The document discusses specific speed, which is a metric used to compare different types of turbines. Specific speed is defined as the speed of a geometrically similar turbine that produces 1 unit of power under 1 unit of head. The specific speed ranges are provided for common turbine types: Pelton wheel turbines have a specific speed of 80-50, Francis turbines range from 50-250, and Kaplan turbines have the highest specific speed range of 250-850. Specific speed is one factor used to select the appropriate turbine type for installation based on factors like head, part load operations, number of units, cost, and more. Turbines are also classified as having high, medium, or low specific speeds based on these defined ranges.

1. SPECIFIC
SPEED
CREATED BY : RITU GOSWAMI
ROLL NO : 18545
DEPARTMENT : APPLIED SCIENCE (IT)

2. WHAT IS SPECIFIC SPEED ?
– Specific speed of a turbine is defined as the speed of a geometrically similar
turbine which produce a unit power when working under a unit head.
– By geometrically similar means that turbine is identical in shape, dimensions,
blade angles and gate opening etc. it is denoted by the symbol Ns. The specific
speed is used in comparing the different type of turbines as every of turbine has
different specific speed.

3. SPECIFIC SPEED
SR. NO. TYPES OF TURBINE SPECIFIC SPEED
1. Pelton wheel with single jet(nozzle) 80-30
2. Pelton wheel with multiple jet(nozzle) 30-50
3. Francis turbine 50-250
4. Kaplan turbine 250-850

4. SELECTION OF TURBINE
– 1. HEAD
– 2. SPECIFIC SPEED
– 3. PART LOAD OPERATIONS
– 4. NUMBER OF UNITS
– 5. CAVITATION
– 6. POSITION OF TURBINE SHAFT
– 7. COST

5. SELECTION OF TURBINE ON
THE BASIS OF SPECIFIC SPEED
– The specific speed of a pump is defined as the speed of geometrically similar
pump that delivers units discharge under units head.
– Thus the specific speed , Ns is given as Ns = N√Q/H3/4
– Where N is the speed of the pump in r.p.m
– Q is discharge in m3/s and H is head in meters.

6. CLASSIFICATION OF HYDRAULIC
TURBINES.
ACCORDING TO THE SPECIFIC SPEED
– According to the specific speed, turbines may be classified as:
– (a) high specific speed turbine
– (b) medium specific speed turbine
– (c) low specific speed of a turbine

7. HIGH SPECIFIC SPEED TURBINE.
– Specific speed of these turbines are 250 to 850. so these are
called as high specific speed turbines. Kaplan and propeller
turbine are the examples of high specific speed turbines.

9. MEDIUM SPECIFIC SPEED TURBINE.
– Specific speed of these turbines are 50 to 250 . So these
are called medium specific speed turbine. Francis
turbine turbine is the example of medium specific speed
turbine.

10. Francis turbine

11. LOW SPECIFIC SPEED TURBINE
– Specific speed of these turbines are 8 to 30 with single
nozzle and up to 50 with nozzles. So these are called low
specific speed turbines. Pelton turbine is the example of
low specific speed.

12. Pelton turbine

13. Table gives the values of specific speed of
different types of pump.
Specific speed of centrifugal pump
SR. NO. PUMP SPEED SPECIFIC SPEED
1. Radial flow Slow
Medium
High
10-30
30-50
50-80
2. Mixed flow 80-160
3. Axial flow 160-425

14. THANK YOU

15. REFERENCES
– https://en.wikipedia.org/wiki/Specific_speed
– www.engineeringtoolbox.com/specific-speed-pump-fan-d_637.html
– Basics of mechanical engineering by vineet jain