1882, Rudolf Dissel put forward the working principle of diesel engine.
1896 built the first four-stroke diesel engine. 100 years, diesel engine technology has been fully developed and its application fields are more extensive. A large number of research results show that diesel engine is the one with the highest thermal efficiency, the best energy utilization rate and the most energy saving among all kinds of power machinery being industrialized at present. Equipped with the most advanced technology, the diesel engine can reach 30 ~ 50 kWh/L, the torque reserve coefficient can reach above 0.35, the minimum fuel consumption can reach 198g/kWh, and the rated power fuel consumption can reach 204g/kWh. Diesel engines are widely used in many fields, such as ship power, power generation, irrigation, vehicle power and so on. , especially in terms of vehicle power. The global trend of "diesel" of automobile power has been formed. In the United States, Japan and Europe, 100% of heavy vehicles use diesel engines. In Europe, 90% of commercial vehicles and 33% of cars are diesel vehicles. In the United States, 90% of commercial vehicles are diesel vehicles. In Japan, 38% of commercial vehicles are diesel vehicles, and 9.2% of cars are diesel vehicles. According to experts' prediction, diesel engine will become the mainstream of automobile power in the world in the next 20 years or even longer. The governments of developed countries in the world automobile industry also attach great importance to the development of diesel engines, and take measures to promote the popularization and development of diesel engines from the aspects of taxation and fuel supply.
First, the present situation and development of foreign diesel engine technology
Modern adjustable high-performance diesel engines have higher thermal efficiency and less pollutant emissions than gasoline engines.
As automobile power, it is widely used. Western European countries use diesel engines not only for trucks and buses, but also for cars. Recently,
The US Federal Department of Energy, represented by the three major American automobile companies, and the Council of American Automobile Research Institute are developing a new generation of economical cars, which also use diesel engines as power configuration. After years of research and the application of a large number of new technologies, the biggest problem of diesel engine-smoke and noise has made a major breakthrough, reaching the level of gasoline engine.
The following are some advanced technologies adopted by foreign diesel engines:
(A) * * * track and four-valve technology
At present, the combination of * * rail new technology, four-valve technology and turbocharged intercooling technology is widely used in foreign diesel engines.
The engine has achieved good results in performance and emission limits, which can meet the requirements of Euro 3 emission limits regulations. The four-valve structure (two in and two out) can not only improve the charging efficiency, but also because the injector can be arranged in the center.
The uniform distribution of porous oil bundles can create conditions for good mixing of fuel and air; At the same time, the air inlet can be designed as two independent structures with the same shape on the four-valve cylinder head to realize variable vortex.
The synergistic effect of these factors can greatly improve the formation quality of mixed gas, effectively reduce the emissions of soot particles, HC and NOX, and improve thermal efficiency.
(2) High pressure injection and electronic control injection technology.
High pressure injection and electronically controlled injection technology are one of the important measures to reduce diesel engine emissions abroad.
The effective application of high-pressure injection and electronic control injection technology can fully atomize the fuel and realize the best mixing of fuel and air in each cylinder, thus reducing emissions and improving the performance of the whole vehicle.
(3) supercharging and intercooling technology
Turbocharging is used to increase the air volume of diesel engine and increase the excess air coefficient of combustion in order to reduce the exhaust smoke and PM under heavy load.
Effective measures for emissions and fuel consumption. Effective air-to-air cooling system can reduce the temperature of pressurized air to below 50℃, and the reduction of working cycle temperature is helpful to reduce NOX emission and PM. Therefore, at present, diesel engines of heavy vehicles are generally supercharged and intercooled, which not only helps to reduce emissions but also has good fuel economy. In addition, the application of turbine exhaust bypass valve can not only reduce the emission of PM and CO,
It can also improve the transient performance and low-speed torque of turbocharged diesel engine.
Application of EGR technology
EGR is a widely used technology for advanced internal combustion engines in developed countries. Its working principle is to introduce a small amount of exhaust gas into the cylinder, and the exhaust gas is nonflammable CO2.
Moreover, the steam exhaust gas has a large heat capacity, which can increase the ignition delay period, slow down the combustion rate, reduce the highest combustion temperature in the cylinder and destroy NOX.
The generating conditions of. EGR technology can obviously reduce the NOX emission of motor vehicles, but for heavy-duty diesel engines, intercooled EGR technology is the first choice at present, because it can not only obviously reduce NOX,
But also can keep the low level of other pollutants.
(v) aftertreatment technology
The goal of diesel engine aftertreatment is to further improve PM and NOX emissions. At present, it is mainly to install oxidation catalyst and develop NOX.
Catalytic converter and particle trap with good regeneration ability.
(6) Diesel oil
The production and storage conditions of diesel oil are an important guarantee to ensure the normal operation of diesel engines (vehicles), prolong their service life and maintain low emissions. For example, the use of first-class diesel in Sweden can reduce CO emissions by 54%, HC and
NOX emission reached 10%, and PM emission decreased 14% ~ 47%. Fuel detergent has been widely used in developed countries, which can not only save fuel, but also remove carbon deposits and reduce emissions.
(VII) Application of emulsified diesel oil
Diesel oil is mixed with emulsifier by adding water to form relatively stable water-containing emulsified diesel oil.
The use of this improved fuel can obviously reduce the emissions of diesel engines (vehicles), especially NOX and PM. At present, the United States has made great progress in this field, and China has also conducted research in this field, and has made gratifying progress. Adding 20% emulsified diesel oil (without layering for 70 days), under the load of 100% on a large diesel engine, the power is not reduced, the fuel saving is obvious, the power output is 4.3% higher than that of diesel oil, and the smoke and NOX emission are obviously reduced. However, although this technology is beneficial to low emission, its potential problems are such as water freezing,
Problems such as water corrosion to the engine have yet to be solved.
(8) Reduce oil consumption
A considerable part of particulate matter emitted by diesel engines comes from the combustion of heavy fraction engine oil.
In order to meet the increasingly stringent requirements of diesel engine (automobile) emission limit standards, it is necessary to minimize the combustion of engine oil, that is, to minimize the consumption of engine oil on the premise of ensuring the normal operation of the engine. In order to reduce the fuel consumption of diesel engines,
This is very important to optimize the design and manufacture of piston rings and the scientific configuration between cylinder liners.