In recent years, due to the advantages of natural gas engines in energy conservation and emission reduction and air pollution prevention and control, China's natural gas engine market can be described as hot. At present, both the central and local governments have set up subsidy policies for natural gas engine vehicles. With the increase of natural gas import and transportation pipelines and the improvement of natural gas refueling stations, the supply of vehicle gas will be fully guaranteed. . In addition, natural gas engines are gradually gaining more recognition from users due to their mature technology and stable performance.
It is understood that the newly added natural gas buses accounted for 1/3 of the total new passenger car market in 2014, and the growth trend is remarkable. In this context, how should the natural gas passenger car engine develop in the future? What are the main technical routes? What kind of products can better adapt to the current development trend of China's bus passenger transport market?
On the 9th event affecting the Chinese bus industry on January 9, 2015, Cummins Vice President, Cummins China Chief Technology Officer Peng Lixin and Cummins Asia Gas and Bus Market General Manager Liu Yue, respectively, on natural gas buses The engine has expressed its own views on the development of our country.
The main technical route of the current gas engine: lean combustion and equivalent combustion
From January 1, 2015, the emission requirements for passenger car diesel engines in China should meet the national four standards, while natural gas engines have been required to meet the national five standards. Peng Lixin said that in China, most of the natural gas five engines use lean burn technology, the purpose is to avoid the problem of too high heat load, and at the same time, it can produce higher thermal efficiency than equivalent combustion technology.
If lean combustion technology is used, the amount of change is minimal for the engine to change from diesel to natural gas. Basically, as long as the original diesel engine fuel system is replaced by a natural gas system, and then the piston processing is changed to a normal compression ratio, after a large improvement in these two directions, a diesel engine can be turned into a natural gas engine, and the cost of the engine is relatively Lower.
Compared with lean combustion technology, the equivalent combustion technology requires a very accurate air-fuel ratio control strategy, and the cost of the body is high, but it has the advantages of high horsepower and simple emission control. The engine adopting the equivalent combustion technology only needs to use the three-way catalytic technology adopted by the passenger car when performing the post-treatment of the exhaust gas emission, and the cost is low and the application is convenient. Moreover, gas engines using equivalent combustion technology can meet the requirements of the national six emission standards.
The development of engine technology is endless. At present, there is also an EGR (exhaust gas recirculation) technology. Peng Lixin explained that the technology can introduce exhaust gas from the exhaust pipe, hinder the combustion process of the engine and lower the combustion temperature. In this way, through the transformation of a series of technical routes, you can “free up†more space and produce higher horsepower. "Combining EGR technology with equivalent combustion technology can increase the horsepower of the engine from 200 to 400 horsepower, nearly double the amount of equivalent combustion technology alone," said Peng Lixin.
The reliability of the gas engine is not worse than that of the diesel engine.
The industry has always been skeptical about the reliability of natural gas engines, and the general view is that it is not as good as diesel engines. In this regard, Peng Lixin does not agree, he said, "If you can control the deflagration technology, ensure that each combustion can be carried out according to the normal combustion design, the reliability of a natural gas engine can fully match the reliability of the diesel engine. Consistent. Therefore, if the natural gas engine is doing well, there is no reason to prove that its reliability is worse than that of the diesel engine."
Cummins is also demonstrating this with practical actions. Cummins' natural gas engine products entered the Chinese market more than a decade ago. Now, many cities, including Beijing, have adopted Cummins natural gas engines, which have made remarkable achievements in the city's energy conservation and emission reduction and air pollution prevention and control. Prior to 2014, Cummins natural gas engines on the Chinese market were imported from abroad. In May 2014, Cummins launched its first domestic natural gas engine, the L8.9G, in the Chinese market.
Peng Lixin introduced that the L8.9G natural gas engine is developed in China, using domestically produced components and meeting the specific requirements of the domestic market. It adopts the technical route of lean combustion, and the emission meets the national five standards, which can meet the passenger car power requirements of 11-12 meters or even longer. Peng Lixin also revealed that due to the good market response of L8.9G, in 2015, Cummins will also launch a second domestically produced engine, B6.7G, which can reach 250 horsepower to meet the needs of 11-meter passenger cars.
Low-power engines or future trends
At present, the speed of railways, the opening of high-speed railways, the improvement of the aviation industry management system, and the increasing number of private cars have led to an increasing number of transportation resources, and people's travel modes have gradually changed. In the past long-distance passenger transport market, the source of passengers was severely diverted. Nowadays, most of them are facing the problem of reduced customer sources and shrinking market. The opening of more and more inter-city buses has also brought new challenges to passenger transport.
What changes have the quiet changes in the passenger operating industry have on the development of the engine? In this regard, Liu Yue believes that due to the development of the passenger operation industry, small power engines may become the future development trend. He said: "In recent years, through the exchanges with some passengers of public transport passengers, due to the continuous shortening of passenger lines, they are more demanding low-power engines. This also reminds us that engine manufacturers should pay attention in advance. This kind of user needs, and prepare for relevant development."
The energy reserves and consumption structure in China are extremely unreasonable, which has caused China to face the challenges of oil safety, pollution control and greenhouse gas emission reduction, reduce the proportion of coal and oil in the one-time energy structure, and improve natural gas, wind energy and solar energy. The proportion of clean energy is the trend of the times. It is understood that the total length of China's natural gas pipelines is about 35,000 kilometers, and by 2015, the total length of China's natural gas pipeline planning will be close to 100,000 kilometers, almost three times the current level, and the country's emphasis on natural gas applications can be seen.
The promotion of the country, the attention of enterprises, the continuous maturity of technology and the gradual expansion of the market have all brought natural gas engines into the "golden period" of development in China. In the future, China's natural gas engine market will usher in a great development.
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