Upload
long
View
71
Download
2
Tags:
Embed Size (px)
DESCRIPTION
Radial Pump Impeller Design (Example). Design a rotor(impeller) of a radial water pump for the following given values Q = 300 m 3 /h (0.0833 m 3 /s) H = 50 m n = 1450 rpm. The Specific speed for the pump is calculated from the following formula for the given values - PowerPoint PPT Presentation
Citation preview
1
Radial Pump Impeller Design (Example)
2
• Design a rotor(impeller) of a radial water pump for the following given values
Q = 300 m3/h (0.0833 m3/s)H = 50 mn = 1450 rpm
3
• The Specific speed for the pump is calculated from the following formula for the given values
• After finding the specific speed the shape of the impeller can be decided using the following table.
The specific speed is in the radial type pump range
3.2250
0833.014504343
HQn
ns
Shape No. Range Shape of the Impeller
10<ns<50 Radial Type
50<ns<150 Mixed Type
150<Ns<400 Axial Type
4
• The shaft Power is given as:
• The overall efficiency, ηo, for a single stage, single entry, radial pump can be read from the figure below to be ηo = 0.85.
• The pump power becomes,
o
QgHP
kWkWP 551.5185.0
5081.90833.0103
5
(Source: Centrifugal Pumps, Johann Friedrich Gülich, 2nd ed)
6
• Shaft diameter can be found using the following formula
• The torque can be calculated as it follows:
• The allowable shear stress for most of the shafts is in the range between 40 -60 N/mm2. Thus the shaft diameter becomes:
• The hub diameter, dh = 1.1 to 1.3 ds
316
ts
Td
Nmn
PPT 3626014502
550002
mmdsaymmd ss 40,64.3513.32
mmdd sh 502.1
7
• The eye diameter (D1) can be calculated by assuming inlet number . The radial velocity at the inlet is given by:
• The volume flow rate at the suction end is given by:
• Calculating for the eye diameter,
• The volumetric efficiency is given by:
YCom 2
V
homQQWheredDCQ
',
4' 22
1
965.0,,0362.1,3.22
287.01,287.0113232 V
sV
orn
21
4h
Vom
dCQD
8
• The inlet number can be found from the following table.
Guidelines to choose ε
9
• From the table,
• Thus,
• Another option to estimate the value of inlet number is to use the formula by Pfleiderer,
• Thus, D1 becomes,
3.22,13.008.0 snfor
smsmCom /4/52.75.2
32
210).35.1( sn
mmD 175.0173.005.0965.04
0833.04 21
10
The outer diameter D2 can be calculated using:1) The head coefficient (ψ)
The head coefficient for different type of pumps is given below.
222UgH
ψ Pump Type0.7-1.3 Radial Impeller
0.25-0.7 Mixed-flow impeller0.1-0.4 Axial Impeller
gHnDU 2
602
2
gH
nD 260
2
11
• Choosing ψ = 1,
2) The specific diameter (δ)
The specific diameter becomes,
mDandsmU
412.0,/32.31
2
2
21
41
nDQ
DnDQ
AUQ
UC
DnY
UgH
m322
22222
4
4
22
2/1
4/12
2/1
32
4/1
22221
41 05.142Q
YDnD
QDnY
12
• D2 becomes,
• The specific diameter is plotted in the following diagram for various specific speeds,
• From the table, δ = 6.5.
• Thus the outer diameter can be taken to be
D2 = 0.4m
4/122/05.1 QgH
D
mD 397.00833.0/5081.905.1
5.64/122
13Cordier Diagram
14
• Blade width b1
• The Blade width at the outlet b2
• C2m can be found from figure below.
mmm
CDQ
CDQb
omVom
40039.04175.0965.0
0833.0
'
111
mVm CDQ
CDQb
22222
'
smCfigurethefromkgHkC
m
mmm
/45.3,11.0,2
2
222
mmmb 200199.045.34.0965.0
0833.02
15
16
• Blade angle β0
• Blade angle β2 can be estimated from the previous figure.
• Number of blades
o
omom
nDC
UC
75.1660/1450175.0
4tan
tantan
1
1
1
1
10
oo to 3.238.21
43.04.0tan
2
2
approachStepanoffZ ,73
2
6
7,2
sin 21
12
21
Z
kofvaluethetakingDDDDkZ