Presented By:

PATEL YASH S. (150123119039)

Branch:- Mechanical

Semester:-6th (D)

Subject:-Internal Combustion Engine(2161902)

Active Learning Assignment (ALA)Topic:-Simple Carburetor

05/02/23 1

GANDHINAGAR INSTITUTE OF TECHNOLOGY

MECH 6 D3 ICE

Content

Introduction Simple carburetor Operation of carburetor Ideal system Auxiliary port system Types of carburetor based on direction Limitation

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Introduction The process of mixture preparation in an SI engine is called

carburetion. This air fuel mixture is prepared outside the cylinder in a device called CARBURETOR.

It must supply correct amount of air fuel mixture in correct proportion under all load condition and speed of the engine.

It must run engine smoothly by supplying a correct mixture strength.

Carburettor is a device which is generally used for mixing air and fuel in the proper quantities, to achieve the sufficient air-to-fuel ratio needed for the proper operation of an engine

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Simple Carburetor A float chamber with a float to store fuel and to adjust its

level. A round cylinder with a venturi for atomization of fuel. A fuel nozzle to atomize and produce a spray of fuel. A throttle valve to supply varying quantity of the mixture at

different load condition. A choke valve to control the air supply in order to provide a

rich or a lean mixture.

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Operation

The fuel supply to the float chamber is controlled by the action of the float and the attached fuel supply valve. During the intake or the suction stroke of the engine, the piston moves from TDC to BDC, and creates a vacuum in the space above it and in the suction manifold. Due to this fall in pressure, the atmospheric air rushes into the carburetor. Near the venturi, velocity increase, pressure decreases and the fuel comes out in the form of a jet. The fuel gets mixed with air and goes into the cylinder.

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Operation Because of the narrow passage at the venturi throat, the air

velocity increases but its pressure falls. This causes a partial vacuum (called carburetor depression) at the venturi throat. This carburetor depression causes fuel to come out as jet in the form of a spray. This fuel spray vaporizes and mixes with the incoming air and the mixture goes into the cylinder through the throttle valve.

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Idling System During starting or idling, engine runs without load and the

throttle valve remains in closed position. Engine produces power only to overcome friction between the parts, and a rich mixture is to be fed to the engine to sustain combustion.

The idling system as shown consist of an idling port. When the throttle is partially closed, a depression past the throttle allows the fuel to go into intake through the idle tube. The fuel flow depends on the location of the idle nozzle and the adjustment of the idle screw.

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Auxiliary Port System

In auxiliry air valve provides extra air at higher load on engine.when load on engine increase ,the vaccume in ventury increses and hence ,this valve open and allow additional air.therefore ,the mixture is prevented from becoming over rich.

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Types of simple carburator The Simple Carburetor may be of following three types based on

direction of flow.1. Updraft Type:-In this, the air enters the carburetor at the bottom

and leaves at the top.2. Downdraft Type:-In this, air enters the carburetor at the top and

leaves at the bottom. This used most passenger cars because it can be installed at a higher level in the engine which makes it more accessible for the purpose of inspection and repair.

3. Horizotal carburator:-It consist the horizontal jet tube. Such a carburetor has the advantage where under bonnet space is limited and also the resistance to flow is reduce due to elimination of one right angled turn in the intake passage.

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Limitations During sudden acceleration , rich mixture is required which can not be

provided by simple carburator. It do not provide rich mixture during starting and idling. During idling,starting and low speed rich mixture is required but in

this carburator during this peroid throttel is nearly close which do not produce sufficient difference for fuel flow

At high speed mixture richness is atomatically increase which is not required,this is due to large pressure difference at fuel jet at high speed,so mass floe rate of fuel increase at greater rate compared to air,so rich mixture available.

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Thank You…Thank You…

MECH 6 D3 ICE