The human heart has gone from "two chambers" to "one atrium and one ventricle", then to "two atriums and one ventricle", and finally perfected "two atriums and two ventricles", a process that has gone through hundreds of millions of years. But fortunately, with the wisdom and wisdom of mankind, the car gasoline engine has undergone three major changes in the course of a hundred years. The evolution of the carburettor>electrospray>direct injection has been concentrated in a hundred years.
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Carburetor engine: Heroes are late to exit the market in 2002
The carburetor was first born in 1892 and was invented by American Durier. With the evolution of technology, the carburetor function has become more complete. Until the middle and late of the last century, the carburetor has been divided into five parts: the main oil supply system, the starting system, the idle system, the heavy load enrichment system (economizer) and Accelerate the system. The role of the five parts is: according to the needs of the engine under different conditions, the gasoline is gasified, and mixed with the air into a combustible mixture in a certain proportion, and timely into the cylinder.
The advantages of the carburetor are: the ability to control the oil-gas ratio of the internal combustion engine to an ideal level, regardless of weather and temperature, forever a constant work. Moreover, the carburetor has low cost, high reliability, and easy maintenance and maintenance. Of course, there are also many weaknesses in the carburetor: for example, in cold start, idle speed, rapid acceleration or low-pressure environment, such a fixed oil supply method can not fully meet the operating requirements of the engine, and may even produce black smoke. Insufficient burning and insufficient horsepower. Therefore, since 2002, China has banned the sale of carburetor cars, and all models have since switched to EFI engines.
EFI engine: it is used in the main models of the single beam.
The EFI was first introduced in 1967, and the D-type electronic injection device developed by Porsche of Germany was subsequently used in Volkswagen and other German cars. This device takes the pressure inside the intake pipe as a parameter, but it still has the disadvantages of complicated structure, high cost and instability compared with the carburetor. In response to these shortcomings, Bosch has developed a kind of L-type electronically controlled gasoline injection device, which takes the air flow in the intake pipe as a parameter, and can directly determine the intake air amount according to the relationship between the intake flow rate and the engine speed. This jets out the corresponding gasoline. Due to its reasonable design and reliable operation, this device has been widely adopted by automobile manufacturing companies such as Europe and Japan, and has laid the prototype for today's electronically controlled fuel injection devices.
So far, the driving computer of the EFI system will detect engine temperature, intake air flow, speed change and vibration condition at any time, and adjust the fuel supply amount and ignition time according to actual needs, so it can be used in power output, fuel economy and sewage discharge performance. Made a fairly good balance. At the same time, in order to increase the engine intake and improve fuel efficiency, the engine evolved from an early single-point injection to multi-point injection, and the number of valves increased from two to five. At present, the most advanced is the EFI engine equipped with VVT variable valve technology.
In general, the biggest advantage of the EFI system is that the fuel supply control is very precise, so that the engine can have the correct air-fuel ratio under any condition, not only keeps the engine running smoothly, but also the exhaust gas can meet the requirements of environmental regulations. . However, the EFI oil supply system is not the most scientific. Due to the inherent limitations of the internal combustion engine configuration, the EFI nozzle is installed beside the valve, and the oil and gas injection can be completed only when the valve is opened. Therefore, the injection will be affected by the opening and closing cycle, causing a delay, thus affecting the computer's control of the injection time. Fortunately, this problem has been solved by the direct injection technology in the cylinder.
In-cylinder direct injection engine: the main direction of luxury cars in recent years
In the past two years, when European and American manufacturers realized that the research and development of EFI technology has entered a bottleneck period, the direct injection technology in the cylinder has become the main direction of major manufacturers. In-cylinder direct injection engines that are currently on the market include: Audi FSI in-cylinder direct injection engines, Cadillac SIDI dual-mode direct injection engines.
Compared with the EFI engine, the injector of the in-cylinder direct injection engine is moved to the inside of the cylinder, so the amount of oil and gas in the cylinder is not affected by the opening and closing of the valve, but the timing and weight of the injection are automatically determined directly by the computer. As for the valve, it only controls the entry time of the air, and the two are mixed when entering the cylinder. Since the mixing space and time of oil and gas are quite short, the direct injection system in the cylinder must rely on high pressure to press fuel from the injector into the cylinder to achieve a high atomization effect, thereby better mixing the oil and gas. Among the engines with higher compression ratio of mixed oil and gas, the stronger its power performance, the more obvious the corresponding energy-saving effect. The compression ratio of the Audi 3.2-liter FSI in-cylinder direct injection engine reached 10.3:1; the compression ratio of the Cadillac 3.6-liter SIDI dual-mode direct-injection engine reached 11.3:1. In addition, the combustion chamber and piston of the direct injection system in the cylinder also have special guide grooves for the gas turbine to generate cyclone vortex after entering the combustion chamber to improve the atomization effect and combustion efficiency of the mixed oil and gas.
In general, engines that use in-cylinder direct injection technology increase the peak power by 10% to 15% compared to the same-displacement multi-point injection engine, while peak torque can be increased by 5% to 10%. This kind of improvement can be described as a qualitative change, and it is difficult to achieve this effect by increasing the number of valves.
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