4th lab 2013
Transcript of 4th lab 2013
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8/17/2019 4th lab 2013
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Mechanical Engineering Lab
Hydraulics
4th
Year
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Centrifugal Pump Characteristics
Objectives
It is required to study the performance of a centrifugal pump at different speeds.
Experimental procedure
1. The pump is operated at a certain speed (N).
2. The discharge of the pump is changed using a gate valve installed on the delivery side.
3.
Adjust the speed (N) for each case.
4. For different discharges, the following readings are taken.
Manometric suction head (Hms) by using a pressure gauge, ft.
Manometric delivery head (Hmd) by using a pressure gauge, ft.
U-tube manometer reading (y), cm.
Force (F) by using weights, kgf .
Calculations
1. Pump manometric Head:
Hm = Hmd - Hms
2. Discharge:
1
222
f
u
throat p ipe
throat p iped
yh
gh A A A AC Q
Where,
Cd = 0.94
d pipe = 10 cm
dthroat = 6.86 cm
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
y = U-tube manometer reading
u = 13.6
f = 1
3. Efficiency:
η = (O/P) / (I/P)
Where,
O/P = water x Hm x Q
I/P = T x ω
T = F x R
ω = 2π N / 60
Hint: R (brake radius) = 0.3048 m.
Results and Discussion
1)
Draw a schematic diagram for the system.
2) Plot the relation between:
The pump discharge (Q) and the pump manometric head (Hm).
The pump discharge (Q) and the pump efficiency (η).
The pump discharge (Q) and the pump input power (I/P).
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Observations
N1 = rpm
y (cm) Hms (ft) Hmd (ft) F (Kgf ) T = F * R (N.m) I/P (Watt)
h (m) Q (lit/s) Hm (m) = Hmd - Hms O/P (Watt) η
N2 = rpm
y (cm) Hms (ft) Hmd (ft) F (Kgf ) T = F * R (N.m) I/P (Watt)
h (m) Q (lit/s) Hm (m) = Hmd - Hms O/P (Watt) η
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Pelton Wheel Characteristics
Objectives
It is required to study the performance of a Pelton Wheel (turbine) and plot the relation
between the specific speed (Ns) and the mechanical efficiency (η).
Experimental procedure
1. At no flow; read the balance zero reading at the zero position.
2. Start the pump, fully open both the pump discharge valve and the turbine needle valve
then operate the pump at a certain speed.
3. Get the mercury U-tube reading (y) and the turbine inlet head (H).
4. Adjust the turbine brake, load, to get a certain turbine speed (N).
5.
At this speed; use masses and screw to restore original zero position and take the balance
reading.
6. Repeat steps 4 and 5 at different turbine speeds and loads.
Calculations
1. Discharge:
1
222
f
u
throat p ipe
throat p ipe
d
yh
gh A A
A AC Q
Where,
Cd = 0.94
d pipe = 10 cm
dthroat = 6.86 cm
y = U-tube manometer reading
u = 13.6
f = 1
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
2.
Brake force:
F = Counter balance masses + zero reading – balance reading
Where, the "Counter balance masses" are the masses added to ensure a net tension force on
the balance.
3. Efficiency:
η = (O/P) / (I/P)
Where,
I/P = water x H x Q
O/P = T x ω
T = F x R
ω = 2π N / 60
Hint: R (brake radius) = 0.46 m.
4. Specific speed:
Where; O/P in kw.
Results and Discussion
Plot the relation between the specific speed (Ns) and efficiency (η) for the Pelton Wheel
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Observations
Balance zero reading = (kgf )
Counter balance masses (kg ) y (cm) H (ft) N (rpm) Balance reading (kgf )
Q (m3/s) I/P (watt) F (N) ω (rad/s) T (N.m) O/P (watt) Ns(SI units) η (%)
7.3
6.9
5
3.7
1040
1000
960
900
6
6
6
6
4
74
74
74
74
f
3.5
3.5
3.5
3.5
F (N
1.9
5.8
24
37
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Forced Vortex
Objectives
It is required to study the pressure distribution on the bottom of a tank filled with liquid and
subjected to forced vortex at different rotational speeds.
Experimental Procedure
1. Turn on the motor switch.
2. Adjust the speed regulator at certain rotational speed.
3.
Wait for steady flow (piezometers readings remain constant).
4. List down the readings of the 12 piezometer tubes.
5. Change the rotational speed.
6.
List down the readings of the 12 piezometer tubes at the new speed.
Observations
Tube No.Piezometer tube reading (cm)
N1 (rpm) = … N2 (rpm) = …
1
2
3
4
5
6
78
9
10
11
12
Results and Discussion
Draw the distribution of the pressure head on the tank bottom at the two speeds N 1 and N2
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Secondary Losses in Bends and Fittings
Objectives
It is required to demonstrate the secondary losses through different types of bends and fittings.
Experimental Procedure
1.
Close the regulation valve and start the centrifugal pump.
2. Open the valve partially.
3. Wait for steady flow (Piezometers readings = constant).
4.
Read the differential readings of the Piezometers connected to the mitre, the elbow, the
short bend, the enlargement and the contraction.
5. Read the initial volume in the collection tank V1.
6.
Observe the time (t) to increase the collected volume to V2.
7. Increase the valve opening.
8. Repeat the experiment two times.
9. After recording all the required readings, close the valve gradually then stop the
centrifugal pump.
Notes:Pipe area : 301.7 mm2
Enlargement pipe diameter : 26.2 mm
Contraction pipe diameter: 19.48 mm
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Observations
Experiment No. 1 Experiment No. 2
Type of fittingh
(mm)
V1(lit.)
V2(lit.)
t
(Sec.)h
(mm)
V1(lit.)
V2(lit.)
t
(Sec.)
Mitre
Elbow
Short bend
Enlargement
Contraction
Calculations
)tEnlargemen(22
)-(
K=h
)nContractio(22
K=h
) bendShort&ElbowMitre,(2
K=h
t
VVQ
2
1
2
2
2
21
2
1
2
2
2
2
2
12act
g g
g g
g
Where,
v1 = upstream velocity
v2 = downstream velocity
Results and Discussions
List down the value of the coefficient of loss (K) for each type of fitting.
Comment on the results.
K (Exp. No. 1) K (Exp. No. 2) K av
Mitre
Elbow
Short bend
Enlargement
Contraction
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Performance of a Pressure Relief Valve
Objectives
It is required to study the performance of a direct-acting pressure relief valve.
Experimental Procedure
1)
Close the throttle valve completely then, unload the pressure relief valve.
2)
Set the pressure relief valve approximately to 50 bar then, open the throttle valve
completely.
3) Close the throttle valve in several steps, measure and note down the system pressure and
the flow rate through the pressure relief valve.
Observations
Throttle valve Open Closed
Psystem (bar)
Qrelief (l/min) Zero
Results and Discussions
1) Describe the operation of the circuit.
2) Plot the pressure-flow relationship for the pressure relief valve.
3)
List down all components used in the circuit.
4) Draw the hydraulic circuit diagram.
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Alexandria University
Facul ty o f Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Regenerative Circuit Characteristics
Objectives
It is required to study the behavior of a regenerative circuit and to compare it with that of a
normal circuit.
Experimental Procedure
1)
Using the 4/2 DCV as a 3/2 DCV (by plugging one of its ports), extend the double-acting
cylinder and notice the extension speed and the pressures upstream and downstream the
cylinder.
2)
Using the 4/2 DCV normally, extend the double-acting cylinder and notice the extension
speed and the pressures upstream and downstream the cylinder.
Observations
Pupstream (bar) Pdownstream (bar) Extension Time
Regenerative circuit
Normal circuit
Results and Discussions
1) Describe the operation of the circuit.
2) Compare the extension parameters (extension time, force) for the regenerative and the
normal circuits.
3) List down all components used in the circuit.
4) Draw the hydraulic circuit diagram for both the regenerative and the normal circuits.
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Alexandria University
Facul ty of Engineer ing
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Control of a Double Acting Cylinder in a Pneumatic System
Objectives
It is required to study how to connect a pneumatic circuit to perform extension and retraction
of a double-acting cylinder.
Experimental Procedure
Use the 3/2 Push- button DCV’s to actuate the 5/2 pilot operated DCV which controls the
extension and retraction of the double-acting cylinder.
Observations
Notice how the air is transmitted through the pneumatic lines from the air source to the
cylinder through the directional control valves to perform the extension and the retraction of
the double acting cylinder.
Results and Discussions
1) Describe the operation of the circuit.
2) List down all components used in the circuit.
3) Draw the pneumatic circuit diagram.
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Alexandria UniversityFaculty of Engin eering
Mechanical Engineering Department
Hydraul ics Lab ( 4th
year )
Speed Control for a Position-Dependant Double Acting
Cylinder
Objectives
It is required to study how to connect a pneumatic circuit to perform controlled speed
piston extension and retraction functional sequence for a double-acting cylinder.
Experimental Procedure
Use the 3/2 Push-button DCV to actuate the 5/2 pilot operated DCV which controls the
extension and retraction of the double acting cylinder through two mechanical actuated
3/2 DCV’s. Notice the extension and retraction strokes and how they are controlled.
Observations
Notice how the air is transmitted through the pneumatic lines from the air source to the
cylinder through the directional control valves to perform successive extension and
retraction of the double acting cylinder.
Results and Discussions
1) Describe the operation of the circuit.
2) List down all components used in the circuit.
3)
Draw the pneumatic circuit diagram.