Carburettor MCQ Quiz in বাংলা - Objective Question with Answer for Carburettor - বিনামূল্যে ডাউনলোড করুন [PDF]

Primary swirl/induction swirl is usually obtained by two methods :

i) By careful formation of the air intake passages.

ii) By masking or shrouding a portion of the circumference of inlet valve.

The air fuel ratio for different operations is given below

Idling – 10

Cruising – 16

Maximum Power – 13

Explanation:

Carburettor:

• The carburettor is a device used in petrol engines for atomising and vaporising the fuel and mixing it with air in varying proportions to suit the charging mixture in the induction manifold of the engine.
• The carburettor meters the required quantity of fuel and atomises or breaks it into minute globules for being mixed with a correct quantity of air.
• The main object of the carburettor is to supply the required petrol and air mixture of the correct strength as dictated by the load conditions of the engine.
• A simple carburettor supplies the particular air-fuel ratio at a particular throttle position. The mixture gets richer as the throttle opening gets increasing. So the rich mixture is supplied at the accelerating position.
• Theoretically 15: 1 is the correct mixture of air and petrol which would result in burning without leaving an excess of air and fuel.
• Combustion will take place for the ratio between 7: 1 to 10: 1 on the lower side and up to 20: 1 on the higher side.
• For average cruising speed, the air-fuel ratio is approximately 15: 1 to 17: 1 
• A richer mixture of 12:1 is desirable for accelerating the engine quickly, when starting the engine from cold, even richer mixture may be desired.
• For maximum economy, i.e., less fuel consumption per unit power, the fuel-air ratio should be 16: 1 or 17: 1.

Thus, the carburettor has to be designed to provide varying requirements of fuel-air ratios.

The process of formation of a combustible fuel air mixture by mixing the proper amount of fuel with air before admission to engine cylinder is called carburetion and the device which does this job is called a carburettor.

Thus carburettor supply mixture of air and fuel with maintained air petrol ratio, generally used in petrol engine.

GDI Engines:

The carburettor of conventional SI engines, is being replaced by multipoint fuel injection (MPFI) system in which fuel is injected into the intake manifold (called port injection), instead of into the combustion chamber as in CI engine. GDI, also known as petrol direct injection, is a mixture formation system for SI engines that run on gasoline, in which fuel is directly injected into the combustion chamber, in contrast to the older port fuel injection system or MPFI system. The GDI is proving to be a promising technology to increase engine efficiency and specific power output simultaneously and to reduce exhaust emissions potentially.

Flywheel: It regulates the fluctuation in the crankshaft speed. It absorbs the energy during the power stroke and supplies the energy during compression and other strokes.

Cam: It regulates the opening and closing of valves of the cylinder. It is run through the crankshaft.

Crankshaft: This is the main shaft of the engine. It converts the reciprocating motion of pistons to the rotary motion.

Due to less amount of fuel and more amount of air, thermal efficiency at leaner mixture will be high but due to less amount of fuel heat generated will be less and hence less power output.

Explanation:

Internal Combustion Engines (IC Engines):

• Internal Combustion (IC) engines are mechanical devices that convert chemical energy from fuel into mechanical energy by burning the fuel-air mixture inside a combustion chamber. These engines are widely used in automobiles, power plants, and other industrial applications. Depending on various parameters, IC engines are classified into different categories. One such classification is based on the method of fuel injection, which divides IC engines into carburetor engines and air injection engines.

Method of Fuel Injection

This classification is based on how the fuel is supplied to the combustion chamber:

• Carburetor Engine: In this type of engine, a carburetor is used to mix air and fuel in the correct proportion before it enters the combustion chamber. The carburetor plays a crucial role in maintaining the air-fuel ratio, ensuring proper combustion. These engines are commonly found in older vehicles and smaller engines, such as motorcycles and lawnmowers. However, carburetor engines have been largely replaced by more advanced fuel injection systems in modern vehicles due to their limitations in efficiency and precision.
• Air Injection Engine: In air injection engines, fuel is injected directly into the combustion chamber using a high-pressure air stream. This method ensures better atomization of fuel, leading to improved combustion efficiency and reduced emissions. Air injection engines are often used in heavy-duty applications, such as large diesel engines, where precise fuel delivery and combustion control are crucial.

Explanation:

Simple Carburetor:

• A simple carburetor is a critical component in petrol (spark-ignition) engines. Its primary function is to atomize and mix fuel with air in the proper ratio required for efficient combustion. The carburetor ensures that the engine receives the correct air-fuel mixture for various operating conditions, such as idling, acceleration, cruising, and deceleration.
• In a petrol engine, the combustion process requires a specific air-fuel ratio for optimal performance. The ideal ratio, known as the stoichiometric ratio, is approximately 14.7:1, meaning 14.7 parts of air to 1 part of fuel by weight. However, depending on the operating conditions, the engine may require a richer (more fuel) or leaner (less fuel) mixture. The carburetor is designed to adjust the air-fuel mixture dynamically to meet these requirements.

Working of a Simple Carburetor:

• Air Flow: Air enters the carburetor through the air intake. The airflow is controlled by a throttle valve, which adjusts the engine's power output by changing the volume of air entering the engine.
• Fuel Atomization: Fuel is drawn from the fuel reservoir into the carburetor's venturi, a narrow passage where the air velocity increases, creating a low-pressure zone. This pressure difference causes the fuel to atomize, breaking it into tiny droplets.
• Air-Fuel Mixing: The atomized fuel mixes with the incoming air to form a homogenous air-fuel mixture. The mixture's composition is regulated using jets and needles within the carburetor.
• Delivery to Combustion Chamber: The air-fuel mixture is then delivered to the engine's combustion chamber, where it is ignited by the spark plug to produce power.