Four stroke Diesel Engine-Alfred Franklin

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Session – 1 Working Principle of 4-Stroke diesel Engine Alfred Franklin V Mobile Number: 9965370082 Course: B.E/B.Tech (First Year) Subject: Basic Civil and Mechanical Engineering. University: Anna University Tirunelveli.

description

The four stroke diesel engine working principle is explained

Transcript of Four stroke Diesel Engine-Alfred Franklin

Page 1: Four stroke Diesel Engine-Alfred Franklin

Session – 1

Working Principle of 4-Stroke diesel Engine

Alfred Franklin VMobile Number: 9965370082

Course: B.E/B.Tech (First Year)Subject: Basic Civil and Mechanical Engineering.University: Anna University Tirunelveli.

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Session Objectives

At the end of this session, the learner will be able to:

Define engine.Classify EngineDifferentiate between Diesel engine and Petrol engine.Describe the Working principle of diesel engine.List out Applications of four stroke diesel engine.

Teaching Learning Material

Black Board and ChalkPPTAnimation

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Session Plan

Time(in min) Content

Learning Aid and

Methodology

Faculty Approach

Typical Student Activity

Skill andCompetency Developed

5 Recap : Engine Question and Answer Facilitates Participates

Remembering/Knowledge Intrapersonal

5 I.C Engine Classification PPT Explains Listens

Remembering/KnowledgeUnderstanding/Comprehension

15I.C Engine Components & their functions

PPT Explains Listens

Remembering/KnowledgeUnderstanding/Comprehension

15 Working Principle of CI engine PPT/Animation Explains Listens

Remembering/KnowledgeUnderstanding/Comprehension

5 Applications Quiz Facilitates Participates

Remembering/KnowledgeUnderstanding/ComprehensionInterpersonal

5Comparisons between Petrol and Diesel Engine

Choose and Defend Facilitates Participates

Knowledge/ compressionInterpersonal

Session Inputs

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Recap: Engine

The learners are already familiar with diesel engines. The same can be recapped through a question and answer round before introducing the new topic.

Suggested Activity: Question & Answer

The following questions can serve as sample questions for the activity: 1. What is engine?2. How engines are classified?3. What is IC & EC engine?

What is an engine? Heat engines are mechanical device converting heat into

useful mechanical work

Heat is generally generated by chemical reaction, typically from combustion of all sorts of fuels.

The original concept is called fire piston, which uses the high temperature due to a rapid compression of gas to kindle a fire.

How an engine is classified? Internal Combustion Engines. - Combustion takes place inside the cylinder. External Combustion Engines. - Combustion takes place outside the cylinder.

While explaining the IC and EC engines we can show the following pictures.

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IC Engine classification

The students should know the classification of IC engines as a part of curriculum; we have to classify the Internal combustion engines by showing the following pictures.

1. Based on Basic engine design2. Working cycle (SI & CI engine)3. Based on Application.

1. Based on Basic engine design

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2. Working cycle (SI & CI engine)

• 2-stroke: 1 power stroke per 1 crankshaft rev• 4-stroke: 1 power stroke per 2 crankshaft rev

Components of I.C Engine

Before explaining the working principle of 4S diesel engine we have to explain the components and their functions so that the students can understand the working principle easily.

The components are broadly classified into:a) Structural componentsb) Moving components

(a) Structural Components:

1. Engine Block (Multi cylinder Engine)• Part of engine frame that contains cylinders in which piston moves• Supports liners & head

• Part of engine frame that contains cylinders in which piston

moves

• Supports liners & head

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2. Engine Head or Cylinder Head Assembly

• Serves to admit, confine, and release fuel/air

• Cover to cylinder block• Supports valve train

3. Crankcase• Engine frame section that houses the crankshaft.

(b) Moving Components

Three Groups – according to motion Reciprocating only (pistons and valves) Reciprocation & rotary (connecting rods) Rotary only (crankshafts and camshafts)

4. Piston • Acted on by combustion gases• Lightweight but strong/durable

• Piston Rings• Transfer heat from piston to

cylinder• Seal cylinder & distribute lube

oil• Piston Pin

• Pivot point connecting piston to connecting rod

5. Connecting Rod

• Connects piston & crankshaft

• Converts reciprocating into rotary motion.

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6. Crank Shaft

• Combines work done by each piston

• Drives camshafts, generator, pumps, etc

7. Flywheel• Absorbs and releases kinetic energy of

power strokes and converts smoothes rotation of crankshaft.

8. Valves• Intake: open to admit air to cylinder.

• Exhaust: open to allow gases to be rejected

9. Camshaft & Cams• Used to time the addition of intake and

exhaust valves

• Operates valves via pushrods & rocker arms

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Working Principle:

After explaining the components of four stroke diesel engine, the students can understand the working principle easily. The following two figures are used for explaining the working principle.

Terminology• TDC: Top Dead Center, position corresponding to

smallest volume in the cycle• BDC: Bottom Dead Center, position corresponding to

largest volume in the cycle• Stroke: distance between TDC and BDC• Bore: diameter of piston• Displacement volume: volume limited by TDC and BDC

4-strokeCycle CI Engine Principle of Operation

• Cycle of operation is completed in 4-strokes of the piston or 2 revolutions of the crankshaft.

• Each stroke consists of 180°, of crankshaft rotation and hence a cycle consists of 720°of crankshaft rotation.

The series of operations of an ideal four-stroke SI engine are as follows:

Intake/Suction Stroke

During the intake stroke, the intake valve opens as the piston moves down to allow air into the cylinder.

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Stroke Valve Position

Suction StrokeSuction Valve openExhaust Valve closed

Compression Stroke

Both Valves closed

Expansion or Power Stroke

Both Valves closed

Exhaust StrokeExhaust Valve openSuction Valve closed

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The air is pushed by atmospheric pressure into the cylinder through the intake valve.

Compression Stroke

After the piston reaches its lower limit, it begins to move upward and as the piston moves up, the intake valve closes.

The exhaust valve is also closed, so that at this point in the cycle, the cylinder is sealed.

As the piston moves upward, the air is compressed and the compression of the air causes the pressure and the temperature of the cylinder to increase.

Expansion/Power Stroke

As the piston reaches maximum compression of the air, diesel fuel is injected to the combustion chamber filled with compressed air.

The heat of the compressed air ignites the fuel spontaneously at the self-ignition temperature of the fuel.

As the cylinder pressure increases, the piston is forced down into the cylinder.

The power impulse is transmitted down through the piston, through the connecting rod, and to the crankshaft, which is rotated due to the force. 

Exhaust Stroke

As the piston reaches the bottom of its stroke, the exhaust valve opens.

As the piston moves up on the exhaust stroke, it forces the burned gases out of the cylinder through the exhaust valve.

Then as the piston reaches the top of its stroke, the exhaust valve closes, and the intake valve opens.

The cycle repeats again with the intake stroke.

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Applications of Diesel engines

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The applications of diesel engine can be explained by conducting a technical quiz activity.

The applications of diesel engines are listed below with pictures for effective understanding.

Suggested Activity: Quiz

The learners may be asked to suggest the applications of diesel engine by showing some of the pictures. We can list their answer on the board.

1. Marine engine

Marine (Largest engine in the world)

3. AGRICULTURE/FARM

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4. TRANSPORTATION

5. Power plants

Comparisons between Petrol and Diesel Engine

The differences between Petrol and diesel engine can be explained by conducting an activity. The figure gives them some clear idea about petrol and diesel engine.

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Suggested Activity: Choose and Defend

The entire class can be divided into two groups. Each group has to support one of the engines. Each group has to predict the advantages of the engine assigned to them and also disadvantages of the other engines. For each advantage 2 points can be given and for each disadvantage 1 point. We can draw two columns on the board with the following headings: ‘diesel engine’ and ‘petrol engine’. A small space may be provided for noting down the points.

The SI engine offers the following advantages1. Low initial cost.2. Low weight for a given power output3. Smaller size for a given power output4. Easy starting

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5. Less noise6. Less objectionable exhaust gas odor and less smoke

The CI engine offers the following advantages

1. Low specific fuel consumption at both full load and part load conditions.2. Utilizes less expensive fuels.3. Reduced fire hazard4. Long operating life5. Better suited for supercharging6. Better suited for two-stroke cycle operating, as there is no loss of fuel in scavenging7. The great advantage of CI engine is lower fuel consumption which counteracts the disadvantage of higher initial cost, if engine used for long duties.

Disadvantages of diesel engine1. Engine Weight high.2. High initial cost.3. High maintenance cost.

Disadvantages of Petrol engine1. Fuel cost high.2. Highly inflammable fuel.

Summary In this session, we learnt to:

Define engine & IC engine.Classify enginesName all the ComponentsDescribe the working principle

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List the applicationsCompare the Petrol and Diesel engine.

References

Books

Theory & Practice in IC Engines By C F Taylor

Fundamentals of I C Engines-J B Heywood

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Internal Combustion Engines by Ganesan

Internal Combustion Engines by M L Mathur & S P Sharma

Websitewww.images.google.com

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