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Investigations on multicycle spray detonations

LI Mu, YAN Chuanjun, ZHENG Longxi, WANG Zhiwu, QIU Hua

《能源前沿(英文)》 2007年 第1卷 第2期   页码 207-212 doi: 10.1007/s00000-007-0027-5

摘要: Experimental investigations were carried out on a 50-I.D. multicycle pulse detonation engine (PDE) model, and liquid fuel (gasoline) was used. The average of pressure peak, as measured by piezoelectricity pressure transducer, increased versus distance to thrust wall before fully-developed detonation came into being. According to the pressure history, the pressure in detonation tube would not rise abruptly until the flame front advanced a certain distance downstream the spark. Just at that moment, two compression waves spreading to opposite direction were formed. One was enforced by combustion and became detonation rapidly. The other was weakened because of obstacles and insufficiency of fuel. Two methods were used to determine the induction length of two-phase detonation wave through the pressure history. Ignition delay time was found to be longer than deflagration-to-detonation transition (DDT) time, and the sum of the two would change little as cycle frequency increased. So they could be the most important factors controlling two-phase PDE frequency. Filling process and blowdown process were also analyzed.

关键词: multicycle     deflagration-to-detonation transition     pressure transducer     compression     piezoelectricity pressure    

Novel piezoelectric pump with “E”-shaped valve found from sub-experiments

Jianhui ZHANG, Jun HUANG, Xiaoqi HU, Qixiao XI,

《机械工程前沿(英文)》 2010年 第5卷 第2期   页码 212-218 doi: 10.1007/s11465-010-0009-x

摘要: Increasing the driving frequency of a piezoelectric vibrator can resolve the bottleneck of low flow in a valve piezoelectric pump. However, a piezoelectric pump of a traditional valve body presents the hysteretic nature of the valve, and macroscopic performance is up-frequency to flow-sharply. This research is to settle the bottleneck mentioned above. First, through the sub-experiment on various parameters of the plate valve of a piezoelectric pump, the reasons why a valve body itself can influence “up-frequency to flow-sharply”, which causes the hysteretic nature of the valve, were discovered. Second, an “E”-shaped valve and piezoelectric pump with an “E”-shaped valve (PPEV) were invented. Finally, the efficiency of PPEV has been proved helpful to reduce hysteretic nature in experiments. Under the similar conditions, compared with traditional pumps, the driving frequency of novel PPEV can be more than 10 times high, and the flow rate also can be several times high.

关键词: piezoelectricity     valve     pump     experiment         E”     -shaped valve    

Microstructure and electrical properties of NaNbO

Shihui XIE, Kongjun ZHU, Jinhao QIU, Hua GUO

《机械工程前沿(英文)》 2009年 第4卷 第3期   页码 345-349 doi: 10.1007/s11465-009-0050-9

摘要: Lead-free piezoelectric ceramics (1- )NaNbO - BaTiO have been fabricated by a traditional ceramic sintering technique. The effects of BaTiO (BT) synthesized by hydrothermal method on crystal structure, density, dielectric, piezoelectric, and electromechanical properties were investigated. Results show that the phase structure transforms from the orthorhombic phase to the tetragonal phase with the increase of the content of BT, and the two phases co-exist when 0.08< ≤0.10. However, the optimum composition for (1- )NaNbO - BaTiO ceramics is 0.90NaNbO -0.10BaTiO . The 0.90NaNbO -0.10BaTiO ceramics sintered at 1250°C have higher properties: piezoelectric constant of 120 pC/N, dielectric constant of 718, planar electromechanical coupling factor of 24%, planar frequency of 3 MHz·mm, and the mechanical quality factor of 138, respectively. The results show that the (1- )NaNbO - BaTiO ceramics is one of the promising lead-free materials for high-frequency applications.

关键词: Lead-free piezoelectric ceramics     NaNbO3-BaTiO3     piezoelectricity     ceramics     crystal structure     microstructure    

Machine of testing the ceramic’s bending strength properties at high temperature and ultra-low speed

Jianhui ZHANG, Fang YE, Onuki AKIYOSHI,

《机械工程前沿(英文)》 2010年 第5卷 第3期   页码 289-293 doi: 10.1007/s11465-010-0094-x

摘要: According to the established rules for testing ceramic’s bending strength, the falling velocity of the pressure head of the machine should be more than 0.5 mm/min. For the machine of testing the ceramic’s bending strength properties, most designs adopt the lowest falling velocity as 0.5 mm/min. In the fields such as aerospace and deep-ocean exploration, the utilization of ceramic materials that work at normal temperature, low temperature, or even high temperature and bend at an ultra-low velocity is increasing; thus, the intense requirements for the machine of testing the ceramic’s bending strength properties at high temperature and ultra-low speed (MTCBSP) and its experimental basis are put forward. This research developed an MTCBSP suitable for normal temperature and high temperature with the lowest falling velocity of 0.05 mm/min, and manufactured a drive reducer for ultra-low speed and high-temperature working condition. In the test, equipment includes a high-temperature furnace, bending die for four-point bending, and protection system of inert gas, which was placed in the high-temperature furnace to prevent the ceramic sample from being oxidized to diminish its effects. The results show that the lowest falling velocity of the pressure head of this new machine is 0.05 mm/min, and the mechanical properties of silica glasses are noticeably different at the same high temperature and the different falling velocities of 0.5 mm/min and 0.05 mm/min.

关键词: piezoelectricity     value     pump     experiment         E”     -shaped value    

Detection of void and metallic inclusion in 2D piezoelectric cantilever beam using impedance measurements

S. SAMANTA, S. S. NANTHAKUMAR, R. K. ANNABATTULA, X. ZHUANG

《结构与土木工程前沿(英文)》 2019年 第13卷 第3期   页码 542-556 doi: 10.1007/s11709-018-0496-0

摘要: The aim of current work is to improve the existing inverse methodology of void-detection based on a target impedance curve, leading to quick-prediction of the parameters of single circular void. In this work, mode-shape dependent shifting phenomenon of peaks of impedance curve with change in void location has been analyzed. A number of initial guesses followed by an iterative optimization algorithm based on univariate method has been used to solve the problem. In each iteration starting from each initial guess, the difference between the computationally obtained impedance curve and the target impedance curve has been reduced. This methodology has been extended to detect single circular metallic inclusion in 2D piezoelectric cantilever beam. A good accuracy level was observed for detection of flaw radius and flaw-location along beam-length, but not the precise location along beam-width.

关键词: piezoelectricity     impedance curve     mode shapes     inverse problem     flaw detection     curve shifting    

标题 作者 时间 类型 操作

Investigations on multicycle spray detonations

LI Mu, YAN Chuanjun, ZHENG Longxi, WANG Zhiwu, QIU Hua

期刊论文

Novel piezoelectric pump with “E”-shaped valve found from sub-experiments

Jianhui ZHANG, Jun HUANG, Xiaoqi HU, Qixiao XI,

期刊论文

Microstructure and electrical properties of NaNbO

Shihui XIE, Kongjun ZHU, Jinhao QIU, Hua GUO

期刊论文

Machine of testing the ceramic’s bending strength properties at high temperature and ultra-low speed

Jianhui ZHANG, Fang YE, Onuki AKIYOSHI,

期刊论文

Detection of void and metallic inclusion in 2D piezoelectric cantilever beam using impedance measurements

S. SAMANTA, S. S. NANTHAKUMAR, R. K. ANNABATTULA, X. ZHUANG

期刊论文