This study attempts to apply a single-probe fiber-optic reflectometer (FOR) to determine the velocities and sizes of oil droplets rising in a static water column. The concept proposed by Chang et al (2003 Rev. Sci. Instrum. 74 3559-65) was employed to derive the oil droplet velocity from a signal acquired using the FOR technique. An oil plume in a vertical water column was set up to verify the applicability in the oil-water mixture flow. A high-speed imaging technique was applied to provide control data sets for quantitative validation. The droplet velocity, residence time, and chord length measurements were validated by comparing with the results from high-speed images using the bubble image velocimetry technique and the image gradient method. To extract the oil-phase residence time, a double-threshold method was applied. It was found that the velocity measured by the FOR probe has an error of approximately 8%, while the measured chord length has an error of 13% and 8% in direct and indirect comparison with images, respectively. Furthermore, to evaluate the applicability of droplet size estimation using the present cleaved-tip single-optical-fiber probe, droplet-probe interaction was studied to examine the lower limit of the measurable range using dominant dimensionless parameters. The lower limit was found as roughly 20 times the diameter of the optical-fiber probe.
Abstract:Wave energy converters have been developed and commercialized in past decades; they have now faced numerous challenges of large volume sizes, environmental hazards, and high costs of deployment, components and maintenance. To address these challenges and make a wave energy converter practically available for various applications at a reasonable cost, we have developed a soft wave energy harvester that integrated low-cost soft material structures and piezoelectric-based Macro Fiber Composite (MFC). This integrated soft wave energy converter has a straightforward fabrication process and structure that can harvest energy from a broad working frequency of waves. The innovative design combined low-cost and commercially available materials and formed a harvester that addressed the aforementioned problems of commercially available harvesters. Additionally, the low cost and simple design are scalable for large energy conversion in the future. The energy conversion performance of the proposed platform has been investigated in a wave flume with low-frequency incoming waves (<2Hz). The soft energy conversion platform is hung like a curtain and produces a maximum 487nW. Also, the low cost and durable encapsulation can protect the electrical properties of MFCs and circuits, and a single harvester can last through all experiment steps without any degradation, which was more than 170 hours.
This paper presents an experimental study to investigate the applicability and accuracy of phase discrimination and measurements of velocity and size for bubbles and droplets using a single-probe fiber optic reflectometer technique in an oil–gas–water three-phase flow. The technique is capable of identifying dispersed and continuous phases and measuring velocity and size of gas bubbles or oil droplets in two-phase flows. In this study, the technique was expanded to identify water, air bubbles, and oil droplets and quantify velocity and size of bubbles and droplets in an oil–gas–water three-phase flow through processing the acquired signals. By applying Fresnel reflectivity, setting a threshold, and using wavelet transform for phase discrimination, bubbles and droplets were identified with improved accuracy. In the study, 99.9% of the droplets and 98.3% of bubbles were successfully discriminated for the approximately 7000 combined bubble and droplet encounters. Besides, the velocity, size, and phase were correctly measured and identified in 100% of 117 encounters (63% of which are bubbles) for the cases with signals containing the velocity information. Furthermore, a dominant dimensionless parameter was identified to quantify the applicability limit of the probe to bubble and droplet size ratios.
An open-water wave energy converter (OWEC) made of a new soft platform has been developed by combining piezoelectric macro-fiber composites (MFCs) and a low-cost elastomer. In the past decades, numerous types of water wave energy conversion platform have been developed and investigated, from buoys to overtopping devices. These harvesters mainly use electromagnetic-based generators, and they have faced challenges such as their enormous size, high deployment and maintenance costs, and negative effects on the environment. These problems hinder their practicality and competitiveness. In this paper, a soft open-water wave energy converter is introduced which integrates piezoelectric MFCs and bubble wrap into an elastomer sheet. The performance of the OWEC was investigated in a wave flume as a floatable structure. The maximum 29.7 µW energy harvested from the small OWEC represents a promising energy conversion performance at low frequencies (<2 Hz). The elastomer was able to protect the MFCs and internal electrical connections without any degradation during the experiment. In addition, the OWEC is a foldable structure, which can reduce the deployment costs in real-world applications. The combination of no maintenance, low fabrication cost, low deployment cost, and moderate energy harvesting capability may advance the OWEC platform to its real-world applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.