ja304

CHAPTER 5

CYLINDER BLOCK AND CYLINDER HEAD

BY

MOHD SAHRIL MOHD FOUZI

MECHANICAL ENGINEERING DEPARTMENT

UNGKU OMAR POLYTECHNIC

CLO 2 (Sketch the diagram of processes involved in spark ignition and compression ignition.)(P4)

[JA304] INTERNAL COMBUSTION ENGINE

MSF


CYLINDER BLOCK & CYLINDER HEAD

MSF

General objective:

To understand the application and structure of the cylinder block and head.

Specific objectives:

At the end of this unit you should be able to:

1. explain the application of the cylinder block.

2. explain the material selected to provide cylinder block.

3. explain two types of sleeve

3.1 Wet sleeve

3.2 Dry sleeve

4. explain the advantages and disadvantages of sleeve.

5. discuss the design of a cylinder head.



MSF

Introduction

A cylinder block and cylinder head are the main supporting structures to which

all other engine parts are attached to

Cylinder Block

The cylinder block is the main component of an engine.

It houses, supports, and positions other parts for precise operation.

Engineers have developed many types of cylinder blocks, such as the L- head (side valve), V twin, and twin-opposed types, to fit equipment

requirements.

The blocks of the engines are generally made of aluminium but may have a steel cylinder liner (sleeve).

Cast-iron engines fill the need for heavy-duty commercial works.



MSF

FIGURE 5.1: CYLINDER BLOCK CONSTRUCTION

Figure 5.1 shown a cylinder block four cylinder engine. Cylinder blocks can be

categorized into two categories: replaceable cylinder liners and fixed cylinder

liners. Engines with replaceable cylinder liners are usually called sleeved

engines



MSF

Cylinder Block Material Selection

A cylinder block is made by casting process due to its complex feature.

Once the cylinder block is cast , and after it has been cooled and cured, surfaces are machined so other parts can be attached to the block. These

surfaces include the cylinders, top of block (deck),camshaft bore, crankshaft

bore, and oil pan surfaces.

The front and rear of the block mounts are also machined so that the parts can be attached and sealed correctly.

Materials that are used to make a cylinder block are: i. Cast Iron/steel

ii. Aluminum ( for smaller engine)



MSF

Differences between Aluminum and Cast Iron

In theory, cylinder block which contains iron heads do not conduct as much heat away from the cylinder as aluminum does, so the iron heads should be

made more powerful.

With the increased concern for improving gasoline mileage, however, car manufactures are trying to make the vehicle lighter. Besides that, aluminum

weighs less and is generally much easier to repair.

One way to reduce the weight in the block, aluminum is used for this purpose. Iron is less expensive but weighs more. Silicon is also added to the aluminum.

Through a special process, the silicon is concentrated on the cylinder walls. This design is called silicon-impregnated cylinder wall.

Cylinder Sleeves



MSF

Some manufacturers use cylinder sleeves. Rather than casting the cylinder bores directly into the block, they insert a machined sleeve (Figure 5.2).

FIGURE 5.2: TYPES OF CYLINDER SLEEVES

Sleeves are inserted after the block has been machined. The purpose of using a sleeve is that, if the cylinder is damaged, the sleeve can be removed and

replaced rather easily.

Blocks which already have sleeves have to be bored out to remove any damage. After boring, larger piston will be needed.



MSF

The dry sleeve is pressed into a hole in the block. It can be machined quite thinly because the sleeve is supported from the top to the bottom by the

cast iron block.

The wet sleeve is also pressed into the block. The cooling water touches the center part of the sleeve. This is why it is called wet sleeve.

Seal must be used on the top and at the bottom of the wet sleeve. Seals are used to keep the cooling water from leaking out of the cooling system. Wet

sleeves are used on some larger diesel engines.

Advantages of a sleeved engine: i. easily reconditioned in frame

ii. engine manufacturers are able to produce cylinder liners from special

wear-resistant and heat-treated alloys



MSF

Cylinder Head

The cylinder head closes one end of the cylinder and encloses the combustion chamber, which is cast into cylinder head.

The cylinder head includes the valve guides, valve seats, ports, combustion chamber, water jackets, threaded holes for spark plug, other threaded hole for

attaching parts, and several machined surfaces.

The spark plug is threaded into the cylinder head with the spark plug electrodes protruding into the combustion chamber for each cylinder or

piston.

The cylinder head also has fins to release the heat of combustion into passing air flow.



MSF

FIGURE 5.3: STRUCTURE OF CYLINDER HEAD

Cylinder Head Materials

Cylinder head can be made from cast iron or aluminum.

Aluminum is used to make the engine lighter, but it transfers heat more rapidly and expands more than cast iron with the addition of heat.

The cylinder head must have an intake and exhaust port.

After the cylinder head has been cast, it must be machined. Areas must be machined so that intake and exhaust manifolds can be attached, valves can

be seated, sparks plugs and injectors can be installed, and a good seal can

be provided to the block.



MSF

Intake and exhaust ports must be cast into the cylinder head. These ports are made so the air and fuel can pass through the cylinder head into the

combustion chamber.

FIGURE 8.4: CYLINDER HEAD CONSTRUCTION

Combustion Chamber

The shape of the Combustion Chamber affects the operating efficiency of the engine.

Two types of combustion chamber designs are commonly used and they are the Wedge- Shaped Combustion Chamber and The Hemispherical

Combustion Chamber.



MSF

WedgeShape Combustion Chamber

FIGURE 5. 5: WEDGE SHAPED COMBUSTION CHAMBER

As the piston comes up on the compression stroke, the air and fuel mixture are squashed in the quench area. The quench area causes the air and fuel to be

mixed thoroughly before combustion chamber.

This helps to improve the combustion efficiency of the engine. Spark plugs are positioned to get the greatest advantage for combustion.

When the spark occurs, smooth and rapid burning moves from the spark plug outward. The Wedge Shaped Combustion Chamber is also

called a Turbulence-Type Combustion Chamber.



MSF

Hemispherical Combustion Chamber

FIGURE 5.6 : HEMISPHERICAL COMBUSTION CHAMBER

The Hemispherical Combustion Chamber is also called the Hemi-Head.

The Hemispherical Combustion Chamber is considered a No turbulence-Type Combustion Chamber. The air and fuel mixture is compressed evenly on the

compression stroke.

The spark plug is located directly in the center of valve. The advantages of the Hemispherical Combustion Chamber are that air and fuel can enter the chamber

very easily.

Swirl Chamber



MSF

FIGURE 5. 7: SWIRL CHAMBER

The Swirl Chamber is designed to provide better mixing of the air and fuel particles to improve combustion.

This results in better fuel economy and lower exhaust emissions since fewer unburned hydrocarbons enter the exhaust system.

The swirl effect is achieved by intake port design, port location in the combustion chamber, and the shapes of the chamber itself.



MSF

This design factor results in a corkscrew type of flow of the air-fuel mixture in the cylinder as the piston move up and down on the intake stroke.

As the piston come up on the compression stroke this agitation of the air-fuel mixture continues and is compounded by compression

Multivalve Design



MSF

FIGURE 5.9: CVCC (CONTROLLED VORTEX COMBUSTION CHAMBER)

The multivalve design is used in across-flow arrangement with intake valve on one side and exhaust valve on the other side (Figure 5.9).

There are two camshafts, one for intake valves and one for exhaust valves. This result in more complex camshaft mounting and camshaft drive

requirements.



MSF

The advantages of the multivalve chamber include greater volumetric efficiency resulting from the increased flow rate, central spark plug location for

better combustion, reduced emissions, better performance, and increase fuel

economy.


SELF-ASSESSMENT

MSF

List down two types of cylinder blocks in single-cylinder air-cooled engine

blocks that are cast.

QUESTION 1

What are the materials used to make cylinder block?

QUESTION 2

Name two categories of a cylinder block

QUESTION 3

List two types of Cylinder Sleeve:

QUESTION 4

What is the main function of a cylinder head at the engine?

QUESTION 5

Based on the figure below, label the parts of CVCC Combustion Chamber


SELF-ASSESSMENT

MSF

QUESTION 6

List down three types of Combustion Chamber found in Internal combustion

engine.

QUESTION 7

Explain the purpose of Combustion Chamber in the internal engine


SELF-ASSESSMENT

MSF

QUESTION 8

What are the materials needed to make a cylinder head?

QUESTION 9

ja304

Documents

cylinder engine

types of cylinder blocks

replaceable cylinder

fixed cylinder liners

block deck

block mounts

steel cylinder liner

compression ignition