If a little attention to the car engine friends must know that today's popular turbo engine, most of them are equipped with direct injection technology.But the major launch of turbocharged direct injection engine manufacturers, but also the name of ultra-high fuel Economical, dynamic significantly improve the energy-saving environmental protection under the banner, to promote its direct injection engine how powerful, but the fact is it? Direct injection engine really so good?
What is the in-cylinder direct injection engine?
To put it simply, the engine's nozzle is designed inside the cylinder (the manifold injects the engine, which is designed in the intake manifold, ie outside the cylinder's intake valve). When the piston in the cylinder goes down At run-time, the cylinder sucks in fresh air, and at this point, the injector will spray a small amount of fuel for the first time to mix it with the air, but because of this little fuel injection, Concentration, so when the piston runs up to the dead center, when the compressed air, the nozzle will once again fuel injection, the concentration of the mixed gas to be ignited conditions, when the ignition spark ignited the compressed gas mixture, resulting in explosion , To promote the piston down to work.
Do you think this method is faulty? If you follow the manifold EFI injection method, then the air and fuel have enough time to mix, reach the cylinder, you can mix evenly, so that the homogeneous combustion Why do you want to make a direct injection, is not this your pants fart?
No stratified combustion of direct injection, are playing rogue
The following will introduce a new concept, called stratified combustion, which is the core technology of direct injection engine, without it, all the advantages of direct injection engine will cease to exist.
As we all know, the most perfect internal combustion engine air-fuel ratio is 14.7: 1, that is, 14.7 copies of air, as long as a mixture of fuel, you can fuel-efficient at the same time. To achieve the best combustion state. Then igniting the mixture in the cylinder, It is required that the air-fuel ratio of the mixture gas in the entire cylinder be 14.7: 1, as long as the gas near the spark plug reaches this concentration. After the spark plug ignites the combustible gas in its vicinity, it ignites the leaner mixture in the periphery, This also can achieve the purpose of burning, explosion, doing work and the most edge of the mixture, air-fuel ratio of only 40: 1 or even 50: 1, we think, is not more than the overall 14.7: 1 homogeneous fuel-efficient? Fuel concentration is low, easier to be fully burned, reduce engine cylinder carbon deposition, emissions more environmentally friendly. And almost no need to worry about the engine knock, then the compression ratio can be increased accordingly, the overall increase in engine efficiency, it is not great.
Domestic direct injection, are playing rogue
We've all seen the 'TSI' written behind the butt of Volkswagen, which is 'Dual Boost + Stratified Combustion + In-Cylinder' (yes, T is dual booster, not turbo, which is also used by Volkswagen Castration technology, the previous 1.4T imported golf travel version, is dual boost: supercharged + turbocharged.) However, the domestic public, including Audi, and even direct injection engine manufacturers are castrated hierarchical Combustion is just the same homogeneous combustion as the manifold injection, so the so-called direct injection engine onboard our car has no eggs!
Hierarchical combustion is used in the engine under low-load, low-speed operation of the environment. At this time less intake, the temperature is not high, with only a small amount of oil to achieve complete combustion, in fact, very favorable for urban conditions. If stratified combustion is castrated, then homogeneous combustion is used in all operating conditions.
The intake air temperature of the engine, especially the turbocharged engine inlet air temperature, is very high, which seriously affects the combustion efficiency. When the injector injects the fuel, the colder fuel can cool the high temperature and pressure gas , But because the direct injection engine injects fuel into the cylinder and the mixing time is short, more oil must be sprayed to achieve the cooling effect, so this will make the concentration of the mixed gas in the cylinder too high, resulting in The result is more fuel-efficient, easier to make the piston carbon deposition, greater pollution.
Poor domestic oil, direct injection emissions are not up to standard
Although stratified combustion can achieve better fuel consumption and engine efficiency by burning a leaner mixture, it brings the problems of over-temperature in the cylinder and increased nitrogen oxides, and the current filtration speed of the three-way catalyst, Completely behind the speed of the formation of nitrogen oxides .At this time, engineers in the ternary behind the design of a storage of nitrogen oxides cans, non-hierarchical combustion conditions, that is, when the homogeneous combustion, and then Filter it out.
However, the storage tank is covered with a metal coating, which is used to convert the residual nitrogen oxides to nitrogen gas. However, if this coating encounters sulfur in gasoline, it will sulfidize the material and result in increased fuel consumption. And greatly reduce the conversion efficiency, so that emissions increase.It is so coincidentally, the domestic gasoline, just sulfur content is greatly exceeded ... So stratified combustion in the domestic implementation of the great restrictions on emissions, has become this now does not People do not look like a ghost
