DPF... Problem of understanding...! Inappropriate crutch? (long text)

Hello fellow DIY enthusiasts,

"For some time now, I've been wondering why diesel particulate filters (DPFs) are not being promoted in Germany. In fact, even car manufacturers are increasingly reluctant to voluntarily install DPFs, despite previous announcements made at the IAA in 2003. Instead, more and more vehicle manufacturers are trying to meet the EU4 emissions standard using conventional methods (with Toyota being the latest to join)."

Why all of this?

So, I've been giving it some thought.
A filter, as I learned in school, is a structure with a certain pore size that retains substances larger than that pore size. The mesh size cannot be chosen to be infinitely small, as this would eliminate any flow.
Currently, DPFs have a "pore size" of 5-3µm. Therefore, anything smaller than 3µm passes through the filter unimpeded. Due to the system, the particle sizes in diesel engines are 0.09µm (regardless of the engine type or application)! This is already too small to be filtered out by the DPF. Consequently, the DPF can only filter out cluster particles (multiple particles that have agglomerated). However, this agglomeration is a product of poor combustion processes. Therefore, the DPF only removes the products of poor combustion processes. Therefore, Volkswagen is likely also advocating for exhaust gas cleaning within the combustion chamber.

What happens to the filtrate?
To prevent the DPF from becoming permanently clogged, it is burned off in a so-called regeneration process, breaking down the particles into smaller ones. This occurs at a temperature of approximately 500-600°C. That's precisely the temperature range where furans and dioxins are formed (as far as I'm aware, they are also not harmless).

These smaller particles are suspected of causing damage to the lungs.
The human body is capable of filtering out particles larger than 150nm (0.15µm) through the mucous membranes. Smaller particles can reach the lungs, where they are eliminated by the body's own "scavenger cells" (provided the body is healthy). As can be seen, the size of harmful particles is far below the DPF filter threshold. Therefore, the DPF actually produces particles that can enter the lungs. At the very least, he is certainly not able to filter out the fine particles from the lungs.

The EU4 standard requires a maximum particle mass of 0.025g/km. Vehicles equipped with a DPF (according to KBA homologation) achieve 0.004g/km. This means a reduction of 0.021kg/km. Over 100,000 km, this would amount to 2.1kg. The DPF would need to be heavier to achieve this level of filtration. However, due to the regeneration process, these 2.1kg are almost completely burned off and removed. Since the mass of the particles cannot be destroyed, it must remain. Considering the overall lifespan, the DPF only provides an improvement for the measurement cycle.
I was unable to find any measurements taken during the regeneration process (every 500-1000 km).
In addition, the regeneration process requires energy, which results in increased consumption.

What is the purpose of the DPF then?
Just to reassure environmentalists?
Has Greenpeace ever actually considered what they are demanding?
Why are car manufacturers still trying to hinder efforts to prevent the formation of particles in the engine? The PDF isn't any better either!


I hope there aren't any major mistakes in this text; please correct it if there are.


Here's another little thought experiment:
A Euro 6 diesel vehicle is allowed to emit a maximum of 0.025g/km of particulate matter, which is equivalent to 2.5kg per 100,000 kilometers. During this time, the vehicle will typically require about 2-3 sets of tires and at least one set of brake pads. The particulate matter generated by brake dust and tire wear is certainly greater than that produced by engine emissions.


Here are some additional sources:
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Hmm, aren't those small particles incinerated during the regeneration process? I think I read something about that once.

Best regards, WarLord.

WarLord wrote:

Hm, aren't the small particles incinerated during the regeneration process? I think I read something about that once. Greetings, WarLord

.


That's exactly what it's all about.
The process only involves the vaporization of the particles into smaller sizes that are more easily transported within the lungs.

By the way: Particulate matter/soot is ash.

Hello Bertil.

You're right about what you're writing, but there's another reason why the automotive industry isn't getting involved in this.
Have you ever noticed that, for example, Peugeot doesn't get tax exemptions for their verschandeln diesel HDI engines with particulate filters? This is because, while they retain particulate matter, they produce other pollutants in excessive amounts. The people at Mercedes-Benz and Volkswagen then think that the whole effort isn't worth it. Instead, Volkswagen prefers a verschandeln combustion process that minimizes pollutants and reduces soot emissions through optimized combustion.
It is kept to a minimum, and as you mentioned above, the soot from the filter will eventually be burned off, and the soot will end up back on the road and in people's lungs.

'If I'm wrong about something, please correct me.'

At this point, we also need to give the ADAC a bit of a scolding.

They can only resort to populist rhetoric about particulate filters instead of actually addressing the underlying issues.

I strongly doubt that here (ADAC) is acting in the best interests of drivers with regard to environmental protection and low operating costs (fuel consumption, additives).

If you define 'partikel' (particles) as 'visible exhaust fumes,' the actions of environmental fanatics seem less significant... that's often all they're really concerned about. They then get into their own cars and lecture us about being environmentally friendly because cars are durable and don't waste resources in (new) car production... oh dear.

I recently saw an HDI without a filter. It's no wonder why someone might have needed to replace one...

I think the whole thing about particle emissions is just complete nonsense.
Currently, vehicles emit fewer particles than they intake through the air filter at the front.

Ask a cat advocate what kind of lawnmower they use. If it's a gasoline-powered mower, ask them if they know how far they would have to drive in a car for 30 minutes to produce the same amount of emissions.


CU Gremlin.

Hi,



Ask a cat advocate what kind of lawnmower they use. If it's a gasoline-powered mower, ask them if they know how far they would have to drive in a car for 30 minutes to produce the same amount of emissions.


Are those parts now also available with a catalytic converter?

Perhaps it would be worthwhile to first verschandeln up the biggest polluters and offenders --> utility vehicles!

Hi,

Quote:

Perhaps it would be worthwhile to start by cleaning up the biggest polluters: commercial vehicles!

Yep, I think so too. I've often driven behind public transport buses in Berlin, which spew out huge clouds of exhaust fumes every time they accelerate, and often at intersections, you see a 10 cm pipe on a truck from which a thick cloud is blown directly into the ventilation systems of the cars next to it.

But I don't think this topic has a chance in a country that wants to shift all goods transport onto the roads...

Somewhere, there used to be a percentage figure indicating what percentage of diesel emissions are produced by diesel-powered passenger cars – I believe it was under 10% in Germany, but even that small percentage is now being politicized.

Best regards,

Jan.

Hello everyone!

The issue of particulate filters has been bothering me for a long time. Which sane person would ever come up with the idea of reducing the engine's efficiency by increasing exhaust backpressure, using post-injection for regeneration, and increasing the heat capacity of the exhaust system before the catalytic converter?
There are actually two downsides to this.
1. Increased consumption leads to increased emissions of CO2, NOx, and CO.
2. The reliability of vehicles is suffering because the control unit functions and sensor technology of the engine management system are becoming increasingly complex, and because there is also the added risk of failure due to the DPF (Diesel Particulate Filter) itself, such as clogging, cracking, or other damage.

And what's the purpose of all this? Ultimately, it's to collect the particles over a longer period of time and then release them in a highly concentrated form. Great, a super approach!

The dilemma arises solely from the conflict in goals: it's not possible to simultaneously reduce soot and NOx emissions. If the only goal was to reduce particulate emissions, the engine could simply be operated with a larger excess of air, which would be a relatively easy task for any software developer. You can either shift the map for soot reduction slightly towards a lower injection quantity, or alternatively, increase the overall boost pressure map slightly (or a combination of both).
Unfortunately, this in turn leads to a larger excess of oxygen in the combustion chamber, resulting in higher combustion temperatures and, consequently, more NOx emissions.

Perhaps it would be better to develop a sensible NOx storage catalytic converter concept for diesel engines and to operate the engines completely without EGR .
This would further increase reliability, and the "dynamic rush of air" that occurs when suddenly accelerating would also be a thing of the past, because the EGR valve would no longer need to close first to increase the amount of fresh air.

To regenerate the NOx storage catalyst, it is necessary to ensure that the exhaust gas contains no oxygen at specific time intervals. This condition does not even occur in diesel engines under full load .
Nevertheless, it shouldn't pose a major technical challenge. One could, for example, install a kind of afterburner (e.g., a flame candle) in the exhaust stream that uses the remaining oxygen for combustion. Ideally, this afterburner should be located in the collector duct before the turbine, so that at least some of the energy can be utilized .
In order for the afterburner to not produce soot, the amount of fuel must be precisely controlled (e.g., using a lambda sensor in the exhaust stream).
Now, some people might attack me and say: Before, he argued against the efficiency losses caused by DPFs, and now he himself wants to implement an energetically questionable post-injection and increase the control effort through lambda regulation.
Absolutely correct, I can only agree with that, but I believe that the energy balance still looks better than with DPF systems, especially if the afterburner is located before the turbo .
Another possible solution would be to use a different medium than diesel, one that burns without producing particles. For example, a small gas cylinder could be used, from which a specific amount of gas is released into the exhaust system for the regeneration process to burn any remaining oxygen. If the dosage is too high, the unburned hydrocarbons (CO) originating from the gas would be oxidized to CO2 and H2O by the downstream oxidation catalyst. Therefore, such a solution would not require such a precise dosing system.

Let's see what you have to say about my technical output .

Regards,
Alex.

Hi everyone,

Unfortunately, the whole issue with particulate filters has completely lost its original focus. Initially, the idea was to eliminate particles, either through the filter itself or through improvements in the engine design. The discussion became increasingly heated, and suddenly, every diesel engine (as long as it was a passenger car!!!) was seen as a potential source of lung cancer. At the height of this discussion, a brilliant idea (and we have to give them credit, there couldn't have been a better time) occurred to some French marketing people: to become leaders in verschandeln diesel technology by quickly installing particulate filters on older Euro 3 HDI engines. These filters were, more or less, still in their infancy, but the goal was simply to attract buyers. Unfortunately, as Bertil writes, this probably only works in normal operation, but never after the catalytic converter burns out. It's also quite surprising that the cars, despite being supposedly verschandeln Euro 3 compliant, barely managed to pass. It was clearly a marketing gimmick, and as such, it certainly worked, because the growth rates related to each manufacturer and their diesel share were the highest among French manufacturers during that specific period.
I find it quite remarkable how VW, BMW, Toyota, Mercedes, and others have managed to make their diesel engines comply with the Euro 4 emissions standards, despite the perception that diesel engines are inherently dirty.
Okay, they have to offer the filter, otherwise there's a risk of sales declining. But honestly, as long as there's no discount, who's going to spend €800 or more on a technology that, as Bertil clearly pointed out above, certainly isn't the ultimate solution?

Furthermore, things will get much worse when the Euro 5 emissions standard comes into effect in 2010. This will likely mean the end for small and medium-sized diesel cars, as it will be difficult to achieve the same level of nitrogen oxide emissions from a 2.0-liter TDI engine as from a comparable gasoline engine.
Did anyone in Brussels ever stop to think about this...?
The last question is rhetorical!

Here's a question I find quite interesting: In chemistry, I was taught that carbon always produces soot when it burns, and that longer carbon chains contain more energy but are also more prone to producing soot. So, why shouldn't gasoline, which contains carbon, also produce soot? According to my theory, the gasoline engine would actually be even worse if we only consider the argument about particle size, since the particles would then be much smaller.

Please let me know if there's an error in my reasoning.

Best regards, WarLord.

Did anyone in Brussels ever stop to think about this...?
The last question is rhetorical!


I will still answer with a clear NO.

@FBonNet

Sure, there are lawnmowers with catalytic converters... unregulated and with carburetors. What do you think something like that emits?

Motorcycles could have had regulated catalytic converters for YEARS if lawmakers had just agreed on emission limits. Without a clear development goal, there's no incentive to develop anything, and otherwise, things could end up backfiring.


CU Gremlin.

Hello Bertil and everyone else,

Regarding your explanation, I must say that it is unfortunately incorrect. Contrary to what the word "filter" might suggest, the deposition of soot particles occurs according to different principles. I'm quoting myself from a previous statement: Thesis paper (image description see Word document).

3.3 Principle of operation of particulate filters.

The separation of particles, solids, or droplets cannot occur through blocking or sieving effects when dealing with the characteristic size of diesel particles (10-1000 nm). The pore size in technical filter media typically ranges from 10-30 μm, which is at least 100 times larger than typical diesel particles. The total pore volume or void space of the filter can be as high as 90%. Particle separation occurs through the following mechanisms: either by inertial separation (impaction) for larger particles, by interception from a boundary layer for medium to large particles, or by diffusion for smaller particles, all related to the characteristic size range of diesel particles. The separation efficiency, measured by particle number or mass, for a typical filter medium such as silicon carbide, is approximately 100%.
During the regeneration process, a simple combustion of the accumulated particles occurs, following the formula:

C + O2 = CO2

Therefore, no toxic substances or tiny, invisible particles are produced.
The disadvantages of a DPF include its cost, its negative impact on fuel consumption, and uncertainties regarding its lifespan and performance (e.g., clogging). Of course, reducing particle emissions through combustion is always preferable (the principle being to avoid waste).

Best regards,
Albrecht.

Hmmm...

Interesting discussion.

I would also like to point out that these particulate filters, unfortunately, do not have an unlimited lifespan. Once they have reached the end of their life, they must be disposed of as special waste. I doubt that this is a very environmentally friendly solution.

I, too, would like to give ADAC a 'slap on the wrist' because they seem to have overlooked or deliberately ignored something.

It was a truly interesting discussion. And thank you, Albrecht, for your contribution; I'll skip my own contribution here. According to my information, the DPF burns carbon particles into pure CO2.

Despite this, I remain very skeptical about the DPF.

-the increased consumption negates the technical advancements of recent years in terms of... Ruined consumption.

-The exhaust gas inevitably contains a certain amount of ash. This can be caused by the fuel, the combustion of engine oil, and the presence of fine particles. Therefore, I am rather skeptical about the stated lifespan of the filter.

If you need to replace the DPF every two years, the overall environmental impact is more than questionable.

SeatArosa1.7SDI wrote:

-the increased consumption relates to technical advancements of recent years regarding. Consume again to nothing

*ding-dong* (that's what it sounds like at my place right now)
The Polo with 130 horsepower now has a EU4 1.9-liter engine (engine code = ??), which consumes 0.2 liters per 100 km more in the city, on the highway, and overall compared to the ASZ engine.

Conversely, there is virtually no difference in fuel consumption (0.0 liters) between the EU3-ATD engine in the Ibiza and the AXR engine in the Polo, both in the 1.9-liter 100 horsepower class.

-> Could the 1.9-liter 130 HP EU4 engine also have such a poorly designed filter?