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[YesAuto Engine Technology] We always say that the biggest mistake humans make is sacrificing people's trust in him, and it is often necessary to pay a great price to correct these mistakes. In these years, we have repeatedly seen recall incidents affecting people's confidence in buying in the automotive industry. Just when we were still sighing about the large-scale recall incidents caused by the explosion of the Takata airbag, Volkswagen became the protagonist of the new incident. Cheating against diesel engine emissions has caused them to face recalls exceeding tens of millions. Roughly taking the recall cost of 6.5 billion US dollars, plus the additional fine of 18 billion US dollars, the total loss of 24.8 billion US dollars is by no means a complete figure, which far exceeds the profit of the Volkswagen Group for a full year. However, what is more complicated than Takata Airbag is that Volkswagen's recall involves not only a large number of products, but also the complexity of the recall process.

The astronomical amount of money always touches people's nerves, and what attracts people's attention is how to solve the problem after the public recalls the problematic product. In other words, how to use non-cheating methods to make these models meet emission standards on the existing basis. However, in the face of such a large number of products to be recalled, Volkswagen still seems to have not given specific recall measures. Although the main areas of this recall are North America and Europe, only 1950 vehicles in my country are involved in this matter. However, this does not mean that it has nothing to do with us. Because this is a storm involving the present and even the future of diesel engines. Even electric vehicles and fuel cell vehicles may enter our lives faster. What happened here? What will happen again? Let us go back to the original point, starting from the recall, and look at this incident that is more complex than the previous one.

● 11 million hidden worries

A few days ago, Volkswagen announced the global recall of approximately 11 million vehicles equipped with 2.0L TDI (code-named EA189) diesel engines. Volkswagen (China) Sales Co., Ltd. also confirmed that there are a total of 1950 imported Volkswagens with modified engines in the Chinese market, including 1946 imported Tiguans and 4 imported Magotan (B6). The owners will accept Volkswagen’s recall service in 2016. .

After many days of reports, I believe that the large number of recalls and fines are already difficult to stimulate your nerves. More and more people are starting to pay more attention to what measures the public will take to solve the problem after the recall. Although in the previously announced recall information, the official did not announce a detailed solution. However, because the models involved in the recall have adopted a completely different approach to exhaust emissions. Therefore, after the vehicle is recalled, different solutions may be used. Therefore, before speculating on the plan that Volkswagen will adopt, we must first understand which exhaust treatment methods are adopted on these models.

-Models with LNT exhaust gas aftertreatment device: Volkswagen Golf, Jetta, Beetle and Audi A3

Focus: multiple fuel injection

The full name of LNT in Chinese is “lean-burn nitrogen oxide compound collector”, which captures and adsorbs the nitrogen oxides emitted by the engine during operation, namely NOx. When it reaches saturation (usually about 60 seconds), the NOx is reduced and regenerated to produce harmless nitrogen. Although it seems convenient, LNT needs to use a small amount of fuel during reduction. Therefore, if you want to ensure the reduction of NOx and control the emission level, it is not conducive to the fuel economy of the vehicle. Obviously, this is contrary to the economic and energy-saving selling point of diesel vehicles that Volkswagen has long promoted.

It is precisely because of this characteristic of the LNT system that Volkswagen has set up a program for it to increase the amount of fuel only during detection to increase the level of NOx reduction. In daily driving, change back to reducing fuel consumption for reduction to improve fuel economy. As a result, it can meet the standard during exhaust gas testing without causing consumers to question its economy, and maintain the competitiveness of the model. Among the models involved, the diesel version of the Volkswagen Golf, Jetta and Audi A3 belong to this situation.

-Model with SCR exhaust gas aftertreatment device: Volkswagen Passat

Focus: Urea catalyst

The US version of Passat, which also uses the EA189 2.0L TDI engine, is different from the above four compact cars. This medium-sized car uses an exhaust gas treatment device called SCR, that is, selective catalytic reduction technology. Compared with LNT technology, SCR has the potential to cope with stricter standards in the future.

To use urea SCR to reduce NOx, it is necessary to increase the frequency of urea addition. However, for car owners, frequent addition of urea is not only too troublesome, but also increases the cost of the vehicle, which will reduce the competitiveness of the vehicle. Therefore, Volkswagen has developed a program that only increases the use of urea during testing and reduces the use of urea during daily driving. Such an approach will obviously reduce the frequency of car owners adding urea, but when the vehicle is running, NOx emissions cannot be effectively controlled.

Okay, now that we have understood the two exhaust emission control measures designed in the entire emission incident, then, for these two different structures, we have sorted out two solutions, which have lower implementation costs and immediate results. The software adjustment method. There is also a hardware modification method to get rid of “stubborn disease roots”. After all, which one will the public choose?

Solution 1: Software adjustment

At present, Volkswagen has given a construction plan for the vehicle recall, mainly to modify the engine control software. Official information shows that the Volkswagen EA189 engine is equipped with technology to reduce nitrogen oxides in the exhaust gas by re-directing the exhaust gas discharged from the exhaust valve to the intake side for secondary combustion. Yes, this is the exhaust gas recirculation system called Exhaust Gas Recirculation, or EGR for short. Its existence means that Volkswagen can adjust diesel engine emissions through software.

For models using LNT technology , in addition to adjusting the EGR system, it is obviously simpler and more straightforward to increase the fuel supply used to reduce nitrogen oxides through software adjustments, but whether Volkswagen is willing to reduce the fuel economy of the vehicle will affect What is the reputation of diesel vehicles in this regard for a long time? This is a question that needs to be weighed.

For Passat models that already have an SCR system , because the system itself has very high potential, increasing the supply of urea under daily working conditions can obviously solve the problem effectively, but this is for those who pursue simplicity and ease of use and only use the vehicle as a tool. It is certainly not good news for American consumers.

☆ Solution 2: Hardware modification

As mentioned earlier, there are many vehicles involved in the recall, including both LNT technology and SCR technology models. According to the information already available, it is not necessary to adjust the software, but to re-install the exhaust gas control device that meets the emission standards for 11 million vehicles to be recalled. The hardware cost is very high, and the hardware layout must be redesigned, and the entire exhaust system and the entire exhaust system must be recalibrated. Exhaust gas control system. Within one year of the recall, the possibility of completing such a large amount of work is close to zero.

Inferred Recall Solution

Through the comparison of the two schemes, it can be easily seen that by adjusting EGR, increasing the fuel injection volume of the LNT system, and increasing the urea supply volume of the SCR system, the vehicle involved can be recalled in a short time, and the overall scheme The cost is lower than the hardware modification. Therefore, the possibility of improving the recalled vehicles by modifying the software is relatively higher. After consulting with a number of suppliers related to diesel engine design, production and exhaust emission control, we also got a positive answer.

-How to solve the domestic models involved?

At present, the domestically designed models are mainly imported Volkswagen Tiguan and Magotan models. It is believed that software adjustments synchronized with foreign countries will also be carried out. The specific plan will also be determined according to the type of exhaust gas aftertreatment device equipped with the vehicle.

● Is the diesel engine really “incurable”?

In the preface, we mentioned that this incident may affect diesel engines, even pure electric vehicles, and fuel cell vehicles. This is not sensational. Because the EU has always favored diesel engines with lower fuel consumption for the choice of vehicle engines, you can find that hot-selling models have diesel engines to choose from on the official website of the company.

After Volkswagen's “emission gate”, it has been exposed that other brands of diesel engines also have fraudulent behaviors in different situations. It is not just Volkswagen that has encountered a crisis of trust this time, it can be said that the entire diesel engine family has been questioned. Such a result may change the attitude of car companies towards diesel engine research and development, and vehicles driven by new energy sources may appear on the stage faster. However, until then, a large number of diesel engines will still be the main force in the market. Precisely because diesel engines will frequently appear in our lives, it is necessary for us to have a deep understanding of the current diesel engine exhaust emission treatment technology.

-Comparison of three mainstream processing methods

At present, major component suppliers such as Faurecia, Bosch, Cummins, etc. have introduced mature exhaust emission aftertreatment technologies, which can specifically solve the problem of diesel engine emissions that do not meet the standards. Mercedes-Benz and MAN started producing and selling passenger cars and commercial vehicles that meet emission standards 10 years ago. The LNT and SCR technologies have been introduced above, and DOC+DPF technologies will also be mentioned here. What is the difference between them? Let's take a look at DOC+DPF first, and finally a comparison.

☆ The most realistic partner: DOC+DPF

Most of the diesel cars in our childhood impressions are silly, big, black, and thick. The black exhaust that they remove every time they pass by is regarded as the “heritor” that leaves us with such an impression. In these black exhaust gases, particulate matter occupies a large proportion, and it is also the main cause of air pollution. The DPF technology we are going to talk about below is a weapon to eliminate this culprit.

The working principle of DPF is relatively simple. It filters and collects the particulate matter contained in the exhaust gas through a filter. After the particulate matter reaches a certain amount, it is burned to convert it into carbon dioxide (CO2) and discharged. In addition, it only needs to be installed on the silencer, so it is currently the most popular.

☆ Cost control king: LNT

With the continuous improvement of emission regulations in various countries and regions, traditional exhaust gas treatment methods have begun to show a state of being exhausted. At this time, the nitrogen oxide adsorption technology of LNT began to move forward. However, when the emission regulations are further raised to the Euro 6c standard, although the LNT system can still improve the treatment effect in theory and meet the emission regulations, the resulting cost increase is too high.

☆ Rising star: SCR

With the continuous improvement of emission regulations, people's demand for diesel engine emission control has become more urgent. After research, engineers developed a method of catalytic reduction by injecting a reducing agent into the exhaust gas based on the characteristics of most diesel engines in oxy-fuel combustion, high oxygen concentration in the exhaust gas and low carbon monoxide concentration. At present, 5 of the 7 major commercial vehicle manufacturers in Europe have begun to adopt SCR technology.

Comparison of common diesel engine exhaust gas treatment methods
DOC+DPF LNT SCR
Features The treatment of CO and particulate matter has a good effect, which can meet the future national 5 emission regulations Simple structure and low cost Excellent treatment of nitrogen oxides
Disadvantage It is more difficult to meet the stricter European emission regulations in the future, and it needs to be used with EGR. When meeting higher emission regulations,
The cost of hardware upgrades is relatively high.
It is impossible to treat the hydrocarbons and particles in the exhaust gas, and the car owner needs to add the urea water solution by himself, and the system takes up a little more space.

From the above explanation and chart, it can be easily seen that the DOC+DPF treatment method is the best choice to meet the current emission regulations, but when faced with higher and stricter emission regulations, it is similar to the LNT treatment system. Powerless. At this time, SCR technology seems to be the savior to save the future of diesel vehicles.

-Pain of SCR promotion

So, why is the SCR technology that has excellent nitrogen oxide treatment effect and can better meet the stringent emission regulations in the future has not been fully popularized until now? First of all, although the SCR system can generate nitrogen and water through a high temperature oxidation-reduction reaction in the catalyst with the help of urea, the reaction can effectively reduce the nitrogen oxide content in the exhaust gas of the car. However, the treatment of other substances such as particulate matter, hydrocarbons, alcohols, and lead compounds in vehicle exhaust still requires traditional three-way catalysts.

● What should we do in the future

-SCR new technology

The “Diesel Door” is not only a crisis of trust for the Volkswagen brand, it can be said that the entire diesel engine family has been questioned. Such a result may lead to the attitude of European car companies towards diesel engine research and development. In the future, emission testing is bound to be stricter and emission regulations will be more stringent. Therefore, technologies with better treatment effects and more convenient use in the later period may be more displayed. stage.

Of course, the further development of SCR technology means more thorough treatment of nitrogen oxides. On the other hand, we cannot ignore the presence of hydrocarbons and soot particles in the exhaust gas. With the further development of technology, future diesel engines may abandon EGR technology. Engineers can adjust diesel engines more “radically”. Of course, the resulting emissions of hydrocarbons and soot particles will be even greater. Many, this also requires more perfect DOC and DPF technology. This is not a idiotic dream. Several exhaust emission treatment suppliers we interviewed have all started relevant research.

-g-tron, fuel cell

Diesel engines will not disappear due to the “diesel gate” incident in a short period of time, and more emerging technologies will benefit from this and have the opportunity to take the stage.

Full text summary:

With the passage of time, the number of diesel vehicles with exhaust emissions problems gradually increased. By analyzing the exhaust emission control strategy, it can be found that these diesel engine models have adopted different treatment methods such as LNT and SCR. Considering factors such as time, financial resources, and rearrangement of hardware, changing the vehicle software system is the most likely method that Volkswagen will use to meet the emission standards of these huge number of recalled models in a short time. Of course, even if the lowest cost recall method is adopted, the total recall cost and fines of US$24.8 billion cannot be avoided. Such lessons cannot be said to be painful.

However, if we take a more long-term view, we will find that such fines are not “unjust”, and even promote the promotion of diesel engines. After such incidents, emission regulations will be stricter, loopholes in testing will be compensated, and testing procedures will be more complete. This will also force manufacturers to improve their R&D level and respond to testing. Although the current mainstream DOC+DFP and LNT can fully meet the requirements of recent emission regulations, in view of the more stringent emission regulations in the future, the SCR technology, which has not yet been fully popularized, is also the winning trump card for the promotion of diesel engines. The future of diesel engines is still bright.