Since 1992 the author has led research group in Xi'an Jiaotong University to investigate and develop micro-electro mechanical systems(MEMS) sensors,including pressure sensor,acceleration sensor,gas sensor,viscosit...Since 1992 the author has led research group in Xi'an Jiaotong University to investigate and develop micro-electro mechanical systems(MEMS) sensors,including pressure sensor,acceleration sensor,gas sensor,viscosity & density sensor,polymerase chain reaction(PCR) chip and integrated sensor etc.This paper introduces the technologies and research results related to MEMS sensors we achieved in the last 20 years.展开更多
In order to reveal the effect of turnings on explosion propagation, experiments were performed in three different pipes (single bend, U-shaped pipe and Z-shaped pipe). Flame and pressure transducers were used to tra...In order to reveal the effect of turnings on explosion propagation, experiments were performed in three different pipes (single bend, U-shaped pipe and Z-shaped pipe). Flame and pressure transducers were used to track the velocity at the explosion front. When the pipes were filled with methane, the explosion strength was significantly enhanced due to the turbulence induced by increasing the number of turnings, while the flame speed (Sf) and peak overpressure (ΔPmax) increased dramatically. In addition, the strength of the explosion increased in violence as a function of the number of turnings. However, when the bend was without methane, the turnings weakened the strength of the explosion compared with the ordinary pipe, shown by the decrease in the values of ΔPmax and Sf. In addition, the propagation characteristics in a U-shaped pipe were similar to those in a Z-shaped pipe and the values of APmax and Sf were also close. The results show that the explosion propagation characteristics largely depend on gas distribution in the pipes and the number of turnings. The different directions of the turnings had no effect.展开更多
An experimental investigation on the unsteady tip flow field of a transonic compressor rotor has been performed.The casing-mounted high frequency response pressure transducers were arranged along both the blade chord ...An experimental investigation on the unsteady tip flow field of a transonic compressor rotor has been performed.The casing-mounted high frequency response pressure transducers were arranged along both the blade chord and the blade pitch.The chord-wise ones were used to indicate both the ensemble averaged and time varying flow structure of the tip region of the rotor at different operating points under 95% design speed and 60% design speed.The pitch-wise circumferential transducers were mainly used to analyze the unsteadiness frequency of the tip leakage flow in the rotor frame at the near stall condition.The contours of casing wall pressure show that there were two clear low pressure regions in blade passages,one along the chord direction,caused by the leakage flow and the other along the tangential direction,maybe caused by the forward swept leading edge.Both low pressure regions were originated from the leading edge and formed a scissor-like flow pattern.At 95% design speed condition,the shock wave interacted with the low pressure region and made the flow field unsteady.With the mass flow reduced,the two low pressure regions gradually contracted to the leading edge and then a spike disturbance emerged.展开更多
A new method of measuring gas pressure in vacuum insulation panels(VIPs)is reported in this study,which provides a fast and efficient quality control option of production.Although there are different methods of measur...A new method of measuring gas pressure in vacuum insulation panels(VIPs)is reported in this study,which provides a fast and efficient quality control option of production.Although there are different methods of measuring gas pressure for VIPs,connecting an internal measurement gauge to external data acquisition units is problematic.The thin high barrier film covering the panel’s core usually prevents external electrical wires or mechanical devices being connected to the inside of the VIPs.To solve this problem,a micro capacitive pressure sensor with 0 to 250 Pa detection range is developed to detect the vacuum pressure.The sensor has high linearity and a sensitivity of 10 mV/Pa.Moreover,through the communication mode study,an ultrasound communications system for VIPs is designed.It shows from operation that this system is stable and reliable,and quick for communication speed.This new method enables the quality detection of VIPs to be completed within 1 second.The minimum detectable pressure of VIPs is below 1 Pa,and the measurement error can be controlled around 5%.展开更多
文摘Since 1992 the author has led research group in Xi'an Jiaotong University to investigate and develop micro-electro mechanical systems(MEMS) sensors,including pressure sensor,acceleration sensor,gas sensor,viscosity & density sensor,polymerase chain reaction(PCR) chip and integrated sensor etc.This paper introduces the technologies and research results related to MEMS sensors we achieved in the last 20 years.
基金Financial support for this work, provided by the National Natural Science Foundation of China (No.50574093)the Key Program of the National Natural Science Foundation of China (No.50534090)+3 种基金the National Basic Research and Development Program of China (No.2005CB221506)the National Science Foundation for Young Scholars of China (No.50804048)the National Key Technology R&D Program (No.2007BAK29B01) Research Innovation Program for College Graduates of Jiangsu Provincethe Open Foundation of State Key Laboratory of Explosion Science and Technology (No.KFJJ10-19M)
文摘In order to reveal the effect of turnings on explosion propagation, experiments were performed in three different pipes (single bend, U-shaped pipe and Z-shaped pipe). Flame and pressure transducers were used to track the velocity at the explosion front. When the pipes were filled with methane, the explosion strength was significantly enhanced due to the turbulence induced by increasing the number of turnings, while the flame speed (Sf) and peak overpressure (ΔPmax) increased dramatically. In addition, the strength of the explosion increased in violence as a function of the number of turnings. However, when the bend was without methane, the turnings weakened the strength of the explosion compared with the ordinary pipe, shown by the decrease in the values of ΔPmax and Sf. In addition, the propagation characteristics in a U-shaped pipe were similar to those in a Z-shaped pipe and the values of APmax and Sf were also close. The results show that the explosion propagation characteristics largely depend on gas distribution in the pipes and the number of turnings. The different directions of the turnings had no effect.
基金supported by the National Natural Science Foundation in China under Grant No.50736007National Basic Research Program 2007CB210104 of China
文摘An experimental investigation on the unsteady tip flow field of a transonic compressor rotor has been performed.The casing-mounted high frequency response pressure transducers were arranged along both the blade chord and the blade pitch.The chord-wise ones were used to indicate both the ensemble averaged and time varying flow structure of the tip region of the rotor at different operating points under 95% design speed and 60% design speed.The pitch-wise circumferential transducers were mainly used to analyze the unsteadiness frequency of the tip leakage flow in the rotor frame at the near stall condition.The contours of casing wall pressure show that there were two clear low pressure regions in blade passages,one along the chord direction,caused by the leakage flow and the other along the tangential direction,maybe caused by the forward swept leading edge.Both low pressure regions were originated from the leading edge and formed a scissor-like flow pattern.At 95% design speed condition,the shock wave interacted with the low pressure region and made the flow field unsteady.With the mass flow reduced,the two low pressure regions gradually contracted to the leading edge and then a spike disturbance emerged.
基金supported by the Science and Technology Projects of Fujian Province of China(Grant No.2010H6025)Science and Technology Projects of Xiamen City of China(Grant No.3502Z20103012)
文摘A new method of measuring gas pressure in vacuum insulation panels(VIPs)is reported in this study,which provides a fast and efficient quality control option of production.Although there are different methods of measuring gas pressure for VIPs,connecting an internal measurement gauge to external data acquisition units is problematic.The thin high barrier film covering the panel’s core usually prevents external electrical wires or mechanical devices being connected to the inside of the VIPs.To solve this problem,a micro capacitive pressure sensor with 0 to 250 Pa detection range is developed to detect the vacuum pressure.The sensor has high linearity and a sensitivity of 10 mV/Pa.Moreover,through the communication mode study,an ultrasound communications system for VIPs is designed.It shows from operation that this system is stable and reliable,and quick for communication speed.This new method enables the quality detection of VIPs to be completed within 1 second.The minimum detectable pressure of VIPs is below 1 Pa,and the measurement error can be controlled around 5%.