1. BASIC MECHANICAL ENGINEERING
UNIT-3
1)Hydraulic Pumps And Turbines
2)Refrigeration And Air Conditioning Systems

2. HYDRAULIC MACHINERY

3. Hydraulics Hydraulics deals with the mechanical properties of liquids.
Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties.
Hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids.
Pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion.

4. Topics Hydraulic pumps Hydraulic power plant layout Hydraulic Turbines
Reciprocating pump
Centrifugal pump
Hydraulic power plant layout
Hydraulic Turbines
Impulse
Reaction

5. Hydraulic Pump
Mechanical device which converts the mechanical energy into hydraulic energy.
Increase the pressure energy subsequently converted into potential energy.
A pump is a device which lifts water from a lower level to a higher level at the expense of mechanical energy.
Pump is a Power absorbing device.

6. Reciprocating Pump

9. As the crank moves outwards, the piston moves out creating suction in the cylinder.
Due to the suction water/fluid is drawn into the cylinder through the inlet valve.
The delivery valve will be closed during this outward stroke.
During the return stroke as the fluid is incompressible, pressure will developed immediately which opens the delivery valve and closes the inlet valve.
During the return stroke fluid will be pushed out of the cylinder against the delivery side pressure.

10. Centrifugal Pump

13. Energy is imparted to the fluid by centrifugal action of moving blades from the inner radius to the outer radius.
The main components of centrifugal pumps are
the impeller,
the casing
the drive shaft

14. The impeller consists of a disc (impeller) with blades mounted perpendicularly on its surface.
The casing is air tight and water tight and its cross sectional area gradually increases towards the outlet
The upper end of the suction pipe is connected to the eye of the impeller and other end to foot valve
The delivery pipe is connected to the outlet of the pump to deliver liquid to the required height with the help of delivery valve

15. Working
The fluid enters through the suction nozzle of the pump to the eye of the impeller.
The fluid is trapped between the blades of the impeller.
The impeller is spinning at the velocity of the driver.
As the fluid passes from the eye, through the blades toward the outside diameter of the impeller, the fluid undergoes a rapid and explosive increase in velocity

16. As velocity goes up, the pressure goes down, and indeed there is a low-pressure zone in the eye of the impeller
The liquid that leaves the outer diameter of the impeller immediately slams into the internal casing wall of the volute where it comes to an abrupt halt
As velocity goes down, the pressure increases
The velocity is now converted into head or pressure available at the discharge nozzle.

17. Priming
To start delivery of the fluid the suction pipe, casing, impeller and the delivery pipe up to delivery valve should be filled with the fluid without any air pockets. This is called priming.
In presence of air, negligible pressure is generated because of low density of air and hence no water will be lifted
Delivery valve is kept closed even after the casing is filled with water.
Then delivery valve is opened gradually to allow high velocity and high pressure water to push through the delivery pipe.

18. CENTRIFUGAL PUMP
RECIPROCATING PUMP
Large discharge and small heads
Small discharge and higher heads
Lifting of high viscous fluids like oils, paper pulp, chemicals
Can handle only pure water and less viscous fluids
Uniform and continuous flow
Flow is fluctuating and pulsating
Higher speed and hence coupled with motor
Runs at low speed hence gear driven

19. Needs priming
Priming not required
Quiet in operation
Noisy in operation
Maintenance is cheap
costly
Less wear and tear
More wear and tear
Occupies less space
4 to 6 times larger area
Efficiency is less
Efficiency is more

20. HYDRAULIC TURBINE
Hydraulic turbines are machines which convert hydraulic energy (energy of water ) into mechanical energy.
Thus in turbines fluid does work on the machine and machine produces power.
The mechanical energy developed by the electric generator which is directly coupled to the shaft of the turbine.
The electric power developed by the electric generator is known as hydro electric power. So the generation of hydro electric power is cheaper than the other sources like coal, oil, etc.

21. Hydro Power Plant Layout

23. Shaft Connecting Turbine & Generator

25. TUNGABHADRA 6 X 9 MW Kaplan, 2 X 9 MW Francis
SRISAILAM 6 X 165 MW Kaplan 6 X 110 MW Francis
TUNGABHADRA 6 X 9 MW Kaplan, 2 X 9 MW Francis
NAGARJUNA SAGAR 1 X 110, 7 X 100,8.
5 X 30 Francis

26. Hydraulic Turbines
Machines which convert hydraulic energy in to mechanical energy.
Fluid does work on the machines, produces power
Power developed is called hydro electric power
Principal component of turbine is rotor

27. Classification 1.Action of water
Impulse : There is no pressure drop on the runner/rotor. K.E of water coming from the jet is used to run the runner/rotor.
Ex: Pelton wheel turbine.
Reaction: There is a loss of K.E as well as pressure energy on the runners of the blade.
Ex: Francis turbine
2. Direction of flow of water
Tangential: In this flow the water strikes the runner tangential to the path of rotation.
Radial: In this flow the water enters the runners radially and comes out axially.
Axial: In this flow the water flows parallel to the axis of the turbine.
Ex: Kaplan turbine

28. Classification 3. Available head
High head: The turbine capable of working under high potential head of water above 250m
Ex: Pelton wheel turbine.
Medium head: The turbine is capable of working under medium range of potential head about 60m to 250m
Ex: Francis turbine.
Low head: The turbine is capable of working under low range of potential head greater than 60m
4. Specific speed:
Low speed: Turbine works in the range of (Ex: Pelton wheel turbine)
Medium speed: Turbine works in the range of (Ex: Francis turbine)
High speed: Turbine works in the range of (Ex: kaplan turbine)

29. Impulse turbine
The available energy of water is converted into kinetic energy by passing it through a nozzle at the end of the penstock
Water coming out of nozzle forms into free jet which impinges on a series of buckets of the runner, causing it to revolve
Water is in contact only with a part of the runner at a time
A casing is provided on the runner to prevent splashing and to guide the water discharged from the buckets to the tailrace

32. Reaction Turbine
At the entrance to the runner only a part of the available energy of water is converted into kinetic energy and a suitable part remains in the form of pressure energy
As the water flows through the runner the change from pressure to kinetic energy takes place gradually
For this gradual change in pressure to be possible the runner must be enclosed in a air tight casing
The difference of the pressure between the inlet and the outlet of the runner is called reaction pressure, hence reaction turbine.

34. IMPULSE
REACTION
Available energy is converted into kinetic energy
Major part of available energy is converted to pressure energy
Pressure in turbine is constant
Pressure gradually reduces while water flows on the turbine blades
The wheel and the blades should have accesses to free air and must not run full
The blades are always under the action of pressure, wheel must always run full
Only one face of blade is active
Both sides
Turbine must always be installed above water level in tail race
The turbine is usually set above the tailrace.

35. Regulation of flow and power is easier without loss of energy
Difficult
Used for high heads
Low and medium heads
Efficiency is less
Efficiency is more
Energy transfer being change in energy
Due to change in pressure head

36. PELTON WHEEL OR PELTON TURBINE

37. Runner consists of circular disk with a suitable number of double hemi ellipsoidal cups know as buckets evenly spaced round its periphery
One or more nozzles are mounted to direct a jet of water on the runner in tangential direction
The nozzle is fitted with a spear or needle fixed to the end of a rod
The impulse force produced due to this momentum of water causes the turbine to rotate
The double semi ellipsoidal buckets split the water jet in two half’s which helps in balancing the turbine.

38. FRANCIS TURBINE

43. Francis turbine is a radial inward flow turbine and is the most popularly used one in the medium head range of 60 to 300 m.
The main components are (i) The spiral casing (ii) Guide vanes (iii) Runner (iv) Draft tube
The spiral casing surrounds the runner completely
Its area of cross section decreases gradually around the circumference.
This leads to uniform distribution of water all along the circumference of the runner.
A draft tube is a large pipe with increasing cross section area which connects the runner exit to the tailrace

44. Water enters the runner through the guide blades along the circumference
The blade passages act as a nozzle in this aspect guiding the water at the proper direction
The area of blade passage is changed to vary the flow rate of water according to the load so that the speed can be maintained constant

45. The runner is circular disc and has the blades fixed on one side
The runner is circular disc and has the blades fixed on one side. In high speed runners in which the blades are longer a circular band may be used around the blades to keep them in position.
The runners change the direction and magnitude of the fluid velocity and in this process absorb the momentum from the fluid.

46. Guide vanes (yellow) at minimum flow low setting
CUT-WAY VIEW OF FRANCIS TURBINE :-
Guide vanes (yellow) at minimum flow low setting

47. Kaplan Turbine

48. Kaplan turbine

51. Main components are
Runner with runner blades
Scroll casing
Guide vanes
Draft tube
It is an axial flow turbine
Suitable for low head and large quantity of water
The inlet is trough the scroll casing which is in the form of the spiral
After entering in to the casing water gets distributed into the guide vanes
In guide vanes water turns through a right angle into axial direction

52. Water flows over the runner blades and losses their pressure energy to impart kinetic energy to the runner
Runner blades as well as guide vanes are adjustable
Finally water is discharged to the tail race through a gradually expanding tube called the draft tube

54. Hydraulic Machinery