CFD Simulation of Flow Pattern and Torque in Draft Tube Hydro Vortex Turbine

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CFD Simulation of Flow Pattern and Torque in Draft Tube Hydro Vortex Turbine Made Suarda1, I Putu Widiarta2 1Asst. Professor, Mechanical Engineering Study Program, Udayana University, Badung, Bali, Indonesia

2Asst. Professor, Mechanical Engineering Study Program, Udayana University, Badung, Bali, Indonesia

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Abstract - Vortex turbines are widely developed because of

innovations to improve the performance of vortex turbines, one of which is the torque on the runner. Efforts to improve the performance of vortex turbines are carried out both experimentally and through CFD (Computational Fluid Dynamic) simulations. Some of the main aspects that are the object of research are making modifications to the main components of the turbine such as the notch angle of the turbine channel, the height and shape of the basin and the profile of the turbine blades and the vortex turbine basin [7].

their advantages in being able to be applied to low flow heads and their simpler construction, making them suitable for application in mountainous areas. The efficiency of vortex turbines is still relatively low, thus triggering many innovations to be carried out to improve the performance of vortex turbines by conducting research both experimentally and through CFD simulations. In low pressure vortex turbines, it is used to create an air core so that a vortex flow can be created. On the other hand, a low-pressure area that is too high in the turbine runner area causes the conversion of vortex flow energy and turbine torque to be less than optimal, so it is necessary to add a turbine flow control mechanism, namely a draft tube. Adding a divergent draft tube model to the basin outlet channel results an increase in the pressure value around the turbine runner and enhances the turbine torque by 22.7%.

Research that has been conducted to improve the performance of vortex turbines such as conical turbine basins produces higher turbine efficiency compared to cylindrical basin models [8]. Increasing the value of the vortex turbine notch angle can increase the flow velocity from the channel moving towards the turbine basin so that the resulting vortex becomes more optimal [9, 10]. The runner immersion position affects turbine performance where optimal vortex turbine efficiency can be obtained at a runner immersion position of 65-75% of the basin height [11]. The addition of a booster runner can increase the power of the vortex turbine by 20.4% this is because the vortex energy at the bottom of the basin is reused to rotate the booster runner [12]. On the other hand, the rotation of the turbine runner affects turbine performance where optimal efficiency is obtained at a turbine rotation of 90 rpm [13]. Research conducted by Kim et al. (2021) added a smalldraft tube configuration at the vortex turbine outlet channel which has an effect on increasing runner torque due to the low-pressure area being maintained with a draft tube so that it can increase the pressure drop in the turbine runner area [14]. The function of the draft tube is to convert the flow velocity energy in the outlet channel into flow pressure energy and can control the outlet mass flow. In low pressure vortex turbines are used to create an air core so that a vortex flow can be created, on the other hand, a low-pressure area that is too high in the turbine runner area causes the conversion of vortex flow energy and turbine torque to be less than optimal because the air core space is too high causing the runner area affected by the vortex flow to be reduced [15]. Thus, a flow control mechanism is needed to improve turbine performance, namely the vortex turbine torque.

Key Words: Vortex turbine, draft tube, flow phenomena, torque, vortex turbine

1.INTRODUCTION Energy is a crucial factor in the sustainability and advancement of human civilization. The primary energy source is fossil fuels. The downside of fossil fuels is that they are not environmentally friendly and are non-renewable [1].

These issues have prompted a shift towards more environmentally friendly and renewable energy sources.

Several renewable energy sources, such as air, solar energy, and water, are being utilized as more environmentally friendly alternatives for generating electricity. Water energy is used to drive turbines, which in turn drive alternators, thereby generating electrical energy [2].

Water turbines can generally be classified into two types in terms of flow energy conversion, namely impulse turbines and reaction turbines. Impulse turbines are turbines that utilize flow velocity energy to generate momentum on turbine blades while reaction turbines are turbines that utilize changes in working fluid flow pressure [3], [4].

Nowadays, vortex turbines are widely developed because of their advantages that can be applied to low flow heads and simpler construction so that they are suitable for application in mountainous areas [5]. The way vortex turbines work is by utilizing the vortex flow created in the turbine basin to drive the turbine runner [6]. The efficiency of vortex turbines is still relatively low so that it triggers many

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Based on the literature review conducted, further research is needed on the addition of a draft tube with a divergent draft tube configuration to the vortex turbine outlet. The purpose

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2.2. Simulation modeling

of this study is to analyse the effect of the addition of a draft tube applied to the vortex turbine basin outlet on the vortex turbine flow and torque phenomena. The study was conducted using CFD simulation using Ansys Fluent software and tested at the same mass flow.

CFD simulations generally consist of three main processes: pre-processing, solving, and post-processing. Pre-processing is the stage of creating a rotating fluid domain and a stationary fluid domain, as well as performing the meshing process. The mesh type used is the poly-hexcore type, which is a combination of a poly and a hexcore mesh. The fluid domain and mesh are shown in Figures 2 and 3. The mesh results statistics are shown in Table 1.

2. METHODS 2.1. Research Scheme The geometry of the study was carried out by adding a draft tube to the vortex turbine outlet channel as shown in Figure 1. The main components of the vortex turbine consist of a channel (1), Inlet of the channel (2), outlet of draft tube (3), basin (4), runner (5) and draft tube (6). The vortex turbine works by channeling the flow capacity flowing in the channel to the turbine basin. In the turbine basin, the flow is converted into a vortex flow and used to drive the runner so that the turbine runner can produce torque and turbine output power.

(a)

(b) Fig -2: Fluid domain: (a) without draft tube, (b) with a draft tube

Fig -1: A vortex turbine equipped with draft tube

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Fig -3: Poly-hexcore mesh results in view clipping mesh

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3.1 Existing Overview of Nusa Penida DWSS

Table -1: Mesh Statistics

The fluid pressure and velocity contours around the runner were taken at the middle, top, and bottom positions of the runner. Figure 5 shows the distribution of pressure contour results and Figure 6 shows the distribution of velocity contours around the turbine runner. The addition of a draft tube to the vortex turbine basin outlet channel causes an increase in the flow pressure value around the turbine runner. The increase in flow pressure caused by the lowpressure area at the basin outlet can be minimized by the draft tube which causes a change in flow pressure in the turbine basin where the kinetic energy of the flow is converted back into pressure energy by the shape of the draft tube configuration, namely divergent. On the other hand, the addition of a draft tube causes the distribution of low pressure around the runner without a draft tube to be reduced so that the turbine runner is more evenly exposed to the vortex flow so that the resulting torque can be increased.

Without Draft Tube Cell’s

966311

Face

4480477

Node

2829888

Average orthogonal quality

0.9458259

Equipped with a Draft Tube Cell’s

917334

Face

4269589

Node

2701611

Average orthogonal quality

0.94381102

The solver process is the process of determining the simulation boundary conditions such as wall, inlet, and outlet.

The simulation boundary conditions are shown in Figure 4.

Where the inlet condition is set to mass flow inlet, the wall is set to non-slip condition, and the outlet is pressure outlet.

The outlet pressure in the test without a draft tube is set to 0 atm (gauge pressure), while in the outlet condition with the addition of a draft tube, it is set to 2.970 Pa (gauge pressure), where this condition indicates a submerged draft tube (tail race). The turbulence model used in the CFD simulation is komega SST with the SIMPLE (Semi Implicit Pressure Linked Equation) scheme solver, where this solver connects the pressure and velocity values to obtain the mass flow conservation value.

(a)

Fig -4: CFD simulation boundary conditions

(b)

3. RESULTS AND DISCUSSION

Fig -5: Pressure contours: (a) without draft tube, (b) equipped with draft tube

The residual results of the CFD simulation, namely momentum in each direction x, y and z, reached a residual value of e-05, while k and omega and continuity were able to reach a residual value of e-04.

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The flow velocity distribution around the turbine runner tends to remain unchanged with the addition of a draft tube to the vortex turbine basin outlet channel as shown in Figure 6. This is because the turbine is simulated at the same runner

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distributed over the vortex turbine runner area so that the flow area that hits the runner can be optimized.

speed of 90 rpm, therefore, the runner rotation is controlled and maintained constant. Thus, the velocity distribution around the runner has a tendency to have the same velocity value in variations with and without the addition of a draft tube.

(a)

(a)

(b) Fig -7: Streamline: (a) without draft tube, (b) equipped with draft tube

(b)

3.3 Torque of the vortex turbine

Fig -6: Pressure contours: (a) without draft tube, (b) equipped with draft tube

3.2 Streamline The flow streamline was created with 100 tracking points to obtain the flow path. Figure 7 shows the flow streamline in a vortex turbine with and without the addition of a draft tube.

The addition of a draft tube to the outlet basin channel causes a change in the path phenomenon of the vortex flow in the turbine basin. The vortex flow after hitting the blades on the turbine without the addition of a draft tube tends to be directed in an axial direction so that the flow falls freely and exits towards the turbine outlet channel. This phenomenon causes the flow streamline to be unevenly distributed over the vortex turbine runner area and can affect the resulting torque gain. On the other hand, adding a draft tube to the outlet basin channel can change the flow phenomenon from axial flow near the outlet channel to tangential flow. This phenomenon can be observed from the flow streamline. The change in flow phenomenon due to the effect of the addition of a draft tube causes the flow streamline to be more evenly

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Fig -7: Streamline: (a) without draft tube, (b) equipped with draft tube

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Figure 8 shows the torque of a vortex turbine with and without the addition of a draft tube from the CFD simulation results. The simulation results show that a vortex turbine with the addition of a draft tube at the outlet channel causes an increase in the torque value on the turbine runner, a similar finding was also found in research conducted by Kim et al. (2021). In research conducted by Kim et al. (2021) the addition of a small draft tube caused a 3% increase in torque [14]. The increase in torque value is caused by an increase in the flow pressure value and a more even flow streamline around the turbine runner as shown in Figures 5 (b) and 7 (b). A higher flow pressure value produces a higher force when it hits the turbine blade area. The greater the force that can be generated with the same runner diameter, the turbine torque can be increased where the turbine torque is the multiplication of the force and the runner radius. Meanwhile, a more even streamline causes the wetted area on the runner to be more evenly distributed.

[4]

Karre, R. K., Srinivas, K., Mannan, K., Prashanth, B., & Prasad, C. R. (2022). A review on hydro power plants and turbines. AIP Conference Proceedings, 2418. https://doi.org/10.1063/5.0081709

[5]

Dhakal, S., Timilsina, A. B., Dhakal, R., Timilsina, A. B., Dhakal, R., Fuyal, D., Ratna Bajracharya, T., & Pandit, H. P. (2014). Effect of Dominant Parameters for Conical Basin: Gravitational Water Vortex Power Plant.

Proceeding of IOE Graduate Conference. https://doi.org/10.13140/RG.2.1.1455.7843

[6]

Rahman, M. M., Tan, J. H., Fadzlita, M. T., & Wan Khairul Muzammil, A. R. (2017). A Review on the Development of Gravitational Water Vortex Power Plant as Alternative Renewable Energy Resources. IOP Conference Series: Materials Science and Engineering, 217(1). https://doi.org/10.1088/1757-899X/217/1/012007

3. CONCLUSIONS

[7]

Maika, N., Lin, W., & Khatamifar, M. (2023). A Review of Gravitational Water Vortex Hydro Turbine Systems for Hydropower Generation. In Energies (Vol. 16, Issue 14).

Multidisciplinary Digital Publishing Institute (MDPI). https://doi.org/10.3390/en16145394

[8]

Aziz, M. Q. A., Idris, J., & Abdullah, M. F. (2022).

Simulation Of the Conical Gravitational Water Vortex Turbine (GWVT) Design in Producing Optimum Force for Energy Production. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 89(2), 77–91. https://doi.org/10.37934/arfmts.89.2.99113

[9]

Bajracharya, T.R., Timilsina, A. B., Ghimire, R. M., & Timilsina, A. B. (2018). Design And Performance Analysis of Water Vortex Powerplant In Context Of Nepal Comparative Study of Gaseous and Particulate Emissions from Traditional and Modified Charcoal Production Kilns View Project Computational modeling (atomistic, nanoscale and mesoscale simulations) of materials. View project DESIGN AND PERFORMANCE ANALYSIS OF WATER VORTEX POWERPLANT IN CONTEXT OF NEPAL. In 20 th International Seminar on Hydropower Plants. https://www.researchgate.net/publication/330083382

The addition of a draft tube to the vortex turbine basin outlet with a divergent configuration can increase the flow pressure around the vortex turbine runner area. The addition of a draft tube also causes the flow streamlines around the turbine runner to occur more evenly compared to without the addition of a draft tube. The addition of a divergent draft tube increases runner torque by 22.7%.

Suggestions for future research is examining variations of the draft tube dimensional configurations to achieve optimal performance.

ACKNOWLEDGEMENT The authors would like to express their gratitude to the Mechanical Engineering Study Program, Faculty of Engineering, Udayana University.

REFERENCES [1]

Perera, F., & Nadeau, K. (2022). Climate Change, FossilFuel Pollution, and Children’s Health. New England Journal of Medicine, 386(24), 2303–2314. https://doi.org/10.1056/nejmra2117706

[2]

Ng, S. K., Nakayama, A., & Ng, W. X. (2024). Application of Smoothed Particle Hydrodynamics Method for the Analysis of the Flow Past Vertical Vortex Turbine of a Micro Hydropower. KSCE Journal of Civil Engineering, 28(3), 1132–1139. https://doi.org/10.1007/s12205024-1732-x

[3]

Peng, N., Wang, E., & Wang, W. (2023). Design and analysis of a 1.5 kW single-stage partial-admission impulse turbine for low-grade energy utilization. Energy, 268. https://doi.org/10.1016/j.energy.2023.126631

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[10] Sukadana, I. G. K., Suarda, M., Widiarta, I P., & Danus, I.

(2024). CFD (Computational Fluid Dynamics) Simulation of Hydrodynamic Vortex Turbine Performance: Influence of Notch Angle Variation on Flow Patterns and Efficiency. Natural Sciences Engineering and Technology Journal, 4(2), 336–351. https://doi.org/10.37275/nasetjournal.v4i2.56 [11] Bajracharya, T.R, Timilsina, A. B., Niraula, R., Timilsina,

A. B., Niraula, R., Rasaily, B., Lama, M., & Pathak, P. (2022). Effect Of Stay Vanes in Gravitational Water Vortex Power Plant with Spiral Basin. 21st International Seminar on Hydropower Plants-Hydropower for future

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generations, 09-11 November, Vienna, Austria. https://www.researchgate.net/publication/370301646 [12] Dahal, N., Shrestha, R. K., Sherchan, S., Milapati, S.,

Shakya, S. R., & Jha, A. K. (2020). Performance Analysis of Booster based Gravitational Water Vortex Power Plant. Journal of the Institute of Engineering, 15(3), 90– 96. https://doi.org/10.3126/jie.v15i3.32026 [13] Gusti Muttaqin, I., Sucipta, M., & Suarda, M. (2022).

Computational Fluid Dynamic Simulation on Vortex Turbine Model with Runner Rotation Speed Variation (“Simulasi Computational Fluid Dynamic Pada Model Turbin Vortex Variasi Kecepatan Rotasi Runner”).

Sibatik Journal. Jurnal Ilmiah Bidang Sosial, Ekonomi, Budaya, Teknologi, Dan Pendidikan, 1(8), 1445–1454. https://doi.org/10.54443/sibatik.v1i8.188 [14] Kim, M.S., Edirisinghe, D. S., Yang, H.-S., Gunawardane, S.

D. G. S. P., & Lee, Y.-H. (2021). Effects of blade number and draft tube in gravitational water vortex power plant determined using computational fluid dynamics simulations. Journal of Advanced Marine Engineering and Technology, 45(5), 252–262. https://doi.org/10.5916/jamet.2021.45.5.252

[15] Sinaga, D. A., Septiyanto, M. D., Arifin, Z., Rusdiyanto, G.,

Prasetyo, S. D., & Hadi, S. (2023). The Effect of Blade Distances on the Performance of Double-Stage Gravitational Water Vortex Turbine. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 109(1), 196–209. https://doi.org/10.37934/arfmts.109.1.196209

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