Fuel InjectorsFuel Injectors

MAE 442MAE 442Mitch Rieck, Arie van Eyk and Mitch Rieck, Arie van Eyk and

Brandon KaufmanBrandon Kaufman12/9/200912/9/2009

OutlineOutline BackgroundBackground

• HistoryHistory• Comparison to CarburetionComparison to Carburetion• TypesTypes

Direct InjectionDirect Injection Indirect InjectionIndirect Injection ApplicationsApplications CalculationsCalculations

• FormulasFormulas• GraphsGraphs• ModificationsModifications

High PerformanceHigh Performance Fuel EfficiencyFuel Efficiency DurabilityDurability

ConclusionsConclusions ReferencesReferences

BackgroundBackground

All internal combustion engines All internal combustion engines require a device to mix the fuel and require a device to mix the fuel and air before being ignited by the spark air before being ignited by the spark plugplug

The two types we will look at are The two types we will look at are Mechanical DirectMechanical Direct and and Mechanical Mechanical IndirectIndirect injectors injectors

HistoryHistory

Fuel injectors have been around since Fuel injectors have been around since the 1950’sthe 1950’s

Herbert Akroyd Stuart developed the developed the first fuel injection system for a first fuel injection system for a gasoline engine. gasoline engine.

Robert Bosch improved Herbert’s and improved Herbert’s and adapted it for use in the diesel adapted it for use in the diesel engine.engine.

CarburetionCarburetion

Carburetion was replaced by the fuel Carburetion was replaced by the fuel injector. injector.

The last Carburetor that was installed The last Carburetor that was installed in an American automobile was in in an American automobile was in 1990 1990

Uses a simple throttle plate to Uses a simple throttle plate to control the volume of air flow control the volume of air flow through the pipethrough the pipe

TypesTypes

After the carburetor there are two main types of fuel injection, direct and indirect. The main difference between direct and indirect injection is the layout of the injection system, the indirect injection system actually has a small swirl chamber above the cylinder, where the fuel is injected, this chamber also contains the spark plug, which is needed to start the engine, the direct injection system has the injection nozzle actually fixed to the top of the combustion chamber, usually the piston on the engine with this type of injection system has a crown shape in the top to create the needed air/fuel mixture.

Indirect InjectionIndirect Injection

Indirect injection is used on most automobiles today. Before the fuel enters the piston cylinder it mixes with the air in a separate chamber. When the correct pressure is reached it is released into the piston cylinder for combustion.

Open view diagramOpen view diagram

Indirect Fuel Injector

Exploded view diagramExploded view diagram

Needle Valve

Multiport injector

Compression Bushing

Valve Spring

Injector Housing

Nose Cover

Direct InjectionDirect Injection

In a direct-injection system, the air and gasoline are not pre-mixed. Air comes in through the intake manifold, while the gasoline is injected directly into the cylinder. The piston head is curved to create a swirl at high pressures in order to ensure a balanced air-fuel mixture.

Open view diagramOpen view diagramDirect Fuel Injector

Photograph courtesy of Mitch Rieck

Spray Tip

Fuel Passageway Valve Spring

Air Intake

Advantages/DisadvantagesAdvantages/Disadvantages

Indirect Injection

Advantages:•High rate of swirl over wide range of engine speeds•Does not require expensive, ultra high pressure injection system•Less chance of injector blockage due to self cleaning pintle injectors

Disadvantages:•Poorer fuel consumption due to lower thermal efficiency•Higher compression ratio required to aid starting

Direct Injection

Advantages:•Cold starting is easier•More Economical•Smaller combustion space, better thermal

efficiency

Disadvantages:•Tend to be noisy•More prone to blockages due to small injector holes•Lower power output•Slower swirling, particularly at low engine speeds

ComparisonComparison Cadillac CTS: Two versions (same 3.6L V6) one direct and one Cadillac CTS: Two versions (same 3.6L V6) one direct and one

indirect. indirect. Indirect produces 263 horsepower and 253 lb-ft torqueIndirect produces 263 horsepower and 253 lb-ft torque Direct produces 304 hp and 274 lb-ft torqueDirect produces 304 hp and 274 lb-ft torque Despite the additional power, EPA fuel economy estimates for the Despite the additional power, EPA fuel economy estimates for the

direct injection engine are 1 MPG higher in the city (18 MPG vs 17 direct injection engine are 1 MPG higher in the city (18 MPG vs 17 MPG) and equal on the highwayMPG) and equal on the highway

Sidenote: Cadillac's direct injection engine runs on regular (87 octane) gasoline. Sidenote: Cadillac's direct injection engine runs on regular (87 octane) gasoline. Competing cars from Infiniti and Lexus, which use 300 hp V6 engines with indirect Competing cars from Infiniti and Lexus, which use 300 hp V6 engines with indirect injection, require premium fuel.injection, require premium fuel.

http://www.cadillac.com/pages/open/cts.do

ApplicationsApplications

Direct InjectionDirect Injection• Compression ignition (diesel)Compression ignition (diesel)• Two stroke (exhaust port can be allowed to close before Two stroke (exhaust port can be allowed to close before

the mixture is injected, greatly reducing exhaust the mixture is injected, greatly reducing exhaust emissions. )emissions. )

Indirect InjectionIndirect Injection• Spark IgnitionSpark Ignition• Wide range of four stroke enginesWide range of four stroke engines

CalculationsCalculations

Calculations will focus around the power output Calculations will focus around the power output which will be calculated using the relationship which will be calculated using the relationship between horsepower and fuel mass flow rate.between horsepower and fuel mass flow rate.

Trends showing the effects of each variable on Trends showing the effects of each variable on the fuel flow rate will be shown in graphical form.the fuel flow rate will be shown in graphical form.

FormulaeFormulae

During injection, the mass flow rate During injection, the mass flow rate of fuel through an injector is:of fuel through an injector is:

The total power output is then The total power output is then calculated using:calculated using:

Formulae (cont.)Formulae (cont.)

GraphsGraphs

Three different fuels were used, each having a Three different fuels were used, each having a different Heating Value and density:different Heating Value and density:

Gasoline – 43,000 kJ/kg, 702.5 kg/m^3Gasoline – 43,000 kJ/kg, 702.5 kg/m^3

Light Diesel – 42,500 kJ/kg, 815 kg/m^3Light Diesel – 42,500 kJ/kg, 815 kg/m^3

Ethanol – 26,950 kJ/kg, 789 kg/m^3Ethanol – 26,950 kJ/kg, 789 kg/m^3 The following values are common:The following values are common:

Discharge Coefficient – 0.7-1.0Discharge Coefficient – 0.7-1.0

Nozzle Flow Area - 0.2-1.0 mm Nozzle Flow Area - 0.2-1.0 mm

Pressure Differential – 20-200 MpaPressure Differential – 20-200 Mpa

GraphsGraphs

GraphsGraphs

GraphsGraphs

AnalysisAnalysis

The graphs tell us the higher the rate of fuel The graphs tell us the higher the rate of fuel consumption the more horsepower we are consumption the more horsepower we are producing.producing.

One can increase the discharge coefficient by One can increase the discharge coefficient by increasing the number of valves, but it is very increasing the number of valves, but it is very difficult to achieve a coefficient of 1.0. Power difficult to achieve a coefficient of 1.0. Power increased by ~2,000hp for the gasoline engine increased by ~2,000hp for the gasoline engine for a coefficient of 0.7 and 1.0.for a coefficient of 0.7 and 1.0.

Analysis (cont.)Analysis (cont.)

By increasing the nozzle area, more fuel is By increasing the nozzle area, more fuel is entering the chamber and creating more entering the chamber and creating more combustion. This increased horsepower from combustion. This increased horsepower from 4,000hp to 11,000hp in the gasoline engine.4,000hp to 11,000hp in the gasoline engine.

It is observed that changing the pressure It is observed that changing the pressure differential by 180 Mpa, we increased the power differential by 180 Mpa, we increased the power by ~7,500hp.by ~7,500hp.

Modifications – High PerformanceModifications – High Performance

Modifications were based on the calculations Modifications were based on the calculations shown in the graphs.shown in the graphs.

Horsepower increases linearly with increasing Horsepower increases linearly with increasing Discharge Coefficient.Discharge Coefficient.

Horsepower increases linearly with increasing Horsepower increases linearly with increasing Nozzle Flow Area.Nozzle Flow Area.

Horsepower increases logarithmically with Horsepower increases logarithmically with increasing Pressure Differential.increasing Pressure Differential.

Modifications – Fuel EfficiencyModifications – Fuel Efficiency

Even though power is increased, by increasing Even though power is increased, by increasing the fuel flow rate, one would be using more gas.the fuel flow rate, one would be using more gas.

So, it is best to maximize performance and lower So, it is best to maximize performance and lower fuel consumption through fuel efficiency.fuel consumption through fuel efficiency.

Engine sensors, catalytic converters, and Engine sensors, catalytic converters, and performance chips are all used to increase fuel performance chips are all used to increase fuel efficiency.efficiency.

Modifications - DurabilityModifications - Durability

The biggest obstacle in durability is clogging of The biggest obstacle in durability is clogging of the fuel injectors.the fuel injectors.

It is recommended to replace fuel injectors every It is recommended to replace fuel injectors every 25,000 miles.25,000 miles.

One can also use a fuel injector cleaner or One can also use a fuel injector cleaner or cleaning kit to reduce clogs.cleaning kit to reduce clogs.

ConclusionsConclusions

Injection is superior to carburetionInjection is superior to carburetion Indirect injection is easier and therefore more Indirect injection is easier and therefore more

common to implementcommon to implement Direct injection is more efficientDirect injection is more efficient Increasing the pressure differential across a fuel Increasing the pressure differential across a fuel

injector is the most effective way to improve injector is the most effective way to improve performanceperformance

Increasing the nozzle area is the easiestIncreasing the nozzle area is the easiest

ReferencesReferenceshttp://www.howcarswork.co.uk/modules/articles/article.php?id=7

http://auto.howstuffworks.com/question3771.htm

http://en.wikipedia.org/wiki/Fuel_injection

http://www.chathamfuel.on.ca/http://www.chathamfuel.on.ca/

http://ezinearticles.com/?Fuel-Injectors:-Time-To-Replace?&id=63453

Pulkrabek, Willard W. Prentice Hall 2004. 2Pulkrabek, Willard W. Prentice Hall 2004. 2ndnd Edition. “Engineering Edition. “Engineering Fundamentals of the Internal Combustion Engine”. pp. 199-240Fundamentals of the Internal Combustion Engine”. pp. 199-240