The ban on diesel vehicles in many major cities in China is closely related to the lack of understanding of diesel engines by most people. More people think that diesel vehicles are high-power, high-power, high-power, high-power, high-power, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered, high-powered vehicles. representative. Technological development and urban environmental construction require that everyone must re-recognize diesel engine technology. The development of technology has made diesel a cleaner energy than gasoline.
In the past, diesel engines did have the above-mentioned shortcomings, so they were rarely used in civilian vehicles, especially in the car sector, and almost all of them were gasoline engines. Heavy-duty, noisy and noisy diesel engines are used in trucks, machinery and purebred off-road vehicles. But with the advancement of diesel engine technology, many of the performance indicators of the new diesel engine are now comparable (or even surpassed) to gasoline engines, and its unparalleled fuel economy is far superior to gasoline engines. As a result, more and more new diesel engines are beginning to be used in cars. TDI is the abbreviation of English "TurboDirectInjection", which means "electric control common rail diesel direct injection turbocharged engine". TDI solves many of the problems of older diesel engines by using electronically controlled common rail direct injection and turbocharging technology. This article takes Volkswagen TDI diesel engine as an example to show the development trend of new diesel engines.
After more than ten years of development, Volkswagen has been relatively mature in TDI technology. In the past, diesel engines have various shortcomings, mainly related to the characteristics of diesel engines and diesel characteristics. It is well known that compressed air releases heat. In order to reduce the internal heat of the cylinder and prevent the premixed gas from premature spontaneous combustion, adding turbocharger can effectively reduce the compression ratio of the engine. This reduces some of the vibration and noise and also increases engine power.
If turbocharging technology has long been used on diesel engines, it is nothing new, and electronically controlled common rail direct injection is an essential improvement to the old diesel engine.
The so-called direct injection is to directly inject diesel into the combustion chamber through the high-pressure injection device. Because the top of the piston is designed in a concave shape, the diesel and air will form a spiral vortex mixed gas in the cylinder, which makes diesel and air. The mixing is more complete and the combustion is more complete, thereby increasing the output of the diesel engine and reducing fuel consumption.
Many diesel engines use direct injection, but TDI is controlled differently. TDI uses a high-pressure common rail electronically controlled injection system, and its concept is similar to that of a gasoline engine.
In general, the injection system of a diesel engine is controlled by various mechanical sub-pumps after the main pump is boosted. This mechanical injection is difficult to achieve precise control. The TDI engine controls the high-pressure injection of diesel through a solenoid valve – enabling more precise and closed-loop control. Therefore, the TDI engine can reduce the abnormal deflagration and knocking while improving the combustion accuracy, thereby reducing the engine vibration and noise, and the injection pressure is greatly improved by the electric pump, which is more conducive to the full mixing of the fuel. Speaking of the careful readers here, we will find that there is no sub-pump in the high-pressure common rail of TDI. As mentioned above, the sub-pump is also the "culprit" of vibration and noise. Since the TDI engine replaces the sub-pump with a common rail and a solenoid valve, vibration and noise are reduced at the source.
The electronic fuel injection closed-loop control used by TDI is also different from the purely mechanical open-loop control of ordinary diesel engines. In this way, various sensor devices similar to gasoline engines can be arranged on the engine, which further optimizes the control of diesel injection time and injection amount, and reduces CO, HC and carbon particle emissions (of course, effective for carbon particle treatment) Reduced, but still not fully controlled, also need to install a filter for carbon filtration, this filter needs to be replaced regularly during maintenance). At present, one out of every two Volkswagens in Europe is a TDI model, and the sales of diesel vehicles are more than 40%.
TDI is just one of the new diesel engines. In fact, many European manufacturers are committed to the development and production of car diesel engines. In France, the PSA Group's diesel engine is significantly more famous than its gasoline engine, and many new models (such as the 4007) do not even have a gasoline engine to choose from. The other two German auto giants Mercedes-Benz and BMW are also doing the same work. Many Mercedes-Benz and BMW models have only a diesel version.
(Source: China Industry News)
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