Fuel Injection vs. Carburetors

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Questions and Answers

What is the primary factor that determines fuel supply in a carburetor system?

Pump pressure

Fuel speed at the point of injection

Air velocity passing through the throat (correct)

Engine temperature

Which of the following is NOT a listed advantage of fuel injectors?

Better acceleration and starting

Correct and uniform mixture distribution

Higher initial cost (correct)

Improved volumetric efficiency

In fuel injection systems, what is a critical requirement concerning the timing of fuel injection?

It should always be the same regardless of conditions

It can be easily changed without affecting performance

It should be uniform across all cylinders

It must vary according to engine load and speed (correct)

Which problem is commonly associated with carburetor systems in multi-cylinder engines?

Maldistribution of fuel Signup and view all the answers

What is the main function of the pumping element in a fuel injection system?

Move the fuel from the tank to the cylinder Signup and view all the answers

What is the primary function of the metering control in fuel injection systems?

To adjust the rate of fuel metering element according to engine demands Signup and view all the answers

Which of the following describes an advantage of using an air injection system?

It produces better mixing between air and fuel Signup and view all the answers

What type of injection system is characterized as 'Air-Less Mechanical Injection'?

Solid Injection System Signup and view all the answers

What role does the governor play in a fuel injection system?

To regulate the amount of fuel based on engine demands Signup and view all the answers

What is the consequence of not adjusting the fuel supply at higher engine speeds?

Excess fueling leading to poor combustion Signup and view all the answers

Why is proper atomization of fuel crucial in injection systems?

It increases evaporation and mixing with air in the cylinder Signup and view all the answers

What may occur at idling speeds if the fuel supply is not properly controlled?

Insufficient fuel can cause the engine to stall Signup and view all the answers

What effect does the design of a fuel injector have on combustion?

It affects the atomization and distribution of fuel in the combustion chamber Signup and view all the answers

How does an increase in engine load affect fuel supply from the pump?

It leads to excessive fuel delivery and possible carbon deposits Signup and view all the answers

What is a common feature of fuel injection systems that manage the pressure for fuel preparation?

Incorporation of both air and mechanical means Signup and view all the answers

Study Notes

Fuel Injection System

Fuel injection is a crucial component affecting the performance and operation of internal combustion engines (specifically, CI engines).
Both fuel injection and carburetors aim to prepare and deliver a combustible mixture to the engine, per its needs.
However, their methods differ.

Fuel Atomization

Both systems require fuel atomization before ignition for proper mixing with air.
For carburetors, incoming air velocity needs to be higher than fuel velocity.
Injectors require the fuel velocity to be greater at the injection point.

Fuel Supply

In carburetors, fuel supply depends on the amount and velocity of air passing through the throat.
Injectors rely on pump pressure for fuel supply.

Carburetor Problems

Maldistribution of fuel in multi-cylinder engines.
Loss of volumetric efficiency due to passage restrictions.
Freezing at low temperatures.
Surging in the secondary tank due to tilting.
Risk of fire from backfires.
Vapor leakage in extreme heat.
Excessive fuel supply.

Injector Advantages

Correct and uniform mixture distribution.
Improved volumetric efficiency.
Freedom from icing issues.
Better starting and acceleration.
Absence of tilting problems.
Better fuel control.

Injector Disadvantages

Higher initial cost and complex design.
High maintenance costs.
Bulkier and heavier.
More noisy.
Requires a specific fuel type.

Fuel Injection System Objectives

Meet engine demand for fuel volume.
Distribute fuel evenly to all cylinders.
Inject fuel at the correct time and rate.
Inject fuel with proper pattern and atomization for the combustion chamber design.
Inject fuel with abrupt start and stop to avoid dribbling.
Injection timing should adapt to engine load and speed.
System requires high reliability throughout its operation.

Functional Elements of Fuel Injection System

Pumping element: Moves fuel from the tank to the cylinder.
Metering element: Measures and supplies fuel at the rate determined by engine demand.
Metering control: Adjusts the rate of fuel metering according to engine needs.
Timing control: Adjusts the start and end of the injection process.
Mixing element: Atomizes and distributes fuel inside the combustion chamber.

Classification of Injection Systems

Air Injection Systems: Fuel is forced into the cylinder using compressed air. This is less common today, requiring multi-stage compressors.
Solid/Air-Less Injection Systems: Liquid fuel only is injected directly into the cylinder.

Injection Pump Governor

The injection pump governor regulates fuel delivery based on injection pump characteristics, air intake, and engine demand.
The governor adjusts fuel supply to match engine speed changes and load to prevent issues like stalling or excess fueling.

Fuel Injector

Fuel injector design impacts the rate and completeness of fuel combustion.
Atomizing fuel into small droplets increases surface area for better mixing with air and rapid vaporization.
This improves combustion speed and effectiveness.

Nozzle

The injector nozzle is crucial for liquid fuel spraying into the combustion chamber, ensuring atomization, and proper fuel distribution.
Factors affecting distribution of fuel include Injection pressure, air density in the cylinder, and fuel properties.
Preventing fuel from striking the combustion chamber walls is crucial to avoid carbon deposits.
Efficient fuel injection ensures proper mixing of air and fuel for optimal combustion.
Specific factors like fuel velocity, and areas like droplet size, should be accounted for in determining these rates.

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Description

Explore the key differences between fuel injection systems and carburetors in internal combustion engines, particularly focusing on their operations, fuel atomization, and supply mechanisms. This quiz will test your knowledge on how each system functions and their respective advantages and drawbacks.