Performance of Kaplan turbine

1.        Objectives:

In this experiment, the main aims are:

1.    Determine the Turbine Performance Characteristics of output break power and efficiency of an adjustable blade Kaplan Turbine.

2.    Study the constructional detail of the Kaplan turbine and draw its fluid flow circuit.

2.        Introduction:

The hydraulic turbines are classified according to the type of energy available at the inlet of the turbine, direction of flow through the vanes. The Hydraulic turbines mainly of two types:

1.      Impulse Turbine

2.      Reaction Turbine

Kaplan Turbine is axial flow reaction turbine. If the water flows parallel to the axis of the rotation of the shaft the turbine is known as axial flow turbine. And of the head at the inlet of the turbine is the sum of pressure energy and kinetic energy and during the flow of water through runner at part of pressure energy is converted into kinetic energy, the turbine is known as reaction turbine. When the vanes are fixed to hub and they are not adjustable the turbine is known as propeller turbine. But if the vanes of the hub are adjustable the turbine is known as Kaplan Turbine after the name of V. Kaplan an Austrian Engineer. This turbine is suitable where a large quantity of water at low heads is available. The main parts of a Kaplan Turbine are:

1.      Scroll casing

2.      Guide vanes mechanism

3.      Hub with vanes or runner of the turbine

4.      Draft tube.

3.        Theory and Analysis:

1.      Set the nozzle guide vane angles to a specified degree by means of the lever.

2.      Measure the following values:

a.       The tachometer reading rpm (N)

b.      The dead weight in kg (m)

c.       The force on the indicator balance in lb. (F)

d.      The deflection of U-tube manometer in mm (∆h)

e.       Inlet static pressure of the turbine in m (Hi)

f.        Outlet static pressure of the turbine in m (Ho)

(1)   calculate the flow rate Q

(3)   The power extracted from the fluid

4.        Description of Experimental Setup and Instrumentation:

Armfield laboratory water turbines are scale replicas of modern large capacity hydraulic machines specifically designed for educational purposes. They are of substantial proportions and are fully instrumented to allow comprehensive testing, producing results which may be used to predict the performance of industrial turbines. The view of a Kaplan Turbine with its flow circuit is shown in Fig. 1. The turbines are supplied in complete self-contained testing systems.

Fig. 1 The view of a Kaplan Turbine testing system.

4.1 The main components of the experimental setup are:

1.      Kaplan turbine.

2.      The Draft tube.

3.      Surge tank.

4.      Service Axial pump.

5.      Three phase variable speed motor.

6.      Butterfly valve.

7.      Pipework.

8.      Orifice flow meter.

9.      Mechanical dynamometer.

 4.2 Instrumentation:

·         Orifice Flow Meter.

·         Bourdon Type Pressure Gauges.

·         Tachometer.

·         Mechanical Dynamometer.

·         Voltmeter.

·         Ammeter.

·         Power Factor Transducer.

4.3 SPECIFICATION:

·         A Kaplan reaction turbine with 200 mm runner, designed to be mounted vertically, complete with volute case, draft tube and guide vanes. The output power is absorbed by a mechanical dynamometer. Shaft speed is indicated on a direct reading belt driven dial type tachometer. Inlet branch pressure is indicated by a Bourdon gauge mounted on the turbine body.

·         The unit is constructed as a self-contained test circuit including, pipe work, an axial flow horizontal shaft two speed pump with variable angle impeller blades, full instrumentation and controls.

4.4 The test rig constant

·         inlet pipe diameter: 33.5 cm

·         Outlet pipe diameter: 30.5 cm

·         Dynamometer radius: 15.4cm

·         Orifice meter calibration equation Q (m3/min) = 17.02 (∆h)0.5011 where ∆h is the manometer difference reading in meters.

5.         Test Conditions and Experimental Procedure:

1.      Unload the turbine if there is any load on it.

2.      Fill the sump tank with sufficient amount of water.

3.      Switch on the power supply to start the axial pump.

4.      Now open the delivery valve slowly and adjust the required flow rate at the inlet of turbine.

5.      Adjust the load on rope break balance and the delivery valve to get the required reading on the rotational speed transducer.

6.      Repeat the above procedure for different inlet flow rate.

6.        Results:

Record calculated results on the attached summary results sheets following the recorded measured data tables.

plot the following:

·         Break power against the flow rate at constant rotation speed

·         The turbine efficiency of the turbine against the flow rate at constant rotation speed.

7.        Discussions:

Examine and describe the trends of the graphs obtained, relating this to the changing performance of the turbine as the flow rate changes. Locate the point of maximum efficiency and the flow rate at which it occurs.

8.        References:

·         List all references you might have used.

9.        Tables of Experimental Data and Results Summary:

The experimental data of the Test should fill in the following table

Table 1 The experimental data of Test.

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Performance of Kaplan Turbine