What is the current development trend of engines?

The rapid growth of automobile production and sales is accompanied by air pollution and oil consumption. At present, China has become the third largest oil importer after the United States and Japan. The oil consumption of automobiles accounts for 50% of China's annual oil consumption. Undoubtedly, advanced engine technology plays a key and decisive role in the development of automobile energy-saving and environmental protection technology. Since the end of the 20th century, automobile emission regulations have become stricter and stricter. Compared with the federal emission regulations implemented in the United States in the mid-1990s, the new federal emission regulations fully implemented in 2007 will require the emission of nitrogen oxides from automobiles to be reduced by up to 95% and the emission of hydrocarbons to be reduced by up to 84%. At the same time, the durability requirements of emission-related systems and components reach 6.5438+0.2 million miles. In 2007, the hydrocarbon emission limit of the fifth group in the American federal emission standard was about half of the Euro IV emission limit (due to the inconsistent test cycle, the actual emission requirement was lower than half of the Euro IV emission). This increasingly stringent emission regulations and people's deeper understanding of energy saving make the development of high-efficiency and low-emission vehicle engine technology highly valued, thus promoting the continuous innovation of traditional internal combustion engine technology. Such as gasoline engine direct injection technology, variable valve timing technology, variable intake pipe, combustion rate control slider, variable displacement technology, high pressure rail direct injection diesel engine and so on. Due to the different national conditions, the technologies that focus on environmental protection and energy saving are also different. Due to the factors of land and resources in Japan, the proportion of mini-cars and economical cars is relatively high, so small-displacement engines can not only meet the requirements of energy conservation and environmental protection, but also provide sufficient driving force for such cars; In Europe, because diesel is cheap and its thermal efficiency is much higher than that of gasoline engine, consumers can easily accept the fact that diesel-driven cars are more expensive than similar cars driven by gasoline engine 1000 ~ 2000 USD. In addition, the low-speed torque of diesel engine is far better than that of gasoline engine, which also makes Europeans who prefer car sports feel regard direct injection diesel engine as a representative of high technology. Now in Western Europe, more than 35% of new car sales are diesel engines. While developing new technologies of engine energy saving and environmental protection, people can't ignore the great influence of fuel characteristics on the popularization of engine technology. The purification of automobile exhaust completely depends on the catalytic aftertreatment device, and the sulfur content in fuel is the "nemesis" of the catalytic aftertreatment device. The sulfur in the fuel is oxidized into sulfur dioxide after combustion in the cylinder, and the sulfur dioxide reacts with the catalyst in the carrier coating, which greatly reduces the conversion efficiency of the catalyst. According to the regulation of fuel sulfur content, the sulfur content of European diesel engines is below 50ppm, while the federal limit in the United States is currently 300ppm, which will be reduced to 80ppm by 2007. European low sulfur diesel fuel has created conditions for the wide application of diesel engines. In the United States, with the reduction of sulfur content, the conditions for the application of direct injection diesel engines in light vehicles are becoming more and more mature, and multinational automobile companies are developing high-speed direct injection diesel engines for the North American market in order to put them into the market after 2007. Direct injection (GDI) technology of gasoline engine means that gasoline is directly injected into the combustion chamber through a high-pressure (about 100 atmospheric pressure) fuel supply system to mix with air for combustion. After the rapid development of electronic injection and control technology, GDI entered the market in the late 1990s. Compared with the traditional multi-point injection gasoline engine, GDI has four obvious advantages: it can effectively reduce the unburned hydrocarbon emission of the engine, because GDI technology avoids the problem of fuel deposition on the intake wall during cold start, greatly improves the mixing degree of fuel and air, and controls the air-fuel ratio of each combustion cycle more accurately, thus achieving the goal of complete combustion in the cylinder; Gasoline is atomized and evaporated in the combustion chamber, which reduces the temperature of the air in the combustion chamber, thus increasing the quality of the air in the combustion chamber; Because gasoline evaporation reduces the charging temperature, it is possible for engine designers to improve the compression ratio and thermal efficiency of the engine. GDI makes it easy for the engine to achieve stratified combustion. Variable valve timing technology (VVT) is another milestone in the development of gasoline engine technology. VVT means that engine valve lift and valve timing can be adjusted in real time according to engine working conditions. This technology makes it unnecessary for engine designers to choose between low-speed torque and high-speed power, and real-time valve timing adjustment makes it possible to take both low-speed torque and high-speed power into consideration. Continuously variable valve timing technology combined with advanced engine control strategy can skillfully realize variable compression ratio. For example, under heavy load, the engine is prone to knock caused by spontaneous combustion, and the effective compression ratio can be reduced by delaying the closing time of the intake valve, thus avoiding knocking. Under medium and small load, knocking is no longer a problem, and the effective compression ratio can be improved by adjusting the valve closing time, so that the engine has excellent thermal efficiency under medium and small load. Variable valve technology can also make the emission quality of gasoline engine reach a better level. Burning rate control blade is another energy-saving and environmental protection technology, and similar design ideas are reflected in Toyota and Ford engines. When the gasoline engine is idling and under light load, the proportion of residual exhaust gas in the combustion chamber is very high, which will lead to ignition difficulties and slow flame propagation, which will have a negative impact on the engine's emission and efficiency. On the other hand, in general urban traffic, the automobile engine is in a state of medium and small load and idle speed most of the time. Under this condition, it is of great significance to optimize the emission and thermal efficiency of gasoline engines. The purpose of combustion rate control blades is to create a stable and easily ignited air-fuel ratio near the spark plug in the combustion chamber, and to achieve the purpose of energy saving and environmental protection by increasing the turbulence intensity in the combustion chamber. When the engine is idling or under light load, the electronic controller of the engine will adjust the position of the blade in the engine inlet in real time, so that the blade blocks part of the cross-sectional area of the inlet, so that the fresh air-fuel mixture has tangential velocity when entering the combustion chamber, and an orderly vortex is formed in the combustion chamber. At the beginning of ignition and combustion, the ordered vortex is broken into small-scale vortex, which greatly improves the flame propagation speed. Another gasoline engine technology put into the market in recent two years is cylinder-cutting cycle, or variable displacement. Variable displacement technology is to determine the effective displacement of the engine in real time according to the demand of automobile power, so that the cylinder doing work is always in a heavy load state, thus achieving the purpose of energy saving and environmental protection. This technology is suitable for engines with medium and large displacement and V-shaped layout, such as Honda V6, General V8 and Dyke V 12 gasoline engines.