Four stroke Diesel Engine-Alfred Franklin
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Transcript of 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.
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
Working principle of 4-stroke Diesel Engine Page 2Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
4-stroke Diesel Engine Page 3Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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.
Working principle of 4-stroke Diesel Engine Page 4Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
4-stroke Diesel Engine Page 5Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
Working principle of 4-stroke Diesel Engine Page 6Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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.
4-stroke Diesel Engine Page 7Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
Working principle of 4-stroke Diesel Engine Page 8Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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.
4-stroke Diesel Engine Page 9Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
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.
Working principle of 4-stroke Diesel Engine Page 10Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
Applications of Diesel engines
4-stroke Diesel Engine Page 11Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
Working principle of 4-stroke Diesel Engine Page 12Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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.
4-stroke Diesel Engine Page 13Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
Working principle of 4-stroke Diesel Engine Page 14Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
4-stroke Diesel Engine Page 15Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
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
Working principle of 4-stroke Diesel Engine Page 16Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering
Internal Combustion Engines by Ganesan
Internal Combustion Engines by M L Mathur & S P Sharma
Websitewww.images.google.com
4-stroke Diesel Engine Page 17Author Name: Alfred Franklin.V College Name: St. Xavier’s Catholic College of Engineering