Go Back   2019-2020-2021 StudyChaCha > StudyChaCha Discussion Forum > General Topics




  #2  
Old April 1st, 2014, 12:48 PM
Sashwat's Avatar
Super Moderator
 
Join Date: Jun 2011
Default Re: Model Paper for IES Mechanical Engg

Indian Engineering Services Mechanical Engineering stream paper has questions from following topics:

Thermodynamics
Heat Transfer and Refrigeration and Airconditioning
Fluid Mechanics
Fluid Machinery and Steam Generators
Theory of Machines
Strength of Materials
Machine Design
Engineering Materials
Production Engineering
Indusrial Engineering

Question paper:

PAPER–I
1. (a) Cylinder closed at both ends in thermal insulated from the surroundings. It contains a
movable thermally insulated, frictionless and leak proof piston. Initial the pressure, volume
and temperature on each side of the piston are p0, V0 and T0. The number of moles of gas of
each side is n. Heat is now slowly supplied to the gas on the left side of the piston by an
electric heating coil. As a result the gas on the left-hand side expands and displaces the piston
compressing the gas on the right-hand side until its pressure reaches (27/8) p0. If the ratio of
specific heats (cp/cv) is 1 and the molecular weight of the gas is M, determine, in term of n,
cv, M and T0
(i) the work done on the gas on the right hand side,
(ii) the final temperature of
the gas on the right hand side,
(iii) the final temperature of the gas on the left hand side and
(iv) the heat supplied to the gas on the left hand side. All assumptions made must be clearly
stated.

(b) Two reversible heat engines E1 and E2 are keep in series between a hot reservoir at a
temperature T1 of 600 K and a cold reservoir at a temperature T3 of 300 K. Engine E1
receives 500 kJ of heat from the reservoir at T1. The thermal efficiency of both the engines is
the same. Determine
(i) the temperature at which heat is rejected by engine E1 an received by
engine E2,
(ii) work done by engine E1,
(iii) world done by engine E2,
(iv) heat rejected by
engine E2 to the cot reservoir and
(v) the efficiency of the engines.

2. (a) Derive an expression for the air-standard efficiency of a Diesel cycle in terms of the
compression ratio (the ratio of the volumes at the beginning and end of the corn pression
process), the cut-off ratio (ratio of volumes at the end and beginning of the constant pressure
heat addition process) ad the ratio of specific heats at constant pressure and constant volume.

Draw a neat sketch of the cycle on the p-V diagram.
(b) An ideal Diesel engine operates with air as the working substance. The temperature and
pressure of the air the beginning of the compression process are 25°C and 0.005 bar. The
compression ratio is 18 and the cut-off occurs 6.5% of the expansion stroke.
(i) Draw the p-V and the T-s diagrams for the cycle indicating clearly each of the
processes;
(ii) Determine the pressure and temperature at the end of each process;
(iii) Determine the air-standard efficiency of the cycle assuming  = 1.4 for air;
(iv) The work done per cycle (assume cp = 10 kJ/kgK);
(v) The mean effective pressure.
3. (a) In a surface condenser air is removed from a careened-off section of the cooling tubes at a
temperature of 32°C. The absolute pressure of the steam entering the condenser is 0.0075
kgf/cm2. The mean temperature in the condenser is 36°C and the hot-well temperature is
30°C. Cooling water flowing at the rate of 100000 kg/h enters the condenser at 20°C and
leaves it at 32°C. The condensate formed is 2300 kg/h. Determine the vacuum efficiency, the
condenser efficiency, the state of steam entering the condenser, the mass of air present in the
condenser per m of its volume and the mass of air present per kg of unconcerned steam.
Assume the gas constant for air to be 29 3 (kgf-m)/(kg K).

MECHANICAL ENGINEERING


(b) A power plant operates on the regenerative cycle. Steam is supplied to the turbine at 80
kgf/cm2 and 100°C. It is exhausted to the condenser at 0.05 kgf/cm2. The plant has two feedwater
heaters where steam extracted from the turbine is directly mixed with the feed-water.
Steam is extracted from the turbine at pressures of 10 kgf/cm2 and 1.5 kgf/cm2. Determine the
mass of steam extracted at each of these pressures per kg mass flow at the turbine inlet, the
heat rejected in the condenser per kg mass flow at the turbine inlet, the cycle efficiency and
the gain in the cycle efficiency over a Rankine cycle operated under the same initial and final
conditions: Assume expansion of steam to be isentropic.
4. (a) Draw neat schematic diagrams of closed cycle and open cycle gas turbine engines. Label all
components and show the flow directions. Show the various thermodynamic processes of the
open and the closed cycle on the p-V and the T-s diagrams.
(b) Derive an expression for the optimum pressure ratio that will give the maximum power
output per unit mass flow in a Brayton cycle where the compressor and the turbine
efficiencies are and respectively, in terms of the maximum and minimum temperatures in the
cycle and the ratio of specific, heats at constant pressure and constant volume.
(c) The maximum and the minimum temperatures occurring in a closed cycle gas turbine plant
are 927°C and 37°C. The pressures at the outlet and the inlet of the compressor are 5 kgf/cm2
and 1 kgf/cm2. The compressor and turbine efficiencies are 80% and 88% respectively. Per kg
of air flow in the cycle determine the compressor work, the turbine work, the heat supplied to
the cycle and the net work done in the cycle. Also determine the thermal efficiency of the
cycle and the optimum pressure ratio for maximum power output for the given temperatures.
Assume  for air to be 1.4 and the specific heat at constant pressure to be 0.25 kcal/kgK.
5. (a) Describe with the help of a neat diagram the working of a vapor-compression refrigeration
plant. Sketch the corresponding temperature-entropy and pressure-enthalpy diagrams
indicating the directions of the various processes. Establish the expressions for the
coefficients of performance when the plant is operated as a refrigerator and as a heat pump.
How do superheating of the vapor at the entrance to the compressor and sub-cooling of the
liquid at the entrance of the throttle valve as also the frictional losses in the compressor affect
the performance of the machine? Indicate these effects on the T-s and the p-h diagrams.
(b) An ammonia refrigerator operates on the simple vapor compression cycle. The pressure of
liquid ammonia before throttling is 12 3 kgf/cm2 and its temperature is 272°C. The evaporator
pressure is 253 kgf/cm2. Ammonia gas leaves the evaporator at -95°C. The power input to the
compressor is 212 kW and the mass flow rate of ammonia is 27 kg/h. Determine the dryness
fraction of the gas after throttling, the heat absorbed per hour in the evaporator and the
coefficient of performance of the refrigerator. Sketch the cycle on the T-s and the p-h
diagrams. Properties of ammonia arc given below
Specific heat of liquid at 12.3 kgf/cm2 may be taken to be 1.14 kcal/kg°C and the specific
heat of superheated vapor at 253 kgf/cm2 may be taken to be 0.6 kcal/kg°C.
6. (a) Develop an expression for the heat flux passing radically through a long composite cylinder
of length L made up of three concentric layers of different materials and thicknesses in terms
of r1, the inside radius of the inner cylinder ; r2, r3 and r4, the outside radii of the inner, middle
and the outer cylinders respectively; their corresponding thermal conductivities k1, k2 and k3
the temperature T1 at the inner surface of the inner cylinder and the temperature 14 at the
outer surface of the outer, cylinder, T1 being greater than T4.
If the inside heat transfer coefficient of a fluid at temperature T1 flowing through this
cylinder is hi and the outside heat transfer coefficient of another fluid at temperature T2
flowing on the outside is h0, determine the overall heat transfer coefficient referred to the
inside surface.

(b) A thick-walled steel pipe of 168 mm outer diameter and 18 mm wall thickness is to be
provided with asbestos layer insulation. The pipe carries saturated steam at a pressure of 100
kgf/cm2. The velocity of steam in the pipe is 25 m/s. The temperature of the surroundings is
30°C.
The outside heat transfer coefficient may be taken to be 15 kcal/m2 h°C while the
inside heat transfer coefficients of the condensing steam may be taken to be 5000 kcal/m2
h°C. If the loss of steam by condensation is to be restricted to 0.5% of the mass flow per 100
meter length of the pipeline, determine the insulation thickness. Assume thermal conductivity
of steel to be 40 kcal/m h°C and the thermal conductivity of asbestos to be 0.15 kcal/m h°C.
Neglect effect of fouling.
7. (a) What is the basis for classifying hydraulic turbines? Illustrate your answer by giving names
of turbines falling under each category.
(b) An inward flow reaction turbine has a degree of reaction of 0.6. The peripheral velocity of the
vanes at entry is 15 m/s. The radial velocity of flow is constant at 3.2 m/s. The diameter of
the rotor at entry is twice that at the exit. Determine the blade angles at entry and exit
assuming that the absolute velocity of the water leaving the runner is in the radical direction.
(c) Discuss the phenomenon of cavitations in hydraulic turbines.
8. Write short notes on any four of the following:—
(a) Steam accumulator.
(b) Hydraulic ram.
(c) Orifice meter for flow measurement.
(d) Orsat apparatus for analyzing the product of combustion.
(e) Governing of steam turbines.
(f) Carburettor.

Time Allowed: 3 hours Maximum Marks: 200
Candidates should attempt any five questions
All Answers carry equal marks
Answers must be written in English.

PAPER - II
SECTION A
1. (i) Why are the shafts generally finished by grinding ‘while beams are used in as rolled
condition?
(ii) A helical spring is compressed axially. How does the spring wire get shear strain?
(iii) A piece of sheet metal strip can be easily bent, while the same strip when formed into a
channel shape becomes stiffer. Explain.
(iv) Distinguish between ‘fail safe’ and ‘safe fail’ concepts in machine design.
(v) What is the role of hunting tooth or hunting cog in gear transmission?
(vi) For increasing the stiffness of a helical spring, one should —
(a) increase/decrease diameter of spring,
(b) increase/decrease diameter of spring wire,
(c) increase/decreased length of spring or length of spring has no effect.
Write the correct answer for each of parts (a), (b) and (c).
(vii) Arrange the following sections in order of increasing torsional rigidity, see Fig. 1.
(viii) Give an approximate composition for each of the following alloys;
(a) High speed steel
(b) Stainless steel
(ix) State the von Mises hypothesis of yielding metals.
(x) Which of the following coolants are used machining of (a) aluminium and (b) cast iron? —
(a) Soap solution
(b) Kerosene
(c) Soluble oil solution
(d) EP cutting oil
(c) No coolant is used
(xi) A rubber band is elongated to double its initi length. Calculate its true strain.
(xii) List the followings in order of increasing mach nability:

MECHANICAL ENGINEERING

(a) Grey cast iron
(b) Mild steel
(c) Brass
(d) Stainless steel
(xiii) What is the relative consumption by volume oxygen and acetylene in oxy-acetylene welding
of mild steel?
(xiv) It is desired to measure the pouring temperature while casting grey cast iron. State a suitable
method.
(xv) Write four sentences distinguishing an N milling machine from a CNC milling machine.
(xvi) For which of the following cases NC machine can be used economically?
(a) Mass production
(b) Batch production
(c) Job-shop production
(xvii) State the name of frequency distribution use for estimating activity times for PERT. Give a
sketch of the distribution.
(xviii) In which of the following processes there is no wear of tool?—
(a) Ultrasonic machining
(b) Electrochemical machining
(c) Electro-discharge machining
(d) Grinding
(xix) With which of the following, value analysis is concerned?—
(a) Inventory control
(b) Quality control
(c) Fixing selling price of a product
(d) Attaching a cost value to every function fulfilled by a part in a product
(xx) What do AQL and AOQ stand for in quality control?
(xxi) What are ‘coated carbide cutting tools’ coated with?
(xxii) What are ceramic cutting tools made of?
(xxiii) The sizes of hole and shaft are respectively
Determine the maximum and minimum clearances, in the assembly of the two.
(xxiv) How are toothpaste tubes manufactured?
(xxv) For spur gears, state the relationship between nodule and circular pitch.
(xxvi) Give names of gear manufacturing processes, passed on generation of profile.
(xxvii) Give names of three methods used for forecasting in industry.
(xxviii)List the methods of ‘manufacturing seamless tubes.
(xxix) Write three main functions of coatings on the electric-arc welding electrodes.
(xxx) List three methods for experimental determine on of strains in the elastic members.
2. (a) A quick return mechanism of a shaper is shown in Fig. 2. The crank O1A rotates at 40 r.p.m.
in the counterclockwise direction. Determine the linear velocity of the cutting tool when the
crank 01 A is at 450 with the horizontal. All dimensions are given in the figure. 20

(b) A hollow shaft of 40 mm outer diameter and 25 mm inner diameter is subjected to a twisting
moment of 1200 kgf-cm, simultaneously; it is subjected to an axial thrust of 1000 kgf and a
bending moment of 800 kgf-cm. Calculate the maximum compressive and shear stresses. 15
3. (a) A .single plate clutch, effective on both sides, is required to transmit 33.5 HP at 3000 r.p.m.
Determine the outer and inner diameters of frictional surface if the coefficient of friction is
0.255, ratio of diameters is 1.25 and the maximum pressure is not to exceed 0.0l kgf/mm2.
Also, determine the axial thrust to be provided by springs. Assume the theory of uniform
wear.
(b) Two rotors of mass moment of inertia J1, J2 are connected to the ends of a shaft of length l,
diameter d and modulus of rigidity G. The shaft is appropriately supported to permit the
rotation of the shaft about its axis.
Find the natural frequency of the free torsional vibration of the system.
10
(c) A gear box for a drilling machine is to be designed to provide spindle speeds in the range of
100 r.p.m. to 640 r.p.m in 9 steps arranged in the geometric progression. Calculate the speeds
which may be rounded off to the nearest 5 r.p.m.
Sketch a schematic diagram of arrangement of gears.
10
4. (a) A circular bar of 500 mm length is supported freely at its two ends, It is acted upon by a
central concentrated cyclic load having a minimum value of 2000 kgf and a maximum value
of 5 00 kgf. Determine the diameter of bar by taking a factor of safety of 1.5, size effect of
0.85, surface finish factor of 0.9. The material properties of bar are given by: ultimate
strength of 65 kgf/mm2, yield strength of 50 kgf/mm2, and endurance strength of 35 kgf/mm2.
15
(b) Which effects are taken care of by Wahl correction factor for the helical springs?
10
(c) What do you understand by Computer Aided Design (CAD)? Explain with an example of
design of a spring.
10

SECTION B
5. (a) in a turning operation tool life T is given by VTn = constant. Determine the value of a if 50%
increase in cutting speed V reduces T by 20%.
(b) Draw a neat sketch of an enlarged surface profile and show clearly on it (i) mean surface (ii)
roughness height (iii) roughness width (iv) waviness height (v) waviness width.
Comment how mean surface can be shown.

10
(c) A stockist finds that monthly demand for a is 80 paisa the pens per month is 10% of the price
of pens. What is the economic ordering quantity?
8
(d) Work sampling studies are conducted to find the utilization of a machine. Out of 200
observations made, only 40 observations indicated the machine to be idle. Find the number of
observations to be made in order to satisfy 95% confidence to state the utilization of machine
with expected accuracy of ±5%.
6. (a) In an orthogonal cutting the following data is observed:
Uncut chip thickness = 035 mm
Cut chip thickness = 016 mm
Width of cut = 4 mm
Cutting speed = 30 m/min
Cutting force component parallel to machined surface = 150 kgf
Cutting force component normal to machined surface = 30 kgf
Rake angle of tool = 15°
Determine the horsepower required, shear plane angle, and average coefficient of friction on
the tool rake face.

(b) What do you understand by fibre-reinforced plastics? Explain rule of mixture for finding the
material properties of the composite. Also give two applications of these materials.
11
(c) In rolling of metals with flat rolls, explain the effect of following parameters on total rolling
load and on the pressure distribution contacting roll surface:
12
(i) Reduction in height of billet
(ii) Diameter of rolls
(iii) Coefficient of friction between rolls and billet.
7. (a) Maximize 3x1 + 10x2
3x1 + 6x2 < 24
2.5x1 + 1.25x2 < 10
3x1 + x2 > 0

(b) The network diagram of a project is given in Fig. 3 below. The activity times in days are
shown on the arcs.
Determine
(i) critical path and critical path time;
(ii) total float and free float of activity 1-4.
(iii) If due to unavoidable reasons activity (1-3) takes 6 days instead of 4, find the change
in the critical path.

(c) Six jobs are to be processed on two milling machines. All of them follow the same machine
sequence. Determine the optimal job sequence and minimum total expected time from the
data given below
__________________
Answered By StudyChaCha Member
Reply With Quote Quick reply to this message
Reply


Reply to this Question / Ask Another Question
Your Username: Click here to log in

Message:
Options

Forum Jump


All times are GMT +6.5. The time now is 02:13 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Friendly URLs by vBSEO 3.6.0 PL2

1 2 3 4 5 6 7 8 9