The effective compression ratio of diesel engine, why is the compression ratio of diesel engine larg

The compression ratio of modern automobile engines, gasoline engines are generally 8 11 due to the limitation of detonation. There is no knock limit for diesel engines, and the compression ratio is generally 12 22.

The compression ratio indicates the degree to which the gas in the cylinder is compressed as the piston moves from the bottom dead center to the top dead center. The compression ratio is one of the important parameters of the engine. i.e. =va vc

The minimum working volume of the cylinder, that is, the total volume above the piston when the piston is at the top dead center, is called the volume of the combustion chamber, which is represented by VC; When the piston is at the bottom dead center, the total volume above the piston, that is, the maximum volume of the cylinder, is called the total volume of the cylinder, which is expressed by VA.

1. The diesel engine relies on the gas-oil mixture in the cylinder to spontaneously combust when it reaches a certain pressure, while the gasoline engine is ignited and burned with a spark plug after reaching a certain pressure, and it does not need such a high pressure. Specifically:

1. The ratio of the total volume of the cylinder to the volume of the combustion chamber is called the compression ratio. The compression ratio indicates the degree to which the gas is compressed in the cylinder as the piston moves from bottom dead center to top dead center.

2. The larger the compression ratio, the greater the degree of compression of the gas in the cylinder, the higher the pressure and temperature of the gas at the end of compression, the greater the power, but the compression ratio is too high and prone to detonation.

3. The compression ratio is an important structural parameter of the engine. Due to the different nature of fuel, different types of engines have different requirements for compression ratios. Diesel engines require a larger compression ratio, generally between 12-29, while gasoline engines have a smaller compression ratio, between 6-11.

The use of high-grade gasoline can partially increase the compression ratio.

2. A diesel engine is an engine that burns diesel fuel to obtain energy release. It was invented in 1892 by the German inventor Rudolf Diesel, and in honor of the inventor, diesel is represented by his surname Diesel, and diesel engines are also known as diesel engines.

3. Gasoline engine is an engine that uses gasoline as fuel to convert internal energy into kinetic energy. Because gasoline is less viscous and evaporates quickly, gasoline can be injected into the cylinder with a gasoline injection system, and after compression reaches a certain temperature and pressure, it is ignited with a spark plug to make the gas expand to do work. The gasoline engine is characterized by high speed, simple structure, light weight, low cost, stable operation, and convenient use and maintenance.

Gasoline engines are used in large quantities in automobiles, especially small cars.

The compression ratio indicates the degree to which the gas is compressed in the cylinder and also indicates the multiple of the volume change as the gas expands.

Diesel engine belongs to the compression-ignition engine, the compression stroke is close to the end of the diesel injected into the cylinder is by absorbing the heat of the high-temperature and high-pressure air that has been compressed in the cylinder and ignites by itself, in order to create favorable conditions for the spontaneous combustion of the diesel engine, the compression ratio must be designed higher, generally 16 22 is more suitable.

When the compression ratio is too high, due to the high temperature and pressure in the cylinder during the compression process, premature combustion or deflagration of the cylinder mixture will occur. Therefore, the compression ratio of the gasoline engine should not be too high, generally 6 9.

Because the diesel engine relies on the high temperature generated by compressed air to obtain kinetic energy through high-pressure fuel injection, so that the fuel is burned. The gasoline engine is a fuel mixer that compresses part of the fuel mixer and obtains kinetic energy through ignition combustion. They don't work the same way.

Therefore, diesel fuel must have a higher compression ratio to reach the temperature at which diesel burns.

Diesel engine. The diesel engine relies on the movement of the piston to compress the mixture (the mixture of diesel and air) to do work to make the diesel reach the ignition point. This requires a larger compression ratio.

Gasoline engines, on the other hand, require a smaller compression ratio than diesel engines because they have spark plugs to help gasoline reach the ignition point.

The diesel engine is compression-ignition, and there is no large compression ratio compression-ignition that cannot be injected into the cylinder of diesel;

The gasoline engine is ignited, and the gasoline is sucked into the cylinder with the air, and the compression ratio will form premature ignition, which affects the normal operation.

The cylinder of a diesel engine is filled with pure diesel, while the gasoline engine is a mixture of air and gasoline.

This is hard to say, because diesel engines also have electronically controlled ignition. Generally, the compression ratio of a 4-stroke diesel engine (without ignition system) is larger than that of a gasoline engine, so the horsepower of a diesel engine is greater than that of a gasoline engine of the same displacement at the same speed. The horsepower of a diesel engine is reflected in the compression ratio, while the gasoline engine is reflected in the speed.

The compression ratio of modern diesel engines is generally between 12 and 22, but the compression ratio of ultra-supercharged diesel engines can be as low as 8. A few years ago, the compression of a gasoline engine was 6 10, but today it is generally between 9 12.

It depends on the ignition point of the fuel used. Usually gasoline only needs 500 degrees to ignite, while diesel needs 700 degrees to ignite, in order to reach the ignition temperature of diesel, so the compression ratio of diesel engine is high.

Although diesel and gasoline engines are both internal combustion engines, the characteristics of the fuels used vary greatly, resulting in significantly different operating methods and output characteristics. Diesel and gasoline are two completely different fuels, and the spontaneous ignition temperature of diesel is low, about 220, and the viscosity is large and not volatile; The autoignition temperature of gasoline is high, about 415 530, and the viscosity is small and volatile.

The compression ratio of a diesel engine is greater than that of a gasoline engine. The compression ratio of gasoline engines is basically limited to 9-11:1, while that of diesel engines can reach 17-24:1.

Although diesel has a low ignition point, it has a stable temperament, unlike gasoline, which is naturally unruly and difficult to control. Therefore, the diesel engine can be compression-ignition without worrying about the detonation of the engine.

But gasoline is the opposite. As a result, diesel engines have larger blocks, liners, and connecting rods than gasoline engines. Then compared with the engine of the same displacement, the diesel engine is naturally larger.

The role of the engine compression ratio:

Engine compression can increase the pressure, which can make the density of the gas larger, and the distance between molecules will be smaller, so that the fuel molecules and oxygen molecules will be closer together, and the combustion speed will be faster;

Temperature allows gas molecules to move faster, making it easier for fuel and oxygen molecules to interact with each other, which makes gas mixtures more likely to ignite. Moreover, the smaller combustion space can complete the combustion faster, and the faster combustion process also improves the performance.

The usual low compression ratio refers to a compression ratio of less than 10, and a compression ratio of more than 10 is considered a high compression ratio engine. The level of the compression ratio will directly affect the grade of gasoline used in the engine, generally speaking, the larger the compression ratio, the higher the gasoline grade required.

If gasoline is used below the recommended mark, problems such as "cylinder knocking", increased engine vibration, uneven driving, etc., can also impair engine performance and shorten service life.

In general, the compression ratio is 92 or 93 gasoline; 95 gasoline should be used for the compression ratio above.

Hello, gasoline engine ignition, diesel engine is compression ignition, so diesel engine compression ratio is larger, I hope it can help you.

Generally speaking, diesel engines have a large compression ratio. The compression ratio of diesel engines is generally 15-22, and the compression ratio of gasoline engines is generally 6-10. This is related to the characteristics of gasoline and diesel, diesel has a high viscosity and is not easy to evaporate, and the combustible mixture is ignited by compression ignition, which is suitable for low-speed engines, but the output torque is large and the compression ratio is large.

Diesel engine: Diesel is compression-ignited. Because diesel has a relatively low burst point, it can be burned by pressure.

Gasoline engine: Gasoline is ignited by spark plugs. Because the deflagration point of gasoline is relatively high, it is not easy to compress ignition.

When the compression ratio is larger, the pressure in the cylinder can be increased.