## Monday, 29 August 2011

### Assignment - 8

Fluid Mechanics & Hydraulic Machinery – 8th UNIT
Assignment - 8
2009
1.         (a) What is priming? Why is it necessary? Explain how it is done.
(b) Find the number of pumps required to take water from a deep well under a total head of 156 m. Also, the pumps are identical and are running at 1000 r.p.m. The specific speed of each pump is given as 20 while the rated capacity of each pump is 150 lit/s.         [8+8]
2.         (a) Define a centrifugal pump. Explain the working of a single-stage centrifugal pump with sketches.
(b) The internal and external diameters of the impeller of a centrifugal pump are 30 cm and 60 cm respectively. The pump is running at 1000 r.p.m. The vane angles at inlet and outlet are 200 and 300 respectively. The water enters the impeller radially and velocity of flow is constant. Determine the work done by the impeller per unit weight of water. [8+8]
3.         (a) How will you determine the possibility of the cavitation to occur in the installation of a turbine or a pump?                                                                                                             [8+8]
(b) A single-acting reciprocating pump running at 30 r.p.m., delivers 0.012 m3/s of water. The diameter of the piston is 25 cm and stroke length 50 cm. Determine:
i. The theoretical discharge     ii. Co-efficient of discharge   iii. Slip and percentage slip
5.         (a) What is cavitation and what are its causes? How will you prevent the cavitation in hydraulic machines?
(b) A single-acting reciprocating pump has a cylinder of a diameter 15 cm and of stroke length 30 cm. The centre of the pump is 4 m above the water surface in the sump. The atmospheric pressure head is 10.3 m of water and pump is running at 40 r.p.m. If the length and diameter of the suction pipe are 5 m and 10 cm respectively, determine the pressure head due to acceleration in the cylinder:
i. At the beginning of the suction stroke  ii. In the middle of suction stroke.                        [8+8]
6.         (a) Find an expression for the head lost due to friction in suction and delivery pipes.
(b) A centrifugal pump (diffusion type) has a suction lift of 1.5 m and the delivery tank is 13.5 m above the pump. The velocity of water in the delivery pipe is 1.5 m/s. The radial velocity of flow through the wheel is 3 m/s. and the tangent to the vane at exit from the wheel makes an angle of 1200 with the direction of motion. Assuming that the water enters radially and neglecting friction and other losses, determine:
i. Velocity of wheel at exit     ii. Velocity and pressure head at exit from the wheel
iii. Direction of fixed guide vanes.                                                                             [8+8]
(b) A Centrifugal pump is running at 1000 r.p.m. The outlet vane angle of the impeller is 300 and velocity of flow at outlet is 3 m/s. The pump is working against a total head of 30 m and the discharge through the pump is 0.3 m3/s. If the manometric efficiency of the pump is 75%, determine:
i. The diameter of the impeller            ii. The width of the impeller at outlet.           [8+8]
8.         (a) Show from first principle that the work saved, against friction in the delivery pipe of a single-acting reciprocating pump, by fitting an air vessel is 84.8% while for a double-acting reciprocating pump the work saved is only 39.20%.
(b) What is negative slip in a reciprocating pump? Explain with neat sketches the function of air vessels in a reciprocating pump. [8+8]
2010
1.         A three stage centrifugal pump has impellers 40cm in diameter and 2cm wide at outlet. The vanes are curved back at the outlet at 450 and reduce the circumferential area by 10%. The manometric efficiency is 90% and the overall efficiency is 80%. Find the head generated by the pump when running at 1000 r.p.m delivering 50lps. What should be the shaft horse power?
2.         A four-stage centrifugal pump has four identical impellers keyed to the same shaft. The shaft is running at 400 r.p.m and the total manometric head developed by the multistage pump is 40m. The discharge through the pump is 0.2 m3/ s .The vanes of each impeller are having outlet angle as 450. If the width and diameter of each impeller at outlet is 5cm and 60cm respectively find the manometric efficiency.
3.         Explain the performance characteristic curves of a centrifugal pump.
4.         A single-stage centrifugal pump with impeller diameter of 30cm rotates at 2000r.p.m and lifts 3m3 of water per second to a height of 30m with an efficiency of 75%. Find the number of stages and diameter of each impeller of a similar multistage pump to lift 5m3 of water per second to a height of 200 meters when rotating at 1500 r.p.m.
5.         (a) How will you obtain an expression for the minimum speed for starting a centrifugal pump?
(b) Find the rise in pressure in the impeller of a centrifugal pump through which water is flowing at the rate of 15 lit/s. The internal and external diameters of the impeller are 20 cm and 40 cm respectively. The widths of impeller at inlet and outlet are 1.6 cm and 0.8 cm. The pump is running at 1200 r.p.m. The water enters the impeller radially at inlet and impeller vane angle at outlet is 300. Neglect losses through the impeller. [16]

### Assignment - 7

Fluid Mechanics & Hydraulic Machinery – 7th UNIT
Assignment - 7
2009
1.         (a) What is cavitation? How can it be avoided in reaction turbine?                           [8+8]
(b) What is governing and how it is accomplished for different types of water turbines?
2.         (a) Obtain an expression for unit speed, unit discharge and unit power for a turbine.
(b) A Pelton wheel is revolving at a speed of 200 r.p.m. and develops 5886 kW S.P when working under a head of 200 m with an overall efficiency of 80%. Determine unit speed, unit discharge and unit power. The speed ratio for the turbine is given as 0.48. Find the speed, discharge and power when this turbine is working under a head of 150 m. [8+8]
3.         (a) Define the term Governing of a turbine. Describe with a neat sketch the working of an oil pressure governor.
(b) A Kaplan turbine working under a head of 29 m develops 1287.5 kW S.P. If the speed ratio is equal to 2.1, flow ratio = 0.62, diameter of boss = 0.34 times the diameter of the runner and overall efficiency of the turbine = 89%, find the diameter of the runner and the speed of turbine.                                                                                                     [8+8]
4.         (a) Define the specific speed of a turbine? Derive an expression for the specific speed. What is the significance of the specific speed?                                                     [8+8]
(b) A turbine is to operate under a head of 30 m at 300 r.p.m. The discharge is 10 m3/s. If the efficiency is 90%, determine:
i. Specific speed of the machine, ii. Power generated, and iii. Types of the turbine.
5.         (a) What are unit quantities? Define the unit quantities for a turbine. Why are they important?
(b) A turbine develops 7357.5 kW S.P. when running at 200 r.p.m. The head on the turbine is 40 m. If the head on the turbine is reduced to 25 m, determine the speed and power developed by the turbine.                                                                                    [8+8]
2010
1.         What is meant by specific speed? Also derive the expression for specific speed of a turbine.
2.         (a) Explain the necessity of unit quantities with reference to turbines.
(b) A turbine is to operate under a head of 25m at 200r.p.m. The discharge is 9 Cumecs. If the efficiency is 90%, find the performance of the turbine under a head of 20meters.

3.         (a) What is meant by governing of turbines?
(b) A turbine is to operate under a head of 25m at 200r.p.m. The discharge is 9 Cumecs. If the efficiency is 90% determine specific speed of the machine, power generated and type of turbine.
4.         Explain the characteristic curves of a turbine.

### Assignment - 6

Fluid Mechanics & Hydraulic Machinery – 6th UNIT
Assignment - 6
2009
1.         (a) Draw a schematic diagram of a Francis turbine and explain briefly its construction and working.
(b) A Pelton wheel having a mean bucket diameter of 1.0 m is running at 1000 r.p.m. the side clearance angle is 150 and discharge through the nozzle is 0.1 m3/s, determine power available at the nozzle and hydraulic efficiency of the turbine.                    [16]
2.         (a) What do you mean by gross head, net head and efficiency of a turbine? Explain the different types of the efficiencies of a turbine.
(b) A Pelton wheel has a mean bucket speed of 35 m/s with a jet of water flowing at the rate of 1 m3/s under a head of 270 m. The buckets deflect the jet through an angle of 1700. Calculate the power delivered to the runner and the hydraulic efficiency of the turbine. Assume co-efficient of velocity as 0.98.                                                           [16]
3.         (a) Describe briefly the functions of various main components of Pelton turbine with neat sketches.
(b) The following data is given for a Francis turbine: Net head = 70 m, speed = 600 r.p.m., shaft power = 367.875 kW, ηo = 85%, ηh = 95%, flow ratio = 0.25, breadth ratio = 0.1, outer diameter of the runner = 2 X inner diameter of runner. The thickness of vanes occupy 10% of the circumferential area of the runner. Velocity of flow is constant at inlet and outlet and discharge is radial at outlet. Determine:
ii. Runner vane angles at inlet and outlet,
iii. Diameters of runner at inlet and outlet, and
iv. Width of wheel at inlet.                                                                                         [8+8]
4.         (a) What do you understand by the characteristic curves of a turbine? Name the important types of characteristic curves.
(b) An outward flow reaction turbine has internal and external diameters of the runner as 0.5 m and 1.0 m respectively. The guide blade angle is 150 and velocity of flow through the runner is constant and equal to 3 m/s. If the speed of the turbine is 150 r.p.m., head on turbine is 10 m and discharge at outlet is radial, determine:
i. The runner vane angles at inlet and outlet,
ii. Work done by the water on the runner per unit weight of water striking per second and
iii. Hydraulic efficiency.                                                                                             [8+8]
2010
1.         (a) Explain the various terms associated with Pelton wheel.
(b) A Pelton wheel is having a mean bucket diameter of 1m and is running at 1000r.p.m.  The net head on the pelton wheel is 700m. If the side clearance angle is 150 and discharge through nozzle is 0.1m3/s, find the power available at the nozzle and hydraulic efficiency of the turbine.
2.         (a) Explain the various efficiencies in a hydraulic turbine.
(b) A pelton wheel is to be designed for a head of 60m when running at 200r.p.m. The pelton wheel develops 95.6475 KW shaft power. The velocity of the bullets = 0.45times the velocity of the jet, overall efficiency = 0.85 and coefficient of velocity = 0.98. Find the diameter of jet, wheel, width and depth of buckets and number of buckets on the wheel.
3.         (a) Explain the classification of hydraulic Turbines.
(b) Also explain the different efficiencies of a hydraulic Turbine.
4.         (a) Explain pelton wheel with a neat sketch.
(b) An inward flow reaction turbine has external and internal diameters as 1m and 0.5m respectively. The velocity of flow through the runner is constant and is equal to 1.5m/s. Find discharge through the runner and width of the turbine at outlet if the width of the turbine at inlet = 200mm.

### Assignment - 5

Fluid Mechanics & Hydraulic Machinery – 5th UNIT
Assignment - 5
2009
1.         (a) What are penstocks? What is meant by economical diameter of a penstock? How can it be found?
(b) What are the functions of a surge tank? Describe with neat sketches, the behavior of various types of surge tanks.                                                                                         [8+8]
2.         (a) Explain firm power and secondary power in detail                                               [8+8]
(b) What are the different methods of classifying the hydroelectric power plants? Explain.
3.         (a) Discuss the relative merits and demerits of hydropower as compared to other power sources.
(b) Describe how water power potential is estimated before any power plant is contemplated.                                                                                                                   [8+8]
4.         (a) What are valves used in a penstock. Explain with neat sketches, various types of valves with their suitability under various conditions.                                       [8+8]
(b) What are intake structures? Explain different types with the help of neat sketches.
5.         (a) Describe the status of hydroelectric power in India.
(b) Explain how the load factor, capacity factor and utilization factor interrelated. Also explain the significance of diversity factor.                                                                      [8+8]
6.         (a) What is forebay and what are different parts of forebay. Explain.
(b) What is a tunnel? Discuss the classification of tunnels.                                        [8+8]
2010
1.         What are the different types of hydel plants? Explain in detail.
2.         Explain the principal components of hydroelectric scheme.