details on soot characteristics in the IDFs were determined according to the fuel dilution ratio and air/fuel ratio. Fuel dilution results in a decrease of temperature and an enhancement of residence time, but the critical dilution mole fraction is found for which temperature does not effect soot growth. Soot inception is also found to be weakly dependent on temperature as influenced by fuel dilution.
05/02681 Temperature and air-fuel ratio dependent specific heat ratio functions for lean burned and unburned mixture Ceviz, M. A. and Kaymaz, I Energy Conversion and Management, 2005, 46, (15 16), 2387 2404. The most important thermodynamic property used in heat release calculations for engines is the specific heat ratio. The functions proposed in the literature for the specific heat ratio are temperature dependent and apply at or near stoichiometric air-fuel ratios. However, the specific heat ratio is also influenced by the gas composition in the engine cylinder and especially becomes important for lean combustion engines. In this study, temperature and air-fuel ratio dependent specific heat ratio functions were derived to minimize the error by using an equilibrium combustion model for burned and unburned mixtures separately. After the error analysis between the equilibrium combustion model and the derived functions is presented, the results of the global specific heat ratio function, as varying with mass fraction burned, were compared with the proposed functions in the literature. The results of the study showed that the derived functions are more feasible at lean operating conditions of a spark ignition engine.
05102682 Transient development of methane-air diffusion flame in a confined geometry with and without air-preheat Mandal, B. K. et al. International Journal of Energy Research, 2005, 29, (2), 145-17. The transient development of a methane-air diffusion flame is studied numerically in the present work in a confined geometry. An explicit finite difference based numerical model is developed for the solution of transient reacting flow with varying thermodynamic and transport properties. The effect of air preheat on the flow and temperature fields at different time planes are studied by comparing two cases with air temperatures of 300 and 400 K, respectively. The preheating of air is found to complicate the flow situation with the formation of additional vortices. Thermal stratification in the flow causes a radial stretching of the flame, which is more evident with higher preheat temperature. In the absence of any preheating a stable re-circulation of ambient air is observed to extend from the exit plane into the domain adjacent to the wall. The mixing of ambient air results in gradual drooping in the bulk mean temperature of the flow. Such drooping nature in the bulk temperature distribution is not found with air preheat due to the absence of any stable re-circulation. The complication in the initial flow transients delays the attainment of steady situation for the flame with preheat.
l0
ENGINES Power generation and propulsion, electrical vehicles
05•02683 A linear encoder using a chiaroscuro and its extension to switched reluctance motor drive Kang, F.-S. and Park, S.-J. Energy Conversion and Management, 2005, 46, (7 8), 1119-1128. In switched reluctance motor drives, the on-off switching angle of each phase switch should be accurately controlled to stabilize torque and speed. However, as the speed of a motor increases, the switching angle is prone to deviate from a preset value. Because the accuracy of the switching angle largely depends on the resolution rate of the equipped encoder, which provides a digital controller with positional information of the rotor. It also relies on the sampling performance of the digital controller. To solve these problems, a new linear encoder is proposed. It consists of a chiaroscuro plate, phototransistors and a simple logic circuit. The resolution rate of the proposed encoder is sufficiently high owing to its inherent linear characteristic. It is, moreover, not affected
Fuel and Energy Abstracts November 2005
391
05/02677 Numerical study on NO formation in CH4-O2-N2 diffusion flame diluted with CO2 Hwang, D.-J. et al. International Journal of Energy Research, 2005, 29, (2), 107-120. Numerical study with momentum-balanced boundary conditions has been conducted to grasp chemical effects of added COz, to either fuelor oxidizer-side on flame structure and NO emission behaviour in CH4O2-N 2 diffusion flames. Cautious investigation is made for the comparison among the behaviours of principal chain branching and important H-removal key reactions. This describes successfully the reason why flame temperatures for fuel-side dilution are higher than those for oxidizer-side dilution. The role of the principal chain branching reaction is also recognized to be important even in the change of major flame structure caused by chemical effects. The importantly contributing reaction steps to NO production are examined. The reduced production rates of thermal NO and prompt NO due to chemical effects are much more remarkable for fuel-side dilution. It is atso found that the reaction step, H + NO + M = H N O + M plays a decisive role of the formation and destruction of prompt NO.
05/02678 Process modeling for control of a batch heat treatment furnace with low NOx radiant tube burner Tiwari, M. K. et al. Energy Conversion and Management, 2005, 46, (1314), 2093-2113. In this first part of a two-part problem, a process model for control of a batch-type heat treatment furnace with low NOx radiant tube burner has been developed. The model considers coupling between the different components and the wide variation in time scales of the processes involved. The heat transport between the gas stream and the radiant tube is modelled by a conjugate convectio~radiation mode using an empirical correlation for the convection and an optically thin radiation model. The combustion is considered in a highly preheated and diluted mode with single step modelling of the chemical kinetics. The heat transfer between the radiant tube and the load is considered to be only through radiation. The model is used in a companion paper to generate optimal operating conditions for the desired performance and emission characteristics.
05•02679 Pyrolysis of blends of different types of sewage sludge with one bituminous coal Folgueras, M. B. et al. Energy, 2005, 30, (7), 1079 1091. Pyrolysis of sewage sludge samples from three Asturian urban wastewater treatment plants was carried out. One high volatile bituminous coal and its blends with 10 and 50 wt% of sludge were studied by thermo-gravimetry. The same operational conditions (a constant heating rate of 10°C/min in the temperature range 25-800°C and a Na flow of 200 cm3/min) were maintained throughout. The results indicate that sludge is formed by two organic fractions with different reactivity, whose devolatilization processes partially overlap. Both fractions are more reactive than coal, since they decompose and devolatilize at temperatures lower than coal. Under oxidizing conditions, the action of oxygen during pyrolysis depends on the conditioning of sludge. If sludge is treated with FeC13, oxidative pyrolysis takes place. The behaviour of sludge-coal blends is intermediate between those of the coal and the corresponding sludge, without interactions between both blend components. In addition, a kinetic analysis was performed to fit thermo-gravimetric data, the global processes being considered as a series of consecutive first order reactions. A reasonable fit to the experimental data was obtained for all materials and their blends.
05/02680 Soot formation in inverse diffusion flames of diluted ethene Lee, E. J. et al. Fuel, 2005, 84, (5), 543-550. Experimental measurements of flame structure and soot characteristics were performed for ethene inverse diffusion flames (IDFs). IDFs are considered as an ideal flow field for studying incipient soot because the soot particles do not experience the oxidation process. In this study, an laser-induced fluorescence image clarified the reaction zone of IDFs with OH signal and polyeyclic aromatic hydrocarbon distribution. A
laser scattering technique also identified the soot particles. To address the degree of soot maturing, the carbon to hydrogen ratio and morphology of the soot sample were investigated. From the measurements, the effect of flow residence time and temperature on soot inception could be estimated, and more details on soot characteristics in the IDFs were determined according to the fuel dilution ratio and air/fuel ratio. Fuel dilution results in a decrease of temperature and an enhancement of residence time, but the critical dilution mole fraction is found for which temperature does not effect soot growth. Soot inception is also found to be weakly dependent on temperature as influenced by fuel dilution.
05/02681 Temperature and air-fuel ratio dependent specific heat ratio functions for lean burned and unburned mixture Ceviz, M. A. and Kaymaz, I Energy Conversion and Management, 2005, 46, (15 16), 2387 2404. The most important thermodynamic property used in heat release calculations for engines is the specific heat ratio. The functions proposed in the literature for the specific heat ratio are temperature dependent and apply at or near stoichiometric air-fuel ratios. However, the specific heat ratio is also influenced by the gas composition in the engine cylinder and especially becomes important for lean combustion engines. In this study, temperature and air-fuel ratio dependent specific heat ratio functions were derived to minimize the error by using an equilibrium combustion model for burned and unburned mixtures separately. After the error analysis between the equilibrium combustion model and the derived functions is presented, the results of the global specific heat ratio function, as varying with mass fraction burned, were compared with the proposed functions in the literature. The results of the study showed that the derived functions are more feasible at lean operating conditions of a spark ignition engine.
05102682 Transient development of methane-air diffusion flame in a confined geometry with and without air-preheat Mandal, B. K. et al. International Journal of Energy Research, 2005, 29, (2), 145-17. The transient development of a methane-air diffusion flame is studied numerically in the present work in a confined geometry. An explicit finite difference based numerical model is developed for the solution of transient reacting flow with varying thermodynamic and transport properties. The effect of air preheat on the flow and temperature fields at different time planes are studied by comparing two cases with air temperatures of 300 and 400 K, respectively. The preheating of air is found to complicate the flow situation with the formation of additional vortices. Thermal stratification in the flow causes a radial stretching of the flame, which is more evident with higher preheat temperature. In the absence of any preheating a stable re-circulation of ambient air is observed to extend from the exit plane into the domain adjacent to the wall. The mixing of ambient air results in gradual drooping in the bulk mean temperature of the flow. Such drooping nature in the bulk temperature distribution is not found with air preheat due to the absence of any stable re-circulation. The complication in the initial flow transients delays the attainment of steady situation for the flame with preheat.
l0
ENGINES Power generation and propulsion, electrical vehicles
05•02683 A linear encoder using a chiaroscuro and its extension to switched reluctance motor drive Kang, F.-S. and Park, S.-J. Energy Conversion and Management, 2005, 46, (7 8), 1119-1128. In switched reluctance motor drives, the on-off switching angle of each phase switch should be accurately controlled to stabilize torque and speed. However, as the speed of a motor increases, the switching angle is prone to deviate from a preset value. Because the accuracy of the switching angle largely depends on the resolution rate of the equipped encoder, which provides a digital controller with positional information of the rotor. It also relies on the sampling performance of the digital controller. To solve these problems, a new linear encoder is proposed. It consists of a chiaroscuro plate, phototransistors and a simple logic circuit. The resolution rate of the proposed encoder is sufficiently high owing to its inherent linear characteristic. It is, moreover, not affected
Fuel and Energy Abstracts November 2005
391