Gasification of biomass waste has a significant potential to reduce environmental impact and promote sustainability by producing syngas,which is considered as renewable energy.This work investigated the gasification o...Gasification of biomass waste has a significant potential to reduce environmental impact and promote sustainability by producing syngas,which is considered as renewable energy.This work investigated the gasification of macadamia nutshells in air-preheated,batch-fed fluidized bed gasifier.The study conducted a parametric analysis to assess the effect of equivalence ratio(ER)and air temperature on the gasifier temperature profile and its performance based on gas composition,higher heating value(HHV),and gas yield.The research was conducted within the range of 0.15-0.35 for the ER and 25-825℃ for the air temperature.Multi-objective numerical optimization was conducted using response surface methodology(RSM).From the parametric study,a distinct temperature profile was observed along the gasifier height,with the peak temperature near the top of the fluidized bed section and the lowest temperature at the top of the gasifier.Air preheating mostly favored gasification temperature at the lower part of the gasifier and showed rare significance at the top.No improvement in gasifier performance was observed beyond an air temperature of 620℃,which was identified as the ideal air-preheating temperature.Analysis of variance(ANOVA)revealed that the ER was the most influential parameter in the production of combustible gasses,syngas HHV and gas yield.Air preheating did not have a significant effect on methane production and gas yield.The most optimal values for ER and air temperature were obtained as 0.195℃ and 620℃,respectively,producing optimal values of 9.54,14.65%,2.03,4.02 MJ⋅Nm^(-3),and 1.82 Nm^(3)⋅kg^(-1) for hydrogen,carbon monoxide,methane,HHV,and gas yield,respectively.展开更多
In order to improve the cold start performance of heavy duty diesel engine, electronically controlling the preheating of intake air by flame was researched. According to simulation and thermodynamic analysis about th...In order to improve the cold start performance of heavy duty diesel engine, electronically controlling the preheating of intake air by flame was researched. According to simulation and thermodynamic analysis about the partial working processes of the diesel engine, the amount of heat energy, enough to make the fuel self ignite at the end of compression process at different temperatures of coolant and intake air, was calculated. Several HY20 preheating plugs were used to heat up the intake air. Meanwhile, an electronic control system based on 8 bit micro controller unit (MCS 8031) was designed to automatically control the process of heating intake air. According to the various temperatures of coolant and ambient air, one plug or two plugs can automatically be selected to heat intake air. The demo experiment validated that the total system could operate successfully and achieve the scheduled function.展开更多
Ammonium bisulfate(ABS)is a viscous compound produced by the escape NH_(3) in the NO reduction process and SO_(3) in the flue gas at a certain temperature,which can cause the ash corrosion of the air preheater in coal...Ammonium bisulfate(ABS)is a viscous compound produced by the escape NH_(3) in the NO reduction process and SO_(3) in the flue gas at a certain temperature,which can cause the ash corrosion of the air preheater in coal-fired power plants.Therefore,it is essential to study the formation temperature of ABS to prevent the deposition of ABS in air preheaters.In this paper,the SO_(3) reaction kinetic model is used to analyze the SO_(3) generation process from coal combustion to the selective catalytic reduction(SCR)exit stage,and the kinetic model of NO reduction is used to analyze the NH_(3) escape process.A prediction model for calculating the ABS formation temperature based on the S content in coal and NO reduction parameters of the SCR is proposed,solving the difficulty of measuring SO_(3) concentration and NH_(3) concentration in the previous calculation equation of ABS formation temperature.And the reliability of the model is verified by the actual data of the power plant.Then the influence of S content in coal,NH_(3)/NO_(x) molar ratio,different NO_(x) concentrations at SCR inlet,and NO removal efficiency on the formation temperature of ABS are analyzed.展开更多
In this paper the premixed catalytic combustion emissions such as CO, unburned hydrocarbon (UHC), NOx and the temperature distribution in the catalytic monolith with ultra low concentration of Pd were studied. Three t...In this paper the premixed catalytic combustion emissions such as CO, unburned hydrocarbon (UHC), NOx and the temperature distribution in the catalytic monolith with ultra low concentration of Pd were studied. Three types of monoliths were used for experiments and the temperature of preheated air was respectively 50℃ , 100℃ and 200℃ . The results showed that preheated air made radial temperature in the catalytic monolith uniform which helped to avoid local hot spots so as to decrease NOx emission. The experiment also proved that the shorter monolith showed much better catalytic combustion performance than longer one and the temperature at the exit of the shorter monolith was relatively lower. On the contrary, the temperature was higher in the longer monolith and the lethal NOx emission was slightly increased.展开更多
An experimental study on heat transfer and resistance coefficients of linearly arranged smooth and spirally corrugated tube bundles in cross-flow was performed. The heat transfer and resistance coefficients are presen...An experimental study on heat transfer and resistance coefficients of linearly arranged smooth and spirally corrugated tube bundles in cross-flow was performed. The heat transfer and resistance coefficients are presented in this paper with transverse and longitudinal tube-pitch and tube geometries taken into account. The experiment's results can provide technical guidelines for application to horizontal air preheater with arranged in-line spirally corrugated tube bundles, especially to the air preheater for CFBCBs (Circulating Fluidized Bed Combustion Boilers).展开更多
This numerical study investigates the effects of using a diluted fuel （50% natural gas and 50% N2） in an industrial furnace under several cases of conventional combustion （air with 21% O2 at 300 and 1273 K） and th...This numerical study investigates the effects of using a diluted fuel （50% natural gas and 50% N2） in an industrial furnace under several cases of conventional combustion （air with 21% O2 at 300 and 1273 K） and the highly preheated and diluted air （1273 K with 10% O2 and 90% N2） combustion （HPDAC） conditions using an in-house computer program. It was found that by applying a combined diluted fuel and oxidant instead of their uncombined and/or undiluted states, the best condition is obtained for the establishment of HPDAC＇s main unique features. These features are low mean and maximum gas temperature and high radiation/total heat transfer to gas and tubes; as well as more uniformity of theirs distributions which results in decrease in NOx pollutant formation and increase in furnace efficiency or energy saving. Moreover, a variety of chemical flame shape, the process fluid and tubes walls temperatures profiles, the required regenerator efficiency and finally the concentration and velocity patterns have been also qualitatively/quantitatively studied.展开更多
Based on the local blockage of air preheater of #4 boiler and its influence on boiler combustion, the paper analyzes the causes of local blockage of air preheater and adopts necessary countermeasures and treatment met...Based on the local blockage of air preheater of #4 boiler and its influence on boiler combustion, the paper analyzes the causes of local blockage of air preheater and adopts necessary countermeasures and treatment methods to slow down the aggravation of local blockage of air preheater and ensure the safe operation of boiler. During the subsequent overhaul of Unit #4, on-site inspection shall be conducted on the corrosion and damage of the air preheater heat exchange elements, and the processes such as repair of the air preheater flexible seal, cleaning of heat exchange elements, modification of flue gas deflector at the inlet of denitration reaction zone, and replacement of denitration catalyst shall be followed throughout. After the overhaul of Unit #4, tests such as ammonia injection leveling optimization and ammonia escape rate at denitration outlet were conducted. Through the collection, comparison and analysis of a large amount of data during the test period, the experience is summarized and detailed measures are formulated to avoid the recurrence of air preheater blockage.展开更多
Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, La...Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, Laser-Induced Incandescence (LII) has been increasingly applied for soot concentration quantification in various combustion environments such as laminar flame, vehicle exhaust, internal combustion chamber as well as aero-engine combustor. In this work, we experimentally measured the spatial and temporal distribution of SVF using two-color LII technique at the outlet of a single-sector dual-swirl aero-engine model combustor. The effect of inlet pressure and air preheat temperature on the SVF distribution was separately investigated within a pressure range of 241–425 kPa and a temperature range of 292–500 K. The results show that soot production increases with the inlet pressure but generally decreases with the air preheat temperature. Qualitative analysis was provided to explain the above results of parametric studies. The LII experiments were also conducted under 3 designed conditions to evaluate soot emission under practical operations. Particularly, weak soot emission was detected at the outlet under the idle condition. Our experimental results provide a valuable benchmark for evaluating soot emission in the exhaust plume of this aero-engine combustor during practical operations.展开更多
In Shougang Jingtang 5500m 3 huge blast furnace(BF)design,dome combustion hot blast stove(DCHBS)technology is developed.DCHBS process is optimized and integrated,and reasonable hot blast stove(HBS)technical parameters...In Shougang Jingtang 5500m 3 huge blast furnace(BF)design,dome combustion hot blast stove(DCHBS)technology is developed.DCHBS process is optimized and integrated,and reasonable hot blast stove(HBS)technical parameters are determined.Mathematic model is established and adopted by computational fluid dynamics(CFD).The transmission theory is studied for hot blast stove combustion and gas flow,and distribution results of HBS velocity field,CO density field and temperature field are achieved.Physical test model and hot trail unit are established,and the numeral calculation result is verified through test and investigation.3-D simulation design is adopted.HBS process flow and process layout are optimized and designed.Combustion air two-stage high temperature preheating technology is designed and developed.Two sets of small size DCHBSs are adopted to preheat the combustion air to 520-600℃.With the precondition of BF gas combustion,the hot blast stove dome temperature can exceed 1420℃.According to DCHBS technical features,reasonable refractory structure is designed.Effective technical measures are adopted to prevent hot blast stove shell intercrystalline stress corrosion.Hot blast stove hot pipe and lining system are optimized and designed.After blowing in,the blast temperature keeps increasing,and the monthly average blast temperature reaches 1300℃when burning single BF gas.展开更多
In the production process of thermal power plant, high-pressure heater (abbreviated as Gaojia) is one of the most important auxiliary equipment of steam turbine. If shutdown occurs due to high-pressure heater fault, f...In the production process of thermal power plant, high-pressure heater (abbreviated as Gaojia) is one of the most important auxiliary equipment of steam turbine. If shutdown occurs due to high-pressure heater fault, feedwater can only enter boiler through bypass pipe, which will greatly reduce feedwater temperature entering boiler, thus increasing fuel consumption, increasing power generation cost and reducing economy. When the temperature of feedwater entering the boiler is lowered, the heat absorption of water in the boiler is increased. Compared with the decrease of heat load evaporation in the furnace, the steam is heated and increased in the boiler superheater, causing the temperature of superheated steam and the temperature of the pipe wall to increase. In severe cases, the superheater may be burnt out;In addition, the shutdown of the high-pressure heater will also cause the flue gas temperature at the inlet and outlet of the air preheater to decrease, which will easily lead to the decrease of the activity of the denitration catalyst and the blockage of the heat exchange elements of the air preheater.展开更多
Ammonia is a suitable carbon-free alternative fuel for power equipment.Direct combustion of liquid ammonia has the potential to reduce system costs and heat loss of gas turbine(GT).However,its tendency to flash and th...Ammonia is a suitable carbon-free alternative fuel for power equipment.Direct combustion of liquid ammonia has the potential to reduce system costs and heat loss of gas turbine(GT).However,its tendency to flash and the high latent heat of vaporization can lead to combustion deterioration.Previous research suggests that stabilizing a liquid ammonia flame requires swirling and preheated air.So far,the influencemechanism of preheated air on liquid ammonia swirl spray remains inadequately explored.To fill this research gap,this study conducted a large eddy simulation(LES)to investigate the effect of preheated air temperature(T_(a))on a liquid ammonia flash spray in a swirl combustor.The influence of T_(a) on the spray morphology and the axial velocity,diameter,and temperature distributions of the droplets were investigated to understand the spray characteristics.Besides,the effects of T_(a) on the evaporation characteristics,the properties,and the possible ignition performance of themixture were studied.The results show that with the increase of T_(a),the heating capacity of air is enhanced,leading to a greater proportion of droplets reaching flash boiling conditions.This greatly optimizes the evaporation process,resulting in more complete evaporation and significantly smaller volume.The bulk air flow velocity is increased,causing the expansion of the inner recirculation zone(IRZ),and the gaseous temperature and mixture concentration distribution are optimized.In addition,the low gaseous ammonia concentration makes ignition difficulty at T_(a)=300 K.The high|τ|value(τis the shear stress)and large inner recirculation zone area lead to a larger RegionM and a smaller RegionL at T_(a)=300 K compared to the case of T_(a)=500 K.展开更多
The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature trans-fer matrix was obtained for the air preheater that comprises several discrete heat transfer units with ...The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature trans-fer matrix was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could be easily calculated for a given air preheater and inlet fluid temperatures. The active length of condenser in a variable conductance heat pipe is determined according to the flat interface model. With the same initial conditions, the comparisons between variable conductance heat-pipe air preheater and regular heat pipe air preheater has been analyzed and tested in terms of heat pipe wall temperature, heat transfer surface area and outlet fluid temperatures. Based on the real industrial applications, it has been confirmed that the variable conductance heat pipe air preheater has excellent performance of anti-corrosion and anti-ash-deposition especially at the variable working condition and the sulfur coal (5%-6% mass fraction of sulfur) condition.展开更多
Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks,owing to its use of mature technologies and low cost per unit...Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks,owing to its use of mature technologies and low cost per unit of storage capacity.Adiabatic compressed air energy storage(A-CAES)systems typically compress air from ambient temperature in the charge phase and expand the air back to ambient temperature in the discharge phase.This papers explores the use of an innovative operating scheme for an A-CAES system aimed at lowering the total cost of the system for a given exergy storage capacity.The configuration proposed considers preheating of the air before compression which increases the fraction of the total exergy that is stored in the fom of high-grade heat in comparison to existing designs in which the main exergy storage medium is the compressed air itself.Storing a high fraction of the total exergy as heat allows reducing the capacity of costly pressure stores in the system and replacing it with cheaper thermal energy stores.Additionally,a configuration that integrates a system based on the aforementioned concept with solar thermal power or low-medium grade waste heat is introduced and thoroughly discussed.展开更多
基金supported in part by German Academic Exchange Service(DAAD)Japan International Cooperation Agency(JICA)through AFRICA-ai-JAPAN Project.
文摘Gasification of biomass waste has a significant potential to reduce environmental impact and promote sustainability by producing syngas,which is considered as renewable energy.This work investigated the gasification of macadamia nutshells in air-preheated,batch-fed fluidized bed gasifier.The study conducted a parametric analysis to assess the effect of equivalence ratio(ER)and air temperature on the gasifier temperature profile and its performance based on gas composition,higher heating value(HHV),and gas yield.The research was conducted within the range of 0.15-0.35 for the ER and 25-825℃ for the air temperature.Multi-objective numerical optimization was conducted using response surface methodology(RSM).From the parametric study,a distinct temperature profile was observed along the gasifier height,with the peak temperature near the top of the fluidized bed section and the lowest temperature at the top of the gasifier.Air preheating mostly favored gasification temperature at the lower part of the gasifier and showed rare significance at the top.No improvement in gasifier performance was observed beyond an air temperature of 620℃,which was identified as the ideal air-preheating temperature.Analysis of variance(ANOVA)revealed that the ER was the most influential parameter in the production of combustible gasses,syngas HHV and gas yield.Air preheating did not have a significant effect on methane production and gas yield.The most optimal values for ER and air temperature were obtained as 0.195℃ and 620℃,respectively,producing optimal values of 9.54,14.65%,2.03,4.02 MJ⋅Nm^(-3),and 1.82 Nm^(3)⋅kg^(-1) for hydrogen,carbon monoxide,methane,HHV,and gas yield,respectively.
文摘In order to improve the cold start performance of heavy duty diesel engine, electronically controlling the preheating of intake air by flame was researched. According to simulation and thermodynamic analysis about the partial working processes of the diesel engine, the amount of heat energy, enough to make the fuel self ignite at the end of compression process at different temperatures of coolant and intake air, was calculated. Several HY20 preheating plugs were used to heat up the intake air. Meanwhile, an electronic control system based on 8 bit micro controller unit (MCS 8031) was designed to automatically control the process of heating intake air. According to the various temperatures of coolant and ambient air, one plug or two plugs can automatically be selected to heat intake air. The demo experiment validated that the total system could operate successfully and achieve the scheduled function.
基金the Key Research and Development Plan of Shandong Province (2019GSF109004)Natural Science Foundation of Shandong Province (ZR2020ME190) for funding and supporting this work
文摘Ammonium bisulfate(ABS)is a viscous compound produced by the escape NH_(3) in the NO reduction process and SO_(3) in the flue gas at a certain temperature,which can cause the ash corrosion of the air preheater in coal-fired power plants.Therefore,it is essential to study the formation temperature of ABS to prevent the deposition of ABS in air preheaters.In this paper,the SO_(3) reaction kinetic model is used to analyze the SO_(3) generation process from coal combustion to the selective catalytic reduction(SCR)exit stage,and the kinetic model of NO reduction is used to analyze the NH_(3) escape process.A prediction model for calculating the ABS formation temperature based on the S content in coal and NO reduction parameters of the SCR is proposed,solving the difficulty of measuring SO_(3) concentration and NH_(3) concentration in the previous calculation equation of ABS formation temperature.And the reliability of the model is verified by the actual data of the power plant.Then the influence of S content in coal,NH_(3)/NO_(x) molar ratio,different NO_(x) concentrations at SCR inlet,and NO removal efficiency on the formation temperature of ABS are analyzed.
基金Supported by the Key Project of the National 973 Program of China (No.2005CB724201)the Natural Science Foundation ofBeijing (No.06C0002)the Beijing Education Commission Key Laboratory of Heat Transfer and Energy Conversion Fund(No.05005790200406).
文摘In this paper the premixed catalytic combustion emissions such as CO, unburned hydrocarbon (UHC), NOx and the temperature distribution in the catalytic monolith with ultra low concentration of Pd were studied. Three types of monoliths were used for experiments and the temperature of preheated air was respectively 50℃ , 100℃ and 200℃ . The results showed that preheated air made radial temperature in the catalytic monolith uniform which helped to avoid local hot spots so as to decrease NOx emission. The experiment also proved that the shorter monolith showed much better catalytic combustion performance than longer one and the temperature at the exit of the shorter monolith was relatively lower. On the contrary, the temperature was higher in the longer monolith and the lethal NOx emission was slightly increased.
文摘An experimental study on heat transfer and resistance coefficients of linearly arranged smooth and spirally corrugated tube bundles in cross-flow was performed. The heat transfer and resistance coefficients are presented in this paper with transverse and longitudinal tube-pitch and tube geometries taken into account. The experiment's results can provide technical guidelines for application to horizontal air preheater with arranged in-line spirally corrugated tube bundles, especially to the air preheater for CFBCBs (Circulating Fluidized Bed Combustion Boilers).
基金Supported by the National Iranian Oil Company (NIOC)
文摘This numerical study investigates the effects of using a diluted fuel （50% natural gas and 50% N2） in an industrial furnace under several cases of conventional combustion （air with 21% O2 at 300 and 1273 K） and the highly preheated and diluted air （1273 K with 10% O2 and 90% N2） combustion （HPDAC） conditions using an in-house computer program. It was found that by applying a combined diluted fuel and oxidant instead of their uncombined and/or undiluted states, the best condition is obtained for the establishment of HPDAC＇s main unique features. These features are low mean and maximum gas temperature and high radiation/total heat transfer to gas and tubes; as well as more uniformity of theirs distributions which results in decrease in NOx pollutant formation and increase in furnace efficiency or energy saving. Moreover, a variety of chemical flame shape, the process fluid and tubes walls temperatures profiles, the required regenerator efficiency and finally the concentration and velocity patterns have been also qualitatively/quantitatively studied.
文摘Based on the local blockage of air preheater of #4 boiler and its influence on boiler combustion, the paper analyzes the causes of local blockage of air preheater and adopts necessary countermeasures and treatment methods to slow down the aggravation of local blockage of air preheater and ensure the safe operation of boiler. During the subsequent overhaul of Unit #4, on-site inspection shall be conducted on the corrosion and damage of the air preheater heat exchange elements, and the processes such as repair of the air preheater flexible seal, cleaning of heat exchange elements, modification of flue gas deflector at the inlet of denitration reaction zone, and replacement of denitration catalyst shall be followed throughout. After the overhaul of Unit #4, tests such as ammonia injection leveling optimization and ammonia escape rate at denitration outlet were conducted. Through the collection, comparison and analysis of a large amount of data during the test period, the experience is summarized and detailed measures are formulated to avoid the recurrence of air preheater blockage.
基金supported by the National Key Research and Development Program of China(No.2020YFA0405700).
文摘Quantitative measurement of Soot Volume Fraction (SVF) is an essential prerequisite for controlling soot particle emissions from aero-engine combustors. As an in-situ and non-intrusive optical diagnostic technique, Laser-Induced Incandescence (LII) has been increasingly applied for soot concentration quantification in various combustion environments such as laminar flame, vehicle exhaust, internal combustion chamber as well as aero-engine combustor. In this work, we experimentally measured the spatial and temporal distribution of SVF using two-color LII technique at the outlet of a single-sector dual-swirl aero-engine model combustor. The effect of inlet pressure and air preheat temperature on the SVF distribution was separately investigated within a pressure range of 241–425 kPa and a temperature range of 292–500 K. The results show that soot production increases with the inlet pressure but generally decreases with the air preheat temperature. Qualitative analysis was provided to explain the above results of parametric studies. The LII experiments were also conducted under 3 designed conditions to evaluate soot emission under practical operations. Particularly, weak soot emission was detected at the outlet under the idle condition. Our experimental results provide a valuable benchmark for evaluating soot emission in the exhaust plume of this aero-engine combustor during practical operations.
文摘In Shougang Jingtang 5500m 3 huge blast furnace(BF)design,dome combustion hot blast stove(DCHBS)technology is developed.DCHBS process is optimized and integrated,and reasonable hot blast stove(HBS)technical parameters are determined.Mathematic model is established and adopted by computational fluid dynamics(CFD).The transmission theory is studied for hot blast stove combustion and gas flow,and distribution results of HBS velocity field,CO density field and temperature field are achieved.Physical test model and hot trail unit are established,and the numeral calculation result is verified through test and investigation.3-D simulation design is adopted.HBS process flow and process layout are optimized and designed.Combustion air two-stage high temperature preheating technology is designed and developed.Two sets of small size DCHBSs are adopted to preheat the combustion air to 520-600℃.With the precondition of BF gas combustion,the hot blast stove dome temperature can exceed 1420℃.According to DCHBS technical features,reasonable refractory structure is designed.Effective technical measures are adopted to prevent hot blast stove shell intercrystalline stress corrosion.Hot blast stove hot pipe and lining system are optimized and designed.After blowing in,the blast temperature keeps increasing,and the monthly average blast temperature reaches 1300℃when burning single BF gas.
文摘In the production process of thermal power plant, high-pressure heater (abbreviated as Gaojia) is one of the most important auxiliary equipment of steam turbine. If shutdown occurs due to high-pressure heater fault, feedwater can only enter boiler through bypass pipe, which will greatly reduce feedwater temperature entering boiler, thus increasing fuel consumption, increasing power generation cost and reducing economy. When the temperature of feedwater entering the boiler is lowered, the heat absorption of water in the boiler is increased. Compared with the decrease of heat load evaporation in the furnace, the steam is heated and increased in the boiler superheater, causing the temperature of superheated steam and the temperature of the pipe wall to increase. In severe cases, the superheater may be burnt out;In addition, the shutdown of the high-pressure heater will also cause the flue gas temperature at the inlet and outlet of the air preheater to decrease, which will easily lead to the decrease of the activity of the denitration catalyst and the blockage of the heat exchange elements of the air preheater.
基金National Natural Science Foundation of China,Grant/Award Number:52176130Open Research Fund of Beijing Key Laboratory of Powertrain for New Energy Vehicle,Beijing Jiaotong University。
文摘Ammonia is a suitable carbon-free alternative fuel for power equipment.Direct combustion of liquid ammonia has the potential to reduce system costs and heat loss of gas turbine(GT).However,its tendency to flash and the high latent heat of vaporization can lead to combustion deterioration.Previous research suggests that stabilizing a liquid ammonia flame requires swirling and preheated air.So far,the influencemechanism of preheated air on liquid ammonia swirl spray remains inadequately explored.To fill this research gap,this study conducted a large eddy simulation(LES)to investigate the effect of preheated air temperature(T_(a))on a liquid ammonia flash spray in a swirl combustor.The influence of T_(a) on the spray morphology and the axial velocity,diameter,and temperature distributions of the droplets were investigated to understand the spray characteristics.Besides,the effects of T_(a) on the evaporation characteristics,the properties,and the possible ignition performance of themixture were studied.The results show that with the increase of T_(a),the heating capacity of air is enhanced,leading to a greater proportion of droplets reaching flash boiling conditions.This greatly optimizes the evaporation process,resulting in more complete evaporation and significantly smaller volume.The bulk air flow velocity is increased,causing the expansion of the inner recirculation zone(IRZ),and the gaseous temperature and mixture concentration distribution are optimized.In addition,the low gaseous ammonia concentration makes ignition difficulty at T_(a)=300 K.The high|τ|value(τis the shear stress)and large inner recirculation zone area lead to a larger RegionM and a smaller RegionL at T_(a)=300 K compared to the case of T_(a)=500 K.
文摘The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature trans-fer matrix was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could be easily calculated for a given air preheater and inlet fluid temperatures. The active length of condenser in a variable conductance heat pipe is determined according to the flat interface model. With the same initial conditions, the comparisons between variable conductance heat-pipe air preheater and regular heat pipe air preheater has been analyzed and tested in terms of heat pipe wall temperature, heat transfer surface area and outlet fluid temperatures. Based on the real industrial applications, it has been confirmed that the variable conductance heat pipe air preheater has excellent performance of anti-corrosion and anti-ash-deposition especially at the variable working condition and the sulfur coal (5%-6% mass fraction of sulfur) condition.
基金This work has been supported by the UK Engineering and Physical Sciences Research Council(EPSRC)through the NexGen-TEST(EP/LO14211/1),IMAGES(EP/K002228/1)and RESTLESS(EP/N001893/1)projects.
文摘Compressed air energy storage is an energy storage technology with strong potential to play a significant role in balancing energy on transmission networks,owing to its use of mature technologies and low cost per unit of storage capacity.Adiabatic compressed air energy storage(A-CAES)systems typically compress air from ambient temperature in the charge phase and expand the air back to ambient temperature in the discharge phase.This papers explores the use of an innovative operating scheme for an A-CAES system aimed at lowering the total cost of the system for a given exergy storage capacity.The configuration proposed considers preheating of the air before compression which increases the fraction of the total exergy that is stored in the fom of high-grade heat in comparison to existing designs in which the main exergy storage medium is the compressed air itself.Storing a high fraction of the total exergy as heat allows reducing the capacity of costly pressure stores in the system and replacing it with cheaper thermal energy stores.Additionally,a configuration that integrates a system based on the aforementioned concept with solar thermal power or low-medium grade waste heat is introduced and thoroughly discussed.
