# VTU Previous Question Papers BE-ME 5th Semester

# Turbo machines June 2010

Important Note : I. On completing your any *s, compulsorily draw diagonal cross lines on the remainin’ blank pages.

2. Any revealing of idenlifk ..on, appeal to evaluator and lot equations written eg,

**Fifth Semester B.E. Degree Examination, May/June 2010 Turbomachines**

Note: 1. Answer any FIVE full questions, selecting at/e. questions from Part — A and TWO questions 2. Use of Thermodynamic data hand book is m

**PART – A**

1. a. Define a turbo machine. Explain the principal components of a

b. With the help of h – s diagram, explain various efTicienci machines.

c. Obtain an expression for T, using dimensional analysis, where disc of diameter D rotating at a speed N in a fluid of viscosity ji flow.

2. (a) Representing all the components of velocity in a generalized turbo machine diagram, derive Euler turbine equation.

(b) Derive an expression for the utilization feeto^for an axial flow impulse turbine stage which has equiangular rotor blades, in terms of the fixed inlet blade angle and speed ratio and show the variation of utilization factor and speed ratio in the form of a graph.

(c) Determine the energy input to the fluid for a mixed flow pump for the given data : i) Inlet hub diameter = 7cm ii) Speed : 50 rps iii) Impeller tip diameter = 28cm iv) V_{wi} = Vrad.out* Assume that the relative velocity at the exit equals the inlet tangential blade speed.

3.(a)Define degree of reaction for an axial flow machine. Prove that degree of reaction for an ing constant velocity of flow) is given by R

(b)An axial compressor of 50% reaction design has blades with inlet and outlet angles of lively. The compressor is to produce a pressure ratio 5 : 1 with an overall efficiency of 87% when the inlet temp is 290K. The mean blade speed and axial constant throughout the compressor. Assume that blade velocity is 180m/sec input factor is 0.85. Find the number of stages required and the change of entropy.

4.(a)Derive an expression for an overall isentropic efficiency for finite number of stages of impression in terms of pressure ratio, stage efficiency, number of stages and ratio of specific heats for a compressor.

(b)In an axial flow compressor, air is taken at 1 bar and 288K. The delivery pressure of the compressor is 6.4 bars. The final temperature of air is 578K. Determine the following : i) Overall isentropic efficiency ii) Polytropic efficiency iii) Number of stages required if the actual temp, rise per stage is limited to 14.5K assuming that the polytropic efficiency is equal to the stage efficiency.

PART -B

5. a. With a neat skctch and velocity triangles, explain different vane shapes of the centrifugal compressor. Draw the inlet velocity triangle assuming Vyi = 0.0.

b. Write a note on the following for an axial flow compressor: i) Workdone factor ii) Radial equilibrium condition iii) Pressure ratio.

6. (a)Define the following terms for a centrifugal pump :

i) Manomctric head ii) Manometric efficiency iii) NPSH

(b)Derive an expression for the minimum starting speed for centrifugal pump.

(c)A centrifugal pump is running at 1000 rpm. The output vane angle the velocity of flow at outlet is 2.5m/scc. The discharge thro’ the the pump is working against the total head of 20m. If pump is 80%, determine i) diameter of the impeller ii)>

7. (a) Explain briefly a two stage pressure compounded impulse turbines and show the Pressure and velocity variations across the turbine.

b. Prove that the maximum rotor efficicncy is T)_{rm}a._{x} = Cos^{2} aj.

c. What is meant by reaction staging?

(50% reaction) turbine is given

8. (a)How do you classify the hydraulic turbines.

(b) Design a Pelton wheel for a head 103 kW shaft po efficiency 0.80. A Kaplan tis 85%. The s boss and show the pressure (06 Marks) gular rotor blades for impulse turbine ^{v} (06 Marks) imum stage efficiency of Parson’s m and speed 300 rpm. The Pelton wheel develops Icient of velocity 0.98, speed ratio 0.45 and overall

(c) A kaplan turbines develop 9000 kW under a head of 10m. Overall efficiency of the turbine ed on outer diameter is 2.2 and flow ratio 0.66. Diameter of the es tne outer diameter of the runner. Determine the diameter of the runner, specific speed of the runner.

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