68 Questions
What is the main function of a heat engine?
Turning the chemical energy of a fuel into thermal energy for mechanical work
Which type of engine transfers heat to a second fluid that is the working fluid of the cycle?
External combustion engine
What type of engine has the combustion of air and fuels taking place inside the cylinder?
Reciprocating engine
Which type of engines use a turbine for their basic design?
Rotary engine
What distinguishes a four-stroke engine from a two-stroke engine?
The number of strokes per cycle
In which type of heat engine does the combustion of air and fuels take place directly in the cylinder?
Internal combustion engine
What type of engine has combustion of air-fuel inside the engine cylinder?
Diesel engine
Which type of engine uses cheaper fuels including solid fuels?
External combustion engine
What is the function of piston rings in a reciprocating IC engine?
Provide an airtight seal to prevent gas leakage
Which component of a reciprocating IC engine is responsible for transmitting the force exerted by the burning of the charge to the connecting rod?
Piston
What is the main purpose of a cylinder head in an IC engine?
Provide an airtight seal at the top of the cylinder
In which type of engine is a boiler used for combustion of air-fuel?
External combustion engine
Which type of ring on the piston provides an effective seal to prevent oil leakage into the engine cylinder?
Oil ring
What is the main function of connecting rod in a reciprocating IC engine?
Convert reciprocating motion into circular motion
What is the significance of using special alloys in internal combustion engines?
To withstand high pressure and temperature
What feature distinguishes between single-cylinder and multi-cylinder engines?
Cylinder arrangement
What is the reverse process to combustion?
Dissociation
At what temperature does the dissociation of CO2 into CO and O2 start commencing?
1000°C
Which gases tend to prevent the dissociation of CO2?
CO and O2
In internal combustion engines, what causes a reduction in the maximum temperature and pressure?
Heat transfer to the cooling medium
What reduces the maximum temperature by about 300°C even at the chemically correct air-fuel ratio?
Dissociation
What is the effect of dissociation on output power in a spark-ignition engine?
Decreases output power
What process can be looked at as the disintegration of combustion products at high temperature?
Dissociation
What is the function of the crankshaft in an internal combustion engine?
Converts reciprocating motion of the piston into rotary motion
Which alloy is commonly used for manufacturing the connecting rod in an internal combustion engine?
Aluminum alloys
What is the Dead Centre in an internal combustion engine?
Position at the end point of the stroke where piston direction is reversed
What is the main function of a flywheel in an internal combustion engine?
Stores excess energy during power stroke to maintain speed constant
In a four-stroke engine, what happens during the suction stroke?
Suction valve open, fresh air-fuel charge drawn into the cylinder
Which engine has a heavier flywheel due to non-uniform turning movement?
Four-stroke engine
What is the role of the clearance volume in an internal combustion engine?
Volume of space on the combustion side of the piston at top dead centre
Which term refers to the nominal volume generated by the working piston between two dead centres?
Swept volume
'Volumetric efficiency' in an internal combustion engine relates to what aspect of its operation?
'Volumetric efficiency' refers to the air-fuel mixture drawn into the cylinder compared to its total volume.
'Compression ratio' in an internal combustion engine is defined as what?
'Compression ratio' is the ratio of swept volume to clearance volume.
What is the expansion ratio or pressure ratio in an Otto cycle?
rp = p3/p2
During which process in the Otto cycle is heat rejected to an external sink?
Constant Volume Heat Rejection Process
What is the characteristic gas constant R in relation to specific heats?
R = Cp - Cv
At what temperature range do gases generally show an increase in specific heat?
300 K to 2000 K
What is the relationship between temperature T2 and T1 during adiabatic compression in an Otto cycle?
$T2 = T1(1-r^{(\gamma-1)})$
Which equation represents the increase in specific heat for gases at higher temperatures?
$Cp = a_1 + k_1T + k_2T^2$
What happens to the final temperature and pressure if variable specific heats are considered during the compression stroke in an Otto cycle?
They decrease
What does the difference between Cp and Cv depend on for gases?
$T$
What is the value of specific heat for air at 300 K?
$Cp = 1.005 kJ/kg K$
What is the work done formula in an Otto cycle?
$W = Cp(T3-T2) - Cv(T4-T1)$
What is a characteristic of a two-stroke engine?
One power stroke in each revolution of the crankshaft
Why is the flywheel lighter in a two-stroke engine?
As a result of more uniform turning movement
What is a downside of a two-stroke engine?
Higher rate of wear and tear
Which type of engine uses the Otto cycle?
SI engine
What is a characteristic of a diesel engine?
Low self-ignition temperature
What type of heat addition does the Otto cycle operate with?
Isochoric
What assumption is made about the gas in the cylinder for air-standard cycles?
'Air' obeys gas laws and has constant specific heats
Why is the air-cycle approximation used despite not closely representing actual cylinder conditions?
To obtain approximate answers to complex engine problems
What defines the simplest theoretical cycle used for calculating conditions in internal combustion engines?
'Air' acting as a perfect gas with certain assumptions
What happens to the maximum temperature as the air-fuel ratio decreases in an internal combustion engine?
Increases
Why are dissociation effects less pronounced in a CI engine compared to an SI engine?
Presence of excess air and heterogeneous mixture
How does dissociation affect the pressure in the expansion stroke of an internal combustion engine?
Decreases pressure
Which type of loss occurs when combustion gases leak past the piston rings into the crankcase?
Blowby Losses
What is the main cause of incomplete combustion in an internal combustion engine?
Ineffective spark-ignition and combustion
How do exhaust heat losses affect the overall efficiency of an internal combustion engine?
Reduce efficiency
Which process in the Otto Cycle corresponds to spark-ignition and combustion in an actual engine?
2?3
Why do engine designers work to minimize friction losses between moving engine components?
To improve overall efficiency
What effect does a rich mixture have on dissociation effects in an internal combustion engine?
Increases dissociation effects
What is the primary reason for lower peak gas temperatures in a compression-ignition (CI) engine compared to a spark-ignition (SI) engine?
Heterogeneous mixture composition and excess air in CI engines
What is the expression for the thermal efficiency of an Otto cycle?
1 - (T4 - T1)/(T3 - T2)
What is the impact of increasing the compression ratio on the thermal efficiency of an Otto cycle?
Increases efficiency
What does the thermal efficiency of an Otto cycle depend on?
Compression ratio only
In the Otto cycle, what is the relationship between temperatures T1, T2, T3, and T4?
T1 = T2, T3 = T4
What factor contributes to increasing the efficiency of an Otto cycle?
Increasing the compression ratio
How is the net work output for an Otto cycle represented?
(p3V3 - p4V4)/(x-1) - (p2V2 - p1V1)/(x-1)
Learn about the basics of internal combustion engines and heat engines, which transform chemical energy into thermal energy to produce mechanical work. Explore the classification of heat engines into external and internal combustion engines.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
