Fluid mechanics and hydraulic machinery

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JNTUK R10 2-1 SEM PREVIOUS PAPERS(MECHANICAL ENGINEERING)

JNTUK R10 2-1 SEM PREVIOUS PAPERS(MECHANICAL ENGINEERING)

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  • 1. JNTUWORLD Code No: T0321/R07 II B.Tech II Semester, Regular Examinations, Apr - 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (Mechanical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. a) If 5 m3 of a certain oil weighs 4000 kg(f), calculate the specific weight, mass density, and specific gravity of this oil. b) Express pressure intensity of 7.5 kg/cm2 in all pressure units. Take the barometer reading as 76 cm of mercury. 2. a) A bend in pipeline conveying water gradually reduces from 60 cm to 30 cm diameter and deflects the flow through angle of 600 . At the larger end the gage pressure is 1.75 kg/cm2 . Determine the magnitude and direction of the force exerted on the bend, i) when there is no flow, ii) when the flow is 876 litres per sec. b) Define and distinguish between streamline, path line and streak line. 3. a) A pipeline 22.5 cm in diameter and 1580 m long has a slope of 1 in 200 for the first 790 m and 1 in 100 for the next 790 m. The pressure at the upper end of the pipeline is 1.1 kg/cm2 and at the lower end is 0.55 kg/cm2 . Taking f = 0.032 determine the discharge through the pipe. b) A venture meter having a diameter of 7.5 cm at the throat and 15 cm diameter at the enlarged end is installed in a horizontal pipeline 15 cm in diameter carrying an oil of specific gravity 0.9. The difference of pressure head between the enlarged end and the throat recorded by a U-tube is 17.5 cm of mercury. Determine the discharge through the pipe. Assume the co-efficient of discharge of the meter as 0.97. 4. A jet of water 7.5 cm diameter having a velocity of 20 m/sec, strikes normally a flat smooth plate. Determine the thrust on the plate (a) if the plate is at rest, (b) if the plate is moving in the same direction as the jet with a velocity of 5 cm/sec. Also find the work done per second on the plate in each case and the efficiency of the jet when the plate is moving. 5. a) What are the different types of hydropower plant? Describe each one briefly. b) What do you understand by a ‘flow duration curve’? How is it prepared? 1 of 2 SET Ͳ ϭ www.jntuworld.com www.jntuworld.com
  • 2. JNTUWORLD Code No: T0321/R07 6. a) What are the uses of a draft tube? Describe with neat sketches different types of draft tubes. b) A Pelton wheel has to be designed for the following data: Power to be developed=8000 hp; Net head available=300 m ; Speed=550 r.p.m. ; Ratio of jet diameter to wheel diameter=1/10 and overall efficiency=85%. Find the number of jets ; diameter of the jet ; diameter of the wheel and the quantity of water required. 7. a) What is a surge tank and a forebay and what are their functions? Describe with neat sketches different types of surge tanks. b) A Francis turbine working under a head of 5 m at a speed of 210 r.p.m. develops 100 h.p. when the rate of flow of water is 1.8 m3 /sec. The runner diameter is 1 m. If the head on this turbine in increased to 16 m, determine its new speed, discharge and power. 8. a) Explain the term ‘slip’ and ‘cavitation’ with reference to reciprocating pumps. b) Explain with neat sketches the working of a single-stage centrifugal pump. 2 of 2 SET - 1 www.jntuworld.com www.jntuworld.com
  • 3. JNTUWORLD Code No: T0321/R07 II B.Tech II Semester, Regular Examinations, Apr - 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (Mechanical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. a) Carbon-tetra chloride has a mass density of 162.5 msl/m3 . Calculate its mass density, specific weight and specific volume in the English system of units. Also calculate its specific gravity. b) Define the terms gage pressure, vacuum pressure and absolute pressure. Indicate their relative positions on a chart. 2. a) The diameter of a pipe bend is 30 cm at inlet and 15 cm at outlet and the flow is turned through 1200 in a vertical plane. The axis at inlet is horizontal and the centre of the outlet section is 1.5 m below the centre of the inlet section. The total volume of fluid contained in the bend is 0.85 m3 . Neglecting friction, calculate the magnitude and direction of the force exerted on the bend by water flowing through it at 225 litres per sec when the inlet pressure is 1.4 kg/cm2 . b) What is meant by one-dimensional, two-dimensional and three dimensional flows? 3. a) The population of a city is 8,00,000 and it is to be supplied with water from a reservoir 6.4 km away. Water is to be supplied at the rate of 140 litres per head per day and half the supply is to be delivered in 8 hours. The full supply level of the reservoir is R.L. 180.00 and its lowest water level is R.L.105.00. The delivery end of the main is at R.L.22.50 and the head required there is 12 m. Find the diameter of the pipe. Take f=0.04. b) What is a compound pipe? How would you determine the equivalent size of a compound pipe? 4. A jet of water moving at 20 m/sec impinges on a symmetrical curved vane shaped to deflect the jet through 1200 (that is the vane angle ߠ and ‫׎‬ are each equal to 300 ). If the vane is moving at 5 m/sec, find the angle of the jet so that there is no shock at inlet. Also determine the absolute velocity of exit in magnitude and direction, and the work done. 5. a) Explain briefly how can the power available for a hydel project be estimated. b) Make a neat sketch of a hydropower plant and show clearly the various elements. 1 of 2 SET - 2 www.jntuworld.com www.jntuworld.com
  • 4. JNTUWORLD Code No: T0321/R07 6. a) Explain briefly the principles on which a Kaplan turbine works. b) A pipeline 1200 m long supplies water to 3 single jet Pelton wheels. The head above the nozzle is 360 m. The velocity coefficient for the nozzle is 0.98 and the coefficient of friction for the pipeline is 0.02. The turbine efficiency based on the head at the nozzle is 0.85. The specific speed of each turbine is 17.8 and the head lost due to friction in the pipeline is 12 m of water. If the operating speed of each turbine is 560 r.p.m., determine: i) The total H.P. developed. ii) The diameter of each nozzle. iii) The diameter of the pipeline. iv) Volume of water used per sec. 7. a) What do you understand by governing of hydraulic turbines? Explain with sketches the working of an oil pressure governor. b) A turbine develops 10140 h.p. under a head of 24.7 m at 135 r.p.m. What is the specific speed? What would be its normal speed and output under a head of 19.5 m? 8. a) Explain the working principles of reciprocating pump with sketches. b) What are the different efficiencies of a centrifugal pump? 2 of 2 SET - 2 www.jntuworld.com www.jntuworld.com
  • 5. JNTUWORLD Code No: T0321/R07 II B.Tech II Semester, Regular Examinations, Apr - 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (Mechanical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. a) A plate, 0.0254 mm distant from a fixed plate, moves at 61 cm/sec and requires a force of 0.2 kg (f)/m2 to maintain this speed. Determine the dynamic viscosity of the fluid between the plates. b) Explain how vacuum pressure can be measured with the help of a U-tube manometer. 2. a) A 30 cm pipe carries water at a velocity of 24.4 m/sec, At points A and B measurements of pressure and elevation were respectively 3.68 kg/cm2 and 2.94 kg/cm2 and 30.5 m and 33.5 m. For steady flow, find the loss of head between A and B. b) State and derive Bernoulli’s Theorem, mentioning clearly the assumption underlying it. 3. a) Explain the terms hydraulic gradient and total energy lines. b) A venture meter has its axis vertical, the inlet and throat diameters being 15 cm and 7.5 cm respectively. The throat is 22.5 cm above inlet and K=0.96. Petrol of specific gravity 0.78 flows up through the meter at a rate of 0.029 m3 /sec. Find the pressure difference in kg/cm2 between inlet and throat. 4. A jet of water 5 cm in diameter having a velocity of 20 m/sec, strikes normally in flat smooth plate. Determine the thrust on the plate (a) if the plate is at rest ; (b) if the plate is moving in the same direction as the jet with a velocity of 8 m/sec. Also find the work done per second on the plate and the efficiency of the jet when the plate is moving. 5. a) What are the different types of hydropower plant? Describe each one briefly. b) What do you understand by a ‘flow duration curve’? How is it prepared? 6. a) What are the uses of a draft tube? Describe with neat sketches different types of draft tubes. b) Design a Francis turbine runner with the following data ; Net head H =68 m ; speed N=750 r.p.m. ; output P=450 H.P. ; hη =94% ; 0η =85% ; flow ratio ψ =0.15 ; breadth ratio n=0.1 ; inner diameter of runner is ¸ ¹ · ¨ © § 2 1 outer diameter. Also assume 6% of circumferential area of the runner to be occupied by the thickness of the vanes. Velocity of flow remains constant throughout and flow is radial at exit. 1 of 2 SET - 3 www.jntuworld.com www.jntuworld.com
  • 6. JNTUWORLD Code No: T0321/R07 7. a) Explain i) Unit speed, ii) Unit discharge, iii) Unit power of a hydraulic turbine. Derive expressions for each of them. b) A model of Francis turbine one-fifth of full size, develops 4.1 h.p at 306 r.p.m. under a head of 1.77 m. Find the speed and power of full size turbine operating under a head of 5.7 m, if i) the efficiency of the model and the full size turbine are same, ii) the efficiency of the model turbine is 76 % and the scale effect is considered. 8. a) A single acting reciprocating pump has a plunger diameter of 25 cm and stroke of 35 cm. If the speed of the pump is 60 r.p.m. and it delivers 16.5 litres per second of water, find the theoretical discharge, coefficient of discharge, the slip and the percentage slip of the pump. b) What is meant by ‘Priming’ of a pump? What are the different priming arrangements employed for small and big pumping units? 2 of 2 SET - 3 www.jntuworld.com www.jntuworld.com
  • 7. JNTUWORLD Code No: T0321/R07 II B.Tech II Semester, Regular Examinations, Apr - 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (Mechanical Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks 1. a) Through a very narrow gap of height h, a thin plate of large extent is pulled at a velocity V. On one side of the plate is oil of viscosity ߤ1 and on the other side oil of viscosity ߤ2. Calculate the position of the plate so that i) the shear force on the two sides of the plate is equal; ii) the pull required to drag the plate is minimum. b) State the advantages of mechanical pressure gages over the manometers. 2. a) A pipe 300 m long has a slope of 1 in 100 and tapers from 1.2 m diameter at the high end to 0.60 m diameter at the low end. Quantity of water flowing is 5400 litres per minute. If the pressure at the high end is 0.70 kg/cm2 , find the pressure at the low end. Neglect losses. b) Define and distinguish between i) steady and unsteady flow; ii) uniform and non-uniform flow iii) rotational and irrotational flow. 3. a) What is a compound pipe? How would you determine the equivalent size of a compound pipe? b) A pipeline ABC 180 m long, is laid on an upward slope of 1 in 60. The length of the portion AB is 90 m and its diameter is 15 cm. At B the pipe section suddenly enlarges to 30 cm diameter and remains so for the remainder of its length EC, 90 m. A flow of 50 litres per second is pumped into the pipe at its lower end A and is discharged at the upper end C into a closed tank. The pressure at the supply end A is 1.5 kg/cm2 . Sketch i) the total energy line, ii) the hydraulic gradient line and also find the pressure at the discharge and C. Take f=0.02. 4. Show that the efficiency of a free jet striking normally a series of flat plates mounted on the periphery of a wheel never exceeds 50%. 5. a) Explain briefly how can the power available for a hydel project be estimated. b) Make a neat sketch of a hydropower plant and show clearly the various elements. 6. a) Explain briefly the principles on which a Kaplan turbine works. b) A Kaplan turbine produces 80000 H.P. under a head of 25 m with an overall efficiency of 90%. Taking the value of speed ratio ku as 1.6, flow ratio ψ as 0.5 and the hub diameter as 0.35 times the outer diameter, find the diameter and speed of the turbine. 1 of 2 SET - 4 www.jntuworld.com www.jntuworld.com
  • 8. JNTUWORLD Code No: T0321/R07 7. a) What is meant by ‘cavitation’ ? What is Thoma’s cavitation factor, and what is its significance for water turbines? b) Estimate the maximum height of straight conical draft tube of 18000 h.p., Francis turbine running at 150 r.p.m. under a net head of 27 m. The turbine is installed at a station where the effective atmospheric pressure is 10.6 m of water. The draft tube must sink at least 0.77 m below the tail race. 8. a) A double acting reciprocating pump having piston area 0.1 m2 has a stroke 0.30 m long. The pump is discharging 2.4 m2 of water per minute at 45 r.p.m. through a height of 10 m. Find the slip of the pump and the power required to drive the pump. b) Under what headings the centrifugal pumps are classified? 2 of 2 SET - 4 www.jntuworld.com www.jntuworld.com