Question bank analysis of Applied Thermodynamics

Part A
Gas Turbine
22 What is meant by "thermal refinement" in relation to gas turbine plant? Discuss the
three thermal refinement strategies with appropriate diagrams.
22 Show that the efficiency of ideal gas turbine cycle with regenerator (Heat
exchanger) depends on both maximum cycle temperature and pressure ratio.
22 A gas turbine plant operates on Brayton cycle with lower and upper temperature
limits being 30°C and 910°C. The efficiencies of turbine and compressors are 80%
and 85% respectively for actual cycle. What would be the optimum value of
pressure ratio if the turbine is to be operated for maximum power output? Also
determine the plant efficiency for that calculated pressure ratio.
21 Show that the efficiency of the ideal gas turbine cycle only depends on the pressure
ratio.
21 Find out the condition of maximum and minimum work output for an ideal gas
turbine cycle.
21 A gas turbine plant operates on Brayton cycle with lower and upper temperature
limits being 289 K and 978 K. The efficiencies of turbine and compressors are 75%
and 75% respectively for actual cycle. What would be the optimum value of
pressure ratio if the turbine is to be operated for maximum power output? Also
determine the plant efficiency for that calculated pressure ratio.
21,17,14 Why are regenerators and intercoolers used in gas turbine?
21,19,17 Show that the optimum pressure ratio (Ropt) of a real gas turbine cycle depends on
the temperature ratio (1) and the isentropic efficiencies of both the turbine (ηT) and
the compressor(ηC).
21 A gas turbine plant operates on Brayton cycle with lower and upper temperature
limits being 285K and 975K. The efficiencies of turbine and compressors are 80%
and 80% respectively for the actual cycle. What would be the optimum value of
pressure ratio if the turbine is to be operated for maximum power output? Also
determine the plant efficiency for that calculated pressure ratio.
21,18,15,14,13 Distinguish between open cycle and closed cycle gas turbine. For a gas turbine,
show that the optimal pressure ratio is equal to the square root of the maximum
pressure ratio, i.e. (rp)opt = √(rp)max
21 A gas turbine plants operates on Brayton cycle with lower and upper temperature
limits being 300° K and 980° K. The efficiencies of turbine and compressor are 87%
and 83% respectively for actual cycle. What would be the optimum value of
pressure ratio if the turbine is to be operated for maximum power output? Also
determine the plant efficiency for that calculated pressure ratio.
19 In a gas turbine unit, air is compressed from 1 bar and 28°C through a pressure ratio
of 4:1. It is then heated to 1000°C in a combustion chamber and expanded back to
atmospheric pressure of 1 bar in the turbine. Heating value of the fuel is 40 MJ/kg.
The isentropic efficiencies of turbine and compressor are 85%. and 80%
respectively. For an air flow rate of 1.3 kg/s, determine (i) air-fuel ratio of the
 turbine plant, (ii) overall efficiency of the plant, and (iii) back work ratio. Take Cp
1.005 kJ/kg K and y= 1.4 both for air and gases.
19 Show that in case of Person's turbine the degree of reaction is half.
19,18,16,15,14 Why reheat factor is always greater than unity?
18 Discuss the relative advantages and disadvantages of closed and open cycle gas
turbine.
18 What are the requirements of a good combustion chamber in open cycle gas
turbine?
18 A gas turbine plant operates with lower and upper temperature limits being 27°C
and 920°C. What would be the optimum pressure ratio, if the turbine is to be
operated for maximum power output? For the pressure ratio thus calculated,
determine the plant efficiency and work ratio.
18 The blade speed of a single ring impulse blading is 300 m/sec and the nozzle angle is
20°. The isentropic heat drop is 473 kJ/kg and the nozzle efficiency is 0.85. The
blade velocity coefficient is 0.7 and the blades are symmetrical. Draw the velocity
diagram and calculate the followings for a muss flow rate of 1 kg/sec.
(i) The axial thrust on the blading. (ii) Steam consumption rate for a mechanical
efficiency of 90%. (iii) Blade (Diagram) efficiency and (iv) Energy loss in blade
friction.
18 From the expression for blade outlet angle, show that in reaction turbine both
impulse and reaction part contribute to the final absolute velocity?
17 In a gas turbine plant, air at 15°C is compressed from 1 bar through a pressure ratio
4: 1. It is then heated to 700°C in the combustion chamber and expanded back to
atmospheric pressure of 1 bar in the turbine. Calculate the cycle efficiency and work
ratio if a perfect heat exchanger is used. Assume the isentropic efficiencies of
turbine and compressor are 85% and 80% respectively.
16 Describe the means of improving the efficiency and output of a gas turbine working
on C simple Brayton cycle.
16 How the cooling is done in gas turbine?
16 "Although the efficiency of simple gas turbine is independent of the maximum
temperature in the cycle, but the performance of the real cycle is dependent on the
same." Justify the statement.
16 A gas turbine plant operates with lower and upper temperature limits being 27°C
and 900°C. What would be the optimum pressure ratio? if the turbine is to be
operated for maximum power output? For the pressure ratio thus calculated,
determine the plant efficiency and work ratio.
16 The mean diameter of the blades of an impulse turbine with a single row wheel is
105 cm and the speed 3000 rpm. The nozzle angle is 18°. the ratio of blade speed to
steam speed is 0.46 and the ratio of the relative velocity at outlet from the blades
to that at inlet is 0.85. The outlet angle of the blades is to be made 3" less than the
inlet angle. The steam flow is 8 kg/see. Draw the velocity diagram for the blade and
determine
(i) Resultant thrust on blades.
(ii) Tangential thrust on blades,
(iii) Axial thrust on blades.
(iv) Hp developed in blades and
(v) Blading efficiency
15 How one can improve the work output of a closed cycle gas turbine? Explain your
07 answer with the help of T-S diagram.
14 Calculate the power of installation, air fuel ratio, back work ratio and overall
efficiency 18 of a gas turbine working on Joule cycle for the following conditions:
(i) Inlet condition of compressor is 1.5 bar, 350K, (ii) Inlet temperature of turbine is
750K. (iii) Pressure ratio is 4.0, (iv) Air flow rate is 1.25 kg/sec, (v) Heating value of
fuel used is 41,000 kJ/kg. (vi) ηT = 85% and ηC = 80%.
For air y = 1.40 and Cp = 1.005 kJ/kgK and for gases y = 1.35 and C, = 0.98 kJ/kgK
13 In a gas turbine plant, air is compressed from 1 bur and 20°C through a pressure
ratio 4:1. It is then heated to 700°C in the combustion chamber and expanded back
to atmospheric pressure of 1 bar in a turbine. Calculate the cycle efficiency and the
work ratio if perfect heat exchanger is used. The isentropic 80% and -85%.
12 How the efficiency of a single cycle gas turbine can be improved by employing heat
exchanger? Explain briefly with neat sketch.
12 How cooling is done in a gas turbine?
12 In a gas turbine plant, air is compressed from 1 bar and 20°C through a pressure
ratio of 4:1. It is then heated to 700°C in the combustion chamber and expanded
back to atmospheric pressure of 1 bar in a turbine. Calculate the cycle efficiency
and the work ratio if a perfect heat exchanger is used. The isentropic efficiencies of
the turbine and compressor are 85% and 80% respectively. Note

Steam Turbine
22,21,19,15,14,13 Why staging is done in steam turbine? Describe the principal features of
pressure and velocity staging.
22,19,17,16,15,14,13 Show that for frictionless and symmetrical blading, the maximum diagram
efficiency of an impulse turbine can be expressed as, ηdmax = cos2α, where α is
the nozzle angle.
22 Steam issues from the nozzles of a de Laval turbine with a velocity of 920
m/sec. The nozzle angle is 20°, the mean diameter of the blade is 26 cm and
speed of rotation is 20,000 rpm. The mass flow through the turbine nozzles
and blading is 0.2 kg of steam per second. If the friction loss in the blade
channels is 34% of the kinetic energy corresponding to the relative velocity at
inlet to the blades, draw the velocity diagram and calculate the followings:
(i) Velocity of whirl, (iii) Work done on the blades,
(ii) Tangential and axial forces on blades, and (iv) Blade efficiency.
22,21,19,17,15 What is meant by degree of reaction? Draw and explain the condition curves
in h-s diagram for a multi-stage turbine. Why is it important in turbine design?
22,19,18,17,16,15 What are the different internal losses encountered in steam turbine? How disc
friction losses are estimated? How blade windage is accounted?
22,20 From the expression of blade outlet angle, show that in reaction turbine both
impulse and reaction part contribute to the final absolute velocity.
22,21,19,17,16 What are the different types of plate blade sections?
21,12 Describe the velocity diagram of an impulse turbine, which is a single stage
steam turbine.
21,20,18 If the fixed nozzle angle is α, the blade inlet and outlet angles are β1 and β2,
respectively and the blade factor is K, then show that the diagram efficiency
is:
𝑐𝑜𝑠2 𝛼 cos 𝛽2
ηb=(1+kC) where C=
2 cos 𝛽1
21 Steam issues from the nozzles of a de Laval turbine with a velocity of 915
m/sec. The nozzle angle is 20°, the mean diameter of the blade is 25 cm and
speed of rotation 20000 rpm. The mass flow through the turbine nozzles and
blading is 0.2 kg of steam per second. If the friction loss in the blade channels
is 33% of the kinetic energy corresponding to the relative velocity at inlet to
the blades, draw the velocity diagram and calculate the following:
(i) Velocity of whirl, (ii) Tangential and axial forces on blades, (iii) Work done
on blades per second, (iv) Horse-power of wheel, and (v) Blade efficiency.
21,19,18,16,12 Why is turbine governing necessary?
21 Explain briefly the nozzle control governing system.
21 A single stage impulse turbine rotor has a diameter of 1.2 m running at 3500
rpm. The nozzle angle is 18 and blade speed ratio is 0.9. The outlet angle of
the blade is 3o smaller than that of the inlet. The steam flow rate is 4 kg/sec.
Determine- (i) Velocity of whirl, (ii) Axial thrust on the bearing, (iii) Blade
angle, and (iv) Power developed.
21,12 For frictionless and symmetrical blading show that the maximum rate of doing
work corresponding to maximum diagram efficiency can be expressed as
2𝐶𝑏 2
Wmax= where Cb is the speed at the mean height of the blade.
𝑔𝑐
21,20 What are the different losses encountered in steam turbine? Explain how
profile blades eliminate losses in the turbine?
21,18,16 Describe the principles of action of steam turbine with neat sketches.
21,19,18,17,16,15,12 Mention five differences between impulse turbines and reaction turbines.
21 Steam with absolute velocity of 330 m/sec enters the stage of an impulse
turbine provided with a single row wheel. The nozzles are inclined at 20° to
the plane of the wheel. The blade rotor with a diameter of 92 cm rotates with
a speed of 3100 rpm. Find (i) suitable inlet and outlet angles for the moving
blade so that there is no axial thrust on the blade. It may be assumed that the
friction in blade passage is 18% of the kinetic energy corresponding to the
relative velocity at inlet to blades; (ii) power developed in blading for a steam
flow of 1 kg/sec; and (iii) kinetic energy of steam finally leaving the stage.
21 Steam with absolute velocity of 325 m/s enters the stage of an impulsive
turbine provided with a single row wheel. The nozzles are inclined at 21° to
the plane of wheel. The blade rotor with diameter 90 cm rotates with a speed
of 2900 rpm. Find: (i) suitable inlet and outlet angles for the moving blade so
that there is axial thrust on the blade. It may be assumed that the friction in
blade passage is 20% of the kinetic energy corresponding to the relative
velocity at inlet to blades, (ii) power developed in blading for a steam flow of 1
kg/s; and (iii) kinetic energy of steam finally leaving the stage.
21,14 What is meant by reaction turbine? Show that the maximum blade efficiency
2𝑐𝑜𝑠2 𝛼
of a reaction turbine can be expressed as 1+𝑐𝑜𝑠2 𝛼 where 𝛼 is the inlet angle of
the steam to the blade.
20 Derive an expression for thermal efficiency of a gas turbine cycle.
20 What is the condition of maximum work output? Explain it for an ideal gas
turbine cycle.
20 A gas turbine plant operates on Brayton cycle with lower and upper
temperature limits being 298°K and 978°K. The efficiencies of turbine and
compressor are 85% and 80% respectively for actual cycle. What would be the
optimum value of pressure ratio if the turbine is to be operated for maximum
power output? Also determine the plant efficiency for that calculated
pressure ratio.
20 Steam with absolute velocity of 320 m/sec enters the stage of an impulse
turbine provided with a single row wheel. The nozzles are inclined at 20° to
the plane of wheel. The blade rotor with diameter 92 cm rotates with a speed
of 3000 rpm. Find: (i) suitable inlet and outlet angles for the moving blade so
that there is no axial thrust on the blade. It may be assumed that the friction
in blade passage is 20% of the kinetic energy corresponding to the relative
velocity at inlet to blades; (ii) power developed in blading for a steam flow of 1
kg/sec; and (iii) kinetic energy of steam finally leaving the stage.
19 Derive an expression for thermal efficiency of a regenerative cycle.
19 Compare and contrast velocity staging with pressure staging.
19 Describe the principle of action of steam turbine.
19 Steam with absolute velocity of 360 m/s enters the stage of an impulse
turbine provided with a single row wheel. The nozzles are inclined at 22° to
the plane of wheel. The blade rotor with diameter 100 cm rotates with speed
of 2850 rpm. Assume that there is no axial thrust on the blade and the friction
in blade passage is 20% of the kinetic energy corresponding to the relative
velocity at inlet to the blades. The steam flow rate in the system in the system
is 1.2 kg/s. Calculate (i) power developed in the blading, (ii) inlet and outlet
angles of the moving blades, and (iii) kinetic energy of the steam finally
leaving the blade.
19,18,13 What are the methods mainly used for governing the steam turbine?
19,17,16 Explain in details throttle control governing with neat sketch.
17 Steam issues from the nozzles of an impulse turbine with a velocity of 1070
m/sec. The nozzle angle is 20°, the mean blade velocity is 366 m/sec, and the
inlet and outlet angles of the blades are equal. The mass of steam flowing
through the turbine per hour is 820 kg. Calculate- (i) the blade angles, (ii) the
relative velocity of the steam entering the blades, (iii) the tangential force on
the blades, (iv) the horse power developed and (v) the blade efficiency.
16,15,14 Define line of condition and reheat factor applicable for multi stage impulse
turbine?
15 Draw the pressure and velocity profile of steam both for velocity and pressure
compounding.
14 Steam with an absolute velocity of 360 m/sec enters the stage of an impulse
turbine with 1 single row wheel. The nozzles are inclined at 20° to the plane of
the wheel. The blade rotor with a diameter of 90 cm rotates with a speed of
3000 rpm. Assume no axial thrust on the blade and the friction in blade
passages is 20% of the kinetic energy corresponding to relative velocity at inlet
to blades. For steam flow rate of 1.5 kg/sec, determine (i) inlet and outlet
 angles of moving blades, (ii) power developed in the blading, (iii) KE of steam
finally leaving the stages. For air Cp = 1.005 kJ/kgK and γ = 1.40.
14 Air expands under reversible adiabatic conditions in a nozzle from 6 bar 600°C
to a final pressure of 1.1 bar. Determine what type of nozzle is to be used for
the above conditions? Calculate the critical velocity and air flow rate if the
minimum nozzle diameter is 1.5 cm. Assume for air y 1.40.
13 How one can improve both work output and efficiency of a plant? Explain
your answer the help of T-s diagram.
13 The blade speed of a single ring of impulse blading is 300 m/sec and nozzle
angle is 20°. The isentropic heat drop is 450 kJ/kg and nozzle efficiency is 88%.
The blade velocity coefficient is 0.78 and the blades are symmetrical. Draw the
combined velocity triangle and calculate the following for a mass flow rate of
1.1 kg/sec.
(i) Steam consumption rate for a mechanical efficiency of 85%
(ii) Maximum blade efficiency
(iii)Axial thrust on the blading and
(iv)Energy loss in the blade friction
12 The stage of an impulse turbine provided with a single row wheel where
steam enters at an absolute velocity of 300 m/sec. The nozzle through which
steam is supplied is 22 to the plane of wheel. The blade rotates with a speed
of 3600 rpm. The diameter of the rotor blade is 100 cm. Determine the (i) inlet
and outlet angles for the moving blades so that there is no axial thrust on the
blade. Assume that friction in the blade passages is 20% of the kinetic energy,
corresponding to relative velocity at inlet to blades, (ii) Power developed in
blading for a steam flow rate of 1.5 kg/sec and (iii) the Kinetic Energy of steam
finally leaving the stage.
12 Define overall efficiency of steam turbine. Show that overall efficiency of
𝛴Δh
steam turbine can be expressed as η0= ΔΗ where symbols have their usual
meanings.
12 Write down the salient points of difference between impulse turbine and
reaction turbine.

Jet Propulsion
22,19,18,17,15, What are the essential differences between turbo-jet and turbo-prop engines? With
14,12 neat sketch, describe the working principle of Ramjet engine.
22 A turbo-jet engine flying at a speed of 780 km/hr consumes air at the rate of 38
kg/sec. Given the enthalpy change for the nozzle is 200 kJ/kg, velocity coefficient is
0.96, air-fuel ratio is 73, heating value of the fuel is 45 MJ/kg and combustion
efficiency is 95%; calculate: (i) Thrust specific fuel consumption, (ii) Thermal
efficiency of the plant, (iii) Propulsive power, and (iv) Overall efficiency.
21,17 Derive an expression for overall efficiency of a jet propulsion unit.
21 Describe the working principle of turbo-jet engines. Also mention its advantages.
21 A turbo-jet engine flying at a speed of 750 km/hr consumes air at the rate of 40
kg/sec. Given the enthalpy change for the nozzle is 180 kJ/kg; velocity coefficient is
 0.95, air-fuel ratio is 75, heating value of the fuel is 42 MJ/kg and combustion
efficiency is 94%; calculate: (i) Thrust specific fuel consumption, (ii) Thermal
efficiency of the plant, (iii) Propulsive power, and (iv) Overall efficiency.
21 A turbo-jet engine flying at a speed of 700 km/hr consumes air at the rate of 40
kg/sec. Given the enthalpy change for the nozzle is 170 kJ/kg, velocity coefficient is
0.93, air-fuel ratio is 68, heating value of the fuel is 42 MJ/kg and combustion
efficiency is 94%. Calculate: (i) thrust specific fuel consumption; (ii) thermal
efficiency of the plant; (iii) propulsive power and (iv) overall efficiency.
21 A turbo-jet engine flying at a speed of 800 km/hr consumes air at the rate of 42
kg/sec. Given the enthalpy change for the nozzle is 200 kJ/kg, velocity coefficient is
0.95, air-fuel ration is 70, heating value of the fuel is 43 MJ/kg and combustion
efficiency is 95%; calculate - (i) thrust specific fuel consumption, (ii) thermal
efficiency of the plant, (iii) propulsive power, and (iv) overall efficiency.
16,15,13 With a neat sketch describe the working principle of pulse jet engine. What is
meant by after burning?
16 A turbojet engine flying at a speed of 875 km/hr consumes air at the rate of 48
kg/sec. Calculate:
(i) The jet exit velocity, the enthalpy changes for the nozzle is 195 kJ/kg and the
velocity coefficient is 0.95. (ii) Fuel flow in kg/hr and thrust specific fuel
consumption assuming air fuel ratio is 82, (iii) The propulsive power and the thrust
horse power.
15 A turbojet engine flying at a speed of 810 km/hr. consumes air at the rate of 45
kg/sec. Calculate:
(i) Jet exit velocity, the enthalpy changes for the nozzle is 44.5 kcal/kg and the
velocity coefficient is 0.95.
(ii) Fuel flow in kg/hr and thrust specific fuel consumption assuming that air fuel
ratio is 80.
(iii)Thermal efficiency of plant given n combustion -95% and calorific value of fuel
used 10500 kcal/kg.
(iv)Propulsive power and thrust H.P.
(v) Propulsive η and overall η.
14 A jet propulsion engine having two jets and working on turbojet system has a
velocity of 15 720 km/hr at an altitude 12000 meters. The density of air at the same
altitude is 0.172 kg/m3. The drag of the plane is 6300N and the propulsive
efficiency of the jets is 48%. If the overall efficiency of the turbine plant is 20% and
the heating value of the fuel is 46 MJ/kg, then calculate (i) Volume of air
compressed, (ii) Diameter of the jet in cm, (iii) Thrust power, (iv) Air fuel ratio of the
unit.
13 A turbojet has a speed of 840 km/hr while, flying at an altitude of 12,000m. The
propulsive efficiency of the jet is 50% and the overall efficiency of the turbine plant
is 18%. The density of air at 12,000 m altitude is.0.177 kg/m3. The drag on the plane
is 6250N. The calorific value of fuel is 44,000 kJ/kg. Calculate the
(i) Power output of the unit
(ii) Absolute velocity of the jet and
(iii) Diameter of the jet.
12 A turbo jet has a speed of 800 km/hr while flying at an altitude of 12,000 m. The
propulsive efficiency of the jet is 48% und the overall efficiency of the turbine plant
 is 20%. The density of air at altitude of flying is 0.179 kg/m2. The drag on the plane
is 6100 N. The calorific value of the fuel is 42 MJ/kg. Calculate (1) Power output of
the unit and (ii) Diameter of the jet.

Rocket Propulsion
2𝑞
22,21,18,16,15, Show that the efficiency of rocket propulsion can be expressed as ηrocket=1+𝑞2
14,13,12
21,20,19,18,17,14 What is meant by restricted and unrestricted burning of propellant in rocket
engine?
20,19,18,17,13 What are the differences between jet propulsion and rocket propulsion?
18 What is meant burning?
12 What is meant by propellant? What are the basic requirements of rocket
propellant?
 Part B
Introduction & Overview
22 What is the physical significance of volumetric efficiency? How inlet valve timing
and engine speed affect volumetric efficiency?
22 With the help of indicator diagram, explain (i) Indicated work/cycle, and (ii)
Pumping work/cycle.
22 The air flow to the four cylinder four stroke petrol engine is measured by means
of 7 cm diameter sharp-edged orifice with Ca = 0.65. During the engine test on
the test bed, the following data were recorded:
bore = 11 cm, stroke = 13 cm, engine speed = 2200 rpm, brake power 38 kW, fuel
consumption = 7 kg/hr, heating value of fuel = 42.5 MJ/kg. The pressure across
the orifice is 5 cm of water, atmospheric temperature and pressure = 22°C and 1
bar, respectively. Calculate- (i) Thermal efficiency on the basis of brake power, (ii)
Brake mean effective pressure, (iii) Volumetric efficiency based on free air
condition.
21,19 What is meant by pumping loss in relation to SI engine? "Pumping loss is
minimum for an engine operating at wide open throttle (WOT) condition"--
Explain with necessary diagrams.
21 The air flow to the four cylinder four stroke petrol engine is measured by means
of 8 cm orifice with Ca=0.70. During test on the engine, the following data were
recorded: bore x stroke = 12 cm x 13 cm, engine speed = 1250 rpm, brake torque
140 Nm, fuel consumption 5.9 kg/hr, heating value of fuel 45 MJ/kg, head across
orifice = 5.9 cm of water, ambient temperature and pressure 25°C and 1.013 bar,
respectively. Calculate- (i) Thermal efficiency, (ii) Brake mean effective pressure,
(iii) Volumetric efficiency. based on free air condition.
21 Discuss the reasons for deviation of actual valve timing from the theoretical one.
Also, mention the consequences of valve overlapping.
21 Discuss the reasons for early opening and late closing of both inlet valves and
exhaust valves with appropriate diagrams. Also justify the valve overlapping.
21,20 What is meant by "pumping loss"? "Pumping loss could be minimized in direct
injection spark ignition (DISI) engine"- explain with necessary diagrams.
21,20 The air flow to a 4-cylinder 4-stroke oil engine is measured by means of a 6 cm
diameter orifice with Ca0.65. During a test on the engine the following data were
recorded: Bore x Stroke = 11cm x13 cm, engine speed = 1300 rpm, brake torque =
145 N.m, fuel consumption = 4 kg/hr, heating value of the fuel = 43 MJ/kg, head
across the orifice = 6 cm of water, ambient temperature and pressure = 25°C and
1 bar respectively. Calculate - (i) Thermal efficiency on the basis of brake power.
(ii) Brake mean effective pressure and (iii) Volumetric efficiency based on free air
condition.
21 Draw and explain the standard performance curves for IC engine.
19,17 Define ihp, bhp, fhp and mep.
19 Define rich combustion and lean combustion. Draw the actual valve timing
diagram for SI engine and justify the valve overlapping.
19 The air flow to the four cylinder four stroke petrol engine is measured by means
of 7.5 cm diameter sharp-edged orifice, Ca =0.60. During the engine test on the
 test bed the following data were recorded: bore = 11 cm, stroke = 13 cm, engine
speed 2250 rpm, brake power 36 kW, fuel consumption 10.5 kg/hr, calorific value
of the fuel = 42 MJ/kg. The pressure across the orifice is 4.1 cm of water,
atmospheric temperature and pressure are 15 °C and 1.013 bar. Calculate - (i)
thermal efficiency on the basis of brake power, (ii) brake mean effective pressure.
18 What are the parameters to be recorded during engine performance test and
what are the parameters to be discussed on performance study? Explain.
18 Draw bhp, bsfc and BThEff curve versus engine speed. Discuss variation of bsfc
with load (bhp).
18 The air flow to the four cylinder four stroke petrol engine is measured by means
of 7.5 cm diameter sharp-edged orifice, Ca=0.60. During the test on the engine
the following data were recorded:
Bore=11cm, stroke=13cm. engine speed-2250rpm, brake power 36kW. fuel
consumption 10.5 kg/hr, calorific value of the fuel-42.000kJ/kg. pressure drop
across the orifice is 4.1cm of water. Atmospheric temperature and pressure are
15°C and 1.013 bar: Calculate; (i) Thermal efficiency on the basis brake power. (ii)
Brake mean effective pressure. (iii) Volumetric efficiency based on free air
condition.
17 Draw the characteristic curves for a variable speed engine test and explain.
17 How ihp could be measured in the laboratory? Explain your answer with the help
of an indicator diagram.
17 The air flow to a 4-stroke 4-cylinder petrol engine is measured by means of a 7.5
cm diameter sharp-edged orifice with ca=0.60. During the engine test on the test
bed the following data were recorded:
Bore 11 cm, stroke = 13 cm, engine speed = 2250 rpm, brake power = 36 kW, fuel
consumption 10.5 kg/hr, calorific value of fuel 42500 kJ/kg. The pressure across
the orifice is 4.1 cm of water, atmospheric temperature and pressure are 17°C
and 1.013 bar; calculate- (i) thermal efficiency on the basis of brake power, (ii)
brake mean effective pressure.
16 Draw the important performance parameters of SI engine against speed of the
engine and describe it.
16 What are the physical interpretation of sfc, mep and volumetric efficiency.
16 The following observations were recorded during a test on a single cylinder stroke
cycle oil engine having a bore of 20 cm and stroke of 50 cm. The duration of trail
was one hour. Air sucked by the engine has a temperature of 25°C. Calculate:
(i) Indicated power. (ii) Brake power. (ii) Brake thermal efficiency and (iv)Draw up
a heat balance on hour basis.
Observations of test: (i) Fuel Consumption 12.0 kg (ii) RPM = 600 (iii) Calorific
value of fuel= 41 500 kJkg (iv) Вmер= 5 bar (v) Net brake load= 2.0 KN (vi) Brake
drum diameter= 1.75 m (vii) Brake rope diameter= 1.8 cm (viii) Flow rate of
cooling water in the jacket=650 kg/hr (ix) Rise in temperature of jacket cooling
water= 50°C (x) Air flow as measured = 300kg/hr (xi)Temperature of exhaust gas
=425°C (xii) Specific heat of exhaust gas = 0.98 KJ-kg.K
15,14,13 What is meant by the performance test of IC engine. What are the major
parameters tested in the lab during performance study?
15,13 Explain the performance of SI engine with the help of Hook's curve
15 The following data were collected during the test of a single cylinder oil engine
working on four-stroke cycle. Calculate:
(i) BHP, (ii) Mechanical Efficiency and (iii) Indicated thermal efficiency of the
engine.
Data recorded are as follows:
Bore= 12 cm, RPM=1500, Area of indicator diagram = 4 cm2, Stiffness of spring =
12, Spring balance reading=5 kg, Diameter of brake wheel 64 cm, Stroke 20 cm,
Fuel consumption 0.15 kg/BHP-hr, Length=6 cm, Dead load 35 kg, Calorific value
of fuel used = 44000 kJ/kg, Rope diameter = 3 cm.
14 Draw the trend curves for the performance of SI engine and explain it in details.
14 A 4-stroke, 6-cylinder SI engine has bore and stroke of 7.5cm x 10.0cm. the
clearance volume is 68 cm3. It runs at a speed of 3600 rpm. When tested on load
it develops a torque of 65 N-m. The calorific value of fuel used was 42000 kJ/kg.
Mechanical efficiency of the engine is 80% and relative efficiency based on brake
thermal efficiency is 50%. For air take y= 1.40. Calculate the specific fuel
consumption (sfc) and the brake mean effective pressure (Bmep).
13 The following data were recorded during a trial on 4-stroke diesel engine.
(i) Mechanical efficiency; (ii) Brake thermal efficiency; (iii) Brake specific fuel
consumption and (iv) Cooling loss of the engine.
Diameter of the piston= 12cm
No. of cylinder=6
Stroke length=18 cm
Imep=0.65 Mpa
Brake torque=180.5 N-m
Speed=1900 rpm
No. of explosion=920 per min
Fuel consumption=12 kg/hr
Calorific value of fuel=42,000 kJ/kg
Flow rate of jacket cooling water=900 kg/hr
Rise in temperature of cooling water=40°C
Sp. Heat of cooling water= 4.18 kJ/kg-K
12 A 4-stroke cycle oil engine having bore and stroke of 18x21cm was tested in a
laboratory for a period of 30 minutes and following information were recorded.
Calculate IHP, BHP, Mechanical efficiency and prepare a heat balance sheet for
the engine.
RPM=450
Mep=3.0 bar
Diameter of brake drum=1.5 m
Net brake load=60 kg.
Oil consumption-3.0 kg
Heating value of oil = 41,000 kJ/kg
Flow of cooling water=420 kg
Increase of temperature of Jacket water = 20°C
Atmospheric temperature=28°C
Temperature of exhaust gas entering the calorimeter=300°C
Temperature of exhaust gas leaving the calorimeter=210°C
Quantity of water passing through the calorimeter = 400 kg
Rise in temperature in the calorimeter = 12°C
 SI Engine

22,21,20,17,16,13 What are the engine variables that control the flame speed of an IC engine?
22,21,20 How spark timing influences MBT? Discuss the factors that increase the tendency
to knock in SI engine.
19,18,12 What are the causes of surface ignition? Explain the origin of knock in SI engine
with the help of auto-ignition theory.
21 What is meant by surface ignition and MBT-timing? "Pre-ignition is more harmful
than post-ignition" - Explain.
21,19 What are meant by MBT, Abnormal combustion and Flame front? Which factors
do influence the MBT timing?
21 What are the causes of surface ignition? Explain the following terms (i) Pre-
ignition, (ii) Post-ignition, (iii) End gas autoignition.
18,15,14,13,12 What is combustion? Describe the terms: (i) pre-ignition. (ii) auto-ignition and (iii)
self-ignition.
18,17,15,14,12 Distinguish between knock and detonation.
16,13 Define knock and detonation. Describe in details the factors which are
responsible for generating knock in Sl engine.
15 Briefly describe the effect of engine variables on flame speed, and detonation.
15,13 Describe the methods to reduce knock in SI engine.
15 Develop an expression of air fuel ratio (AFR) for SI engine generally used to
calculate the same.
14 What is meant by combustion and ignition limits. Briefly describe.
14 Show that the temperature of end gas is lower than that of spark plug.

CI Engine
22,21,20 Define the following terms:
(i) Squish, (ii) Tumble, (iii) Swirl, and (iv) Blow-by.
22,21 How knock in Cl engine differs from that in SI engine? A good SI engine fuel is a
bad CI engine fuel." - Explain with appropriate figures.
22,21,20,18,14,12 What are the different methods of generating swirl in CI engine? Describe
compression swirl and induction swirl with their advantages and disadvantages.
21 Distinguish rich combustion from lean combustion. Generally a CI engine
operates with lean mixture-Explain.
21 What are the major differences in combustion process of SI engine and Cl
engine? Explain with appropriate diagrams.
21,20 How does ignition delay in SI engine differ from that in CI engine? Explain the
different stages of combustion in CI engine with the help of "heat release rate-
crank angle" diagram.
21,20,19,18,17,14 "Factors tending to increase detonation in SI engine tend to reduce knocking in CI
engine" -justify the above statement.
19 What are the variables responsible for reducing knock in diesel engine?
19,15,14,13 What is delay period? Write in brief, the factors affect delay period?
17 What is delay period? Describe the details of delay period of a CI fuel in the
engine cylinder.
16,13 Make a comparison of combustion phenomena of SI and CI engine.
16 Explain how auto ignition reduces the delay period of an engine.
14 What are the methods of generating air swirl in CI engine?
12 Write down the importance of swirl in CI engine.

Combustion Chamber
21,19 Write the advantages of 'M'-combustion chamber. Why low ignition quality fuel can
be used in very large, slow speed Cl engine?
21,20 What are the requirements of designing the combustion chamber of a CI engine for
high thermal efficiency?
18,14,12 Briefly discuss the history of combustion chamber design for Spark Ignition engine.
18,17 What are the functions of combustion chamber? State the requirements of designing
the combustion chamber of a CI engine for (i) high thermal efficiency (ii) smooth
engine operation.
15 What are the requirements to be fulfilled to design a good combustion chamber of SI
engine for high power output?
14,12 Briefly describe the objective of combustion chamber design.

2 Stroke Engine
22,21 What is meant by "scavenging"? "2-stroke CI engine is more common than 2-stroke
SI engine."- Explain the statement.
21,19,13 Why scavenging requires more attention in 2-stroke engine than that for 4-stroke
engine? Discuss the different types of scavenging processes with suitable diagrams.
18,14 What is meant by scavenging process? What are the different types of scavenging
pump used in two stroke engine? Describe one of them with neat suitable sketch.
16 Briefly describe the ideal scavenging system.

Engine Boosting(Supercharging & Turbocharging)

22,21 What is meant by supercharging? Describe the principle of operation of a turbo-
charger and its advantages.
21,19 Discuss supercharging limits for both SI and CI engines.
21 How supercharging influences, the performance of SI and CI engines? What kind of
modifications in engine are required if supercharging is to be employed?
19,14 Describe Buchi/Pulse turbo-charging system for IC engine.
19 Which one of SI engine and CI engine is more suitable for supercharging? Why?
18 What are the methods of turbo-charging in four stroke Cl engine? Write down the
advantages of pulse turbo-charging.
17 What is meant by supercharging? Mention its advantages. What are the different
types of supercharger used for supercharging? Briefly describe the centrifugal
compressor type supercharger.
15 Describe the method of supercharging and turbocharging with neat sketch.

Fuel Metering
22 How chemical structure of fuel determines the ignition quality? Explain fractional
distillation and chemical conversion processes in brief.
21 Classify fuel injection system and injector nozzle. Compare Pintaux nozzle with Pintle
nozzle.
21,17 Derive the expression for air-fuel ratio of simple carburetor taking compressibility
into account and also without it.
21,19 Why electronic fuel injection (EFI) is superior over conventional carburetion.
Describe the different types of fuel injection system for CI engines.
19 A 6-cylinder four stroke Cl engine develops 20 hp at 1200 rpm and consumes 0.20 kg
fuel per bhp per hour. Estimate the diameter of single orifice injector if the injection
pressure is 200 kg/cm2 and pressure in the cylinder is 40 kg/cm2. The period of
injection is 36° of crank angle. The specific gravity of fuel is 0.890 and coefficient of
discharge is 0.90.
18,13,12 With neat sketch describe the working principle of Bosch individual pump system for
injecting fuel in CI engine.
17 Classify fuel injection system for IC engine. Briefly explain air injection system with
its advantages and disadvantages.
17 What is meant by solid fuel injection and what are the main types of modern fuel
injection system?
16,12 What are the different types of nozzle used in Cl engine injector? Briefly describe
them.
16 A 6-cylinder 4-stroke 1 engine develops 250 kW at 1200 rpm and consumes 0.25 kg
of fuel per brake KW-hr. Determine the diameter of the single orifice if the injection
pressure is 130 bar and cylinder pressure during injection is 40 bar. The duration of
injection is 33° of the crank angle. Specific gravity of fuel is 0.88 and the coefficient
of discharge is 0.90.
15 What is meant by fuel metering in IC engine? What are the objectives to be fulfilled
for metering fuel in CI engine?
14 What are the modern systems of fuel injection in Cl engine? With a neat sketch
describe the working principle of any one type of individual fuel-pump system.
14 A 8 cylinder, 4-stroke diesel engine has power output of 368 kW at 800 rpm. Fuel
consumption is 0.238 kg/kWhr. The pressure in the cylinder at the beginning of fuel
injection is 35 bar and maximum cylinder pressure is 60 bar. The injector is expected
to be set at 210 bar and maximum pressure at the injector is set to be 600 bar.
 Calculate the orifice area required per injector, if injection takes place over 12° crank
angle. Assume coefficient of discharge for injector is 0.6, specific gravity of fuel is
0.85 and atmospheric pressure is 1.013 bars. Also, assume effective pressure
difference to be the average over the injection period.
13 Develop the following expression stated below for mass flow rate of air through the
venturi of a carburetor connected to SI engine.
𝐴𝑎 𝑃1 𝑃 𝑃
ma = 0.131 √(𝑃2 )1.43 − (𝑃2 )1.71
√𝑇1 1 1

13 What is injector? Describe the functions of injector.

Fuel & Fuel Rating

22,19 Explain the following terms:
(i) Anti-knock, (ii) Pro-knock, (iii) Sensitivity of fuel, and (iv) Cetane number.
19 Describe five major refining processes employed in crude oil refining industries.
Make a list of products of refining process.
19 What are the physical significances of octane number(ON) and cetane
number(CN) explain with example.
18 What is the role of TEL in improving knock rating of gasoline?
16,13 What is knock rating of a fuel? Describe the different fuel additives used to
reduce engine knocking.
16 How octane rating and cetane rating are calculated?
15 What are meant by-"Octane rating of fuels" and Octane number (ON)=80?
15 What is antiknock? What are the ideal requirements of an antiknock? Why TEL is
added with SI fuel?
12 Make a list of refinery products after refining crude oil. What is meant by ON =
80?
12 What is the function of delivery valve in fuel pump?
12 Discuss briefly advantages of pintle nozzle over single hole nozzle.
12 A 6-cylinder 4-stroke CI engine develops 15 kW at 900 rpm and consumes 0.2 kg
of fuel per kWhr. Estimate the diameter of the single orifice injector if the
injection pressure is 180 bar and pressure in the cylinder is 35 bar. The period of
injection is 30° of the crank angle. The specific gravity of fuel is 0.90 and
coefficient of discharge is 0.85.