Rotodynamic machines

Question 1

What is a rotodynamic machine

Answer 1

Machine having a rotating part called impeller or rotor through which fluid flows freely

Question 2

What two forms does energy exist in rotodynamic machines

Answer 2

Hydraulic and mechanical

Question 3

What is hydraulic energy

Answer 3

energy possessed by a fluid

Question 4

Mechanical energy consists of what two types of energy

Answer 4

kinetic energy and potential energy

Question 5

what two ways do rotodynamic machines transfer energy

Answer 5

Mechanical to hydraulic and hydraulic to mechanical

Question 6

are gasses highly compressible

Answer 6

yes

Question 7

3 applications of compressible flow

Answer 7

natural gas flow in pipes for heating, steam turbine and flow of gas in exhaust system

Question 8

what are the four variables flow field are described by

Answer 8

velocity vector, pressure, density and temperature

Question 9

what is cp

Answer 9

specific heat at constant pressure

Question 10

what is cv

Answer 10

specific heat at constant volume

Question 11

what is specific heat

Answer 11

the amount of energy needed to raise the temperature of 1kg of a substance by 1 degree

Question 12

what are the four equations needed

Answer 12

continuity equation, mass conservation, momentum and energy

Question 13

equation for mach number

Answer 13

gas velocity over speed of sound V/C

Question 14

how to increase velocity of a supersonic flow?

Answer 14

increase the area

Question 15

how do you obtain a supersonic flow

Answer 15

a converging diverging nozzle or a supersonic nozzle is needed.

Question 16

what is flow regime 1?

Answer 16

no flow in the nozzle and the pressure distribution is uniform (PB=PO)

Question 17

flow regime 2?

Answer 17

as back pressure is decreased, the flow commences. subsonic flow everywhere

Question 18

flow regime 3?

Answer 18

subsonic flow continues till pb is reduced to critical pressure. mass flow rate teaches a maximum value and flow is choked

Question 19

flow regime 4?

Answer 19

pb<p></p>

Question 20

how does fluid flow in axial flow machine?

Answer 20

along the axis of rotation

Question 21

how does fluid flow in centrifugal or radial flow machines

Answer 21

enters the rotor axially and flows in a radial direction

Question 22

how does fluid flow in a mixed flow machine

Answer 22

combine features of axial and centrifugal machines.

Question 23

two important fluid variables?

Answer 23

flow rate and heat

Question 24

mechanical variables associated?

Answer 24

speed, power transfer between fluid and impeller, size and efficiency

Question 25

losses for pumps?

Answer 25

by energy balance

Question 26

how can performance problems be solved for testing roto machines

Answer 26

using dimensionless groups and similarity laws

Question 27

two types of turbines

Answer 27

impulse and reaction

Question 28

impulse turbine?

Answer 28

uses hydraulic energy of water to move the impeller

Question 29

reaction turbine?

Answer 29

develops power from the combined action of pressure and moving water

Question 30

what is cavitation

Answer 30

formation of bubbles of a flowing liquid where the pressure of liquid falls below its vapor pressure

Question 31

what causes cavitation

Answer 31

low pressure boiling, gas release

Question 32

effect of cavitation

Answer 32

erosion damage

Question 33

what is an extended surface

Answer 33

An extended surface is a solid which transfers heat by conduction within its boundaries and by convection and/or radiation between its boundaries

Question 34

what is fin performance

Answer 34

Fin performance is the ratio of the fin heat transfer rate to the heat transfer rate that would exist without the fin

Question 35

biot number

Answer 35

The Biot number, Bi, is a dimensionless number used in non-steady state (transient) heat transfer calculations. It gives a simple index of the ratio of the heat transfer resistances inside of and at the surface of a body

Question 36

fourier number

Answer 36

The Fourier number, Fo, is a dimensionless number that characterizes heat conduction. It is the ratio of the heat conduction rate to the rate of thermal energy storage

Question 37

nusselt number

Answer 37

The Nusselt number, Nu, is the ratio of convective to conductive heat transfer across boundary