Engine-a machine that converts some form of energy into mechanical energy. Its function is to convert the chemical energy of liquid or gas into heat energy, and then convert the heat energy into mechanical energy through expansion, and output power to the outside world. The power of the car comes from the engine. The engine is the heart of the car, which provides power for the car to walk. The car is dynamic, economical and environmentally friendly. Simply put, the engine is an energy conversion mechanism, that is, when the combustion gas expands in a sealed cylinder, it pushes the piston to do work and converts the thermal energy of gasoline (diesel) into mechanical energy, which is the most basic principle of the engine. All the structures of the engine are used for energy conversion. Although the engine has gone through 100 years with the automobile, it has been greatly improved in design, manufacturing, technology, performance and control, and its basic principle remains unchanged. This is an era of creativity. Those engine designers constantly integrate the latest technology with the engine, turning the engine into a complex mechatronics product, which makes the engine performance.

First, the role of automobile engines

Automobile engine is a device that provides power for automobile, is the heart of automobile and is an energy conversion device. Its function is to burn gasoline (diesel oil) in a sealed cylinder, and then convert thermal energy into mechanical energy through gas expansion to push the piston to do work. According to different power sources, automobile engines can be divided into diesel engine, gasoline engine, electric vehicle motor and hybrid power.

Second, the classification of automobile engines

1. According to the working mode of the intake system, it can be divided into four types: natural inhalation, turbocharging, mechanical supercharging and double supercharging.

2. According to the piston movement mode, it can be divided into two types: reciprocating piston internal combustion engine and rotary piston engine.

3. In-line engines, V-type engines, W-type engines and horizontally opposed engine are classified according to cylinder arrangement.

4. According to the number of cylinders, it can be divided into single-cylinder engine and multi-cylinder engine. Modern cars mostly use three-cylinder, four-cylinder, six-cylinder and eight-cylinder engines.

5. According to different cooling methods, it can be divided into water-cooled engine and air-cooled engine. The water-cooled engine cools evenly.

6. According to the number of strokes, it can be divided into four-stroke internal combustion engines and two-stroke internal combustion engines. Four-stroke internal combustion engines are widely used in automobile engines.

7. Classification by fuel supply mode: carburetor engine, EFI engine and in-cylinder direct injection engine.