hydraulic microturbines: design, adaptations for teaching of

Modern Environmental Science and Engineering (ISSN 2333-2581) March 2019, Volume 5, No. 3, pp. 215-224 Doi: 10.15341/mese(2333-2581)/03.05.2019/004 Academic Star Publishing Company, 2019 www.academicstar.us

Hydraulic Microturbines: Design, Adaptations for

Teaching of Microgeneration

Teresa Maria Reyna, Belén Irazusta, María Lábaque, Santiago Reyna, and Cesar Riha

Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Argentina

Abstract: When it comes to improving the teaching-learning process at the university level, modern teaching techniques are sought to be implemented. This project seeks to generate awareness among students for environment care and encourage the development of renewable energies, focusing the study on micro hydroelectric plants. In the National University of Córdoba (UNC), four projects have been developed to design micro turbines in order to establish the feasibility of construction and development with local technology. A Michael Banki turbine, another axial turbine a Pelton turbine and finally a Turgo turbine were developed. They were designed by students and teachers of the UNC and built in local laboratories, one in the secondary school Technological Institute Cristo Obrero of Carlos Paz and others were materialized by 3D printers generating a prototype of the turbine suitable to take to classrooms.

Key words: microturbines, teaching, microgeneration

1. Introduction

Currently, the development of renewable energies is

the foreseeable consequence of a look at the energy

issue from the perspective of sustainability. Within this

paradigm, professionals and those responsible for

energy and the environment play a fundamental role in

generating its dissemination and bringing technology

closer to the population.

Modern societies are increasingly inclined towards

the adoption of measures that protect our planet. This is

reflected in national policies that considers, as priority,

a sustainable development that does not compromise

the future’s generations natural resources.

The promotion of renewable energy technologies

offers a double advantage: energy diversification and

the hope of development for many poor and isolated

communities that are not connected to the grids of

transport and electrical distribution. The supply of

energy to isolated communities is conceived as support

Corresponding author: Teresa Maria Reyna, Doctora

Ingeniera Civil; research areas/interests: hydraulic, hydrology, environment. E-mail: [email protected].

for their productive, domestic and commercial

activities. Consequently, it is considered as a strategic

component within a framework for development work

[1].

Knowing the current problems, this project seeks to

generate awareness among students for the

environmental care and encourage the development of

renewable energy. From hydraulics, the improvement

is focused on deepening and consolidating knowledge

about turbomachinery, especially those used in micro

hydroelectric plants.

In this context, four projects have been developed at

the National University of Córdoba to design micro

turbines in order to establish the feasibility of

construction and development with local technology.

A Michael Banki turbine was development during

the years 2010-2012. This turbine was designed and

built in Cordoba workshops in a 1:1 scale. This

machine is currently installed in the Hydraulics

Laboratory of the Faculty of Exact, Physical and

Natural Sciences of the National University of Córdoba.

This project was financed by the Secretariat of Science

Hydraulic Microturbines: Design, Adaptations for Teaching of Microgeneration

216

and Technology of the National University of Córdoba

(SECYT).

During the 2014-2015 period, a second project was

also financed by the SECyT, where the engineering of a

turbine propeller (axial type) was developed. In 2017,

the technical-institute Cristo Obrero from Carlos Paz,

Córdoba, Argentina (Instituto Técnico Cristo Obrero)

was involved in the construction of this turbine to

incorporate the subject into the middle level of

education, which was completed at the beginning of

2018. In addition, an agreement has been signed

between the school and the Faculty of Exact, Physical

and Natural Sciences to continue working together.

During the period 2016-2017, a Turgo turbine was

developed. This turbine was materialized using 3D

printers, generating a prototype suitable for carrying it

to the classroom as a teaching support.

Besides, during the year 2018 a fourth project begun

by developing the enginery of a Pelton turbine. This

project started as a final work of a studet to get her

degree as Civil Engineer. The design was fully

developed and the turbine’s runner was also

materialized using 3D printers.

During the year 2019 the analysis and study for the

development of a Francis turbine will begin, always

with the same premise of simplifying the models which

brings us to a loss of efficiency but makes the

construction and maintenance accessible to isolated

populations.

2. Methodology

The project consisted on the design, modeling and

materialization of small turbines (microturbines) for

later use in the field of education. They would clearly

show how the machines operate.

Firstly, the parameters needed for design of the

turbomachine were defined (machines usable in the

Province of Córdoba, Argentina), then the calculation

memory was developed and the turbines were drawn in

the SolidWorks program.

Finally, they were materialized either being

manufactured in the Instituto Técnico Cristo Obrero

secondary school, in local workshop or in a 3D printer.

With the machines and different animations, this

project is transferred to the classrooms to better

visualize the operation of the turbomachinery.

3. Developing

The theoretical analysis of the turbomachines is

carried out assuming negligible the effect of friction

load loss and considering an incompressible fluid.

Then, the velocity of the fluid is decomposed so that

the velocity Ui is the absolute velocity of the blade at

the inlet or outlet, , the absolute velocity of the fluid,

, the relative velocity of the fluid regarding the blade,

, the meridional component of the absolute velocity

of the fluid, , the peripheral (tangential) component

of the absolute velocity of the fluid, , the angle

formed by and and the angle formed by

with − (usually called the blade’s angle). These

three speeds V1, U1 and Vr1 are related by the relative

movement mechanics according to Eq. (1): = − (1)

Given the second form of the Euler Eq. (2) it can be

analyzed each of its term and define which of them are

negligible or not for the different machines. = + + (2)

The dynamic height that the fluid gives to the

impeller is the third term of the previous equation, that

is to say± , while, + is the

pressure or static height of the impeller.

Fig. 1 Triangle of speeds.


217

The term constitutes the static load due to

the centrifugal action or inertial reaction of the fluid

produced by the normal acceleration created by the

drag of the fluid with the blades in their rotation around

the axis of the machine [2].

The turbines can be classified by the degree of

reaction of a turbine. It refers to the way the impeller

works and is the relation between the pressure energy

Hp and the total energy Hu, defined according to the

equation:

height?of?pressure?absorbed?by?the?impeller?GR

total?height?absorbed?by?the?impeller

p

u

H

H (3)

If the degree of reaction is 0, that is Hp = 0, the

machine is called of action or impulse. If GR 0, the

turbine is called of reaction, it has a pressure

component to transfer energy.

Thus, this given classification the Turgo turbines and

the cross flow turbines (Michel-Banki) will have a GR

= 0, while the Francis and Kaplan turbines will have a

GR 0.

According to the estimated characteristics of jump

and flow of the site where the turbine will be placed

and the power that is needed, it is possible to identify

the type of turbine and it’s most suitable size.

Mini-hydraulic systems can be used in all cases

where a power supply is needed and a water course is

available, even if it is small, with a jump of even a few

meters. In these cases, the introduction of water

utilization systems has a reduced impact since there is

no change in the majority use of the watercourse, which

can be vital for the supply of isolated areas. These

systems require few components: turbine group —

generator — and a regulatory system. Also, power

batteries can be used. There is no need of a continuous

presence of a person, however, an operator should

periodically control the correct functioning of

hydraulic (intake) and electromechanical

(turbine-alternator) installations.

In the case of micro-systems, there are different

machines to be adopted according to the conditions of

the emplacement site or to the installations possibilities.

The differences between the machines are linked to the

optimization of the energetic potential of water in order

to generate electric power. Each type of turbine can

only work within flow rates between nominal (for

which the performance is maximum) and the technical

minimum below which it is not stable [3].

The choice of the type of turbine will depend on the

estimated characteristics of the jump and flow of the

area of location and the power that is needed. Fig. 2

shows a diagram that presents the recommended

conditions for the different types of hydraulic turbines

based on these physical characteristics of water courses.

4. Michell Banki Turbine

The Michell-Banki turbine is a machine classified as

an action turbine with radial inlet and transverse flow.

It is used mainly for small hydroelectric uses and its

main advantages are its simple design and its easy

construction, which makes it attractive in the economic

balance of a small-scale use [4].

The main characteristics of this machine are the

following: it operates with wide ranges of flow and

height without varying too much its efficiency, the

diameter does not depend on the flow, it regulates flow

Fig. 2 Range of application for different types of turbines [5].


218

and power with an adjustable vane, its construction is

simple and can be manufactured in small workshops.

This transverse flow turbine is especially suitable for

rivers with small flows, which generally carry very

little water for several months. The water energy is

transferred to the rotor in two stages, which gives this

machine another the name: double effect turbine. The

first stage delivers an average of 70% of the total

energy transferred from the fluid to the turbine, and the

second one around the 30% remaining (Fig. 3). Thus,

the water is restored in the discharge at atmospheric

pressure (degree of reaction equal to zero).

The present turbine was designed with the following

imposed conditions: effective water jump of 25 m, flow

rate 120 l/s, total efficiency of 60%. The useful power

obtained is: 18 kW.

The turbine consists in two main elements: an

injector and a rotor. The rotor is composed of two

parallel discs where the blades are attached. The blades

are curved in the form of a circular arc.

For the construction of the different elements of the

turbine, a series of machine tools were used, such as

folding machines, filing machines, milling machines,

numerical control lathe, etc. The construction of the

rotor and the injector of this machine did not involve

precision casting tasks, as it was already said,

simplifying the turbine (simple design and easy

construction) is an objective of this work. A very

important element for the good operation, and that in

general requires a lot of precision in the construction,

are the rotor blades. In this case to facilitate the

construction of the blades a seamless carbon steel

commercial pipe was used. The pipe was cut forming

an arc with an angle θ. All the pieces that are in direct

contact with the water (injector and rotor assembly)

were subjected to a zinc plating surface treatment to

prolong their useful life. Both the rotor assembly and

the injector were built in steel SAE 1020.

In addition to the construction, plans and a

mathematical model were made using a fluid

computational model (CFD) [6] (Fig. 4a).

Fig. 3 Componentes Principales de la Turbina

Michell-Banki [7].

(a)

(b)

(c) Fig. 4 a) Mathematical Model CFD. b and c) Michael Banki turbine installed in the laboratory.


219

The machine is currently installed in the Hydraulics

Laboratory of the Faculty of Exact, Physical and

Natural Sciences (Fig. 4b and 4c).

5. Axial Microturbine

The axial micro turbine is a machine classified as a

reactive turbine, with axial input and flow. On a large

scale the best axial turbine known is called Kaplan.

This machine is used to design the different parameter

and calculations of the machine, and adaptations are

made for small hydroelectric uses.

The impeller is composed of a few blades, which

gives it the shape of a ship’s propeller; when these

blades are fixed, the turbine is called a propeller,

whereas if they are adjustable, they are called Kaplan

turbines. In both cases, the turbines operate with a

single direction of rotation, therefore, they are

irreversible turbines. In this case, it was opted a turbine

propeller for the development simplifying the design.

Its main characteristics are: reduced dimensions,

relatively high speeds, high performance with variable

load, remarkable capacity for overloads.

For the Kaplan turbine the absolute speed of the

blade U is constant along the vertical axe (not in the

radial direction of the blade, which U changes

according to the radius of each point). Thus, Euler's

equations are as following. = − (4)

= − + − (5)

The machine that was developed seeks to produce at

least one kilowatt. The flow rate considered is 0.1 m3/s

and a net height of 5 m. With these values, considering

an approximate efficiency of 60%, a useful power of

approximately 3 kW is obtained.

In these machines the profile of the blades has

hydrodynamic characteristics with a little curvature.

This facilitates its performance and increases the speed

of the fluid (water), these characteristics make the

diameter of the impeller very small.

As it was said before, the rotor blades have an

aircraft wing profile and helical development. The

wing profile allows the blades to optimize the action of

the water´s impact and movement. The helical shape or

warping is justified because the relative speed of the

flow varies in direction and magnitude with the radius,

assumed ω (angular velocity) constant, and considering

the absolute speed of the blade’s constant in magnitude

and direction. In addition, a polished surface finishing

is required for the blades, since the permitted

roughness between the contact surface and the water

depends on the flow rate.

The manufacture of the blades is the main drawback

to achieve an economic machine, this is because it

requires casting with important precision. If blades of

constant thickness, flat or curved, are used, lower lift

coefficients and greater resistance are obtained. Thus,

overall, efficiency would be lower as the machine

wouldn’t fully exploit the energy of the fluid while

impacting the blades. An example of different

efficiencies obtained is found in the article by Espinoza

(1991) [8], where the axial turbine used without

aerodynamic blades obtains an efficiency value of 40%,

while the axial turbine made by ITDG [9] that has

aerodynamic blades has efficiency of almost 60%.

However, this alternative of blades with constant

thickness was studied, considering the construction of

the blades from a plate with cuts up to a central

diameter and then twisted in helical form. To this end,

work was made with a mathematical model of the

turbine using Solid Works software as a basis for the

development of the different components. Besides, this

program allows to show the animation of the piece and

the simulation of the flow, which helps to understand

the operation of the machine.

In Fig. 5 the hydraulic machine can be observed,

with the simulation of the developed flow. Also, the

absolute speed is decomposed in different directions

needed for the calculation of the different parts of the

turbine. They are also schematized in the figure.

220

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223

Fig. 15 Turbine’s blade.

Fig. 16 Turbine’s injector.

Fig. 17 Design of the rotor in SolidWorks.

Fig. 18 SolidWorks simulation.

Fig. 19 Materialized rotor and blades.

Fig. 20 Rotor of Pelton’s turbine materialized with 3D printers.

8. Conclusions

The main cause of the scarce development of micro

turbines in the Province of Córdoba is the lack of

knowledge and lack of access to the technology and

knowhow of these machines.

The best way to promote the future use of renewable

energies is to make students aware of their importance

and to teach them and make them familiar with their

use, showing them how these machines are an effective

and profitable option. Students must leave the


224

University recognizing the feasibility of applying

renewable energy in their future developments as

engineers and the need of such use, they should

consider them as an option when solving problems of

energy supply.

To accelerate the application of alternative systems

in rural areas, and to make this a normal practice, it is

necessary to develop adequate equipment, adapt them

for progressive production in local industries, and

establish a financing system in collaboration with local

banks to assist to potential users and owners. There is

an unmet demand for robust and reliable equipment

that can supply small amounts of energy at low cost

[10].

The generation of electricity through micro

hydroelectric power stations is today a profitable

option for energy diversification and the development

of communities without access to the interconnected

electricity system. It will only be possible to be

promoted if hydroelectric microturbines are developed

and studied in more depth. The development of

hydraulic machines in the field of Universities has a

direct impact on the promotion of these energies.

Vector diagrams being the biggest difficulty that

students have to learn and understand turbomachines,

with a 3D simulation of these machines and the same

materialized, it is much easier to understand the design

process to improve the efficiency of the machines.

Thus, students will leave the University with the

necessary tools to deepen their study in

turbomachinery and improve the microgeneration

system.

Acknowledgement

Thanks to the Secretariat of Science and Technology

of the National University of Córdoba (SECYT) for

supporting the development of these projects; To the

director of the secondary school Technological

Institute Christ Obrero of Carlos Paz for supporting the

challenge of building hydraulic machines in his school

and to bring renewable energy to the levels of

secondary education.

References

[1] T. Reyna, S. Reyna, M. Lábaque, C. Riha and E. Giménez, Aplicaciones de Usos de Energías Renovables. Microturbinas de Generación Hidroeléctrica, XXV Congreso Latinoamericano de Hidráulica S. J., Costa Rica. 9 al 12 de septiembre de 2012.

[2] M. Polo Encinas, Turbomáquinas Hidráulicas, México, LIMUSA, 1976.

[3] C. Mataix, Turbomáquinas Hidráulicas: Turbinas hidráulicas, bombas, ventiladores (1st ed.), Universidad Pontificia Comillas, 2009.

[4] ITDG, Soluciones Prácticas. Ficha Técnica Nº 2. Turbina Michell Bank, 2004, Consultado noviembre de 2016, available online at: http://www.solucionespracticas.org.pe/ficha-tecnica-n2-turbina-michell-banki.

[5] Celso Penche, Layman’s Handbook on How to Develop A Small Hydro Site (2nd ed.), A handbook prepared under contract for the Commission of the European Communities, Directorate-General for Energy by European Small Hydropower Association (ESHA), 1998.

[6] T. Reyna, C. Góngora, S. Reyna, M. Lábaque, M. García and C. Riha, Turbinas Michell-Banki. Modelaciones Matemáticas De Alabes, XXIV Congreso Nacional del Agua, 2013.

[7] L. S. Paris, J. D. Peláez Restrepo and C. Mira Hernández, Construction and performance evaluation of a Michell-Banki, in: Turbine Prototype: Proceeding of First LACCEI International Symposium on Mega and Micro Sustainable Energy Projects, Cancun, Mexico, August 15, 2013.

[8] J. Espinoza Silva, Desarrollo simplificado de turbina axial tipo “S” para micro aprovechamientos hidráulicos. Informe de Proyecto de FONDECYT-90/0123, 1991, pp. 1-11.

[9] HIDRORED, Red latinoamericana de micro energía, Diseño, construcción y prueba de una turbina de hélice, in: VI Encuentro latinoamericano en pequeños aprovechamientos hidroenergéticos, Lima, 1995.

[10] T. Reyna, S. Reyna, M. Lábaque, C. Riha and F. Groso, Applications of small scale renewable energy, Journal of Business and Economics, 2016.

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