copy of carburettion & injection

CARBURETION & INJECTION Copyright Gautam Malik 2007C

Engine Fuel System


Petrol Engines


Fuel/Air ratioThe purpose of the carburettor in case of Petrol Engines is to mix air and fuel, So the fuel/air ratio is theoretically 1:14,6. When the supply of airis more, the ratio gets higher than 1:14,6 i.e. a leaner mixture, there still will be some free oxygen left in the exhaust gases. If the supply of fuel is more than air the ratio gets below 1:14 i.e. a richer mixture,there will be no free oxygen left but some fuel will leave the engine unused.


Carburettor


Venturi-type Carburetor

P+1/2 V2 = Constant

Bernoulli Effect:

Constant level is maintained in bowl -as float moves down, valve stem moves down, allowing more fuel into bowl, float moves up and closes valve

Valve StemFuel Inlet

Float

Metering Orifice

Throttle Plate

Air/Fuel Mixture To Engine

Choke Plate

Fuel Nozzle

Inlet Air

Bowl

Atomized Fuel

Venturi


Desirable Features

1 To meter & supply the correct amount of air fuel mixture ratios under all conditions of load & speed of the engine for

• Easily Starting

• Providing rich mixture forslow idling

• Providing rich mixture for aceleration

• Providing rich mixture for high speed

2 To operate satisfactorily during hot & cold weathers

3 To be robust

4 To withstand the density changes for varying altitudes.


Main Systems

• Float System

• Idle System

• Main Metering System

• Power System

• Accelerator Pump System

• Choke System


Float System


Idle System


Low Speed Operation


Main Metering System


Metering Rod Types

• Tapered

• Stepped


Tapered Rod


Stepped Rod


Power System


Accelerator Pump System


Choke System


Diesel Fuel System

In diesel fuel system only air is sucked into the cylinder during the intake stroke.

The combustion of fuel takes place as soon as the diesel is injected into the cylinder prior to power stroke.


The injection in case of diesel engine is executed with the help of Fuel Injection Pump(FIP)in conjunction to the nozzles /injectors.

The Main parts of the FIP are

• FIP driving gear

• FIP Cam Shaft

• Followers

• Plungers

• Barrels

• Retaining Springs

• Governor

• Spring Loaded rack arrangement


Main Parts


No Delivery


Full Delivery


Partial Delivery


Barrel


Mechanical Injectors


Nozzle


Fuel Injection


Multi Point Fuel Injection(MPFI)

50 psi typical

Monitored Engine Operating Conditions:

Manifold PressureEngine Speed

Air TemperatureCoolant Temperature

Acceleration

COMPUTERTRIGGER

INJECTOR DRIVE UNIT

Pressure Regulator FuelFilter

Fuel Pump

FUEL TANK

Injectors


THANK YOU

copy of carburettion & injection

Documents

supply of fuel

combustion of fuel

air fuel mixture ratios

case of diesel engine

engine unused

leaner mixture

richer mixture

engine operating conditions