Diesel engine ignition control, the ignition principle of diesel engine

There is a misunderstanding in this problem, the diesel engine is not compressed, but ignited. The ignition time of the diesel engine is the injection time of the injector, and the traditional injector uses timing gears and mechanical advancers to control the accurate injection time. The new electronically controlled common rail fuel injection system now uses a computer to control the injector's injection time.

The injection time is slightly earlier than the ignition time.

Horn. The working sequence of the diesel engine should be: the piston goes down to fresh air, then the piston rises and begins to compress the fresh air, with the increase of air pressure, the temperature of the compressed fresh air will rise sharply, and the temperature when it reaches the top dead center exceeds the ignition point of the diesel, then the injector is opened, and the atomized diesel enters the combustion chamber and is ignited.

Fuel injection and combustion are basically synchronized, and the injection time will continue to be slightly earlier as the rpm increases.

The ignition time is controlled by the spark plug in the gasoline engine, while the ignition time is controlled by the fuel injection time of the injector.

At present, many diesel engines have an EPI (electronically controlled fuel injection) system. Therefore, the ICU in the engine will issue an ignition command at the right time.

Ordinary mechanical pump, which can adjust the injection advance angle to control the ignition time. There is no way to do it with electronic control, unless you modify the computer module program.

With conventional fuel injection pumps, the drive camshaft is fixed at the time of production.

The optimal injection time is usually set through experiments or statistics.

A diesel engine is an internal combustion engine that uses diesel as fuel. Diesel engines belong to compression-ignition engines, and they are often referred to as Diesel engines after the name of the main inventor, Diesel. When the diesel is working, the air in the cylinder of the diesel engine is sucked in, and it is compressed to a higher degree due to the movement of the piston, reaching a high temperature of 500 700.

Diesel engines can be classified according to different characteristics: according to the speed, it can be divided into high-speed, medium-speed and low-speed diesel engines; According to the type of combustion chamber, it is divided into direct injection type, vortex chamber type and pre-combustion chamber diesel engine; According to the cylinder intake mode, it is divided into supercharged and non-supercharged diesel engines; According to the mode of action of gas pressure, it is divided into single-acting, double-acting and opposing piston diesel engines.

According to the application, it is divided into marine diesel engine, locomotive diesel engine, etc. Diesel engine fuel is mainly diesel, usually high-speed diesel engine with light diesel; Light diesel oil or heavy diesel oil for medium and low-speed diesel engines. Diesel engines use fuel injection pumps and injectors to inject fuel into the cylinder at high pressure, and the injected fuel is misted and mixed with air for combustion.

Therefore, the diesel engine can use heavy fuel or inferior fuel with poor volatility, such as ** and residual oil. In addition to filtering out impurities and moisture, the oil supply system should be preheated and insulated to reduce the viscosity for conveying and spraying. Light fuels such as ethanol, gasoline and methanol can also be used in diesel engines with a suitable combustion chamber.

The working process of a diesel engine is actually the same as that of a gasoline engine, and each working cycle also goes through four strokes: air intake, compression, work and exhaust.

Inhalation is pure air. When the compression stroke is nearing the end, the diesel fuel is injected with the oil pressure to more than 10MPa, injected into the cylinder through the injector, and mixed with the compressed high-temperature air in a very short time to form a combustible mixture. Due to the high compression ratio of the diesel engine (generally 16-22), the air pressure in the cylinder can reach the end of compression, and the temperature is as high as 750-1000K, which greatly exceeds the auto-ignition temperature of diesel.

Therefore, after the diesel fuel is injected into the cylinder, it mixes with the air in a very short time and immediately ignites and burns on its own. The air pressure in the cylinder rises sharply to 6-9MPa, and the temperature also rises to 2000-2500K. Driven by high-pressure gas, the piston moves downward and drives the crankshaft to rotate and work, and the exhaust gas is also discharged into the atmosphere through the exhaust pipe.

The fuel supply system of ordinary diesel engine is driven by the engine camshaft, and the diesel fuel is delivered to the fuel chamber of each cylinder with the help of a high-pressure oil pump. This type of oil supply changes with the change of engine speed, and the optimal oil supply at various speeds cannot be achieved.

How four-stroke diesel engines work.

Like a gasoline engine, a four-stroke diesel engine is also composed of an intake stroke, a compression stroke, a power stroke and an exhaust stroke. Because the diesel engine uses diesel as fuel, compared with gasoline, the spontaneous combustion temperature of diesel fuel is low, the viscosity is large and it is not easy to evaporate, so the diesel engine adopts compression ignition ignition at the end of compression, also called compression ignition ignition, and its working process and system structure are different from those of gasoline engine.

1) Intake stroke.

The working fluid that enters the cylinder is pure air. Due to the less resistance of the diesel engine intake system, the pressure at the end of the intake air is pa= (, which is higher than that of the gasoline engine. The intake terminal temperature ta=300 340K, which is lower than that of a gasoline engine.

2) Compression stroke.

Since the compressed working fluid is pure air, the compression ratio of diesel engines is higher than that of gasoline engines (generally =16 22). The pressure at the end of compression is 3 000 5 000 kPa, and the temperature at the end of compression is 750 1 000 K, which greatly exceeds the autoignition temperature of diesel (about 520 K).

3) Do the power stroke.

When the compression stroke is nearing the end, under the action of the high-pressure oil pump, the diesel is sprayed into the cylinder combustion chamber through the injector at a high pressure of about 10MPa, and it is mixed with air in a very short time and immediately ignites and burns by itself. The pressure of the gas in the cylinder rises rapidly to a maximum of 5 000 9 000 kPa and a maximum temperature of 1 800 2 000 K. Because the diesel engine is self-ignited and burned by compression, the diesel engine is called a compression-ignition engine.

4) Exhaust stroke.

The exhaust of a diesel engine is basically the same as that of a gasoline engine, except that the exhaust temperature is lower than that of a gasoline engine. General TR = 700 900K. For single-cylinder engines, their rotational speed is uneven, the engine works unsmoothly, and the vibration is large.

This is because only one of the four strokes is work-done, and the other three are those that consume power in preparation for work. To solve this problem, the flywheel must have a large enough moment of inertia, which in turn leads to an increase in the mass and size of the entire engine. The use of multi-cylinder engines can compensate for the above shortcomings.

Modern automobiles mostly use four-, six- and eight-cylinder engines.

Unlike gasoline engines, diesel engines ignite the compressed mixture by a spark plug at the end of the compression stroke. At the end of the compression stroke of the diesel engine, the temperature in the cylinder has reached above the combustion temperature of the diesel, and the diesel is directly injected into the cylinder by the fuel injector, and the diesel is in contact with the high-temperature gas for combustion (the gas temperature is higher than the temperature of the diesel combustion point), so as to push the piston down to do work.

What I wrote in my book is that the diesel engine is compressed and self-combusting, and the gasoline engine is ignited by an electric spark plug.

Diesel engines are compressed and self-combusting.

There is no way to adjust the ignition time of a four-cylinder diesel engine.

In 1922, Bosch in Germany invented a mechanical injection device, which gradually replaced air injection. In the late 20s of the twentieth century, high-speed diesel engines appeared, and they began to be used in cars.

In the 50s, some new serialized and generalized diesel engines with more perfect structural performance developed, and since then diesel engines have entered the stage of specialized mass production. Especially after the adoption of exhaust gas turbocharging technology, diesel engines have become the most important part of modern power machinery.

Architectural diagram of diesel fuel internal components, power transmission components, body and main bearings, valves, fuel system and governor, lubrication system, cooling system, starting system internal combustion engine. Diesel fuel spontaneous combustion is characterized by low temperature, so instead of diesel, spark plugs, ignition devices, compressed air is used to raise the air temperature, diesel oxidation test air temperature, and then the air mixture of diesel spray spontaneous combustion is injected into combustion.

The diesel pump will be sent to the filter filter pump to ensure sufficient fuel and maintain a certain pressure, the fuel supply of the fuel transfer pump is much larger than the fuel injection pump's demand, the excess diesel fuel is returned to the fuel tank through the low pressure pipe, and the rest of the diesel fuel is compressed to high pressure by the fuel injection pump. Compression ignition cylinder directly into the combustion chamber.

There is no way to adjust the ignition time of the four-cylinder diesel engine, and the diesel engine is ignited:

1. In thermodynamics, a compression-ignition engine is similar to a spark-ignition engine. The cycles of both engines include suction, compression, heating, expansion, and exhaust.

Second, the combustion process and power control method of compression-ignition engine are different from those of EDM ignition engine. Compression-ignition engines, usually with a compression ratio of between 12 and 20 during the inhalation of the air.

Third, so the temperature of the air becomes very high during the combustion process. In a compression-ignition engine, air is compressed to a very high temperature with a high compression ratio, and then liquid fuel is injected into the engine. The high temperature of the air sets the fuel on fire.

If you put a four-cylinder engine at 10 o'clock, the valve of the first cylinder has a gap, the valve of the four-cylinder has no clearance at all, you can adjust the two valves of the first cylinder, the intake valve of the second cylinder, the exhaust valve of the third cylinder, the gap between the two valves of the four-cylinder can be adjusted when there is no clearance between the two valves of the four-cylinder, the exhaust valve of the two-cylinder, and the intake valve of the three-cylinder.

It is to adjust the oil supply advance angle, the specific method is to loosen the high-pressure oil pipe of a cylinder, rotate the crankshaft, when a cylinder of high-pressure oil pipe has the pulsation of oil, it is the starting point of oil pump oil supply, check the degree of the engraved position on the flywheel at this time relative to the top dead center of a cylinder, this degree is the oil supply advance angle. If the requirements are not met, loosen the fixing bolt of the oil pump and turn the position of the high-pressure oil pump to change this degree.

The ignition time of the diesel engine is not used and cannot be adjusted, and the fuel of the diesel engine is sprayed into the combustion chamber in the form of a high-pressure mist and burns itself at high temperature and high pressure. If you want to adjust, it is the advance angle of oil supply, which is to observe the angle of the crankshaft when the oil is discharged from the high-pressure oil pipe relative to the top dead center of the cylinder compression by rotating the angle of the high-pressure oil pump.

Adjust the feed advance angle of a cylinder.

Diesel engines do not have an ignition system, so there is no ignition process. Diesel engine.

The working process is actually the same as that of a gasoline engine.

In the same way, each duty cycle also goes through four strokes: air intake, compression, work and exhaust.

1. The cylinder liner has cracks or the cylinder gasket is damaged, along with the cooling water.

As the temperature and pressure rise, the cooling water enters the cylinder. Water mist or water vapor can easily form when venting.

2. The atomization of the injector is poor, the injection pressure is too low, and there is a dripping phenomenon. In the cylinder, the fuel mixture is uneven, the combustion is incomplete, a large number of unburned hydrocarbons are produced, and water mist or water vapor is easy to form when exhausting.

3. The oil supply advance angle is too small. Too little fuel is injected into the cylinder before the piston goes up to the cylinder top, forming a thinner combustible mixture, and the late injection reduces the amount of premixed fuel, and the amount of premixed mountain is reduced. The pre-mixed gas reduces the blind eggplant, reduces the combustion rate, and the combustion ends late, forming a large amount of water vapor smoke from combustion.

4. There is water and air in the fuel. Water and air are injected into the cylinder with the fuel to form an uneven fuel mixture, which is incompletely combusted, and a large amount of unburned hydrocarbons are discharged out of the machine.

5. Serious wear of pistons, cylinder liners, etc., causes insufficient compression force, resulting in incomplete combustion.

6. When the diesel engine is just started, there is no combustion in individual cylinders (especially in winter), and the unburned fuel mixture is discharged with the exhaust gas of other working cylinders to form water vapor smoke.

Gasoline has a high spontaneous ignition temperature and uses spark plugs.

Forced ignition, gasoline engine.

It is a ignition engine. Hence the gasoline engine.

Ignition system Diesel has a low autoignition temperature and a high compression ratio.

Compression-ignition, diesel engine.

It is a compression-ignition engine. Therefore, the diesel engine does not have an ignition system.

Gasoline engine: suction stroke.

Inhale gasoline empty.

Gas mixture. Compression stroke:

The mixture is pressed.

shrink to 11-18 bar, temperature.

Work stroke: through spark plugs.

Ignite the mixture.

Exhaust stroke. Exhaust burned out.

of gases. Diesel engine.

Inspiratory stroke. Inhale air.

Compression stroke: The air is compressed. Reach.

bar, temperature 700-900

Power stroke: Diesel injection is high.

degree of compression of emptiness.

In the air, it is produced from.

Burn. Exhaust stroke.

Exhaust burned out.

of gases. Gasoline engines by changing the throttle.

The opening of the mixture controls the amount of gas entering the cylinder to achieve the output of different powers; The diesel engine control power output completely depends on the amount of fuel injection, which is the real sense of the throttle, canceling the throttle, starting the state reed machine intake is more sufficient, and the combustion is more sufficient, which is also one of the reasons for the high thermal efficiency of the diesel engine.

After the gasoline engine is ignited, it burns instantly, bursts out energy, and outputs high power at high speed, so it can have high performance and faster response speed with small volume and light weight. However, the compression ratio of the gasoline engine is often only half of that of the diesel engine, and the temperature and pressure in the cylinder are much lower than that of the diesel engine when doing the power stroke, so the thermal efficiency is relatively low, which is commonly known as "fuel consumption".

After the diesel engine is injected with fuel, it takes a certain amount of time to burn, so it is suitable to let the fuel fully burn at a lower speed to bring high torque, and in order to resist the high pressure and high torque in the cylinder, the cylinder and piston connecting rod and other parts of the diesel engine are stronger than the gasoline engine, so they are more bulky than the gasoline engine. But it is also the diesel engine because of the characteristics of high compression ratio and low speed, which can better convert heat into kinetic energy, so the diesel engine has better thermal efficiency, that is, better fuel consumption performance. This is the reason why gasoline engines are usually used in cars and racing cars, while diesel engines are used in large vehicles such as buses and trucks.