What is an Engine

A device that converts chemical energy it to mechanical energy

Also converts linear force into mechanical force

Basic Engine Theory

Requires external fuel source (motor does not)

Converts chemical energy to mechanical energy

Only about 40% effecient

Generates a lot of waste heat and sound

Two-Stroke Engine Operation

Simplest design with few moving parts

Highest power/weight ratio

Ineffecient, dirty and noisy

Picture of a basic two stroke cylinder

Four-Stroke Engine Operation

This is the engine design in almost all trucks on the road

Utilizes four stroke of the piston for one complete cycle

The four strokes

The four strokes are:

Intake

Compression

Power

exhaust

Rotating vs. Reciprocating Mass

Crankshaft, flywheel, and lower portion of connecting rod are considered rotating mass

Piston and upper portion of connecting rod are considered reciprocating mass

Cams and valves also rotate and reciprocate

Combustion Chamber

the area inside the engine where the fuel/air mixture is compressed and then ignited

formed on one side by the shape cast into the cylinder head, and on the other side by the top of the piston

Combustion Chamber

THINK

When is the chamber’s dimension is at its smallest

Types of Combustion Chambers

HemisphericalThe "Hemi" Combustion Chamber• Offer the least amount of compromise for

the efficiency gained

• Hemispherical combustion chamber is one half of a sphere cast into the bottom of the cylinder head

Hemispherical design

Hemispherical

chambers

generally have

a central

spark plug

Wedge-Shaped Chambers

resembles an inclined basin recessed into the deck of the head

The relatively steep walls in such chamber design force the air/fuel flow path and deflect and force it to move in a downward spiral around the cylinder axis

Wedge-Shaped Chambers

Diesel fuel

crude oil, is naturally found in the earth

After refining, it can be separated into several different kinds of fuels, including gasoline, jet fuel, kerosene and, of course, diesel

Diesel fuel

Diesel fuel is heavier and oilier than gasoline

evaporates much more slowly

boiling point is actually higher than the boiling point of water

It evaporates more slowly because it is heavier

Diesel fuel

Diesel fuel has a higher energy density than gasoline

3.8 L of diesel fuel contains approximately 155x106 joules (147,000 BTU)

gasoline contains 132x106 joules (125,000 BTU) for 3.8L

Diesel fuel

(C8H18), typical of the molecules found in

gasoline

(C16H34), typical of diesel fuel

C is for carbon and H is for hydrogen

Diesel fuel

In a complete burn, the oxygen in the air combines with the hydrogen to form water (H2O) and with the carbon to form carbon

dioxide (CO2).

If the burning is not complete, some of the carbon atoms only combine with one oxygen atom rather than two, to form carbon monoxide (CO)

Diesel fuel

unburned hydrocarbon molecules can also come out the tailpipe

hydrocarbons react with nitrogen oxides (another pollutant from combustion) in the presence of sunlight to form ozone

Diesel fuel classification

Diesel  fuel  is  graded  and  designated  by  the American Society for Testing and Materials (ASTM

Its specific gravity and high and low heat values are listed by the American Petroleum Institute (API).

Diesel fuel classification

Each oil refiner and supplier attempts to produce diesel fuels that comply as closely as possible with  ASTM  and  API  specifications

Due to different crude oil supplies, the diesel fuel may either be on the high or low end of the prescribed heat scale in Btu per pound or per gallon

Diesel fuel classification

There are only two recommended grades of fuel that is considered acceptable for use in high-speed heavy-duty vehicles. These are the No. 1D or No. 2D

Diesel fuel Grade:1D

Fuels within this classification are applicable for use in high- speed  engines  in  service  involving  frequent  and relatively wide variations in loads and speeds

In cold weather conditions, No. 1D fuel allows the engine to start  easily.

Diesel fuel Grade:1D

Heavy-duty  high-speed diesel  vehicles  operating  in  continued  cold-weather conditions, No. 1D fuel provides better operation than the heavier No. 2D.

Require a minimum cetane number (CN)

above 40

Diesel fuel Grade:2D

Grade No. 2D has a lower volatility

This fuel is used more by truck fleets, due to its greater heat value per /L, particularly in warm to moderate climates

Has higher calorific value

Recommended for use with constant load and speed

Diesel fuel Grade:2D

Like # 1D the 2D CN is required to be above 40

Even though No. 1D fuel has better properties for cold weather operations, many still use No.  2D  in  the  winter,  using  fuel  heater/water  separators to provide suitable starting, as well as fuel additive

Selecting the correct diesel fuel

Seven factors should be considered when selecting fuel to maximize performance and extends engine life. They are:

1. Starting  characteristics

2. Fuel handling

3. Wear on injection equipment

Selecting the correct diesel fuel

4. Wear on pistons

5. Wear on rings, valves, and cylinder liners

6. Engine  maintenance

7. Fuel cost and availability

Cetane Number (CN)

Cetane  number  is  a  measure  of  the  fuel  volatility; the higher the rating, the easier the engine will start and the combustion process will be smoother

The Ideal CN is 100 and a poor CN is 0

Increasing the CN decrease fuel mileage

Cetane Number (CN)

The CN rating is set by the ASTM

Current 1D and 2D diesel fuels have a cetane rating between 40 and 45.

The  higher  the  cetane  rating,  the easier the fuel will ignite once injected into the diesel combustion chamber.

Cetane Number (CN)

If the cetane number is too low, you  will  have  difficulty  in  starting,  

Engine knock and puffs of white smoke during warm-up in cold weather.

Octane rating

Compression is one of the four strokes on a four stroke engine

The amount of compression is called the compression ratio of the engine.

Octane rating

Octane rating

The octane rating of gasoline tells much the fuel can be compressed before it

spontaneously ignites

Spontaneous ignition causes engine knock

Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of

compression before igniting.

Octane rating

The compression ratio of your engine determines the octane rating of the gas

you must use in the car

“High-performance engine" has a higher compression ratio and requires higher-

octane fuel

87 Octane gasoline contains 87-percent octane and 13-percent heptane

Volatility

The tendency of a liquid to Vaporize

Volatility rating for diesel is crucial in summer when its higher fraction tends to boil off lowering the CN

Calorific value

This is the potential heat energy of a fuel

It is measured in BTU, Joules, or calories

Viscosity

Viscosity is the measure of a liquid’s resistance to flow

Viscosity decreases as temperature increases

This means that a fluid with a high viscosity is heavier than a fluid with low viscosity.

Viscosity

High  viscosity  fuel  may  cause  extreme pressures  in  the  injection  systems  and  will  cause reduced atomization and vaporization of the fuel spray

The viscosity of diesel fuel must be low enough to flow freely at its lowest operational temperature, yet high enough to provide lubrication to the moving parts of the finely machined injectors

Viscosity measurement

Recommended  fuel  oil  viscosity  for  high-speed diesel engines is generally in the region of 39 SSU (Seconds  Saybolt  Universal)  

This is  derived  from using a Saybolt Viscosimeter to measure the time it takes for a quantity of fuel to flow through a restricted hole in a tube

Cloud point

This is the temperature at which fuel begins to precipitate as wax crystal. When these crystals become large enough, the fuel will appears cloudy. This is the actual cloud point

Fire point

This is the temperature at which a fuel evaporates enough flammable vapor burn continuously in the presence of air

•   Images

Flame propagation

This represents the way in which a fuel combusts inside the engine cylinder

This is determine by: the flame front, cylinder gas dynamics, AFR, temperature and fuel density

Pour point

This Generally depicts the lowest temperature at which a fuel can be pumped

Pour point is usually 3deg.C (5deg.F) to 15deg.C ( 25 deg.F) below cloud point

Specific gravity

The specific gravity of a fuel is the the weight of a volume of the fuel compared to the weight of the same volume of water.

The S.G. of petroleum base fuel is a direct measure of its heat value

Sulfur content

This is simply the amount of sulfur present in the fuelSulfur is present in most crude petroleum fuel but is more prominent in the heavier fuels such as diesel.The problem with sulfur is that when combusted, the sulfur in the fuel oxidized and form sulfur dioxide

Sulfur content

The sulfur dioxide reacts with water to form sulfuric acid

Diesel fuel as been legislated to be ultra low sulfur(ULS) fuel

Ultra low sulfur (ULS)fuel

Ultra low sulfur fuel

Ultra low sulphur diesel fuel has been refined so that its sulphur content is 15 parts per million (ppm) or less

This is 97 percent cleaner than the standard highway-use diesel fuel sold in the US, which contains an average of 500 ppm of sulphur

Ultra low sulfur fuel

The move toward ULSD is aimed at lowering diesel engines' harmful exhaust emissions and improving air quality

ULSD fuel will work with a new generation of diesel engines and exhaust system as well

Ultra low sulfur fuel

ULSD will enable the new generation of diesel vehicles to meet the same strict emission standards as gasoline-powered vehicles

The new engines will utilize an emissions-reducing device called a particulate filter

Diesel fuel subsystem

Diesel fuel subsystem

NOTE:

Diesel fuel system are usually designed to pump more fuel than is required

This value can exceed 60%

The excess fuel is used to: COOL and LUBRICATE

Fuel Tank

Fuel tanks can be made from aluminium alloy, fibreglass or steel.Most on-road mobile diesel tanks are of aluminium alloy because of its lighter weight and less susceptible to corrosion Tanks must be strategically installed for vehicle balancingFuel tanks are OEM responsibility

Fuel Tank

Fuel tanks also contains Baffles to prevent the fuel from sloshing around when the vehicle is moving

Fuel Tank Recommendations

Need to be located in the air flowMost tanks are cradle mounted to the side of the frame rails to ensure thisGood air flow means good heat exchange from the fuel to the atmosphere When fuel temperatures climb above 95°F, there can be a noticeable loss of power because fuel density drops.

Fuel Tank Recommendations

The best shape is CYLINDRICAL because it

Maximize The surface area of the exposed area of the tank( Quest. Why is this important)

Stronger base on the law of physics (question: Tell me why)

Fuel Tank Recommendations

Fuel should be kept at minimum of 25 % full (Quest. Why)A galvanized steel fuel tank should never be used for fuel storage because diesel fuel reacts chemically with the zinc coating to form powdery flakes that clogs fuel filters and damage fuel pumps and injectors

Dual Fuel Tanks

Usually two tanks mounted on opposite sides of the frame railBoth tanks of equal size and shape to maintain even weight distributionFuel is fed to the engine from both tanksFuel is return to both tanksNote a single pick up tube can be used with a cross over pipe.(old technology)

Pick up tube

Usually positioned slightly above the base of the tank to avoid picking up water or dirt

When or if failed, it can cause the fuel to be aerated

Fuel Tank Ventilation

As fuel is sucked out of the tanks air is drawn in

As fuel is returned to the tanks the air is forced out

This air movement prevent the tank from in a vacuum or from been under pressure.

Fuel Tank Ventilation

At this time diesel tanks are equipped with vents that allow free movement of air into and out of the tank to atmosphere.

Water in fuel

Water in Fuel (WIF) should be periodically checked base on the OEM recommendation

Water in the tank can be checked By: inserting an aluminum rod slightly coated with water detection paste in the fuel tank

Remove rod and inspect for a change in color

Fuel sending unit

This sending unit is mounted in side the tank

It consist of a floating and a arm connected to a variable resistor

The resistor controls the current to the cab gauge proportionally with the fuel level.

Filter Clean Fuel

Fuel filters are rated by their ability to trap particles

They function like a strainer allowing only particle of a certain size to pass through

The unit we use to measure particle is micron.

1 micron = 1 millionth of a meter

Filter Clean Fuel

A typical secondary filter filters down to 5 micron

So any solid 5 micron or bigger will be trapped

NOTE

A human eye is unable to see particles smaller than 40 micron in size

Filter Clean Fuel

Example: a fuel filter with a rating of 2micron at 99% means it will trapped particle 2micron or larger 99%of the time

Fuel Lines

Fuel lines bring the fuel from the tank to the engine and return surplus fuel from the engine to the tank. Tubing, hoses, and fittings have to meet temperature, pressure, chemical, and physical requirements for each part of an installation.

Fuel Lines

Fuel lines may be under relatively low pressure or no pressure such as is the case in return lines bringing fuel back to the tank Supply lines from the tank to the transfer pump are under suction

Fuel Lines

Fuel Lines

Lines from the transfer pump to the injection equipment are under moderate pressure usually ranging from approximately 3 to 75psi depending on the system although some new systems operate at higher pressures, up to 265 psi.

Fuel Lines

Copper tubing is not recommended for any fuel system. This tubing hardens and breaks in a relatively short time in diesel installations Some steel tubing is copper-coated to prevent excessive corrosion and to add resiliency. Copper-coated tubing must not be mistaken for copper tubing.

High pressure fuel line

Pump line nozzle system such as the inline pump system use high pressure fuel lines These are usually made of heavy-wall steel tubing and must be capable of handling fuel pressures as high as 24,000 psi

High pressure fuel line

Pump line nozzle is between the injection pump and the injectors.

Fuel line inspection

Inspect the fuel lines periodically for loose connections, breaks, or other flaws Fuel lines must be replaced if they are worn, damaged, or deteriorated

Fuel Subsystem Operating Fundamentals

There are several different types of high pressure injection equipment

Inline pump

The inline pump consisting of an individual pump element for each cylinder all contained in a single housing,

Distributor pump

Distributor style pumps which use a single pump element for all cylinders which was common on smaller engines

Unit injection systems

MUI, (mechanical unit injector), EUI, (electronically controlled unit injector), HEUI, (hydraulically actuated electronically controlled unit injector)

Unit injection systems

Unit injection systems

The EUI and HEUI are the most common system todayEUI and HEUI systems have individual unit injectors for each cylinder They are called unit injectors because they are responsible for pressurizing metering and atomizing the fuel

Electronic Unit Pump(EUP)

EUP, (Electronic Unit Pump), these systems have individual pumps for each cylinder

The pumps are driven off the engine camshaft

Common rail fuel system

Common rail injection systems use an accumulator rail that retains fuel at injection pressures and delivers it to the injectors There are other proprietary systems in use such as Cummins PT, (Pressure Time), system, Cummins HPI-TP, (High Pressure Injection - Time Pressure), Cummins Accumulator Pump Systems.

Low Pressure Supply System

designed to provide an unrestricted supply of fuel to the transfer pump and the fuel injection pump

Transfer Pump

Transfer pumps must be capable of providing maximum fuel flow at idle speeds

At high speeds the pumps provide much more flow than is required so the pump must have a regulating system of one kind or another in order to limit its maximum pressure

Transfer Pump

Fuel transfer pump can be Driven by

The cam shaft

Gear driven by an accessory

Electric pump controlled by the ECM

Mechanically Operated Diaphragm Transfer Pump

Consists of an actuator arm; a lever-operated, spring-loaded diaphragm; an inlet valve; and an outlet valve The engine's camshaft has an eccentric that applies power to the pump's actuator arm.

Mechanically Operated Diaphragm Transfer Pump

As the diaphragm is pulled down, a low pressure area is created above it This causes the higher atmospheric pressure in the tank to push fuel past the inlet valve into the centre chamber of the pump

Mechanically Operated Diaphragm Transfer Pump

As the diaphragm is forced back up by the spring, the pressure above the diaphragm increases This pressure closes the inlet valve and opens the outlet valve, forcing fuel to travel through the pump outlet and into the injector pump.This pump pressure max. at about 7PSI

Mechanically Operated Diaphragm Transfer Pump

Plunger Transfer Pump

This transfer pump is a higher pressure pump Usually mounted on the injection pump housing The injection pump camshaft actuates the pump's plunger There are two types of plunger pumps single and dual acting.

Plunger Transfer Pump

Gear Transfer Pump

The gear transfer pump is a positive-displacement pump generally driven directly from the end of the governor shaft. A built-in regulating valve prevents damage to the injection equipment in the event of an obstruction in the fuel supply system

Gear Transfer Pump

The fuel pump body is recessed to provide running space for the pump gearsRecesses are also provided at the inlet and outlet cavities An overflow valve returns excess fuel to the supply tank

Gear Transfer Pump

When the discharge pressure is great enough to move the relief valve back from its seat, fuel re-enters the suction side of the pump controlling the maximum pressure

Gear Transfer Pump