Deck 2: Diesel Engines and Thermodynamic Cycles

Question 1

Scavenging air in diesel engine means

A)air used for combustion sent under pres-sure
B)forced air for cooling cylinder
C)burnt air containing products of com-bastion
D)air used for forcing burnt gases out of engine's cylinder during the exhaust period

Answer 1

air used for forcing burnt gases out of engine's cylinder during the exhaust period

Question 2

Does the supply of scavenging air at a density greater than that of atmosphere mean engine is supercharged?

A)yes
B)no
C)to some extent
D)unpredictable

Answer 2

no

Question 3

The ratio of indicated thermal efficiency to the corresponding air standard cycle efficiency is called

A)net efficiency
B)efficiency ratio
C)relative efficiency
D)overall efficiency

Answer 3

relative efficiency

Question 4

Compression ratio of LC. Engines is

A)the ratio of volumes of air in cylinder before compression stroke and after compression stroke
B)volume displaced by piston per stroke and clearance volume in cylinder
C)ratio of pressure after compression and before compression
D)swept volume/cylinder volume

Question 5

A perfect engine works on the Carnot cycle between 727 °C and 227°C. The efficiency of the engine is

A)0.5
B)0.75
C)1
D)0.25

Question 6

The air standard Otto cycle consists of

A)two constant volume and two isentropic processes
B)two constant pressure and two isentropic processes
C)two constant pressure and two constant volume processes
D)none of the above

Question 7

In air standard Diesel cycle at fixed r and fixed n

A)?thermal increases with increase in heat addition and cut-off ratio
B)?thermal decreases with increase in heat addition and cut-off ratio
C)?thermal Remains the same with increase in heat addition and cut-off ratio
D)none of the above

Question 8

Mean effective pressure of Otto cycle is

A)inversely proportional to pressure ratio
B)directly proportional to pressure ratio
C)does not depend on pressure ratio
D)proportional to square root of pressure ratio

Question 9

For a given compression ratio the work output of Otto cycle is

A)increases with Increase in r
B)decreases with increase in r
C)is not affected
D)none of the above

Question 10

For a given value of r, efficiency of Otto cycle

A)decreases with compression ratio
B)increases with compression ratio
C)is not affected
D)none of the above

Question 11

For dual combustion cycle for fixed value of heat addition and compression ratio

A)mep wil be greater with increase in rp, and decrease in rc
B)mep will be greater with decrease in rp and decrease in rc
C)mep remain the same with increase in rp and decrease in rc
D)none of the above

Question 12

The normal range of, compression ratio for Otto cycle is

A)6 to 10
B)2 to 4
C)>10
D)none of the above

Question 13

The normal range of compression ratio for Diesel cycle is

A)4 to 6
B)6 to 8
C)15 to 20
D)>25

Question 14

For the same compression ratio and heat addition

A)?Otto > ?Diesel > ?Dual
B)?Diesel > ?Otto > ?Dual
C)?Otto> ?Dual > ?Diesel
D)?Dual> ?Diesel > ?Otto

Question 15

for the same compression ratio and heat rejection,

A)?Otto> ?Dual > ?Diesel
B)?Diesel > ?Dual > ?Otto
C)?Dual> ?Diesel > ?Otto
D)?Dual> ?Otto> ?Diesel

Question 16

When the engines are built to withstand the sane thermal and mechanical stresses

A)?Diesel > ?Dual > ?Otto
B)?Dual> ?Diesel > ?Otto
C)?Otto> ?Dual > ?Diesel
D)?Otto> ?Diesel > ?Dual

Question 17

For the same peak pressure and heat input

A)?Otto > ?Dual > ?Diesel
B)?Otto > ?Diesel > ?Dual
C)?Diesel > ?Dual > ?Otto
D)?Diesel > ?Otto > ?Dual

Question 18

For the same peak pressure and work output

A)?Otto > ?Dual > ?Diesel
B)?Otto > ?Diesel > ?Dual
C)?Diesel > ?Otto > ?Dual
D)?Diesel > ?Dual > ?Otto

Question 19

Brayton cycle is used in

A)Ramjet engines
B)gas turbines
C)pulse jet engines
D)Cl engines

Question 20

The actual efficiency of a good engine is about _______of the estimated fuel-air cycle efficiency.

A)100%
B)85%
C)50%
D)25%

Question 21

With dissociation peak temperature is obtained

A)at the stoichiometric air-fuel ratio
B)when the mixture is slightly lean
C)when the mixture is slightly rich
D)none of the above

Question 22

With dissociation the exhaust gas temperature

A)decreases
B)increases
C)no effect
D)increases upto certain air-fuel ratio and then decreases

Question 23

Fuel-air ratio affects maximum power output of the engine due to

A)higher specific heats
B)chemical equilibrium losses
C)both (a) and (b)
D)none of the above

Question 24

Mean effective pressure at a given compression ratio is maximum when the air-fuel ratio is

A)higher than stoichiometric
B)lower than stoichiometric
C)equal to stoichionetric
D)none of the above

Question 25

For a compressor process with variable specific heat the peak temperature and pressure are _______compared to constant specific heat

A)lower
B)higher
C)no effect
D)none of the above