Figure 4: Primary mounting methods for axial turbine 
There are several advantages and disadvantages to each mounting method. Rivers and tides have faster water velocities near the surface, meaning that turbines mounted with FSMs or NSMs may be able to generate more power than those mounted with BSMs. However, the energy output from turbines mounted with NSMs may fluctuate depending on the water level. Furthermore, turbines mounted with FSMs and NSMs may get in the way of other river applications, such as naval shipping, recreational boating, or other uses. FSMs also lead to construction challenges, whereas BSMs have abundant civil engineering precursors. On the other hand, turbines mounted with BSMs are difficult to repair or inspect and have larger ecological effects due to their locations. Other factors include the size and mass of the turbine and the constraints on the hardware such as gearboxes and generators .
Abstract- This research concentrates on the impact of diffuser and nozzle angles as changed parameters on flow velocity at diffuser passage. Diffuser length, nozzle length, throat diameter are fixed and diffuser and nozzle angles are varied 5̊ to 30̊ and 5̊ to 15̊ while the flow field analysis has been carried out using commercial software ANSYS CFX .The simulation results also show that diffuser and nozzle angles at (30̊,15̊) are the optimum angles that accelerates flow to the turbine. The velocity at these optimum angles are higher than other angles which cause the turbine can generate more power output. After getting the optimal inlet- nozzle diffuser design, numerical analysis for the designed hydrokinetic axial flow turbine with inlet-nozzle diffuser have been performed by using ANSYS CFX. This study also focuses on the flow velocity and pressure variation around the turbine due to the effect of inlet nozzle diffuser. Hence, the installation of diffuser around the conventional turbine significantly increases its power output capabilities. The proposed turbinedesign is intended to use at the irrigation channel so that turbine diameter and flow velocity is considered based on the selected location. According to the simulation results, incoming velocity 1.50 m/s at the throat of the turbine was increased up to 4.03 m/s and the preliminary designed turbine power output 210 W was increased to 288 W by installing inlet-nozzle diffuser to the hydrokinetic axial flow turbine.
= 2100/3700 = 5.71years, (12) 5.0 Conclusions and recommendations An experimental helical hydro turbine has been designed, fabricated and tested on small river stream in Kenya. The research has provided very important information with regard to local manufacturing of turbines for utilization of water currents especially in small river streams in Kenya. The results show that as the power output from the turbine increases with water velocity which also increases the tip speed ratio and thus proving that the turbine is able to extract available hydraulic power from the small river water flows. This project demonstrate a simple appropriate technology that can provide access to electrical power and water pumping for marginalized areas in Kenya and other developing countries. IRR
Numerical simulations using the Blade Element Momentum Theory (BEMT) have been carried out to validate the analytical findings. An easy approach to optimizing the blade twist to obtain maximum power is suggested, which involves maximizing the tangential aerodynamic force generated by the airfoil at each blade element and azimuth position. Various parametric studies are carried out to study the variation of the rotor performance with these parameters. Four system configurations have been studied in detail and the performance of each of these systems is correlated with multiple design parameters. It is observed that a dual coaxial rotor is more efficient than a single rotor (with 2 blades per rotor) for the range of yaw angles in interest (55 𝑜 , 90 𝑜 ). The other major finding from this analysis is the variation of optimal Tip Speed
It should be kept in mind that this hydrokineticturbine works in an open channel system, so the water flow rate is limited. The water flow rate has a maximum limit, because if the channel exceeds the ability to accommodate the water flow rate, then the water will overflow above the channel or overflow above the turbine. So that, there will be no additional energy if the water supply is given more than the maximum water flow rate. This principle is in accordance with the calculation of a maximize irrigation allocation mentioned by Rispiningtati . The excess water flow that is not useful, may also give the effect of the river overflow (flooding).Based on some of these considerations, it is hoped that a hydrokineticturbinedesign could reach a better performance based on this simulation research. So, if there are shortcomings and a poor design, then this hydrokineticturbinedesign could be corrected and be optimized before being tested in the laboratory.
something that they could do in house. Our marine contractor Pepperrell Cove Marine Services suggested looking into the use of rollers to support the spanning beam. A company called Sunray Inc. was found. Sunray specializes in the production of custom built rollers. They were able to provide 6 inch long polyurethane rollers with a 2.5 inch OD and 0.75 inch bore with stainless steel ball bearings rated at 3,500 lbs. These rollers could be used to create a large custom roller bearing for the spanning beam that would withstand the load and be able to accommodate a 16 inch shaft. On each side of the spanning beam the beam is supported by 8 of these rollers. The rollers are sup- ported within a housing called the beam cradle. The beam cradle supports the rollers and transfers loads from the spanning beam to the rollers into large base plates into the TDP. The components of the beam cradle which support the rollers are bolted such that in the event of a roller failure, an air powered lifting bag can be inserted under the spanning beam to lift the spanning beam and the roller can be un-bolted and replaced. During the design of the TDP the I-beams around the moon pool were reinforced with stiffeners and holes were drilled in multiple locations along the edges of the moon pool to allow for the mounting of the turbine and the device which would pivot the turbine rotor out of the moon pool in multiple possible locations. It was decided that the turbine should be mounted as close to the center of the TDP as possible to keep the center of gravity of the TDS close to the center of the TDP.
This paper presents the sizing of the blades of a 1 kW hydrokineticturbine with 3 blades with hydrodynamic multi- element profiles using the Blade Element Momentum theory (BEM). The hydrodynamic profile used was the Eppler 420. The turbine was designed from a water flow velocity of 1.5 m/s with a tip speed ratio of the blade (λ) of 6.325, a pitch angle of the blade section (θ) of 0°, a power coefficient of 0.4382 and a mechanical efficiency of 70%. The Eppler 420 multi-element profile was selected for the design of the blade because it has a high ratio between the lift coefficient and the drag. A 2D computation study in the JavaFoil code of the Eppler 420 profile was carried out in order to determine the optimal lengths of the main element and the optimal flap for a deflection angle of 30° under conditions of a low Reynolds number.
The discussion of the number of blades in hydrokinetic or wind turbine is not too explored. Only a few references discussing the hydrodynamical effects on the choice of the number of blades are reported in the literature. Duquette et. al. [ 19 ] discussed the effect of the number of blades and the runner solidity for small wind turbines. This work con- cludes that the optimum design three-blade rotors produced an increase in the experimental power coefficient—Cp as solidity increased, with reduced tip speed ratio (TSR) at the optimum operating point. As blade number was increased at a constant solidity, the aerodynamic efficiency and power sharply decreased, contrary to the classical suggestion of Glauert [ 7 ] that pointed out the increase in Cp with the num- ber of blades. In fact, the experimental work of Duquette does not explore properly the best optimum design for the given number of blades. Duquette et. al. [ 19 ] just change the number of blades in the rotor without making modification in the blade design. In the Glauert theory, the solidity has to be changed for the optimum design geometry, for each different number of blades.
1.2.3. Hydrokinetic turbines: A technology review. Hydrokinetic power utilization started in 1978 with the development of the Garman Turbine for water
pumping and irrigation . Within a period of four years, a total of nine prototypes were built and tested on the White Nile (in Juba, Sudan) having a total of 15,500 operational hours. More recent commercial applications include turbines built by various companies in Europe, USA and Canada such as Rutten Company, Belgium , Tyson turbine , Marlec Engineering Co. Ltd. , Verdant Power  and Alternative Hydro Solutions Ltd., Canada . A detailed list of all the existing hydrokinetic projects is given in Table 1.2. The Kinetic Hydro Power System (KHPS) developed by Verdant Power consists of a 5 m diameter three-bladed axial flow turbines rated at 35 kW and operates over a large range of speeds. The turbine rotor is coupled by a step up gear box which drives a grid-connected three-phase induction generator. The turbine operates at 1-2 m/s at a minimum water depth of 6 m in rivers, tidal estuaries and near shore oceans . Hydro Green Energy LLC/Inc. has developed dual duct, axial flow, zero head current- based turbine arrays of 350 kW power capacities operating in river, ocean and tidal settings . The turbines possess high capacity factors (more than 90%) for in-stream river and ocean current applications and surface suspension system provides operational maintenance and safety advantages. Thropton Energy Services manufactured a pontoon- mounted, low power, propeller fan style turbines designed as stand-alone units having maximum power output of 2 kW . Marlec has teamed up their engineering and manufacturing expertise with Thropton Energy Services to develop Amazon Aqua Charger, a battery charging water current turbine. The turbine is lowered into a river or canal deeper than 1.75 m and generates power between water speeds 0.45-1.5 m/s. The tidal turbine generator developed by Clean Current Power Systems consists of a bi- directional ducted horizontal axis turbine with a direct drive variable speed permanent magnet generator. The commercial scale model is 14 m in diameter with 250 kW
turbines are vortex lattice methods and free-vortex wake methods. With growth of computation power in the 1970s, vortex lattice models were developed and employed for analyzing Darrieus-type turbines. Vortex lattice models are based on potential ow theory while the eects of uid viscosity are usually inserted as modications. In 1979, Strikland presented one of the three-dimensional models for ow analysis based on vortex lattice model. He could model airfoil stall by combining the Kutta-Joukowski law and experimental data of airfoil sections . Many numerical modeling techniques such as disk-stream tube and vortex panel methods have limitations in predicting transient per- formance of hydrokinetic turbines. According to the literature, implementation of modern CFD methods for three-dimensional modeling of transient uid ow around ducted hydrokineticturbine has gained great attention. Computational uid dynamics modeling coupled with single-degree-of-freedom motion of rotor is a perfect solution for predicting performance of hydrokinetic turbines . The maximum energy that a single-stage axial turbine can absorb from uid is widely accepted in the turbine industry and is known as Lanchester-Betz limit . In 2003, Kirke compared performances of ducted and unducted hydrokinetic turbines. He experimentally studied the eect of duct on increasing ow velocity through duct and named it diuser-augmented turbine . In 2003, Lawn studied performance of axial ow ducted turbine analytically using a one-dimensional theory . Based on the re- sults of Lawn, with a diuser-augmented hydrokineticturbine, the power coecient can increase over 30% when compared to unducted turbines . In 2004, Setuguchi et al. tried for designing and manufacturing a duct with two passages . They found that a key factor for increasing the eciency of the duct is its shape. In 2004, in United Kingdom, Bryden et al. developed a one-dimensional open-channel model. They investigated maximum attainable energy by an axial hydrokineticturbine. Based on their ndings, the maximum extractable energy was 10% of undisturbed ow kinetic energy [10,11]. In 2005, Garrett et al. studied maximum attainable energy by a fence of axial hydrokinetic turbines [12,13]. They presented an equation to predict the maximum power of the fence of turbines based on developed pressure gradient. In 2009, Munch et al. numerically investigated a four- blade ducted tidal turbine. They numerically simulated transient turbulent ow in ANSYS CFX Software. They showed that with tip speed ratio of seven, the turbine power coecient exceeds 55% . In 2010, Crawford and Shives numerically simulated overall eciency of a ducted tidal turbine using ANSYS CFX Software . They showed that the power coecient of a turbine can increase while the turbine eciency is reduced due to induced drag force. In 2012, Shives and
Harnessing electricity from ocean-currents is similar to the ones described in the literature mentioned in the previous sections. Most of the components like blades, generators, en- ergy storage systems are either readily available or have already been heavily researched in the past, since a lot of those systems are already in use in the wind power industry and have been recently adapted to harvest hydrokinetic energy from river currents and tides. A noteworthy feature of generating power from sources like ocean currents is that they are unidirectional in nature (unlike tidal applications) and hence, even more predictable. A major source for hydrokinetic energy extraction for the state of North Carolina in particular, and the east coast of the US in general, is the Gulf Stream . The Gulf Stream is a strong ocean current in the Atlantic that originates in the Gulf of Mexico, flows around the tip of Florida, and goes along the east of coast of North America before heading towards the west coast of Europe. Figure 1.6 & Figure 1.7 are some snapshots and illustrations of the Gulf Stream. One of the major challenges in extracting energy from the gulf stream is the variability in its position. The gulf stream is known to exhibit a meandering trait [4, 12], i.e. a lateral shift in its position estimated to be on the order of 40km. Furthermore, this lateral shift does not follow a periodic pattern which makes it all the more challenging to deal with. This presents a major problem since a turbine installed at a particular point in the gulf stream would be rendered ineffective for a major part of the year as the gulf stream meanders. This leads to a case of operating an ineffective sys- tem. To mitigate this challenge, a relocatable turbine could be employed to extract energy throughout the year. Such a relocatable energy harvester can be achieved by integrat- ing HydrokineticTurbine technology with Underwater Vehicle (like AUVs) technology to create a Mobile Under Turbine System (MUTS), a relocatable device that efficiently extracts Gulf-Stream Marine Hydrokinetic Energy (GS-MHK). Figure 1.8 shows a com- parison of the energy harvested by a stationary turbine and a relocatable turbine (turbine diameter = 1m, rated speed for relocatable turbine = 2m/s). It can be seen from the aforementioned illustration that by using a relocatable harvester, the harvested energy can easily be doubled. Such a device would also present the following advantages when compared to other existing energy extraction technologies:
Based on the characteristics of the cyclic symmetry for the structure of the hydrokineticturbine rotor (Fig. 2), a rotor sector conformed of a blade and a hub angle of 120 ◦ was used to run the CFD simulation. The computational domain was divided into two parts: an inner rotatable part, with high density of elements, and an outer stationary part with low density elements . Accordingly, a rotational periodic boundary condition was applied across the back and bottom surfaces of the computational domain shown in Fig. 3. The computational domain was created using Nx and meshed in ANSYS ICEM CFD. The mesh used was an unstructured (primarily hexahedral) mesh with very ﬁne prims layer near the turbine walls. All dimensions of the boundary were given in terms of radius (R) of the turbine. The turbine possesses 120 ◦ periodicity and, hence, only one blade was modeled. Figure 3 shows the location of the turbine within the computational domain. The turbine rotational plane was located R away from the inlet, and the ﬂuid domain was extended 7R behind the turbine rotational plane to capture the near and far wake eﬀects. Through previous numerical simulations, it was check that the domain length (7R) was adequate to guarantee that the ﬂow is fully developed downstream of the turbine. The radius of the blade was always ﬁxed during the study, only the section pitch angle of the blade (γ) was varied between 0 ◦ and 90 ◦ to determine the relationships between turbine geometrical design and performance.
Micro hydro refers to projects that generate between 0.5 kW and 100 kW of power, which is the amount typically required to power a single family home or small businesses . Small hydrokinetic systems fall within this micro-hydro category and offer the added benefit of portability. These characteristics are especially desirable in temporary encampment situations such as military field operations. A photovoltaic battery system called the Ground Renewable Expeditionary Energy System, or GREENS, has been developed for use by the U.S. Marine Corps to produce 300 W of continuous power to run these encampments . However, when sunlight is not available, a secondary source of energy is needed to power necessary equipment. A micro-hydrokinetic system could potentially interface with this system to provide the required power.
In design for a portable device, it is necessary to develop and understanding of reasonable flow predictions throughout the region where the device is intended to operate. Testing every location of every river within the United States is unreasonable and impractical. Therefore, data obtained by the United States Geologic Survey (USGS) from testing sites along each river is used to form base predictions and expectations of river flow. It is a base assumption that results from the sites collectively will adequately represent expected flow throughout the United States. Overarching goals of analysis are to determine the influence of various flow characteristics to determine how many rivers fall into various flow speeds, average water depth, and the percentage of sites from the data would be within an operable for a designed turbine with power goals in mind. River Data and Restricting Variables
DOI: 10.4236/jpee.2019.79004 64 Journal of Power and Energy Engineering ANSYS Fluent but most of the configuration had high flow separation which induced an adverse pressure gradient which greatly reduced the lift force and increased the drag force on the curved blade. The configuration shown in Figure 2 had low flow separation hence, it was considered as the structural configura- tion for the hydrokineticturbine for this research.
Hydrokinetic energy can be described as the energy that can be generated from flowing water that occurs in rivers or ocean currents. This includes ocean wave energy, tidal energy, river in-stream energy, and ocean current energy. As of today, there are not many hydrokinetic energy projects in commercial operation. However, there are several proposed wave energy projects worldwide, and a number of operating prototype systems under testing. River in-stream generating facilities are in the development stage with several operating prototypes being tested. Regardless of this comparatively low level of development, hydrokinetic energy resource has a significant potential, and it is a renewable resource which does not produce greenhouse gas and thus environmentally safe.
2. LITERATURE REVIEW
The manufacturing process of composite structures is quite complex. Specifically composite hydrokineticturbine blades, various parameters in terms of fiber/matrix type, reinforcement structure, laminate stacking sequence, environmental conditions, and loading conditions (Degrieck and Paepegem, 2001) can influence the fatigue behavior of composite blades. These factors will accumulate damage to the composite blade and either independently or interactively affects the fatigue life. As a result of the booming of wind industry, the fatigue life of composite structures with application to wind turbine has been studied considerably, especially turbine blades. A fatigue database regarding composite materials for wind turbine blades (Mandell and Samborsky, 2010) was established under the joint effort from Department of Energy and Montana State University. Detailed fatigue results for composite materials used for wind turbine under constant/variable amplitude fatigue loadings were included. Sutherland and Mandell (2005a, 2005b) evaluated the damage of wind turbine blades due to the effects of mean stress and an optimized constant-life diagram. Samborsky et al. (2008) studied delamination at thick ply drops in both carbon and glass fiber laminates subjected to the fatigue loading. Unlike commercialized wind turbine systems, detailed studies on composites for hydrokinetic/tidal applications are very few. There is a certain degree of statistical variability regarding fatigue loads. These factors include material uncertainty, variable water velocity, and scattered S-N data. Young et al. (2010) investigated the effect of material and operational uncertainties on the performance of self-adaptive marine rotors using reliability based design and optimization methodology. Lange (1996) revealed that fatigue reliability is highly dependent on the model chosen. In flatter S-N curves, the spread in failure probabilities for a given turbine life increased. Also, due to the complexity of composite manufacturing processes, blade-to-blade variation has been rarely investigated (Nijssen, 2006). It is indicated that the reliability based analysis is a must for the fatigue analysis of composite blades.
Mohammad Shahsavarifard et al.  studied that maximum power enhancement of 91% is obtained with straight wall duct compared to convergent-divergent duct. Martin Anyi et al.  studied the effect of clogging of debris and to remove them with the help of swinging blades. Kyu-Jung Chae et al.  deliberate the influence of Net head and turbine blade pitch in a semi Kaplan hydraulic turbine experimentally. A detailed experimental analysis of the effects of exit blade geometry on the part-load performance of low-head, axial ﬂow propeller turbines is presented by Punit Singh and Franz Nestmann . Priyono Sutikno et al.  presented an application of the minimum pressure coefficient and free vortex criterions for axial-flow hydraulic turbines cascade geometry design.
offer a high degree of reliability at a reasonable cost per installed KW.Power output of 200 watts was obtained with 80% efficiency. Paritosh singh et al.  carried out an analytical review of impulse and reaction turbine on the basis of type of action of the water on the blade. Here a modified gravitational Pelton wheel turbine was designed for low head and heavy discharge applications. Here the authors have come to the conclusion that reaction turbines are more efficient than impulse turbines. Prof .N.P.Jade et al.  undertook theoretical analysis of simple reaction water turbine for ultra-low head. An enhanced computer model of simple reaction water turbine was developed for optimum turbine sizing for a given head and speed. The turbine was tested in a free water stream environment and the maximum power generated was 8watts at 100 rpm which is too low. From the papers discussed, it is observed that results from studies that considered reaction turbines for low head conditions did not yield good results. The work described in paper  is about modifying a convention Pelton wheel for low heads. Here, no modifications to blade design were done and only effect of gravity on the turbine blades was analyzed. Hence, in this project an attempt has been made to make use of gravitational impulse turbine for power generation at low heads by utilizing the data obtained from the research papers.
Further Study (Optional)
Ask the students if they looked at “real” wind turbine blades while making their blades? How are they different or similar to your blades that you have created? If you can find some model airplane propeller blades develop a way to attach them to the hub and test. Make sure to turn these propellers around as on a plane they are designed to push air not “catch” it. Record the data from the low and high speed tests on the board. These blades may be much more effective than the ones they built. They may not if you have really smart students!