petrol engine Carburation
-
Upload
prof-jignesh-sohaliya -
Category
Documents
-
view
234 -
download
0
Transcript of petrol engine Carburation
-
8/12/2019 petrol engine Carburation
1/42
CARBURATION
PROF. JIGNESH SOHALIYA
JMS
-
8/12/2019 petrol engine Carburation
2/42
PURPOSE OF CARBURATION
S.I engine uses volatile fuels
Formation of a homogenous mixture is normally not completed in inlet
Purpose of carburation is to provide a combustible mixture of fuel & air in required quantity &operation of the engine under all condition.
WHAT IS CARBURATION?
The process of formulation of fuel & air mixture by mixing the proper amount of fuel with air
engine cylinder.
FACTOR AFFECTING CARBURATION
1. Engine speed
2. Vaporization characteristics of the fuel
3. Temp. Of incoming air
4. Design of carburetor
JMS
-
8/12/2019 petrol engine Carburation
3/42
HIGHER SPEED ENGINE
At 3000rpmonly 10 milliseconds for mixture induction during intake
For 6000rpm- 5 milliseconds
Therefore velocity of the air stream at the point where fuel is injected has to be increase.
This is achieved by venture section in the air.
VAPORIZATION OF FUEL
Presence of high volatile hydrocarbons in fuel.
Distillation curve are necessary for efficient carburation especially at high speed.
TEMP. OF INCOMING AIR
High atmospheric air high temp. Of fuel
Produces more homogenous mixture & reduction in its volumetric efficiency.JMS
-
8/12/2019 petrol engine Carburation
4/42
PROPER DESIGN OF CARBURETOR ELEMENTS ALONE ENSURE THE SUPPLY OF DESIRE COM
MIXTURE UNDER DIFFERENT CONDITIONS.
COMPLETE COMBUSTION MEANS ALL CARBONE IN FUEL CONVERTED IN TO CO2 & ALL HY
AIR FUEL MIXTURES
1. Chemically correct mixture or stoichiometric (15:1)
2. Rich mixture (less air 12:1 , 10:1)
3. Lean mixture (more air 17:1, 20:1)
JMS
-
8/12/2019 petrol engine Carburation
5/42
MIXTURE REQUIREMENT AT DIFFERENT LOADS AND SPEED
Air fuel ratio at which engine operates has a considerable
influence on its performance
For high speed & low speed engine a/f ration is varying.
A/F ratio will affect both the POWER OUTPUT & BRAKE
SPECIFIC FUEL CONSUPTION. Best power mixture (12:1) is much richer than chemically
corrected mixture.
Best economy(16:1) is slightly leaner than chemically correct.
JMS
-
8/12/2019 petrol engine Carburation
6/42
As indicated in fig. there are three general
ranges of throttle operation. In each of this engine requirements different.
Ranges are.
1. Idling (mixture must be enriched)
2. Cruising (mixture must be leaned)3. High power (mixture must be enriched)
JMS
-
8/12/2019 petrol engine Carburation
7/42
JMS
-
8/12/2019 petrol engine Carburation
8/42
SIMPLE CARBURETOR
JMS
-
8/12/2019 petrol engine Carburation
9/42
JMS
-
8/12/2019 petrol engine Carburation
10/42
JMS
-
8/12/2019 petrol engine Carburation
11/42
LIMITATION OF SIMPLE CARBURETOR
IT DO NOT PROVIDE RICH MIXTURE DURING STARTING & IDLING. THROTTLE IS NEARLY CLO
PRODUCE SUFFICIENT PRESSURE DIFFERENCE FOR FUEL.
DURING SUDDEN ACCELERATION RICH MIXTURE IS REQUIRED WHICH CAN NOT PROVIDE B
AT HIGHER SPEED MIXTURE RICHNESS IS AUTOMATICALLY INCREASE.
JMS
-
8/12/2019 petrol engine Carburation
12/42
MODIFICATIONS OF SIMPLE CARBURETOR
1. STARTING DEVICE(CHOCK)
2. IDLING DEVICE
3. MAIN METERING SYSTEM4. POWER ENRICHMENT
5. ACCELERATION PUMP
JMS
MAIN METERING SYSTEM
-
8/12/2019 petrol engine Carburation
13/42
MAIN METERING SYSTEM FOR WIDE RANG OF SPEED & LOAD OF THE ENGINE ----- A/F
RATIO IS VARIES
1. COMPENSATING JET
IT PROVIDES EXTRA AIR FLOW WHEN MAIN JET PROVIDES
MORE FUEL DURING HIGH SPEED.
AREA OF MAIN JET AND COMPENSATING JET IS EQUAL TO
SINGLE JET.
INCREASING SPEEDMAIN JET & C.J DELIVER MORE
FUEL(RICH).
THE FLOW OF FUEL THROUGH COMPENSATING JETINCREASES WITH INCREASING SPEED BUT THE FLOW OF FUEL
FROM THE FLOAT CHAMBER TO COMPENSATING WELL IS
RESTRICTED BY ORIFICE.
COMPENSATING JET DELIVER LEAN MIXTURE & IT IS MAINTAIN
BY MAIN JET UNDER HIGH SPEED.JMS
Emulsion tube
-
8/12/2019 petrol engine Carburation
14/42
Emulsion tube
Main metering jet is kept at level of 25mmbelow
the fuel level in float chamber therefore its called
SUBMERGED JET.
Jet located on the bottom of the well.
The side of the well have holes. Holes are incommunication with atmosphere.
When throttle is open pressure at venturi throat
decreasing & petrol is drawn into the air stream.
This result uncovering the holes in central tube
leading to increasing air fuel ratio or decreasing
richness of mixture when all holes are uncover. Normally flow take place from the main jet.
JMS
-
8/12/2019 petrol engine Carburation
15/42
JMS
BACK SUCTION CONTROL
-
8/12/2019 petrol engine Carburation
16/42
BACK SUCTION CONTROL
TOP OF THE FUEL FLOAT CHAMBER IS CONNECTED
TO AIR ENTRY BY MEANS OF CONTROL VALVE.
ANOTHER LINE A SMALL ORIFICE CONNECTS THE
TOP OF THE FUEL FLOAT CHAMBER WITH THE
VENTURI THROAT.
WHEN C.V OPEN LINE IS UNRESTRICTED FLOAT
CHAMBER IS (P1) & THROAT PRESSURE WILL BE P2.
IF THE VALVE IS CLOSED THEN FLOAT CHAMBER
PRESSURE IS EQUAL TO THROAT PRESSURE SO NO
FUEL CAN FLOW.
ALTERING THE QUANTITY OF FUEL DISCHARGED
FROM THE NOZZLE THE REQUIRED AIR FUEL RATIO
MIXTURE CAN BE ACHIEVED.
ONLY FOR LARGE CARBURETORS.JMS
ECONOMIZER OR POWER ENRICHMENT
-
8/12/2019 petrol engine Carburation
17/42
ECONOMIZER OR POWER ENRICHMENT
SYSTEM
MAX. POWER RANGE RICH AIR FUEL RATIO
IS REQUIRED.
ECONOMIZER IS DEVICE WHICH REMAINS
CLOSED AT NORMAL CRUISING RANG.
IT REGULATES ADDITIONAL FUEL SUPPLY
DURING THE FULL THROTTLE.
JMS
AUXILIARY VALVE
-
8/12/2019 petrol engine Carburation
18/42
AUXILIARY VALVE
PROVIDES EXTRA AIR AT HIGHER
LOAD ON ENGINE
LOAD INCREASING VACUUM IN
VENTURE INCREASING & HENCE
AUXILIARY VALVE IS ALLOW
ADDITIONAL AIR.
JMS
-
8/12/2019 petrol engine Carburation
19/42
SOLEX CARBURETOR
JMS
-
8/12/2019 petrol engine Carburation
20/42
JMS
STARTING :-
-
8/12/2019 petrol engine Carburation
21/42
TO GET THE RICH MIXTURE DURING STARTING BI-STARTER DISK USED WHICH IS OPERATED
STARTER LEVER.
BI- STARTER DISC CONSIST OF DIFFERENT SIZES OF HOLE.
AT THE TIME OF STARTING VALVE IS OPEN.
NORMAL WORKING-
IDLING AND LOW LOAD
RICH MIXTURE WILL PROVIDE BY PILOT JET.
AT THE SPEED INCREASES BY OPENING THE THROTTLE, PRESSURE BELOW THE THROTTLE VA
FLOW
JMS
CARTER CARBURETOR
-
8/12/2019 petrol engine Carburation
22/42
CARTER CARBURETOR Carter carburetor is normally used in jeeps.
The gasoline enter the float chamber (1).
Chock valve (2) is always open during normal condition.
Carter carburetor comprises three venture.
Smallest venturis(3) is above the fuel level, two venturis
5,6 are below the fuel level.
LOW SPEED
Suction in the venturi 3, is sufficient to induct the fuel.
Nozzle 4, enters the ventrui 3, & throws the fuel up
against the air stream.
The mixture from venture 3, flows centrally through the
second venture 5, where it is surrounded by air stream& finally goes to the third venture 6,
So well mixed & gives more homogenous & better
mixture at every low speed.
Metering rod 7, which is directly connected to the main
throttle valve.JMS
Idle & low speed circuit
-
8/12/2019 petrol engine Carburation
23/42
p
Rich mixture in small quantity required.
Throttle valve 8, practically closed.
The entire suction pressure created by piston in the
engine suction stroke & is exerted at the idle port 9.
So gasoline is inducted through the idle feed jet 9 & air
is inducted through first by pass 11, and rich mixture is
provided.
Accelerating pump.
Purpose is to avoid flat spot in acceleration.
Pump comprises plunger13, inside cylinder consisting non
return inlet check valve 14, & outlet check valve 15.
The plunger of the pump is connected to the acceleration
pedal by throttle control rod 16.
JMS
On rapidly opening the throttle by pressing the
-
8/12/2019 petrol engine Carburation
24/42
accelerating pedal, the pump is actuated & small
amount of gasoline spurts in to the chock tube by jet 17.
JMS
S.U. CARBURETOR
-
8/12/2019 petrol engine Carburation
25/42
S.U carburetor is constant vacuum carburetor.
In this carburetor venture are vary with the speed which maintain constant pressure.
While other carburetor venture area is constant so P is varies with respect to speed.
A tapered pin is connected to variable chock.
Lower partition of the variable chock is maintain at atmospheric pressure. Upper portion is below atmospheric pressure.
Pe will be varies according to suction pressure which change as per the speed of engine.
JMS
-
8/12/2019 petrol engine Carburation
26/42
JMS
OPERATING DIFFICULTY IN CARBURETOR
-
8/12/2019 petrol engine Carburation
27/42
OPERATING DIFFICULTY IN CARBURETOR
1. ICE FORMATION :-
FUEL SPRAY BY THE MAIN JET IN VENTURY WHERE FUEL ATOMIZE & VAPORIZE.
FOR VAPORIZATION OF THE FUEL IT REQUIRED LATENT HEAT WHICH IS TAKEN FROM INCO
SURROUNDING.
IF TEMP. BECOME LOWER THAN THE DEW POINT OF WATER, WATER VAPOR IN THE INCOM
FREEZE & FORM ICE.
2. VAPOR LOCK :-
FOR BETTER COMBUSTION HIGHER VOLATILE FUEL IS PREFERRED & TO PREVENT ICE FORMA
VAPORIZATION.
VAPORIZATION OF FUEL BETWEEN FUEL TANK & CARBURETOR CREATES THIS PROBLEM.
MAINLY DUE TO HIGHER SPEED, DURING HOT DAYS, HIGH LOAD.
VAPOR IS COMPRESSIBLE & HENCE, THERE IS DIFFICULTY IN PUMPING OF FUEL FROM FULL
STOPS WHICH IS KNOWN AS VAPOR LOCK.
JMS
3. BACK FIRING :-
-
8/12/2019 petrol engine Carburation
28/42
BACK FIRING WILL TAKE PLACE IN INTAKE OR EXHAUST MANIFOLD.
IF THE MIXTURE IS TOO LEAN , THE RATE OF COMBUSTION IS TOO SLOW.
IN THIS CONDITION BACK FIRING IS TAKE PLACE.
4. NON UNIFORM DISTRIBUTION OF A/F MIXTURE IN MULTI CYLINDER ENGINE.
JMS
PETROL INJECTION SYSTEM
-
8/12/2019 petrol engine Carburation
29/42
PETROL INJECTION SYSTEM There are number of drawback & limitation of carburetor in petrol engine & it can b
injection system.
In petrol injection system, metered air is supplied to intake manifold or fuel may be dire
manifold or in cylinder like diesel engine. Quantity of air & fuel continuously changing according to reqirement of an engine at var
Various sensor are placed which gives signal to electric control unit (ECU).
Computer simulates all the data & actuates fuel injector & injection system for best perfo
JMS
TYPES OF PETROL INJECTION SYSTEM
-
8/12/2019 petrol engine Carburation
30/42
TYPES OF PETROL INJECTION SYSTEM
PetrolInje
ctionsyste
m
Indirect injection
Multi point fuelinjection
Port
Thrott
Single pointinjection
Port
ThrottGasoline directinjection
Indirect Injection
-
8/12/2019 petrol engine Carburation
31/42
The Term Indirect Injection, In An Internal Combustion Engine, Refers To Fuel Injection Where
Injected Into The Combustion Chamber.
Gasoline Engines Are Usually Equipped With Indirect Injection Systems,
Wherein A Fuel Injector Delivers The Fuel At Some Point Before The Intake Valve.
An Indirect Injection Diesel Engine Delivers Fuel Into A Chamber Off The Combustion C
Prechamber, Where Combustion Begins And Then Spreads Into The Main Combustion Chambe
JMS
Gasoline Direct Injection
-
8/12/2019 petrol engine Carburation
32/42
In Internal Combustion Engines,
Gasoline Direct Injection (GDI), Also Known As Petrol Direct
Injection Or Direct Petrol Injection Or Spark Ignited Direct
Injection (SIDI) Or Fuel Stratified Injection (FSI).
In This System Petrol Is Directly Injected Inside The Cylinder
At The End Of Compression Stroke. As in diesel injection
system.
JMS
Multi-point Fuel Injection
-
8/12/2019 petrol engine Carburation
33/42
Multi-point Fuel Injection Systems Involve The Use Of Numerous Individual Injectors Fo
Two Basic Arrangements
1. Port Injection
2. Throttle Body Injection
Port Injection
In P.I , The Injector Is Placed On The Side Of The Intake Manifold Near The Intake Por
The Injector Sprays Gasoline Into The Air, Inside The Intake Manifold.
Gasoline Mix With Air Uniform Manner.
Every Cylinder Provided With An Injector In Its Intake Manifold.
JMS
-
8/12/2019 petrol engine Carburation
34/42
JMS
Throttle Body Injection
-
8/12/2019 petrol engine Carburation
35/42
This Throttle Body Is Similar To The Carburetor Throttle Body, With The Throttle Valve
Amount Of Air Entering The Intake Manifold.
An Injector Is Placed Slightly Above The Throttle Throat Of The Throttle Body.
The Injector Sprays Gasoline Into The Air In The Intake Manifold Where The Gasoline
This Mixture Then Passes Through The Throttle Valve & Enters Into The Intake Manifold
JMS
-
8/12/2019 petrol engine Carburation
36/42
JMS
M.P.F.I SYSTEM FOR MODERN AUTOMOBILE
-
8/12/2019 petrol engine Carburation
37/42
MULTIPOINT FUEL INJECTION SYSTEM (MPFI) :- SEPARATE FUEL INJECTOR TO SUPPLY FUEL
SINGLE POINT FUEL INJECTION (SPFI) :- ONLY ONE CENTRALLY LOCATED FUEL INJECTOR
IN BEGINNING IT IS ONLY USED FOR AERO PLANE ENGINES
THIS SYSTEM IS COMBINE ELECTRICAL+ELECTRONICS+COMPUTER+MECHANICAL
DAEWOO MATIZ IS THE FIRST VEHICLE EQUIPPED WITH MPFI SYSTEM IN INDIAN AUTOMO
COMPONENTS
1. ELECTRONIC CONTROL UNIT (ECU) :- IT CONTROLS THE IGNITION TIMING & QUANTITY2. SENSORS :- TO MONITOR AMBIENT, COOLANT & EXHAUST GAS TEMP, INTAKE PRESSURE
3. SOLENOID INJECTOR
JMS
CLASSIFICATION OF MPFI SYSTEM
-
8/12/2019 petrol engine Carburation
38/42
1. D-M.P.F.I
2. L- M.P.F.I
D-M.P.F.I
As the air enters into the intake manifold , the intake
manifold sensor detect the intake manifold vacuum &
send the information to ECU.
The speed sensor also sends information about the RPM
of the engine to ECU.
The ECU in turns sends commands to the injector to
regulate the amount of fuel supply for injection.
JMS
-
8/12/2019 petrol engine Carburation
39/42
INTAKE MAINFOLDVACCUME SENSOR
ENGINE
INJECTOR
ECU
JMS
L-MPFI SYSTEM
-
8/12/2019 petrol engine Carburation
40/42
IN THIS SYSTEM THE FUEL METERING IS REGULATED BY THE ENGINE
SPEED AND THE AMOUNT OF AIR THAT ACTUALLY ENTERS THE
ENGINE.
AIR FLOW SENSOR---ECU
SPEED SENSOR-----ECU
ECU-----SIGNAL TO THE INJECTOR.
JMS
ADVANTAGES & DISADVANTAGES
-
8/12/2019 petrol engine Carburation
41/42
ENGINE REQUIRES DEFERENT A/F RATIO AT DIFFTERNT OPERATING CONDITION. THIS SYSTE
CONDITION.
THERE IS NO VENTURY AS IN CARBURETOR SO THERE IS SMOOTH FLOW OF AIR, HENCE VO
INCREASES.
LESS PROBLEM OF ICING & VAPOR LOCK.
EASY STARTING
IN MULTI CYLINDER SAME A/F RATIO WILL PROVIDE.
IMPROVE BSFC RESULTS
DISADVANTAGES
HIGH INITIAL COST
MAJOR PART ARE ELECTRONICS SO CAN NOT BE REPAIR.
SKILLED WORKER & SPECIAL SERVICE EQUIPMENTJMS
-
8/12/2019 petrol engine Carburation
42/42
THANK YOU
JMS