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Introduction The advantages of diesel engines are their high power and economic performance. The working process of a diesel engine is similar to that of a gasoline engine. Each working cycle also undergoes four strokes of intake, compression, work, and exhaust. However, because the diesel engine fuel is diesel, its viscosity is higher than that of gasoline, it is not easy to evaporate, and its auto-ignition temperature is lower than that of gasoline. Therefore, the formation of the combustible mixture and ignition methods are different from that of the gasoline engine. The main difference is that the mixture in the diesel engine cylinder is ignited, not ignited. When the diesel engine is working, the air entering the cylinder is air. When the air in the cylinder is compressed to the end point, the temperature can reach 500-700°C and the pressure can reach 40-50 atmospheres. When the piston approaches top dead center, the engine's high-pressure pump injects diesel fuel into the cylinder with high pressure. The diesel oil forms tiny oil particles. It mixes with the high-pressure and high-temperature air. The diesel fuel mixture burns on itself and expands violently to generate explosive force and push the piston to do work. At this time, the temperature can reach 1900-2000°C and the pressure can reach 60-100 atmospheres. The generated power is large, so diesel engines are widely used in large-scale diesel vehicles.
The advantage of diesel engines in terms of energy saving and carbon dioxide emission is that all heat engines, including gasoline engines, cannot be replaced. Therefore, the advanced small-scale high-speed diesel engines have already reached the Euro III standard and become “green enginesâ€. At present, it has become a power device for many new cars in Europe and America.
Features: The characteristics of traditional diesel engines: good thermal efficiency and economy, diesel engine uses compressed air to increase the air temperature, so that the air temperature exceeds the spontaneous combustion of diesel fuel, then spray into the diesel, diesel spray and air mixture while ignition . Therefore, diesel engines do not need an ignition system. At the same time, the diesel engine's fuel supply system is relatively simple, so the reliability of the diesel engine is better than that of the gasoline engine. Due to the non-detonation limit and the need for diesel self-ignition, the diesel engine has a high compression ratio. The thermal efficiency and economy are better than those of the gasoline engine. At the same time, the diesel engine has large torque and low rotational speed at the maximum power, which is suitable for the use of trucks.
However, due to the high working pressure of the diesel engine, the relevant parts are required to have high structural strength and stiffness, so the diesel engine is relatively bulky and bulky; the diesel engine's fuel injection pump and nozzle have high requirements for manufacturing precision, so the cost is higher; in addition, the diesel engine is working rough , Vibration and noise; Diesel is not easy to evaporate, cold start in winter is difficult. Due to the above characteristics, diesel engines were previously commonly used on large and medium-sized trucks. New developments in small, high-speed diesel engines: Emissions have reached the European Standard III. Traditionally, diesel engines have been seldom favored by cars due to their heavy weight, lower power ratings than gasoline engines (lower rotational speeds), higher noise and vibration, and relatively more soot and particulate (PM) emissions. However, with the advancement of diesel technology in recent years, especially the new development of small-scale high-speed diesel engines, a number of advanced technologies, such as electronically controlled direct injection, common rail, turbocharged, and intercooled technologies, can be applied to small diesel engines. Therefore, the disadvantages of the original diesel engine have been better solved, and the advantages of the diesel engine in terms of energy saving and CO2 emission are that all the heat engines including the gasoline engine cannot be replaced. Therefore, the advanced small-scale high-speed diesel engine Emissions have reached the European standard of No. III and become a "green engine". Now it has become the power plant for many new cars in Europe and America. It can be foreseen that more and more diesel cars will appear in China.
Differences Gasoline engines typically inject gasoline into the intake manifold and mix with the air to form a combustible mixture that re-enters the cylinder, where it is ignited and expanded by the spark plug to do work. People usually call it a ignited engine. The diesel engine generally injects diesel fuel directly into the engine cylinder through a fuel injection pump and a fuel injection nozzle, uniformly mixes the compressed air in the cylinder, and spontaneously ignites under high temperature and high pressure, thereby promoting the piston to perform work. This type of engine is commonly referred to as a compression ignition engine.
Gasoline engine cars have high rotation speeds (gasoline engine speed can be as high as 5000-6000 rev / min, trucks gasoline engine up to 4000 rev / min or so), light weight, small noise at work, easy start, low manufacturing and maintenance costs, so in It is widely used in cars, medium and small trucks and military off-road vehicles. The shortcomings are high fuel consumption and poor fuel economy. Due to the high compression ratio and lower fuel consumption, the diesel engine is on average about 30% lower than that of a gasoline engine, so the fuel economy is better. For example, the recently launched TDI1 produced by FAW-Volkswagen Automotive Co., Ltd. can save 2 liters of oil per 100 kilometers compared with a 1.6-liter petrol sedan. Most of the general trucks use diesel engines. The weakness of diesel engines is that the speed is lower than that of gasoline engines (generally the maximum speed is around 2500-3000 rev/min), the quality is high, and the manufacturing and maintenance costs are high (because the injection pump and the injectors require high machining accuracy). However, these weaknesses in diesel engines are gradually being overcome and their scope of application is being extended to medium- and light-duty trucks. Foreign diesel cars also have rapid development, and their maximum speed can reach 5000 rpm.
Generally speaking, the thermal efficiency of diesel engines is 30% higher than that of gasoline engines. Therefore, from the perspective of energy conservation and fuel cost reduction, the promotion of diesel engine cars is of great significance. Compared with gasoline engines, diesel engines have high power, long life, and good dynamic performance. They emit 45% lower greenhouse effect than gasoline, and emit low levels of carbon monoxide and hydrocarbons. During the service life of complete vehicles, nitrogen oxides The emissions are slightly larger than the gasoline engine. The disadvantage of diesel engines is the large emission of harmful particulates. In recent years, diesel engines have adopted advanced technologies such as turbocharging, intercooling, direct injection, exhaust gas catalytic conversion, and particulate traps. The emissions of diesel engine vehicles have reached Euro III and Euro IV emission standards. In Europe, diesel cars are more popular. With the strict requirements for the sustainable development of environmental protection and energy conservation, the future of automobiles, especially diesel cars, will be a development trend. At present, China FAW-Volkswagen has developed Jetta, Bora diesel cars, and has been listed in some domestic cities.
The ability of a car to complete a unit's transportation work with a minimum amount of fuel under certain conditions of use is called the fuel economy of the car. The fuel economy of automobiles is one of the main uses of automobiles. In general, fuel consumption accounts for about 37% of the cost of running a car. The main factors influencing the fuel economy of automobiles are: from the perspective of the automobile itself, it is necessary to first increase the thermal efficiency of the engine, the intake efficiency, and reduce the friction loss. Second, it is necessary to reduce the weight of the vehicle body, reduce the air resistance, and reduce the rolling resistance of the wheels. Third, improve transmission efficiency and reasonably match transmission ratios. In terms of usage, different grades of roads can run on different fuels. Traffic jams and severe congestion are completely different from the smooth fuel consumption. Wind, rain, and climate change have an impact on the fuel consumption of cars. Driver's technology also plays an important role in fuel consumption. There are many factors that affect the fuel economy of automotive fuel. The most important one is the automobile engine itself.
Automotive Knowledge Base for Diesel Engines
A diesel engine is an engine that burns diesel fuel for energy release. It was invented by the German inventor Rudolf Diesel in 1892. To commemorate this inventor, diesel was represented by his last name Diesel, and the diesel engine was also called the diesel engine.