1.0
EXPERIMENTAL PROCEDURES 1.1
General Start-up Procedures 1. Connect the power plug to the nearest power supply. 2. Fill up the water reservoir of Hydraulics Bench up to 80% full. 3. Slacken the tensioning screw and belt to apply minimum force to the pulley. 4. Close the throttle valve then switch on the water pump. 5. Slowly open the throttle valve and spear valve to allow water to circulate. Note: If water is not flowing after the pump is on, loosen the air bleed valve at the centrifugal pump to bleed the air. 6. The unit is now ready for experiments.
1.2
Experiment 1.1 : Turbine Characteristics Objectives: To study the characteristic curves of a Pelton turbine operating at a different fluid flow rates with high head Procedures: 1. Perform the general start-up procedures. 2. Then, fully open the throttle valve and allow the water to circulate until all air bubbles have dispersed. 3. Open and adjust the spear valve until 1.5 kgf/cm2 of inlet water head is obtained. 4. Tighten up the tensioning screw on the pulley wheel until the turbine is almost stalled (rotor just turning). 5. Note the value of the pulley brake. Decide on suitable increments in force to give adequate sample points (typically 8 points between zero and maximum brake force). 6. Slacken off the tensioning screw so no force is being applied to the turbine, i.e. Fb at almost 0. Obtain the volumetric flowrate (Q), force reading (Fb), water head (P1) and turbine rotational speed (N), then record into the experimental data sheet. This represents the first point on the characteristic curve. 7. Tighten the screw to give the first increment in force for the brake. When readings are steady enough, record all the readings again. 8. Repeat step 7 above for a gradually increasing set of Fb values, i.e. increasing values of torque. The final sample point will correspond to the turbine stalling. 1
9. The recorded set of data may now be used for analysis and to plot the Pelton turbine characteristics curve. 10. Now decrease the volume flow rate to a new setting by changing the throttle valve position and at the same time also change the spear valve position to maintain the pressure at 1.5 kgf/cm2. Repeat the taking of samples for gradually increasing values of torque, as in Steps 4 - 9 above. Repeating this step will produce a series of result sets for comparison.
Experiment 1.2 : Turbine Characteristics Objectives: To study the characteristic curves of a Pelton turbine operating at a different flow rates with low head Procedures: 1. Perform the general start-up procedures. 2. Then, fully open the throttle valve and allow the water to circulate until all air bubbles have dispersed. 3. Open and adjust the spear valve until 1.0 kgf/cm2 of inlet water head is obtained. 4. Tighten up the tensioning screw on the pulley wheel until the turbine is almost stalled (rotor just turning). 5. Note the value of the pulley brake. Decide on suitable increments in force to give adequate sample points (typically 8 points between zero and maximum brake force). 6. Slacken off the tensioning screw so no force is being applied to the turbine, i.e. Fb at almost 0. Obtain the volumetric flowrate (Q), force reading (Fb), water head (P1) and turbine rotational speed (N), then record into the experimental data sheet. This represents the first point on the characteristic curve. 7. Tighten the screw to give the first increment in force for the brake. When readings are steady enough, record all the readings again. 8. Repeat step 7 above for a gradually increasing set of Fb values, i.e. increasing values of torque. The final sample point will correspond to the turbine stalling. 9. The recorded set of data may now be used for analysis and to plot the Pelton turbine characteristics curve. 10. Now decrease the volume flow rate to a new setting by changing the throttle valve position and at the same time also change the spear valve position to maintain the 2
pressure at 1.0 kgf/cm2. Repeat the taking of samples for gradually increasing values of torque, as in Steps 4 - 9 above. Repeating this step will produce a series of result sets for comparison.
3
Experiment Data Sheet: g= π = r= ρ =
m/s2 m kg/m3
Flow rate Measurement Data: V1 (L)
T1 (MIN)
T2 (MIN)
4
Q (LPM)
Q (m3/s)
m1 (g)
m2 (g)
Fb1 (N)
Fb2 (N)
Fb (N)
N1 (rpm)
N2 (rpm)
N (rpm)
N (Hz)
Q (m3/s)
Fb (N)
N (Hz)
P1 (bar)
Hi (m)
Ph (W)
T (Nm)
Pb (W)
Et (%)
5
Result analysis: Formula Used: 1. Hi =
P1 ρ ×g
Ph= ρ × g× Hi× Q
2.
3. T = Fb× r 4. Pb = 2 × π × N× T 5. Et =
Pb ×100% Ph
Experiment 1: Turbine Characteristics g π r ρ
= = = =
9.81 3.142 0.04 1000
m/s2 m kg/m3
Flow rate Measurement Data: V1 (L) 10
T1 (MIN) 0.278
T2 (MIN) 0.282
Q (LPM) 35.7
Q (m3/s) 5.96E-04
Referring to the partial immerged data (1st data)
Volumetric Flow rate, Q
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Q= =
V1 TAVG 10 L ( 0.278 + 0.282 ) min
2
= 35.7 LPM 35.7 L 1 m 3 1 min = × × min 1000 L 60 s = 5.96 E − 04 m 3 / s
m1 (g) 40
m2 (g) 0
Fb1 (N) 0.3924
Fb2 (N) 0.0000
Fb (N) 0.3924
Brake Force, Fb Fb = Fb1 − Fb2 = ( m1× g ) − ( m2 × g )
(
) (
= 0.04 kg × 9.81 m / s 2 − 0.00 kg × 9.81 m / s 2 = 0.3924 N
Turbine Rotational Speed, N
7
)
N1 (rpm) 2121.0
N2 (rpm) 2124.0
N (rpm) 2122.5
N (Hz) 35.38
N1 + N 2 2 2121 + 2124 = rpm 2 = 2122.5 rpm 2122.5 rev 1 min 1 Hz = × × min 60 s 1 / s = 35.38 Hz
N =
Q (m3/s) 5.96E-04
Fb (N) 0.3924
N (Hz) 35.38
P1 (kgf/cm2) 1.50
Hi (m) 14.99
Ph (W) 87.6
Input Head to Turbine, Hi P1 ρ×g 1.5 × 98066 .5 Pa = 1000 kg / m 3 × 9.81 m / s 2 = 14.99 m
Hi =
Hydraulic Power at Input, Ph Ph = ρ × g × Hi × Q = 1000 kg / m 3 × 9.81 m / s 2 ×14.99m × 5.96 E − 04 m 3 / s = 87.6 W Torque, T T = Fb × r = 0.3924 N × 0.04 m = 0.0157 Nm
8
T (Nm) 0.0157
Pb (W) 3.49
Et (%) 3.98
Brake Power, Pb Pb = 2 × π × N × T = 2 × 3.142 × 35.38 Hz × 0.0157 Nm = 3.49 W Turbine Efficiency, Et Pb ×100% Ph 3.49 W = ×100% 87.6 W = 3.98%
Et =
9
10
