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Home , Carburetor, Common rail, Fuel injection, Indirect injection, Injection pump, Manifold injection

and injection

• is a system for mixing fuel with air in an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having almost completely replaced carburetors in the late 1980s.

• The was invented by Karl Benz (founder of Mercedes‐Benz) in 1885 and patented in 1886.

• Carburetors were the usual fuel delivery method for almost all gasoline (petrol )‐ fuelled engines up until the late 1980s, when fuel injection became the preferred method of automotive fuel delivery. In the U.S. market, the last carbureted were the 1990 Custom Cruiser, Wagon, and Justy, and the last carbureted light was the 1994 . Elsewhere, Lada cars used carburetors until 1996. A majority of still use carburetors Internal combustion Engines: due to lower cost and response problems with early injection set ups, but as of 2005, many new models are now being introduced with fuel injection. Carburetor, Fuel injection, timing Carburetors are still found in small engines and in older or specialized automobiles, such as those designed for stock racing.

Dr. Primal Fernando • A fuel injection system is designed and calibrated specifically for the type(s) of [email protected] fuel it will handle. Most fuel injection systems are for gasoline or diesel Ph: (081) 2393608 applications. 1 2

Gas Review November 1913 Well, lets see if we can figure it out…… Used on tractors, boats, and stationary engines, including the Waterloo Boy Gas Review September 1917 and Model D tractors

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Carburetor Theory Carburetor Theory

• It’s all due to Air (or lack thereof) • Close to sea level pressure is 14.7 psi • Venturi –Air has weight –88 lbs in a 12x12x8 ft room – What is it? • “Vacuum” is a pressure less than 14.7 psi • Wind blowing in downtown Chicago –Often measured in inches of mercury – always stronger in the smaller areas between 2 14.7 psi ~ 30 in Hg bldbuildings • As engine runs, strokes create • River currents – always faster in a narrower, shallower place than “vacuum” or lower air pressure in manifold deep, wide pools –Normal ~10 psi (~20 in Hg) • With throttle plate open, carburetor throat exposed to manifold pressure

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1 Carburetor Theory Carburetor Theory • What causes air flow through carburetor? –Intake of creates vacuum Intake valve open, transmits vacuum to throttle plate

– Position of throttle plate determines air flow Closed – no flow – high Open –full flow –low manifold vacuum

–Air (at ~ atmospheric pressure) flows from air cleaner side, through venturi, past throttle plate, through manifold and intake valve, into • Carburetors operate on the • The venturi is a narrowing of the • Model A running at 975 rpm flows about 70 cfm (cubic feet per minute)

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Carburetor Theory Carburetor Theory • As air flows through venturi, pressure decreases in venturi • Important factors – Bernoulli’s Law tells us as Area decreases, velocity –Amount of vacuum created by intake stroke • Less vacuum if increases and – Intake valve guides leak air –As velocity increases, pressure decreases –Exhaust valve leaks air • Air pressure on ffluel in bblowl is always ~atthimospheric – Piston rings lkleak air • As pressure difference between 1) fuel in bowl and – Manifold leaks air 2) at tip of nozzle (located in venturi) increases, fuel – Position of throttle plate • Determines air flow through carburetor flow increases from nozzle – Determines difference in pressure on fuel in bowl and at – Throttle opens, more air flow, greater ΔP, more fuel tip of nozzle in venturi flow » Greater difference –more fuel flow – Throttle closes, less air flow, less ΔP, less fuel flow

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Carburetor types Carburetor Theory Venturi‐type Carburetor Air/Fuel Mixture To Engine Bernoulli Effect: • To further regulate the mixture, two “air regulators” or P+1/2 V2 = Constant butterfly are also added: Throttle Plate Atomized Fuel – These restrict the amount of air flow through the carburetor‐‐either manually or automatically. Fuel Inlet Valve Stem » This action decreases the power and speed and Float the richness of the mixture within the engine. Venturi Bowl Choke Plate

Constant level is – Throttle valves restrict air movement at all speeds and Inlet Air maintained in bowl -as Fuel are generally manually controlled. float moves down, Nozzle valve stem moves down, – Choke valves restrict air movement at start‐up to allowing more fuel into Metering Orifice allow for a richer mixture and can be manually or bowl, float moves up and automatically engaged. closes valve Ref. Obert

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2 The Throttle θ % Bore Open 0 0.0 10 1.5 • The throttle is a round 14 3.0 disc mounted on a 17 4.4 shaft beyond the main 24 8.6 θ 30 13.4 fuel nozzle in the 33 16.1 carburetor. 41 25.0 45 29.3 • It regulates the 60 50.0 amount of air‐fuel 75 75.0 mixture entering the 84 90.0 % Bore open = πb²(1 ‐ cosθ)x100 90 100 “Bore Open” is difference between cylinder. bore size and area of throttle plate b = radius of bore size

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The Choke Natural Draft Carburetor

• The choke is a round disc mounted on a shaft located at the intake end of the carburetor. • This carburetor is used • Since cold fuel is hard to vaporize, the choke is used where there is little during cold engine starts to provide a rich mixture to the space on top of the carburetor in order to get the engine started. engine. The air horizontally into the manifold.

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Updraft Carburetors Down‐draft Carburetors

• This type is placed low • This carburetor operates with lower air velocities and larger on the engine and use passages. This is because a gravity fed‐fuel gravity assists the air‐fuel supply. In other mixture flow to the cylinder. words, the tank is above the carburetor • The downdraft carburetor can provide large volumes of fuel and the fuel falls to it. when needed for high speed and high power output.

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3 Diaphragm Carburetors Mixture Requirements

• This type does not have a float, Engine induction and fuel system must prepare a rather the difference between fuel‐air mixture that satisfies the requirements of atmospheric pressure and the vacuum created in the engine the engine over its entire operating regime. puls at es a fleiexibl e diaphr agm. Optimum air‐fuel ratio for an SI engine is that which • The pulsation of the diaphragm gives takes place on every intake and compression stroke. 1. required power output 2. with lowest fuel consumption 3. consistent with smooth and reliable operation

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Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio

Energy balance for a steady flow system  2   2         out   in  Q W   m out  hout   gZ ot    m in  hin   gZ in   2   2   2   2             in   out  Q in Win   m in  hin   gZin   Q out Wout   m out  hout   gZ ot   2   2    2    2       out   in  q  w  hout   gZot   hin   gZin   2   2   2   2        Q  Q  W W  m  h  out  gZ   m  h  in  gZ  in out out in   out  out ot    in  in in  Applying the steady flow energy equation to  2   2      sections A‐A and B‐B per unit mass flow of air:

 2   2  2 2           out in 2 1     q  w  h2   gZ2   h1   gZ1  General form Q W   m out  hout   gZ ot    m in  hin   gZin          2 2  2   2      Here, q and w are the heat and work transfers from the entrance to the Note: In the above equation, heat input to the system and work output from throat and h and v stand for enthalpy and velocity respectively. the system is positive (+) and heat output from the system and work input If we assume reversible adiabatic conditions, and there is no work to the system is negative (‐). transfer, q=0, w=0, and if approach velocity v1≈0 we get

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4 Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio

 2   2  v2  2c p T1  T2  0  h2  h1     2   k  1   p  k v  2 h  h T  T  T 1   2   2  1 2  1 2 1      p1    If air is assumed tobe a perfect gas we get k 1 h c T hence we can write    p  p  k v  2c T 1   2   2 p 1     v2  2cp T1  T2  p1    Assume flow from inlet to throat to be isentropic k  1 By the we can write down the theoretical mass T  p  k flow rate of air then 2   2  . T  p  1  1  ma  1 A1v1  2 A2v2  k  1   p  k where A and A are the cross‐sectional areas at the air inlet (point 1) T  T  T 1   2   1 2 1 2 1     and venturi throat (point 2).  p1   

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Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio

k 1 k 1      p  k  p  k v  2c T 1   2   v  2c T 1   2   2 p 1     2 p 1      p1   p1      (velocity) . . ma   A v   A v ma  1 A1v1  2 A2v2 1 1 1 2 2 2 1  p  k To calculate the mass flow rate of air at the throat, we have assumed the  2  2  1  flow to be isentropic till the throat so the equation relating p and v (or  p1  ρ) can be used. 1 1  k 1  . k k k k p1 p2 k  p   p    p2  2  2  p1v1  p2v2 k k   ma  1  A2 2cpT1 1      2  1        1 2 p  p1   p1   1    (specific volume)

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Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio 1  k 1   2 k  1  . k k .   k   k  p2    p2   A2 p1  p2 p2  ma     A 2c T 1    m  2c      1  2 p 1     a p  p   p    p1   p1  R T1  1   1     

p1 Since the fluid flowing in the intake is air, we can put in the For a perfect 1  approximate values of R = 287 J/kgK, cp = 1005 J/kgK and k = 1.4 at 300K. gas we have RT1 1.43 1.71 1 k 1 .   A2 p1  p2   p2  . k k ma  0.1562       p2  p1   p2       m    A 2c T 1    T1  p1   p1  a  p  RT 2 p 1   p    1  1   1     1.43 1.71 rearranging the above equation we have A p  p2   p2   0.1562 2 1  where        2 k 1  p1   p1    T1 . A p  p  k  p  k m  2 1 2c  2    2   a p      R T1  p1   p1   

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5 Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio 1.43 1.71 1.43 1.71 . A p  p   p   p2   p2  2 1 2 2        1.43 1.71 ma  0.1562          .     p p A2 p1  p2   p2  T1  p1   p1   1   1  ma  0.1562Cd ,a         T1  p1   p1  A p  0.1562 2 1  The coefficient of discharge and area are both constant for a given T1 venturi, thus Here, pressure p is in N/m2,areaA is in m2,and temperature T is in K. . If we take the ambient temperature T1 = 300Kand ambient pressure p1 5 2 ma   p1 =10 N/m ,then . T1 ma  901.8A2 Above equation gives the theoretical mass flow rate of air. The actual Since we have to determine the air‐fuel ratio, we now calculate the mass flow rate, can be obtained by multiplying the equation by the . fuel flow rate. coefficient of discharge for the venturi, Cd,a. ma Cd ,a  . ma 31 32

. p Calculation of Air‐fuel Ratio 1 . p Calculation of Air‐fuel Ratio ma   1 Fuel flow will take place because of ma   T1 the drop in pressure at point 1 due T1 The fuel is a liquid before mixing with the air, it can be taken to be to the venturi effect. incompressible. 2 2 P1 V1 P2 V2   gz1    gz2 We can apply Bernoulli’s equation 1 2 2 2 between the atmospheric P P V 2 conditions prevailing at the top of 1 2 2    gz2 the fuel surface in the float bowl, 1 2 2 which corresponds to point 1 and the point where the fuel will flow 2 P1 P2 V f out, at the venturi, which    gz (2)  f  f 2 corresponds to point 2. (1) 3 Fuel flow will take place because of the drop in pressure at point 1 where ρf is the density of the fuel in kg/m , Vf is the velocity of the fuel due to the venturi effect. at the exit of the fuel nozzle (fuel jet), and z is the depth of the jet exit below the level of fuel in the float bowl. This quantity must always be 2 2 2 P V P1 V1 P2 V2 above zero otherwise fuel will flow out of the jet at all times. The value   gz  C (Constant) or   gz1    gz2  2 1 2 2 2 of z is usually of the order of 10 mm.

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Calculation of Air‐fuel Ratio p p V 2 Calculation of Air‐fuel Ratio 1  2  f  gz  f  f 2 2 where Af is the exit area of the fuel jet in m .IfCd,f is the From above equation we can obtain an expression for the fuel velocity at coefficient of discharge of the fuel nozzle (jet) given by

the jet exit as . m .   C  f m  C A 2 p  p   gz p1  p2 d , f . f d , f f f 1 2 f V f  2  gz mf   f  .   A2 p1 . ma  0.1562Cd ,a  Applying the continuity equation for the fuel, we can obtain the Air A m   a T1 theoretical mass flow rate, Since Fuel F . m f 1.43 1.71 .  p   p     2    2  mf   f Af Vf      p1   p1  A C A p   0.1562 d ,a 2 1 F Cd , f Af 2 f T1p1  p2   f gz  Af 2 f p1  p2   f gz

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6 Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio .  2 k 1  . m  C A 2 p  p   gz . C A p  p  k  p  k f d , f f f 1 2 f d ,a 2 1  2 2  m  C A 2 p  p   gz ma  2c p      f d , f f f 1 2 f  p   p    2 k 1  . R T1  1   1  . k k   1 p1  p2   p2  m  C A 2c       c p  cv  R a d ,a 2 R p  p   p   p  R 1  1   1  c R 1 1R 1 1   v 1    1  RT p T c c 1 p1 T1 1 1  2 k 1  p p . c  p  k  p  k  p  2   2   1 R ma  Cd ,a A2 1 p1 2  1  2 k 1 R  p   p      1   1  k c .  R p  p  k  p  k   p m  C A 1 1 2c  2    2   a d ,a 2 p      c p1 R  p1   p1  p k    2 k 1   . 2k  p  k  p  k R k 1 m  C A  p  2    2    2 k 1  a d ,a 2 1 1 k 1  p   p   .  p  p  k  p  k  1   1   m  C A 1 1 2c  2    2     a d ,a 2 p      R  p1   p1   

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Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio . m f  Cd , f Af 2 f p1  p2   f gz  2 k 1  k k 2k  p2   p2   Cd,a A2 1 p1      2 k 1 .        k 1  p1   p1  . 2k  p  k  p  k m   m  C A  p  2    2   a  a d ,a 2 1 1      k 1  p1   p1  m f C A 2 p  p   gz   d , f f f 1 2 f

1 . 2 k 1 2 k 1     m  C  A    2 p k  p  k  p  k 2k  p  k  p  k a  d ,a  2  1  1  2 2   2 2        Cd,a A2 1 p1      m  C  A    k 1  p p  .      f  d , f  f  f  p1  p2   f gz  1   1  k 1  p1   p1    m     a  m f C A 2 p  p   gz d , f f f 1 2 f pa If we put and  p1 pa  p1  p2 p 1  2 p1

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Calculation of Air‐fuel Ratio Calculation of Air‐fuel Ratio p a  p p  p  p 1 a 1 2 p2  2 k 1  1  k  p  k  p  k p  2 2  1 1      . k 1  p   p    C    2 p  1   1   1 ma d ,a A2 1 a   .  2 k 1       2 k k     m  C  A    p k  p   p  m f Cd , f Af  f p   gz p a   d ,a  2  1  1  2    2       a f 1  2 m  C  A    k 1  p   p   p f  d , f  f  f  p1  p2   f gz  1   1  1   A C A  p  d ,a 2 a a   2 k 1  F C A  p   gz k  p  k  p  k d , f f f a f  2    2   1     . k 1  p p  1 2  1   1      2 k 1 2 ma Cd ,a A2 1 pa           p  k  p  k m  C  A      2    2   f  d , f  f  f  pa   f gz p2       1   k   p1   p1  p      1  k 1  p    1   2        p1   

41 42

7 Calculation of Air‐fuel Ratio Air‐fuel ratio neglecting compressibility of air

5 2 if we take T1 = 300K and p1 =10 N/m then • If we assume air to be incompressible, then we can apply Bernoulli’s equation to air flow also. Since initial velocity is A Cd ,a A   901.8 2 assumed zero, we have F Cd , f Af 2 f p1  p2   f gz Thus The coefficient of discharge represents the effect of all deviations from 2 the ideal one‐dimensional isentropic flow. It is influenced by many p1 p2 v2 factors of which the most important are:   1.Fluid mass flow rate, a a 2 2.Orifice length‐to‐diameter ratio, 3.Orifice area‐to‐approach area ratio, 4.Orifice surface area, Thus  p1  p2  5.Orifice surface roughness, v2  2  6.Orifice inlet and exit chamfers,  a  7.Fluid specific gravity, 8.Fluid viscosity, and 9.Fluid surface tension. 43 44

Applying the continuity equation for the fuel, we can obtain the theoretical mass flow rate,

A Cd ,a A2 a p1  p2 .  ma  a A2C2  A2 2a p1  p2 F Cd , f Af  f p1  p2   f gz

2 where A2 is the venturi in m .IfCd,a is the coefficient of discharge of the venturi given by . A Cd ,a A2 a p1  p2 m  a F C A  p  p   gz Cd ,a  . d , f f f 1 2 f ma . . If we assume z = 0, then then ma  Cd ,a A2 2a p1  p2 A C A  .  d ,a 2 a Air A m   a F Cd , f Af  f Since Fuel F . m f 45 46

 A  The effects of equivalence ratio   1 F C A    gz  2 variations  s d , f f f f   1   The equivalence ratio, (ratio between stoichiometric air  Cd ,a A2 a  pa  fuel ratio to actual air fuel ratio) • Mixture requirement at full load: Complete utilization of air to Typical value for a obtain maximum power, wide operation of throttle, rich‐of‐ gasoline engine A C A  p  d ,a 2 a a  stoichiometric mixtures, 1.1.  A    F Cd , f Af  f pa   f gz  F s 14.6    1 • Mixture requirement at part loads: Part throttle, dilute air A A  2 k 1  2  p  k  p  k mixture wihith excess air or exhdhausted gas recycldled (EGR) F F   2    2         (improves the fuel conversion efficiency).  k   p1   p1        k 1  p    1   2        A   p1  • The equivalent ratio of the mixture delivered by an elementary   1   2 carburetor is not constant.  F s Cd , f Af  f   f gz    1    Cd ,a A2 a  pa 

47 48

8 Calculation of Air‐fuel Ratio  2 k 1  k k k  p2   p2   1      . k 1  p   p   2  1   1  m  Cd ,a  A    pa   a    2  1      m f Cd , f Af  f p   gz p     a f 1  2 p1 A C A  p  d ,a 2 a a  F Cd , f Af  f pa   f gz

1  2 k 1  2  p k  p  k    2    2          k   p1   p1        k 1  p    1  2        p1   

49 50

Carburetor Performance The deficiencies of a elementary carburetor 1. At low loads the mixture becomes leaner; the engine requires the • Figure shows the performance of an elementary mixture to be enriched at low loads. carburetor. The top graph shows the variation of Cd,a and 2. At intermediate loads, the mixture equivalence ratio increases Cd,f and Φ with the venturi pressure drop (typically vary slightly as the air flow increases. The engine requires an almost with pressure drop). For Δpa ≤ ρfgz, there is no fuel flow. constant equivalence ratio. Once fuel starts to flow, the fuel flow rate increases more 3. As the air flow approaches the maximum wide open‐throttle rapidly than the air flow rate. The carbbturetor ddlielivers a value, the equivalence ratio remains essentially constant. mixture of increasing equivalence ratio as the flow rate However, the mixture equivalence ratio should increase to 1.1 or increases. z is typically order of 10 mm. Usually fuel level greater to provide maximum engine power. in the float chamber is held below the fuel discharge 4. The elementary carburetor cannot compensate for transient nozzle to prevent the fuel spillage when the engine is inclined to horizontal. phenomena in the intake manifold. Nor can enrich the mixture during engine starting and warm‐up. 5. The elementary carburetor can not adjust to changes in ambient air density (due primarily to changes in altitude).

51 52

Modern Carburetor Design Two common methods used to achieve above are The changes required in the elementary carburetor so that it provides the equivalence ratio required at various air flow rates are as follows. 1. The main metering system must be compensated to provide a constant lean or stoichiometric mixture over 20 to 80% of the air flow range. • Boost venturis 2. An idle system must be added to meter the fuel flow at idle and light loads to provide a rich mixture. Double venturi system, multiple venturis. 3. An enrichment system must be provided so that the engine can get a rich mixture as conditions is approached and maximum power can be obtained. 4. An accelerator must be provided so that additional fuel can be introduced into the engine only when the throttle is suddenly opened. 5. A choke must be added to enrich the mixture during cold starting and • Multiple barrel carburetors warm‐up to ensure that a combustible mixture is provided to each Two barrel carburetors usually consists of two single barrel cylinder at the time of ignition. carburetors mounted in parallel. 6. Altitude compensation is necessary to adjust the fuel flow which makes the mixture rich when air density is lowered. 7. Increase in the magnitude of the pressure drop available for controlling the fuel flow is provided by introducing boost venturis (Venturis in series) or Multiple‐barrel carburetors (Venturis in parallel).

53 54

9 Fuel injection systems Merits of Fuel Injection in the SI Engine • Gasoline fuel injection – Inject the fuel into the engine intake system • Absence of Venturi –No Restriction in Air Flow/Higher Vol. Eff./Torque/Power – Required one per cylinder – There are both mechanical and electronic injector systems • Hot Spots for Preheating cold air eliminated/Denser air enters – Increased power and torque, uniform fuel distribution, rapid engine • Manifold Branch Pipes Not concerned with Mixture Preparation response to throttle position, precise control of equivalence ratio‐‐‐‐‐ (MPI) • injection • Better Acceleration Response (MPI) – Fuel sprayed in cylinder near TDC • Fuel Atomization Generally Improved – Atomization, vaporization & mixing delay ignition • Use of Greater Valve Overlap – Ignition occurs wherever conditions right • Use of Sensors to Monitor Operating Parameters/Gives Accurate Matching of Air/fuel Requirements: Improves Power, Reduces – Combustion rate controlled by injection characteristics (injection rate, fuel consumption and Emissions spray angle, injection pressure, nozzle size and shape), chamber • Precise in Metering Fuel in Ports shape, mixture motion, & turbulence • Precise Fuel Distribution Between Cylinders (MPI) – Glow plug may be used to aid cold starting – Power output controlled only by amount of fuel injected

55 56

Limitations of Petrol Injection Gasoline Fuel Injection System Components • High Initial Cost/High Replacement Cost • Increased Care and Attention/More Servicing Problems 1. Electric • Requires Special Servicing Equipment to Diagnose Faults and Failures 2. Fuel Accumulator – Maintains Fuel Line Pressure When Engine is • Special Knowledge of Mechanical and Electrical Systems Needed to Shut Off and Quietness the Noise Created by the Roller Cell Pump Diagnose and Rectify Faults 3. ‐ A Pleated Paper or Lint‐of‐fluff Type Plus Strainer • Injection Equipment Complicated, Delicate to Handle and Impossible to 4. Primary Pressure Regulator – Maintains Output Delivery Pressure to Service by Roadside Service Units be About 5 Bar • Contain More Mechanical and Electrical Components Which May Go 5 Push Up Valve – Prevents Control Pressure Circuit Leakage. Wrong It is a Non‐return Valve Placed at Opposite End of Pressure Regulator • Increased Hydraulic and Mechanical Noise Due to Pumping and 6. Fuel Injection Valve – Valves are Insulated in Holders to Prevent Fuel Metering of Fuel Vapor Bubbles Forming in the Fuel Lines Due to Engine Heat. • Very Careful Filtration Needed Due to Fine Tolerances of Metering and Valves Open at about 3.3 Bar and Spray Fuel. Discharging Components Valve Oscillates About 1500 cycles per second and so Helps in • More Electrical/Mechanical Power Needed to Drive Fuel Pump and/or Atomization Injection Devices • More Fuel Pumping/Injection Equipment and Pipe Plumbing Required‐ May be Awkwardly Placed and Bulky 57 58

Gasoline Fuel Injection

• In SI engines the air and • Also Called or Single Point Injection (SPI) or fuel are usually mixed Throttle Body Injection (TBI) together in the intake • Injector Usually Upstream From Throttle (Air Intake Side) or In system prior to entry to Some Cases Placed on the Opposite Side the engine cylinder. • are Low –2 to 6 Bar. Maybe Injected Irrespective of • Ratio of air to fuel ≈ 15 : 1 Intake Process • Fuel is injected to trough • Cost Would be Low individual from a • Has Same Air and Fuel Mixing and Distribution Problems as low‐pressure fuel supply Carburetor but Without Venturi Restriction so Gives Higher system into the intake Engine port. • Higher Injection Pressures Compared to Carburetion – Speeds up Atomization of Liquid Fuel

59 60

10 Semi‐direct Injection Direct Cylinder Injection • Also Called Direct Multi‐point Injection (DMPI) or Gasoline Direct • Also Called Port Injection or Indirect Multipoint Injection (IMPI) or Injection (GDI) Simply Multi‐point Injection (MPI) • Injection May be During Intake or Compression Process • Injectors Positioned in Each Induction Manifold Branch Just in Front of Inlet Port • Increased Turbulence Required • Injection at Low Pressure (2‐6 Bar) • To Compensate For Shorter Permitted Time For Injection/Atomization/Mixing Injection Pressure Must Be Higher • Need Not Be Synchronized With Engine Induction Cycle • More Valve Overlap Possible So Fresh Air Can Be Utilized For • Fuel Can Be Discharged Simultaneously to Each Induction Pipe Where Scavenging it is Mixed and Stored Until IVO • Injector Nozzle Must Be Designed For Higher Pressure and • Need Not Be Timed –Requires Low Discharge Pressures –Injectors Not Temperature So Must Be More Robust and Will Be Costlier Than Exposed to Combustion Products so Complexity Reduced –Less Cost Other Types • No Fuel Distribution Difficulties Since Each Injector Discharges Directly • Position and Direction of Injection Are Important –No One Position Into Its Own Port and Mixture Moves a Short Distance Before Entering Will Be Ideal For All Operating Conditions Cylinder • Air and Fuel Mixing Is More Thorough in Large Cylinders Than In • Induction Manifold Deals Mainly With Only Inducted Air – So Branch Small Cylinders Because Droplet Size is the Same Pipes Can Be Enlarged and Extended to Maximize Ram Effect • Condensation and Wall Wetting in Intake Manifold Eliminated But Condensation On Piston Crown and Cylinder Walls

61 62

Gasoline Fuel Injection‐Injector types Fuel Injection (electronic, multi‐port)

• Mechanical injection using an injection Monitored Engine pump driven by the engine. Operating Conditions: TRIGGER COMPUTER Manifold Pressure Engine Speed Air Temperature • Mechanical, driveless, continuous Coolant Temperature injection. Acceleration INJECTOR DRIVE UNIT

• Electronically controlled driveless Pressure Regulator Fuel Fuel injection. 50 psi typical Filter Pump

Injectors

FUEL TANK

63 64

ELECTRONIC FUEL INJECTION The Fuel Injector

• Strict emission standards require precise fuel delivery • Electromechanical device • Computers used to calculate fuel needs • Engine rpm determines when injector opens • EFI very precise, reliable & cost effective • How long it stays open determined by: – • EFI provide correct A/F ratio for all loads, speeds, & temp Engine temp ranges – Engine load – Throttle pos. – O2 sensor voltage

65 66

11 Throttle Body Injection (TBI) LOW PRESSURE FUEL INJECTOR • First injection unit used • Housing • 13‐16 psi similar to Carb operating pressure • One or two • BllBall style injector pintle • One or two of • Easily replaceable these units FIG 6-40 CLASS mounted to intake manifold

67 68

Fuel Pressure Regulator Multi‐Port Fuel Injection • Located at end of fuel rail • One injector per cylinder • Maintains constant pressure at injectors • Mounts in intake • Internal chamber contains a diaphragm manifold, sprays directly – Pressurized fuel on one side at intake valve – Manifold vacuum & spring tension on other • Fired in groups or • Manifold vacuum pulls up on diaphragm, individually (SFI) metering fuel that is returned to tank • Ram Tuning for denser air charge • Excess fuel pressure can overcome spring tension, allowing fuel to return to tank • Lower A/F temps • Increases in manifold pressure causes spring • Leaner mixture during tension to push diaphragm down, blocking warm‐up return line, increasing pressure in rail.

69 70

Fuel Pressure Regulator Fuel Pressure Regulator Vacuum hose connection Fuel rail

Fuel return

71 72

12 (CI) Diesel fuel‐injection system consists of

1. • The liquid fuel jet atomizes into drops and entrains air; evaporates‐fuel vapor mixes with air‐air temperature and 2. Delivery pipes pressure are above the fuel’s ignition point. After a short delay auto ignition starts. 3. Fuel injector nozzles • At full load air fuel ratio is ≈ 20: 1

73 74

THE DIESEL FUEL SYSTEM Fuel Injection Systems

• Injection Pump usually mechanical drive –Belts and rollers not good, use gears and chains • Note spill line from injector, pump, separator

75 76

General Characteristics A pump ain’t so simple!

• Pump runs at ½ engine speed • How does timing vary with load? – –Controls Quantity AND Ignition delay is SHORTER (higher density) BUT: timing of injection –Although ignition delay is shorted, –Max fuel limited by smoke still need more advance to ensure all limit fuel is burnt during stroke –Timing varies with load and • At max load fuel variance among speed cylinders should be less than 3% –Timing accurate to 1o otherwise power limited by smoky exhaust of richest cyl. angle

77 78

13 In‐Line (most common)‐ Layout of conventional fuel system a set of driven plungers (one for each cylinder)

• Driven from crank ½ speed • Multi‐lobe cam • This example uses rack, not lever • Rack rotates plunger assy and controls flow • and advance coupling driven by rotating weights acting against a spring (like mechanical advance on ) • Fuel trapped in the plunger is forced through a check valve into the injection line. The injection nozzle has one or more holes through which the fuel is sprayed to cylinder.

79 80

Plunger Design – Traditional Injection Pump Plungers

• Operation: –Plunger moves up and blocks inlet –Fuel is allowed to escape through spill port (notice helical grove) –Reminder of fuel forced out outlet port –Stroke is constant by delivery varied by rotation

• Plunger forces fuel through fitting • Rotating Lever controls how much spills back – lever controls fuel flow (no throttle) • All run by cam driven by crank

81 82

Rotary Pump Typical Rotary Pump

• Much less complicated but lower pressures • Few moving parts • Fed by transfer pump • Metering through governor mechanism – rotor slides • Pressurization via sliding

83 84

14 Fuel Injectors Timing sets

• Nozzle type dictates performance • Single Hole –Good for ID –1mm hard to clog • Multi hole –Better misting –Easy clog as size ‐> 0.1mm • Clogs caused by decomp of leaked fuel • Differential pressures cause opening • Note needle design – pressure OPENS nozzle • Differential pressures –f(needle diameter vs. diameter) Gear sets –Spring closing –Harder to open than to keep open • Cam and crank rotate in opposite directions • Smaller seat contact area and strong spring • Noisy if not free of burrs enhance sealing, eliminate dribble • Dribble leads to emissions and deposits • Helical and spur cut gears

85 86

Timing sets Pintle Nozzle

• Excellent disbursement, provides conical spray pattern • Looks Similar to that used in CIS systems • Opens UPWARD • ElltExcellent clog resitistance

Timing chains • Single and double roller • Tensioners

87 88

More Injector Considerations Pilot Injection • Aux hole to bleed excess fuel and prevent deposits • 4V Heads: • Small Amount of fuel early to initiate flame front –Upside • Allows for large advance •Vf Up • Eliminates knock and corresponding problems associated with high peak • Central injector position pressures and wave impingement – Downside • 2 Spring Special injector needed for 2 mode operation • Less swirl • More nozzle holes for gg/,ood disbursion/combustion, as small as 0.1 mm • Nozzles cooled by fuel –Cooling important to maintain tolerances and sealing • Spray Pattern Critical! –Aspect Ratio of 2‐8 –Larger Aspect Ratio –more penetration –Larger Aspect ratio – Smaller cone –Atomization up –w‐ velocity, but restricts penetration as well

89 90

15 Electronic Unit Injection Moving Components

• Valves • Electronic Unit Injection – Intake: open to admit air to –Solenoid Controlled cylinder (with fuel in ) –So fast pilot injection can be used – Exhaust: open to allow gases to be –Expensive to produce rejected –Widely used in heavy truck • & where emissions and economy are – Used to time the addition of intake critical and exhaust valves –Controlled just like SI EFI – Operates valves via pushrods & rocker arms • Variation is HEUI

91 92

Valve trains Valve trains

OHV (overhead valve) Pushrod configuration OHC (overhead cam) Many reciprocating parts Fewer reciprocating parts Higher valve spring pressure required Reduced valve spring pressure required Compact engine size compared to OHC Higher RPM capability assemblies are taller 93 94

Valve trains Valve Locations

Cam-in-head No pushrods Use rocker arms

95 96

16 Charge Stratification Combustion process: stratified charge

jet guided wall guided inlet air guided

97 98

Combustion Chamber Designs Design

99 100

Combustion Chamber Design Combustion Chamber Design

101 102

17 Combustion Chamber Design Combustion Chamber Design

103 104

Combustion Chamber Design CLASSIFICATION OF INTERNAL COMBUSTION ENGINES

Cooling

1. Direct Air‐cooling

2. Indirect Air‐cooling (Liquid Cooling)

3. Low Heat Rejection (Semi‐adiabatic) engine.

105 106

Cooling system operation Cooling system operation

Engine heat is transfered . . . Fans increase air flow through radiator • through walls of the combustion chambers • Hydraulic clutches • through the walls of cylinders • Hydraulic fans consume 6 to 8 HP Coolant flows . . . • Electric fans • tdithto upper radiator hose • through radiator Coolant () • to water pump • 50/50 mixture increases boiling point to 227°F • through engine water jackets • pressurizing system to 15 PSI increases to 265°F • through Coolant (propylene glycol) • back to radiator • Less protection at the same temperatures • Less toxic

107 108

18 CI vs. SI Engines • SI engines draw fuel and air into the cylinder. • Fuel must be injected into the cylinder at the desired time of combustion in CI engines. • Air intake is throttled to the SI engine ‐‐ no throttling in CI engines. • Compression ratios must be high enough to cause auto‐ignition in CI engines (CI:12 to 24), compressed to pressure about 4 Mpa Diesel: Gasoline’s Dirty Cousin? and tttemperature abbtout 800 K. • Upper in SI engines is limited by the auto‐ ignition temperature (SI: 8 to 12). • Flame front in SI engines smooth and controlled. • CI combustion is rapid and uncontrolled at the beginning. • The in both CI and SI are similar.

109 110

Misconceptions About Diesel How is Diesel Different from Gasoline? • Diesel is a petroleum‐based fuel with a higher energy content than gasoline. – contains about 30% more energy per gallon as compared to • It’s Dirty gasoline. • Diesel is a safer fuel than gasoline or other alternatives. – less flammable and explosive than gasoline due to lower • It Causes a lot of Pollution combustibility. • Diesel is Cheaper than Gasoline • It has Limited Uses – Current Cost of a Gallon of Gasoline and Diesel • Gasoline = $1.78 • Diesel = $1.65

111 112

Problems with “Old” Diesel Benefits of Diesel Technologies

• A well maintained diesel engine usually emits lower levels of • High Sulfur Content of Fuel monoxide, hydrocarbons and carbon dioxide than • High NOx Emissions gasoline engines. • High Particulate Matter Emissions • Better fuel economy, – The “Black Smoke” everyone sees • Increased durability for longer engine life. • Noisy Engines

113 114

19 Sulfur Content NOx Emissions

• Diesel fuel available in the U.S. currently contains from 340 ppm • High cylinder pressure and temperature with excessive air is the

of sulfur to 140 ppm in California. recipe for making NOx • European Standards are much lower • Because of excess air in diesel engines, current catalytic can’t – As low as 10 ppm in Germany and Sweden scrub out NOx

115 116

Particulate Matter Clean Diesel

• Unburned fuel in the compression ignition process becomes • Clean diesel is an evolutionary systems‐based process that , a pervasive form of particulate matter. combines advancements in diesel engines, cleaner burning and emissions control system, all working and optimized together.

117 118

What Makes Diesel Clean? Cleaner Burning Fuels

• The Three Pillars of Clean Diesel Technology: • The newest in diesel fuels is called Ultra‐low – cleaner‐burning fuels Sulfur Diesel (ULSD) – state‐of‐the‐art engines – Ultra‐low sulfur diesel fuel is a specially refined diesel – effective emissions‐control systems fuel that has dramatically lower sulfur content than regular diesel and can be used in any diesel engine just like regular diesel fuel. • Today, the sulfur content of ULSD ranges from 15 to 30 parts per million. Regular diesel has a maximum of 500 parts per million of sulfur.

119 120

20 How Does ULSD Help? State of the Art Engines

• Reduces sulfate emissions • New Engine Technologies • Allows the use of particulate traps and catalytic converters – Electronic Controls • Lowers engine maintenance costs – Common‐rail Fuel Injection • Easy to convert to – Variable Injection Timing – No retrofitting required – Improved Combustion Chamber Configuration • Only costs a few cents more – Turbocharging

121 122

Comparison of SI and CI Engines Typical Brake Thermal Efficiencies of CI and SI Engines

123 124

125 126

21 (port fuel injection)

Roger Krieger, GM R&D Center 127 128

Summary Diesel Engines

Advantages: • Efficiency (most efficient prime mover)

• Emissions (low CO, CO2, good durability) • Very high torque and performance

Disad vant ages: • Emissions (more challenging to control NOx, ) • Higher cost • Heavier • Noise (more challenging to make quiet)

Roger Krieger, GM R&D Center Roger Krieger, GM R&D Center 129 130

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