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Efficient Cross Flow Turbine Report
1. Project Completion Report
on
R&D PROJECT
Development of Efficient Cross Flow Turbine for
Hilly Region
Name and Address of PI
Prof. R.P. Saini,
Professor,
Department of Hydro and Renewable Energy (HRED)
(Formerly Alternate Hydro Energy Centre)
Indian Institute of Technology Roorkee
Roorkee -247667, Uttarakhand
Grantee Institutions/organization
Indian Institute of Technology Roorkee
Roorkee (Uttarakhand)
Submitted to:
Ministry of New and Renewable Energy (MNRE)
Govt. of India, New Delhi
Prepared By:
Department of Hydro and Renewable Energy (HRED)
(Formerly Alternate Hydrology Energy Centre)
Indian Institute of Technology Roorkee
Roorkee – 247 667 (Uttarakhand)
May 2019
2. i
1. Title of the Project: Development of Efficient Cross Flow Turbine for Hilly
Region
2. Principal Investigator(s) and Co-Investigator(s)
Principal Investigator
Prof. R.P. Saini
Professor
Department of Hydro and Renewable Energy (HRED)
(Formerly Alternate Hydro Energy Centre)
Indian Institute of Technology Roorkee
Roorkee -247667, Uttarakhand, India
Phone : 01332-285841, Fax : 01332-273517, 273560
E-mail : rajsafah@iitr.ac.in, saini.rajeshwer@gmail.com
Co-Investigator
Prof. S.K. Singal
Department of Hydro and Renewable Energy (HRED)
(Formerly Alternate Hydro Energy Centre)
Indian Institute of Technology Roorkee
Roorkee -247667, Uttarakhand, India
Phone : 01332-285167, Fax : 01332-273517, 273560
E-mail : sunilfah@iitr.ac.in, sunilksingal@gmail.com
3. Implementing Institution(s) and other collaborating Institution(s)
Department of Hydro and Renewable Energy (HRED)
(Formerly Alternate Hydro Energy Centre)
Indian Institute of Technology Roorkee
Roorkee -247667, Uttarakhand
4. Date of commencement of Project
18 March, 2014
5. Approved date of completion
March 17, 2017 extended upto June 30, 2018
6. Actual date of completion
June 30, 2018
7. Objectives of the Project
i) Broad Objectives
In hilly region micro hydro plant capacity up to 100 kW have momentous role in
utilization of mechanical power and electricity generation. The capacity of micro
3. ii
hydro power plant up to 5.0 kW is considered under development of water mill
program by Ministry of New and Renewable Energy (MNRE), Govt. of India. The
popularity of the turbines under micro hydro lies in the fact that they are less costly
and can be fabricated locally. There are various types of turbines that can be used in
micro hydro. Among them, cross-Flow turbine has been considered techno-
economically viable for such sites.
Cross flow turbine runner can be fabricated locally, but has the poor efficiency. Also
this type of runner may be work for low discharge low & high head conditions, which
is a common case in the hills. A cross flow type runner has a drum shape consisting of
two parallel discs connected together by a series of curved vanes or blades. The water
from the nozzles strikes the blades and convert 2/3rd
part of the potential into the
mechanical power. Water comes out from blades at first stage then strikes
diametrically opposite blades and transfers its remaining 1/3rd
energy at second stage.
Water flows from stage I to stage II and remains unguided inside the runner and this
may be the main cause of its low efficiency.
It is aimed to develop standard designs of improved cross flow turbines. The cross
flow runner shall be modified in order to improve the efficiency of the turbine. It is
proposed to provide a flow control mechanism inside the runner. Flow analysis shall
be done using CFD. It is expected that about 5% increment in the efficiency of the
turbine can be achieved. CFD results shall be validated with the laboratory test and a
prototype is proposed to be fabricated and installed at a suitable site for its field
performance monitoring.
ii) Specific Objectives
It is proposed to develop a prototype of improved cross flow turbine. The design of
the improved turbine is proposed to analyze through CFD in order to determine blade
profile and design guide mechanism under different operating conditions of turbine.
Following are the specific objectives;
(a) To carry out CFD based design of runner with guide mechanism of cross flow
turbine.
(b) To design and fabricate the runner along with guide mechanism and other
components of a turbine for a capacity of 5.0 kW.
(c) To test the turbine performance in laboratory for design validation.
(d) To install the modified turbine at a selected site for field test and performance
monitoring.
8. Output of the Project
a) Details of proposed Scientific output:
i) Technical Documents : Completion report of the project
ii) Research Papers : Research component of the project output is
proposed to be published.
iii) Awareness Camps: During development of turbines, two awareness Camps.
4. iii
b) Product/ process quantifiable performance output proposed:
A prototype of 5.0 kW capacity with upto 5% more efficient cross- turbine is
proposed to be developed.
9. Summary of the Project work
In micro-hydro potential sites, cross flow hydro turbine is the suitable alternative to provide
the energy due to its low initial cost, easy construction, installation and maintenance.
However, cross flow turbine suffers the problem of low performance as compared to
conventional hydro turbines. Under the present study, an attempt has been made to enhance
the cross flow turbine efficiency by improving the flow conditions/direction inside the turbine
runner. A guide mechanism having different types of airfoils (Symmetrical and
unsymmetrical) has been investigated and the performance in term of efficiency of the
modified turbine is compared with the conventional cross flow turbine design. In order to
investigate the turbine performance at different operating conditions, numerical simulation
(CFD) using commercially available software (ANSYS) was used. Further, the numerical
results have been validated with the experimentation carried out in the Hydraulic
Measurement Laboratory, Department of Hydro and Renewable Energy, Indian Institute of
Technology Roorkee, India.
Based on the numerical simulations, it is found that the guide tube/vane improves the flow
characteristics inside the runner and hence the efficiency. The placement angle of the guide
vanes affects the flow behavior which in turn flow condition over guide vane. It is, therefore,
the placement angle for both symmetrical and unsymmetrical vane was required to be
optimized and it is found that the cross flow turbine provides better performance with
symmetrical and unsymmetrical guide vane having placement angle of 55º and 45º
respectively. The positioning of the guide vanes has also been optimized by placing the guide
vanes at left, center and right positions and it has been observed from the numerical
simulations that the ‘right’ position of the guide vane yields better performance
corresponding to given operating conditions.
Further, in order to attain the optimum placement angle and placement position for both
symmetrical and un-symmetrical vanes, it was desired to select the suitable airfoil from the
two. Therefore, both airfoils have been simulated under similar operating conditions and it
has been found that the cross flow turbine at 125% of design discharge and with
unsymmetrical guide vane yields the maximum efficiency 76.61% which is about 5.84%
higher than the conventional design cross flow turbine without guide vane and 4.50% higher
than the turbine with symmetrical guide vane. The numerical results of the cross flow turbine
have been validated by rigorous experimental testing in laboratory. Therefore, a cross flow
turbine model was fabricated and tested under different operating conditions. Based on the
experimental investigations it was found that numerical results are on similar lines and a
maximum of 4.57% deviation in results was observed which may be due to instrumental or
measurement error.
Further, in order to test the prototype of modified cross flow turbine a pico hydro power site
was identified at Balkhila River in Chamoli District near Mandal village. The turbine is
deployed. Further, the modified turbine was tested at site and it has been found that the
turbine yields its maximum performance as 71.28% corresponding to 0.151 m3
/s discharge.
5. iv
10. Detailed progress report giving relevant information on work carried out,
experimental work, detailed analysis of results indicating contributions made
towards increasing the state of knowledge in the subject:
Attached with at Annexure-I.
11. S&T benefits accrued
i) Patents taken, if any : NIL
ii) List of Research publications :
Sl.
No
Authors Title of
paper*
Name of the
Journal
Volume Pages Year
i) Saini R.P. and Singal S.K., “Development of cross flow turbine for pico hydro”,
International Conference on Hydropower for Sustainable Development, Feb.05-
07, 2015, Dehradun.
ii) Saini R.P. and Singal S.K, “CFD simulation of cross flow turbine using
AcuSolve”, Altair Technology Conference, 2015.
iii) Saini R.P. and Singal S.K, Saini Gaurav, “Numerical and Experimental
Investigations for Flow Characteristics and Performance Improvement of Cross
Flow Turbine” Journal of Renewable and Sustainable Energy [Submitted on Feb.
03, 2019].
ii) List of Technical Documents prepared : Final report attached.
iii) Manpower trained under the project
(a) Research Scientists/ Research Associates : 03
(b) No. of M. Tech. Dissertation produced : 02 nos.
iv) Awareness, training camps, etc. organized: 02
12. Details of work which could not be completed (if any)
N.A.
13. Suggestions on further work on the subject of research
Further scope of research on the subject is to analyse the combined effect of guide
tube and draft tube on the performance of cross flow turbine. For this, separate
research project proposal may be submitted in due course.
6. v
14. Project Expenditure
The utilization certificate and statement of expenditure has been submitted separately. The
summary details are as follows:
No Financial Position/
Budget Head
Amount
Sanctioned
(Rs. in lacs)
Actual
Expenditure
(Rs. in lacs)
Committed
Liabilities
(Rs. in lacs)
1. Travel 1.60 2.93
1.37
2. Manpower 14.40 10.83
3. Equipment 6.00 4.78
4. Consumables 6.00 5.90
5. Contingencies 2.88 3.51
6. Others, if any --- ---
7. Overhead Expenses 7.36 5.99
Total 38.24 33.94 1.37
Total Expenditure (Rs. in lacs) : 33.94 + 1.37 = 35.31
15. Equipment Status
Sl.
No
Name of
Equipment
Year of
Purchase/
installed
Make/
Model
Cost
(FE/
Rs in
lakhs)
Date of
Installation
Utilization
Rate (%)
Remarks
regarding
Maintenance/
Breakdown
1 CFD software 23.06.2014 -Altair Hyperworks
Acusolve Software (25
HWU)
2.396 27.10.2015
100% NIL
2 Desktop 30.09.2014 - Model: 3020 MT Mini
Tower Business Model
- Make : DELL
0.50 01.10.2014
3 UPS 30.09.2014 - 1 KVA
- Make: Numeric
-Model: 1000AX
0.06 01.10.2014
4 Imported
Reflective
Chargeable
Film
18.09.2014
---
0.04 ---
5 4 GB DDR-3
1600 MHZ
RAM for
DELL PC
22.12.2014
---
0.05 ---
6 Turbine
Components
Fabricated items time to time 2.257 ---
7 Dell 24” LED
TFT Monitor
05.08.2015 S.No.CN-0MZJRH 0.16 05.08.2015
8 Plutek Mobile 15.09.2015 5420 0.13 15.09.2015
9 18.5 LCD
Monitor
18.06.2016 S.No.511INAR2C536 0.06 18.06.2018
10 DOL Motor
Starter
20.04.2017 - 45 HP
- 415 V
- Make: LOT
0.18 20.04.2017
11 Alternator &
Pulley
13.05.2017 - 7.5 kVA
- Make: Kirloskar
- Single phase, Brushless
type Pulley dia-18”,
Section B, Groove:
Double 22.04.2017
0.42 13.05.2017
7. 16. Manpower
Sl. No. Sanctioned List In position at the time of
proiect completion (Yes/ No)
Pay Scale/
Emoluments
1 ProjecVResearch
Associate (01 No.)
No Rs.20,000-40,000/-
(fixed)
z. Project Attendant
(01 No.)
Yes Rs.8,000 - 20,000/-
(fixed)
h*
Principal Investigator
(S.K. Singal)
Head. HRED
vi
8. ANNEXURE - I
Final Report
on
R&D Project
Development of Efficient Cross Flow Turbine for
Hilly Region
9. 2
EXECUTIVE SUMMARY
In hilly region micro hydro up to 100 kW have momentous role in utilization of mechanical
power and electricity generation. The capacity of micro hydro power plant up to 5.0 kW is
considered under development of water mill program by Ministry of New and Renewable
Energy (MNRE), Govt. of India. The popularity of the turbines under micro hydro lies in the
fact that they are less costly and can be fabricated locally. There are various types of turbines
that can be used in micro hydro. The cross flow turbine recommended for micro hydro range
is generally considered a simple turbine in construction, installation, operation and
maintenance. It is suitable for low, medium and even high head also. However its efficiency
is inferior in comparison of other conventional turbines. As cross flow type runner has a drum
shape consisting of two parallel discs connected together by a series of curved vanes or
blades. The water from the nozzles strikes the blades and convert 2/3rd
part of the potential
into the mechanical power. Water comes out from blades at first stage then strikes
diametrically opposite blades and transfers its remaining 1/3rd
energy at second stage. Water
flows from stage I to stage II and remains unguided inside the runner and this may be the
main cause of its low efficiency.
Various studies have been carried out to improve and analyze the efficiency of cross flow
turbine. Some experimental studies have been carried out to analyze the turbine efficiency by
varying the number of blades, the runner diameter, and the nozzle entry arc under different
flow and head conditions. Other geometric parameters such as angle of water entry, diameter
ratio, number of blades, flow stream spreading, runner aspect ratio, and blade exit angle are
also investigated for better efficiency of turbine. Some experimental studies were also carried
out to investigate the effect of draft tube size on the performance of a cross-flow turbine.
There is a scope to develop an improved cross flow turbine design by providing a guide
mechanism and draft tube. Few concept studies were carried out to investigate the effect of
interior guide tubes in cross flow turbine runner on turbine performance. However, flow
conditions inside the turbine runner were not extensively investigated so far.
It is therefore, there is a need to investigate the flow passage inside the turbine with respect to
guide tube area in order to develop an efficient cost effective cross flow turbine design.
Keeping this in view a R&D project entitled “Development of Efficient Cross Flow Turbine
for Hilly Region” was sanctioned by Ministry of New and Renewable Energy (MNRE), New
Delhi with the following objectives:
i. To carry out CFD based design of runner with guide mechanism of cross flow
turbine and a draft tube.
ii. To design and fabricate the runner along with guide mechanism and other
components of a turbine for a capacity of 5.0 kW.
iii. To test the turbine performance in laboratory for design validation.
iv. To install the modified turbine at a selected site for field testing.
10. 3
This project completion report contains the details of the work carried out under the project.
The improvement has been analysed through CFD and based on CFD analysis the turbine
parameters were determined for different operating conditions. Finally using the determined
parameters a small capacity of about 5 kW cross flow turbine was fabricated, tested in
laboratory for performance validation and then the prototype was installed at a selected site
(Village-Mandal near Gopeshwer in District Chamoli, (Uttarakhand) for testing turbine in
field.
11. 4
Chapter-1
SELECTION OF DESIGN PARAMETERS
1.1 GENERAL
In Cross flow turbine energy transformation take place over turbine runner blades in two
stages. Water enters to runner blades through the nozzle at first stage and after crossing the
open space inside the runner water strikes the blades again at second stage and then discharge
through outlet. The water crosses the shaft before leaving the turbine hence the name is given
as ‘cross flow’. Fig.1.1 depicts the schematic of water flow over the turbine runner.
Fig.1.1: Schematic of cross flow turbine showing the flow over the runner blades [1]
1.2 COMPONENTS OF CROSS FLOW TURBINE
In cross flow turbine runner and nozzle are the main parts. The nozzle guides and controls
the water flow into the runner and converts the potential energy into kinetic energy in the
form of high velocity jet. Nozzle is rectangle in cross section. The two surfaces are plane and
other two surfaces are typically curved. The selection of optimum number of blades is an1
important consideration for runner design for CFT. Less as well as more number of blades
may increase the hydraulic losses and hence reduce the efficiency of CFT. The runner blades
can be cut from a standard sheet metal or steel pipe and then be bent into the required blade
profile. In some cases, to improve the structural integrity of the runner, more than two
equally spaced discs are employed. The main components of Cross Flow turbine are as
shown in Fig.1.2.
Fig. 1.2: Components of Cross Flow turbine [1]
1
(Source: C.S. Kaunda etc., A numerical investigation of flow profile and performance of a low cost Crossflow turbine, International
Journal of Energy and Environment 5 (3) (2014).
12. 5
1.3 DESIGN PARAMETERS
There are numbers of design parameters that affect the turbine performance such as outer
diameter of runner (D1), angle of attack (ɑ), optimum number of blades, nozzle profile, blade
profile, etc. Values of all these parameters for an optimum design are computed as follows.
Keeping in view the constraints of computing facility and available testing facilities of
laboratory, design parameters of proposed Cross Flow turbine are considered. The range of
system and operating parameters considered are discussed under this section of the report.
1.3.1 Working and System Parameters
(i) Power Output, Po = 5 kW
(ii) Design Head, H = 4-8 m
(iii) Turbine Efficiency, η = 70% (without modification)
(iv) Turbine speed, N = 300 rpm
Based on the working parameters given above, other design parameters are determined using
standard formulae as given below:
(i) Power Input, Pi =
η
(1)
(ii) Design Discharge, Q = (2)
(iii) Jet Velocity, vjet = (3)
(iv) Runner Velocity, u = ku.vjet (4)
(v) Runner Outer Diameter, D1 = (5)
(vi) Runner width, b = (6)
Using above expressions and value of working parameters the turbine parameters are worked
out and given as follows:
1.3.1.1 Turbine runner
(i) Outer Diameter of runner (D1) : 300 mm
(ii) Diameter ratio (D2/D1) : 0.67 (Standard value for CFT)
(iii) Inner Diameter of runner (D2) : 0.67×300 (= 200) mm
(iv) Runner Width (b) : 300 mm
1.3.1.2 Runner blades
Standard values of blade inlet angle, blade outlet angle and number of blades are considered
for the design of blades of the turbine.
The method of designing the blade profile is depicted (Fig.1.3)
i. Draw Outer diameter circle (D1) and inner diameter circle (D2) from centre point O.
13. 6
ii. Draw a line OB from runner centre O that make angle of 120° with vertical centre line
OC which cuts the inner diameter circle at point A.
iii. Draw a line joining point A and point C, which cuts the inner circle at point E.
iv. Draw a line through C that makes an angle of 30° with the line OC and cuts the
perpendicular bisector of CE at point D.
v. Taking D as the centre, draw an arc joining point C and point E. This arc represents
the inner surface of the blade profile.
vi. Another arc with a radius 4 mm greater than the inner radius is drawn between the
two concentric circles to obtain the outer surface of the blade profile.
Fig.1.3: Blade Profile
Using the aforementioned method, the value of blade radii for the cross flow turbine runner
are found as:
Blade inner radius (rb) : 48 mm
Blade outer radius : 48 + 4 = 52 mm
The values of blade parameters summarized and are given in Table-1.1.
Table-1.1: Blade parameters
S. No. Parameters Value
1 Blade inlet angle (ɑ) 16o
2 Blade outlet angle (β1) 30o
3 Number of blades 24
4 Blade Thickness 4 mm
120
o
14. 7
1.3.1.3 Nozzle
As per the construction and working of the Cross Flow turbine, Nozzle width (D) is taken
equal to the runner width (b). The different values are given below:
Nozzle width : 300 mm
Nozzle Admission Arc (Arc angle) : 90°
In order to get the nozzle profile radial distance of nozzle profile radius from the centre for
given are angle and an angle φ can be determined by using following expression:
Rφ = R1etan .φ (rad)
(7)
Where, φ (rad) = φ (°)* /180.
The determined values are given in Table 1.2.
Table 1.2: Radius distance of nozzle profile
S. No. φ(°) φ(rad) Rφ
1 0° 0 150
2 30° 0.5236 174.30
3 60° 1.0472 202.54
4 90° 1.5708 235.35
15. 8
Chapter-2
NUMERICAL INVESTIGATION OF CROSS FLOW TURBINE
2.1 GENERAL
Initially numerical investigation was carried out on a conventional cross flow turbine model
and the results obtained are used to analyse the power output and efficiency of the turbine.
The turbine model is then modified and a guiding mechanism (guide tube) is introduced in
the runner to investigate its efficiency. A CFD analysis is then carried out on the modified
design. Finally, a comparison is made between the two cases to study the effect of interior
guide tube on the performance of the turbine.
The flow domain consists of nozzle wall, runner and outflow channel. First of all, a 3D model
of the turbine is created using ANSYS Workbench, using the aforementioned dimensions.
The 3D model is then discretized through mesh module of ANSYS. The discretized 3D
model is simulated to solve the flow problem in ANSYS Fluent solver. Solver of the domain
involve the creating reference frame for rotating flow zones, assigning boundary conditions,
assigning initial conditions applying governing equations with appropriate turbulence model
and choosing the fluid (water) and its phase properties. Finally, the results obtained are
analysed in post-processing tool of ANSYS workbench.
2.2 GEOMETRY CREATION
3D model of the cross flow turbine is generated in the design module of ANSYS with vanes
and without vanes. The computational zone consists of four zones, namely nozzle, rotating
volume, stationary volume and the outflow channel. Nozzle is modelled as a rectangular
cross section duct, which delivers water to the runner and wrapped over 90º part out of total
360º. A gap of 2 mm is introduced between the nozzle and the runner. The profile of the
nozzle is drawn as per the aforementioned nozzle parameters. In order to make the
simulations, 2 domains of the complete model were selected as rotating domain and
stationary domain. The rotating domain consists of rotor blades and form the runner for
turbine. Stationary domain is the open space inside the runner. The outlet section resembles
the draft tube for turbine. In order to apply the boundary conditions the 3D model was named
as inlet section, nozzle, runner, guide tube/vane, runner interior and casing. The material of
the model was kept as “fluid’. Fig.2.1 shows the 3D model of the cross flow turbine, along
with all its components.
16. 9
Fig.2.1: 3D model of cross flow turbine
2.3 MESHING
The non-conformal unstructured grid was generated in the MESH module for all parts of 3D
computational domain. The unstructured grid provides better flexibility for automatic
generation with the designed accuracy level. The fine mesh size has been selected in the
rotating domain as compared to stationary domain. Further, in order to have the meshing
stability or gird independence, mesh of the computational domains was gradually refined at
several stages. The total number of nodes were varied from 2.3 million to 7.1 million and 6.5
million nodes are found to be satisfactory since efficiency achieved an asymptotic value. The
Boundary (inflation) layers at the turbine runner blades and guide vane were formed to
enhance the quality of the boundary layer flow. The quality parameters of the mesh were met
as per the guidelines given by ANSYS Fluent. In order to maintain the boundary layer flow,
‘y+’ value was fixed corresponding to the considered turbulence model (SST k-ω).
Accordingly, the value of the height of first prism layer has been fixed. The mesh at boundary
layers and interfaces were refined in order to make the smoother transition of mesh at
interfaces. General Grid Interface (GGI) method was applied for interfaces connections. The
detailed statistics of Meshing is given in Table 2.1 for the model with and without guide
vane. Further, the computational meshed domain with guide vane is shown in Fig.2.2.
Table 2.1: Details of the generated mesh
Domain With guide vane Without guide vane
Nodes Elements Skewness Nodes Elements Skewness
Nozzle 188046 173512 0.764 271100 254133 0.76
Rotating
Volume
4605799 12514269 0.81 3168243 8294837 0.80
Stationary
Volume
1213687 4108554 0.79 547300 532818 0.54
Outflow
Channel
594270 566996 0.67 914300 878625 0.50
Total 6538035 17363331 0.82 4853643 9960413 0.81
17. 10
Fig.2.2: Meshing of computational domain (stationary and rotating)
2.4 SOLVER SETUP
ANSYS FLUENT has been used as the solver to solve the unsteady incompressible Navier-
stokes equations. In order to solve the complex flow inside the turbine runner a suitable
turbulence model is required to converge the solution of unsteady Reynolds averaged Navier-
stokes equations. Two equations based SST k-ω turbulence model was used for present
numerical analysis. The SST model has shown a reasonable better turbine performance and
solution convergence. Further, it demonstrates the good agreement between CFD and
experiments results.
For the present study, necessary fluid (water) properties were taken from the ANSYS
database. For numerical solution, various cases of cross flow turbine were solved by using the
required boundary conditions and defined at different named selections. The present
numerical analysis involves various boundary conditions as summarized in Table 2.2.
Different mass flow rate have been examined to study the performance of the turbine at rated
load, overload and part load conditions. Atmospheric pressure condition has been provided at
the outlet of the outflow channel. The rotating zone having the turbine blades was provided
with the angular velocity calculated for runner. The “Mesh motion” approach was used for
rotating domain in order to obtain the transient solutions.
Table 2.2: Details of Boundary Conditions
Boundary Name Boundary Type Boundary condition
Inlet Mass Flow Inlet Mass flow rate
Outlet Pressure Outlet Atmospheric pressure
Blades Moving Wall Angular velocity
Nozzle walls and
casing solid walls
Wall No slip condition
18. 11
In order to obtain more accurate results, the CFD investigation was carried out by selecting
SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) pressure velocity coupled
solver along with 2nd
order upwind scheme for all convection terms i.e. equation of
momentum, turbulent kinetic energy, and turbulent dissipation rate. The least squares cell
based algorithm is considered to evaluate all the gradients. The SIMPLE solver was selected
due to complicated problem associated with the flow inside the turbine runner and it
incorporates the under-relaxation factor which is less than one and increase the accuracy of
the results. However, the convergence of the solution takes a high computational cost.
Convergence criteria for all residuals of momentum, continuity, and turbulence equations
were defined as 1×105
for each time step.
For CFD simulations, the results are significantly influenced by the time step size. The
optimum time step size along with maximum number of time step size leads to accurate
results. Under the present analysis, time step size (t=0.011 sec) corresponds to 20º runner
rotation was provided. For each case, the maximum number of time step size was provided
for 5 complete rotation of turbine. The torque of the last revolution was used for turbine
performance. The power output of the turbine is the multiplication of the torque obtained and
the angular velocity of turbine runner. Thus, the rotor required 18 time-steps to complete a
revolution. For a complete case total 90 time steps were applied along with 50 iteration per
time step or up to convergence achieved. Present numerical investigations was carried out
without considering the cavitation effect.
2.5 SIMULATION RESULTS
2.5.1 For Cross Flow Turbine without Guide Vane
2.5.1.1. Flow contours
In order to visualize the flow behaviour across the turbine, the pressure and velocity contours
were plotted. Velocity contour displays the velocity variation inside the computational
domain. The intensity of the velocity at any section can be analysed by the color of the
contour. The red color shows the high velocity fields while the blue color shows the low
velocity field. The magnitude of the velocity at any particular position can be easily
visualized with the help of scale besides each contour. In similar ways, the pressure contour
displays the pressure variation in the computational domain. The high pressure areas are
shown with red color while the low pressure areas are shown with blue color.
Fig.2.3 shows the pressure variation across cross flow turbine under different discharge
conditions having no guide vane. A wake zone (indicated by white circle) was observed in
the open space between the turbine blades when turbine was running with partial and design
operating conditions. The wake zone was found to be disappeared as the turbine was allowed
to operate at overload conditions. Wake region was originating due to recirculation of the
water and improper guidance of the flow. A high pressure zone (indicated by blue circle) was
observed at the nozzle. It can also be observed that the pressure across the first stage blades
are more than the pressure over second stage blades and the magnitudes of total pressure
increases with the increase of discharge.
19. 12
Fig.2.3: Pressure contour (without guide vane) at different discharge conditions
Fig.2.4 indicates the velocity variation across the cross flow turbine having no guide vane
under different discharge condition. The rotor experience a high speed zone (indicated by
dark blue circle) due to formation of jet phenomena inside the open space and a low speed
zone (indicated by white circle) due to flow recirculation under partial load conditions.
However, the turbine starts to operate smoothly as the discharge increases up to design and
overload conditions. It is also observed that water follows the similar flow variations under
different discharge conditions except the magnitude of velocity. The water emerged in jet
form after passing from the second stage of blades.
Fig.2.4: Velocity contour (without guide vane) at different discharge conditions
20. 13
2.5.1.2. Performance analysis
In order to obtain the turbine performance without guide vane the simulation results were
analysed and given in Table 2.3.
Table 2.3: CFD Simulation Results analysis
S.
No
Discharge
(Q/Qmax)
(%)
Boundary conditions Simulation Results
Mass flow
rate at inlet
ṁ (kg/s)
Pressure at
Outlet
po (Pa)
Torque
(Nm)
Inlet
Pressure
pi (Pa)
Outlet
Pressure
po (Pa)
1 50 129 101325 42.77 24428.1 1.82
2 75 193 101325 172.06 40250.1 0.91
3 100 257 101325 370.67 57700.3 0.54
4 125 322 101325 643.58 79496.5 1.15
5 150 386 101325 983.07 101591 0.45
The value obtained from the simulation, as tabulated in Table 2.3, are used to calculate
various performance parameters, such as head developed, input power, output power and
efficiency for the turbine. The values of the various parameters have been calculated, as
summarized in Table 2.4. The curve is plotted and shown in Fig.2.5. It can be observed from
Fig.2.5 that efficiency of a cross flow turbine increases with increase in discharge up to a
certain limit and then attained a constant value for discharge conditions.
Table 2.4: Output calculation for turbine without guide vane
S.
No.
Discharge
(Q/Qmax)
(%)
Head
Developed
H (m)
Power
Input
Pi (kW)
Power
Output
Po (kW)
Efficiency
η (%)
1 50 2.49 3.14 1.34 42.76
2 75 4.10 7.77 4.84 62.24
3 100 5.88 14.85 10.58 71.26
4 125 8.10 25.57 18.44 72.13
5 150 10.36 39.21 28.58 72.89
21. 14
Fig.2.5: Efficiency vs. Discharge
2.5.2 Cross Flow Turbine with Guide Vane
2.5.2.1 Performance analysis
Numerical analysis of the cross flow turbine has been carried out with and without guide
vane and performance of the turbine was accessed in term of efficiency of the turbine. In
order to simulate the turbine with guide vane, two different type of guide vanes (symmetrical
and unsymmetrical) were chosen to guide the water passage inside the runner cavity.
The placement of the guide vane inside the runner cavity is decided by the placement angle,
therefore, the turbine runner were tested at different angles and the results are plotted as
shown in Fig.2.6. The output calculations for symmetrical and unsymmetrical guide vane at
different vane angle are given in Table 2.5 and Table 2.6 respectively. In case of symmetrical
guide vane, the cross flow turbine attains the maximum efficiency at 55º angle, while for un-
symmetrical guide vane, maximum efficiency is found to be at 45º placement angle.
Therefore, 55º and 45º were chosen for symmetrical and un-symmetrical guide vane
respectively. In order to observe the turbine behavior under different operating conditions,
discharge was varied from 50% - 150% of design discharge.
Table 2.5: Angle optimization for symmetrical guide vane
Vane Angle
Simulation Results Calculations
T (Nm) pi (Pa) po (Pa) H(m) Pi (kW) Po(kW) η (%)
50º 354.42 57832.3 0.02 5.9 14.88 11.13 71.23
55º 344.89 54938.7 0.18 5.6 14.14 10.84 72.98
58º 365.32 59216.3 0.74 6.04 15.24 11.48 71.89
0
10
20
30
40
50
60
70
80
45 65 85 105 125 145
Efficiency
(%)
Discharge (Q/Qmax), (%)
22. 15
Table 2.6: Angle optimization for un-symmetrical guide vane
Vane
Angle
Simulation Results Calculations
T (Nm) pi (Pa) po (Pa) H(m) Pi(kW) Po (kW) η (%)
40º 374.43 58331.4 0.04 5.95 15.01 11.29 72.17
45º 375.01 57260.1 0.04 5.84 14.73 11.37 74.26
50º 366.31 56595.0 0.04 5.77 14.56 11.18 73.49
Fig.2.6: Vane angle optimization for symmetrical and un-symmetrical vane
Fig.2.7 shows the efficiency variation under different discharge conditions for symmetrical
and unsymmetrical guide vane. The simulations were performed on cross flow turbine runner
by varying the positions of guide vane inside the runner cavity. Three different positions (left,
right and center) of guide vane were selected for analysis. Under these positions, the
performance of cross flow turbine was compared with the turbine having no guide vane.
Based on the performance curve it can be observed that the turbine with guide vane follows
the similar trend turbine without guide vane. Further, it has also been found that the right
position of guide vane yields maximum performance for all the cases considered. This is due
to the fact that recirculation of water is reduced significantly by placing the guide vane at
right side inside the turbine runner.
70
71
72
73
74
75
39 44 49 54 59
Efficiency
(%)
Vane Angle (º )
Symmetrical vane angle
Un-symmetrical Vane angle
23. 16
Fig.2.7: Performance comparison of cross flow turbine with (a) Symmetrical guide vane
(b) Un-symmetrical guide vane
The flowing water experience the presence of a guide tube to enter in the second stage, which
might be one of the reason for the better performance of the turbine. On the other hand, the
left positioning of guide vane yields the inferior performance under similar operating
conditions. Under the left positioning of guide vane the flowing water experience more wall
shear stress, hence reduction in performance. Similarly, the center position of guide vane
enhance the shearing effect due to viscosity. Based on the analysis, the results of the output of
the turbine under different cases are summarized in Table 2.7 and Table 2.8.
24. 17
Table 2.7: Comparison of turbine efficiency for symmetrical guide vane
Discharge
(Q/Qmax)
(%)
No vane Vane at the Centre Vane at the Left Vane at the Right
Efficiency
(%)
Efficiency
(%)
Variation in
Efficiency
(%)
Efficiency
(%)
Variation in
Efficiency
(%)
Efficiency
(%)
Variation in
Efficiency
(%)
50 42.76 39.57 -3.19 36.42 -6.34 43.95 2.42
75 62.24 59.5 -2.74 62.26 0.02 64.79 4.57
100 71.26 69.47 -1.79 69.75 -1.51 71.98 3.61
125 72.13 69.62 -2.51 70.85 -1.28 73.16 3.09
150 72.89 68.15 -4.74 70.58 -2.31 71.58 0.94
Table 2.8: Comparison of turbine efficiency for un-symmetrical guide vane
Discharge
(Q/Qmax)
(%)
No vane Vane at the Centre Vane at the Left Vane at the Right
Efficiency
(%)
Efficiency
(%)
Variation in
Efficiency
(%)
Efficiency
(%)
Variation in
Efficiency
(%)
Efficiency
(%)
Variation in
Efficiency
(%)
50 42.76 39.17 -3.59 36.42 -6.34 47.99 5.23
75 62.24 59.24 -3.00 62.22 0.02 67.78 5.54
100 71.26 68.87 -2.39 69.75 -1.51 75.99 4.73
125 72.13 69.02 -3.11 70.85 -1.28 76.61 4.48
150 72.89 68.35 -4.54 70.58 -2.31 74.31 1.42
It is clearly seen from Tables 2.7-2.8 that guide vane placement at left and center reduces the
turbine efficiency as compared with turbine having no guide vane. However, the right
position of guide vane enhances the turbine performance by guiding the water inside the open
space between the runner blades. Further, it has also been found that the unsymmetrical guide
vane provide the maximum enhancement as 5.54% at 75% discharge conditions (partial load
conditions). On the other hand, the turbine with symmetrical guide vane achieved a
maximum enhancement of 4.57% at 75% discharge conditions (partial load conditions).
Under full load conditions, the turbine with unsymmetrical guide vane experience a 4.73%
enhancement in the performance which is considered to be substantial increment, while the
symmetrical guide vane aids to improve the turbine performance by 3.61 %.
2.5.2.2 Flow contours
In order to visualize the difference between the flow pattern of the cross flow turbine with
guide vane, Figs.2.8-2.11 were plotted. Fig.2.8 shows the pressure contours across the cross
flow turbine having a symmetric guide vane at different location inside the open space under
constant discharge condition (on design load condition). The pressure difference with guide
vane is more than without guide vane. The wake zone (low pressure) is found to be
diminished due flow attachment at center and right position of guide vane. However, the left
position of guide vane does not interact with the eddies formation due to recirculation of
water. Thus, the wake zone is observed in the open space. Fig.2.9 represents the velocity
variation contours at different positions (center, right and left) of symmetric guide vane under
constant discharge condition. It can be visualized from the contours that center and left
position of guide vane try to retard the motion of water flow due to wall effect. However, in
case of right position, a defined path of water is developed due to presence of guide vane.
Therefore, the right position of guide vane increase the participation of water interaction in
second stage. In second stage, water interact with more number of blades as compared to
runner with guide vane under similar operating conditions.
.
25. 18
Fig.2.8: Pressure contour with 100% discharge and different positions of
symmetrical guide vane
Fig.2.9: Velocity contour with 100% discharge and different positions of
symmetrical guide vane
Fig.2.10 shows the pressure contours of cross flow turbine runner having un-symmetrical
guide vane at different position under constant discharge condition. The pressure difference is
found to be more under un-symmetrical guide vane as compared to symmetrical guide vane
runner. Fig.2.11 shows the velocity variation in turbine runner having un-symmetrical vane
under constant discharge conditions. The velocity contours of turbine having unsymmetrical
guide vane are similar with the symmetrical guide vane but the magnitude of the velocity is
slightly higher in case of un-symmetrical guide vane runner. The right position of guide vane
are found to be worthy as compared to left and center position.
Fig.2.10: Pressure contour with 100% discharge and different positions of
un-symmetrical guide vane
27. 20
Chapter-3
FEBRICATION AND EXPERIMENTAL STUDY OF CROSS FLOW
TURBINE
3.1 GENERAL
Based on the optimal design of the cross flow turbine investigated by numerically, turbine is
designed and fabricated. Further, the performance of the developed turbine is tested in
laboratory.
3.2 FABRICATION OF TURBINE COMPONENTS
The runner based on the design parameters as given below was fabricated.
Diameter of runner = 300 mm
Width of runner = 500 mm
No. of blades = 24
Shaft diameter = 50 mm
Fig.3.1 shows the fabricated components of the turbine of the runner.
29. 22
3.3 EXPERIMENTAL TESTING OF CROSS FLOW TURBINE
3.3.1 Test Setup Experimental Procedure
In order to validate the results obtained through CFD analysis, the turbine has been tested on
an experimental setup at HRED, IIT Roorkee (Figs.3.2-3.4).
Cross Flow Turbine was tested at the rig in laboratory. Two service pumps installed in the
sump tank were used to supply the required flow for the operation of cross flow turbine. A
valve was connected at the turbine inlet to vary the discharge supplying to the cross flow
turbine. A digital pressure gauge was connected to the CFT inlet for measuring the pressure
head. For the discharge measurement Ultrasonic Transit Time Flow meter (UTTF) was used,
which was fitted on the penstock. The CFT was connected to a generator through a belt and
pulley arrangement. The generator was connected to the panel having bulb loads and a
wattmeter for measuring the generator output. Slowly the valve was open and the water was
made to flow through the CFT impeller. When the impeller just started to rotate, readings of
the pressure gauge head, discharge were noted. After that the valve was opened further and
the turbine started to rotate with more speed. Then the load on the generator was given by
switching on the bulbs. The flow and the bulb loads were so adjusted as to maintain 1500
rpm of the generator and 240 volts in the voltmeter. The reading of the pressure gauge (head),
Flow meter (discharge), and wattmeter were noted. After that valve was opened furthermore
and again the procedure was repeated and several readings for varying discharge were taken
for further calculation of efficiency.
Fig.3.2: Test Rig and developed turbine for laboratory testing
30. 23
Fig.3.3: Developed turbine with generator on testing rig.
Fig.3.4: Testing of the Cross Flow Turbine in the Laboratory
3.3.2 EXPERIMENTAL RESULTS
The numerical results were validated with the experimental results under similar
operating conditions. Fig.3.5 shows the comparison in the numerical and experimental
efficiency results versus discharge (m3
/s). Numerical results follow the similar trends with the
experimental results and the difference between the values are due to measurement and
instrument error. Table 3.1 gives the measured data on results of turbine efficiency.
32. 25
Chapter-4
FIELD TESTING OF MODIFIED CROSS FLOW TURBINE
4.1 SITE SELECTION AND SURVEY
In order to test the efficiency of modified Cross Flow turbine in field, a site at Mandal village
in district Chamoli of Uttarakhand State was identified. The topographic details of the site are
given below:
Details of site
Name of the Site : Balkhila River
Village : Upper Mandal Village
District : Chamoli
Head (m) : 6.0
Discharge (lps) : 200
Access : Mandal village is 13 km from Gopeshwar
Fig.4.1 shows the road map of the site.
Fig.4.1: Road Map of the site location
Site Location at Mandal,
Chamoli
33. 26
After identification of the site, a survey of the scheme was conducted. During survey water
availability, head and discharge were measured. Locations for diversion, desilting tank,
forebay tank and power house were located. The location map and layout of the site is shown
in Fig.4.2 and Fig.4.3 respectively.
Fig.4.2: Location map of project site at Balkhila river in Distt, Chamoli
Fig.4.3: Layout of the power house at Balkhila site
Photographs taken during survey are given in Figs.4.4-4.8.
36. 29
Fig.4.8: Location of forebay
4.2 CONSTRUCTION OF CIVIL WORKS AND INSTALLATION OF
EQUIPMENT
4.2.1 Diversion Weir and Intake
A diversion structure is required across the nallah for diverting its water for power
generation. The nallah bed consists of pebbles, gravels and boulders. Such weirs are suited
for mountainous streams as they do not much interfere with the regime of the stream. It is
proposed that the weir shall be constructed in full width of stream to avoid any restriction to
flow that could cause an afflux.
4.2.2 Intake and Power Channel
The water from diversion weir is lead to desilting tank through rectangular intake channel
(Refurbishment). The details and photograph of construction of power channel are shown in
Fig.4.9 and Fig.4.10 respectively.
38. 31
4.2.3 Desilting-cum-Forebay Tank
As per site conditions and requirement of desilting tank and forebay which are constructed
combined. A desilting chamber is considered very essential for removing the silt from the
water and to minimize the abrasion effects on the turbine runners. The existing desilting-cum-
forebay tank is quite adequate to remove the silt efficiently.
Criterions adopted for desilting-cum-forebay tank design are as follows:
Desilting tank comprises a concrete rectangular tank of 1.5 meters width and 5.0
meters length.
The discharge outgoing from desilting-cum-forebay tank for power generation is 0.12
cumec.
One valve is provided at outlet for silt flushing from the desilting tank.
The silt-ridden water is discharged back into the nallah.
Free board as 0.30 m is provided at desilting tank.
The existing desilting-cum-forebay tank has sufficient storage capacity for 6.0 kW
generation.
The detail of desilting-cum-forebay tank is shown in Fig.4.11. Photograph in Fig.4.12 shows
the details of construction of desilting-cum-forebay tank.
Fig.4.11: Desilting-cum-forebay tank
39. 32
Fig.4.12: Forebay construction at site
4.2.4 Penstock
Water from forebay is being taken to the powerhouse to run hydraulic turbine through
pressurized penstock pipe from forebay tank. The penstock pipe of mild steels is selected
with 254 mm diameter from forebay tank to cross flow turbine.
4.2.5 Power House Building
Powerhouse building is a simple structure housing for turbine, generating units, draft tube,
auxiliary equipment, control panels and suitable outlet for tail water discharge.
The main features of the powerhouse building are as follows.
i. The building is of size 12.0 ft x 10.0 ft x 10.0 ft to accommodate 1 no turbine
generating unit of 5 kW, control panels, auxiliary equipment etc.
ii. The height of the building is kept 10.00 ft.
iii. The power house building partly below the ground level in order to provide proper
insulation from ground.
iv. Walls of the building are made of CGI sheets.
Fig.4.13 shows the photographs of power house construction. Photograph in Fig.4.14 shows
the transportation of turbine in power house building. Fig.4.15 shows the view of the power
house building.
41. 34
Fig.4.15: View of power house building during construction
Figs.4.16-4.18 show the photographs taken during installation of machines in the power
house.
Fig.4.16: Installation of turbine at site
43. 36
Chapter-5
PERFORMANCE TESING OF MODIFIED CROSS FLOW TURBINE
5.1 GENERAL
As discussed in previous chapter that a pico hydro site has been developed under this project
by installing the modified cross flow turbine based generating unit. The generating unit was
tested and based on the test results efficiency of turbine was determine.
5.2 SALIENT FEATURES
1. Location
I. State : Uttarakhand
II. District : Chamoli
III. Town : Gopeshwar
IV. Village Panchayat/Village : Mandal
V. Access : 1km on foot from Mandal.
Mandal is 13 km on road from
Gopeshwar, Gopeshwar is 250 km
from Dehradun
2. Geographical Coordinates
I. Longitude : 79°16’28” E
II. Latitude : 30°27’26” N
III. Altitude : 4868ft
3. Hydrology
I. Name of River/Nallah : Balkhila
II. Dependable flow as adopted in
Design for power generation
: 200 lps
III. Type of rivulet : Perennial
IV. Discharge
Minimum
Maximum
:
:
600
3500 lps (estimated)
4. Desilting-cum-Forebay Tank
a. Length 5.0m
b. Width 1.5m
c. Depth 1.5m
d. Free board 0.310m
e. Type/ Material Concrete
f. Design discharge 200 lps
5. Penstock
a. Numbers 1 No piece
b. Outer Diameter 323.85 mm
c. Thickness 6 mm
d. Length 5.3 m
e. Design discharge 200lps
f. Material MS
44. 37
6. Tail Race
a. Shape Rectangular
b. Construction Stone Masonry
c. Size 3 m x 0.3 m
d. Length 3 m
7. Turbine
a. Type Cross Flow
b. Number 1
c. Capacity of turbine 5kW
9. Generator
a. Type of generator Synchronous
b. Setting Horizontal
c. Number 1 Nos.
d. Capacity of each Generator 7.5 kVA, 0.85 pf
10. Power
a. Installed capacity 1× 5 kW
5.3 HEAD MEASUREMENT
In order to measure the head, Ultrasonic level sensor has been used to measure the head race
water level. Height of the level sensor has been calculated from center line of turbine by
using fundamental method of water tube as scale. The Ultrasonic level sensor readings are
given in Table 5.1.
Table 5.1: Reading of Ultrasonic level sensor
Load (kW) 3.465 3.315 2.205 2.580
Time of Start (hours) 1230 1250 1305 1410
Reading interval (minute) 1 1 1 1
S. No. ULS
Reading (m)
ULS
Reading (m)
ULS
Reading (m)
ULS
Reading (m)
1 0.885 0.882 0.804 0.820
2 0.884 0.881 0.803 0.822
3 0.888 0.882 0.803 0.822
4 0.889 0.886 0.802 0.82
5 0.884 0.883 0.802 0.821
6 0.889 0.881 0.804 0.822
7 0.884 0.884 0.806 0.822
8 0.889 0.886 0.803 0.821
9 0.886 0.885 0.800 0.822
10 0.889 0.887 0.805 0.817
11 0.883 0.883 0.803 0.899
12 0.887 -- 0.805 --
13 0.885 -- 0.808 --
14 0.889 -- 0.806 --
15 0.883 -- 0.803 --
Average Depth (h) in m 0.8863 0.8836 0.8038 0.8280
45. 38
The net head is determined by using the following expressions:
H = net head of water in m
= - (8)
Where,
H1 = Height of Ultrasonic level sensor from center line of turbine
= 5.30m
h = Reading of ultrasonic level sensor
v = Average flow velocity in pipe in m/s
k = Bend loss coefficient
= 0.4
D = Inside diameter
= 0.310
f = Friction loss efficient
= 0.025
l = Length of penstock
= 5.3 m
H = - (9)
Where, H is in m and Q is in m3
/s.
5.4 MEASUREMENT OF DISCHARGE
Clamp on Ultrasonic transit time flow meters (UTTFs) were used for discharge measurement.
Two clamp-on type ultrasonic transit-time flowmeters (UTTFs) were used. One UTTF of RR
Flowmeter make (model F-133) and another one of Ultraflux make (model- 801-P) were used
for discharge measurement. The pair of transducers of each flowmeter was fixed in reflection
mode. The transducers of Ultraflux UTTF were installed downstream of the transducers of
the RR flow meter UTTF. The readings taken by UTTFs are given in Table 5.2-5.3.
Table 5.2: Measurement of Discharge by UTTF-1
Load (KW) 3.465 3.315 2.205 2.580
Time of Start
(hours)
1230 1250 1305 1410
Reading Interval
(min)
1 1 1 1
S. No. UTTF Reading
(m3
/s)
UTTF Reading
(m3
/s)
UTTF Reading
(m3
/s)
UTTF Reading
(m3
/s)
1. 0.153 0.149 0.073 0.086
2. 0.151 0.147 0.074 0.087
3. 0.150 0.145 0.073 0.089
4. 0.151 0.145 0.073 0.088
5. 0.155 0.155 0.071 0.089
6. 0.152 0.153 0.073 0.088
47. 40
5.5 MEASUREMENT OF ELECTRICAL POWER OUTPUT
Yokogawa WT 230 make power analyser was used for power measurement. The readings
taken by power analyser are given in Table 5.4.
Table 5.4: Electrical power measurement
Load (kW) 4.2675 4.0852 2.205 2.580
Time of Start (hours) 1230 1250 1305 1410
Duration of test (minutes) 15 10 15 10
Time of integration (T)
(hour: min : sec)
00:15:00 00:10:00 00:15:00 00:10:00
Energy reading (Wh) 0.2134 0.1389 0.1102 0.086
Power calculated (P=Wh / T)×(W) 0.854 0.817 0.441 0.516
Power output
(Pe= P x CTR) (kW)
4.2675 4.0852 2.205 2.580
5.6 CALCULATION OF TURBINE EFFICIENCY
The average values of electrical power output, discharge and head calculated in the preceding
tables are used in the following table for calculating the efficiency of the generating unit.
The efficiency of the turbine-generator unit is given by
(10)
Ph = g HQ (11)
Where,
= actual density of water (at 10.4C and 150 kPa absolute)
= 999.8 kg/m3
(Reference: IS/IEC-41)
g = actual acceleration due to gravity (at 304’ latitude and 1550 m altitude above
MSL)
= 9.788 m/s2
(Reference: IS/IEC-41)
Q = discharge of water through the turbine in m3
/s
Table 5.5 gives values for calculating efficiency of turbine.
)
h
(P
turbine
to
input
power
Hydraulic
)
e
(P
genertor
of
output
power
Electrical
η
48. 41
Table 5.5: Values for calculating efficiency of turbine
Quantity Load on Machine (kW)
Discharge (Q)
(m3
/s)
0.151 0.146 0.073 0.088
Average depth (h) 0.8863 0.8836 0.8038 0.8280
Net Head from equation
(4) - (m)
4.052 4.078 4.412 4.349
Hydraulic Power Input
from equation (2) -(kW)
5.987 5.826 3.152 3.745
Electrical Power Output
(Pe) - (kW)
4.2675 4.0852 2.205 2.580
Unit Efficiency from
equation (1) - (%) 71.28 70.12 69.97 68.97
Photographs taken during performance testing of the generating unit are shown in Figs.5.1-
5.9.
52. 45
Fig.5.7: ULS installed at tailrace channel for level measurement
Fig.5.8: Precision Digital Wattmeter connected for electrical power output
measurement
54. 47
Chapter-6
CONCLUSION
In micro-hydro potential sites, cross flow hydro turbine is the suitable alternative to provide
the energy due to its low initial cost, easy construction, installation and maintenance.
However, cross flow turbine suffers the problem of low performance as compared to
conventional hydro turbines. Under the present study, an attempt has been made to enhance
the cross flow turbine efficiency by improving the flow conditions/direction inside the turbine
runner. A guide mechanism having different types of airfoils (Symmetrical and
unsymmetrical) has been investigated and the performance in term of efficiency of the
modified turbine is compared with the conventional cross flow turbine design. Following
conclusions are drawn from the study.
1. In order to investigate the turbine performance at different operating conditions,
numerical simulation (CFD) using commercially available software (ANSYS) was
used. Further, the numerical results have been validated with the experimentation
carried out in the Hydraulic Measurement Laboratory, Department of Hydro and
Renewable Energy, Indian Institute of Technology Roorkee, India.
2. Based on the numerical simulations, it is found that the guide tube/vane improves the
flow characteristics inside the runner and hence the efficiency. The placement angle
of the guide vanes affects the flow behavior which in turn flow condition over guide
vane. It is, therefore, the placement angle for both symmetrical and unsymmetrical
vane was required to be optimized and it is found that the cross flow turbine provides
better performance with symmetrical and unsymmetrical guide vane having
placement angle of 55º and 45º respectively.
The positioning of the guide vanes has also been optimized by placing the guide vanes
at left, center and right positions and it has been observed from the numerical
simulations that the ‘right’ position of the guide vane yields better performance
corresponding to given operating conditions.
3. Further, in order to attain the optimum placement angle and placement position for
both symmetrical and un-symmetrical vanes, it was desired to select the suitable
airfoil from the two. Therefore, both airfoils have been simulated under similar
operating conditions and it has been found that the cross flow turbine at 125% of
design discharge and with unsymmetrical guide vane yields the maximum efficiency
as 76.61% which is about 5.84% higher than the conventional design cross flow
turbine without guide vane and 4.50% higher than the turbine with symmetrical guide
vane.
4. The numerical results of the cross flow turbine have been validated by rigorous
experimental testing in laboratory. Therefore, a cross flow turbine model was
55. 48
fabricated and tested under different operating conditions. Based on the experimental
investigations it was found that numerical results are on similar lines and a maximum
of 4.57% deviation in results was observed which may be due to instrumental or
measurement error.
5. Further, in order to test the prototype of modified cross flow turbine a pico hydro
power site was identified at Balkhila River in Chamoli District near Mandal village.
The turbine is deployed. Further, the modified turbine was tested at site and it has
been found that the turbine yields its maximum performance as 71.28% corresponding
to 0.151 m3
/s discharge.
