56 Questions
What is the preparatory phase of combustion in a CI engine known as?
Ignition delay period
Which period exerts a significant influence on both engine design and performance in a CI engine?
Ignition delay period
When does the ignition delay period begin in a CI engine?
Start of injection
What is the primary characteristic of the ignition delay period in a CI engine?
Fuel has not yet ignited after admission
Why is the ignition delay period important in a CI engine?
It influences engine starting ability
What happens during the ignition delay period in a CI engine?
There is a time gap between fuel injection and actual burning
What is the purpose of generating turbulence in the combustion chamber of internal combustion engines?
To enhance combustion stability and reduce emissions
How does the swirl method contribute to turbulence in the combustion chamber?
By inducing a rotational movement of the charge for better mixing
What effect does the tumble method have on combustion efficiency and emissions?
It improves combustion efficiency and reduces emissions
How does the squish method contribute to turbulence in the combustion chamber?
By forcing the mixture into the combustion zone for better mixing
Which method employs high-pressure fuel injectors to introduce fuel directly into the combustion chamber?
Jet and Direct Injection method
What role does the pre-chamber design play in enhancing turbulence within the combustion chamber?
Induces a high-velocity jet to enter the main chamber for turbulence
How does a modern CI engine control nitrogen oxide (NOx) emissions?
By implementing technologies like EGR and SCR in the combustion chamber
What is one of the key functions of piston-bowl designs in a CI engine's combustion chamber?
To promote efficient air-fuel mixing and combustion stability
Which of the following is NOT a method used to generate turbulence in the combustion chamber?
Cooling passages method
How do high-velocity fuel jets contribute to turbulence in the combustion chamber?
By creating better atomization and mixing for enhanced combustion efficiency
What factor contributes to the decrease in delay period in milliseconds with an increase in engine speed?
Rise of temperature and pressure of compressed air
What is a primary cause of diesel knock in a compression-ignition engine?
Ignition of fuel in localized areas
How does an increase in engine output affect the delay period in milliseconds?
Decreases the delay period
Which factor can contribute to diesel knock due to uneven combustion?
Excessive carbon deposits
How does the compression ratio of an engine influence diesel knock?
Makes engines less susceptible to knocking
In a CI engine, what does 'diesel knock' refer to?
'Sharp metallic sound'
What does the Cetane number evaluate regarding diesel fuel?
Ignition quality
Why does the peak pressure reached may be high with an increase in engine output?
'Temperature and pressure rise of compressed air'
What can alter the combustion process leading to knocking according to the text?
Poor spray patterns due to clogging
How does an increase in compression temperature affect the delay period?
Decreases the delay period
What is the physical delay period in the context of diesel engine combustion?
The time between injection and the attainment of chemical reaction conditions
What is the chemical delay period influenced by in compression-ignition engines?
High compression ratios
Which factor affects the physical delay of fuel ignition in diesel engines?
Compression ratio of the engine
What is true about the ignition lag in compression-ignition (CI) engines?
It is shorter than the duration of injection in most CI engines
Why does the physical delay period decrease with high turbulence in the combustion chamber?
To facilitate breakup of the fuel jet and improve evaporation
What characterizes the period of rapid combustion in a diesel engine?
Presence of fresh air around fuel droplets
How does the duration of the delay period impact pressure rise during rapid combustion in a diesel engine?
Short delay periods lead to more rapid pressure rise
What role does autoignition temperature play in determining the chemical delay period?
Autoignition temperature decreases due to increased density of compressed air
In a compression-ignition engine, what is crucial for achieving efficient and clean combustion?
Optimal control of the delay period
Which design factor significantly affects the delay period in diesel engine combustion?
Compression ratio
What is the relationship between the Cetane number and the ignition delay in diesel engines?
Higher Cetane number results in a shorter ignition delay.
Why is it essential to balance the Cetane number in diesel fuels?
To comply with environmental regulations on fuel quality.
What is the primary function of the combustion chamber in a Compression Ignition (CI) engine?
To facilitate the combustion process that powers the engine.
Why is efficient mixing of air and fuel crucial in the combustion chamber of a CI engine?
To achieve a uniform and controlled combustion process.
How does a high compression ratio contribute to the performance of a CI engine?
It promotes better combustion efficiency.
Why must the construction of a combustion chamber in a CI engine be robust?
To ensure longevity and reliability under high pressures and temperatures.
How does the shape and geometry of the combustion chamber affect combustion in a CI engine?
It influences turbulence, swirl, and squish patterns during combustion.
Why should the combustion chamber design be compatible with the engine's ignition system?
To ensure effective ignition during the combustion process.
What happens when diesel fuels with higher Cetane numbers are used in engines?
They contribute to smoother engine operation and lower emissions.
Which aspect of the Cetane number affects combustion efficiency in diesel engines?
It impacts how quickly and completely fuel ignites.
What is the purpose of using Bowl-in-piston designs in diesel engines?
To create controlled turbulence during compression and combustion processes
Which technology uses high-velocity jets to induce turbulence and initiate combustion in a controlled manner?
Turbulent Jet Ignition (TJI)
What is a common use of EGR (Exhaust Gas Recirculation) in engines?
Reduce emissions
Which type of combustion chamber requires high fuel-injection pressure and complex design of fuel injection pump?
Direct-Injection Chambers
What is the main advantage of Shallow Depth Chambers in engines?
Minimum squish effect
In which type of combustion chamber is the combustion space divided into two or more distinct compartments connected by restricted passages?
Indirect-Injection Chambers
What is the specific purpose of Swirl Chambers in engines?
To mix air and fuel more effectively through strong rotary movement
What distinguishes an open combustion chamber from a divided combustion chamber?
Single cavity with little restriction
Why is EGR (Exhaust Gas Recirculation) commonly used in engines?
To reduce emissions by altering air-fuel mixture composition
What do Variable Valve Timing (VVT) systems influence by optimizing valve events?
Air intake and exhaust processes
Learn about the four stages of combustion in a Compression Ignition (C.I) engine, including the ignition delay period, rapid combustion period, controlled combustion period, and afterburning period. Explore the details of each stage and their significance in the combustion process.
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