Centrifugal pump design 2022
Centrifugal pump design
The Centrifugal pump design assignment is worth 30% of the turbomachinery II module.
The due date for submission is Wednesday, 30th May 2022, 14:00:00 Beirut Time.
You must work individually on this assignment and the answers should be presented in
a report format with references. .
Please submit your answers, including a cover page, in one single pdf file.
Learning outcomes
1- Gained practice in pump design and presentation of design data in a report.
2- Developed project management skills within a project timeline.
Tasks
i) Project management
1- Project scoping form covering both the design task and the drawing tasks:
2- Work Breakdown Structure.
3- Gantt Chart
ii) Centrifugal pump impeller design task
1- Design description a centrifugal pump impeller (using mixed) for the technical data
and individual design specifications given in this brief.
.
iii) Drawing Task
1- Blade profiling in two planes.
2- Scroll case design and drawing
Structure of the report
The order of what you submit is important. (page numbers approximate)
i) Project management (2 pages)
Project scoping form, Work Breakdown structure, Gantt chart…
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Centrifugal pump design 2022
Clearly show how you planned your work, who did what and date/time clearly shown
with final submission as the last step.
ii) Impeller design calculations (10-12 pages)
Introduce your design, and then present your calculations clearly and systematically. All
calculations should be easy to follow and put the findings in context to the report.
iii) A clear sketch of the impeller + key design findings (1 page)
Figure need not be to scale but if too cluttered add sizes, blade numbers and other
design parameters in a related text box.
iv) Data sheet (1 page)
Clear summary set out neatly on a single sheet of A4 paper and include:
1- Data for velocities, flow rates, heads, efficiencies, slip factor, reduction coefficient
2- The obtained design facts such as number of blades, blade and flow angles, impeller
diameters and blade parameters (width, thickness, material). Use the structure of the
Data Sheet found in this brief, where a typical centrifugal pump impeller Data Sheet can
be found in pumps catalogues
v) Profiling of blades and design, drawing of scroll case (3 pages)
.
vi) Conclusion and critical review (max. 1 page)
Conclude all your report tasks
vii) References
Use Harvard system and list the references that you used in your design and
calculations
Recommended references …:
Do not use Wikipedia (or simple Google search) as a reference
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Centrifugal pump design 2022
Given
Parameter
3
Q m /s
Hm
ω 1/s
Variants
0
0.02
15
300
1
0,025
17
290
2
0.028
19
280
3
0.03
21
270
4
0.035
23
260
5
0.04
25
250
6
0.042
27
200
7
0.045
29
180
8
0.047
31
160
9
0.055
33
150
The last two digits of the student ID number
Last digit for Q
Preceding digit for H
Absolute value of the difference between the two digits for ω
Example: 39
Q = 0.055 m3/s; H = 19 m, ω = 200 1/s
A- Centrifugal pump impeller design procedure
1- Qs = Q/i = Q; I = 1; number of entry
2- Hs = H/j = H; j = 1; number of stages
3- ns = 3.65 x n x √Q / H3/4
rpm
4- Impeller normalized diameter D1 norm = √(D12 – Dhub2) = (4 - 4.5) (Qs / n)1/3 m
5- Hydraulic efficiency ηh = 1- [0.42 / (Log D1 norm – 0.172)2]; D1 norm in mm
6- EN = Hth = Hs / ηh
m
7- Volumetric efficiency ηv = 1 / [1 + 0.68 x ns-2/3]
8- Flow through the impeller Qi = Qs / ηv m3/s
9- At first estimation, the allowable fluid velocity at the entry (eye):
C0 = (0.06 – 0.08) (Qi x n2)1/3 m/s
10- Mechanical efficiency ηm = ηm int – (0.010.- 0.03) = 96 – 0.9
ηm int = (2 x Cf / 1000) x ρ x ω3 x R24 x (R2 + 5 Lcylinder);
Cf = C0f + ΔCf; Cf – Disc friction coefficient
11- Overall efficiency ηo = ηh x ηv x ηm
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Centrifugal pump design 2022
12- Shaft / mechanical Power Pm = (ρ g Q H) / (1000 x ηo)
13- Required power Preq. = FS x Pm
kW
kW
Factor of safety
FS = 1.05 – 1.3
FS = 1.03
Mechanical power
Pm = (1 – 50) kW
Pm > 50 kW
‘
14- Maximum shaft torsional moment Mmax = Preq. / ω
N.m
15- Pump shaft diameter dshaft = (Mmax / 0,2 x [τ])1/3 m;
[τ] = (15 – 20) MPa
16 – Sleeve / hub diameter dhub = (1.2 - .25) dshaft
m
17- Entry / eye diameter D0 = √(4Qi/πC0 +dhub2) m
18- Impeller tangential velocity at D1; U1 = π D1 n / 60
Specific speed rpm
ns = 90 - 300
ns = 30 - 90
m/s
Impeller diameter D1
D1 = (0.8 – 0.9) D0
D1 = (1.03 – 1.05) D0
19- Fluid velocity at the entry / eye C0 = 4 Qi / [π (D02 – dhub2]
20- Meridian velocity at D1; C’m1 = C0
m/s
m/s
21- Meridian velocity at D1 Cm 1 = K1 C’m1; K1 = 1.05 – 1.015
22- Shock free flow angle β’1 = arc tang (Cm1 / U1)
22’- blade angle β1 = β’1 + i
i = 3 - 10⁰ - angle of attack
Usually β1 = 17 - 25⁰
23- Inlet blade width b1 = Qi / (π D1 C’m1)
m
24- Impeller head coefficient Ψ = CU2 / U2 = (1.87 – 2) ns-0.28
25- Impeller tangential velocity at D2; U2 = √(g Hth / Ψ)
26- Impeller diameter D2 = 2 U2 / ω
m
m
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Centrifugal pump design 2022
27- Coefficient of area reduction K2 = (1.05 – 1.1)
28- Meridian velocity C’m2;
C0 / 2 ≤ C’m2 ≤ C0
m/s
29- W 1/W 2
ns
W1/W 2
40
2.1
50
1.75
60
1.6
70
1.45
80
1.3
90
1.2
100
1.1
120
1.1
150
1
200
1
30- Blade angle β2 = arc sin (W 1/W 2 x K2/K1 x C’m2 / C’m1 x sin β1)
31- Number of blades Z = 6.5 [(D2 + D1) / (D2 – D1)] sin [(β1 + β2) / 2]
32- E = Hth.∞ = (1 + p) Hth
m
p = 2 ϕ / [Z (1 – (D1/D2)2)]
ϕ = (0.55 – 0.65) + 0.6 sin β2; higher values of ϕ for higher values of ns
33- Meridian velocity Cm2 = K2 C’m2
m/s
34- Second estimation for U2 = 0.5 [(Cm2 / tg β2) + √((Cm2 / tg β2)2 + 4 g E)]
35- Impeller outlet diameter D2 = 2 U2 / ω
36- Outlet blade width b2 = Qi / (π D2 C’m2); Check if b2 = 0.07 D2 (ns/100)4/3
37- Blade thickness
Steel blades
Cast iron blades
Freza I chtampovani blade
t1 = t2 = (3 – 6) mm
t1 = t2 = (4 – 9) mm
t1 = t2 = (2 – 5) mm
38- Verification of area reduction coefficient K’2 = 1 / [1 – (Z t2) / (π D2 sin β2)]
Acceptable error Δ = (5- 10) %
If more, than take K2 = K’2 and repeat calculation from point 30
39- Verification of area reduction coefficient K’1 = 1 / [1 – (Z t1) / (π D1 sin β1)]
Acceptable error Δ = (5- 10) %
If more, than take K1 = K’1 and repeat calculation from point 21
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Centrifugal pump design 2022
40- Verification of relative velocity ratio
W’1 = K’1 C’m1 / sin β1
W’2 = K’2 C’m2 / sin β2
If W’1/W’2 and W 1/W 2 is more than 5-10 % then take W 1/W 2 = W’1/W’2 and repeat from
point 30
If the results diverge we recommend take different values for K1 and K2 and or different
values of other parameters such as t1 and t2
41- Construction of velocity triangles
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Centrifugal pump design 2022
Part B Blade profiling
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Centrifugal pump design 2022
Part C Volute / spiral case design and drawing
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