You may have heard the saying: "As many as two hundred cars are polluted by a big diesel truck." ”
Due to the pollution problem, many people compare the diesel engine to the "stupid big smoke", but this is not the original sin of the diesel engine, but is constrained by the backwardness of the mainland diesel technology. In the domestic market, many people only know the advantages of diesel engines, but do not understand their disadvantages: insufficient power, high fuel consumption, large exhaust emissions, etc. In fact, these shortcomings can not affect the power and economy of the diesel engine. In fact, advanced technology diesel engines, not only powerful, coupled with high-quality diesel, can meet the same emission standards as ordinary gasoline engines.
In terms of performance, diesel engines have more advantages, so why not upgrade backward diesel engine technology?
But the problem is that the core technology of the diesel engine has been firmly in the hands of foreign countries, and it is not easy to improve the technical level of the diesel engine, and many small partners want to know what advantages the diesel engine has compared with the gasoline engine.
What is so difficult about the core technology of the diesel engine?
In what ways should Chinese manufacturing break through in order to alleviate the pain point of "stuck neck"?
In this episode, we will explore the secrets of diesel engines
Tanks, locomotives, ships and even agricultural machinery rely on diesel engines, which have great advantages of high compression ratio, high torque and good fuel economy.
What is a high compression ratio?
It is fuel that uses the same calorific value, and the thermodynamic processes of the diesel engine can release more useful work, which makes the effective efficiency of the diesel engine nearly 10% higher than that of the gasoline engine, and this figure is not a difference of a dollar and a dime.
Add in fuel consumption, fuel prices and the number of cars, quite a lot.
Diesel and gasoline engines also have one thing in common, four-stroke operation, what is four-stroke?
That is to say, each work cycle has to go through the intake, compression, workmanship and exhaust stroke, first, the vehicle starts from the intake stroke, through the intake stroke, the piston that opens the intake valve moves downwards, the air is sucked into the cylinder to inject fuel, and then, when the valve is closed, the piston moves up, compressing the oil-gas mixture, and then performing another compression stroke.
The next step is to do the work stroke, when the composite gas ignites, forcing the piston back to the bottom of the cylinder.
Looking at the exhaust stroke, this section mainly studies the working process at different speeds; the fourth part: summarizes the content of this article and makes some suggestions. After summarizing this paper, the following conclusions have been drawn. Exhausted oil and gas through the exhaust valve from the cylinder discharge, in the case of the same workmanship process, the biggest difference is the combustion mode of air and the combustion mode of fuel, diesel engine naturally uses diesel, diesel viscosity is large, less flash point, not easy to volatilize, and the gas mixture in the cylinder is pressure combustion, the greater the pressure, the higher the temperature, so the diesel engine does not need the ignition system at all.
Gasoline engines, on the other hand, are ignited fuels that need to be ignited by electric sparks in the cylinder, which is why the compression ratio of diesel engines is higher than that of gasoline engines.
In fact, here, many friends think that the diesel engine is not difficult to operate in principle, if it is similar to the gasoline engine, why is the core technology of the diesel engine in the hands of others?
Of course, basic diesel engines are not difficult, but the first problem to be solved when diesel power generation is really launched is the pollution problem.
According to the "China Motor Vehicle Environmental Management Annual Report (2017)" released by the Ministry of Environmental Protection, nitrogen oxides emitted by diesel vehicles account for nearly 70% of total vehicle emissions, particulate matter accounts for more than 90% of total vehicle emissions, while the exhaust gas of mainland trucks accounts for only 5% of motor vehicle exhaust pollution.
In order to solve the problem of pollution, it is necessary to mention a system, that is, the electronically controlled diesel high-pressure common rail system.
The so-called high pressure, because the system makes the pressure of the fuel injection system is 3 times that of traditional diesel, the higher the pressure, the better the atomization effect, the more fuel burned, the more power is increased, and the purpose of fuel economy is finally achieved.
Common rail is the brain of the diesel engine, through the common fuel supply pipe simultaneously delivered to all the injectors, the same mass and pressure of fuel to make the diesel engine run more smoothly, reduce engine vibration and fuel consumption, so that the engine mixing is more uniform, combustion more fully.
As a result, not only pollution is reduced, but also motivation and economy are improved.
Although the structure of high-pressure common rail is simple and practical, it is difficult to solve a series of world-class problems such as high combustion efficiency, low heat transfer, high reliability and low friction loss of diesel engines using high pressure common rail.
For many years, the technology has been in the hands of Germany, the United States and Japan, with Bosch AG accounting for 85% of the market share.
Can we rely on imports?
The answer is, no
As diesel engines began to replace gasoline engines in large numbers, the range of use of diesel engines expanded from tractors to military equipment such as armored vehicles and tanks. As one of the world's largest producers and consumers of diesel engines, China has become the world's largest producer of diesel engines. At present, the mainland already has a number of well-known multinational groups, including Cummins and Bosch. It can be said that the development of the diesel engine industry, from agriculture to national defense, is of great significance to China.
It is no exaggeration to say that in the current international situation, if we do not have our own high-pressure common rail system, the development of high-voltage common rail system will sooner or later be the only way.
So, how does China achieve overtaking in curves?
This can be traced back to non-road vehicles such as excavators and tractors, because the profit is not as high as in the automobile market, and foreign brands such as Bosch do not focus on this, which gives independent companies the opportunity to develop technology and occupy the market.
The first thing to mention is the Wuxi Wuxi Oil Pump Nozzle Research Institute established in 1980, we refer to as the Oil-Free Institute, the development of this system in front of you two problems, one is the control system problem, the other is the manufacturing system problem, the latter is a global manufacturing problem.
In the global manufacturing industry, the accuracy requirements of electronically controlled common rail systems are the highest in the entire industry, for example, electronically controlled common rail systems have only a few couplings, but can withstand more than 2000 kg of pressure, flexible movement, no leakage, and a gap of only 2-3 microns.
In order to develop the technology, the oil-free supervisor visited bosch's factory, but bosch demonstrated a production line that used a lot of automation equipment and could only see robots repeating their actions. To put it bluntly, this display is not only meaningless, but also keeps China in the dark.
However, the technicians of the oil-free institute were not intimidated and began to train professionals to hone their skills.
In 2005, a small unit of more than 200 people successfully developed a diesel electromechanically controlled high-pressure common rail tower fuel system, installed on a truck, and successfully completed a 1500 km barrier-free road test.
So far, China has become the fourth country in the world to master the technology.
At the same time, Chinese enterprises are also looking for breakthroughs from other technical directions, at this time, the electronic control in-line pump is an opportunity, although the linear pump electronic control in-line pump injection pressure is low, the reaction speed is slow, can only adjust the amount of fuel injection, it can be said that it can not completely meet the requirements of modern diesel engines.
But Chinese engineers improved the injection mechanism of the in-line pump, decoupled the fuel pressure from the regulation function, used a high-speed solenoid valve to directly regulate the injection, and created an electronically controlled combined in-line pump. This combined linear pump not only raises the pressure above 180MPa and reacts to the pump in milliseconds, but also regulates the time and frequency of injection.
After more than ten years of development, in the non-road field, domestic high-pressure common rail technology manufacturers stand out with an annual sales volume of 100,000 high-pressure common rail systems, and technically, the injection pressure of domestic common rail has reached the international first-class level.
On September 16, 2020, Weichai Group, a leading enterprise in China's equipment manufacturing industry, released the news that the thermal efficiency of the world's first diesel engine exceeded 50%, which means that China's diesel engine can easily meet the National VI emission standards, Weichai ranks among the world's top diesel engine manufacturers, and diesel engine technology has reached the world's top technology for some time.
But from scratch, from weak to strong, from technical barriers to breaking monopolies, China from the back to the top, all the way through the thorns, showing the strongest momentum of development, diesel engine core technology is not in China's hands, but China will use innovation to solve the industry's "card neck" pain points.