CODE NO: A109210202
SET - 1
R09
II B.TECH - I SEMESTER EXAMINATIONS - MAY, 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (ELECTRICAL AND ELECTRONICS ENGINEERING)
Time: 3hours
Max. Marks: 75 Answer any FIVE questions All Questions Carry Equal Marks ---
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b)
Explain the fluid property vapour pressure. Give its significance in Engineering. A body weighing 450 N with a flat surface area of 0.023m2 slides down lubricated inclined plane making a 300 angle with the horizontal. For viscosity of 0.1 N-S/m2 and body speed of 3m/s, determine the lubricant film thickness. What is the difference between simple manometer and differential manometer? A closed tank as shown in figure 1 is filled with water and is 2 m long. The pressure gauge on the tank reads 50N/m2. Determine: i) Height ‘h’ in the open water column. ii) Absolute pressure of the air on the water surface if local atmosphere pressure is 101N/m2. iii) Gauge pressure acting on the bottom surface AB of the tank. [7+8]
in
1.a)
Figure 1
Define continuity equation & derive the expression for the same for on dimension flow. The velocity componals for two dimensional, steady static and incompressible x flow field are given by U = C and V = C loge(xy). Check whether the flow exist or y not? Water is supplied to a turbine through a 0.3 m diameter pipe at the rate of 0.3m3/s. After passing through the turbine water is discharged through a draft tube which has a diameter of 0.6m at point B which is 1m below a point A in the 0.3m pipe. If the pressure at the points A and B are respectively 147.15 kN/m2 and -34.335 kN/m2. Determine the power delivered to the turbine by the water. [8+7]
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2.a)
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b)
3.a)
b)
Describe Reynold’s experiment and state the significance of Reynold’s number. Pipes of 500 mm diameter, 1800m length, 400 mm diameter, 1200 m length and 300 mm diameter, 600 m length are connected in series. If these pipes are to be replaced by an equivalent pipe of 400 mm diameter, what would be its length? A pilot tube records a reading of 7.85 kN/m2 as the stagnation pressure when it is held at the centre of a pipe of 250 mm diameter conveying water. The state pressure is the
discharge 40 mm of mercury (gauge – vacuum). Calculate the discharge through the pipe assuming that the mean velocity of flow is 0.8 times the maximum velocity, take Cd = 0.98. [7+8]
b)
Obtain an expression for force existed by a jet of water on an unsymmetrical moving curved plate when the jet strikes tangentially at one of the tips. A 50 mm diameter jet having a velocity of 25m/s, strikes a flat plate, the normal of which is incline at 300 to the axis of the jet calculate the normal force exerted on the plate, when the plate is moving with a velocity of 10 m/s in the direction of the jet. Find also the work done and the efficiency of the jet when the plate is moving. [7+8]
in
4.a)
Explain Run off river plants, Reservoir plants, pumped storage plants & Tidal plants. How mass curve technique is used to determine the capacity of reservoir to satisfy the uniform demand of water. [7+8]
6.a)
Prove for a pelton wheel turbine, the hydraulic efficiency is maximum when the bucket speed is equal to half the velocity of jet and obtain the expression for the maximum hydraulic efficiency with usual notation. The diameter of an inward radial flow turbine is 1.2 m and inward flow area is 0.5 m2. The head available is 150 m. The inlet vane angle and blade angle are 200 and 600 respectively. If the turbine is running at 500 rpm, find out the power developed by the turbine and hydraulic efficiency. Assume discharge passing through the runner. [7+8]
b)
8.a)
What is a Surge tank and a fore bay and what are their functions? Describe with neat sketches different types of surge tank? A hydraulic turbine develops 7355 kW of power under a head of 24.7m at 210 rpm. What is its specific speed? Indicate the type of turbine suitable for the purpose if this turbine is tested in the laboratory where the head available is 7.5 m, what power will if develop and at what speed? [7+8] Define Manometric efficiency, volumetric efficiency, mechanical efficiency, overall efficiency as applied to centrifugal pump. The inner and outer diameters of an impeller of a centrifugal pump are 250 mm and 500 mm respectively. The velocity of flow at outer is 1.5 m/s and vane outlet angle 600. If the manometric efficiency is 75%, final out the minimum speed required to start the flow. [7+8]
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b)
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7.a)
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b)
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5.a) b)
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CODE NO: A109210202
SET - 2
R09
II B.TECH - I SEMESTER EXAMINATIONS - MAY, 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (ELECTRICAL AND ELECTRONICS ENGINEERING)
Time: 3hours
Max. Marks: 75 Answer any FIVE questions All Questions Carry Equal Marks ---
in
nt
uW
or
b)
Differentiate i) Real fluids & Ideal fluids ii) Newtonian & non Newtonian fluids. Through a narrow gap of height δ, a thin plate of large surface is pulled with a velocity U on one side of the plate, oil is of velocity µ1, and on the other side of µ2. Determine the position of the plate so that the shear force on two sides is equal. What is the difference between U – tube differential monometer and inverted U – tube differential manometer? For the arrangement shown in figure, determine the height ‘H’. [7+8]
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1.a)
Distinguish between stream lines, streak lines & path lines the flow field is given by ψ = x3y check weather the given field exist or not? Further check whether it is irrotational? b) Water flows through a 0.9m diameter pipe at the end of which there is reduction connecting to a 0.6m diameter pipe. If the gage pressure at the entrance reduces to 412.02 kN/m2 and the velocity is 2m/s, determine the resultant thrust, assuming that the frictional; loss of head in the reduces is 1.5m. [7+8]
Aj
2.a)
3.a)
Derive an expression for loss of head due to sudden expansion in pipe line with usual notation.
With a neat sketch explain the working principle of pilot tube. A venturimeter has its axis vertical, the inlet and throat diameter being 150 mm and 75 mm respectively. The throat is 225 mm above inlet and K = 0.96. Petrol of specific gravity 0.78 flows up through the meter at a rate of 0.029 m3/s. Find the pressure difference between the inlet and the throat. [7+8]
4.a)
Obtain the relation between the velocity of jet and the velocity of the vane to obtain the maximum efficiency, when a jet of water impinges on a series of vanes mounted on the circumference of a wheel at a fixed distance apart. A jet of water having a velocity of 20 m/s strikes a curved vane which is moving with a velocity 9m/s. The vane at inlet and lever at an angle 1300 to the direction of motion of the vane and outlet, calculate the work done per second per kg of water. Strikes the vane. [7+8]
b)
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b)
Differentiate between storage and pondage supply your answer with a neat sketch. What is mass curve? Explain the procedure for preparing a mass curve and also its uses. [7+8]
6.a)
The pelton wheel has the water head 5.6 m. If the speed ratio = 2.09 flow ratio = 0.68 overall efficiency 86% and the diameter of the boss is 1/3 the diameter of the runner. Find the diameter of the runner, its speed of and the specific speed of the turbine.
or
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5.a) b)
b) Obtain an expression for the work done per second by water on the runner of the pelton wheel. Hence derive an expression for maximum efficiency [7+8]
b)
8.a)
Define NPSH and derive the equation for the same. Why pump industry specifies NPSH for pumps. What is its significance? A water pump has to deliver 20 lit/s of water when running at 1200 rpm. The inlet vane angle is 300 and exit vane angle is 450. If the velocity of flow is constant in the impeller, the power supplied to run the pump by the motor is 40 kW. Assuming the mechanical efficiency as 0.9 final inlet and outlet diameters of the impeller. Take D2 = 2d. [7+8]
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b)
Derive an expression for specific speed of turbine. What is its significance in the design of turbine? Water is flowing in a long pipe which is 0.15 m diameter and 6.25 mm thick with a velocity of 1.2 m/s and it is suddenly brought to rest by the closing of a valve. Calculate the inertia pressure and the theoretical stress produces in the pipe near the valve, taking K for water as 207×104 kN/m2 and E for pipe material as 206×106 kN/m2. [7+8]
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7.a)
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CODE NO: A109210202
SET - 3
R09
II B.TECH - I SEMESTER EXAMINATIONS - MAY, 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (ELECTRICAL AND ELECTRONICS ENGINEERING)
Time: 3hours
Max. Marks: 75 Answer any FIVE questions All Questions Carry Equal Marks ---
2.a)
Define stream function. What are its properties? A stream function is given by ψ = 3x2 – y3. Determine the magnitude and velocity components at the point (2, 1). State the different forces considered in studying the equation of motion of a fluid state the condition under which each is significant. A pump has a tapered such on pipe and discharges water out of a sump. The diameters of pipe at the inlet and at the upper end are 0.5m and 0.25m. The free water surface in the sump is 2m above the centre of the inlet and the pipe is paid at a slope of 1(vertical) to 5(along the line). The pressure at the top end of the pipe is 6m(abs) and it is known that the loss of head due to friction between the two sections is 1/10 of the velocity head at the top section. Compute the discharge in the pipe if its length is 25m. Take atmosphere pressure as 10m. [7+8]
3.a)
Derive an expression for equivalent pipes in parallel. Three pipes 300m long, 300mm diameter; 150m long, 200mm diameter and 200m long, 250mm diameter are connected in series in the same order. Pipe having 300mm diameter is connected to reservoir. Water level in the reservoir is 15m above the pipe axis which is horizontal. The respective friction factors for the three pipes are 0.018, 0.02 and 0.019. Determine flow rate. Water flows through an inclined verturimeter. The inlet and throat diameters are 0.10m and 0.05m respectively and their height difference is 0.30m. A mercury manometer located across the inlet and the throw indicates 0.10m of mercury column at a given flow rate. Estimate the flow rate, Coefficient of discharge and pressure difference between inlet and the throat. [7+8]
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b)
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b)
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b)
What is Kinetic Viscosity? Why is it so called? Give its dimensions and units. If a certain liquid has Viscosity 0.1448 N.S/m2 and Kinetic Viscosity 1.73×10-4 m2/s. What is its specific gravity? Define gauge pressure, vacuum pressure and absolute pressure. Indicate their relative position on a chart. Convert a pressure head of 15m of water i) meters of oil of specific gravity 0.750 ii) Meters of mercury of specific gravity 13.6. [7+8]
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1.a)
Prove that the force external by a jet of water on a fixed Semi-Circular plate in the direction of the jet when the jet strikes at the centre of the Semi circular plate is two times the force external by the jet on a fixed vertical plate. A jet of water having a velocity of 40 m/s strikes a curved vane, which is moving with a velocity of 20m/s. The jet makes an angle of 300 with the direction of motion of vane at inlet and leaves at an angle of 900 to the direction of motion of vane at outlet. Draw the velocity triangles at inlet and determine the vane angles at inlet and outlet so that the water enters and leaves the vane without shock. [7+8] With a neat sketch explain the various components of Hydro Power Plants.
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4.a)
b)
5.a)
What are the different types of efficiencies of the turbine? How are they different from each other? [7+8]
6.a)
Show that the hydraulic efficiency of Francis turbine is given by 1 ηn = ⎡ ⎤ ⎢1/ 2 tan 2 α ⎥ 1+ ⎢ tan α ⎥ ⎢ 1− ⎥ tan θ ⎦ ⎣ Where α = guide blade angle and θ = runner vane angle at inlet. The turbine is having parallel discharge outlet. A jet of water coming out of 150mm diameter nozzle strikes the buckets of person wheel and jet is deistical through an angle 1650. Final the force external by the jet on the bucket and power developed. Take following date: U Head available at nozzle = 500 m, Cv = 0.97, = 0.46. V The reduction in relative velocity at exit of the bucket is 15%. [8+7]
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b)
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b)
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7.a) Briefly explain how the turbines are selected on the basin of head available and specific speed. Why these parameters are adopted in the selection process. b) A model of a turbine is 1/5 of prototype and it is tested under the available head of 40m. The prototype turbine is used to run under the head of 40m and 400 RPM. Find the speed of the model, if it develops 100kW when quantity of water supplied is 0.7 m3/s. Also find the power which will be developed by the prototype. Also find overall efficiency for model as were as for prototype. [7+8]
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8.a) Differentiate pumps in series, pumps in parallel and multi stage centrifugal pump. Under what circumstances they are used? What are their limitations? b) A single stage centrifugal pump has an impeller of 300mm diameter which rotates at 1780 rpm and discharges 4000 lit/minute to a height of 25m at an efficiency of 70%. Obtain the number of stages of a similar multi stage pump to lift 5000 lit/minute to 157m at 150 r.p.m. [7+8]
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CODE NO: A109210202
SET - 4
R09
II B.TECH - I SEMESTER EXAMINATIONS - MAY, 2011 FLUID MECHANICS AND HYDRAULIC MACHINERY (ELECTRICAL AND ELECTRONICS ENGINEERING)
Time: 3hours
Max. Marks: 75 Answer any FIVE questions All Questions Carry Equal Marks ---
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b)
A cylinder of 0.3m diameter rotates in annular sleeve of 0.31m internal diameter. Both the cylinders are 0.3m long. Determine the viscosity of the liquid which fills the space between the cylinder if a torque of 0.98 N.m is required to maintain an angular velocity of 2π rad/s. With a neat sketch of ‘u’ tube connected to a pipe under pressure, explain the procedure of writing manometric equation.(Assume the u tube manometer contain mercury on manometric liquid and open to atmosphere). Gauge ‘A’ attached at the bottom of a tank shown in figure reads 350KPa (abs). What is the height ‘h’ of water? What is the reading of gauge ‘B’? [7+8]
in
1.a)
2.a)
Define steady, non steady, uniform and non uniform flow. The following given stream function responds a two dimensional steady state of flow ψ = 4(x2 – y2). Check whether the flow is irrotational or not? If it is irrotational, then find out the corresponding velocity potential function. Describe the nature of various forces normally included in the momentum equation. A vertical pipe carrying oil of sp.gravity 0.8 taken uniformly from 200mm diameter at the lower section to 100mm diameter at the upper section. The vertical distance between the sections is 1 m. The pressure gauges installed at the lower and upper section read 6 N/m2 and 5 N/m2 respectively when the discharge of oil is 30 litres/ seconds. Calculate the loss of head between the two sections. Determine the direction of flow also. [7+8]
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b)
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Figure
Define ‘Hydraulic gradient line’ and ‘Total energy line’. The cross section of a pipe carrying a given discharge is suddenly enlarged. What would be the ratio of the two diameters of the pipe if the magnitude of the loss of head at this change of section is same irrespective of the direction of flow? Assume CC = 0.64. Determine the throat diameter of a venturimeter for installation in a 100mm diameter pipeline carrying oil of sp. Gravity 0.87. The maximum range of available oil – mercury differential gauges is 0.5 m of mercury deflection. Find the maximum throat diameter which would show full gauge deflection when the rate of flow is 20 litres per [7+8] second. Assume Cd = 0.984.
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3.a)
b)
6.a)
b)
7.a) b)
8.a)
in
b)
Define Gross head and Net head as applied to hydraulic turbine. How effective head of reaction turbine differs from impulse turbine. How hydro power plants are classified on functional basis and on the basis of head under which they operate? [8+7]
With neat sketch explain draft tube. Why draft tube is used in reaction turbine? Explain how the net head on the reaction turbine is increased with the use of draft tube. Find out the hydraulic power developed by the pelton wheel which is moving with a velocity of 20m/s. The net head available on the nozzle is 50m. Take following data Cv = 0.98, Angle of deflection is 1650 and discharge Q = 30 liters/second. [7+8]
ld .
5.a)
Explain unit speed, unit discharge & unit power of hydraulic turbine. Why they are defined for the turbine? A pelton wheel develops 5520 kW break power when running at 180 RPM and head available is 250m and overall efficiency is 80%. The speed ratio is 0.46. Find the speed, discharge and power developed when available head is reduced to 200m. [7+8]
or
b)
A jet having a velocity V strikes a single curved vane moving in the same direction as the jet with velocity u, so that velocity of the jet relative to the vane is (v-u). The vane causes the jet to be reversed in direction. Show that the maximum efficiency is obtained when V = 3u and that this maximum efficiency is slightly less than 0.6. A jet of water having a velocity of 15m/s strikes a curved vane which is moving with a velocity of 5 m/s. The vane is symmetrical and it is so shaped that jet is deflected through 1200. Find the angle of the jet at inlet of the vane so that there is no shock. What is the absolute velocity of the jet at outlet in magnitude and direction? [7+8]
Prove that minimum speed required for the centrifugal pump to start is given by
N=
120 Vw2 D2 η π ( D22 − D12 ) mano
The inner and outer diameter of the impeller of a centrifugal pump are 250mm and 500mm. The velocity of flow through the impeller is constant and 5m/s. Taking outlet vane angle as 450; find inlet vane angle, absolute velocity of water at outlet and power available at the pump when it is running at 1200 rpm and discharging at the rate of 0.2 m3/s. [7+8]
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b)
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4.a)
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