Highly Efficient Cross flow Turbine Runner Design for Upgrading Traditional Water Mill in to Micro Hydro Power Plant (A case Study for Kersa-Minko Village)

Highly Efficient Cross flow Turbine Runner Design for Upgrading Traditional Water Mill in to Micro Hydro Power Plant (A case Study for Kersa-Minko Village)

(A case Study for Kersa-Minko Village)

Nebiyu Bogale Mereke School of Mechanical Engineering Jimma Institute Of Technology, JiT

Jimma, Ethiopia

AbstractCross flow turbines, which are suitable in upgrading traditional water mills in to hydro power generating systems in Ethiopia and in general in developing nations creates high interest, due to their simplicity for manufacturing in simple local metal workshops, suitable operating condition for large load variation conditions, the ease of operation and maintenance by low skill remote rural farmers in areas which are detached from the main grid line and apart from most hydraulic turbines their suitability for low head and flow rate conditions . Therefore, in this paper the design of highly efficient cross flow turbine runner for upgrading traditional water mill in to micro hydro power plant and water mill in Kersa-Minko village is conducted. The design includes calculations that determine runner diameter, runner length, runner speed, turbine power, water jet thickness, blade spacing, number of blades, radius of blade curvature, attack angle and the blade inlet and exit angles.

KeywordsCross flow; turbine; runner; flow rate, head, blades.

1. INTRODUCTION

   Ethiopia with a population of 92 million in 2012, with 85% of the people in the nation are living in remote rural villages with their income mainly from agriculture.[2] the settlers in this villages live in a scattered manner for the sake of managing their land. Ethiopian people consider electric power as a luxury enjoyed by a few people in urban areas, which results in migration to the urban areas and abroad to different Arab and western nations for the sake of better life, this days such problems are creating savior problems for the government and people of the nation. therefore creating awareness through technological developments and providing ways for better living standards is the main mechanism in minimizing the problems and developing the nation.[6,7]

   In Ethiopia in 2012 about 2100Mw electricity generated mainly from hydropower and the GTP-1 plan states the country should have 8000 Mw at the end of the five year GTP-1 in 2015. Apart from the large hydro power plants available in the country the highland topography of the country which is suitable for small, micro and Pico hidro power plants, for having sufficient head or elevation for generating power from water by using the large number of annual flowing rivers which are available in almost all rural villages of the country, despite the fact that transmission of power to this rural remote villages from the main grid with difficult topography creates an interest to develop small, Pico, micro and ultra low head hydro power

   projects which can be managed in decentralized manner with their estimated potential of 1500- 3000Mw[6,7]

   In addition, the indigenous knowledge of grain milling using the power of water from small annual flowing rivers, creates interest to undergo further technological development by higher institutions like Jimma University and different governmental and nongovernmental organizations like Alphasol Modular Energy, Agricultural Mechanization Research Institute, GIZ-ECO etc. by using the power from in Ethiopia remote rural villages.[7]

   Only in Jimma Zone which is situated in the south western part of the nation there are more than 60 traditional water mills which can be easily upgraded in to micro hydro power generating system by performing minor adjustment in the existing head race canal and diversion wear, and by installing locally made efficient electro mechanical system, in this respect the efficiency and suitability for technology transfer of the turbine plays an important role in disseminating the technology to the rest remote villagers of the nation.

   This days, the cross-flow hydraulic turbine is gaining popularity in low head and small water flow rate establishments, due to its simple structure and ease of manufacturing in local metal work shops. the standard and latest cross flow turbine known T-15 is manufactured by lather process do have efficiency of conversion from kinetic energy of water in to mechanical energy accounts 80% which is the best turbine, but this manufacturing process is not economical in developing nations. In Ethiopia the maximum efficiency gained from cross flow turbine is about 70% which is highly recommended in the context of the nation.

   The cross-flow turbine is composed of two major parts, the runner and the nozzle . the runner was a circular rotor with two side walls to which the blades are fixed along the periphery of the turbine. The cross-section of the blades was circular with specific radius of curvature. The nozzle directs the water flow into the runner at a certain attack angle and a single water jet penetrates the turbine blade twice, this is a similar process like that of two turbines work for an output, such feature provides larger efficiency.

   The traditional water mill is situated on Kersa-Minko River, Toli Kersu village, Kersa Province, Jimma Zone of the Oromia Regional State of Ethiopia at about 321-km south west of the

   capital, Addis Ababa on the route Addis Ababa- Jimma. The approximate geographical co-ordinates of the area is 70 44.44

   N, 370 00.14 E. at an altitude of 1740 to 2660 meters above sea level.

   H

   Fig. 1. Cross Flow Turbine Runner with Housing

   In this work the design steps of cross flow runner for Kersa-Minko river flow considering the dry season water flow,

   gross

   : Gross Head(m), the elevation difference from the head race canal to the turbine exit.

   and diversion water flow less than 30% of the main river flow in order not to affect the main stream environmental conditions.

   Fig. 2. Cross flow turbine runner

   The design includes calculations that determine runner diameter, runner length, runner speed, turbine power, water jet thickness, blade spacing, number of blades, radius of blade

   The gross head is the elevation difference from the head race

   canal to the turbine exit for kersa-minko is measured using sight surface leveling and found to be (11.8meter)

   Hlosses : Head loss(m), This includes the different losses of

   water flowing from the forbay tank until it penetrates the turbine runner, which includes, trash rack loss, entrance loss, fanning friction loss in the penstock, joint and bending losses, valve losses, and summing up all this results, or considering 6-10% of the gross head. (1.3m)

   Therefore, for kersa-minko flow the net head considered is

   H net =10.5m. Flow Rate

   Kersa-Minko river water flow which is found in the Giba basin

   have annual flow duration, shown in the figure. In this work the flow less than 30% of the main stream in kersa-minko river is considered in the dry season for the sake of environmental effects on the main stream flow. Therefore,

   the flow in the head race canal considered is

   curvature, attack angle and the blade and exit angles. Further recommendations for maximum output while installing the plant is also provided.

   Q 0.2 m3

   Efficiency

   Sec.

2. DATA COLLECTION AND ANALYSIS

   The most important data in the design of hydro power plant is the head and the flow rate,

   Head

   the maximum efficiency of cross flow turbine mainly depends on the angle (angle of attack) between the particle velocity and the tangent directio at the impeller inlet, but according to different researches the maximum efficiency is obtained when the angle of attack 220 , the blade roughness coefficient

   Where:

   Hnet H gross Hlosses

   (1)

   ( =0.98), and Nozzle roughness coefficient (C=0.98)

   The thickness of jet entrance, measured at right angles to the tangential velocity of runner is given as

   te K Do

   Where K=0.087

   te =0.014m Blade spacing tb

   The tangential blade spacing,

   tan1 2 tan

   1

   1

   where, : Blade inlet angle

   390

   (7)

   (8)

   Fig. 3. Flow duration curve at Gilgel Gibe river flow

   The tangential spacing tb is given as,

   t te =0.02225m (9)

   1

   b sin

   Radial rim width (a):

   It is the difference between the outer radius ro and inner radius ri of the turbine runner, and it is also equal to the blade

   spacing and can be given as:

   K

   1

   a sin

   Do =0.02225m (10)

   Number runner blade (n)

   The number of the runner blades can be determined as,

   Fig. 4. Flow duration curve at kersa-Minko river flow

   n Do =22.65 23 blades (11)

   1 C 2 1 cos 2 [3] (2)

   2

   tb

   j

   Water jet thickness t

   , and runner length

   L

   the maximum efficiency becomes =81%, but due to

   It is also defined as nozzle width and can be calculated as,

   manufacturing problems, the efficiency considered in this work is 65%.

   Turbine power out put

   L Q NT

   50H net

   =0.308m (12)

   and the water jet thickness is given by,

   Pt g Hnet Q 13.4Kwt

   (3)

   t 11.7

   H net

   =0.047m (13)

   Speed of the Turbine NT

   j NT

   Distance between water jet and the center of runner shaft y1

   the specific speed correlation with the net head is given by

   N

   513.25

   H

   s 0.505

   net

   156.5

   (4)

   the radius of the runner is the sum of , the water jet thickness, the radial rim width, the distance between water jet and the center of runner shaft, and the distance between water jet and

   513.25 H 5 4

   the inner periphery of runner.

   N net 808 rpm (5)

   T P

   ro y1 t j y2 a

   (14)

   t

   Turbine runner outer diameter

   Do

   And,

   y1 0.116 Do =0.0186m

   D 40

   H net

   =0.1604m (6)

   Distance between water jet and the inner periphery of runner

   o NT

   Jet Thickness te

   y2

   y2 0.05 Do =0.00802m

   The exit blade angle, 2 considered is 90o for perfect radial flow, and is equal to 1 for maximum efficiency,

   N s Specific Speed

   Do Outer diameter of Runner

   Di Inner diameter of Runner

   te Water Jet Entrance Thickness

   tb Blade Spacing

   t j Water Jet Thickness

   B1 Blade Inlet Angle

   B2 Blade Exit Angle

   a Radial Rim Width

   n Number of Blades

   L Length of Runner

   Fig. 5. Blade Geometry

   The radius of blade rc is calculated as,

   1. ACKNOWLEDGMENT

      My acknowledgment goes to Jimma University/Jimma Institute of Technology Research office for supporting this work in terms of finance, and i also would like to thank Dr.Berhanu Belay, Dr.-Ing Towfik Jemal, and Mr. Efrem Wakjira, who kept me highly motivated to undertake every activity of the research project.

      D D

      2

      c 4 D 1

      r o 1 i cos

      o

      1 =0.072m [4] (15)

      REFERENCE

      1. R.K. Saket, Design aspects and probabilistic approach for generation reliability evaluation of MWW based micro-hydro power plant., Indian Institute of Technology (Banaras Hindu

         The central angle

         of the blade angle which depends

         University), Department of Electrical Engineering, Varanasi, Uttar Pradesh 221005, India, 21 September 2013

         basically on the inlet blade angle, is given by,

         2 tan1 1 310

         (16)

      2. Nebiyu Bogale1, Nigussie Mulugeta2,Feasibility Study on the Solar

         PV-B20 hybrid Powered Water Pumping System (A case study in Robit Village), International Journal of Engineering and Technical

         tan1

         1. CONCLUSION

            The complete design of cross flow turbine runner parts considering the maximum efficiency depending on the local manufacturing facilities is performed. The complete runner components, including runner outer and inner diameter, runner length, runner speed, turbine power, water jet thickness, blade spacing, number of blades, radius of blade curvature, attack angle and the blade inlet and exit angles for the case of Kersa- Monqo river is calculated. the design of the other components like penstock, forbay etc., which is not incorporated in this work also determines the safe and optimum operating conditions of the turbine runner and in general, the hydro power plant.

         2. NOMINICLATURE

Angle of attack

Blade Roughness Coefficient

C Nozzle Roughness Coefficient

Efficiency of Turbine

Density of Water

g Acceleration due to gravity

Research, Volume 3, ISSUE 10, October 2015.

1. Bilal Abdullah Nasir, Design of High Efficiency Cross-Flow Turbine for Hydro-Power Plant, International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 8958, Volume-2, Issue-3, February 2013 308

2. Vincenzo Sammartano 1,, Costanza Aricò 1, Armando Carravetta 2, Oreste Fecarotta 2 and Tullio Tucciarelli1 Banki-Michell Optimal Design by Computational Fluid Dynamics Testing and Hydrodynamic Analysis, Energies 2013, 6, 2362-2385; doi:10.3390/en6052362 ISSN 1996-1073,29 April 2013

3. Muhammad Adil Khan, International Islamic University, Islamabad, Pakistan 821 Muhammad Adil Khan and Saeed Badshah International Islamic University, Islamabad, Pakistan Design and Analysis of Cross Flow Turbine for Micro Hydro Power Application using Sewerage Water, May 19, 2014 Published:

4. World Small Hydropower Development Report 2013 www.smallhydroworld.org ETHIOPIA, Published in 2013 by United Nations Industrial Development Organization (UNIDO) and International Center on Small Hydro Power (ICSHP).

5. Melessaw Shanko, Ethiopias Small Hydro Energy Market Target Market Analysis, December 2009

www.renewables-made-in-germany.com

NT Runner Speed