For capturing and recycling of CO2 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 techni...For capturing and recycling of CO2 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 CO2 from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system. The other part of CO2 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 CO2 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 CO2 for vehicular internal combustion engine.展开更多
Lifetime isone of the important indicators of automotive proton exchange membrane fuel cells. People used to evaluate the lifetime of vehicular fuel cells by laboratory tests or road tests that usually take thousands ...Lifetime isone of the important indicators of automotive proton exchange membrane fuel cells. People used to evaluate the lifetime of vehicular fuel cells by laboratory tests or road tests that usually take thousands hours even years. In order to achieve a rapid evaluation technique and to seek lifetime extension methods, a lifetime calculation formation was drawn out in consideration of the vehicle driving cycle and the working condition factors. Bench experiments were individually carried out on two fuel-cell stacks same as ones applied on vehicle, and the performance decay rates of the two stacks were obtained under four operation conditions of changing load cycle, start-stop cycle, idling and heavy load. As a result, the predicted lifetimes rather conform to the actual running status in road test. And the research on the fuel cell performance decay rates under different load conditions was also done. Consequently, an unexpected finding was discovered that operating under micro-current has an effect on recovering fuel cell performance. The vehicle fuel cell rapid assessment method only requires four laboratory tests of driving cycle, load cycle, idle operating conditions and heavy load conditions, and the whole process merely lasts less than 250 h. These experimental results can be used to predict the vehicular fuel cell lifetimes on various utility models or driving cycles, therefore to optimize the application model to prolong the fuel cell lifetime. Actually in the experiment, it has already been proved successfully that the fuel cell lifetime could be extended from 1 100 h to 2 600 h by optimizing operating mode. The quick evaluation method is helpful to develop extended life fuel cell and to deplete fuel cell for a longer time.展开更多
The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many rese...The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many researchers within the error range in the current computer speed. On the basis of the latest experimental results, TP （temperature phases） model is presented as a new soot model to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature and excess air factor are the most important two parameters in this model. When zone temperature T〈 1 500 K and excess air factor Ф〉0.6, only the soot precursors-- polycyclic aromatic hydrocarbons（PAH） is created and there is no soot emission. When zone temperature T ≥ 1 500 K and excess air factor Ф〈0.6, PAHs and soot source terms （particle inception, surface growth, oxidation, coagulation） are calculated. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. KIVA standard model and experimental data are analyzed for the results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP models. The experimental results indicate that the TP model can carry out optimization and computational fluid dynamics can be a tool to calculate for a high-pressure common rail directed injection diesel engine. The TP model result is closer than the use of the original KIVA-3V results of soot model accuracy by about 50% and TP model gives a new method for engine researchers.展开更多
The accelerated degradation in the front ceils of a polymer electrolyte membrane fuel cell（PEMFC） stack seriously reduces the reliability and durability of the whole stack. Most researches only focus on the size and...The accelerated degradation in the front ceils of a polymer electrolyte membrane fuel cell（PEMFC） stack seriously reduces the reliability and durability of the whole stack. Most researches only focus on the size and configuration of the gas intake manifold, which may lead to the maldistribution of flow and pressure. In order to find out the mechanisms of the accelerated degradation in the front cells, an extensive program of experimental and simulation work is initiated and the results are reported. It is found that after long-term lifetime tests the accelerated degradation in the front cells occurs in all three fuel cell stacks with different flow-fields under the U-type feed configuration. Compared with the rear cells of the stack, the voltage of the front cells is much lower at the same current densities and the membrane electrode assembly（MEA） has smaller active area, more catalyst particle agglomeration and higher ohmic impedance. For further investigation, a series of three dimensional isothermal numerical models are built to investigate the degradation mechanisms based on the experimental data. The simulation results reveal that the dry working condition of the membrane and the effect of high-speed gas scouting the MEA are the main causes of the accelerated degradation in the front cells of a PEM fuel cell stack under the U-type feed configuration. Several mitigation strategies that would mitigate these phenomena are presented： removing cells that have failed and replacing them with those of the same aging condition as the average of the stack; choosing a Z-type feed pattern instead of a U-type one; putting several air flow-field plates without MEA in the front of the stack; or exchanging the gas inlet and outlet alternately at a certain interval. This paper specifies the causes of the accelerated degradation in the front cells and provides the mitigation strategies.展开更多
文摘为研究进气相对湿度对燃料电池在不同工况(工作温度为70℃,进气相对湿度为40%和100%)下的影响,提出了进气加湿效率(Inlet Humidification Efficiency,IHE)模型。该模型将燃料电池总的水含量分为两部分:外部进气加湿携带的水和内部电化学反应生成的水,由此推导出进气加湿效率公式。建立几何模型并划分计算网格,将进气加湿效率模型导入计算流体动力学软件(Fluent)中进行计算。建立燃料电池测试系统,对工作温度为70℃,进气相对湿度分别为40%和100%的工况进行了试验。对IHE模型、Fluent模型和试验值进行比较分析,结果表明:当电池工作温度为70℃,电流密度为350 m A/cm2,进气相对湿度为100%时,IHE模型精确度比Fluent模型提高了37.4%;当进气相对湿度为40%时,进气加湿效率为34%。
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 CO2 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 CO2 from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system. The other part of CO2 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 CO2 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 CO2 for vehicular internal combustion engine.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2007AA05Z125)
文摘Lifetime isone of the important indicators of automotive proton exchange membrane fuel cells. People used to evaluate the lifetime of vehicular fuel cells by laboratory tests or road tests that usually take thousands hours even years. In order to achieve a rapid evaluation technique and to seek lifetime extension methods, a lifetime calculation formation was drawn out in consideration of the vehicle driving cycle and the working condition factors. Bench experiments were individually carried out on two fuel-cell stacks same as ones applied on vehicle, and the performance decay rates of the two stacks were obtained under four operation conditions of changing load cycle, start-stop cycle, idling and heavy load. As a result, the predicted lifetimes rather conform to the actual running status in road test. And the research on the fuel cell performance decay rates under different load conditions was also done. Consequently, an unexpected finding was discovered that operating under micro-current has an effect on recovering fuel cell performance. The vehicle fuel cell rapid assessment method only requires four laboratory tests of driving cycle, load cycle, idle operating conditions and heavy load conditions, and the whole process merely lasts less than 250 h. These experimental results can be used to predict the vehicular fuel cell lifetimes on various utility models or driving cycles, therefore to optimize the application model to prolong the fuel cell lifetime. Actually in the experiment, it has already been proved successfully that the fuel cell lifetime could be extended from 1 100 h to 2 600 h by optimizing operating mode. The quick evaluation method is helpful to develop extended life fuel cell and to deplete fuel cell for a longer time.
基金supportedd by National Natural Science Foundation of China (Grant No. 51176082)Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality, China (PHR (IHLB), Grant Nos. 201008370, 201106125)
文摘The existing soot models are either too complex and can not be applied to the internal combustion engine, or too simple to make calculation errors. Exploring the soot model becomes the pursuit of the goal of many researchers within the error range in the current computer speed. On the basis of the latest experimental results, TP （temperature phases） model is presented as a new soot model to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature and excess air factor are the most important two parameters in this model. When zone temperature T〈 1 500 K and excess air factor Ф〉0.6, only the soot precursors-- polycyclic aromatic hydrocarbons（PAH） is created and there is no soot emission. When zone temperature T ≥ 1 500 K and excess air factor Ф〈0.6, PAHs and soot source terms （particle inception, surface growth, oxidation, coagulation） are calculated. The TP model is then implemented in KIVA code instead of original model to carry out optimizing. KIVA standard model and experimental data are analyzed for the results of cylinder pressures, the corresponding heat release rates, and soot with variation of injection time, variation of rail pressure and variation of speed among TP models. The experimental results indicate that the TP model can carry out optimization and computational fluid dynamics can be a tool to calculate for a high-pressure common rail directed injection diesel engine. The TP model result is closer than the use of the original KIVA-3V results of soot model accuracy by about 50% and TP model gives a new method for engine researchers.
基金supported by National Basic Research Program of China(973 Program,Grant No.2012CB215500)National Hi-tech Research and Development Program of China(863 Program,Grant Nos.2012AA1106012,2012AA053402)+1 种基金National Natural Science Foundation of China(Grant No.20976095)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20090002110074)
文摘The accelerated degradation in the front ceils of a polymer electrolyte membrane fuel cell（PEMFC） stack seriously reduces the reliability and durability of the whole stack. Most researches only focus on the size and configuration of the gas intake manifold, which may lead to the maldistribution of flow and pressure. In order to find out the mechanisms of the accelerated degradation in the front cells, an extensive program of experimental and simulation work is initiated and the results are reported. It is found that after long-term lifetime tests the accelerated degradation in the front cells occurs in all three fuel cell stacks with different flow-fields under the U-type feed configuration. Compared with the rear cells of the stack, the voltage of the front cells is much lower at the same current densities and the membrane electrode assembly（MEA） has smaller active area, more catalyst particle agglomeration and higher ohmic impedance. For further investigation, a series of three dimensional isothermal numerical models are built to investigate the degradation mechanisms based on the experimental data. The simulation results reveal that the dry working condition of the membrane and the effect of high-speed gas scouting the MEA are the main causes of the accelerated degradation in the front cells of a PEM fuel cell stack under the U-type feed configuration. Several mitigation strategies that would mitigate these phenomena are presented： removing cells that have failed and replacing them with those of the same aging condition as the average of the stack; choosing a Z-type feed pattern instead of a U-type one; putting several air flow-field plates without MEA in the front of the stack; or exchanging the gas inlet and outlet alternately at a certain interval. This paper specifies the causes of the accelerated degradation in the front cells and provides the mitigation strategies.
