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

Accepted Answer

Dissociation can be considered as all of the above: it involves the disintegration of combustion products at high temperatures, can be seen as the reverse process of combustion, and is a heat absorption process.

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

Accepted Answer

Progressive combustion causes a delay in the combustion process, leading to a time loss factor in the actual cycle.

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

Accepted Answer

D

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

Accepted Answer

The efficiency of the fuel-air cycle is less than that of the air-standard cycle primarily due to the loss attributed to specific heat variation and chemical equilibrium. This difference arises because the air-standard cycle assumes constant specific heats, whereas in the fuel-air cycle, the specific heats vary with temperature, and chemical reactions occur, affecting the cycle's efficiency.

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

Accepted Answer

The major loss in a Compression Ignition (CI) engine is due to incomplete combustion. This occurs when all the fuel is not completely burned during the combustion process, leading to inefficiencies and loss of potential energy that could have been converted to mechanical work.

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

Accepted Answer

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

Accepted Answer

In an SI engine, as speed increases, the throttle is more open to allow more air-fuel mixture, reducing the vacuum in the intake manifold and increasing pumping losses.

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

Accepted Answer

The volumetric efficiency of an engine is influenced by several factors including the exhaust gas remaining in the clearance volume, the design of the intake and exhaust valves, and the timing of the valves. These elements affect how efficiently the engine can draw in the air-fuel mixture and expel exhaust gases, thereby impacting its overall performance.

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

Accepted Answer

The air standard efficiency of an Otto cycle is more than that of a Diesel cycle for a given compression ratio because the Otto cycle operates on constant volume heat addition, which is more efficient than the constant pressure heat addition process of the Diesel cycle at the same compression ratio.

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

Accepted Answer

In a typical medium speed, 4-stroke cycle diesel engine, fuel injection usually starts just before the piston reaches the top dead center (TDC) to ensure that the fuel has enough time to mix with the air and start the combustion process as the piston starts its power stroke. Ending the injection after TDC allows for a complete and efficient burn of the fuel. The specific degrees mentioned in option A (starting at 10° before TDC and ending at 20° after TDC) are within the typical range for such engines, ensuring proper combustion and efficiency.

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

Accepted Answer

The calorific value of a fuel is the amount of heat released during its complete combustion per unit quantity. It is a critical property of fuels, indicating their energy content.

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

Accepted Answer

The calorific value of a fuel is a measure of the amount of energy released during its combustion. It is significant because it helps in deciding which fuel is more efficient or better for a specific use based on the amount of energy it can produce.

Question 13

Which gas has the highest calorific value among given option?
A)Oxygen
B)Helium
C)Hydrogen
D)Nitrogen

Accepted Answer

Hydrogen has the highest calorific value among the options given. It releases a large amount of energy per unit mass when it combusts, making it an efficient fuel.

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

Accepted Answer

Bomb calorimeter is specifically designed for determining the calorific value of solid and liquid fuels. It allows for the combustion of a sample in an oxygen-rich environment inside a strong, sealed container (bomb), facilitating the precise measurement of heat released.

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

Accepted Answer

Junker calorimeter is specifically designed for determining the calorific values of gaseous fuels.

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

Accepted Answer

The difference between the two heating values of fuel primarily depends on its chemical composition, as this determines how much energy is released during combustion.

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

Accepted Answer

The bomb calorimeter is designed to measure the calorific value of both solids and liquid fuels by combusting the fuel sample in a high-pressure oxygen environment to determine its heat of combustion.

Question 18

If the intake air temperature of I.C. engine increases, its efficiency will
A)increase
B)decrease
C)remain same
D)unpredictable

Accepted Answer

The efficiency of an internal combustion (I.C.) engine decreases with an increase in intake air temperature because the engine has to work harder to compress the warmer air, which reduces its overall efficiency.

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

Accepted Answer

The answer of All heat engines utilize
A)low heat value of...

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

Accepted Answer

The answer of Fuel oil consumption guarantees for I .C....

Quiz 3: Combustion and Efficiency in Engines

Dissociation can be considered as

Time loss factor in actual cycle is due to

The major loss in a SI engine is due to

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

The major loss in a CI engine is

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

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

The volumetric efficiency is affected by

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

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

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

What is the significance of calorific value?

Which gas has the highest calorific value among given option?

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

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

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

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

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

All heat engines utilize

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