With the increasingly stringent requirements on energy and environmental protection, the engines must also evolve and evolve in order to meet people's needs. Nowadays, the words 'direct injection in cylinders', 'stratified combustion' and 'variable displacement' Is not strange, in the end how they work? Now let's understand it.
Pistons, crankshaft is the most tired?
To start a run, the piston 'head' will have to withstand high temperature and pressure, constantly doing high-speed up and down movement, the working environment is very harsh.Can say the piston is the engine 'heart', so the piston material production accuracy is very high Request.
The piston is not under the foot of the crankshaft is not good, to keep doing high-speed rotary motion crankshaft to rotate thousands of times per minute, shoulders the drive oil pump, generator, air conditioner compressor, camshaft and other agencies Arduous task, is the engine shaft of rotation, so it is also more 'strong.'
Linear motion how to change rotation?
We all know that the cylinder piston is up and down the linear motion, but the output drive wheel forward rotation force, is how the linear motion into rotary motion? In fact, this structure and the crankshaft has a great relationship. Connecting rod axis and the spindle are not in the same line, but the opposite arrangement.
The principle of this exercise is actually very similar to our bike, our two feet is equivalent to two adjacent pistons, pedals equivalent to the connecting rod shaft, and the middle of the flywheel is the crankshaft of the main axis of our left foot down When the piston is doing work or breathing in and out, the right foot will be raised (the other piston will compress or exhaust to move upwards), so the cycle moves into linear motion.
Why is the engine flywheel so big?
We all know that the piston stroke, only one time is doing work, intake, compression, exhaust stroke three trip requires a certain amount of power to support the smooth progress of the flywheel in the process to help a lot of favor.
The reason why the flywheel is bigger is mainly to store the kinetic energy of the engine so as to ensure the smooth operation of the crankshaft.In fact, this principle is similar to that of our childhood top toy, and after we forcefully rotate it, it can keep rotating for a long time.
Engine displacement, compression ratio
The volume of space through which the piston moves from top dead center to bottom dead center is referred to as cylinder displacement; the sum of all cylinder displacements of the engine is called the engine displacement and is usually expressed in liters (L) .As we usually see the car Displacement, 1.6L, 2.0L, 2.4L, etc. In fact, the cylinder volume is a cylinder, it is unlikely that exactly the entire number of ascent, such as 1998mL, 2397mL and other figures, can be approximately labeled as 2.0L, 2.4L.
The compression ratio, which is the extent to which the engine mixture is compressed, is expressed as the ratio of the total cylinder volume to the compressed cylinder volume (ie, the combustion chamber volume). Why compress the cylinder gas mixture? This will make the gas mixture easier, Faster, complete combustion, improving engine performance and efficiency.
What is variable displacement? How to change the displacement?
Usually in order to obtain a large power, you need to increase the engine displacement, such as 8-cylinder, 12-cylinder engine power is very strong, but the price is paid to increase fuel consumption.Especially in idling and other conditions do not require large power output, Fuel is wasted, and variable displacement can be a good solution to conflicts.
Variable displacement, as its name implies, is that the displacement of the engine is not fixed (that is, the number of cylinders involved in the work varies), but it can be changed according to operating conditions. Simply put, is through the control of the intake valve and the oil circuit to open or close the work of a cylinder.For example, a 6-cylinder variable displacement engine, according to the actual conditions needed to achieve 3-cylinder, 4-cylinder, 6-cylinder three modes of operation to reduce fuel consumption and improve fuel economy.
Such as Volkswagen TSIEA211 engine uses a variable displacement (cylinder shut-off) technology, mainly through the electromagnetic controller and mounted on the camshaft spiral groove sleeve to achieve valve closure and opening.
What is the direct injection cylinder? What are the advantages?
We know that the traditional engine is in the intake manifold fuel injection and then form a mixed gas with air before entering the cylinder in the process, because the fuel injector nozzle still a certain distance, a small oil The particles will adsorb on the pipe wall and the mixing of gasoline and air will be more affected by the intake air flow and valve closing.
In-cylinder direct injection directly injects the fuel into the cylinder and mixes it directly with the air in the cylinder. The ECU can precisely control the amount of fuel and injection and the injection time based on the amount of intake air. The high-pressure fuel injection system can be a Atomization and mixing more efficient, so that the theoretical air-fuel ratio of the combustion gas mixture more fully, thereby reducing fuel consumption and improve the engine's dynamic performance.
The so-called 'homogeneous combustion' can be understood as a common mode of combustion, that is, the fuel and air mixture to form a certain concentration of combustible gas mixture, the combustion chamber air-fuel ratio is the same, the spark ignition combustion.Because the mixture formation time Long, fuel and air can be fully mixed, more uniform combustion, resulting in greater output power.
The stratified combustion, the air-fuel ratio of the mixture inside the combustion chamber is different, the concentration of the mixture near the spark plug to be higher than in other places, so that the mixture around the spark plug he can quickly burn, which led to more distant The combustion of a lean mixture is called "stratified combustion." The purpose of homogeneous combustion is to achieve high power at high speeds and acceleration, and stratified combustion to save fuel at low speeds and loads.
How to achieve stratified combustion?
Such as TSI engine is how to achieve stratified combustion? First of all, the engine moves to the bottom dead center of the intake stroke, the ECU controls the nozzle to make a small amount of fuel injection, the cylinder to form a lean mixture.
In the end of the piston compression stroke when the second fuel injection, so that the formation of the mixture in the vicinity of the spark plug relatively high concentration region, and then use this part of the rich mixture of gas ignited lean mixture inside the cylinder, so as to achieve within the cylinder The lean burn, so you can use less fuel to achieve the same combustion, to further reduce the fuel consumption of the engine.
