为有效地控制发动机燃烧噪声和活塞敲击噪声,研究了振动噪声的产生机理,指出了发动机振动传递的基本途径。通过对发动机结构的传递函数试验发现,由燃烧气体力所引起结构表面的响应主要是通过内部传力部件进行,频谱特性呈宽带凸峰特性,...为有效地控制发动机燃烧噪声和活塞敲击噪声,研究了振动噪声的产生机理,指出了发动机振动传递的基本途径。通过对发动机结构的传递函数试验发现,由燃烧气体力所引起结构表面的响应主要是通过内部传力部件进行,频谱特性呈宽带凸峰特性,而通过敲击缸盖和缸孔引起的振动响应主要发生在2 000 H z以上频段,频谱成尖峰特性,且结构模态效应突出。结合试验结果,最后提出了控制发动机燃烧噪声和活塞拍击噪声的方向,为改进设计提供了参考。展开更多
With the large-scale mining of coal resources,the huge economic losses and environmental problems caused by underground coal fires have become increasingly prominent,and the research on the status quo and response str...With the large-scale mining of coal resources,the huge economic losses and environmental problems caused by underground coal fires have become increasingly prominent,and the research on the status quo and response strategies of underground coal fires is of great significance to accelerate the green prevention and control of coal fires,energy conservation and emission reduction.In this paper,we summarized and sorted out the research status of underground coal fires,focused on the theoretical and technical issues such as underground coal fire combustion mechanism,multiphysics coupling effect of coal fire combustion,fire prevention and extinguishing technology for underground coal fires,and beneficial utilization technology,and described the latest research progress of the prevention and control for underground coal fire hazards.Finally,the key research problems in the field of underground coal fire hazards prevention and control were proposed in the direction of the basic theory,technology research,comprehensive management and utilization,with a view to providing ideas and solutions for the management of underground coal fires.展开更多
采用浸渍法制备CeO_2负载的Co_3O_4催化剂粉末,将催化剂粉末制作了厚膜型催化燃烧式甲烷气体传感器进行测试,讨论不同钴负载量对甲烷催化的影响,重点研究了不同钴负载量对传感器稳定性的影响,通过SEM、TPR、XRD和BET对催化剂进行分析表...采用浸渍法制备CeO_2负载的Co_3O_4催化剂粉末,将催化剂粉末制作了厚膜型催化燃烧式甲烷气体传感器进行测试,讨论不同钴负载量对甲烷催化的影响,重点研究了不同钴负载量对传感器稳定性的影响,通过SEM、TPR、XRD和BET对催化剂进行分析表征。实验结果显示,Co_3O_4/CeO_2催化剂对甲烷有较好的催化特性,Co_3O_4质量分数为30%时的催化剂制备的传感器对甲烷气体(体积分数2%)响应达到19 m V,且在高温环境下传感器响应能力保持稳定,550℃连续工作6 h响应值仅下降0.2 m V。分析催化剂高温处理前后结果,证实传感器失效是由催化剂失效所导致。展开更多
Natural aluminum particles have the core-shell structure.The structure response refers to the mechanical behavior of the aluminum particle structure caused by external influences.The dynamic behavior of the structural...Natural aluminum particles have the core-shell structure.The structure response refers to the mechanical behavior of the aluminum particle structure caused by external influences.The dynamic behavior of the structural response of aluminum core-shell particles before combustion is of great importance for the aluminum powder burning mechanism and its applications.In this paper,an aluminum particle combustion experiment in a detonation environment is conducted and analyzed;the breakage factors of aluminum particles shell in detonation environment are analyzed.The experiment results show that the aluminum particle burns in a gaseous state and condenses into a sub-micron particle cluster.The calculation and simulation demonstrate that the rupture of aluminum particle shell in the detonation environment is mainly caused by the impact of the detonation wave.The detonation wave impacts the aluminum particles,resulting in shell cracking,and due to the shrinkage-expansion of the aluminum core and stripping of the detonation product,the cracked shell is fractured and peeled with the aluminum reacting with the detonation product.展开更多
The effect of upstream velocity pertuibations on the response of a premixed flame was investigated in terms of the flame transfer function dependency on excitation frequency.In this study,the assumption of constant fl...The effect of upstream velocity pertuibations on the response of a premixed flame was investigated in terms of the flame transfer function dependency on excitation frequency.In this study,the assumption of constant flame speed was extended and the effect of flame speed development was considered;i.e.,the flame speed would grow with the time after ignition or with the distance from a flame-holder.In the present study,the kinematics of a conical flame was investigated by linearization of the front tracking equation of flame to uniform and convected fluctuations of the flow velocity and the response was compared with that of a V-shaped flame and the experimental data in the previous studies.The results show that the effect of flame speed development could influence a decreasing gain and increase the phase of the flame response to the uniform velocity oscillations in low and moderate frequencies.Comparing the variations in the gain of flame response upon normalized frequency,show that a conical flame has lower values than the V-flame.In other woods,these flames might be less susceptible to combustion instabilities than the V-flames.Furthennore,the variations in phase of the V-flames responses,which show a quasi-linear behavior with normalized frequency,have higher values than the saturated behavior in phase of the conical flame responses.Also,considering that the flame speed development induces an increase in the gain and phase of the conical flame response to the convected velocity oscillations in certain frequencies;because the developed flame front has longer length in comparison to the flame front in constant flame speed model.Therefore,the flame length may be longer than convective wavelength and the heat release would be generated in different points of the flame;consequently the flow oscillations might exert a stronger impact on the unsteady heat release fluctuations.展开更多
文摘为有效地控制发动机燃烧噪声和活塞敲击噪声,研究了振动噪声的产生机理,指出了发动机振动传递的基本途径。通过对发动机结构的传递函数试验发现,由燃烧气体力所引起结构表面的响应主要是通过内部传力部件进行,频谱特性呈宽带凸峰特性,而通过敲击缸盖和缸孔引起的振动响应主要发生在2 000 H z以上频段,频谱成尖峰特性,且结构模态效应突出。结合试验结果,最后提出了控制发动机燃烧噪声和活塞拍击噪声的方向,为改进设计提供了参考。
基金supported by the National Natural Science Foundation of China (52174229)the Natural Science Foundation of Liaoning Province (2021-KF-23-01),for which the authors are very thankful.
文摘With the large-scale mining of coal resources,the huge economic losses and environmental problems caused by underground coal fires have become increasingly prominent,and the research on the status quo and response strategies of underground coal fires is of great significance to accelerate the green prevention and control of coal fires,energy conservation and emission reduction.In this paper,we summarized and sorted out the research status of underground coal fires,focused on the theoretical and technical issues such as underground coal fire combustion mechanism,multiphysics coupling effect of coal fire combustion,fire prevention and extinguishing technology for underground coal fires,and beneficial utilization technology,and described the latest research progress of the prevention and control for underground coal fire hazards.Finally,the key research problems in the field of underground coal fire hazards prevention and control were proposed in the direction of the basic theory,technology research,comprehensive management and utilization,with a view to providing ideas and solutions for the management of underground coal fires.
文摘采用浸渍法制备CeO_2负载的Co_3O_4催化剂粉末,将催化剂粉末制作了厚膜型催化燃烧式甲烷气体传感器进行测试,讨论不同钴负载量对甲烷催化的影响,重点研究了不同钴负载量对传感器稳定性的影响,通过SEM、TPR、XRD和BET对催化剂进行分析表征。实验结果显示,Co_3O_4/CeO_2催化剂对甲烷有较好的催化特性,Co_3O_4质量分数为30%时的催化剂制备的传感器对甲烷气体(体积分数2%)响应达到19 m V,且在高温环境下传感器响应能力保持稳定,550℃连续工作6 h响应值仅下降0.2 m V。分析催化剂高温处理前后结果,证实传感器失效是由催化剂失效所导致。
基金Project supported by the National Natural Science Foundation of China(Grant No.11772058)
文摘Natural aluminum particles have the core-shell structure.The structure response refers to the mechanical behavior of the aluminum particle structure caused by external influences.The dynamic behavior of the structural response of aluminum core-shell particles before combustion is of great importance for the aluminum powder burning mechanism and its applications.In this paper,an aluminum particle combustion experiment in a detonation environment is conducted and analyzed;the breakage factors of aluminum particles shell in detonation environment are analyzed.The experiment results show that the aluminum particle burns in a gaseous state and condenses into a sub-micron particle cluster.The calculation and simulation demonstrate that the rupture of aluminum particle shell in the detonation environment is mainly caused by the impact of the detonation wave.The detonation wave impacts the aluminum particles,resulting in shell cracking,and due to the shrinkage-expansion of the aluminum core and stripping of the detonation product,the cracked shell is fractured and peeled with the aluminum reacting with the detonation product.
文摘The effect of upstream velocity pertuibations on the response of a premixed flame was investigated in terms of the flame transfer function dependency on excitation frequency.In this study,the assumption of constant flame speed was extended and the effect of flame speed development was considered;i.e.,the flame speed would grow with the time after ignition or with the distance from a flame-holder.In the present study,the kinematics of a conical flame was investigated by linearization of the front tracking equation of flame to uniform and convected fluctuations of the flow velocity and the response was compared with that of a V-shaped flame and the experimental data in the previous studies.The results show that the effect of flame speed development could influence a decreasing gain and increase the phase of the flame response to the uniform velocity oscillations in low and moderate frequencies.Comparing the variations in the gain of flame response upon normalized frequency,show that a conical flame has lower values than the V-flame.In other woods,these flames might be less susceptible to combustion instabilities than the V-flames.Furthennore,the variations in phase of the V-flames responses,which show a quasi-linear behavior with normalized frequency,have higher values than the saturated behavior in phase of the conical flame responses.Also,considering that the flame speed development induces an increase in the gain and phase of the conical flame response to the convected velocity oscillations in certain frequencies;because the developed flame front has longer length in comparison to the flame front in constant flame speed model.Therefore,the flame length may be longer than convective wavelength and the heat release would be generated in different points of the flame;consequently the flow oscillations might exert a stronger impact on the unsteady heat release fluctuations.
