Deck 3: Combustion and Efficiency in Engines

Question 1

Dissociation can be considered as

A)disintegration of combustion products at high temperature
B)reverse process of combustion
C)heat absorption process
D)all of the above

Answer 1

all of the above

Question 2

Time loss factor in actual cycle is due to

A)Progressive combustion
B)heat loss through cylinder walls
C)gas leakage
D)friction

Answer 2

Progressive combustion

Question 3

The major loss in a SI engine is due to

A)exhaust blow down
B)pumping
C)incomplete combustion
D)variation in specific heat and chemical equilibrium

Answer 3

variation in specific heat and chemical equilibrium

Question 4

Fuel-air cycle efficiency is less than air-standard cycle efficiency by an amount equal to

A)pumping loss
B)friction loss
C)loss due to specific heat variation and chemical equilibrium
D)exhaust blow down loss

Question 5

The major loss in a CI engine is

A)direct heat loss
B)loss due to incomplete combustion
C)rubbing friction loss
D)pumping loss

Question 6

The ratio of the actual efficiency and the fuel-air cycle efficiency for CI engines is about

A)0.2-0.3
B)0.5-0.6
C)1.0
D)0.6-0.8

Question 7

In an actual SI engine the pumping loss with respect to speed

A)decreases
B)Increases
C)remains constant
D)nothing to do with speed

Question 8

The volumetric efficiency is affected by

A)the exhaust gas in the clearance volume
B)the design of intake and exhaust valve
C)valve timing
D)all of the above

Question 9

The air standard efficiency of an Otto cycle compared to diesel cycle for the given compression ratio is

A)same
B)less
C)more
D)more or less depending on power rating

Question 10

In a typical medium speed, 4-stroke cycle diesel engine

A)fuel injection starts at 10° before to dead center and ends at 20° after tor dead center
B)fuel injection starts at top dead center and ends at 20° after top dead center
C)fuel injection starts at just before top dead center and ends just after top dead center
D)may start and end anywhere

Question 11

The amount of heat liberated by complete combustion of unit quantity of fuel is known as ________

A)Agitation
B)Combustion
C)Calorific value
D)Thermogenesis

Question 12

What is the significance of calorific value?

A)Helps in deciding which fuel is good
B)Helps in locating fuel
C)Helps in deciding ignition temperature
D)Helps in deciding fire point

Question 13

Which gas has the highest calorific value among given option?

A)Oxygen
B)Helium
C)Hydrogen
D)Nitrogen

Question 14

Which calorimeter is used to find calorific values of solid and liquid fuels?

A)Boy's calorimeter
B)Bomb calorimeter
C)Junker's calorimeter
D)Calvet-type calorimeter

Question 15

Which calorimeter is used to find calorific values of gaseous fuels?

A)Bomb calorimeter
B)Junker calorimeter
C)Adiabatic calorimeter
D)Isothermal titration calorimeter

Question 16

What is the factor on which, difference between the two heating values of fuel depends on?

A)Physical properties
B)Reactants
C)Chemical composition
D)Products

Question 17

The Bomb calorimeter is used to determine the calorific value of:

A)solids and liquid fuels
B)solid and gaseous fuels
C)liquid fuels that can be easily vaporized
D)solid fuels only

Question 18

If the intake air temperature of I.C. engine increases, its efficiency will

A)increase
B)decrease
C)remain same
D)unpredictable

Question 19

All heat engines utilize

A)low heat value of oil
B)high heat value of oil
C)net claorific value of oil
D)calorific value of fuel

Question 20

Fuel oil consumption guarantees for I .C. engine are usually based on

A)low heat value of oil
B)high heat value of oil
C)net calorific value of oil
D)calorific value of fuel

Question 21

Combustion in compression ignition engines is

A)homogeneous
B)heterogeneous
C)both (a) and (b)
D)laminar

Question 22

The air requirement of a petrol engine during starting compared to theoretical required for complete combustion is

A)more
B)loss
C)same
D)may be more or less depending on engine capacity

Question 23

Diesel fuel, compared to petrol is

A)less difficult to ignite
B)just about the same difficult to ignite
C)more difficult to ignite
D)highly ignitable