Engine Types, Firing Order and Operation for SS 3

Class: SS 3
Term: First Term
Week: 2
Age: 16 years
Duration: 45 minutes
Subject: Auto Mechanic Work
Topic: ENGINE – DEFINITION AND TYPES
Subject Matter: We have turbine engine, wankel rotary engine

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• Define an engine.
• List two types of engines covered in the lesson.
• Describe the operational sequence of a gas turbine engine.
• Explain the operational sequence of a Wankel rotary engine.
• State the meaning and importance of engine firing order.

Affective Domain

• Appreciate the different designs and complexities of various engine types.
• Value the importance of correct firing order for engine efficiency and smoothness.

Psychomotor Domain

• Identify components of turbine and Wankel engines from diagrams or charts.
• Observe and describe the general operational principles of different engine types.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Auto Mechanics for Senior Secondary Schools, Book 3
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Live vehicle (for general engine observation)
• Posters showing diagrams of gas turbine engines
• Charts illustrating Wankel rotary engine components and operation
• Diagrams explaining engine firing order
• Whiteboard and markers

Rationale for the Lesson

Understanding different engine types and their operational principles is fundamental for any auto mechanic student. This lesson provides essential knowledge about less common but significant engine designs like turbine and Wankel engines, and clarifies the critical concept of firing order, which ensures smooth and efficient engine operation.

Prerequisite/Previous Knowledge

Students should have a basic understanding of internal combustion engines, their main components, and the four-stroke cycle.

Lesson Content/Board Summary

ENGINE – DEFINITION AND TYPES

Definition of an Engine

An engine is a machine designed to convert one form of energy into mechanical energy, which is then used to perform work. In vehicles, engines typically convert chemical energy from fuel into mechanical power to drive the wheels.

Types of Engines

Engines come in various designs, each with unique operational characteristics. This lesson focuses on:

1. Turbine Engine (Gas Turbine Engine)
2. Wankel Rotary Engine

Turbine Engine (Gas Turbine Engine)

A turbine engine is a type of internal combustion engine that operates on the Brayton cycle. It uses a continuous combustion process to produce hot, high-pressure gas that drives a turbine, which in turn powers a compressor and generates thrust or rotational power.

Operational Sequence of a Gas Turbine Engine

The operation of a gas turbine engine involves four main stages:

1. Intake/Compression: Air is drawn into the engine through an inlet and compressed by a compressor, increasing its pressure and temperature.
2. Combustion: The compressed air enters a combustion chamber where fuel is injected and ignited. This continuous combustion significantly increases the temperature and volume of the gas.
3. Expansion/Power: The hot, high-pressure gas expands rapidly and flows through a turbine, causing it to spin. This rotation drives the compressor and can also provide power for other applications.
4. Exhaust: The exhaust gases are expelled from the engine, often providing thrust (as in jet engines) or being used to drive a power turbine.

Wankel Rotary Engine

The Wankel rotary engine is a type of internal combustion engine that uses a triangular rotor instead of reciprocating pistons to convert pressure into rotating motion. It is known for its compact size, smooth operation, and high power-to-weight ratio.

Operational Sequence of a Wankel Rotary Engine

The Wankel engine operates on a four-stroke cycle, but all four strokes occur simultaneously in different parts of the rotor’s rotation within an epitrochoid-shaped housing:

1. Intake: As the rotor tip passes the intake port, a vacuum is created, drawing the air-fuel mixture into the chamber.
2. Compression: As the rotor continues to turn, the volume of the chamber decreases, compressing the air-fuel mixture.
3. Power/Ignition: At maximum compression, the spark plug ignites the mixture, causing a rapid expansion of gases that pushes the rotor, generating power.
4. Exhaust: As the rotor continues its rotation, it uncovers the exhaust port, allowing the spent gases to be expelled from the chamber.

Engine Firing Order

Engine firing order is the sequence in which the spark plugs ignite the air-fuel mixture in the cylinders of a multi-cylinder internal combustion engine. It is crucial for smooth engine operation, balance, and reducing vibrations.

Importance of Firing Order

1. Engine Balance: A carefully chosen firing order helps to balance the forces and moments generated by the reciprocating parts, reducing engine vibration.
2. Smooth Operation: It ensures an even distribution of power strokes, leading to smoother power delivery and less stress on the crankshaft.
3. Reduced Stress: Proper firing order minimizes twisting forces on the crankshaft and other engine components.
4. Optimal Performance: It contributes to the overall efficiency and longevity of the engine.

Example of Firing Order (4-Cylinder Inline Engine)

A common firing order for a four-cylinder inline engine is 1-3-4-2. This means cylinder 1 fires first, followed by cylinder 3, then cylinder 4, and finally cylinder 2, before the sequence repeats.

Teaching Methods/Instructional Techniques

Discussion, Demonstration, Guided Practice, Question and Answer, Explanation, Observation, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes

Teaching Skill: Recalling/Engaging

Teacher’s Activity: The teacher greets the students and reviews the previous lesson on basic engine components. The teacher then introduces the new topic by asking students if they know that not all engines use pistons and cylinders in the same way, leading into the concept of different engine types and firing order.

Pupils’ Activity: Students respond to questions about previous knowledge and listen attentively to the introduction of the new topic.

Learning Point: Engine component recall

Step 2: Definition of Engine

Time: 5 minutes

Teaching Skill: Explaining/Defining

Teacher’s Activity: The teacher defines what an engine is, emphasizing its role in converting energy into mechanical work. The teacher writes the definition on the board.

Pupils’ Activity: Students listen to the definition and ask clarifying questions. They mentally process the definition.

Learning Point: Engine definition

Step 3: Introduction to Engine Types (Turbine and Wankel)

Time: 7 minutes

Teaching Skill: Listing/Illustrating

Teacher’s Activity: The teacher lists the two main engine types to be covered: turbine engine and Wankel rotary engine. Using charts and diagrams, the teacher briefly shows the general appearance of each engine type, highlighting their unique features compared to conventional piston engines.

Pupils’ Activity: Students observe the charts and diagrams, noting the differences in engine appearance and structure. They identify the two engine types.

Learning Point: Engine type identification

Step 4: Turbine Engine Operation

Time: 7 minutes

Teaching Skill: Explaining/Demonstrating

Teacher’s Activity: The teacher explains the operational sequence of a gas turbine engine (intake, compression, combustion, exhaust) using diagrams and posters. The teacher emphasizes the continuous combustion process and how the turbine drives the compressor.

Pupils’ Activity: Students listen to the explanation, observe the diagrams, and try to visualize the flow of air and gas through the turbine engine.

Learning Point: Gas turbine operation

Step 5: Wankel Rotary Engine Operation

Time: 7 minutes

Teaching Skill: Explaining/Illustrating

Teacher’s Activity: The teacher explains the operational sequence of the Wankel rotary engine, focusing on the unique movement of the triangular rotor within the epitrochoid housing. The teacher uses charts to show how all four strokes occur simultaneously.

Pupils’ Activity: Students pay close attention to the unique mechanics of the Wankel engine, asking questions to understand the rotor’s movement and the simultaneous strokes.

Learning Point: Wankel engine operation

Step 6: Engine Firing Order

Time: 5 minutes

Teaching Skill: Defining/Explaining

Teacher’s Activity: The teacher defines engine firing order and explains its critical importance for engine balance, smooth operation, and reduced stress. The teacher provides a common example of a 4-cylinder firing order (e.g., 1-3-4-2) and explains its principle.

Pupils’ Activity: Students listen to the definition and explanation of firing order, understanding why it is essential for engine performance.

Learning Point: Firing order importance

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. What is an engine?
2. Name two engine types discussed today.
3. Briefly describe the operational sequence of a gas turbine engine.
4. What is the significance of engine firing order?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Engine types understanding

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides pupils/students to copy the essential Board Summary notes on engine definition, types, operational sequences, and firing order into their notebooks.

Pupils’ Activity: Pupils/students copy the notes carefully into their notebooks.

Learning Point: Key concepts recording

Step 9: Conclusion

Time: 0 minutes

Teaching Skill: Summarising

Teacher’s Activity: The teacher briefly recaps the main points of the lesson, emphasizing the diversity of engine designs and the importance of understanding their operational principles and firing order.

Pupils’ Activity: Students listen to the summary and prepare for the next activity.

Learning Point: Lesson consolidation

Continuous Assessment/Further Study

Type: Homework

Instruction: Answer the following questions in your notebook.

1. Draw a simple diagram of a Wankel rotary engine and label its main parts.
2. Compare and contrast the operational principles of a gas turbine engine and a conventional four-stroke piston engine.
3. Research and write down the typical firing order for a 6-cylinder inline engine.

Lesson Keywords

• Engine – A machine converting energy into mechanical work.
• Turbine Engine – An engine using continuous combustion to drive a turbine.
• Wankel Rotary Engine – An engine using a triangular rotor instead of pistons.
• Firing Order – The sequence of spark plug ignition in engine cylinders.
• Compression – The process of reducing gas volume, increasing pressure.
• Combustion – The process of burning fuel to release energy.

Differentiation

Support for Weaker Learners: Provide simplified diagrams and flowcharts for the operational sequences. Pair them with stronger learners for note-taking and discussion. Focus on identifying key components and the general idea of operation rather than intricate details.

Extension for Faster Learners: Encourage them to research other less common engine types (e.g., Stirling engine) or delve deeper into the specific applications of turbine and Wankel engines in different industries (e.g., aviation, specific car models).

Suggested Lesson Videos

For visual understanding of engine types and operation, search YouTube for:

• “How a Gas Turbine Engine Works”
• “Wankel Rotary Engine Explained Animation”
• “Engine Firing Order Explained”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have clear, large diagrams or charts of gas turbine and Wankel rotary engines, along with an illustration of engine firing order. If a live vehicle is available, plan how to safely show students the general engine layout without direct interaction with moving parts. Begin by connecting to students’ prior knowledge of conventional engines before introducing the new types. Explain the operational sequences step-by-step, using the visual aids to make the concepts concrete. Emphasize the importance of firing order for engine performance. Allow time for questions and encourage observation. Students should copy the Board Summary notes after the main concepts have been taught and evaluated, ensuring they have accurate information for future study. Reinforce safety protocols if using a live vehicle for demonstration.