What are the four strokes of the engine?

A gasoline engine mixes gasoline and air into a combustible mixture, which is then entered into the cylinder and ignited by an electric spark. Each working cycle of a four-stroke gasoline engine goes through the following four strokes:

1.Intake stroke In this stroke, the intake valve is opened, the exhaust valve is closed, the cylinder communicates with the carburetor, the piston moves from the top dead center to the downward karma point, the volume above the piston increases, and a certain vacuum degree is generated in the cylinder. The combustible mixture is sucked into the cylinder.

When the piston reaches the bottom dead center, the crankshaft turns half a circle, the intake valve closes, and the intake stroke ends.

2.Compression stroke After the intake stroke is completed, the intake and exhaust valves are closed at the same time. The crankshaft continues to rotate, the piston moves from the bottom dead center to the top dead center, the volume above the piston decreases, and the mixture entering the cylinder is gradually compressed, increasing its temperature and pressure.

When the piston reaches the top dead center, the compression stroke ends.

3.Power stroke Towards the end of the compression stroke, the spark plug emits an electric spark that ignites the combustible mixture. Due to the rapid combustion and expansion of the mixture, the pressure can reach 3 5 MPa in a very short time, and the maximum temperature is about 2200 2800 K.

The high-temperature, high-pressure gas pushes the piston down rapidly, and rotates the crankshaft through the connecting rod to work externally.

4.Exhaust stroke After the mixture is burned, it becomes exhaust gas, in order to facilitate the next working cycle, these exhaust gases should be discharged from the cylinder in time, so at the end of the work stroke, the exhaust valve is opened, the piston moves up, and the exhaust gas is discharged into the atmosphere. When the piston reaches the top dead center, the exhaust valve closes and the crankshaft turns to two weeks, completing a working cycle.

The working process of the engine is divided into four processes: air intake, compression, work and exhaust. The four-stroke engine accomplishes these four processes in four strokes of the piston moving up and down.

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Intake stroke: The intake valve is open and the exhaust valve is closed. As the piston moves from top dead center to bottom dead center, the volume above the piston increases, and the pressure in the cylinder decreases, resulting in vacuum suction. Suck the gas mixture into the cylinder.

Compression stroke: The intake and exhaust valves are closed, and the piston moves from the bottom dead center to the top dead center to press the mixed gas to the combustion chamber.

Work stroke: At the end of compression, the intake valve and exhaust valve are still closed, the spark plug emits an electric spark, igniting the combustible mixture, and the gas after combustion expands violently, generating huge pressure, forcing the piston to go down rapidly, and the crankshaft is rotated through the connecting rod.

Exhaust stroke: The exhaust valve opens, the intake valve closes, and the piston moves from the bottom dead center to the top dead center to expel the exhaust gas.

At the end of the exhaust stroke, the piston returns to the top dead center. This completes a work cycle. The crankshaft then continues to rotate thanks to the inertia of the flywheel, starting the next cycle. And so on, and so on, and the engine keeps running.

Air intake, compression, combustion, exhaust.

Principle of internal combustion engine Two-stroke engines and four-stroke engines work differently, and most automobile engines are four-stroke.

Four-stroke Four-stroke means that the piston inside the engine is fully moving, and it takes four processes at a time.

1. Inhale (at this time, the valve is opened, if it is a four-valve, open two).

2. Compression (at this time, all the valves are closed, and the piston moves from bottom to top to compress the gasoline and air mixture that is sucked in).

3. Do work (when the volume of the gas mixture is compressed to the minimum, the spark plug is ignited, which is deflagration, and the piston at the top is pushed to the lowest end to drive the crankshaft).

4. Exhaust (open the remaining valve and discharge the exhaust gas out of the cylinder block, which is the exhaust gas).

Note: The above processes are all gasoline engines.

Two-stroke two-stroke.

Two-stroke engines and four-stroke engines complete a work cycle, and their intake, exhaust valves, or intake, exhaust, and scavenging ports are only opened and closed once, but the time period for opening and closing is different. For every revolution of the crankshaft of a two-stroke engine, there is a power stroke. Therefore, under the same conditions such as rotational speed, intake conditions, etc.

Theoretically, a two-stroke engine should produce twice as much power as a four-stroke engine with the same working volume. However, because the exhaust exhaust of the two-stroke engine is not complete, and at the same time, because the scavenger closes before the exhaust port and produces additional exhaust, in practice, the two-stroke engine is not equal to the four-stroke engine, but doubles.

An engine is a machine that can convert other forms of energy into mechanical energy, such as internal combustion engines (reciprocating piston engines), external combustion engines (Stirling engines, steam engines, etc.), jet engines, electric motors, etc. For example, the internal combustion engine usually converts chemical energy into mechanical energy.

The engine is applied to both the power generation unit and the entire machine including the power unit (e.g., gasoline engine, aero engine). The engine was first born in England, so the concept of the engine also originated from the English language, and its original meaning refers to the "mechanical device that produces power".

The four strokes are equipped with intake and exhaust valves, ventilation, and most of the two strokes do not have intake and exhaust valves, and most of them are used for DC scavenging and ventilation quality, and the two strokes are widely used in large ships for your reference.

First, the structure is different The thermal part of the two-stroke motorcycle is mainly composed of cylinder heads, cylinders, pistons, piston rings and other parts. The thermal part of a four-stroke motorcycle is mainly composed of a cylinder head, a cylinder head head, a cylinder, a piston, a piston ring and a valve mechanism. The valve mechanism is composed of valves, valve guides, valve seats, valve springs, valve cams, valve chains, valve sprockets, chain tensioners, rocker arms and other parts.

Comparatively speaking, two-stroke motorcycles are smaller than four-stroke motorcycles, simple in structure, light in weight, and easy to manufacture and maintain. Second, the working process is different In order to make the engine work and burn continuously, a series of actions need to be repeated in a certain order. First, the mixed gas is sucked into the cylinder, and the gas is compressed and burned to expand, and the gas produced by combustion is discharged from the cylinder. As.

The working principle of the four-stroke gasoline engine is: 1. Suction stroke, the piston descends, and the mixture is sucked in. 2. Compression stroke, piston rise, compression mixture.

3. Do the power stroke, ignite the fuel, and press the piston down to do the work. 4. Exhaust stroke, piston rises, and exhaust gas is discharged. There are four strokes of air intake, compression, combustion work and exhaust to complete a working cycle.

The four-stroke engine is divided into four cycles: air intake, compression, work and exhaust.

Each working cycle of the four-stroke gasoline engine goes through the following four strokes:1Intake stroke 2Compression stroke 3Work Trip 4Exhaust stroke.

1. The working principle of four-stroke gasoline engine.

Each working cycle of a four-stroke engine needs to go through four strokes of air intake, compression, work (expansion) and exhaust, and the corresponding piston reciprocates up and down four times, and the corresponding crankshaft rotates 720° (two turns). The engine cycle dynamometer diagram is usually used to represent the relationship between the cylinder volume and the pressure. The area enclosed by the curve in the dynamometer diagram represents the work done by the gas in a single cylinder throughout the engine's working cycle.

Intake stroke (shown in Figure A, using naturally aspirated as an example).

During the intake process, the exhaust valve closes, the intake valve opens, and the piston moves a stroke from the top dead center to the bottom dead center, forming a vacuum in the cylinder, and the fresh combustible mixture is sucked into the cylinder; The crankshaft turns clockwise from 0° to 180°.

When the piston moves from the top dead center to the bottom dead center, there is resistance to the air intake system, so the gas pressure in the cylinder at the end of the air intake is slightly lower than the atmospheric pressure, which is 0 090mpa。The temperature of the combustible mixture flowing into the cylinder rises to 370 403K because it comes into contact with high-temperature parts such as cylinder walls and piston tops and mixes with the high-temperature residual exhaust gas left by the previous stroke (exhaust stroke).

On the dynamometer diagram, the intake stroke is represented by the curve RA. The curve Ra is located below the atmospheric pressure line, and the difference between it and the ordinate of the atmospheric pressure line indicates the vacuum degree in the cylinder.

The naturally aspirated engine has a smooth power delivery and does not accelerate abruptly due to changes in engine speed. And the engine has a long service life and simple maintenance.

Compression stroke (shown in Fig. B).

In order to make the combustible mixture that sucks people can burn rapidly, in order to produce a large gas pressure and make the engine work, the combustible mixture must be compressed before combustion, which is the compression stroke. At the end of the intake stroke, the piston moves from bottom dead center to top dead center, and the crankshaft turns from 180° to 360°. At this time, the intake and exhaust valves are closed.

As the volume of the cylinder shrinks, the combustible mixture is compressed and its temperature and pressure increase. The compression stroke continues until the piston reaches the top dead center. At the end of compression, the temperature of the combustible mixture is 600 750K, and the pressure of the combustible mixture is .

On the dynamometer diagram, the compression stroke is represented by the curve AC.

At the end of compression, the pressure and temperature of the combustible mixture depend on the compression ratio, the higher the compression ratio, the faster the combustion rate, and therefore the more power the engine emits, and the better the economy. However, when the compression ratio is too large, not only can not further improve the combustion condition, but abnormal combustion phenomena such as deflagration and surface ignition will occur.

The four-stroke internal combustion engine works with an aspiration stroke, the intake valve opens, the exhaust valve closes, the piston moves downward, and the gasoline and air mixture enters the cylinder. With a compression stroke, both the intake and exhaust valves are closed, the piston moves upwards, and the gasoline-air mixture is compressed. Converts mechanical energy into internal energy.

At the end of the power stroke, the spark plug produces an electric spark, which causes the fuel to burn violently, producing a gas with high temperature and high pressure. The high-temperature and high-pressure gas pushes the piston to move downward, drives the crankshaft to rotate, and does work externally. Among the four strokes, only the power stroke does the work externally, and the other three strokes are completed by the inertia of the power stroke.

Convert internal energy into mechanical energy. Exhaust stroke, the intake valve closes, the exhaust valve opens, and the piston moves upwards to expel the exhaust gas from the cylinder. 2 Introduction to Internal Combustion Engine The internal combustion engine is a kind of power machinery, which is a heat engine that burns fuel inside the machine and converts the heat energy released into power directly.

In a broad sense, the internal combustion engine not only includes the reciprocating piston internal combustion engine, the rotary piston engine and the free piston engine, but also includes the rotary impeller jet engine, but the internal combustion engine usually refers to the piston internal combustion engine, the piston internal combustion engine was the most common in the past. A piston internal combustion engine mixes fuel and air and burns it in its cylinder, and the heat energy released causes the cylinder to produce high-temperature and high-pressure gas. The gas expansion pushes the piston to do work, and then outputs the mechanical work through the crank connecting rod mechanism or other mechanisms to drive the driven machinery to work.

The four strokes of the engine include intake stroke, compression stroke, power stroke and exhaust stroke.

1. Suction stroke.

The intake valve (L) opens, the piston moves downward, the mixture of fuel and air enters the cylinder, and when the piston movement reaches its lowest, the intake valve closes.

2. Compression stroke.

The intake and exhaust valves are closed, the piston moves upward, the mixture of fuel and air is compressed, and when the piston moves to the top, the compression stroke ends, converting the mechanical energy into internal energy.

3. Do power stroke.

The spark ignites the gas mixture, and the burning gas expands dramatically, pushing the piston downward, converting the internal energy into mechanical energy.

4. Exhaust stroke.

The exhaust valve (R) is opened, the piston moves upwards to expel the exhaust gases after combustion, and when the piston moves to the very top, the exhaust valve is closed.

<> intake stroke. The intake stroke refers to the piston inside the cylinder, the next activity, when the intake valve is opened, the exhaust valve will be closed, and a vacuum can be generated in the cylinder to mix and ignite the air and fuel of the fresh buried bridge.

If the fuel combustion in this process is not sufficient, there will be a lot of fuel waste, and the exhaust gas will have a lot of pollution to the air.

Compression stroke. Compression stroke means that when the intake valve and exhaust valve are closed, the piston moves from bottom to top, compresses the mixed gas in the cylinder, compresses it to the extreme, and then ignites the gas in the cylinder, so as to obtain the power required by the car.

During the compression process, if the compression does not reach the lowest point of compression, the power obtained by the ignited gas engine will be very small, and the car will have insufficient power.

Do the work stroke. The power stroke requires both the intake and exhaust valves to be closed, and the spark is blocked.

The compressed gas mixture is ignited, causing the gas mixture to burn and explode with powerful power, pushing the spark plug to the other side. The spark ignites the gas mixture, releasing a large amount of energy, and then the control computer distributes the high-pressure fire to the various valves, so that the car can gain power.

Exhaust stroke. Exhaust stroke refers to the intake valve closed, the exhaust valve open, the cylinder with ignited exhaust gas, no combustion mixture gas, will be moved up by the piston, gas through the exhaust valve discharge, then the mixed gas without combustion will also be discharged, so if the combustion process is not sufficient, the gasoline in the mixed gas discharged at this time will cause serious damage to the environment.

These four strokes are repeated and continuous, providing a constant stream of power to the car.