Question Paper: Elements of Mechanical Engg. : Question Paper Jun 2012 - First Year Engineering (P Cycle) (Semester 2) | Visveswaraya Technological University (VTU)
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## Elements of Mechanical Engg. - Jun 2012

### First Year Engineering (P Cycle) (Semester 2)

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) (i) Fossil fuels are
(A) solid fuel
(B) liquid fuel
(C) gaseous fuel
(D) all of these
(1 marks)
1 (a) (ii) The water tubes in Babcock-Wilcox boiler are inclined to
(B) Improve convective heat transfer
(C) Accommodate the furnace
(D) Promote natural convection of water
(1 marks)
1 (a) (iii) With increases in pressure, the enthalpy of dry saturated steam
(A) Increases
(B) Decreases
(C) remains same
(D) first increases and then decreases
(1 marks)
1 (a) (iv) The specific volume of water, when heated at 0°C
(A) First increases and then decreases
(B) First decreases and then increases
(1 marks)
1 (b) List any four sources of energy, with suitable examples.(4 marks) 1 (c) Describe with a neat sketch, the working of a Badcock-Wilcox boiler. Indicate clearly the direction of flow of flue gases.(8 marks) 1 (d) Find the enthalpy of 1.0 kg of steam at 20 bar when
(i) it is wet with dryness fraction of 0.9
(ii) it is super heated with its temperature of 350°C.
[Take specific heat of super heated steam as 2.3 KL/KgK and properties of steam at 20 bar as ysat=212.4°C, hf=908.6kJ/kg, hfg=1888.6 kJ/kg ]
(4 marks)

2 (a) (i) _____ turbine is an example of impulse turbine.
(A) De-Laval
(B) Kaplan
(C) Francis
(D) Lawn sprinkler
(1 marks)
2 (a) (ii) A gas turbine as compared to a diesel engine takes longer time to accelerate to full speed because.
(A) gas turbine has lesser maximum pressure
(B) diesel engine has larger number of bearings
(C) gas turbine has larger rotating mass
(D) gas turbine needs no water cooling.
(1 marks)
2 (a) (iii) Kaplan turbine is efficient and preferred when
(A) Low head and low discharge is available
(B) low head and high discharge is available
(C) high head and high low discharge is available
(D) high head and high discharge is available.
(1 marks)
2 (a) (iv) Cooling water is not needed in
(A) gas turbine plant
(B) diesel engines plant
(C) steam turbine plant
(D) nuclear plant
(1 marks)
2 (b) With neat sketches, explain compounding of an impulse turbine.(6 marks) 2 (c) With a neat sketch, explain the construction and working of a closed cycle gas turbine plant.(6 marks) 2 (d) Classify water turbines.(4 marks)

3 (a) (i) The overall efficiency of an I.C. engines is
(A) mechanical efficiency
(B) brake thermal efficiency
(C) indicated thermal
(D) None of these
(1 marks)
3 (a) (ii) The air fuel ratio in petrol engine is governed by
(A) injector
(B) go vernor
(C) carburetor
(D) fly wheel
(1 marks)
3 (a) (iii) The ratio of speed of the camshaft to speed of the crank shaft in a four stroke cycle engine is
(A) 1:2
(B) 2:1
(C) 1:1
(D) none of these
(1 marks)
3 (a) (iv) For the same speed and power, the size of the flywheel of a stroke petrol engine is
(A) same as that of 2-stroke petrol engine.
(B) larger than that of 2-stroke petrol engine
(C) smaller than that of 2-stroke petrol engine
all of these
(1 marks)
3 (b) Explain with a neat sketch, working of a two stroke petrol engine.(6 marks) 3 (c) A single cylinder two stroke petrol engine develops 7.5 kW at 2500rmp. The mean effective pressure on the piston is 8 bar and mechanical efficiency is 80%. Calculate the diameter and stroke of the cylinder if stroke to bore ratio is 1.5. Also calculate the fuel consumption rate, if brake thermal efficiency is 28% the calorific value of the fuel is 43900 kj/kg.(10 marks)

4 (a) (i) An ideal refrigerant should have
(A) low freezing point
(B) low boiling point
(C) high latent heat of vapourization
(D) all of these
(1 marks)
4 (a) (ii) In vapour-absorption refrigeration system _____ is/are used to pressurize the refrigerent
(A) a pump and generator
(B) a compressor
(C) both A and B
(D) none of these
(1 marks)
4 (a) (iii) Refrigeration is a process of heat extraction from
(A) a hot body and delivered to a cold body with the help of external work
(B) a cold body and delivered to a hot body without the help of external work
(C) a cold body and delivered to a hot body with the help of external work
(D) a hot body and delivered to a cold body without the help of external work.
(1 marks)
4 (a) (iv) Air conditioning is a process of -
(A) control of temperature
(B) control of humidity
(C) control of cleanliness and air motion
(D) all of these
(1 marks)
4 (b) Define :
(i) COP of refrigeration
(ii) Ton of refrigeration
(4 marks)
4 (c) Draw a neat sketch of vapour compressor refrigeration system. Indicate the state of the refrigerant at all salient points and directions of flow of refrigerent.(6 marks) 4 (d) Describe room air conditioner with a simple sketch.(6 marks)

5 (a) (i) Which of the following parts is not present in lathe
(A) spindle
(B) knee
(C) bed
(D) slide
(1 marks)
5 (a) (ii) Which of the following operations can be carried out on lathe
(A) knurling
(B) facing
(D) all of these
(1 marks)
5 (a) (iii) _____ is the operation of enlarging a hole by a signle point cutting tool.
(A) reaming
(B) counter sinking
(C) boring
(D) all of these
(1 marks)
5 (a) (iv) Drilling machine can be specified based on
(A) max.dia. of drill
(B) spindle travel
(C) power of the motor
(D) all of these
(1 marks)
5 (b) With a neat sketch, explain tapper turning on lathe by swiveling of compound slide.(6 marks) 5 (c) Classify drilling machines.(4 marks) 5 (d) With neat sketchers, explain
(i) conuter sinking
(ii) conuter boring
(iii) reaming
(4 marks)

6 (a) (i) _____ is a machine tool that removes metal as the work is fed against a rotating multipointer cutter.
(A) lathe
(B) drilling machine
(C) shaping machining
(D) milling machines
(1 marks)
6 (a) (ii) In a horizontal milling machines, the rotating spindle is called as
(A) cutter
(B) yoke
(C) arbor
(D) over-arm
(1 marks)
6 (a) (iii) Which of the following are natural abrasives
(A) sand stone
(B) corundum
(C) diamonds
(D) all of these
(1 marks)
6 (a) (iv) _____ grinding produces flat surface
(A) cylindrical
(B) surface
(C) form
(D) none of these
(1 marks)
6 (b) Distinguish between up milling and down milling(4 marks) 6 (c) With a neat sketch, explain the working of vertical milling machine.(8 marks) 6 (d) List the applications and advantages of centreless grinding(4 marks)

7 (a) (i) Spot welding is an example of
(A) gas welding
(B) resistance welding
(C) TIG welding
(D) arc welding
(1 marks)
7 (a) (ii) Which of the following can act as a lubricant?
(A) oil
(B) grease
(C) graphite
(D) all of these
(1 marks)
7 (a) (iii) _____ is the property which enables oil to spread over and adhere to the surface of bearing
(A) oilness
(B) flash point
(C) specific gravity
(D) density
(1 marks)
7 (a) (iv) Which of the following is demerits of all bearing
(A) less friction
(B) requires less lubrication
(C) compact
(D) none of these
(1 marks)
7 (b) Distinguish between soldering, brazing and welding.(6 marks) 7 (c) List the basic requirements of good lubricant.(4 marks) 7 (d) Describe with a neat sketch, working of a bushed bearing.(6 marks)

8 (a) (i) Belt drives are prefered when the distance between the shaft centers is
(A) very small
(B) large
(C) any distance
(D) none of these
(1 marks)
8 (a) (ii) _____ gears connect two non-parallel, non-intersecting shaft which are usually at right angles.
(A) spur
(B) bevel
(C) worm
(D) none of these
(1 marks)
8 (a) (iii) In a clock mechanism _____Gear train is used to connect minute hand and hour hand.
(A) simple
(B) compound
(C) epicyclic
(D) none of these
(1 marks)
8 (a) (iv) Number of teeth on a wheel per unit of its pitch diameter is called