Key points of the four-stroke working cycle of an aviation piston engine

The key points of the four-stroke working cycle of an aviation piston engine can be summarized as follows:

First, four stroke cycle overview

The four-stroke working cycle of an aviation piston engine refers to the fact that the engine needs to go through four strokes to complete a full working process. These four strokes are, in sequence, the intake stroke, the compression stroke, the combustion stroke (also known as the power stroke), and the exhaust stroke. Each stroke corresponds to a specific movement of the piston within the cylinder, as well as the opening and closing states of the valves.

Second, key points of the four-stroke working cycle

Intake stroke

Piston movement: The piston moves downward from the top dead center (the highest point of the piston's movement within the cylinder) to the bottom dead center (the lowest point of the piston's movement within the cylinder).

Valve status: The intake valve is open and the exhaust valve is closed.

Process description: As the piston moves downward, the volume inside the cylinder gradually increases, creating a certain vacuum degree. At this point, the mixture of air and fuel (usually a mixture of gasoline and air in aviation piston engines) is drawn into the cylinder through the open intake valve.

Compression stroke

Piston movement: The piston moves upward from the bottom dead center of the cylinder to the top dead center.

Valve status: Both the intake valve and the exhaust valve are closed.

Process description: As the piston moves upward, the volume inside the cylinder gradually decreases, causing the mixture of air and fuel to be compressed. During this process, the pressure and temperature of the mixture gradually increase, preparing for the subsequent combustion stroke.

Combustion stroke (power stroke)

Piston movement: The piston starts to move downward from a position close to the top dead center.

Valve status: Both the intake valve and the exhaust valve are closed.

Process description: When the piston approaches the top dead center, the spark plug generates an electric spark, igniting the compressed mixture. After the mixture burns, it expands rapidly, generating high-temperature and high-pressure gas. These gases push the piston downward and drive the crankshaft to rotate through the connecting rod, thereby converting internal energy into mechanical energy.

Exhaust stroke

Piston movement: The piston moves upward from the bottom dead center of the cylinder to the top dead center.

Valve status: The intake valve is closed and the exhaust valve is open.

Process description: As the piston moves upward, the volume inside the cylinder gradually decreases, causing the exhaust gas after combustion to be discharged outside the cylinder. Waste gas enters the exhaust system through the open exhaust valve and is eventually discharged into the atmosphere.

Third, the characteristics of the four-stroke working cycle

Periodicity: The four-stroke working cycle is periodic, with each stroke corresponding to a specific movement of the piston within the cylinder and the opening and closing states of the valves.

Coordination: The four strokes need to be closely coordinated to ensure the normal operation of the engine. For instance, the intake stroke and the exhaust stroke need to control the opening and closing of the intake valve and the exhaust valve respectively, while the compression stroke and the combustion stroke need to ensure the correct compression and combustion of the mixture.

Efficiency: Through the four-stroke working cycle, the aviation piston engine can efficiently convert the chemical energy of the fuel into mechanical energy, thereby driving the aircraft to fly.

Fourth, the application of the four-stroke working cycle

The four-stroke working cycle of aviation piston engines has extensive applications in fields such as light low-speed aircraft and unmanned aerial vehicles. This type of engine has the advantages of simple structure, high reliability and convenient maintenance, and can meet the requirements of power units in these fields.

In summary, the four-stroke working cycle of an aviation piston engine is a complex and coordinated process. Through the close cooperation of the four strokes, the goal of converting the chemical energy of the fuel into mechanical energy is achieved.