Water Turbine By Using Moving Blade

Manufacturing of low head water turbine by using moving blade that can be used in the irrigation channel (water flow) Prihatin Kahana Physics Teacher at Karangmojo Senior High Gunungkidul Regency Special Region of Yogyakarta E-mail : [email protected]

School

Abstract: The objective of this study is developing the system hydropower plant in irrigation channels. The observational step started by study of hydropower potency, designing of low head water turbine by using moving blade, turbine testing and installation the system power plant. The power available of water can be determined by measurement velocity of water or head and flowrate. Manufacturing of low head water turbine should be considered the power available, in order the turbine running well. Mechanical power generated by turbine is determined by area of blade, velocity of water and speed of turbine. To develop the system of hydro power plant can use the induction motor as generator (IMAG). Since the turbine usually run at low speed and the generator speed is quite high (1500 rpm) it is required the speed increaser. The test results show that the low head water turbine by using moving blade more efficien than a conventional turbine. Keywords : water turbine, hydropower, mechanical power, speed increaser. Reference to this paper should be made as follows : Khurmi, Gupta, 2005. A Taxtbook of Machine Design, Chand (S,) & Co.LTd, India., Lal, J. 1975. Hydraulics Machines. Metropolitan Book Co.Pt.LTd., Delhi., and Maryono, 2005. Ecological Hydraulics of River Development. Biographical notes : Prihatin Kahana has been a physics teacher since 1990 at Senior High School, graduate from Gadjah Mada University Yogyakarta Indonesia, at Mechanical Engineering ( Engineering System – Microhydro Power System )

1. Introduction The reserve of energy in Indonesia decrease, therefore use it efficienly and utilize the renewable energy resources. The potency of renewable energy in Indonesia is very large, one of it is hydropower. Indonesia has many irrigation channels, designing of low head water turbine by using moving blade that can be used in irrigation channels is needed. Designing of low head water turbine should be considered the power available, in order the turbine running well. The power available of water can be determined by measure velocity of water and flowrate. Velocity of water can be measured by directly or indirect method. Directly measurement of velocity can be used current meter, indirect method can be used floater, its mean measuring the velocity of water at the surface flow, and then convert it to average velocity. Mechanical power generated by turbine is ditermined by area of blade, velocity of water and speed of turbine. The mechanical power can be converted to electrical power by generator. To develop the system hydropower plant can be used the induction motor as generator (IMAG). Since the turbine usually run at low speed, and the generator speed is quite high (1500 rpm) it is required the speed increaser.

2. Sizing Power Plant The electrical power generated (Pe) by the system hydropower plant in irrigation channel can be determined by mathematics equation : Pe = 8 QH kW, where Q is discharge (m3/s), and H is the net head (m), assuming an overall efficiency of the electro-mechanical equipment 0,81. (da Vinci, L., 2001). The electrical power generated (Pe) by the system hydropower plant by using low head water turbine that can be used in irrigation channel (water flows) can be written as : Pe= 0,2 A v3 kW, where A is area of blade

(m2) and v is the velocity of water (m/s), assuming overall efficiency 40%. (Kahana, P., 2009).

3. Measurement of velocity Really the velocity of water in irrigation channel at one point to the other point is deferend. The velocity of water at the surface flow can be converted to the average velocity by mathematic equation : vavg = 0.83 vo , where vavg is the average velocity, and vo is the velocity of water at the surface flows. (Maryono, 2005).

4. Manufacturing of low head water turbine Low head water turbine by using moving blades can be installed in irrigation

channel (water flows), the mechanical power generated is

ditermined by area of blade, velocity of water at inlet and speed of the turbine. Measurement of speed (revolution per menute of the saft are measured by one of the following instruments : (i). Revoltion Indicator or Revolution Counter, (ii). Tachometer, (iii). RPS or RPM Counter, (iv). Electrical or Optical Instruments Revolutions are indicated on a dial but there is no indication of time for the measurement of which a stop watch is needed. Tachometer gives speed in rpm while it is being deriven, generally, by means of a belt from the shaft. RPM counter is a combination of (i) ang (ii). 4.1. Dimention Water turbine by using moving blades is difference with the other tourbine, this turbine consist of three type of shaft : central shaft, shaft of blades and detention shaft. Central shaft is biger then detention shaft and the

shaft of blades is smaller than detention shaft. The number of blades is six and the each area of blade is 0,2 m2. The area of blade can be ditermined by electrical power design, speed of turbine design is needed to calculate the diameter of runner and also the velocity of water. 4.1.1. Diameter of turbine, Area of Blade, number of Blades Diameter of turbine runner can be accaunted by mathematic equation, D = 60 u / π N , where u is linear velocity of runner at inlet,

N is speed of the turbine in rpm. Area of blade is given by : A = 4 P / ρ v 3 , assuming efficiency electro-mecanical equipment of 40%, where P is power design, v is velocity of water at inlet. Based on empirical equation, the number of blades can be determined −1

, where l is width of blade and R is by : Z = 360 / sin (l / R ) radius of the turbine runner. (Kahana, P., 2009)

80cm

(a)

(b)

Fig. 4.1. (a). diameter and number of blades (b). area of blade

4.1.2. Designing Shaft and Power Transmition A shaft is rotating machine which is used to transmit power from one place to another. In actual practice, the shaft are subjected to fluctuating torque and banding moment., to design of stationary shaft or rotating shafts must be consider gradually and suddenly applied load. The diameter of shaft can be writen by :

d=

3

16 T / π τ , where T is torque and τ is

shear stress. If the turbine run at low speed requiring a speed increaser to meet 1500 rpm of standard alternator, speed increaser can be chosen belt drive, it’s the simple and cheapest solution.

driver

1

driver

2

3

4

driven x driven Fig. 4.2. Compound belt drive

A compound belt drive as shown in Fig. 4.2. is used when power is transmitted from one saft to another through a number of pulleys. The ratio between the velocitys of the driver and the follower (driven) can be expressed, mathematically as N2 / N1 = d1 / d2, where d1 is diameter of the driver, and d2 is the diameter of the follower (driven). 4.2. Bearings A Bearing is a machine element which support another moving machine element. Bearing can be devided two type, sliding contact bearing and rolling contact bearing. The avantages of rolling contact bearings over sliding contact bearings are : 1. low starting and running friction exept at very high speed, 2. accuracy of shaft alignment, 3. low cost of maintenance, as no lubrication is required while in service. Disadventages of rolling contact bearing over sliding contact bearings are : 1. more noise at very high speed, 2. more initial cost, 3. Design of bearing housing complicated.

5. Generator