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Matching of Machine with Resource/Demand
P M V SubbaraoProfessor
Mechanical Engineering Department
A Response time Based Parameter….
Machine-Fluid Matching Parameter:
:, pQf
For compressible power consuming fluid machines
4
3
p
QT f
For incompressible power consuming fluid machines
4 3gH
QT f
Selection of Speed of A Turbo Machine
The impact of Nationalism…….
Importance of Specific Speed
A pump with a given flow geometry and momentum transfer principle
Selection of Geometry Vs Specific Speed
Specific Speed
Speed Vs Size : Constant Head & Flow Rate
N=1000 rpmN=1500 rpm
N=3000 rpm
Demand Speed nf = 492 rps
Matching of a Hydraulic Turbine to a hydraulic Resource
Speed: N (rpm) or n (rps)
Scale Time Machine
Scale Time Resourcescale timeessDimensionl
n
T f
1scale timeDimension -Non
This is named as Specific Speed, Ns
4 5gH
Pn
N s
4 5gH
P
T f
,:, gHPfGI
4 5
60
gH
PN
N s
Popular Definitions for Hydraulic Machines
4 5gH
PN
N s
43
45
H
QNor
H
PNN s
The specific speed, usually represented by Ns, also denominated absolute specific speed or specific angular speed.
Specific Speed
Blade Geometry Vs Characteristic of Resource
The Pelton Wheel : Pure Impulse Turbine
Mic
ro c
lass
ific
atio
n B
ased
on
Spe
cifi
c S
peed
MORE ADAPTED TYPE OF TURBINA IN FUNCTION OF THE SPECIFIC SPEED.
Specific Speed in r.p.m. Turbine type Jump height in m
Until 18 Pelton of an injector 800
From 18 to 25 Pelton of an injector 800 to 400
From 26 to 35 Pelton of an injector 400 to 100
From 26 to 35 Pelton of two injectors 800 to 400
From 36 to 50 Pelton of two injectors 400 to 100
From 51 to 72 Pelton of four injectors 400 to 100
From 55 to 70 Very slow Francis 400 to 200
From 70 to 120 Slow Francis 200 to 100
From 120 to 200 Normal Francis 100 to 50
From 200 to 300 Quick Francis 50 to 25
From 300 to 450 Extra-quick Francis 25 to 15
From 400 to 500 Extra-quick helix 15
From 270 to 500 Slow Kaplan 50 to 15
From 500 to 800 Quick Kaplan 15 to 5
From 800 to 1100 Extra-quick Kaplan Less than 5
45
H
PNN s P in hp & H in meters
Further Utility of Specific Speed in Hydro-power Industry
• Every nation has a public sector organization to identify and quantify the hydro resources. (NHPC in India)
• This organization will also announce the developmental plans.
• The data will be made available on public domain.
• Turbine manufactures will collect the data and develop a suitable turbine design with highest possible efficiency.
• Every industry will have in house testing facility to experimentally test the design and show performance guarantee.!!!!!
Sharavathi Catchment Area
Jog Falls
Sharavati Generating Station
• Capacity:1035 MW.
• Head available: 443 m
• Site Specific Speed: 0.776×N rpm
Selection of Turbine
Wheel Specific Speed (rpm)Pelton 10 – 30Turgo 20 – 70Crossflow 20 – 200Francis 30 – 400Propeller and Kaplan 200 - 1000
Hydro-power Manufacturing Industry
• Turbine manufactures will collect the data and develop a suitable turbine design with highest possible efficiency.
• Every industry will have in house testing facility to experimentally test the design and show performance guarantee.!!!!!
How to Simulate a Natural Resource in the Laboratory?
• Compute specific speed of the resource, with a suitable machine speed as:
43
45
H
QNor
H
PNN s
Redefine specific speed as, the speed of a turbine similar to which you want to propose would give (of equal form but reduced dimensions), which, installed in a fall of 1 m height, would provide a power of 1 hp
DIMENSIONAL ANALYSIS
•Scale model to prototype design and analysis.•Used to select proper turbo-machine (axial, radial or mixed flow,…)•Used to define performance parameters