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engineering
introduction mechanical engineering

Basic Mechanical Engineering 2nd Edition PRAVIN KUMAR - Solutions

Mechanical efficiency of two-stroke engine in comparison to four-stroke engine is:(a) More(b) Same(c) Less(d) None of the above
What is supercharging? Explain the structure and working of two-stroke diesel engine.
Thermal efficiency of two-stroke engine in comparison to four-stroke engine is:(a) More(b) Same(c) Less(d) None of the above
The following results refer to a test on C.I. Engine:Indicated power \(=37 \mathrm{~kW}\);Frictional power \(=6 \mathrm{~kW}\);Brake specific fuel consumption \(=0.28 \mathrm{~kg} / \mathrm{KWh}\); Calorific value of fuel \(=44,300 \mathrm{~kJ} / \mathrm{kg}\)Calculate: (i) mechanical efficiency,
During testing of single cylinder two-stroke petrol engine, following data were obtained-brake torque \(=640 \mathrm{Nm}\); cylinder diameter \(=21 \mathrm{~cm}\), speed \(=250 \mathrm{rpm} ;\) stroke \(=28 \mathrm{~cm}\); m.e.p. \(=5.6\) bar; oil consumption \(=8.16 \mathrm{~kg} / \mathrm{hr} ;\)
Explain the valve timing diagram of four-stroke petrol and diesel engines.
Following readings were taken during test of single cylinder four-stroke engine:Cylinder diameter \(=250 \mathrm{~mm}\); stroke length \(=\) \(400 \mathrm{~mm}\); m.e.p. \(=6.5\) bar; Engine speed \(=250\) rpm; net load on brake \(=1,080 \mathrm{~N}\); effective diameter of brake \(=1.5
In a petrol engine, charge is ignited with:(a) Spark plug(b) Compression(c) Both(d) None of the above
Derive an expression for the efficiency of Otto cycle.
In an ideal diesel cycle, the temperatures at the beginning and at the end of compression are \(57^{\circ} \mathrm{C}\) and \(603^{\circ} \mathrm{C}\), respectively. The temperatures at the beginning and at the end of expansion are \(1959^{\circ} \mathrm{C}\) and \(870^{\circ} \mathrm{C}\),
In four-stroke petrol engine:(a) Intake valve closes after top dead center(b) Intake valve closed after bottom dead center(c) Exhaust valve closes after top dead center(d) Exhaust valve closes after bottom dead center
Explain the working of the dual cycle with the help of P–V and T–S diagrams. Derive an expression for air standard efficiency of the dual cycle in terms of compression ratio, pressure ratio, cut-off ratio, and adiabatic index.
In an air standard Otto cycle, the compression ratio is 10 and begins at \(37.8^{\circ} \mathrm{C}, 1\) bar and maximum temperature of the cycle is \(1060^{\circ} \mathrm{C}\). Determine: (i) heat supplied per kg of air, (ii) work done per \(\mathrm{kg}\) of air, (iii) maximum pressure of the
Compression ratio in petrol engine ranges from:(a) 6 to 10(b) 10 to 15(c) 15 to 25(d) 25 to 40
Write down working of two-stroke petrol engine with neat sketch.
In an air standard diesel cycle, the compression ratio is 15 and pressure and temperature of the air at the beginning of the compression are 1 bar and \(288 \mathrm{~K}\). The peak temperature in the cycle is 2,700 K. Calculate: (i) heat supplied, (ii) work done, (iii) cycle efficiency, (iv) peak
A gas engine working on four-stroke cycle has a cylinder of \(250 \mathrm{~mm}\) diameter, length of stroke \(450 \mathrm{~mm}\) and is running at \(180 \mathrm{rpm}\). Its mechanical efficiency is \(80 \%\); mean effective pressure is \(0.65 \mathrm{MPa}\), Find: (i) indicated power, (ii) brake
How are I.C. engines classified? Draw P–V diagrams of Otto and diesel engine cycles.
If compression ratio in petrol engines kept higher than that is in diesel engines, then:(a) Pre-ignition of fuel will occur(b) Ignition of fuel will be delayed(c) Detonation will occur(d) None of the above
Compression ratio in diesel engine ranges from:(a) 6 to 10(b) 10 to 15(c) 14 to 22(d) 25 to 40
Draw the diesel cycle on P–V and T–S coordinates and explain its functioning.
A four-stroke single cylinder petrol engine has a bore of \(150 \mathrm{~mm}\) and stroke of \(250 \mathrm{~mm}\). At \(500 \mathrm{rpm}\) and full load, the net load on friction brake is \(435 \mathrm{~N}\) and torque arm is \(0.45 \mathrm{~m}\). The indicator diagram gives a net area of \(580
In C.I. Engines, the combustion is:(a) Homogeneous(b) Heterogeneous(c) Both(d) None of the above
Differentiate between C.I and S.I. engine.
Following observations were made during a trail on four-stroke diesel engine. Cylinder diameter \(=250 \mathrm{~mm}\), stroke \(=400 \mathrm{~mm}\), speed \(=250 \mathrm{rpm}\) brake load \(=70 \mathrm{~kg}\), brake drum diameter \(=2 \mathrm{~m}\). m.e.p. \(=6\) bar, diesel oil consumption
Explain with the neat sketch, working of the two-stroke petrol engine.
Which of the following is not related to C.I. engine:(a) Fuel pump(b) Fuel injector:(c) Carburetor(d) Flywheel
Following data were collected from a four-stroke single cylinder I.C. engine at full load. Bore \(=\) \(200 \mathrm{~mm}\), stroke \(=280 \mathrm{~mm}\), speed \(=300 \mathrm{rpm}\), m.e.p. \(=5.6\) bar, torque \(=250 \mathrm{Nm}\). Oil consumption \(=4.2 \mathrm{~kg} / \mathrm{h}, \mathrm{C} .
Indicator on an engine is used to determine:(a) B.H.P(b) Speed(c) Temperature(d) I.H.P and M.E.P
Derive an equation for air standard efficiency of Otto cycle.
During testing of single cylinder two-stroke petrol engine following data were obtained. Brake torque \(=640 \mathrm{Nm}\), cylinder diameter 21 \(\mathrm{cm}\), speed \(350 \mathrm{rpm}\), stroke length \(=28 \mathrm{~cm}\), mean effective pressure \(=5.6 \mathrm{bar}\), oil consumption \(=8.16
Morse test is conducted on:(a) Vertical engines(b) Horizontal engines(c) Single cylinder engines(d) Multi cylinder engines
Derive the equation for air standard efficiency of Diesel cycle.
In an engine working on Otto cycle, air has a pressure of 1.0 bar and temperature \(30^{\circ} \mathrm{C}\) at the entry. Air is compressed with a compression ratio of 6 . The heat is added at constant volume until the temperature rises to \(1,500^{\circ} \mathrm{C}\). Determine: (i) air standard
The m.e.p. of a diesel engine with fixed compression ration can be improved by:(a) Increasing cut-off ratio(b) Increasing back pressure(c) Increasing operating pressure(d) Reducing charge density
Differentiate between Petrol engine and diesel engine.
In an Otto cycle, the compression ratio is 10 . The temperature at the beginning of compression and at the end of heat supply is 300 and \(1600 \mathrm{~K}\), respectively. Assume, \(\gamma=1.4\) and CV \(=0.717 \mathrm{KJ} / \mathrm{kgK}\). Find: (i) Heat supplied, and (ii) Efficiency of the cycle.
An engine is said to be square if cylinder bores equal to _______ .
Explain the working of four-stroke petrol engine with neat sketch.
The following data refers to a single cylinder 4 strokes petrol engine. Cylinder diameter \(=30\) \(\mathrm{cm}\), piston stroke \(=40 \mathrm{~cm}\), engine speed \(=1,400\) rpm, indicated mean effective pressure \(=5\) bar, fuel consumption \(=17.568 \mathrm{~kg} / \mathrm{h}\), calorific value
The period during both inlet and exhaust valve remain open is known as _____.
Explain the working of four-stroke petrol engine with neat sketch and P–V diagram.
In ideal constant volume cycle, the pressure and temperature at the beginning of compression are \(97 \mathrm{kPa}\) and \(50^{\circ} \mathrm{C}\), respectively. The volume ratio is 8. The heat is supplied during the cycle is 930 \(\mathrm{kJ} / \mathrm{kg}\) of working fluid. Calculate: (i) the
A two-stroke engine employs ______ cut in the wall of cylinder instead of ______.
With the neat sketch, explain the principle of MPFI?
A four cylinder two-stroke petrol engine with stroke to bore ratio 1.2 develops \(35 \mathrm{~kW}\) brake power at 2,200 rpm. The mean effective pressure in each cylinder is 9 bar and mechanical efficiency is \(78 \%\). Determine: (i) Diameter and stroke of each cylinder, (ii) brake thermal
In four-stroke petrol engine, size of intake valve is ______ than that of exhaust valve.
With the neat sketch, explain the principle of CRDI?
An engine operates on the air standard diesel cycle. The conditions at the start of the compression stroke are \(353 \mathrm{~K}\) and \(100 \mathrm{kPa}\), while at the end of compression stroke the pressure is \(4 \mathrm{MPa}\). The energy absorbed is \(700 \mathrm{~kJ} / \mathrm{kg}\) of air.
Carburetion is the process of ____ and ____.
Give advantages of two-stroke engine over four stroke engine.
An air at \(15^{\circ} \mathrm{C}\) and 1 bar is compressed adiabatically to 15 bar by an engine working on Otto cycle. The maximum pressure of the cycle is 40 bar. Calculate air standard efficiency, mean effective pressure. Take \(\mathrm{Cv}=0.718 \mathrm{~kJ} / \mathrm{kg} \mathrm{K}\) and
Draw a schematic diagram of I.C. engines and name the parts.
A four-stroke diesel engine has a piston diameter \(250 \mathrm{~mm}\) and stroke \(400 \mathrm{~mm}\). The mean effective pressure is 4 bar and speed is \(500 \mathrm{rpm}\) the diameter of the brake drum is \(1,000 \mathrm{~mm}\) and the effective brake load is 4,000 N. Find IP, BP, FP.
Define—Thermal efficiency and mechanical efficiency of I.C. engine.
The inner surface of a plain brick wall is at 80°C and the outer surface is at 30°C. Calculate the rate of heat transfer per m2 of the surface area of the wall, which is 280 mm thick. The thermal conductivity of the brick is 0.75 W/mK.
A gas engine working on 4-stroke cycle has a cylinder diameter \(300 \mathrm{~mm}\) and stroke length of 500 \(\mathrm{mm}\) is running at \(220 \mathrm{rpm}\). Its mechanical efficiency is \(80 \%\) when the mean effective pressure is \(0.65 \mathrm{MPa}\). Find (i) indicated power, (ii) brake
What do you mean by heat transfer? Explain its applications in engineering.
Heat transfer takes place as per:(a) Zeroth law of thermodynamics(b) First law of thermodynamics(c) Second law of thermodynamics(d) All the three
Explain the different modes of heat transfer.
A steel tank of wall thickness \(10 \mathrm{~mm}\) contains water at \(90^{\circ} \mathrm{C}\). Calculate the rate of heat loss per \(\mathrm{m}^{2}\) of tank surface area when the atmospheric temperature is \(15^{\circ} \mathrm{C}\). The thermal conductivity of mild steel is \(55 \mathrm{~W} /
When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred at as heat transfer by:(a) Conduction(b) Convection(c) Radiation(d) None of these
Derive the expression for heat flow in steady state conduction without heat generation using Fourier Law.
A furnace wall consists of \(100 \mathrm{~mm}\) thick refractory brick and \(800 \mathrm{~mm}\) thick insulating firebrick separated by an air gap. The outside wall is covered with a \(20 \mathrm{~mm}\) thickness of plaster. The inner surface of the wall is at \(1,100^{\circ} \mathrm{C}\) and the
When heat is transferred from hot body to cold body, in a straight line, without affecting the intervening medium, it is referred to as heat transfer by:(a) Conduction(b) Convection(c) Radiation(d) None of these
Explain Newton’s law of cooling and derive the heat flow in convection.
A steel pipe of \(100 \mathrm{~mm}\) bore and \(10 \mathrm{~mm}\) wall thickness, carrying steam at \(250^{\circ} \mathrm{C}\), is insulated with \(30 \mathrm{~mm}\) of a molded high-temperature diatomaceous earth covering. This covering is in turn insulated with \(60 \mathrm{~mm}\) of asbestos
Heat transfer in liquids and gases takes place by:(a) Conduction(b) Convection(c) Radiation(d) None of these
Explain Stefan and Boltzmann’s law of and derive the heat flow in convection.
A small hemispherical oven is built of an inner layer of insulating firebrick \(110 \mathrm{~mm}\) thick, and an outer covering \(80 \%\) magnesia \(45 \mathrm{~mm}\) thick. The inner surface of the oven is \(850^{\circ} \mathrm{C}\) and the heat transfer coefficient for the outside surface is \(12
When heat is transferred by molecular collision, it is referred to as heat transfer by:(a) Conduction(b) Convection(c) Radiation(d) None of these
Heat flows from one body to other when they have:(a) Different heat contents(b) Different specific heat(c) Different atomic structure(d) Different temperature
The amount of heat flow through a body by conduction is:(a) Directly proportional to the surface area of the body(b) Dependent upon material of the body(c) Directly proportional to the temperature difference:(d) All of the above
Thermal conductivity of a material may be defined as the:(a) Quantity of heat flowing in one second through one cubic meter of material when opposite faces are maintained at a temperature difference of \(1^{\circ} \mathrm{C}\).(b) Quantity of heat flowing in one second through one square meter of
Heat transfer by radiation mainly depends upon:(a) Its temperature(b) Nature of the body(c) Kind and extent of its surface(d) All of the above
If two surfaces of area \(A\) distance \(L\) apart, of a material having thermal conductivity \(\mathrm{k}\), are at temperatures \(t_{1}\) and \(t_{2}\) then heat flow rate through it will be:(a) \(\mathrm{kA}\left(\mathrm{t}_{1}-\mathrm{t}_{2}\right) / \mathrm{L}\)(b)
According to Stefan's Law, the total radiation from a black body per second per unit area is proportional to:(a) \(\mathrm{T}\)(b) \(\mathrm{T}^{2}\)(c) \(\mathrm{T}^{3}\)(d) \(\mathrm{T}^{4}\)
If the inner and outer surfaces of a hollow cylinder (having radii \(r_{1}\) and \(r_{2}\) and length \(\mathrm{L}\) ) are at temperature \(t_{1}\) and \(t_{2}\), then rate of radial heat flow will be:(a) \(\frac{k}{2 \pi L} \cdot \frac{t_{1}-t_{2}}{\log _{e} \frac{r_{2}}{r_{1}}}\)(b) \(\frac{1}{2
If the inner and outer walls of a hollow sphere having surface areas of \(A_{1}\) and \(A_{2}\), and inner and outer radii \(r_{1}\) and \(r_{2}\), are maintained at temperatures \(t_{1}\) and \(t_{2}\), then rate of heat flow will be:(a) \(k \sqrt{A_{1} A_{2}} \cdot
LMTD for a heat exchanger is given by:(a) \(\frac{\Delta t_{2}-\Delta t_{1}}{\log _{e} \frac{\Delta t_{2}}{\Delta t_{1}}}\)(b) \(\frac{\Delta t_{2}-\Delta t_{1}}{\log _{e} \frac{\Delta t_{1}}{\Delta t_{2}}}\)(c) Both(d) None of these
The heat flow equation through a sphere of inner radius \(r_{1}\) and outer radius \(r_{2}\) is to be written in the same form as that for heat flow through a plane wall. For wall thickness \(\left(r_{2}-r_{1}\right)\), the equivalent mean radius for the spherical shell is:(a)
The cooling effect in refrigeration is obtained by:(i) Mechanical refrigeration technique(ii) Passing a direct current through the junction of two dissimilar metals(iii) Sublimation of carbon dioxide(iv) Throttling of a real gas Which of the above statements are correct?(a) (i) and (ii)(b) (i),
Differentiate the working of refrigeration and heat pump, thermodynamically.
Carnot refrigeration cycle absorbs heat at \(280 \mathrm{~K}\) and rejects heat at \(310 \mathrm{~K}\).(a) Calculate the coefficient of performance of this refrigeration cycle.(b) If the cycle is absorbing \(1120 \mathrm{~kJ} / \mathrm{min}\) at \(280 \mathrm{~K}\), how many kJ of work is required
The cooling effect produced by refrigeration finds application in:(i) Construction of cold storages(ii) Cooling of concrete in dams(iii) Comfort air conditioning of hospitals(iv) Liquification of gases and vapors Select your answer from the following codes:(a) (i) and (iii)(b) (i), (ii) and
Enumerate the various components used in a refrigerator and explain their working.
The capacity of a refrigerator is \(200 \mathrm{TR}\) when working between \(-4^{\circ} \mathrm{C}\) and \(22^{\circ} \mathrm{C}\). Determine the mass of ice produced per day from water at \(22^{\circ} \mathrm{C}\). Also, find the power required to drive the unit. Assume that the cycle operates on
A refrigeration system:(a) Removes heat from a system at low temperature and transfers the same to a system at high-temperature(b) Delivers less heat to the system at high temperature than it extracts from the system at low-temperature(c) Transfers heat from a high-temperature source to a
Write advantages and disadvantages of air refrigeration cycle.
A glass of water is mixed with ice. The moisture from the air begins to condense on the surface of glass when the temperature of water comes \(12^{\circ} \mathrm{C}\). If the room temperature and pressure are \(25^{\circ} \mathrm{C}\) and 1.01325 bars, Determine the partial pressure and mass of
The COP of a Carnot refrigeration cycle decreases on:(a) Decreasing the difference in operating temperatures(b) Keeping the upper-temperature constant and increasing the lower-temperature(c) Increasing the upper-temperature and keeping the lower-temperature constant(d) Increasing the
The pressure and temperature of the mixture of air and water vapor at 1 bar and \(22^{\circ} \mathrm{C}\). The dew point temperature of the mixture is \(12^{\circ} \mathrm{C}\). Find partial pressure of water vapor in the mixture, relative humidity, specific humidity, enthalpy of mixture per
Find the expression for COP using Reversed Carnot cycle and Bell Coleman cycle.
A Carnot refrigerating cycle used in house air conditioning delivers heat to the surroundings at the rate of \(10 \mathrm{kw}\) of power. The coefficient of performance of this refrigerator would be:(a) 1.5(b) 1.67(c) 2.5(d) 0.6
Find the derivation for COP in Vapor Compression cycle.
If a Carnot cycle is to have a coefficient of performance of 5 , the ratio of maximum temperature to minimum temperature in the cycle should be:(a) 1.2(b) 1.5(c) 2.0(d) 2.5
Explain the effect of subcooling and superheating on COP of Vapor Compression Cycle.
The DBT and \(\mathrm{RH}\) of air are \(38^{\circ} \mathrm{C}\) and \(60 \%\) respectively. The atmospheric pressure is 1 bar. Determine the specific humidity and vapor pressure of moisture in the air. If 10 grams of water vapor is removed from the air and temperature is reduced to \(28^{\circ}
A Carnot refrigerator rejects \(3000 \mathrm{kj}\) of heat at \(400 \mathrm{k}\) while using \(1000 \mathrm{kj}\) of work. The lowest operating temperature in the cycle should be:(a) \(15^{\circ} \mathrm{C}\)(b) \(27^{\circ} \mathrm{C}\)(c) \(-6^{\circ} \mathrm{C}\)(d) \(0^{\circ} \mathrm{C}\)
Compare vapor compression and Reversed Carnot Cycle.

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