Lesson Notes By Weeks and Term - Senior Secondary 3

TERM – 1^ST TERM

WEEK SIX

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: AUTO MECHANICAL

Topic: ENGINE II

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Discuss the principle of operation of a gas turbine

II.) Define firing order

III.) Identify firing order for different types of engines

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

ENGINE II

Principle of operation of a gas turbine

The principle of operation of a gas turbine engine involves several key steps:

1. Intake: Air is drawn into the engine through an intake, where it is compressed by a series of rotating compressor blades. The compressor increases the pressure and density of the air before it enters the combustion chamber.
2. Combustion: In the combustion chamber, fuel is injected and mixed with the compressed air. The mixture is ignited, either by spark plugs (in some aircraft engines) or by the high temperature and pressure of the compressed air itself. This combustion process releases a large amount of energy in the form of hot, high-pressure gases.
3. Expansion: The hot gases produced by combustion expand rapidly, driving a series of turbine blades mounted on a shaft. This is often referred to as the gas generator turbine. As the gases flow over the turbine blades, they transfer some of their energy to the turbine, causing it to rotate.
4. Exhaust: After passing through the gas generator turbine, the exhaust gases exit the engine through a nozzle, creating a high-velocity jet of exhaust.

Firing Order

The firing order of an engine refers to the sequence in which each cylinder receives a spark from the ignition system to ignite the fuel-air mixture. The firing order is determined by the engine's design and configuration, such as the number of cylinders and their arrangement (inline, V, flat, etc.).

Regarding the firing order for different types of engines, here are the typical firing orders for some common engine configurations:

1. Inline Engines (Straight Engines): Imagine the cylinders lined up in a row, and they fire one after another, usually in a zigzag pattern.

   - Firing order: The cylinders fire in a sequence like 1-3-4-2 (for a 4-cylinder engine).

2. V Engines: In a V8 engine, for example, the firing order might be 1-8-4-3-6-5-7-2, where the cylinders are arranged in a V shape and fire in a specific order.

   - Firing order: The sequence depends on the number of cylinders and the engine configuration (e.g., V6, V8, V10).

3. Flat Engines (Boxer Engines): Picture the cylinders lying flat, facing each other in pairs, and firing in a specific order.

   - Firing order: Typically, it's 1-3-2-4 for a 4-cylinder engine.

4. Rotary Engines (Wankel Engines): These engines have a unique design where the rotor spins in a circular motion, and the firing order follows a specific pattern.

   - Firing order: It varies based on the engine design, but for Mazda rotary engines, it's often 1-3-2.

EVALUATION: 1. Briefly discuss the principles of operation of a gas turbine

2. Identify the firing order for: (I) V Engines (ii) Flat engine

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively