VELTECH HIGH TECH DR RANGARAJAN DR SAKUNTHALA ENGINEERING COLLEGE YR: II SEM: III Fluid Mechanics and Machinery SUB CODE: ME 2204 PART A Define Reynolds’s number. Mention the circumstances which necessitate the use of distorted models? list out the advantages of dimensional analysis. What is the need for priming in pump? What do you mean by Hydraulic efficiency of turbine? What is a dimensionally homogeneous equation? Give examples? Give the applications of dimensionless numbers Define specific speed of turbine. What is draft tube? PART B State Buckingham’s (-theorem and explain about theorem Write short notes on i).Froude number ii).Weber’s Number iii).Mach Number. Using Buckingham’s π Theorem show that the discharge Q, consumed by an oil ring is given by Q=Nd3φ (µ/ρNd2,σ/ρN2d3,w/ρ N2d) where d is internal diameter of the ring, N is the rotational speed, ρ is the density of the fluid, µ is the viscosity of the fluid, σ is the surface tension and w is the specific weight of the oil. The efficiency of a fan depends on density ρ, viscosity µ,angular velocity ω, diameter d of the rotor and the discharge Q. Express efficiency in terms of dimensionless parameters using Buckingham’s π Theorem. (16 M) A centrifugal pump is to discharge 0.118m3/s at a speed of 1450 r.p.m against a head of 25 m. The impeller diameter is 25 cm, its width at outlet is 5 cm and manometric efficiency is 75%.Determine the vane angle at the outer periphery of the impeller and draw its triangles. (16 Marks) Discuss briefly the characteristic curves of hydraulic turbines. (8 M) A Kaplan turbine is to be designed to develop 9100kW.The net available head is 5.6m.If the speed ratio is 2.09,flow ratio is 0.68,overall efficiency is 86% and the diameter of the boss is 1/3 the diameter of the runner. Find the diameter of the runner, its speed and specific speed of turbine. Explain the parts and working principles of Pelton wheel / Turbine Write short notes on i) Froude’s number ii) Euler’s number iii) Weber’s Number iv) Mach’s number Using Buckingham’s (- theorem, show that the velocity through a circular orifice is given by where H is the head causing flow, D is the diameter of the orifice, ( is co-efficient of viscosity, ( is the mass density and g is the acceleration due to gravity. A ship 300m long moves in sea- water, whose density is 1030 kg/m3, A1:100 model of this ship is to be tested in a wind tunnel around the model is 30m/s and the resistance of the model is 60N. Determine the velocity of ship in sea- water and also the resistance of the ship in sea – water. The density of air is given as 1.24 kg/m3. Take the kinematic viscosity of sea – water and air as 0.012 strokes and 0.018 strokes respectively (3.63) The penstock supplies water from a reservoir to the Pelton wheel with a gross head 500 m. one-third of the gross head is lost in friction in the penstock. The rate of flow of water through the nozzle fitted at the end of the penstock is 2.0 m3/s. the angle of deflection of the jet is 165(. Determine the power given by the water to the runner and also hydraulic efficiency of the pelton wheel. Take speed ratio = 0.45 and Cv = 1.0. A Francis turbine with an overall efficiency of 75% is required to produce 148.25 kW power. It is working under a head of 7.62 m. The peripheral velocity = 0.26 and the radial velocity of flow at inlet is 0.96 . The wheel runs at 150 r.p.m. and the hydraulic losses in the turbine are 22% of the available energy. Assuming radial discharge, determine: (i) The guide blade angle, (ii) The wheel vane angle at inlet, (iii)Diameter of the wheel at inlet and (iv) Width of the wheel at inlet. The drag force (F) on a partially submerged body depends on the relative velocity (v) between the body and the fluid, characteristics linear dimension (l), height of surface roughness (k), fluid density (ρ), the viscosity (µ) and the acceleration due to gravity (g). Obtain an expression for the drag force, using the method of dimensional analysis.
Posted on: Thu, 19 Sep 2013 11:30:41 +0000
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