50 Questions
What is the ignition delay period in a CI engine also known as?
Preparatory phase
Which curve does the pressure-time curve separate from during the start of combustion in a CI engine?
Motoring curve
Why is the ignition delay period in a CI engine extremely important?
Due to its impact on engine starting ability
What happens to fuel immediately upon injection into the combustion chamber of a CI engine?
It has an ignition delay period
What is the specific period of inactivity called between the time when fuel hits the hot air in the combustion chamber and the time it starts burning?
Ignition delay period
Where is the delay period shown on a pressure crank angle diagram in a CI engine?
Between points a and b
What causes diesel knock in a compression-ignition (CI) engine?
Improper fuel injection timing
How does an increase in engine speed affect the delay period in milliseconds?
Decreases the delay period
Which factor contributes to diesel knock related to injector nozzles?
Injector clogging
Why is controlling diesel knock essential for engine efficiency?
To optimize fuel injection systems
How does an increase in engine output affect the air-fuel ratio and delay period?
Decreases air-fuel ratio and increases delay period
What does a higher compression ratio in a CI engine lead to?
Increased diesel knock
What is the primary characteristic of diesel knock in a CI engine?
"Sharp metallic sound"
How does an increase in the minimum auto ignition temperature impact the delay period?
Decreases the delay period
Why might a CI engine with excessive carbon deposits experience knocking?
"Combustion knock"
What aspect does the Cetane number evaluate in diesel fuel used in CI engines?
Fuel's combustion characteristics.
What is the primary role of a higher Cetane number in diesel fuels?
Improve ignition characteristics
How does a higher Cetane number affect the ignition delay in diesel engines?
Shortens the ignition delay
What potential issue might arise from extremely high Cetane numbers in diesel fuels?
Increased engine knock
Why is efficient mixing of air and fuel essential in the combustion chamber of a CI engine?
To achieve optimal power generation
What is the purpose of a high compression ratio in Compression Ignition (CI) engines?
Promote better combustion efficiency
Why must the combustion chamber be robustly constructed in a CI engine?
To withstand high pressures and temperatures
How do the shape and geometry of the combustion chamber influence combustion in CI engines?
Impact turbulence and squish patterns
Why should the combustion chamber design be compatible with the engine's ignition system?
To ensure proper functioning of the engine's ignition system
What is the difference between the physical delay and the chemical delay?
Physical delay is the time between injection and ignition, while chemical delay is the time between ignition and rapid combustion.
In a compression-ignition engine, what role does the delay period play in the combustion process?
It allows for sufficient time for fuel atomization and mixing with air.
What factor influences the physical delay in the ignition process of an engine?
Compression ratio
Why is the physical delay shorter for light fuels compared to heavy viscous fuels?
Light fuels evaporate faster than heavy fuels.
Which phase is characterized by rapid pressure rise during combustion?
Uncontrolled Combustion Phase
How does the chemical delay differ from the physical delay in terms of impact on engine performance?
Chemical delay impacts heat release rate, while physical delay depends on fuel type.
What determines the duration of the period of rapid combustion in an engine?
Compression ratio
What distinguishes the ignition lag in spark ignition engines from that in compression-ignition engines?
In compression-ignition engines, ignition lag is essentially equal to chemical delay.
How do higher combustion chamber temperatures impact the physical delay?
Higher temperatures shorten physical delay by facilitating jet breakup and improving evaporation.
What role does high turbulence play in reducing the physical delay?
High turbulence reduces physical delay by improving fuel atomization and mixing with air.
Which component is crucial in preventing excessive temperatures within the combustion chamber?
Cooling passages
What technology is employed to control nitrogen oxide (NOx) emissions in modern CI engines?
Selective catalytic reduction (SCR)
What is the primary function of swirl in a combustion chamber?
Facilitate better mixing
Which method involves introducing fuel directly into the combustion chamber using high-pressure injectors?
Jet and Direct Injection
What type of motion does tumble refer to in the context of a combustion chamber?
Vertical swirling
Which design feature is responsible for enhancing turbulence by forcing the air-fuel mixture into the combustion zone?
Squish method
What role does the pre-chamber design play in enhancing turbulence within the combustion chamber?
Generating a high-velocity jet that enters the main chamber
How does the intake system contribute to turbulence within the combustion chamber?
By shaping the combustion chamber geometry
Which method is most effective in promoting efficient and rapid mixing of air and fuel in the combustion chamber?
Direct Injection
Which technology uses high-velocity jets to induce turbulence and initiate combustion in a controlled manner?
Turbulent Jet Ignition (TJI)
What is the purpose of introducing exhaust gas into the intake air using EGR (Exhaust Gas Recirculation)?
To reduce NOx emissions
In the context of combustion chambers for CI engines, which type features a shallow depth cavity in the piston?
Shallow Depth Chamber
What is the main advantage of open combustion chambers in CI engines?
Minimum heat loss during compression
What technology allows for the adjustment of valve timing, duration, and lift to influence air intake and exhaust processes?
Variable Valve Timing (VVT)
Which chamber type is defined as having a divided combustion space with pressure differences between compartments during combustion?
Indirect-Injection Chambers
What type of intake design can be tailored to induce turbulence in the incoming air-fuel mixture?
Intake Port Design
Learn about the different stages of combustion in Compression Ignition (C.I) engines, including the ignition delay period, rapid combustion, controlled combustion, and afterburning. Understand the sequence of events that occur during each stage.
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