DIESEL ENGINE - COMMANRAIL SYSTEM

ENGINE MANAGEMENT SYSTEM DIESEL

Differences between diesel and gasoline engines  

Major Differences between Diesel and Gasoline Engines Being as Compression Ignition (CI) engines only draw in air, they are able to compress this to a level which is considerably higher than that in the spark ignition engine (SI) using an air fuel mixture.  With its overall efficiency figure, the diesel engine rates as the most efficient combustion engine. The resulting low fuel consumption, coupled with the low level of pollutants in the exhaust gas and the considerably reduced level of noise, all serve to underline the diesel engine's significance.

Development Steps of Diesel Engine Control Systems

Higher and higher demands are being made on the diesel engine's injection system as a result of the increasingly severe regulations governing exhaust and noise emissions and the need for lower fuel consumption. Looking at the engine control system in the beginning, the control was made by mechanical means, such as the distributor pump. With this systems it was very difficult to acquire optimal engine efficiency with simultaneously satisfying emission control regulations. The next  development stage was the Electronically Controlled Distributor Pump (COVEC-F) from Zexel. The latest generation of diesel injection system is the Common Rail Direct Injection (CRDI) which  nowadays consist of  various sensors detecting the operating conditions of the engine. Actuators  are used to influence the operating conditions accordingly, both  processed by an electronic device, the control unit. The control unit is processing the data acquired by the sensors in order to determine the best operating conditions and then drives the actuators accordingly. Lets start with the basic engine operation to understand the control requirements precisely.


Basics about combustion

As mentioned before, the Diesel Engine is a Compression Ignition (CI) engine. The mixture is usually formed inside the combustion chamber. The injectors are installed inside the cylinder head and inject the fuel directly into the combustion chamber, in which it mixes with air. During the first stroke, the downward movement of the piston draws in un-throttled air through the open intake valve. During the second stroke, the so called compression stroke, the air trapped in the cylinder is compressed by the piston (32-55bar) which now is moving upwards. The compression ratio is around 25:1.  In this process, the air heats up to temperatures around 800C°. At the end of the compression stroke the nozzle injects fuel into the heated air. The injection pressure varies between 250 – 1600 bar, depending on engine load condition and injection system used. Following the ignition delay, at the beginning of the third stroke the finally atomized fuel ignites as a result of auto ignition and burns almost completely. The cylinder charge heats up even further and the cylinder pressure increases again. The energy released by the combustion is applied to the piston. The piston is forced downwards and the combustion energy is transformed into mechanical energy. In the fourth stroke, the piston moves up again and drives out the burnt gases through the open exhaust valve. A fresh charge of air is drawn in again and the working cycle is repeated.

Diesel Fuel

Diesel or Diesel fuel is a specific fractional distillate of fuel oil (mostly petroleum) that is used as fuel in a diesel engine.  As a hydrocarbon mixture, it is obtained in the fractional distillation of crude oil between 250 °C and 350 °C at atmospheric pressure. Diesel fuel is considered to be a fuel oil and is about 18% denser than gasoline. Diesel fuel, however, often contains higher quantities of sulfur. In Europe, emission standards have forced oil refineries to reduce the level of sulfur in diesel fuels since they are harmful for the environment. Sulfur prevents the use of catalytic diesel particulate filters to control diesel particulate emissions. However, lowering sulfur also reduces the lubricity of the fuel, meaning that additives must be put into the fuel to help lubricate injection system components. Diesel contains approximately 18% more energy per unit of volume than gasoline, which, along with the greater efficiency of diesel engines, contributes to fuel economy.

Bio-Diesel

Bio-Diesel can be obtained from vegetable oil and animal fats. Bio-Diesel is a non-fossil fuel and consists of alkyl (usually methyl) esters instead of the alkane and aromatic hydrocarbons of petroleum derived diesel.


Influence of mixture composition 

A variety of different combustion deposits are formed when diesel fuel is burnt. These reaction products are dependent upon engine design, injection system design, engine power output and working load. In the first place water (H2O) and harmless carbon dioxide (CO2) are generated. In relatively low concentrations, the following substances are also produced:

• Carbon monoxide (CO)
• Unburned hydrocarbons (HC)
• Nitrogen oxides (NOx)
• Sulfur dioxide (SO2) and sulfuric acid (H2SO4)
• Soot particles

When the engine is cold, the exhaust gas constituents which are immediately noticeable are the non oxidized or only partly oxidized hydrocarbons which are visible in the form of white or blue smoke, and the strongly smelling aldehydes.

Influence of mixture composition

The following contribute to the reduction of fuel consumption and exhaust gas emissions:

•  Fuel atomization (high injection pressures)
•  Injection sequence characteristics
•  Precision manufactured injection nozzles
•  Fuel injection pumps with precise fuel metering
•  Modified combustion chambers
•  Precisely defined fuel spray geometry

Apart from the above mentioned points, optimal injection timing is decisive for reducing exhaust emissions in a diesel engine. The start of combustion is primarily determined by the start of injection. Retarded injections reduces emissions of oxygen and nitrogen. Over retarded injections increases the emission of hydrocarbons. Deviations of the start of injection from the nominal  value by 1° of crankshaft angle can increase the emission of NOx or HC by approximately 15%.

This high sensitivity requires that the  start of injection is precisely set. The most favorable setting for the start of injection can be precisely maintained by an electronic controlled system.

Turbocharger/Intercooler

As the temperature of the intake air increases on engines with turbochargers, there is a rise in the combustion temperature and thus in the emission of oxides of nitrogen. In engines fitted with turbochargers, the cooling of the compressed air is an effective way of reducing the formation of oxides of nitrogen. Another way for reducing NOx is to use Exhaust Gas Recirculation (EGR).

Subsections of the diesel injection system



 On a diesel fuel injection system fuel supply and delivery is divided into low pressure and high pressure delivery. The Diesel Injection system in general consists of the following main sections:

• Fuel Delivery System, including fuel tank, supply lines, fuel filter, pre-supply pump (either electrical type or mechanical type), high pressure pump and high pressure pipe.
• Start Assist System, including glow plugs and glow plug control unit (either separate or located inside the Engine Control Module)
• Air Induction System, including Air Filter and Exhaust Gas Recirculation
• Exhaust System, including Oxidation Catalyst and Particulate Filter (only CRDI)
• Electronic Control System, including Sensors and Actuators (only Electronically Controlled Distributor pump and CRDI)

• Vacuum System
  
  
  
  Fuel filter and water separator
  
  
  
   Contaminants in the fuel can lead to damage at the injection system. This, therefore, necessitates the use of a fuel filter which is specifically aligned to the requirements of the particular injection system, otherwise faultless operation and long service life cannot be guaranteed. Diesel fuel can contain water either in bound form (emulsion) or in free form (for example condensation of water due to temperature changes).  If this water enters the injection system, it can lead to damage as a result of corrosion.
  
  
  Water Separator Warning Lamp
  The increasing number of diesel engines used in passenger cars has led to the demand for an automatic warning device which indicates to the driver when water must be drained out of the fuel filter.
  
  
  Water Drain Procedure
  The Diesel Injection System needs a fuel filter with water reservoir, from which water must be drained at regular intervals or when the water separator warning lamp is illuminated. Open the drain plug to drain the water from the water reservoir. If no water comes out, open the air bleeding plug on top of the filter element. Please refer to the Shop Manual for more detailed information.  

 Fuel Filter replacement

1. Clean the Filter housing
2. Remove the filter element by turning it counter clockwise
3. Clean the filter contact surface
4. Install the new filter element, tighten it by turning it clockwise, refer to the shop manual for detailed information about the tightening torque

Air Bleeding

It is required to bleed the system if any component within the diesel system was replaced. If there is air present within the system, the engine is hard to start or will run roughly.  The air bleeding procedure differs from model to model. Therefore refer to the Shop or Owners Manual for more detailed information.

Pressure Relief Valve

Certain filters (for example Bosch CRDI) incorporate a Pressure Relief valve located on top of the fuel filter assembly. In case of a restriction inside the filter or at the filter outlet side, the pressure relief valve opens, thus allowing the fuel to flow back into the fuel tank.

 

BORE, STROKE AND DISPLACEMENT

The automotive cylinder is a machined-smooth circular hole in a cast iron engine block. A fpw engine blocks are made of aluminium but this lightweight material wears quickly. Sometimes a machined steel cylinder sleew is used inside an aluminium block for light weight and long wear. In a liquid- cooled engine the quarter-inch th'ck walls of the cylinder are surrounded by a water jacket. Water mixed with coolant flowing in the jacket carries away the unused heat of combustion. The water jacket extends up over the top of the combustion chamber to handle the heat created there. Instead of a water jacket, an air-cooled engine has cooling fins around the outside of each cylinder. They dissipate engine heat directly to the air.
Operating within the cylinder is a machined aluminium alloy piston. The piston is made slightly smaller than the cylinder to prevent binding between the two. The piston rings in grooves around its upper half. The springy piston rings press outward against the cylinder walls. The bottom ring spreads lubricating oil onto the cylinder wall. The top rings keep lubricant scraped back so that it will not reach the combustion chamber. They also seal off combustion gases to keep the gases from slipping past the piston.

BORE AND STROKE

The inside diameter of the cylinder is called bore. Stroke is the distance the piston travels from bottom dead centre to top dead centre. The size of an engine cylinder is refer to in terms of the bore and stroke. These measurements are used to calculate the lp~ston displacement.

A square engine has bore and stroke of equal measurements. An over square engine has relatively long bore and small stroke. There are several reasons for having smaller stroke:

1 . Less friction loss

2. Reduced inertia and centrifugal loads on the engine bearings.

3. Reduced engine height and lower hood line.

NOTE: In the metric system, bore and stroke are given in millimetres.

There are several reasons for the popularity of the oversquare engine. With the shorter piston stroke, there is less friction loss because the piston does not move as far in the cylinder. Also the shorter stroke reduces inertia and centrifugal loads on the engine bearings. In addition, the shorter stroke permits a reduction of the engine height and thus a lower hood line.

Despite the advantages of the shorter-stroke oversquare engine, recent emphasis on reducing atmospheric pollutants in the exhaust has forced automobile manufacturers to lengthen the stroke. For example, one late-model Ford six-cylinder engine has a stroke of 3.91 inches (99.3 mm) compared with a 3.13 inch (79.5 mm) stroke for earlier years. This longer stroke, in effect, provides more burning time for better combustion.

PISTON DISPLACEMENT

Piston displacement is the volume that the piston displaces, or 'sweeps out', as it moves from BDC to TDC. You can pasture this volume as a cylinder that is the diameter of the engine cylinder, the top and bottom being the piston-head at the TDC and BDC positions. To calculate piston displacement, you use the bore D and the length of stroke L. Thus piston displacement of a 4 by 3 112 inch (101.6 by 88.9 mm) cylinder is the volume of a cylinder 4 inches (101.6 mm) in diameter and 3 1/2 inches (88.9 mm) long.

ENGINE DISPLACEMENT

Displacement indicates the working size of an engine. It is given in cubic inches cubic centimeters, or liters. Cubic- inch displacement is often abbreviated cu. in of CID (cubic inch displacement). Cubic centimeters is abbreviated simply cc. It's a metric unit. The other metric unit liter - is used more in formula racing and advertising to give a colorful racing note to an automobile engine.

To convert CID to cc, multiply by 16.39. Thus a 350 CID engine has a displacement of 5736 cc. A liter contains, for practical purposes, 1000 cc. So a 5 liter engine has a displacement of 5000 cc.

To convert cubic centimeters to cubic inches divide by 16.39. The 5000 cc, 5 liter engine contains about 305 cubic inches displacement. To convert liters to cubic inches, multiply by 61.025. Cubic inch figures are soon to be phased out in favor of the metric ones. Ford is already using both cubic- inch and liter designations on its V-8 and V-6 engines.

Definition engine displacement is defined as the volume displaced by all of the engine's piston during one complete revolution of the crankshaft. This is also referred to as swept volume.

It's easy to calculate engine displacement. Merely multiply the area of one cylinder - that is, its cross-sectional area - times the pistons stroke. If all the figures are in cubic inches. If all the figures put into the calculate are in centimeters, the resulting figure will be in cubic centimeters.


The cross section at a cylinder is simple to calculate because it's a circle. It you know the radius of the circle you can figure the area of the circle quite easily by multiplying the radius squared times pi, which is approximately 3.14. The figure pi is a commonly used constant in circular, spherical and other calculations.


Engine manufactures give cylinder bore specifications, but not cylinder radii. Cylinder bores are diameters. Turning a diameter into a radius is simple. Divide it by two. A 4- inch cylinder bore has a radius of 2 inches.


The displacement formula could be stated simply like this. Displacement = 3.14 x stroke x no. of cyls. You need not remember any of these formulas, however. Just try to understand what they are doing.


For example, if the bore is 4 inches and the stroke is 3.5 inches in an eight-cylinder engine, the displacement would be calculate as follows: 3.14 x 4/2 x 4/2 x 3.5 x 8 = 351.68 cubic inches. Or in other words.

Displacement of an engine is a measurement of its size and is equal to the number of cubic inches the piston displaces as it moves from bottom dead centre to top dead center. In other words, it is equal to the area of the piston, it also necessary to multiply by the number of cylinders.

Displacement = A x L x N

Where A is the area of the piston in square inches, L is the length of stroke in inches and N the number of cylinders. Assuming you have a six cylinder engine with a 4 in. bore and a 4 1/4 in. stroke, the procedure is to first calculate the piston area:


Area = 4 x 4 x 0.7854 = 12.56 sq. in.

Then the displacement equals = 12.56 x 4.25 x 6 = 320.28 cu. in

Thus, Engine displacement = L X N cc

Where D = diameter of cylinder in cm
L = length of stroke in cm
N = No. of cylinder

Manual Gearbox

POWER TRAIN

With the 1st-2nd speed synchronizer on the intermediate shaft, the 3rd-4th and 5th speed, synchronizers on the input shaft, and a constant mesh type, smooth gear changes are obtained. In reverse, the reverse idler gear of spur gear slides and mesh with the gear on the input shaft and the one on the outer periphery of the 1st-2nd speed synchronizer sleeve, simultaneously.

TRANSMISSION

In Automotive, 2 type of transmission:

1) Manual Transmission

2) Automatic Transmission

General

As transmissions designed exclusively for 5-speed, 3rd-4th and 5th speed synchronizers is arranged on the input shaft while a 1st-2nd speed synchronizer is arranged on the intermediate gear.

A simple mechanical shift control mechanism is used in shifting into 5th-speed. As a result, the conventional 5th-speed shift control mechanism which uses a vacuum servo has been eliminated

The number of sets of gear meshing when the transmission is turning in neutral has been reduced from six to two, thereby reducing the noises produced during idling with the shift lever in Neutral.

Through use of a new type of synchronizer piece and a reduction in the inertial moment of the relevant synchronizing parts (through modification of the gear train), the shifting effort has been reduced and the shift feeling has been improved.

Through use of split needle bearings and an increase in the capacity of the shaft support bearings, the reliability and durability have been improved

CYLINDER AND ARRANGEMENT

In-line Engine

Designed as an In-Line style

Advantages
•Easy manufacture
•More cheaper

Disadvantages
• Cannot change aerodynamic

“V’ Configuration Engine

‘V’ type design, angle 60-90º

Slant Cylinder Engine

• Engine Design like In line
• It’s design to reduce distance TDC to BDC
• Slanting type can be design more aerodynamically

Opposed Cylinder Engine

• Used Two Cylinder Head
• The angle between two cylinder was 180º
• Normally it’s used in smaller vehicles


Radial Cylinder Engine

• Cylinder are set in a circles
• Normally this type used for high performance engine.

ENGINE - "Energy Conversion"

Still in Engine Topic....
but detail in "Energy Conversion" first..its a Fundamentals

•Energy is define as the ability to do work
• Power is defined as a measure of the work
being done.
• Energy can take on one of six forms, they
include:
a. Chemical
b. Electrical
c. Radiant
d. Mechanical
e. Nuclear
f. Thermal forms of energy

Example how energy conversion happen :

Internal Combustion Engine,
Change Thermal Energy to Mechanical Energy

External Combustion Engine
•Change Thermal Energy to Mechanical Energy
•Burning process occur outside combustion chamber

Reciprocating Engine, Changing motion upward and downward

CLASSIFICATION OF ENGINE

Engine

Ok in english of Engine..

Engines have different layouts, depending on the vehicle application. Common arrangements include in-line, vee, flat or rotary.

Cylinder blocks:

Cylinder blockThe cylinder block is the largest part of the engine. Its upper section carries the cylinders and pistons. Normally, the lower section forms the crankcase, and supports the crankshaft.
Cylinder block constructionCylinder blocks made of aluminum are lighter than cast-iron blocks of the same size. They usually have cast-iron liners which provide a hard-wearing surface for pistons and piston rings.
Cylinder sleevesA dry sleeve can be cast or pressed into a new block or used to recondition cylinders. A flanged, dry sleeve has a flange to fit a recess in the block. A wet sleeve has an outer surface directly exposed to coolant.
Grey ironGrey iron is a cast iron that contains carbon in the form of graphite, plus silicon, manganese and phosphorus

Cylinder heads:

Cylinder headThe cylinder head bolts onto the top of the cylinder block where it forms the top of the combustion chamber. It carries the valves and, in many cases, the camshafts.
Cylinder head designCylinder head combustion chambers are designed to help improve the swirl or turbulence of the air-fuel mixture, and prevent fuel droplets settling on the surfaces of the combustion chamber or cylinder walls.
Diesel combustion chambersDirect-injection diesels inject into the combustion chamber formed in the top of the piston. For indirect injection, the combustion chamber is a separate chamber formed in the head.
Intake & exhaust passsagesSmaller intake and exhaust passages and ports allow more torque at low engine speeds. At high speeds, smaller passages restrict airflow. Larger passages produce greater power at high engine speeds.
GasketsGaskets form a seal by being compressed between stationary parts where liquid or gas could pass. Gaskets around a rotating part would quickly wear out. Oil seals are used to seal these parts.
TurbulenceTurbulence refers to the swirling motion of a liquid or a gas.

Sistem Dalam Kenderaan

huh..lama tak update...sory yerla br nk berbloging ni ..lupa plak nk update mengupdate ni
Ok back to topic...
Sistem dalam kenderaan?..yerla smua benda yg idup mesti ada sistem..badan manusia pun ada sistem2 yg amat kompleks
dalam kenderaan pun ada sistem2 yg boleh kita ambil tahu serba sikit...
Kenderaan ni ada sistem yg tersendiri utk membuat kan ia boleh dipandu dengan selamat dan selesa...sistem ini dikelaskan kepada tiga bahagian utama:-
1. Sistem Enjin
2. Sistem transmisi
3. Sistem Kerangka (chasis system)

SISTEM ENJIN.
Pada masa kini,sistem ini banyak menerima perubahan2 yg terkini. Dulu Kenderaan yang menggunakan bahanapi petrol sinonimnya kita pasti mengingatkan tentang karburetor... bg yg guna Diesel pula samada yg menggunakan inline atau distributor pump untuk sistem bahanapinya. Sekarang zaman berubah dengan begitu pesat..teknologi yang digunakan utk sistem pengangkutan juga perubah mengikut peredaran zaman yg serba elektronik ini. Begitu juga dengan sistem enjin bagi kenderaan kini..bnyk yang menggunakan sistem kawalan elektronik untuk mengoptimumkan kemampuan sesebuah enjin.
Bagi kenderaan yg menggunakn petrol sebagai bahanapi sistem kawalan elektronik seperti Electronic Fuel Injection (EFI) digunakan untuk penggunaan bahanapi yang ekonomi dan mesra alam. Bagi kenderaan Diesel pula penggunaan Elektronic Governer pada pump diperkenalkan dan kemudian penggunaan Electronic DIesel atau lebih dikenali sebagai Common rail diperkenal kan baru2 ini. Semua sistem ini mengalami evolusi yang berperingkat dimana fungsi aau objektif utamanya ialah untk bagi penggunaan bahanapai yang ekonomi dan mengoptimumkan keupayaan enjin

Automotive Technology

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