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Kaplan Turbine - Welcome to Engi

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Kaplan Turbine - Welcome to Engi Powered By Docstoc
					 KAPLAN
TURBINE
TEST RIG
                            KAPLAN TURBINE TEST RIG

OBJECTIVE:             To study the operation of a Kaplan Turbine.

AIM:           To determine the output power of Kaplan Turbine.
               To determine the efficiency of the Kaplan Turbine.
               To plot the performance characteristics curves.

INTRODUCTION:
The Kaplan like the Francis is a reaction turbine. It operates in an entirely closed conduit
from inlet to tail race. Runner has two major differences. Firstly in Francis runner the
water enters radially while in Kaplan type; water strikes on the blades axially. Secondly
the number of blades in Francis runner is 16 to 24 but in the Kaplan it is only 3 to 6. This
reduces the contact surface with water and hence the frictional resistance. It is used for
comparatively low head and large quantity of water is available.

THEORY:
Kaplan turbine is an axial flow reaction turbine. The reaction turbine operates with its
wheel submerged in water. The water before entering the turbine has pressure as we ll as
kinetic energy.

DESCRIPTION:
The vertical shaft Kaplan turbine consists mainly of a spiral casing with sporting legs, an
outer bearing pedestal, and rotor assembly with adjustable bladed runner, shaft and brake
drum and brake arrangement all mounted on a suitable cast iron base plate. A straight
conical draft tube is provided with a draught bend immediately after the runner, for the
purpose of regaining the kinetic energy from the exit water and also facilitating easy
accessibility of the turbine due to its location at a higher level than the tail race. (The
operation of regaining the kinetic energy from the exit water by some means of draught
tube assumes great importance in high specific speed hydraulic turbines, as the absolute
velocity of water leaving the runner in high}. A transparent hollow Perspex cylinder is
provided in between the draught bend and the casing for observation of flow behind the
runner. A rope brake arrangement is provided to load the turbine. The output of the
turbine can be controlled by adjusting the guide vanes, for which purpose suitable control
mechanisms are provided. The net supply head on the turbine is measured by a pressure
gauge and for the measurement of speed, use hand tachometer.

CONSTRUCTIONAL SPECIFICATION:
 1. SPIRAL CASING: Is of close grained cast iron with integral legs and 250mm.
      Flanged inlet. The casing is designed for constant velocity water distribution.

 2. RUNNER: Is of bronze with four aero foil blades, designed to the latest hydro-
      dynamic principles. The runner blade pitch can be adjusted by a suitable
      mechanism operating through the hollow shaft. All parts coming in contract with
      water are made of stainless steel to prevent corrosion.
 3. GUIDE VANE MECHANISM: Consists of bronze guide vanes cast integral with
      their spindles. By suitable external link mechanism these can be set at different
      relative positions, and two external dummy guide vanes are provided to indicate
      the exact position of the actual guide vanes working inside the turbine, thus
      showing the relative water passages through the guide apparatus for the different
      positions of the guide vanes.

 4. SHAFT: Is of EN 8 Chrome plated and hollow to accommodate the runner blade
      control mechanism.

 5. BALL BEARING: Are of double row rigid radial deep groove type in the ca sing and
      double row self aligning type in the pedestal, designed for long life with provision
      for grease lubrication.

 6. BRAKE ARRANGEMENT: Consists of a machined and polished cast iron brake
      drum cooling water pipes, internal water scoop, discharge pipe, standard cast iron
      dead weights, spring balance, robe brake etc. arranged for loading the turbine.

 7. BASE PLATE CUM PERPEX BRACKET: Of cast iron, box type ribbed
     construction.

 8. FINISH: Of high standard suitable for laboratory use in Technical Institutions.

UTILITIES REQUIRED:
     1. Water supply
     2. Three phase supply, 440 volt AC
     3. Drain

EXPERIMENTAL PROCEDURE:

STARTING UP
Make sure before starting that the pipe lines are free from foreign matter. Also note
whether all the joints are water tight and leak proof. Prime the pump and start it. TO
AVOID OVERLOAD IN THE MOTOR PARTS AT THE PARTS AT THE TIME OF
STARTING, KEEP 25% ON OPEN POSITION BOTH BUTTERFLY VALVE AND
TURBINE GUID VANE. See that all the ball bearings and bush bearings in the units are
properly lubricated.
Then slowly open the butterfly valve near the turbine, and see that the pump develops the
rated head. Pressure gauge is used to measure the supply head on the turbine. If the pump
develop the rated head slowly open the turbine guide vanes by rotating the hand wheel
(which operates the guide vanes through suitable link mechanism) until the turbine attains
the normal rated speed of 1500 rpm. Run the turbine at the rated speed for about ten
minutes and carefully note the following.
        1. Operating of the bearings, temperature rise, noise etc.
        2. Vibration of the unit
        3. Steady constant speed and speed fluctuations, if any.
In addition to this, on the pump side note the operation of the stuffing box. (The stuffing
box should show an occasionally drip of water. If the gland is over tightened, the leakage
stops, but the packing will heat up, burn and damage the shaft).
If the operations of the above parts are normal load the turbine slowly and take readings.
To load the turbine, standard dead weights are provided with figures, stamped on them, to
indicate their weights. Open the water inlet valve and allow some cooling water through
the brake drum when the turbine runs under load, so that the heat generated by the brake
drum is under load. So that the heat generated by the brake drum is carried away by the
cooling water. Do not suddenly load the turbine. Load the turbine gradually and at the
same time open the guide vanes to run the turbine at the normal speed.

TO SHUT DOWN
Before switching off the supply pump set first remove all the dead weights on the hanger,
close the cooling inlet water gate valve. SLOWLY CLOSE THE GUIDE VANES TO
ITS 75% CLOSED POSITION. Manometer cocks pitot tube cocks should also be closed
in order to isolate the manometer. Then partially close the main gate valve, and switch off
the supply to pump set. NEVER SWITCH OFF THE SUPPLY TO PUMP SET WHEN
THE TURBINE IS WORKING UNDER LOAD. If the electric line trips off when the
turbine is working, first in- load the turbine, close all the valves and cocks. Start the
electric motor when the line gets the power and then operate the turbine by opening the
valves in the order said above.

TESTING
Water turbines are tested in the hydraulic laboratory to demonstrate how tests on small
water turbine are carried out to study their construction and to give the students a clear
knowledge about the different types of turbines and their characteristics.
Turbines shall be first tested at constant net supply heat at the rated value of 5m by
varying the load, speed, guide vane setting. However, the net supply head on the turbine
may be reduced and the turbine tested in which ease the power developed by the turbine
and the best efficiency speed will also be reduced. Through the turbine can also be tested
at higher net supply heads, the supply pump set cannot develop the higher head at the
same time maintaining higher rate of flow.
The output power from the turbine is calculated from the readings taken on the brake and
the speed of the shaft. The input power supplied to the turbine is calculated from the net
supply head on the turbine and discharge through the turbine. Efficiency of the turbine
being the ratio between the output and input can be determined from these two readings.
The discharge is measured by the Pitot tube and with the differential manometer. Supply
head is measured with the help of the pressure gauge. The speed of the turbine is
measured with a hand tachometer.
It is suggested that the turbine shall be tested at normal speed, 3 speeds below normal
speed, 3 speeds above normal speed, guide vanes. The run away speed (the speed of the
turbine at no load and at rated conditions of supply head) and the pull out torque ( the
maximum torque at stalled speed) may also he observed.
After starting and running the turbine at normal speed for some time load the turbine and
take readings
For any particular setting of the guide vanes first run the turbine at light load and then
RECORD THE FOLLOWING:
Net supply head (Pressure gauge reading)
Discharge (Differential manometer reading)
Turbine shaft speed (Tachometer)
Brake weight (Dead weights plus hanger and rope brake weights)
Spring balance readings
For any particular setting of the guide vanes first run the turbine at light load and then
gradually load it, by adding dead weights on the hanger. The net supply on the turbine
shall be maintained constant at the rated value, and this can be done by adjusting the gate
valve fitted just before the turbine.

SPECIFICATION:
1. Rated supply head          :       5.0 Meters
2. Discharge                  :       6000 lpm
3. Rated Speed                :       1500 rpm
4. Power Output               :       3.75 Kw (5HP)
5. Run away speed             :       2750 rpm
6. Runner outside dia         :        200mm
7. Hub diameter               :       110 mm
8. Hub ratio                  :       0.55
9. No. of runner blades       :       4
10. No. of guide vanes        :       16
11. P.C.O. Guide vanes        :       280mm
12. Brake drum diameter       :       300mm
13. Rope brake diameter       :       15mm
SUPPLY PUMP SET:
1. Rated Head                 :     8.5 meters
2. Discharge                  :     6000 LPM
3. Normal Speed               :     1440 rpm
4. Power Required             :     20 HP (15Kw)
5. Size of Pump               :     250mm X 250mm
6. Type                       :Medium Speed mixed Flow. Single and suction volute
7. Impeller Diameter          :      260mm
8. Cone angle                 :      750

FLOW MEASURING UNIT:
1. Diameter of Pitot :                 4.0mm
2. Diameter of Pipe  :                150mm
3. Manometer         :                Double column Differential type
FORMULAE:

Total Head:   H = 10 X P (m of water)
              P = Pressure gauge reading, kg/cm2
              V = Vacuum gauge reading
Velocity of water in pipe    v = Cpitot √ [2gh {( m / w) – 1}]

                             w = Density of water = 1000 kg/m3
                             m = Density of Manometer fluid i.e. CCL4 = 1590 kg/m3
                             h = Differential pressure of Manometer (m)
                             Cpitot = Co- efficient of pitot tube
Discharge                    Q=AXv           (m3 /s)
                             A = Cross-sectional area of pipe
       B.H.P (Output) = [2N (w1 – w2 ) {(Db + DR) / 2}] / 4500 H.P
w1 = Fixed spring balance reading (kg)
w2 = Adjustable spring balance reading (kg)
N = RPM of Runner shaft
Db = Diameter of brake drum
DR = Diameter of rope
       H.P Hyd (Input) =  w Q H / 75                H.P

w = Density of water
Q = Discharge
H = Total Head
              turbine = (B.H.P / H.P Hyd)x100
OBSERVATION           DATA:
       d = Diameter of pipe = 260 mm
       a = Cross-sectional area of test section/pipe = 0.05309 m3
       m = Density of Manometer fluid i.e. CCL4 = 1590kg/cm3
       w = Density of water = 1000 kg/cm3
       g = Acceleration due to gravity = 9.81 m/s2
OBSERVATION TABLE:
 S. N. RPM (N)       Pr. Gauge reading Differential Pr. Dead weight Spring balance
                     P (kg/cm2 )           H (m)              w1 (kg)   w2 (kg)
 1
 2
 3
CALCULATION TABLE:
 S.N. Total Head Velocity            Discharge       Output       Input  Turbine
        H               v            Q                                   Efficiency
                                                                         %
 1
 2
 3
PRECAUTIONS & MAINTENANCE INSTRUCTIONS:
As these units are build very sturdily, they do not require any routine or regular
maintenance. However, we recommend the following to be done about once in a year to
increase the life of the elements.
Lubricate all the working parts where a provision for lubrications is made. Grease cups
are provided for lubricating ball bearings. Remove the grease drain plugs where fitted,
and inject fresh grease through grease cups until wasted grease along with a portion of
fresh grease is ejected out through the grease drain hole. Then run the machine for a few
minute to eject the excess grease in bearing housings. Then tit the grease drain plug. Over
greasing results in excessive heat due to a pumping action of the bearings a nd it is
harmful as under greasing.
Suitable grease contains no mineral acid, free alkali or foreign matter. Stability is of the
at most importance and the grease should show no tendency to gum, thin out or separate
in to its constituents on standing or in service. Grease containing filling agents should not
be used, for the presence of such substances as graphite, talcum etc., even in an extremely
finely divided state, will give rise to lapping of the bearing parts. For normal condition of
operation soap grease of softer consistency for working temperature up to 75 0 C having a
melting point about 1500 C/l 75°C shall be used.
Clean the stuffing box, repack and lubricated it. If any packing ring is worn out replace it
with good quality asbestos graphited packing. While repacking, the successive ring joints
should be staggered by 90 or 180. Tight the gland nuts evenly, and allow the stuffing box
to drip water occasionally to lubricate the packing rings.
Never run the pump without water in it, as this would cause damage to stuffing box, bush
bearing etc.
Never try to throttle the suction side of the pump to control discharge as it would
seriously affect the performance of the pump.
SAMPLE CALCULATION:

OBSERVATION TABLE:

 S. N. RPM (N)          Pr. Gauge reading   Differential Pr. Dead weight      Spring balance
                        P (kg/cm2 )         H (m)            w1 (kg)          w2 (kg)
 1      1684            1.0                 0.375            20               1.5
 2      1100            1.0                 0.13             24               2.0

CALCULATION TABLE:

 S.N.   Total    Head     Velocity   Discharge       Output        Input        Turbine
        H                 v          Q                                          Efficiency
                                                                                %
 1      1684              10         0.10830         14.44         7.17         49.70%
 2      1100              10         0.06381         08.50         5.57         65.59%

				
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posted:11/15/2010
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