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The purpose of this study is to develop an all in one and maintenance free power-generating facility for river, ocean or tidal flow. A rotating shaft with turbine, power generator, and auxiliary systems are installed in the same axial line and under water level. This architecture can reduce the mechanical loss and increase the efficiency of electri...
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... the shaft seal that can separate between oil and gas had been developed, the shaft seal that can separate between water and air with low frictional torque have not been developed in the past. Figure 3 represents two types of representative shaft seals (a mechanical cover and an oil seal) that have been used as commercial parts. A mechanical seal consists of two main parts: the first ring rotating with the mile and a stationary mating ring with a mechanical body as part of a constant. ...
Citations
... To capitalize these resources, an ideal power generation system has been proposed, in which a rotating shaft with a turbine, dynamo, and ancillary systems are installed in the same straight line below the sea level. In such a generation system however, an excellent shaft seal is required in order to increase the separation ability between the water and air phases and to decrease the frictional loss (Topaloglu et al., 2016;Nakanishi et al., 2014;Chikaura rt al., 2014). ...
In ocean current and tidal power generation systems, the rotating shaft, which connects the turbine in water phase and the generation system in air phase, experiences a variety of shaft speeds and high water-pressure conditions. The shaft seal is required to separate water and air with a rotating shaft, which should guarantee both a low frictional torque and a low leakage of water. Conventional shaft seals realize the low frictional torque by operating in a hydrodynamic lubrication mode at the dynamic seal face. However, the dynamic seal face suffers to form rich lubrication film against low speed shaft in water environment. Therefore, a hydrated seal ring was proposed for use in the dynamic seal faces to realize the boundary lubrication. The hydrated seal ring made of a polyvinyl formal (PVF) was adopted. Two types of shaft seals using PVF seal ring were designed, which had the similar structure to oil seals or mechanical seals. The design scheme was validated using verification tests in which the shaft rotation speed was varied from 5000 to -5000 revolutions per minute under a water pressure of 0.5 MPa. The hydrated seal ring can be further improved by avoiding deformation of the hydrated seal ring to inhibit the clearance flow in the dynamic seal face. However, it needed to consider the surface profile of the ceramics surface used as a counterface of the hydrated seal ring because the heat generation at the dynamic seal face might be occurred, which changes the material property of the hydrated seal ring.
... For example, a new generation system has been developed that uses ocean currents as a renewable energy resource. Its turbines are submerged horizontally several tens of meters below the surface to efficiently capture the water flow (Shirasawa et al., 2016, Topaloglu et al., 2016, Honda et al., 2016, Nakanishi et al., 2016b, 2014, 2013. In such a situation, a shaft seal is needed to protect the mechanical or electrical elements from water ingress under high water pressure. ...
The lips of a shaft seal need to be lubricated to ensure its performance. Such seals are subjected to difficult conditions inside water pumps or underwater mechanical systems. Poor lubrication can cause high friction and wear of seal lips. A new shaft seal was designed to prevent water ingress with low friction and high wear resistance by adopting hydrophilic materials to seal rings. Hydrated composites for seal rings were developed with fibers to avoid excessive deformation. In experiments, cellulose nanofibers were most appropriate for reinforcement of the matrix material and the shaft seal exhibited its sealing performance at the speed of 5000 rpm under pressure of 0.8 MPa. This shaft seal will be useful not only for industrial pumps but also for generation systems driven by water flow, such as ocean current or streamflow.
... This topology has important advantages for small scale energy devices as indicated in Table 1, with high torque density, easily adjustable Voltage constant, simple design methodology, low cost of materials, and flexible fabrication methods available. The potential of this generator topology for small NCRE devices has been recognized by many authors and there are continuous efforts toward its improvement (Topaloglu et al., 2016;Probst et al., 2011;Vansompel et al., 2010;Holmes et al., 2005). ...
A design methodology, its validation and evaluation, for optimal electric energy power management NCRE (NonConventional Renewable Energy) converters used for battery charging is presented, targeting small-scale units (i.e. < 10 kW). It is a general-purpose solution that has been tested with different prime movers: river turbine, tidal turbine, wind turbine, and wave energy converter. There are two critical components in the configuration: the electric generator, and the buck converter or MPPT (Maximum Power Point Tracker). The design of these two components must give careful consideration to the behavior of the primary energy source as well as battery charging requirements. The topology selected for the generator is an axial flux generator with permanent magnets, because it allows matching the low optimal speed of the primary energy converters without the use of speed multipliers such as gears and pulleys. The programmable buck converter topology is selected because it can be used both as a voltage or current source, and hence it works well with battery charging,which is a primary application for small-scaleoff-gridNCRE converters. Cost-effectiveness of the solution is achieved by the simple design methods, low cost components and materials, and simple manufacturing methods.
... However, some situations necessitate the separation of water and air around a rotating shaft, such as in shaft seals used for turbine shafts in ocean current or streamflow power generation systems. 2,3 These turbine shafts are rotated very slowly by water current energy and submerged 10 to 100 m beneath sea level. Therefore, the shaft seal attached to the generation system must prevent water ingress under low-speed operation and high water pressure. ...
... In addition, the frictional loss caused by shaft seals should be minimised to increase the energy recovering efficiency. [2][3][4][5] Sliding materials need to be chosen carefully to achieve both a low frictional loss and an enhanced sealing function with water-based lubrication. 6 Appropriate materials for a new water-sealing system were suggested by artificially reproducing the lubricating mechanism of natural synovial joints, which exhibit excellent water-based lubrication. ...
Shaft seals with a seal lip are used in various applications to separate gases and fluids, but their sealing function and durability are affected by the extent of lubrication at the dynamic seal faces between a rotating shaft and the seal lip. A new sealing system consisting of two hydrated seal rings and non-Newtonian lubricants was designed by a biomimetic approach to minimise frictional loss and provide high waterproof function when separating air and water. This system demonstrates significant superiority in low-speed rotation, conditions under which the lubrication mechanism of an oil seal or mechanical seal does not generally work well. Fibre reinforcement of the seal ring material was performed to prevent the deformation of the soft seal rings because of the frictional force in the tangential direction of the shaft and water pressure. This reinforcement enabled the new sealing system to obtain both high waterproof performance and low frictional characteristics in the speed range of 20–100 r/min.
... So, the effect of cogging torque is very important. The cogging torque can be obtained using the magnetic energy stored in the air gap and PMs of machine as follows [48][49][50] Where R2 and R1 are the inner radius of armature and the outer radius of rotor, respectively; Q is the number of slots and θ is the rotor position. The expressions of Fourier expansion coefficients Gsn and Bsn are detailed in [48,49]. ...
This study reports the analytical computation including performance characteristics under no-load condition in combination with coupled 2D electromagnetic field-circuit analysis of a 4kW direct drive permanent magnet synchronous generator (PMSG) to be used in micro-scale wind turbine applications. The specifications such like stack length, skew and magnet offset of PMSG are optimized by using parametric approach including multi-objective design optimization. It describes the methodology to gain required output performance such as output power, load voltage and maximum efficiency of the wind generator. Based on the optimized design, the model has been exposed to some transient coupled-field circuit analyses based on variable wind flow speed under no-load conditions. In addition to these evaluations; the experimental results verified the effectiveness of the employed simulations model related to finite element methods and analytical studies showing that that the induced voltage at nominal speed and no-load condition is at desired level and results obtained under no-load condition are in good agreement with the analysis and analytical results.
The use of wind energy as an alternative source of energy to generate the electricity is increasing worldwide. The application of an axial flux permanent magnet generator for small-scale wind turbine nowadays is increasing due to innovation, new material discoveries and completion in the manufacturing technology. The axial flux machines can be constructed with single-side, double-side and multi-stage topologies and can also be constructed with or without an iron core. Nine possible patterns between the single-side and double-side topologies with iron core and with surface-mounted permanent magnet method were designed in this study with the aid of the analytical method. To obtain the most qualified generator, there are six parameters used as constraints including flux density distribution, on-load terminal voltage, voltage regulation, total harmonic distortion, output power, and efficiency and analyzed with the finite element method from Maxwell-3D software. From the comparison, the generator type IX excited with rectangular poles is proven to be the most qualified generator among other generators in this case.
