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