In the past decade,dry reforming of methane(DRM)has garnered increasing interest as it converts CH_(4)and CO_(2),two typical greenhouse gases,into synthesis gas(H_(2)and CO)for the production of high-value-added chemi...In the past decade,dry reforming of methane(DRM)has garnered increasing interest as it converts CH_(4)and CO_(2),two typical greenhouse gases,into synthesis gas(H_(2)and CO)for the production of high-value-added chemicals and fuels.Nickel-based DRM catalysts,renowned for their high activity and low cost,however,encounter challenges such as severe deactivation from sintering and carbon deposition.Herein,a surrounded NiO@NiAlO precursor derived from Ni(OH)_(2)nanosheets was modified at both the core and shell interfaces with MgO via wet impregnation.The obtained 0.8MgO^(WI)/Ni@NiAlO catalyst achieved a high CH_(4)reaction rate of~177 mmol gNi^(-1)min^(-1)and remained stable for 50 h at 600℃without coke formation.In sharp contrast,other Mg-doped catalysts(MgO modified the core or shell interfaces)and the catalyst without Mg-doping deactivated within 10 h due to coking or Ni particle sintering.The Ni/MgNiO_(2)interfaces and abundant oxygen vacancies(O_(v))generated by Mg-doping contributed to the outstanding resistance to sintering&coking as well as the superior activity and stability of the 0.8MgO^(WI)/Ni@NiAlO catalyst.In-situ investigation further unveiled the reaction mechanism:the activation of CO_(2)via adsorption on O_(v)generates active oxygen species(O^(*)),which reacts with CH_(x)^(*)intermediates formed by the dissociation of CH_(4)on Ni sites,yielding CO and H_(2).This work not only fabricates coke-free and high-stability Ni-based DRM catalysts via interface engineering but also provides insights and a new strategy for the design of high-efficiency and stable catalysts for DRM.展开更多
The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber ...The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling model.The accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust chamber.Additionally,key parameters related to heat transfer performance were calculated.The results demonstrate that the model is sufficiently accurate to be used as a preliminary design tool.The temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer analysis.In addition,the performance of composite cooling is observed to be superior to regenerative cooling.Increasing the gas film flow rate results in higher cooling efficiency and a lower gas-side wall temperature.Furthermore,the position at which the gas film is introduced greatly impacts the cooling performance.The optimal introduction position for the gas film is determined when the film is introduced from a single row of holes.This optimal introduction position results in a more uniform wall temperature distribution and reduces the peak temperature.Lastly,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall temperature.These results provide a basis for the design of gas film/regenerative composite cooling systems.展开更多
For capturing and recycling of CO_(2)in the internal combustion engine,Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techn...For capturing and recycling of CO_(2)in the internal combustion engine,Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techniques of spraying water in the cylinder and optimizing the ignition advance angle.However,due to the water spray nozzle need to be installed on the cylinder,which increases the cylinder head design difficulty and makes the combustion conditions become more complicated.In this paper,a new method is presented to carry out the closing inlet and exhaust system for internal combustion engines.The proposed new method uses liquid oxygen to solidify part of cooled CO_(2)from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system.The other part of CO_(2)is sent to inlet system and mixed with oxygen,which can reduce the oxygen-enriched combustion detonation tendency and make combustion stable.Computing grid of the IP52FMI single-cylinder four-stroke gasoline-engine is established according to the actual shape of the combustion chamber using KIVA-3V program.The effects of exhaust gas recirculation(EGR)rate are analyzed on the temperatures,the pressures and the instantaneous heat release rates when the EGR rate is more than 8%.The possibility of enclosing intake and exhaust system for engine is verified.The carbon dioxide trapping device is designed and the IP52FMI engine is transformed and the CO_(2)capture experiment is carried out.The experimental results show that when the EGR rate is 36%for the optimum EGR rate.When the liquid oxygen of 35.80-437.40 g is imported into the device and last 1-20 min,respectively,21.50-701.30 g dry ice is obtained.This research proposes a new design method which can capture CO_(2)for vehicular internal combustion engine.展开更多
Methane chemistry is one of the“Holy Grails of catalysis”.It is highly desirable but challenge to transform methane into value-added chemicals,because of its high C-H bonding energy(435 kJ/mol),lack ofπbonding or u...Methane chemistry is one of the“Holy Grails of catalysis”.It is highly desirable but challenge to transform methane into value-added chemicals,because of its high C-H bonding energy(435 kJ/mol),lack ofπbonding or unpaired electrons.Currently,commercial methane conversion is usually carried out in harsh conditions with enormous energy input.Photocatalytic partial oxidation of methane to liquid oxygenates(PPOMO)is a future-oriented technology towards realizing high efficiency and high selectivity under mild conditions.The selection of oxidant is crucial to the PPOMO performance.Hence,attentions are paid to the research progress of PPOMO with various oxidants(O_(2),H_(2)O,H_(2)O_(2)and other oxidants).Moreover,the activation of the selected oxidants is also highly emphasized.Meanwhile,we summarized the methane activation mechanisms focusing on the C-H bond that was broken mainly by·OH radical,O-specie or photogenerated hole(h+).Finally,the challenges and prospects in this subject are briefly discussed.展开更多
Combustion chamber modeling and simulation of the liquid propellant engine with kerosene as fuel and liquid oxygen as an oxidizer in the turbulent flow field are performed by CFD technique.The flow is modeled as Singl...Combustion chamber modeling and simulation of the liquid propellant engine with kerosene as fuel and liquid oxygen as an oxidizer in the turbulent flow field are performed by CFD technique.The flow is modeled as Single-phase in steady state and using RNG k-ε turbulence model.Simulation results are validated by experimental data of thrust,special impulse and combustion chamber pressure.By comparing t.^wo reaction models of finite rate chemistry and frozen model with experimental data,it is concluded that finite rate chemistry has acceptable results.The optimum value of equivalence ratio(oxidizer to fuel ratio)per reaction and operational parameters of the engine which maximize thrust and special impulse are determined.展开更多
为实现燃烧室组件的精确建模及其动力学特性的仿真研究,以零维时滞燃烧室模型为基础,考虑燃烧室内喷射、雾化、蒸发、混合、化学反应过程,采用针栓喷注器SMD(Sauter Mean Diameter,索特尔平均直径)经验关联式以及液滴高压蒸发理论对液氧...为实现燃烧室组件的精确建模及其动力学特性的仿真研究,以零维时滞燃烧室模型为基础,考虑燃烧室内喷射、雾化、蒸发、混合、化学反应过程,采用针栓喷注器SMD(Sauter Mean Diameter,索特尔平均直径)经验关联式以及液滴高压蒸发理论对液氧/甲烷推进剂组合的燃烧时滞进行求解,建立了基于液滴高压蒸发理论的变时滞燃烧室模型。基于1 kg/s级推力室开展热试车验证了变时滞燃烧室模型的准确性,结果表明:所建立的变时滞燃烧室模型可以较为准确地预测燃烧室的压力以及温度动态响应过程,与试验结果相比,稳态压力以及温度误差均在6%以内,压力参数动态响应时间的误差在14%以内,仿真结果具有较高的精度。基于变时滞燃烧室模型开展仿真研究,研究发现:液氧液滴初始粒径以及燃烧室温度作为影响液氧液滴寿命的主要因素,主导着液氧时滞的变化;变时滞模型可以根据工况参数动态计算推进剂燃烧时滞,启动初期喷注器雾化效果较差,液滴最大粒径达到800μm,且燃烧室温度低,进而导致燃烧时滞偏大,最大达到了1100 ms,约为稳定工作状态下燃烧时滞的40倍。本文所建立的变时滞燃烧室模型可根据工况参数对燃烧时滞进行动态计算,相较于传统时滞模型,其燃烧时滞的变化趋势更符合发动机实际工作过程,同时其室压的响应时间、稳态值也更接近实验值,该模型未来可为实际发动机时序设计等提供仿真支撑。展开更多
Combustion process inside kerosene-GOx rocket combustor with kerosene Alm cooling is studied,and a modeling approach is proposed.The paper suggests to use the Lagrangian particle tracking technique to model fuel film ...Combustion process inside kerosene-GOx rocket combustor with kerosene Alm cooling is studied,and a modeling approach is proposed.The paper suggests to use the Lagrangian particle tracking technique to model fuel film behavior while the continuous fluid is simulated via the Navier-Stokes system of Favre-averaged equations.The approach is validated over the 12 experimental regimes by the criterions of characteristic velocity and pressure,ence on the adiabatic wall temperatures and relatively low impact on the pressure.In general,phenomena,the calculation of operational processes becomes fast and robust yet precise en-the design process.展开更多
Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher perfo...Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher performance of a rocket engine. The theoretical model is complicated, it relates to fluiddynamics, heat transfer, combustion, etc... In this papers a regenerative cooling model is presented.Effects such as radiation, heat transfer to environment, variable thermal properties and coking areincluded in the model. This model can be applied to all kinds of liquid propellant rocket engines aswell as similar constructions. The modularized computer code is completed in the work.展开更多
文摘In the past decade,dry reforming of methane(DRM)has garnered increasing interest as it converts CH_(4)and CO_(2),two typical greenhouse gases,into synthesis gas(H_(2)and CO)for the production of high-value-added chemicals and fuels.Nickel-based DRM catalysts,renowned for their high activity and low cost,however,encounter challenges such as severe deactivation from sintering and carbon deposition.Herein,a surrounded NiO@NiAlO precursor derived from Ni(OH)_(2)nanosheets was modified at both the core and shell interfaces with MgO via wet impregnation.The obtained 0.8MgO^(WI)/Ni@NiAlO catalyst achieved a high CH_(4)reaction rate of~177 mmol gNi^(-1)min^(-1)and remained stable for 50 h at 600℃without coke formation.In sharp contrast,other Mg-doped catalysts(MgO modified the core or shell interfaces)and the catalyst without Mg-doping deactivated within 10 h due to coking or Ni particle sintering.The Ni/MgNiO_(2)interfaces and abundant oxygen vacancies(O_(v))generated by Mg-doping contributed to the outstanding resistance to sintering&coking as well as the superior activity and stability of the 0.8MgO^(WI)/Ni@NiAlO catalyst.In-situ investigation further unveiled the reaction mechanism:the activation of CO_(2)via adsorption on O_(v)generates active oxygen species(O^(*)),which reacts with CH_(x)^(*)intermediates formed by the dissociation of CH_(4)on Ni sites,yielding CO and H_(2).This work not only fabricates coke-free and high-stability Ni-based DRM catalysts via interface engineering but also provides insights and a new strategy for the design of high-efficiency and stable catalysts for DRM.
基金supported by the National Science Fund Project(No.2019-JCJQ-ZQ-019)the Innovative Research Group Project of National Natural Science Foundation of China(No.T2221002).
文摘The thermal protection of rocket engines is a crucial aspect of rocket engine design.In this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling model.The accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust chamber.Additionally,key parameters related to heat transfer performance were calculated.The results demonstrate that the model is sufficiently accurate to be used as a preliminary design tool.The temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer analysis.In addition,the performance of composite cooling is observed to be superior to regenerative cooling.Increasing the gas film flow rate results in higher cooling efficiency and a lower gas-side wall temperature.Furthermore,the position at which the gas film is introduced greatly impacts the cooling performance.The optimal introduction position for the gas film is determined when the film is introduced from a single row of holes.This optimal introduction position results in a more uniform wall temperature distribution and reduces the peak temperature.Lastly,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall temperature.These results provide a basis for the design of gas film/regenerative composite cooling systems.
基金Supported by National Natural Science Foundation of China(Grant No.51176082)Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions of China(Grant No.CIT&TCD20140311)Beijing Municipal Natural Science Foundation of China(Grant No.SQKZ201510016004)
文摘For capturing and recycling of CO_(2)in the internal combustion engine,Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techniques of spraying water in the cylinder and optimizing the ignition advance angle.However,due to the water spray nozzle need to be installed on the cylinder,which increases the cylinder head design difficulty and makes the combustion conditions become more complicated.In this paper,a new method is presented to carry out the closing inlet and exhaust system for internal combustion engines.The proposed new method uses liquid oxygen to solidify part of cooled CO_(2)from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system.The other part of CO_(2)is sent to inlet system and mixed with oxygen,which can reduce the oxygen-enriched combustion detonation tendency and make combustion stable.Computing grid of the IP52FMI single-cylinder four-stroke gasoline-engine is established according to the actual shape of the combustion chamber using KIVA-3V program.The effects of exhaust gas recirculation(EGR)rate are analyzed on the temperatures,the pressures and the instantaneous heat release rates when the EGR rate is more than 8%.The possibility of enclosing intake and exhaust system for engine is verified.The carbon dioxide trapping device is designed and the IP52FMI engine is transformed and the CO_(2)capture experiment is carried out.The experimental results show that when the EGR rate is 36%for the optimum EGR rate.When the liquid oxygen of 35.80-437.40 g is imported into the device and last 1-20 min,respectively,21.50-701.30 g dry ice is obtained.This research proposes a new design method which can capture CO_(2)for vehicular internal combustion engine.
基金the National Key R&D Program of China(No.2021YFA1500800)National Natural Science Foundation of China(No.22072106).
文摘Methane chemistry is one of the“Holy Grails of catalysis”.It is highly desirable but challenge to transform methane into value-added chemicals,because of its high C-H bonding energy(435 kJ/mol),lack ofπbonding or unpaired electrons.Currently,commercial methane conversion is usually carried out in harsh conditions with enormous energy input.Photocatalytic partial oxidation of methane to liquid oxygenates(PPOMO)is a future-oriented technology towards realizing high efficiency and high selectivity under mild conditions.The selection of oxidant is crucial to the PPOMO performance.Hence,attentions are paid to the research progress of PPOMO with various oxidants(O_(2),H_(2)O,H_(2)O_(2)and other oxidants).Moreover,the activation of the selected oxidants is also highly emphasized.Meanwhile,we summarized the methane activation mechanisms focusing on the C-H bond that was broken mainly by·OH radical,O-specie or photogenerated hole(h+).Finally,the challenges and prospects in this subject are briefly discussed.
文摘Combustion chamber modeling and simulation of the liquid propellant engine with kerosene as fuel and liquid oxygen as an oxidizer in the turbulent flow field are performed by CFD technique.The flow is modeled as Single-phase in steady state and using RNG k-ε turbulence model.Simulation results are validated by experimental data of thrust,special impulse and combustion chamber pressure.By comparing t.^wo reaction models of finite rate chemistry and frozen model with experimental data,it is concluded that finite rate chemistry has acceptable results.The optimum value of equivalence ratio(oxidizer to fuel ratio)per reaction and operational parameters of the engine which maximize thrust and special impulse are determined.
文摘为实现燃烧室组件的精确建模及其动力学特性的仿真研究,以零维时滞燃烧室模型为基础,考虑燃烧室内喷射、雾化、蒸发、混合、化学反应过程,采用针栓喷注器SMD(Sauter Mean Diameter,索特尔平均直径)经验关联式以及液滴高压蒸发理论对液氧/甲烷推进剂组合的燃烧时滞进行求解,建立了基于液滴高压蒸发理论的变时滞燃烧室模型。基于1 kg/s级推力室开展热试车验证了变时滞燃烧室模型的准确性,结果表明:所建立的变时滞燃烧室模型可以较为准确地预测燃烧室的压力以及温度动态响应过程,与试验结果相比,稳态压力以及温度误差均在6%以内,压力参数动态响应时间的误差在14%以内,仿真结果具有较高的精度。基于变时滞燃烧室模型开展仿真研究,研究发现:液氧液滴初始粒径以及燃烧室温度作为影响液氧液滴寿命的主要因素,主导着液氧时滞的变化;变时滞模型可以根据工况参数动态计算推进剂燃烧时滞,启动初期喷注器雾化效果较差,液滴最大粒径达到800μm,且燃烧室温度低,进而导致燃烧时滞偏大,最大达到了1100 ms,约为稳定工作状态下燃烧时滞的40倍。本文所建立的变时滞燃烧室模型可根据工况参数对燃烧时滞进行动态计算,相较于传统时滞模型,其燃烧时滞的变化趋势更符合发动机实际工作过程,同时其室压的响应时间、稳态值也更接近实验值,该模型未来可为实际发动机时序设计等提供仿真支撑。
基金Financial support was provided by the Russian Ministry of Education and Science(Project 13.7418.2017/8.9).
文摘Combustion process inside kerosene-GOx rocket combustor with kerosene Alm cooling is studied,and a modeling approach is proposed.The paper suggests to use the Lagrangian particle tracking technique to model fuel film behavior while the continuous fluid is simulated via the Navier-Stokes system of Favre-averaged equations.The approach is validated over the 12 experimental regimes by the criterions of characteristic velocity and pressure,ence on the adiabatic wall temperatures and relatively low impact on the pressure.In general,phenomena,the calculation of operational processes becomes fast and robust yet precise en-the design process.
文摘Heat transfer in the thrust chamber is of great importance in the design of liquid propellant rocketengines. Regenerative cooling is an advanced method which can ensure not only the proper runningbut also higher performance of a rocket engine. The theoretical model is complicated, it relates to fluiddynamics, heat transfer, combustion, etc... In this papers a regenerative cooling model is presented.Effects such as radiation, heat transfer to environment, variable thermal properties and coking areincluded in the model. This model can be applied to all kinds of liquid propellant rocket engines aswell as similar constructions. The modularized computer code is completed in the work.
