Explanation:
Specific speed: It is defined as the speed of a similar turbine working under a head of 1 m to produce a power output of 1 kW. The specific speed is useful to compare the performance of the various type of turbines. The specific speed differs for the different type of turbines and is the same for the model and actual turbine.
Option 1: Correct as the relation below is valid for both impulse as well as reaction turbines.
Option 2: Correct as the value of specific speed demands on the system of units
\({N_s} = \frac{{N\sqrt P }}{{{H^{\frac{5}{4}}}}}\)
From the above expression, the specific speed of a hydropower station depends on
Important Points
Option 3: Correct as Kaplan turbine has maximum specific speed. So, for any system of units, the value of specific speed will be lower than that for Kaplan turbine.
Following are the range of specific speeds of different turbines
Option 4: Incorrect
Specific speed |
Dimensional Formula |
Unit (SI) |
N_{s(turbine)} |
M^{1/2}T^{-5/2}L^{-1/4} |
Kg^{1/2}/s^{5/2}m^{1/4} |
N_{s(Pump)} |
L^{3/4}T^{-3/2} |
M^{3/4}/s^{3/2} |