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Design and Velocity Distribution of Runner Blade of Kaplan Turbine Using CFD (Computer Fluid Dynamic) for Small Hydroelectric Power Plant To cite this article: E Permana and Y Rudianto 2017 IOP Conf. Ser.: Mater. Sci. Eng. 180 012269
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1st Annual Applied Science and Engineering Conference IOP Conf. Series: Materials Science and Engineering 180 (2017) 012269
IOP Publishing doi:10.1088/1757-899X/180/1/012269
International Conference on Recent Trends in Physics 2016 (ICRTP2016) IOP Publishing Journal of Physics: Conference Series 755 (2016) 011001 doi:10.1088/1742-6596/755/1/011001
Design and Velocity Distribution of Runner Blade of Kaplan Turbine Using CFD (Computer Fluid Dynamic ) for Small Hydroelectric Power Plant E Permana1, Y Rudianto1 1
Departement of Mechanical Engineering Education, Faculty of Technology and Vocational Education, Indonesian University of Education, Jln Dr. Setiabudhi No 229 Bandung, Jawa Barat, Indonesia.
E-mail:
[email protected],
[email protected]. Abstract. Procedures for designing runner of Kaplan water turbine based on the specific conditions in the water potential of the area to be placed, and assessed on the terms of the theoretical analysis and engineering. The main objective of this study was to determine the main characteristics of runners, namely suction head, water flow, and the hydraulic forces that occur when the turbine operates. Modern software for engineering such as computational fulid dynamics ( CFD ) is used to predict the flow of fluid passing through the runner and Computer Aided Engineering ( CAE ) to verify the design with Finite Element Analisys (FEA). Kaplan turbine runner is designed to place the suction head low and as an option for power generation in Galih Pakuan isolated from Ciwidey area and has not been electricity. The available head and flow rate for turbine are 8 m and 0,3 m3/sec in this site. The output power is 20kW estimated and turbine speed is 900 rpm, In designing blade, blade element theories are the main theories of blade parameter calculation. This paper selecting airfoil shape of the blade from Gottingen (GOE) series and modelling the exact airfoil geometry by using Airfoil.com software.
Keyword: CAE, CFD, FEA, GOE, Kaplan Turbine, Runner. 1. Introduction Geographically, Galih Pakuan village’s isolated from the Ciwidey, because it is located in the valley Patuha. The problems faced by the citizens are not interconnected electricity directly from PLN (Perusahaan Listrik Negara), so the state of the village a bit behind compared to other village in the Sugihmukti. In the face of such problems, the villagers exploit the potential of the river for the manufacture waterwheel as shown in Figure 1. Total waterwheel already installed a total of 35 turbines with a power output of each mill 100-150 watts, enough power to turn on the television and one light for each of the family, while the other 15 of families do not have a water mill and still request with neighbors. The potential of the initial survey conducted according to the data obtained, namely the existence of two streams that are parallel to discharge 0.3 m3/s and has a height difference (head) of 8 m between the position of the river that flows above and river below. Such conditions may
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1st Annual Applied Science and Engineering Conference IOP Conf. Series: Materials Science and Engineering 180 (2017) 012269
IOP Publishing doi:10.1088/1757-899X/180/1/012269
produce the hydraulic power of 23,544 watts and can be converted into electricity is 20,000 watts, the power reduction due to the efficiency of the turbine.
Fig. 1 Village’s water wheel Based on the head, and water discharge at this point, the power plant microhydro power can be created with specific Kaplan turbine to obtain high efficiency. This study explains the procedure for designing the runner on the water turbine Kaplan is based on local conditions (head H and debit Q) of the flow of the river in the village that have not been electricity, for the application of micro (50kW-100kW) use the Software modern engineering such as Computational Fulid Dynamics ( CFD) is used to predict the flow of fluid passing through the runner and Computer Aided Engineering (CAE) to verify the design with FEA (Finite Element Analysis). When the design process, the shape of the runner can be based on the typical flow optimization, and most importantly the runner can be produced. 2. Material and Methods The RBKP (Runner Blade of Kaplan Turbine) in the most important part of a rection turbine in the power generator. The runner, which is responsible of the conversion of hydraulic energy to mechanical energy, is the most vulnerable component since it is exposed to the load due the water pressure. The runner hasthree to six blade of airfoil shape; the number of blade depends of the spesifik speed. The runner blade are movable and can be change their position. The blade are assembly with bolt and nut on hubof RBKP. The fow enters the runner through gude vanes which have an angle fixed and runner is fully immersed in water, and must be strong enough to winhstand the operating pressure. The blade has very complex geometry that depends on the rated flow (Q) and net head (H) of the site in which the hudroelectric power plant is going to operate. The blade are comlex to manufacture due to their irregular shape, and the design is based on airfoil profiles, due to the blades ability to generate a big lift force and a relatively low drag force[1]. Based on empirically studies of Kaplan turbine schemes, correlation are established between the geometry of the runner (the runner exterior diameter De, or runner diameter, the runner interior diameter Di or hub diameter), the echanical power produce (P), the rotational speed (N), the specific speed (Ns), the net head (H) and the rated flow (Q). table 1 presents the aforementioned correalions (equation1-5), which can found in the literature. With these correlation it is possible to determinate the external diameter and internal diameter of the runner [1]. Table 1 Fundamental dimensions of RBKP. P = ηρgQH
(1)
2.716 H0.5
(2)
𝑁S =
De = 84.5 ∙ (0.79 + 1.602 ∙ 𝑁S ) ∙
2
√H 60 ∙ N
(3)
IOP Publishing doi:10.1088/1757-899X/180/1/012269
1st Annual Applied Science and Engineering Conference IOP Conf. Series: Materials Science and Engineering 180 (2017) 012269
Di = (0.25
Cm =
(4)
0.0951 ) ∙ De 𝑁S
(5)
4Q 2
2
(De − DI ) ∙ π
Where: P-generated mechanical power (watts), Q- Debit provided on the water flow (m3/s), NRotational of runner (rpm), Ns value specific rotation of the turbine, g Acceleration due to gravity (m2/s), H- Head / high water fall (m), ηh- hydraulic efficiency, cm -Speed axial turbine inlet (m/s), DeExterior diameter of runner / rotor (m), Di- interior diameter or the diameter of the hub (m). The design of the blade not only depends on the stress analysis, but also in othe several factor play a significant role. The leading edge is ticker than trailing edge for a streamlined flow. Furthermore, the blade should be as thin as possible to reduce cavitation effects. The blade tickher near the runner interior diameter becoming thinner towards the tip. The wing thery is also an important factor in defining the shape of the profile and the distortion of the blade. The velocity triangle are shown in table 2. Whre “u” is the tangential velocity, “c” is the absolute velocity and “w” is the relative velocity. When a cylindrical cut is set a the runner and the cut is develoved into a drawing plane, a grating like that shown table 2 occurs. In this figure, “x” represent the grating partition and “L” denote the chord. And approximate solution of the problem of the behaviour of the flow throught the blades can be obtained considering a constant plane of motin the grating[2]. Table 2 the velocity triangle, which occur on the blade 𝑢=
2𝜋𝑛𝑟 60
(6)
𝑔ηh 𝐻 𝑢
(7)
𝑐𝑢1 =
2 + (𝑢 − 𝑤∞ = √𝑐𝑚
(9)
𝜋𝐷𝑖 𝑧
(10)
𝑥 (𝑥⁄𝑙 )
(11)
𝑥=
𝜉𝑎
𝐿 2. 𝑔ηh 𝐻. 𝑐𝑚 = 2 𝑡 𝑤∞ . 𝑢. sin( 𝛽∞ − 𝜀)
𝜉𝑎 =
2. 𝑔ηh 𝐻. 𝑐𝑚 2 𝑤∞ . 𝑢. sin( 𝛽∞ −
tan 𝜀 = 0,012 + 0,06
𝛿=
3
(8)
𝑐𝑚 𝑐 𝑢 − 𝑢1 2
tan 𝛽∞ =
𝐿=
𝑐𝑢1 2 ) 2
𝑡 𝜀) 𝐿
𝑌𝑚𝑎𝑘𝑠 𝐿
𝑦𝑚𝑎𝑥 ) 𝐿 0,092
(𝜉𝑎 − 4,8
(12)
(13) (14)
1st Annual Applied Science and Engineering Conference IOP Conf. Series: Materials Science and Engineering 180 (2017) 012269
IOP Publishing doi:10.1088/1757-899X/180/1/012269
𝛽 = 𝛽∞ − 𝛿 𝐹𝐿 = 𝜉𝑎 𝐹𝐷 = 𝜉𝑤
𝜌 𝑤∞ 2 𝐿𝑏 2 𝜌 𝑤∞ 2 𝐿𝑏 2
𝐹𝑡 = [𝐹𝐿 sin(𝛽 − 𝜆) − 𝐹𝑎 cos(𝛽 − 𝜆)]. 𝑧
(15) (16) (17) (18)
𝐹𝑎 = [𝐹𝐿 sin(𝛽 − 𝜆) + 𝐹𝐷 cos(𝛽 − 𝜆)]. 𝑧
(19)
𝑇 = 𝐹𝑡 × 𝑟
(20)
where: 𝑟 =
(𝐷𝑖 +𝐷𝑒 )/2 2
𝑃 = 𝑇 ×𝜔
(21)
Where: u- blade peripheral velocity (m/s), r- The radius of the cross section of the blade (m), 𝒄𝒖𝟏 velocity entrance tangential direction (m/s), 𝒘∞ - velocity entrance relatively average (m /s) , 𝛽∞ average entry angle (degrees), x- distance for between two adjacent blade (pitch) (mm), z Number of blades, L-airfoil cord length (mm), ξa- coefficient of lift, 𝜀 - the angle formed between the force lift (A) with a resultant force on the turbine blades (degrees), δ- angle of attack (angle of attack) (degrees), β- entry angle (degrees), L- chord length (mm), 𝐹𝐿 - lift force (N), FD- drag (drag force) (N), FtTangential force (N), FA- Axial force (N), P-mechanical power turbine 𝑁. 𝑚. 𝑠 −1 or watt The table also shows the equations used for the hydraulic design of the runner. These equations can be obtained with theoretical and empirical methods of analisys of flow. The calculation of the blade system was for blade with a degree of reaction 𝜀 between 0,5-1[2][5]. To define the distortion of the blade, velocity triangle of five different cylindrical sectionsof the blade, located at a proportional distance, are determined (figure 2). The angle b0 of each radius gives conclusion to the distortion of the blade, therefore, between the external and internal diameter an arithmetical ratio can be established obtain the diameters[3][4]. Di, Di+1, Di+2, Di+3, and De or the radius ri, ri+1, ri+2, ri+3, and re respectively. From the design of the profile a type Gottingen-364 was chosen. The selection was made following recommendation from several author such as Pfleiderer, for aplications in turbine and axial pump. The characteristics of the blade were obtained from the institute of Aerodynamic of Gottingen, Germany. Table 3 swhows the characteristics of the profile at different sections, expressed as a percentage of length L. y0 and yu represent of ordinates of the top and bottom of the profile corresponding to the absissca x[6]. Table 3 value in % the length for the profile Gottingen GOE-364 0 1.25 2.5 5 7.5 10 15 20 30 40 50 60 70 80 90 95 100 x yo 0.85 4.05 5.45 7.3 8.6 9.65 11 11.85 12.5 12.1 11.1 9.5 7.55 5.35 2.9 1.55 0.1 0 0.05 0.35 0.55 0.65 1.05 0.3 1.7 1.85 1.8 1.55 1.25 0.9 0.45 0.2 0.1 yu 0.85 The correlation between table 1, table 2 and the profile characteristic of the blade enable a preliminary design of the RBKP. For the the design it is recommended to use an axial velocity c m