Stages of Combustion in C.I Engines

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What is the preparatory phase of combustion in a CI engine known as?

Afterburning period

Controlled combustion period

Rapid combustion period

Ignition delay period (correct)

Which period exerts a significant influence on both engine design and performance in a CI engine?

Afterburning period

Controlled combustion period

Ignition delay period (correct)

Rapid combustion period

When does the ignition delay period begin in a CI engine?

Start of controlled combustion

Start of afterburning

Start of injection (correct)

Start of rapid combustion

What is the primary characteristic of the ignition delay period in a CI engine?

Fuel has not yet ignited after admission Signup and view all the answers

Why is the ignition delay period important in a CI engine?

It influences engine starting ability Signup and view all the answers

What happens during the ignition delay period in a CI engine?

There is a time gap between fuel injection and actual burning Signup and view all the answers

What is the purpose of generating turbulence in the combustion chamber of internal combustion engines?

To enhance combustion stability and reduce emissions Signup and view all the answers

How does the swirl method contribute to turbulence in the combustion chamber?

By inducing a rotational movement of the charge for better mixing Signup and view all the answers

What effect does the tumble method have on combustion efficiency and emissions?

It improves combustion efficiency and reduces emissions Signup and view all the answers

How does the squish method contribute to turbulence in the combustion chamber?

By forcing the mixture into the combustion zone for better mixing Signup and view all the answers

Which method employs high-pressure fuel injectors to introduce fuel directly into the combustion chamber?

Jet and Direct Injection method Signup and view all the answers

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 Signup and view all the answers

How does a modern CI engine control nitrogen oxide (NOx) emissions?

By implementing technologies like EGR and SCR in the combustion chamber Signup and view all the answers

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 Signup and view all the answers

Which of the following is NOT a method used to generate turbulence in the combustion chamber?

Cooling passages method Signup and view all the answers

How do high-velocity fuel jets contribute to turbulence in the combustion chamber?

By creating better atomization and mixing for enhanced combustion efficiency Signup and view all the answers

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 Signup and view all the answers

What is a primary cause of diesel knock in a compression-ignition engine?

Ignition of fuel in localized areas Signup and view all the answers

How does an increase in engine output affect the delay period in milliseconds?

Decreases the delay period Signup and view all the answers

Which factor can contribute to diesel knock due to uneven combustion?

Excessive carbon deposits Signup and view all the answers

How does the compression ratio of an engine influence diesel knock?

Makes engines less susceptible to knocking Signup and view all the answers

In a CI engine, what does 'diesel knock' refer to?

'Sharp metallic sound' Signup and view all the answers

What does the Cetane number evaluate regarding diesel fuel?

Ignition quality Signup and view all the answers

Why does the peak pressure reached may be high with an increase in engine output?

'Temperature and pressure rise of compressed air' Signup and view all the answers

What can alter the combustion process leading to knocking according to the text?

Poor spray patterns due to clogging Signup and view all the answers

How does an increase in compression temperature affect the delay period?

Decreases the delay period Signup and view all the answers

What is the physical delay period in the context of diesel engine combustion?

The time between injection and the attainment of chemical reaction conditions Signup and view all the answers

What is the chemical delay period influenced by in compression-ignition engines?

High compression ratios Signup and view all the answers

Which factor affects the physical delay of fuel ignition in diesel engines?

Compression ratio of the engine Signup and view all the answers

What is true about the ignition lag in compression-ignition (CI) engines?

It is shorter than the duration of injection in most CI engines Signup and view all the answers

Why does the physical delay period decrease with high turbulence in the combustion chamber?

To facilitate breakup of the fuel jet and improve evaporation Signup and view all the answers

What characterizes the period of rapid combustion in a diesel engine?

Presence of fresh air around fuel droplets Signup and view all the answers

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 Signup and view all the answers

What role does autoignition temperature play in determining the chemical delay period?

Autoignition temperature decreases due to increased density of compressed air Signup and view all the answers

In a compression-ignition engine, what is crucial for achieving efficient and clean combustion?

Optimal control of the delay period Signup and view all the answers

Which design factor significantly affects the delay period in diesel engine combustion?

Compression ratio Signup and view all the answers

What is the relationship between the Cetane number and the ignition delay in diesel engines?

Higher Cetane number results in a shorter ignition delay. Signup and view all the answers

Why is it essential to balance the Cetane number in diesel fuels?

To comply with environmental regulations on fuel quality. Signup and view all the answers

What is the primary function of the combustion chamber in a Compression Ignition (CI) engine?

To facilitate the combustion process that powers the engine. Signup and view all the answers

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. Signup and view all the answers

How does a high compression ratio contribute to the performance of a CI engine?

It promotes better combustion efficiency. Signup and view all the answers

Why must the construction of a combustion chamber in a CI engine be robust?

To ensure longevity and reliability under high pressures and temperatures. Signup and view all the answers

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. Signup and view all the answers

Why should the combustion chamber design be compatible with the engine's ignition system?

To ensure effective ignition during the combustion process. Signup and view all the answers

What happens when diesel fuels with higher Cetane numbers are used in engines?

They contribute to smoother engine operation and lower emissions. Signup and view all the answers

Which aspect of the Cetane number affects combustion efficiency in diesel engines?

It impacts how quickly and completely fuel ignites. Signup and view all the answers

What is the purpose of using Bowl-in-piston designs in diesel engines?

To create controlled turbulence during compression and combustion processes Signup and view all the answers

Which technology uses high-velocity jets to induce turbulence and initiate combustion in a controlled manner?

Turbulent Jet Ignition (TJI) Signup and view all the answers

What is a common use of EGR (Exhaust Gas Recirculation) in engines?

Reduce emissions Signup and view all the answers

Which type of combustion chamber requires high fuel-injection pressure and complex design of fuel injection pump?

Direct-Injection Chambers Signup and view all the answers

What is the main advantage of Shallow Depth Chambers in engines?

Minimum squish effect Signup and view all the answers

In which type of combustion chamber is the combustion space divided into two or more distinct compartments connected by restricted passages?

Indirect-Injection Chambers Signup and view all the answers

What is the specific purpose of Swirl Chambers in engines?

To mix air and fuel more effectively through strong rotary movement Signup and view all the answers

What distinguishes an open combustion chamber from a divided combustion chamber?

Single cavity with little restriction Signup and view all the answers

Why is EGR (Exhaust Gas Recirculation) commonly used in engines?

To reduce emissions by altering air-fuel mixture composition Signup and view all the answers

What do Variable Valve Timing (VVT) systems influence by optimizing valve events?

Air intake and exhaust processes Signup and view all the answers