The primary and secondary arcs volt-ampere characteristics of low earth orbit solar arrays are studied in this research. Using three gallium-arsenide solar cell samples, the gap lengths of the solar cell are set to 1,...The primary and secondary arcs volt-ampere characteristics of low earth orbit solar arrays are studied in this research. Using three gallium-arsenide solar cell samples, the gap lengths of the solar cell are set to 1, 2, and 3 mm. First, the primary arc voltage characteristics of a solar array are analyzed. It is found that two steps are involved in the primary arc voltages, which are 116 and 22 V according to our experiment and are independent of the electrostatic discharge current and the gap lengths. By comparing with the arc pattern, we determined that current chopping may be the reason for the stepped arc voltage. Then, the characteristics of the secondary arc of the solar array are demonstrated. The study shows that the secondary arc voltage values increase with the gap length. In the case of the same cell with a fixed gap length, the voltage of the secondary arc increases with the string current. Finally, the relationship between the secondary arc voltage and the gap length is obtained which helps the string voltage and the gap length selection for system design.展开更多
We developed a novel cement evaluation logging tool,named the azimuthally acoustic bond tool（AABT）,which uses a phased-arc array transmitter with azimuthal detection capability.We combined numerical simulations and ...We developed a novel cement evaluation logging tool,named the azimuthally acoustic bond tool（AABT）,which uses a phased-arc array transmitter with azimuthal detection capability.We combined numerical simulations and field tests to verify the AABT tool.The numerical simulation results showed that the radiation direction of the subarray corresponding to the maximum amplitude of the first arrival matches the azimuth of the channeling when it is behind the casing.With larger channeling size in the circumferential direction,the amplitude difference of the casing wave at different azimuths becomes more evident.The test results showed that the AABT can accurately locate the casing collars and evaluate the cement bond quality with azimuthal resolution at the casing-cement interface,and can visualize the size,depth,and azimuth of channeling.In the case of good casingcement bonding,the AABT can further evaluate the cement bond quality at the cementformation interface with azimuthal resolution by using the amplitude map and the velocity of the formation wave.展开更多
Plasma Synthetic Jet(PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-mo...Plasma Synthetic Jet(PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-moving components. Although previous studies on PSJ actuators are abundant, most of them have focused on the performance of a single actuator. However, in practice, an actuator array is very necessary for large-scale aerodynamic actuation on account of the small affected area of a single PSJ. In this paper, the characteristics of a twoelectrode plasma synthetic jet actuator array in serial are investigated experimentally. Compared to a parallel actuator array, the serial actuator array requires simpler power supply design and is much easier to realize. High-speed photography of the discharge evolution, voltage-current measurement, and shadowgraphy visualization are used in the investigation. Experimental results show that, for the serial actuator array, weak discharges happen firstly between energized and suspending electrodes, and then a strong pulse arc discharge is triggered. The breakdown voltage in serial is irrelevant to such factors as the number of actuators, the maximum or minimum gap in serial,the connection sequence, etc. It is mainly determined by the sum of gaps. For serial actuators with the same anode-to-cathode spacing, the energy deposition is the same, and the jet is synchronous and similar. Because of the entrainment and merging of adjacent jet vortices, the jet front speed of an aligned synchronous jet array increases as the orifice distance decreases. To achieve the highest jet front velocity, the orifice of the actuator has an optimal diameter.展开更多
Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources....Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources. A phased arc array transmitter, which is a novel transducer that differs from monopole and dipole transducers, is presented in this study. To simulate the acoustic field generated by a phased arc array in a fluid-filled cased borehole with different channelings, a 3D finite-difference time-domain method is adopted. The acoustic field generated by a traditional monopole source is also simulated and compared with the field generated by the phased arc array transmitter. Numerical simulation results show that the phased arc array radiates energy directionally in a narrow angular range in the borehole, thereby compressing the acoustic energy into a narrow range in the casing pipe, the cement, and the formation. We present the analyses of first-arrival waveforms and the amplitudes of casing waves at different azimuthal angles for the two different sources. The results indicate that employing a directional source facilitates azimuthal identification and analysis of possible channeling behind the casing pipe.展开更多
针对传统声波测井井下仪器声源没有指向性或无法控制声波信号辐射指向性的不足,研制了方位声波测井仪(AABT,Azimuthally Acoustic Bond Tool)。该仪器能够实现定向测量,评价第Ⅰ界面和第Ⅱ界面的固井质量情况,并具有较好的周向分辨特性...针对传统声波测井井下仪器声源没有指向性或无法控制声波信号辐射指向性的不足,研制了方位声波测井仪(AABT,Azimuthally Acoustic Bond Tool)。该仪器能够实现定向测量,评价第Ⅰ界面和第Ⅱ界面的固井质量情况,并具有较好的周向分辨特性,其周向分辨能力可达40°,具有好的一致性和准确性。该仪器与单极子、偶极子和四极子等声波测井声源相比,真正实现了周向扫描测量,在固井质量评价、非均质地层评价、定向射孔、定向钻井和井间地层评价等方面有良好的应用前景。介绍了AABT测井仪的电子系统设计方案。仪器由发射电子线路短节、主测控电子线路短节和声系组成。对仪器电子系统的主要构成模块、各部分的主要功能和关键技术进行了比较详细的分析,并给出了初步的现场试验结果。展开更多
基金supported by National Natural Science Foundation of China (No. 51407008)
文摘The primary and secondary arcs volt-ampere characteristics of low earth orbit solar arrays are studied in this research. Using three gallium-arsenide solar cell samples, the gap lengths of the solar cell are set to 1, 2, and 3 mm. First, the primary arc voltage characteristics of a solar array are analyzed. It is found that two steps are involved in the primary arc voltages, which are 116 and 22 V according to our experiment and are independent of the electrostatic discharge current and the gap lengths. By comparing with the arc pattern, we determined that current chopping may be the reason for the stepped arc voltage. Then, the characteristics of the secondary arc of the solar array are demonstrated. The study shows that the secondary arc voltage values increase with the gap length. In the case of the same cell with a fixed gap length, the voltage of the secondary arc increases with the string current. Finally, the relationship between the secondary arc voltage and the gap length is obtained which helps the string voltage and the gap length selection for system design.
基金supported by the National Natural Science Foundation of China(Nos.11204380,11374371,61102102,and11134011)National Science and Technology Major Project(No.2011ZX05020-009)+1 种基金China National Petroleum Corporation(Nos.2014B-4011,2014D-4105,and 2014A-3912)PetroChina Innovation Foundation(No.2014D-5006-0307)
文摘We developed a novel cement evaluation logging tool,named the azimuthally acoustic bond tool（AABT）,which uses a phased-arc array transmitter with azimuthal detection capability.We combined numerical simulations and field tests to verify the AABT tool.The numerical simulation results showed that the radiation direction of the subarray corresponding to the maximum amplitude of the first arrival matches the azimuth of the channeling when it is behind the casing.With larger channeling size in the circumferential direction,the amplitude difference of the casing wave at different azimuths becomes more evident.The test results showed that the AABT can accurately locate the casing collars and evaluate the cement bond quality with azimuthal resolution at the casing-cement interface,and can visualize the size,depth,and azimuth of channeling.In the case of good casingcement bonding,the AABT can further evaluate the cement bond quality at the cementformation interface with azimuthal resolution by using the amplitude map and the velocity of the formation wave.
基金supported by the National Natural Science Foundation of China(Nos.11372349,11502295,and11572349)
文摘Plasma Synthetic Jet(PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-moving components. Although previous studies on PSJ actuators are abundant, most of them have focused on the performance of a single actuator. However, in practice, an actuator array is very necessary for large-scale aerodynamic actuation on account of the small affected area of a single PSJ. In this paper, the characteristics of a twoelectrode plasma synthetic jet actuator array in serial are investigated experimentally. Compared to a parallel actuator array, the serial actuator array requires simpler power supply design and is much easier to realize. High-speed photography of the discharge evolution, voltage-current measurement, and shadowgraphy visualization are used in the investigation. Experimental results show that, for the serial actuator array, weak discharges happen firstly between energized and suspending electrodes, and then a strong pulse arc discharge is triggered. The breakdown voltage in serial is irrelevant to such factors as the number of actuators, the maximum or minimum gap in serial,the connection sequence, etc. It is mainly determined by the sum of gaps. For serial actuators with the same anode-to-cathode spacing, the energy deposition is the same, and the jet is synchronous and similar. Because of the entrainment and merging of adjacent jet vortices, the jet front speed of an aligned synchronous jet array increases as the orifice distance decreases. To achieve the highest jet front velocity, the orifice of the actuator has an optimal diameter.
基金supported by the National Natural ScienceFoundation of China (Grant Nos. 11204380, 11374371, 11134011 and 61102102)National Science and Technology Major Project (Grant No. 2011ZX05020-009)PetroChina Innovation Foundation (2013D-5006-0304)
文摘Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources. A phased arc array transmitter, which is a novel transducer that differs from monopole and dipole transducers, is presented in this study. To simulate the acoustic field generated by a phased arc array in a fluid-filled cased borehole with different channelings, a 3D finite-difference time-domain method is adopted. The acoustic field generated by a traditional monopole source is also simulated and compared with the field generated by the phased arc array transmitter. Numerical simulation results show that the phased arc array radiates energy directionally in a narrow angular range in the borehole, thereby compressing the acoustic energy into a narrow range in the casing pipe, the cement, and the formation. We present the analyses of first-arrival waveforms and the amplitudes of casing waves at different azimuthal angles for the two different sources. The results indicate that employing a directional source facilitates azimuthal identification and analysis of possible channeling behind the casing pipe.
文摘针对传统声波测井井下仪器声源没有指向性或无法控制声波信号辐射指向性的不足,研制了方位声波测井仪(AABT,Azimuthally Acoustic Bond Tool)。该仪器能够实现定向测量,评价第Ⅰ界面和第Ⅱ界面的固井质量情况,并具有较好的周向分辨特性,其周向分辨能力可达40°,具有好的一致性和准确性。该仪器与单极子、偶极子和四极子等声波测井声源相比,真正实现了周向扫描测量,在固井质量评价、非均质地层评价、定向射孔、定向钻井和井间地层评价等方面有良好的应用前景。介绍了AABT测井仪的电子系统设计方案。仪器由发射电子线路短节、主测控电子线路短节和声系组成。对仪器电子系统的主要构成模块、各部分的主要功能和关键技术进行了比较详细的分析,并给出了初步的现场试验结果。
