A passive negative stiffness damper in series with a flexible support: Theoretical and experimental study

2020 ◽  
Vol 27 (9) ◽  
Author(s):  
Peng Zhou ◽  
Min Liu ◽  
Hui Li
Keyword(s):  
Experimental Study ◽  
Negative Stiffness ◽  
Flexible Support ◽  
In Series

scholarly journals Piezoelectric Shunt Stiffness in Rhombic Piezoelectric Stack Transducer with Hybrid Negative-Impedance Shunts: Theoretical Modeling and Stability Analysis

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3387
Author(s):  
He ◽  
Zheng ◽  
Zhao ◽  
Wu
Keyword(s):  
Coupled System ◽  
Analytical Framework ◽  
Negative Stiffness ◽  
Negative Capacitance ◽  
Control Engineering ◽  
Locus Method ◽  
In Series ◽  
The Stability ◽  
Stiffness And Damping ◽  
Piezoelectric Shunt

Negative-capacitance shunted piezoelectric polymer was investigated in depth due to its considerable damping effect. This paper discusses the novel controlled stiffness performance from a rhombic piezoelectric stack transducer with three hybrid negative-impedance shunts, namely, negative capacitance in series with resistance, negative capacitance in parallel with resistance, and negative inductance/negative capacitance (NINC) in series with resistance. An analytical framework for establishing the model of the coupled system is presented. Piezoelectric shunt stiffness (PSS) and piezoelectric shunt damping (PSD) are proposed to analyze the stiffness and damping performances of the hybrid shunts. Theoretical analysis proves that the PSS can produce both positive and negative stiffness by changing the negative capacitance and adjustable resistance. The Routh–Hurwitz criterion and the root locus method are utilized to judge the stability of the three hybrid shunts. The results point out that the negative capacitance should be selected carefully to sustain the stability and to achieve the negative stiffness effect of the transducer. Furthermore, negative capacitance in parallel with resistance has a considerably better stiffness bandwidth and damping performance than the other two shunts. This study demonstrates a novel electrically controlled stiffness method for vibration control engineering.

A Modular-Type Three-Axis Vibration Isolation System Using Negative Stiffness

2010 ◽  
Author(s):  
Md. Emdadul Hoque ◽  
Takeshi Mizuno ◽  
Yuji Ishino ◽  
Masaya Takasaki
Keyword(s):  
Vibration Isolation ◽  
Degree Of Freedom ◽  
Experimental Results ◽  
Negative Stiffness ◽  
Isolation System ◽  
Single Degree Of Freedom ◽  
Vibration Isolation System ◽  
Single Degree ◽  
In Series ◽  
Isolation Systems

A vibration isolation system is presented in this paper which is developed by the combination of multiple vibration isolation modules. Each module is fabricated by connecting a positive stiffness suspension in series with a negative stiffness suspension. Each vibration isolation module can be considered as a self-sufficient single-degree-of-freedom vibration isolation system. 3-DOF vibration isolation system can be developed by combining three modules. As the number of motions to be controlled and the number of actuators are equal, there is no redundancy in actuators in such vibration isolation systems. Experimental results are presented to verify the proposed concept of the development of MDOF vibration isolation system using vibration isolation modules.

An Experimental Study of Surfactant Effect on Gas Tolerance in Electrical Submersible Pump (ESP)

2017 ◽  
Author(s):  
Jianjun Zhu ◽  
Haiwen Zhu ◽  
Jiecheng Zhang ◽  
Hong-Quan Zhang
Keyword(s):  
Experimental Study ◽  
Water Flow ◽  
Flow Rate ◽  
Liquid Flow ◽  
Gas Flow ◽  
Liquid Flow Rate ◽  
Entrainment Rate ◽  
Operational Conditions ◽  
In Series ◽  
Pressure Increment

An experimental study on ESP boosting pressure under air-water flow with/without surfactant injection is presented. The experimental facility comprises of a 3-inch-diameter stainless steel liquid loop and ½-inch-diameter gas loop. A radial-type ESP with 14 stages assembled in series was installed in the testing bench. Pressure ports were drilled at inter-stage to measure the stage-by-stage boosting pressure. Surfactants, isopropanol (IPA) were injected to change interfacial properties of working fluids. Experiments were carried out with mapping and surging test schemes to evaluate pump behaviors at different operational conditions. ESP pressure increment under single-phase water flow agrees well with manufacture curves. For mapping tests without surfactant injection, ESP performance suffers from a severe degradation as gas flow rate increases. High gas entrainment rate causes oscillations of liquid flow rate and pump boosting pressure. A sudden drop of ESP pressure increment, termed as pressure surging, occurs at the critical inlet gas volumetric fraction (GVF). At higher rotational speeds, the critical GVF is higher. With surfactant injection, ESP boosting pressure improves significantly. With different GVFs, only mild degradation was observed. Pressure surging phenomenon disappeared. Further, liquid flow rate and pump boosting pressure are more stable at high GVFs compared to experimental data without surfactant injection.

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