Wave and current energy can be harnessed in the East China Sea and South China Sea; however, both areas are subject to high frequencies of typhoon events. To improve the safety of the ocean energy conversion device, a Floating Ocean Energy Conversion Device (FOECD) with a single mooring system is proposed, which can be towed to avoid severe ocean conditions or for regular maintenance. In this paper, the structure of the FOECD is introduced, and it includes a catamaran platform, an oscillating buoy part, a current turbine blade, hydraulic energy storage and an electrical generation part. The numerical study models the large catamaran platform as a single, large buoy, while the four floating buoys were modeled simply as small buoys. Theoretical models on wave energy power capture and efficiency were established. To improve the suitability of the buoy for use in the FOECD and its power harvesting capability, a numerical simulation of the four buoy geometries was undertaken. The shape profiles examined in this paper are cylindrical, turbinate (V-shaped and U-shaped cone with cylinder), and combined cylinder-hemisphere buoys. Simulation results reveal that the suitability of a turbinate buoy is the best of the four types. Further simulation models were carried out by adjusting the tip radius of the turbinate buoy. Three performance criteria including suitability, power harvesting capability and energy capture efficiency were analyzed. It reveals that the turbinate buoy has almost the same power harvesting capabilities and energy capture efficiency, while its suitability is far better than that of a cylindrical buoy.
Real-time detection and identification of orchard pests is related to the economy of the orchard industry. Using lab picture collections and pictures from web crawling, a dataset of common pests in orchards has been created. It contains 24,748 color images and covers seven types of orchard pests. Based on this dataset, this paper combines YOLOv5 and GhostNet and explains the benefits of this method using feature maps, heatmaps and loss curve. The results show that the mAP of the proposed method increases by 1.5% compared to the original YOLOv5, with 2× or 3× fewer parameters, less GFLOPs and the same or less detection time. Considering the fewer parameters of the Ghost convolution, our new method can reach a higher mAP with the same epochs. Smaller neural networks are more feasible to deploy on FPGAs and other embedding devices which have limited memory. This research provides a method to deploy the algorithm on embedding devices.
The important parameters to describe waves are their amplitude and length. In order to make it easier to improve wave amplitude and facilitate wave experiment, a simple push-type wave generating method using digital rotary valve control was proposed and different wave amplitudes were generated by the new method. After the mathematical model of the new method had been established, numerical analysis based on the linear wave theory was carried out by means of Matlab/Simulink software tools, and experiments were conducted on the push-type wave maker to ascertain the validity of the established model and the numerical simulation results. It shows that both experimental and theoretical results agree relatively well, and the plate motion frequency and amplitude of the push-type wave maker can be continuously adjusted and the various required regular waves can be obtained. Although the wave amplitude and length descends with the increasing of working frequency, the wave amplitude can be improved conveniently by setting the axial opening width of the valve and the oil supply pressure of system. The wave length remains unchanged with the axial opening width and the oil supply pressure change. The research indicates that different regular waves can be easily generated by the new method and the wave amplitude can be further improved in a certain plate motion frequency range.
In this paper, we introduced an intermittent wave energy generator (IWEG) system with hydraulic power take-off (PTO) including accumulator storage parts. To convert unsteady wave energy into intermittent but stable electrical output power, theoretical models, including wave energy capture, hydraulic energy storage, and torque balance between hydraulic motor and electrical generator, have been developed. Then, the integrated IWEG simulator was constructed and tested at the Ningbo Institute of Technology. Through a series of experimental tests, the relationship between operating flow rates and pressure drops across the hydraulic motor was established. Furthermore, on the basis of the pressure drop signal, we proposed a feedback control method on the basis of the pressure drop database as the feedback control signal to eliminate the disturbance of periodic peak pressure impulse through the regulation of the opening ratio of a proportional flow valve and achieved the effective and stable electric power output, albeit intermittently. Compared with the previous complex control theories and algorithms, this method can keep the power output more stable over a wide range of operating conditions. Furthermore, experimental tests indicate that the IWEG system, with hydraulic PTO, including hydraulic accumulator and proportional flow control valve, is simple, reliable, and easy to control. Most importantly, the real-time power output is stable, and power quality and generation efficiency are significantly improved.
Tank sloshing in a liquid cargo ship will cause instability or even overturning of its carrier if the external wave frequency is close to the natural frequency of the tank. The inherent damping of a tank without inner structures has been found to be insufficient for suppressing violent sloshing motion. A variety of damping plates have been designed to increase the inherent damping of the tank. Of them, a horizontal perforated plate (HPP) has been proved to be effective for dissipating energy in a swaying tank through experiments. In this study, the sloshing problem in a tank with an HPP under swaying and rolling excitation is analytically studied based on the potential theory. The quadratic pressure loss boundary at the perforated plate is adopted, and the matched eigenfunction expansion method (MEEM) with iterative calculations is used to develop the analytical model. Based on the different porosities and submerged depths of the plate, both the free surface elevations and the hydrodynamic coefficients are carefully examined. The results give a better understanding in the effect of the inner HPP on the sloshing motion in the ship tank.
In order to develop a portable, autonomous power generation system with a magnitude improvement in energy density over alkaline or lithium-ion batteries, the liquid hydrocarbons fueled small-scale rotary (Wankel-type) internal combustion engines project is directed toward the development of a practical small-scale power generator. Micro combustion and seal are two of the most prominent questions of the design of small-scale rotary engine. As a result, the mathematical model of the micro combustion is proposed and some simulations are implemented. In addition, a combustion experiment is made in a micro combustion vessel to confirm the lower limit of the combustor size and quench distance. Based on an epitrochoidal-shaped housing the small-scale rotary engine is designed. For its planar construction, the rotary engine is available to the MEMS manufacturing techniques such as DRIE, LIGA, DEM, EDM, and is also suitable for micromation. While in the experiment, it is founded that with the housing of the engine with epitrochoidal-shape expanding, the engine couldn’t work steadily. Thus the analysis and simulation of heat transfer and thermal-stress are made to modify the contour of the epitrochoidal-shaped housing. Besides, the single-rotor construction, oil film face seals, and springs apex seals are adopted in the design. A series of small-scale rotary engines (including M2.4, M1.5 and M0.75 rotary engine) have been designed and fabricated from steel by using electro discharge machining (EDM). Test platforms for small-scale rotary engines have been developed and experiments have been conducted respectively, in which liquid hydrocarbons fueled small-scale rotary engines and high-pressure air driven small scale rotary engines to examine the effects of sealing, ignition, design, and thermal management on efficiency. The preliminary test of the M2.4 rotary engine (compressed chambers is 166 mm3, swept displacements is 2600 mm3) fueled by liquid hydrocarbons has shown steady 150 W net power output at 15000 RPM. The preliminary test of the M0.75 rotary engine (compressed chambers is 9 mm3, swept displacements is 143 mm3) can output 1.5W net power at 14000 RPM with high-pressure-air driven. Testing of the small-scale rotary engine has verified the feasibility of the micro-engine. However, heat loss and sealing issues are the key points for efficient operation of the micro-engine, and they must be taken into account in its design and fabrication to improve the design of sealing and micro combustion chamber.
Wave maker is one of the most important experimental equipment in marine engineering. To meet the demands of simulation of higher wave amplitude and compare the effect of piston and flap type wave generation, a new wave generation device was proposed and a new piston and flap type wave maker with a rotary-valve-control vibrator was developed. A mathematical model of the new wave maker was established and analysed by Simulink, and a series of experiments were conducted on the wave maker to analyze wave generation characteristics. The results show that the wave maker can adjust the distance of wave paddle and generate different regular waves. The bigger the axial opening size of the valve port, the larger the wave paddle amplitude and the wave amplitude; the higher the pressure, the higher the wave paddle amplitude and the wave amplitude. High frequency wave making is more efficient than the lower one, and piston type wave making is more efficient than those wave makers that generate waves by flap type.
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
334 Leonard St
Brooklyn, NY 11211
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.