An Apparatus for the Performance Estimation of Pressure Fluctuation Energy Harvesters

The continuous scour of an erodible bed downstream a roller bucket energy dissipater makes it difficult to quantify the efforts applied on the bed. An astute technique allows the measurement of these efforts for various stages of scour and facilitates a better comprehension of the interaction between these efforts and the scour downstream. This technique consists in measuring the bed profile (downstream the dissipater) as a function of time and reproducing scoured profiles using a solid model (concrete) that allows the setting of the measuring devices. The analysis of the efforts has shown that as soon as the scour starts, a small bed deformation induces important changes in the pressure and in the pressure fluctuation distributions in the vicinity of the structure. As erosion goes on, the efforts vary slightly and the distributions remain unchanged. The behaviour of the efforts regarding the erosive process could be interpreted by the nature of scour phenomenon, which develops strongly during the initial phase, and by the specific behaviour of the zone in the vicinity of the bucket, which evolves rapidly and stabilizes quickly.Key words: hydrodynamic efforts, pressure, pressure fluctuation, energy dissipater, roller bucket, movable bed.

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Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine

International Journal of Rotating Machinery ◽

10.1155/2019/4396546 ◽

2019 ◽

Vol 2019 ◽

pp. 1-13

Author(s):

Jian Liu ◽

Wei-Yang Qiao ◽

Wen-Hua Duan

Keyword(s):

Pressure Fluctuation ◽

Rotor Blade ◽

Pressure Fluctuations ◽

Three Dimensional ◽

Operating Conditions ◽

Variable Geometry ◽

Blade Surface ◽

Variable Geometry Turbine ◽

Mach Numbers ◽

Fluctuation Energy

To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.

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Self-Powered Wireless Sensor Using a Pressure Fluctuation Energy Harvester

Sensors ◽

10.3390/s21041546 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1546

Author(s):

Jesus Javier Aranda ◽

Sebastian Bader ◽

Bengt Oelmann

Keyword(s):

Pressure Fluctuation ◽

Energy Harvester ◽

Pressure Fluctuations ◽

Acoustic Resonator ◽

Sensor Data ◽

Wireless Sensor ◽

Hydraulic Systems ◽

Interface Circuit ◽

Self Powered ◽

Fluctuation Energy

Condition monitoring devices in hydraulic systems that use batteries or require wired infrastructure have drawbacks that affect their installation, maintenance costs, and deployment flexibility. Energy harvesting technologies can serve as an alternative power supply for system loads, eliminating batteries and wiring requirements. Despite the interest in pressure fluctuation energy harvesters, few studies consider end-to-end implementations, especially for cases with low-amplitude pressure fluctuations. This generates a research gap regarding the practical amount of energy available to the load under these conditions, as well as interface circuit requirements and techniques for efficient energy conversion. In this paper, we present a self-powered sensor that integrates an energy harvester and a wireless sensing system. The energy harvester converts pressure fluctuations in hydraulic systems into electrical energy using an acoustic resonator, a piezoelectric stack, and an interface circuit. The prototype wireless sensor consists of an industrial pressure sensor and a low-power Bluetooth System-on-chip that samples and wirelessly transmits pressure data. We present a subsystem analysis and a full system implementation that considers hydraulic systems with pressure fluctuation amplitudes of less than 1 bar and frequencies of less than 300 Hz. The study examines the frequency response of the energy harvester, the performance of the interface circuit, and the advantages of using an active power improvement unit adapted for piezoelectric stacks. We show that the interface circuit used improves the performance of the energy harvester compared to previous similar studies, showing more power generation compared to the standard interface. Experimental measurements show that the self-powered sensor system can start up by harvesting energy from pressure fluctuations with amplitudes starting at 0.2 bar at 200 Hz. It can also sample and transmit sensor data at a rate of 100 Hz at 0.7 bar at 200 Hz. The system is implemented with off-the-shelf circuits.

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