turbomachines Chemical engineering is a branch of engineering that applies principles of chemistry, physics, mathematics, biology, and economics

chemical engineering Chemical engineering is a branch of engineering that applies principles of chemistry, physics, mathematics, biology, and economics

1. Turbines

2. A turbo-machine is a rotary machine , which always involves in an energy transfer between a continuously flowing fluid and a rotor . It is a power or head generating machine It uses the dynamic action of the rotor or impeller or runner which changes the energy level of the continuously flowing fluid through the rotor. The energy transfer occurs either from rotor to the flowing fluid or from working fluid to the rotor depending upon the type of machine.

3. Turbines Pumps , compressors, fans…

4. Based on the interaction with working fluid:   Power absorbing turbo machines: These turbo machines, also called fans or pumps, impart energy to the working fluid. They increase the pressure of the working fluid by their operation. They require mechanical work to be supplied to them for their operation. They are also called power consuming turbo machines.

5. These turbo machines, called turbines , absorb energy from the working fluid by way of exchange of momentum, and generate useful rotational mechanical work. The operation of such machines results in a reduction in the energy of the working fluid . Power generating turbo machine:

6. Principle components of a turbo-machine : A vane carrying rotating element called rotor or impeller or runner. A stationery element or elements. An input or/and output shaft. A housing

7. The working principle is: • When the fluid strikes the blades of the turbine, the blades are displaced , which produces rotational energy. • When the turbine shaft is directly coupled to an electric generator the mechanical energy is converted into electrical energy. Turbines the energy transfer is from the fluid to the rotor.

8. Classification of turbo machines based on type working medium When the working fluid is water turbines are called hydraulic turbines. When working fluid is air, and energy is extracted from the wind, the machine is called wind turbine. When the working fluid is steam, turbines are called steam turbines. Turbine that employs a compressible gas as the working fluid is gas turbine .

9. Wind Turbine device that converts kinetic energy from the wind into electrical power . Conventional horizontal axis turbines can be divided into three components:. • The rotor component , includes the blades for converting wind energy to low speed rotational energy . • The generator component, includes the electrical generator, the control electronics • The structural support component, includes the tower

10. Gas turbines are composed of three components : compressor, combustor and power turbine. In the compressor section, air is drawn in and compressed up to 30 times ambient pressure and directed to the combustor section where fuel is introduced, ignited and burned. The combustion generates a high-temperature flow.

11. Steam turbine a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Steam turbines are used for the generation of electricity in thermal power plants

12. Hydraulic turbine – A rotary engine that converts hydraulic energy into mechanical energy

13. Classification of the turbomachines by the stream direction in relation to the axis of the shaft

14. a )   Radial flow turbo machine : In these turbo machines, the working fluid flows radially across the turbine blades. It enters the blade at the inner or outer periphery of the blade, and moving radially, exits the blade at the other periphery. b)  Axial flow turbo machines : Fluid flows parallel to the rotational axis of the shaft of the fluid flows along the shaft. c)  Mixed flow turbo machines: In these turbo machines, the fluid enters the turbine radially, and exits axially, or vice versa . d) Tangential flow machines : fluid flows along the tangent of the runner

15. Axial flow turbine Flow is entering, parallel to the axis of the rotation of impeller or rotor.

16. The inlet is a scroll-shaped tube that wraps around the turbine's wicket gate. Water is directed tangentially through the wicket gate and spirals on to a propeller shaped runner, causing it to spin. Kaplan Turbine

17. Tangential Flow Turbine:  If the water flows along the tangent of the runner, the Turbine is known as tangential flow turbine. Pelton wheel

18. Radial flow turbines: In this type of turbine the water strikes in the radial direction. Inward flow turbine : The flow is inward from periphery to the center ( centripetal type). old Francis turbine. Outward flow turbine:  The flow is outward from the center to periphery (centrifugal type). Fourneyron turbine .

19. Mixed Flow Turbine:  If the water flows through the runner in the radial direction but leaves in the direction parallel to the axis of rotation of the runner, the turbine is called mixed flow turbine. Francis

20. a)  to  (d)  are pumps, compressors or fans;  (e)  to  (j)  are turbines.  (a)  axial – flow;  (b)  radial – with axial inlet;  (c)  mixed – flow;  (d)  radial – flow (centrifugal);  (e)  axial – flow;  (f)  radial – with axial exit;  (g)  mixed – flow;  (h)  radial – flow (in case with alternate rotors rotating opposite);  (i)  radial – flow (centripetal);  (j) tangential –  ( Pelton turbine).

21. According to the Head at the Inlet of Turbine (i). High Head Turbine:  The net head varies in this turbine is from 150 m to 2000 m or even more. It requires small quantity of water. ( Pelton ) ( ii). Medium Head Turbine:  in this turbine, the net head varies from 30 m to 150 m . It requires moderate quantity of water.   (Francis) (iii). Low Head Turbine:  In low head turbines, the net head is less than 30 m. it requires large quantity of water. (Kaplan)

22. According to the Specific Speed of the Turbine (i). Low Specific Speed Turbine:  it has specific speed less than 50 . Pelton turbine . ( ii). Medium Specific Speed Turbine:  The specific speed varies from 50 to 250. Francis turbine . (iii). High Specific Speed Turbine:  The specific speed is more than 250 Kaplan turbine

23. In an impulse turbine, fast moving fluid is fired through a narrow nozzle at the turbine blades to make them spin around. The blades of an impulse turbine are usually bucket-shaped so they catch the fluid and direct it off at an angle. In an impulse turbine, the fluid is forced to hit the turbine at high speed. Hydraulic turbine

24. Pelton Wheel impulse turbine As the water jet hits the bucket-blades, the direction of water velocity is changed to follow the contours of the bucket. Water impulse energy exerts torque on the bucket and wheel system, spinning the wheel; the water stream itself does a " u turn"and exits at the outer sides of the bucket.

25. In Reaction Turbines, the rotation is mainly achieved by the reaction forces created by the acceleration of the fluid in the runner (rotating blade). The basic principle is :medium enters the turbine at low velocity and leaves through the jets at high velocity.

26. Energy in fluid = Kinetic energy (k)+ enthalpy (H) Total energy transfer =∆K+∆H Energy Transformation in Turbine DOR for impulse turbine=0 DOR for reaction turbine=1

27. VELOCITY TRIANGLES AT INLET AND EXIT

28. V1and V2 –inlet and outlet absolute velocities Vr1 and Vr2-inlet and outlet relative velocities U-blade speed α 1 –nozzle angle and α 2 –absolute fluid angle at outlet β 1 and β 2 inlet and outlet blade angle Vw1 Vw2 -Whirl Velocity : at inlet and outlet. Vf1 Vf2 - vertical components of the absolute velocities at inlet and exit

29. Tangential force on blade: Power developed: Blade efficiency or diagram efficiency or utilization factor=work done/kinetic energy supplied Axial thrust =m ”x ( Vf 1 – Vf 2 )

30. Exm . The velocity of steam leaving the nozzles of an impulse turbine is 900 m/s and the nozzle angle is 20’. The blade velocity is 300 m/s and the blade velocity co efficient is 0.7. C alculate the followings for a mass flow of 1 Kg /s , and symmetrical blading: (i) The blade inlet angle (ii) The driving force on the wheel (iii) The axial thrust (iv) The diagram power (v) The diagram effeciency

31. GIVEN DATA V1= 900 m/s α i = 20’ U= 300 m/s K = 0.7 V2=900x0.7 m/s m’ = 1 kg / s And symmetrical blading (βi = βe)

32. Applying Cosine Rule to OAB Vr1 Using sine rule

33. ( ii) The driving force on the wheel The blade velocity is 300 m/s and the blade velocity co efficient is 0.7 V2=V1x0.7=626x0.7=438.5 m/s

34. The axial thrust ( Axial thrust =m ”x ( Vf 1 – Vf 2 )=1x92.3=92.3 N

35. Diagram power: Diagram efficiency:

36. Operational Analysis of a Hydraulic Turbine Overall Efficiency: The ratio of the power from turbine shaft to the power in water at the point of entry into the turbine. (Water Power) Hydraulic Efficiency: The ratio of the actual power developed by the turbine runner to the power in water at the point of entry into the turbine. W𝑃 =𝜂 𝑄H𝜌𝑔

37. Operational Analysis of a Hydraulic Turbine Mechanical Efficiency: The ratio of the power from turbine shaft to the power actually developed by the turbine runner. Volumetric Efficiency: The ratio of the actual quantity of fluid doing work on the turbine runner to the total quantity supplied.

38. Factors Considered in Selection of the Type and Number of Turbines Specific Speed: 2) Peripheral velocity of the turbine blades (ms -1 ) ku – Peripheral coefficient H – Effective head on turbine (m)

39. Exm . It is required to determine the type and number of turbines required for a hydro-power station with a flow (Q) of 200 m3/s-1 ( ρ = 1000 kgm-3) available under a head (h) of 40 m . Specific speed (N S ) of each machine should not exceed 250 kg 1/2 m 1/4 s 5/2 . Speed (N) and overall efficiency (η ) of each machine should be 150 rpm and 80% respectively. Assuming a peripheral coefficient ( ku ) of 0.79, (i). Determine the total power output of the turbines.

40. i i Calculate the output power per turbine .

41. iii. Determine the number and the type of turbines required. Specific speed required = 250, a large head Therefore, a Francis turbine is required .