Question Paper: Turbo Machines : Question Paper Jun 2014 - Mechanical Engineering (Semester 5) | Visveswaraya Technological University (VTU)
0

Turbo Machines - Jun 2014

Mechanical Engg. (Semester 5)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1 (a) Define turbo machine. Classify them on basis of work transfer.(4 marks) 1 (b) Define the.following efficiencies of power absorbing turbo machines:
i) Total-to-total efficiency.
ii) Static-to-static efficiency
(6 marks)
1 (c) Explain specific speed and specific power.(4 marks) 1 (d) A model turbine 1 m in diameter acting under a head of 2 m runs at 150 RPM. Estimate the scale ratio if the prototype develops 20 MW under a head of 225 m with a specific speed Of 100.(6 marks) 2 (a) Define polytropic efficiency of a compressor(4 marks) 2 (b) What is reheat factor in a multi stage turbine? Prove that R.F is greater than unity(8 marks) 2 (c) In a three stage turbine the pressure ratio of each stage is 2 and the stage efficiency is75%. Calculate the overall efficiency and reheat factor(8 marks) 3 (a) Derive an alternate form of Euler's turbine equation and explain the significance of each energy components.(10 marks) 3 (b) Al a 50% reaction stage axial flow turbine, the mean blade diameter is 0.60 meter. The maximum utilization factor is 0.85 and steam flow rate is 12 kg/s. Calculate the inlet and outlet absolute velocities and power developed if the speed is 2500 RPM(10 marks) 4 (a) Derive an expression of theoretical head capacity relationship of radial outward flow devices(centrifugal machines).(10 marks) 4 (b) An inward flow reaction turbine has outer and inner diameter wheel as 1 m and 0.5 m respectively. The vanes are radial at inlet and discharge is radial at outlet and fluid enters the vanes at an angle of 10°. Assuming the velocity of flow to be constant and equal to 3 m/sec. Find: i) Speed of wheel, ii) Vane angle at outlet, iii) Degree of reaction(10 marks) 5 (a) What is compounding or staging? Name the different compounding method(4 marks) 5 (b) The data pertaining to an impulse turbine is as follows:
Steam velocity : 500 m/sec, blade speed : 200 m/sec, exit angle at moving blade : 25° measured from tangential direction, nozzle angle : 20° Neglecting the effect of friction when passing through blade passages. Calculate:
1)Inlet angle of moving blade
ii) Exit velocity and direction
iii) Work done per kg of steam
iv) Power developed
v) Diagram deficiency.
(16 marks)
6 (a) Obtain an expression for the work done per second by water on the runner a pelton Wheel and Hydraulic efficiency.(10 marks) 6 (b) A kapaln turbine has an outer diameter of 8 m and inner diameter as 3m and developing 30,000 KW at 80 RPM under a head of 12m. The discharged through the runner is 300 m2/sec. If the hydraulic efficiency is 95 % , determine:
i) Inlet and out let blade angles
ii) Mechanical efficiency
iii) Overall efficiency.
(10 marks)
7 (a) Derive the expression for the minimum speed for starting a centrifugal pump(12 marks) 7 (b) A centrifugal pump having outer diameter equal to two times inner diameter and running at 1200 RPM, words against a total head of 75m. The velocity of flow through the impeller is constant and equal to 3m/sec. The vanes are setback at an angle of 30° at outlet. If the outlet diameter of the impeller is 60cm and width at outlet is 5 cm. Determine:
i) Vane angle at inlet.
ii) work done per second by impeller.
iii) Manometric efficiency.
(8 marks)
8 (a) Explain the phenomena of surging, stalling and chocking in centrifugal compressor stage(6 marks) 8 (b) Draw velocity triangles at the entry and exit for the axial compressor stage.(6 marks) 8 (c) An axial compressor/blower supplies air to furnace at the rate of 3 kg/sec. The atmospheric conditions being 100 kPa and 310 K. The blower efficiency is 80% and mechanical efficiency is 85%. The power supplied to 30 kW. Estimate the overall efficiency and pressure developed in mm WG(8 marks)

ADD COMMENTlink
written 23 months ago by gravatar for Team Ques10 Team Ques10410
Please log in to add an answer.