Table of ContentNoTitlePage

1Objective2

2Learning Outcome2

3Safety measures2

4Materials and Apparatus3

5Procedure3

6Results 4

7Discussion5-14

8Conclusion15

9Reference15

10Appendix15

Objectives:To study the characteristics curves of a Pelton turbine operating at different flow rates with high head and low head.Learning Outcomes:Upon completion of the experiment, student should understand the characteristics of torque, power output and efficiency of turbines at different rotational speed of turbines, at high head and low head.

Safety Measures:1. Make sure that the scale reading for the Pelton turbine, to obtain the values of m1 and

m2, is stable before the reading is taken as it tend to move up and down.2. To be careful of the water that is leaking from the apparatus.

3. Only turn on the throttle valve partially (one round) because the rotor is too powerful

to be measured within the force balance limit. Results:Part A (i) : High head, with large flow rate.

Table 1 (i) : Flow rate measurement data.

In the following table, m1 and m2 is obtained from the scale. Fb1 and Fb2 is basically converting m1 and m2 respectively in terms of Newton. Fb is obtained by subtraction of Fb1 from Fb2. N1 and N2 is obtained from the Pelton turbine. N is the average of N1 and N2. N is then converted to Hertz.

Table 2 (i) : Pelton turbine experimental data.In the following table, Q, Fb and N is obtained from the previous tables. P1 is obtained by converting the pressure exerted on the turbine, which is 1.5kgf/cm2, to bar. Hi is obtained from converting Pi from bar to metres.

Ph is obtained by the following formula = x g x Hi x Q,

where is the density of water (1000kg/m3) ;

g is the gravitational acceleration (9.81m/s2)

T is obtained by multiplying Fb with the radius of the turbine, which is 0.042m.

Pb is obtained by the following formula = 2NT.

Et (%) is obtained by dividing Pb with Ph and converting it to percentage.

Table 3 (i) : Pelton turbine experimental summary.Part A (ii) : High head, with small flow rate.

Table 1 (ii) : Flow rate measurement data.

In the following table, m1 and m2 is obtained from the scale. Fb1 and Fb2 is basically converting m1 and m2 respectively in terms of Newton. Fb is obtained by subtraction of Fb1 from Fb2. N1 and N2 is obtained from the Pelton turbine. N is the average of N1 and N2. N is then converted to Hertz.

Table 2 (ii) : Pelton turbine experimental data.In the following table, Q, Fb and N is obtained from the previous tables. P1 is obtained by converting the pressure exerted on the turbine, which is 1.5kgf/cm2, to bar. Hi is obtained from converting Pi from bar to metres.

Ph is obtained by the following formula = x g x Hi x Q,

where is the density of water (1000kg/m3) ;

g is the gravitational acceleration (9.81m/s2)

T is obtained by multiplying Fb with the radius of the turbine, which is 0.042m.

Pb is obtained by the following formula = 2NT.

Et (%) is obtained by dividing Pb with Ph and converting it to percentage.

Table 3 (ii) : Pelton turbine experimental summary.

Using the data from Table 3 (i) and Table 3 (ii), in which were using the values for high head large flow rate and high head small flow rate, the following graphs are drawn.

Graph 1 : T versus N (Series 1 represents the large flow rate, series 2 represents the small flow rate)

Graph 2 : Pb versus N (Series 1 represents the large flow rate, series 2 represents the small flow rate)

Graph 3 : Et versus N (Series 1 represents the large flow rate, series 2 represents the small flow rate)

Part B (i) : Low head, with large flow rate.

Table 1 (iii) : Flow rate measurement data.

In the following table, m1 and m2 is obtained from the scale. Fb1 and Fb2 is basically converting m1 and m2 respectively in terms of Newton. Fb is obtained by subtraction of Fb1 from Fb2. N1 and N2 is obtained from the Pelton turbine. N is the average of N1 and N2. N is then converted to Hertz.

Table 2 (iii) : Pelton turbine experimental data.In the following table, Q, Fb and N is obtained from the previous tables. P1 is obtained by converting the pressure exerted on the turbine, which is 1kgf/cm2, to bar. Hi is obtained from converting Pi from bar to metres.

Ph is obtained by the following formula = x g x Hi x Q,

where is the density of water (1000kg/m3) ;

g is the gravitational acceleration (9.81m/s2)

T is obtained by multiplying Fb with the radius of the turbine, which is 0.042m.

Pb is obtained by the following formula = 2NT.

Et (%) is obtained by dividing Pb with Ph and converting it to percentage.

Table 3 (iii) : Pelton turbine experimental summary.Part B (ii) : Low head, with small flow rate.

Table 1 (iv) : Flow rate measurement data.

In the following table, m1 and m2 is obtained from the scale. Fb1 and Fb2 is basically converting m1 and m2 respectively in terms of Newton. Fb is obtained by subtraction of Fb1 from Fb2. N1 and N2 is obtained from the Pelton turbine. N is the average of N1 and N2. N is then converted to Hertz.

Table 2 (iv) : Pelton turbine experimental data.In the following table, Q, Fb and N is obtained from the previous tables. P1 is obtained by converting the pressure exerted on the turbine, which is 1kgf/cm2, to bar. Hi is obtained from converting Pi from bar to metres.

Ph is obtained by the following formula = x g x Hi x Q,

where is the density of water (1000kg/m3) ;

g is the gravitational acceleration (9.81m/s2)

T is obtained by multiplying Fb with the radius of the turbine, which is 0.042m.

Pb is obtained by the following formula = 2NT.

Et (%) is obtained by dividing Pb with Ph and converting it to percentage.

Table 3 (iv) : Pelton turbine experimental summary.Using the data from Table 3 (iii) and Table 3 (iv), in which were using the values for low head large flow rate and low head small flow rate, the following graphs are drawn.

Graph 1 : T versus N (Series 1 represents the large flow rate, series 2 represents the small flow rate)

Graph 2 : Pb versus N (Series 1 represents the large flow rate, series 2 represents the small flow rate)

Graph 3 : Et versus N (Series 1 represents the large flow rate, series 2 represents the small flow rate)

Discussion:

There are two types of turbines, reaction and the impulse, the difference being the manner of head conversion. In the reaction turbine, the fluid fills the blade passages, and the head change or pressure drop occurs within the runner. An impulse turbine first converts the water head through a nozzle into a high-velocity jet, which then strikes the buckets at one position as they pass by. The runner passages are not fully filled, and the jet flow past the buckets is essentially at constant pressure. Impulse turbines are ideally suited for high head and relatively low power. The Pelton turbine used in this experiment is an impulse turbine.

The Pelton turbine consists of three basic components as shown in Figure 1: a stationary inlet nozzle, a runner and a casing. The runner consists of multiple buckets mounted on a rotating wheel. The jet strikes the buckets and imparts momentum. The buckets are shaped in a manner to divide the flow in half and turn its relative velocity vector nearly 180.

Figure 1 : Schematic of an impulse turbine.

The primary feature of the impulse turbine is the power production as the jet is deflected by the moving buckets. Assuming that the speed of the exiting jet is zero (all of the kinetic energy of the jet is expended in driving the buckets), negligible head loss at the nozzle and at the impact with the buckets (assuming that the entire available head is converted into jet velocity), the energy equation applied to the control volume shown in Figure 1 provides the power extracted from the available head by the turbine

Pavailable = QHavailablewhere Q is the discharge of the incoming jet, and Havailable is the available pressure head on the nozzle.By applying the angular momentum equation (assuming negligible angular momentum for the exiting jet) to the same control volume about the axis of the turbine shaft the absolute value of the power developed by the turbine can be written asP = T = 2NTwhere is the angular velocity of the runner, T is the torque acting on the turbine shaft, and N is the rotational speed of the runner.

The efficiency of the turbine is defined as the ratio between the power developed by the turbine to the available water power = P / Pavailable

The following are theories related to the Pelton turbine :

1. It is a tangential flow turbine (water hits runner tangential at the blades) where as in radial turbine water does not hit it, flows over the blades with high pressure and velocity.2. Energy present at inlet is only kinetic but in radial energy at inlet is kinetic and

pressure energy

3. Generally used in hydroelectric plants where water level is high (high head).Conclusion:

In conclusion, the objectives of this experiment has been achieved, which is to study the characteristics curves of a Pelton turbine operating at different flow rates with high head and low head. It has been observed that for both high head and low head, the curves for the larger flow rate are higher than the curves for the smaller flow rate. The proof for this is the graphs drawn for torque, brake power and useful fluid power against the number of rotations per second. Since the objectives of have been met, this experiment is proven to be successful.

References:

1. Robertson, J.A., 1993. Pelton turbine experiment [Online] Available from :

[Accessed on 24th June 2012]

2. Wajid, A., 2009. Theory of Pelton turbine [Online] Available from :

[Accessed on 24th June 2012]

3. Lemelson, P., 2012. The Pelton turbine [Online] Available from :

[Accessed on 24th June

2012]