4791 + Mcqs in Mechanical Engineering Page 8 McqOptions

351.	In axial flow compressor, exit flow angle deviation from the blade angle is a function of
A.	blade camber
B.	blade camber and incidence angle
C.	space-chord ratio
D.	blade camber and space-chord ratio
Answer» C. space-chord ratio

Discussion

352.	A rotary compressor is driven by an
A.	electric motor
B.	engine
C.	either (a) or (b)
D.	none of these
Answer» D. none of these

Discussion

353.	In a centrifugal compressor, an increase in speed at a given pressure ratio causes
A.	increase in flow
B.	decrease in flow
C.	increase in efficiency
D.	increase in flow and decrease in efficiency
Answer» E.

Discussion

354.	Rotary compressors are used for delivering
A.	small quantities of air at high pressures
B.	large quantities of air at high pressures
C.	small quantities of air at low pressures
D.	large quantities of air at low pressures
Answer» E.

Discussion

355.	The total heat rejected in a reciprocating air compressor is equal to the sum of the heat rejected during polytropic compression per kg of air and heat rejected in the intercooler per kg of air.
A.	True
B.	False
Answer» B. False

Discussion

356.	The wet bulb temperature during sensible heating of air
A.	remains constant
B.	increases
C.	decreases
Answer» C. decreases

Discussion

357.	The C.O.P. of an absorption type refrigerator is given by (where T1 = Temperature at which the working substance receives heat, T2 = Temperature of cooling water, and T3 = Evaporator temperature)
A.	<img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/420-193-1.png">
B.	<img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/420-193-2.png">
C.	<img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/420-193-3.png">
D.	<img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/420-193-4.png">
Answer» C. <img src="/_files/images/mechanical-engineering/heat-transfer-refrigeration-and-air-conditioning/420-193-3.png">

Discussion

358.	In a refrigerating machine, heat rejected is __________ heat absorbed.
A.	equal to
B.	less than
C.	greater than
Answer» D.

Discussion

359.	In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the
A.	Reynold's number
B.	Grashoff's number
C.	Reynold's number, Grashoff's number
D.	Prandtl number, Grashoff's number
Answer» E.

Discussion

360.	In a four stage compressor, if the pressure at the first and third stage are 1 bar and 16 bar, then the delivery pressure at the fourth stage will be
A.	1 bar
B.	16 bar
C.	64 bar
D.	256 bar
Answer» D. 256 bar

Discussion

361.	The compressed air may be used
A.	in gas turbine plants
B.	for operating pneumatic drills
C.	in starting and supercharging of I.C. engines
D.	all of the above
Answer» E.

Discussion

362.	A rocket works with maximum overall efficiency when air-craft velocity is __________ the jet velocity.
A.	equal to
B.	one-half
C.	double
Answer» C. double

Discussion

363.	The volumetric efficiency for reciprocating air compressors is about
A.	10 to 40%
B.	40 to 60%
C.	60 to 70%
D.	70 to 90%
Answer» E.

Discussion

364.	The difference of supersaturated temperature and saturation temperature at that pressure is called
A.	degree of supersaturation
B.	degree of superheat
C.	degree of undercooling
D.	none of these
Answer» D. none of these

Discussion

365.	The maximum temperature in a gas turbine is
A.	200 C
B.	500 C
C.	700 C
D.	1000 C
Answer» D. 1000 C

Discussion

366.	The efficiency of steam turbines may be improved by
A.	reheating of steam
B.	regenerative feed heating
C.	binary vapour plant
D.	any one of these
Answer» E.

Discussion

367.	In a reaction turbine, when steam flows through the fixed blades,
A.	pressure increases while velocity decreases
B.	pressure decreases while velocity increases
C.	pressure and velocity both decreases
D.	pressure and velocity both increases
Answer» C. pressure and velocity both decreases

Discussion

368.	Parson's turbine is a
A.	simple impulse turbine
B.	simple reaction turbine
C.	impulse-reaction turbine
D.	none of these
Answer» C. impulse-reaction turbine

Discussion

369.	The value of the reheat factor varies from
A.	1.02 to 1.06
B.	1.08 to 1.l0
C.	1.2 to 1.6
D.	1.6 to 2
Answer» B. 1.08 to 1.l0

Discussion

370.	Parson's reaction turbine is a __________ reaction turbine.
A.	40 percent
B.	50 percent
C.	60 percent
D.	70 percent
Answer» C. 60 percent

Discussion

371.	The critical pressure ratio (p2/p1) is given by
A.	<img src="/_files/images/mechanical-engineering/steam-nozzles-and-turbines/313-26-1.png">
B.	<img src="/_files/images/mechanical-engineering/steam-nozzles-and-turbines/313-26-2.png">
C.	<img src="/_files/images/mechanical-engineering/steam-nozzles-and-turbines/313-26-3.png">
D.	<img src="/_files/images/mechanical-engineering/steam-nozzles-and-turbines/313-26-4.png">
Answer» C. <img src="/_files/images/mechanical-engineering/steam-nozzles-and-turbines/313-26-3.png">

Discussion

372.	The turbine blades are
A.	straight
B.	circular
C.	curved
Answer» D.

Discussion

373.	In reaction turbines, the axial thrust is due to
A.	pressure drop across the rotor
B.	change in axial velocity
C.	both (a) and (b)
D.	none of these
Answer» D. none of these

Discussion

374.	The critical pressure gives the velocity of steam at the throat
A.	equal to the velocity of sound
B.	less than the velocity of sound
C.	more than the velocity of sound
D.	none of these
Answer» B. less than the velocity of sound

Discussion

375.	When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be
A.	choked
B.	underdamping
C.	overdamping
D.	none of these
Answer» C. overdamping

Discussion

376.	The ratio of the workdone on the blades to the energy supplied to the blades, is called
A.	blading efficiency
B.	nozzle efficiency
C.	gross or stage efficiency
D.	mechanical efficiency
Answer» B. nozzle efficiency

Discussion

377.	The discharge of steam in a convergent-divergent nozzle __________ after the throat (i.e. in the divergent portion of the nozzle)
A.	remains constant
B.	decreases
C.	increases
Answer» B. decreases

Discussion

378.	The Parsons' reaction turbine has
A.	only moving blades
B.	only fixed blades
C.	identical fixed and moving blades
D.	fixed and moving blades of different shape
Answer» D. fixed and moving blades of different shape

Discussion

379.	The rate of discharge through the nozzle __________ when the exit pressure is gradually reduced.
A.	remains same
B.	decreases
C.	increases
Answer» D.

Discussion

380.	The turbine, in which the general direction of the steam flow is parallel to the turbine axis, is called axial flow turbines
A.	True
B.	False
Answer» B. False

Discussion

381.	A binary vapour plant consists of
A.	steam turbine
B.	steam condenser
C.	mercury boiler
D.	all of these
Answer» E.

Discussion

382.	The blade velocity coefficient is ratio of relative velocity of steam at outlet tip of the blade to the relative velocity of steam at inlet tip of the blade.
A.	True
B.	False
Answer» B. False

Discussion

383.	Multi-stage steam turbines are of the
A.	velocity compounded type
B.	reaction type
C.	pressure compounded type
D.	all of these
Answer» E.

Discussion

384.	The critical pressure gives the velocity of steam at the throat equal to the velocity of sound.
A.	Agree
B.	Disagree
Answer» B. Disagree

Discussion

385.	The discharge is __________ at critical pressure.
A.	zero
B.	minimum
C.	maximum
Answer» D.

Discussion

386.	The reheat factor is the ratio of the
A.	cumulative heat drop to the isentropic heat drop
B.	isentropic heat drop to the heat supplied
C.	total useful heat drop to the total isentropic heat drop
D.	none of the above
Answer» B. isentropic heat drop to the heat supplied

Discussion

387.	The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop
A.	remains the same
B.	increases
C.	decreases
D.	is unpredictable
Answer» D. is unpredictable

Discussion

388.	High speed compression engines operate on
A.	Otto cycle
B.	Diesel cycle
C.	Dual-combustion cycle
D.	all of these
Answer» D. all of these

Discussion

389.	The pressure inside the cylinder is __________ the atmospheric pressure during the exhaust stroke.
A.	equal to
B.	below
C.	above
Answer» D.

Discussion

390.	The steam leaves the nozzle at a
A.	high pressure and a low velocity
B.	high pressure and a high velocity
C.	low pressure and a low velocity
D.	low pressure and a high velocity
Answer» E.

Discussion

391.	The detonating tendency in petrol engines increases with increase of compression ratio.
A.	True
B.	False
Answer» B. False

Discussion

392.	Each fission of U235 produces on the average __________ fast neutrons as a product of reaction.
A.	2.46
B.	24.6
C.	246
D.	2460
Answer» B. 24.6

Discussion

393.	The self ignition temperature of petrol is __________ as compared to diesel oil.
A.	same
B.	lower
C.	higher
Answer» D.

Discussion

394.	In open combustion chamber in diesel engines, the shape and layout of the piston crown, the inlet port and the valve produce the turbulent effect of fuel mixture.
A.	True
B.	False
Answer» B. False

Discussion

395.	In a four stroke cycle petrol engine, the charge is ignited at
A.	30 before top dead centre
B.	30 after top dead centre
C.	30 before bottom dead centre
D.	30 after bottom dead centre
Answer» B. 30 after top dead centre

Discussion

396.	The brake power of a diesel engine, keeping other parameters constant, can be increased by
A.	decreasing the density of intake air
B.	increasing the temperature of intake air
C.	increasing the pressure of intake air
D.	decreasing the pressure of intake air
Answer» D. decreasing the pressure of intake air

Discussion

397.	In diesel engines, the fuel is injected in the form of very fine spray, into the engine cylinder, which gets ignited due to high temperature of the compressed air.
A.	Agree
B.	Disagree
Answer» B. Disagree

Discussion

398.	The nuclear power station at Tarapur has the reactor of the __________ type.
A.	pressurized water
B.	boiling water
C.	gas cooled
D.	liquid metal cooled
Answer» C. gas cooled

Discussion

399.	In nuclear power plants, due to reflector, less fuel is needed to generate sufficient neutrons to sustain a chain reaction.
A.	Yes
B.	No
Answer» B. No

Discussion

400.	In a four stroke cycle petrol engine, the inlet valve
A.	opens at top dead centre and closes at bottom dead centre
B.	opens at 20 before top dead centre and closes at 40 after bottom dead centre
C.	opens at 20 after top dead centre and closes at 20 before bottom dead centre id) may open or close anywhere
Answer» C. opens at 20 after top dead centre and closes at 20 before bottom dead centre id) may open or close anywhere

Discussion

Explore topic-wise MCQs in Engineering.

In axial flow compressor, exit flow angle deviation from the blade angle is a function of

A rotary compressor is driven by an

In a centrifugal compressor, an increase in speed at a given pressure ratio causes

Rotary compressors are used for delivering

The total heat rejected in a reciprocating air compressor is equal to the sum of the heat rejected during polytropic compression per kg of air and heat rejected in the intercooler per kg of air.

The wet bulb temperature during sensible heating of air

The C.O.P. of an absorption type refrigerator is given by (where T1 = Temperature at which the working substance receives heat, T2 = Temperature of cooling water, and T3 = Evaporator temperature)

In a refrigerating machine, heat rejected is __________ heat absorbed.

In free convection heat transfer transition from laminar to turbulent flow is governed by the critical value of the

In a four stage compressor, if the pressure at the first and third stage are 1 bar and 16 bar, then the delivery pressure at the fourth stage will be

The compressed air may be used

A rocket works with maximum overall efficiency when air-craft velocity is __________ the jet velocity.

The volumetric efficiency for reciprocating air compressors is about

The difference of supersaturated temperature and saturation temperature at that pressure is called

The maximum temperature in a gas turbine is

The efficiency of steam turbines may be improved by

In a reaction turbine, when steam flows through the fixed blades,

Parson's turbine is a

The value of the reheat factor varies from

Parson's reaction turbine is a __________ reaction turbine.

The critical pressure ratio (p2/p1) is given by

The turbine blades are

In reaction turbines, the axial thrust is due to

The critical pressure gives the velocity of steam at the throat

When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be

The ratio of the workdone on the blades to the energy supplied to the blades, is called

The discharge of steam in a convergent-divergent nozzle __________ after the throat (i.e. in the divergent portion of the nozzle)

The Parsons' reaction turbine has

The rate of discharge through the nozzle __________ when the exit pressure is gradually reduced.

The turbine, in which the general direction of the steam flow is parallel to the turbine axis, is called axial flow turbines

A binary vapour plant consists of

The blade velocity coefficient is ratio of relative velocity of steam at outlet tip of the blade to the relative velocity of steam at inlet tip of the blade.

Multi-stage steam turbines are of the

The critical pressure gives the velocity of steam at the throat equal to the velocity of sound.

The discharge is __________ at critical pressure.

The reheat factor is the ratio of the

The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop

High speed compression engines operate on

The pressure inside the cylinder is __________ the atmospheric pressure during the exhaust stroke.

The steam leaves the nozzle at a

The detonating tendency in petrol engines increases with increase of compression ratio.

Each fission of U235 produces on the average __________ fast neutrons as a product of reaction.

The self ignition temperature of petrol is __________ as compared to diesel oil.

In open combustion chamber in diesel engines, the shape and layout of the piston crown, the inlet port and the valve produce the turbulent effect of fuel mixture.

In a four stroke cycle petrol engine, the charge is ignited at

The brake power of a diesel engine, keeping other parameters constant, can be increased by

In diesel engines, the fuel is injected in the form of very fine spray, into the engine cylinder, which gets ignited due to high temperature of the compressed air.

The nuclear power station at Tarapur has the reactor of the __________ type.

In nuclear power plants, due to reflector, less fuel is needed to generate sufficient neutrons to sustain a chain reaction.

In a four stroke cycle petrol engine, the inlet valve