Heat Engines Overview

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Questions and Answers

What defines a heat engine?

An engine that operates solely on electric energy.

An engine that converts sunlight into mechanical power.

An engine that stores mechanical energy for later use.

An engine that uses heat energy to generate mechanical power. (correct)

Which of the following is classified as an external combustion engine?

Piston engine

Gas turbine

Rocket engine

Stirling engine (correct)

Which type of ignition is used in a gasoline engine?

Low Speed Ignition

Fuel Injection Ignition

Electric-Spark Ignition (correct)

Constant Pressure Ignition

What type of cycle does a diesel engine primarily use?

Constant Pressure Cycle Signup and view all the answers

In which classification does an engine with a horizontal layout fall?

According to Direction of Cylinder Signup and view all the answers

What example of a cooling system is commonly used in engines?

Water Cooled Signup and view all the answers

Which configuration represents an engine with multiple cylinders arranged in a 'V' shape?

V Type Engine Signup and view all the answers

What is a characteristic of a rocket engine?

Functions relying on internal combustion and expelling exhaust gases for thrust. Signup and view all the answers

What is the primary function of the piston in an internal combustion engine?

To convert energy released during combustion Signup and view all the answers

Which type of piston is best suited for applications that require efficient combustion and is commonly found in naturally aspirated engines?

Flat – Top Pistons Signup and view all the answers

Which of the following materials is commonly used for cylinder construction due to its lightweight and excellent thermal conductivity?

Cast Aluminum Alloy Signup and view all the answers

In the four-stroke cycle, what occurs during the compression stroke?

The piston compresses the fuel-air mixture Signup and view all the answers

What type of piston bubbles in the middle, increasing the surface area available on the top for better combustion?

Dome Pistons Signup and view all the answers

What design consideration is essential for pistons in order to withstand high pressures during operation?

Enormous strength to withstand high pressure Signup and view all the answers

During which stroke in the four-stroke cycle is a spark plug activated to ignite the fuel-air mixture?

Compression Stroke Signup and view all the answers

What is the function of the crankshaft in an engine?

To convert linear motion into rotational motion Signup and view all the answers

What is the primary function of a carburettor in an internal combustion engine?

To mix fuel with air for combustion Signup and view all the answers

During the operation of a carburettor, what role does the venturi play?

It increases air velocity and creates a low-pressure area Signup and view all the answers

Which type of spark plug is best suited for an engine with electronic ignition?

Platinum Spark Plug Signup and view all the answers

What is the primary role of connecting rods in an internal combustion engine?

To link the pistons and the crankshaft. Signup and view all the answers

How does the throttle valve function in the carburettor system?

It controls the fuel supply rate Signup and view all the answers

Which material is commonly used for high-performance applications in connecting rods?

Billet steel Signup and view all the answers

Which step in the carburettor operation describes the mixing of fuel and air before entering the cylinder?

Step 6 Signup and view all the answers

What component is responsible for controlling the timing of the intake and exhaust valves?

The camshaft Signup and view all the answers

In which type of engine configuration are the valves located beside the combustion chamber?

Side Valve Signup and view all the answers

Which material is not typically associated with spark plugs designed for high-heat applications?

Copper Signup and view all the answers

What is the key feature of direct fuel injection in internal combustion engines?

Fuel is atomized and injected directly into the cylinder. Signup and view all the answers

What results from the gradual drop in fuel pressure as described in the carburettor steps?

The fuel supply valve at the top opens Signup and view all the answers

How do valve trains optimize engine performance?

By regulating the timing of valve openings and closings. Signup and view all the answers

What is the primary purpose of tuning an engine’s air-fuel mixture adjustment?

To improve thermal efficiency and performance Signup and view all the answers

Which of these valve types features the camshaft located in the cylinder head?

Overhead Cam (OHC) Signup and view all the answers

What is the function of exhaust valves in an internal combustion engine?

To release burnt gases after combustion. Signup and view all the answers

Study Notes

Heat Engine

A heat engine uses heat energy from fuel to generate mechanical power.
It can power machines and generate electrical power.

Classifications of Heat Engines

External Combustion Engine - Fuel burns outside the engine cylinder
- Steam Engine - Uses steam generated from burning fuel to power a piston or rotary mechanism.
  - Rotary Steam Engine - Uses steam to rotate a shaft.
  - Piston Steam Engine - Uses steam to move a piston back and forth.
- Stirling Engine - Uses a closed system with a working fluid (typically air or hydrogen) to convert heat energy into mechanical.
Internal Combustion Engine - Fuel burns inside the engine cylinder
- Piston or Reciprocating Engine - Uses a piston moving within a cylinder to convert combustion energy into power.
- Rotary Engine - Employs a rotating mechanism to convert combustion energy into power
- Gas Turbine Engine - Utilizes a rotating turbine powered by hot, expanding gas from combustion.
- Jet Engine - Generates thrust by expelling hot gases, commonly used in aircraft.
- Rocket Engine - Uses rocket propellants for propulsion, typically in space applications.

Classifications of Piston Engines

Ignition
- Electric-Spark Ignition - Uses a spark plug to ignite the fuel-air mixture.
- Fuel Injection Ignition - Injects fuel directly into the combustion chamber where it ignites without a spark.
Fuel
- Gasoline Engine - Burns gasoline as fuel.
- Kerosene Engine - Burns kerosene as fuel.
- Diesel Engine - Burns diesel fuel, which ignites from heat and pressure.
- Gas Engine - Burns natural gas or other gaseous fuels.
Thermal Mechanics
- Constant Volume Cycle (Otto Cycle Engine) - The combustion process takes place at a constant volume.
- Constant Pressure Cycle Engine (Diesel Cycle Engine) - The combustion process takes place at a constant pressure.
Practical Cycle
- Two-Stroke Cycle Engine - Completes the power cycle in two strokes of the piston.
- Four-Stroke Cycle Engine - Completes the power cycle in four strokes of the piston.
Number of Cylinders
- One-Cylinder Engine - Engine with a single cylinder.
- Two-Cylinder Engine/ Multiple-Cylinder Engine - Engine with two or more cylinders.
Direction of Cylinder
- Horizontal Type Engine - The cylinder is positioned horizontally.
- Vertical Type Engine - The cylinder is positioned vertically.
Disposition or Arrangement of Cylinders
- Linear Type Engine - Cylinders are arranged in a straight line.
- Oppose Type Engine - Cylinders are arranged in opposing pairs.
- V, W, X, H Type Engine - Cylinders are arranged in a V, W, X, or H shape.
- Star Type Engine - Cylinders are arranged radially around a central crankshaft.
Cooling Systems
- Water Cooled - Uses a water-based cooling system to regulate engine temperature.
- Air Cooled - Uses air to cool the engine.
Crankshaft Speed
- Low Speed - Rotates at 800 rpm and below.
- Medium Speed - Rotates between 700 to 2500 rpm.
- High Speed - Rotates at 1000 rpm and above.
Action
- Single Action - The piston is powered only on one side.
- Double Action - The piston is powered on both sides.
Use
- Farm - Used in agricultural applications.
- General Land - Used in various land-based applications.
- Marine - Used in maritime applications.
- Generator or Dynamo - Used to generate electrical power.

Connecting Rods

Connecting rods link pistons to the crankshaft
Materials used: Cast iron for cost-effective engines, forged steel for high-performance applications, billet steel for high-strength racing engines.

Valve & Valve Train

Controls the operation of intake and exhaust valves in an internal combustion engine

Intake Valves:

Allow air-fuel mixture (gasoline engines) or air (diesel engines) to enter combustion chamber.

Exhaust Valves:

Release burnt gases (exhaust) from the combustion chamber after the power stroke.

Types of Valves:

Overhead Valve (OHV): Valves located in the cylinder head above the combustion chamber. Camshaft is in the engine block.
Overhead Cam (OHC): Camshaft(s) located in the cylinder head, directly above the valves.
Side Valve: Valves located beside the combustion chamber, within the engine block. Camshaft operates via pushrods and rocker arms.

Valve Train Components:

Camshaft, rocker arm, pushrods, lifter

Valve Train Function:

Essential for controlling the timing and operation of engine valves.
Ensure intake and exhaust valves open and close at the right times for optimal engine performance.

Fuel Injector

Atomizes and injects fuel into the combustion chamber.
Precisely delivers fuel at the optimal point in the combustion cycle.

Types of Fuel Injection Systems:

Direct Fuel Injection (DFI): Injector placed inside the cylinder for direct fuel injection.
Port Fuel Injection (PFI): Fuel delivered directly into the intake manifold or cylinder head.
Throttle Body Injection (TBI): Single or dual injectors mounted in the throttle body. Air enters manifold before fuel is sprayed onto the valve, using the valve's heat to atomize the fuel.

Cylinder Materials and Design Considerations

Typically made of cast iron or aluminum.

Piston

Key component converting energy released during combustion.
Movement:
- Intake stroke: Piston moves downward, increasing volume for fuel-air mixture entry.
- Compression stroke: Intake valve closes; Piston moves upward, compressing the fuel-air mixture. Spark plug ignites it.
- Power stroke: Combustion pushes the piston down, creating the power output.
- Exhaust stroke: Exhaust opens; remaining exhaust gas is pushed out by the upward-moving piston.

Types of Pistons:

Flat-top: Ideal for efficient combustion in naturally aspirated engines.
Dish: Shaped like a dish, used in boosted applications, typically with a lower compression ratio.
Dome: Opposite of a dish, with a center dome, providing more surface area and less compression.

Piston Design Considerations:

Strong to withstand high pressures.
Lightweight to minimize inertia forces.

Crankshaft

Transforms linear motion of the pistons into rotational motion.
Rotational motion is transferred to the vehicle's drivetrain.

Carburetor:

Mixes fuel and air for combustion in an internal combustion engine.

How a Carburetor Works:

Air enters the carburetor through an air filter.
Air passes through a venturi (narrow section), increasing velocity and creating low pressure.
Fuel is drawn from the fuel chambers due to the low pressure.
The throttle valve regulates fuel consumption.
Fuel and air mixture enter the cylinder.
The float chamber continues to supply fuel while the valve at the top opens as fuel pressure drops.
The spark ignites the combustion mixture within the cylinder.
The process repeats as the combustion occurs.

Carburetor Tuning:

Idle Speed Adjustment.
Air-Fuel Mixture Adjustment.
Test and Fine-tune.

Spark Plug:

Creates a spark to ignite the fuel/air within engine cylinders.

Types of Spark Plugs:

Copper Spark Plug: Copper core, best for low-heat range applications.
Platinum Spark Plug: Copper core with platinum coating, ideal for engines with electronic ignition.

Design of a Spark Plug:

(No further detail provided in the text).

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Description

This quiz explores the fundamentals of heat engines, detailing both external and internal combustion engines. You will learn about various types of engines, including steam engines and gas turbines, and how they convert heat energy into mechanical power. Test your knowledge on the classifications and mechanisms of these essential machines.