Diesel and Urea
Вставка
- Опубліковано 19 чер 2024
- The Professor discusses some of the chemistry behind the recent controversy involving Volkswagen cars.
CLARIFICATION: While many diesel engines (including VW cars) use urea as discussed (marketed as AdBlue), we've heard from viewers explaining the technique VW "fiddled with the computer" used another NOX-removal technology. (The Prof is in India without web access but sends apologies for any confusion he caused)
Periodic Videos on Patreon: / periodicvideos
Volkswagen on Words of the World: • Volkswagen - Words of ...
Carbon Dioxide: • Carbon Dioxide (Part I...
More chemistry at www.periodicvideos.com/
Follow us on Facebook at / periodicvideos
And on Twitter at / periodicvideos
From the School of Chemistry at The University of Nottingham: bit.ly/NottChem
Periodic Videos films are by video journalist Brady Haran: www.bradyharan.com/
Brady's Blog: www.bradyharanblog.com
Join Brady's mailing list for updates and extra stuff --- eepurl.com/YdjL9 - Наука та технологія
It's not that Volkswagen was trying to save customers from wasting urea it was that they claimed it wasn't even needed on their smaller diesel engines so they were produced without this urea tank. While the smaller engines like their 4 cyl models can run in lower emissions without the need for urea, the engine must sacrifice efficiency and power to do so which would not please customers. Their solution seems to be that if the vehicle detected a test, it put the engine settings to a low emission mode with low horsepower and reduced fuel efficiency but great emissions. Outside of the test, the engine ran as normal, producing power, fuel economy, AND NoX emissions.
This wasn't just to save their smaller diesel customers from needing urea though, it also allowed them to simplify the exhaust and catalyst systems, saving them a whole lot of money since these systems usually add several thousand dollars to the cost of the vehicle.
It's a bit like advertising a vehicle gets 20% more horsepower but keeping secret that it only produces that power on a dynamo and never while actually driving.
However, you can fool a test but you can't fool chemistry. When NoX levels started to increase in urban areas, people began to suspect diesel might be the cause and for whatever reason, they decided to test the vehicle emissions under actual driving conditions, vehicle in drive with a driver in the seat operating it, and when they compared those emissions to what they measured when the car was parked and being tested, they found vastly different numbers.
By carefully testing this they concluded that the engine computer knew it was being tested, and had been configured to change engine performance to beat the test.
+Subparanon Yes, you are right. This is very important!
Absolutely. I'm surprised this correction is not top comment, the vw part was clearly not researched.
more replies will get the comment higher.
i don't know if it works when they are from the same person though
+Paul Hendrix but i'll try.
Congratulations Sir for pronouncing Volkswagen correct.
+Tilman Baumann *correctly
Correct
+Tilman Baumann Corrected?
+Tilman Baumann "correct" ist in diesem Fall ein Adverb und Adverben werden im Englischen mit einem "y" am Ende gebildet.
Adverben sind Worte die ein Verb beschreiben. Wenn man mit "correct" ein Nomen beschreiben möchte, dann wird es so geschrieben wie du es in deinem Satz verwendet hast.
Shkotay D
No, correct as in affirmative. (Not going to correct that and make all comments about it make no sense)
Im sorry to correct you, but the VW engine in question (EA 189) does not have the Adblue Technology with Urea. They are older and use whats called a Nox Adsorber. In those the Nox gets adsorbed by barium and reacts to bariumnitrate. In certain intervalls the diesel/air mixture gets enriched on purpose to produce CO or unburned carbon-hydrogens which then reduce the bariumnitrate to nitrogen, barium and water. This system is also called the NOX trap
this.
+Axel He used the EA 189 as an example, still Diesel engines still are being used for high load vehicles such as containers, trucks, lorries and so on.This is suppose to be a educational video about the waste/by-product of diesel engines(most of them) which is NOx or NO2 which are very harmful chemicals that need to be reduced in production.
+Axel +Vinay Vyraveraja well, they will simply have to make another video about the "mechanics" behind the other type(s) of NOx neutralizing technologies, and everyone will be happy, and more important - a little bit more educated
+jz1199 I would like keep at least a bit of VWs reputation, because they make extremely good engines. Just shutting of the Urea tank to keep the customers from having to fill up those tanks would be an extremely weak excuse for polluting the world with NOx. With the older technology it is a lot harder to manage , because you ca't emit to much NOx on one side, but also you are not allowed to emit CO or unburned carbon-hydrogens, which are needed to clean the NOx trap
Axel True that
whoa. an odd number of electrons? that's pretty radical
;)
iammaxhailme I see what you did there.
Great comment, but it didn't come for free.
NO and NO2 are not radicals. The are very reactive molecules that can create Photochemical smog.
@@karlbergen6826 NO is a radical. NO2 isn't
@@iammaxhailme
You right on that. No way the electrons can add up. NO, however, is extremely reactive, combining with O2 to give NO2. This dissolves in water to give a mixture of nitric and Nitro's acids. The nitrous acid absorbs more oxygen to become nitric acid or disproportionates.
Diesel engines don't compress a mixture of fuel and air. It compresses air and at the end of the compression stroke, diesel is injected into the combustion chamber where it will ignite due to the high temp and pressure.
Correct, Sir.
Finally an English speaker who pronounces Volkswagen correctly.
+KreatorRage Well, the professor did visit Germany on multiple occasions in his course of work after all.
Pronouncing a "v" as a "v" and not as an "f" and pronouncing a "w" as a "w" and not as a "v" is wrong in German, not in English.
+KreatorRage He has a Russian heritage so he is likely more sensitive to such things than most English speakers..
+euchenio O, right, like every other ethnicity speak English perfectly by contrast?
Japanese turn every "L" sound into an "R" sound.
Chinese and a lot of other Asians swap the "L" and "R" however they please.
Russians and Ukrainians put a "Y" sound after the first letter of every word.
Germans almost never say "TH" correctly, they usually use a "Z/S" hybrid instead.
Don't be banging on too much about the amount of others' accent anomalies, when you got just as many of your own in your backyard, as in everyone else's respectively.
+Postghost Ze "ze"s are pronounced incorrectly. Anytime someone wants to mimic a german accent, "ze" is always used with words that begin with th.
It just shows the sad state of our civilization that if you go out and say "Look our car is really safe and clean, but it's just a little slower" you'll get blank stares. But if you say "Look our car has 30 more HP than the competitor for the same price" you'll get a "Hell yes!". The environment and public health can't sell cars unfortunately...
The problem is that people are looking for exciting and interesting cars, your average economical 4 door family car or people carrier isnt exciting or interesting enough for people without 2-3 kid families to want them
+iliketotallyloveit You can only use mass transit where it exists. Most people can't cycle 30kms+ to work, and arrive looking sweaty and disheveled, then ride home, nor can you ride during much of Winter unless you're rather mad. Honestly, people only use mass transit if they cannot afford to drive.
+jellyfishattack glad to hear your dad is ok. Rear enders are not much fun. Yes unfortunately some people do have a target on their backs. I can't quite remember how many times I have been hit. 4 on a bicycle. 12+ driving. most minor. I kind of like bigger vehicles for some reason. I don't ride bikes much anymore.
+lost4468yt Then you would have to pay more tax
I've never understood the appeal of fast cars when you can only ever drive them at a maximum of 80mph or so.
While what Volkswagen did was obviously illegal I find it pretty silly that people are really complaining while large diesel utes (or trucks as you call them in the US) are allowed to go around with a fraction of the environmental regulations. The nitrogen oxides emitted by the Volkswagen are utterly dwarfed by those of trucks and hydrocarbon burning power stations.
+kylesenior although I agree with you, it has to be noted that the controversy is not that VW engines are "dirty" (which they are not in comparison, as you pointed out) but that VW cheated on the tests to get the engine certified.
by volume i would bet there are more cars(11 million) affected by volkswagons cheating emissions, producing more NOx than utes/trucks or at least near equal, even if the simi traktors do produce more NOx, at least they dont lie about it.
nice try but all new Diesel engines are required to have either, A DPF (diesel particulate filter) which smaller engines mostly have, or the DEF system that is explained above.
Thats all diesel engines from the small ones in the Jetta to the large ones in Class 8 Heavy trucks.
1:00 When the piston of a diesel engine compresses the air, there is no mixture. It is only air. There is no fuel in the cylinder till the piston gets to the top of the compression stroke and the injector actually squirts some fuel in. Because of the high compression ratio of diesel engines, there would be no way of preventing the fuel from detonating prematurely because of the heat being produced by the high compression, which is why the fuel is not introduced till the end of the stroke.
Oy, can't believe he got this wrong 🤦♂️
It is usually 33 to 35 percent urea. I am a Diesel mechanic and deal with S.C.R. systems daily. I enjoy your videos, so I am glad I could add some info.
I was under the impression that the engines in question were not fitted with an AdBlue tank/system. This lead many to scratch their heads when they first came out, as the figures from the magic triangle of power/economy/cleanliness were so good. Now we know why. The worry in considering purchasing one of these now is that they are a/pretty dirty in reality and b/any recall to 'fix' the software will either make them clean and gutless or leave the power/economy but show how dirty they really are, or realistically somewhere in the middle, not so clean, not quite so powerful/economical. This is why I stick with petrol (gas)!
Love your videos Professor.
As diesel emissions regulations tightened, many engine designers can car manufacturers incorporated a completely new subsystem to the emissions controls - one which injects "diesel emissions fluid" (DEF), or urea - into the combustion cycle. This new subsystem increased the cost and complexity of the vehicle.
In an effort to avoid the added costs and complexity, VW came up with a different plan to "meet" the new emissions regulations ...
They cheated. (And so did Bosch and all the other companies that contributed to the manufacture of the verboten cars.)
From 2009 to 2016 models, VW's solution was to program the computers and sensors to detect when the vehicle was being operated in a testing environment. For example, the engine might be operating above idle - say 1500-2000rpm, while the vehicle speed remained zero. At this point, the engine control would adjust the fuel and combustion parameters in order to pass the test. However, while an engine operating at those settings emitted fewer regulated emissions, its performance was reduced so as to make the vehicle perform very poorly on the road.
Once the test was over and the vehicle returned to normal driving conditions, the engine control would return the combustion parameters to their default setting, at which point the vehicle would emit higher pollutants in violation of the emissions regulations.
After being caught and setting aside $10B to resolve the problems of repairs, buybacks, reimbursements and penalties, I read in 2017 or so that they had already spent $24B. I just read that it's up to nearly $33B.
I love VWs; always have. My daily driver is an older VW diesel (I've got as much as 53 mpg!). But this was the stupidest plan ever. How could they have even imagined this wasn't cheating? Or that they'd not get caught?
I'm not saying that anyone "should" do this, but regulators also clearly don't do their jobs if they got away with this for 7 years. It's a clever solution if you want to artificially keep the price of a vehicle down though. The ethics are reprehensible, but I admire the ingenuity. Also, I have a very hard time believing that they were the only ones who did it, they simply got caught.
I worked in the EPA compliance market in the early-mid 90's using this exact chemistry to control NOx emissions in paper mills....They used urea or anhydrous HN3 along with a catalyst bed to convert NOx to N2 and H20.....the trick was limiting NH3 "slip".....there's a point where increasing the injection levels of NH3 no longer reduces NOx emissions and in fact becomes a significant polluting agent unto itself. The major problem at the time was accurate, continuous monitoring of NH3......NH3 is nearly as soluble in water as water is soluble in water which makes it VERY difficult o accurately measure.....interesting to see the concept alive and well in 2015....
I 'm not sure VW did this to save a consumer money more than they did it to sell cars in California.
+Pepper Spray They could have sold them anyway. They would just have to add more urea which would cost the customers more but then they would meet the emission goals.
I agree re: California. It sorta cancels out the efforts of the environmentalists I see biking to work on the PCH, non?
+AeroDoenot everyone biking on PCH is an environmentalist ;) most of the environmentalists I see on PCH are driving priuses and honking.
Baxter Ross
You just described me!
+Pepper Spray Well they violated European standards in the process so they could be screwed out of so much money.
Finally someone explains what was all that about , all I see scandal and ramifications
Why would you even expect any bit of science from media?
Do you know something I don't? :D
+Star Sadly the expiation is faulty, its quite a bit more complicated
matsv201 Yes, I suspect natural lightning produces more NOx in one day than VW diesels produce in a year.
EPA was needed in the early seventies when rivers caught fire and L.A. air was like pepper spray but they've gone off the chain.
It's to prevent new car companies from starting up unless you have billions in capital like Elon Musk.
+rich5562000 that was exactly my first thought when i heard of the scandal. it's satisfying for the public though seeing such a mighty villain fall.
mibars
"diesel engines does not compress air/oil mixture, but it is injected into combustion"
This is actually not true for all diesel engines. Actually mostly modern diesel that does it in this way.
"Also diesel engines have no control over amount of oxygen"
This is also not really that true. A lot of modern diesel engine recirculate exhaust to reduce the amount of Oxygen.
Also, there is a additional problem. With some modern gasoline engine the fuel is inected under high pressure right into the cylinder just like diesel. There fore they can use high pressure and compression. They still have spark-plugs but don´t really have to use them (all the time anyway).
This is really engine that hybrid diesel and gasoline engines. They are almost always classified as gasoline engine due to tax (at least in Europe). They also fuel gasoline, but it would probably be possible to run then on diesel-fuel, but the mostly don´t.
There fore there is now special regulation for engines with this kind of injection on the EURO 6.
The VW issue was using Exhaust Gas Recycling in Test Mode (makes emissions good but engine performance terrible)
It had nothing to do with AdBlue (which is fitted to larger Diseasels in the VW range)
I did some researching on this subject before all the details were finally revealed, here's what I think is going on.
The reason for NOx reduction equipment, either NOx traps or SCR, is because Diesels are lean burning engines and the catalysts are unable to react with NOx in such a lean exhaust environment. Gasoline engines generally operate in the 14.7 stoichiometric range, whereas Diesel engines are designed to have excess air to reduce soot, improve combustion, and to cool the engine.
The NOx traps require regeneration, which means injecting fuel into the exhaust to cause the catalyst to burn off the trapped contaminants. This regeneration is used in Diesel Particulate Filters too, and causes significant fuel consumption. It's possible to also passive regeneration too, but this requires long drive cycles and elevated EGTs. I suspect that most city driving does not generate the conditions necessary for passive regeneration. This means VW must use fuel to regenerate, causing a loss in economy.
The SCR systems use DEF to treat the NOx in the catalyst. Passat's have a 5 gallon reservoir and 18.2 gallon fuel tank. Typical DEF use is about 5%, or .91 gallons per tank. VW claims the DEF lasts at least 10k miles and they pay for the first 36k miles of DEF. At .91 gallons and 35MPG, the actual use per 10k miles would be around 14.2 gallons of DEF if the engine is using it in typical proportions. This is 3x the use VW claims in their literature. Since VW covers the first 3 fills, that's roughly 10 gallons per fill, or 30 gallons of DEF they don't have to buy. With 11million of these cars on the road, that's about $90 million worth DEF that VW doesn't have to pay for. $90mn is a considerable incentive, but I think the touted DEF efficiency is the major driver. If their vehicles use 3x less DEF than other's, the TCO is lower for customers and that's a selling point.
Now, let's discuss performance. I read claims that the emissions tune produces less torque than the normal tune. Looking at the performance figures from when the new TDI was released in 2008, it's clear that there is a huge performance difference between the previous generation engine (1.9TDI) and the current 2.0TDI. The torque went from 178ft/lbs to 236ft/lbs, which means more cylinder pressures and more NOx. The NOx traps VW uses are a new technology and are expensive. It's not a stretch to consider that the technology is in its infancy and further efficiency gains will be made. That said, I speculate that the NOx traps don't have the capacity to swallow the NOx produced by the newer "hot" tune engines and thus VW decided to have a mild and hot tune, with the hot tune saturating and overrunning the NOx trap. It's quite possible that VW can't achieve the performance numbers with the size of the NOx trap the car is equipped with, so all of the customers who have their cars recalled are going to have a very significant performance and fuel economy degradation. I would bet the revised torque numbers will be around 190-200ft/lbs with 150HP, that's about 15% less overall, and fuel economy will probably drop by 15%.
When my TDi is in regen mode, the car shudders like it has a rough idle. I notice this mostly when stopped at red light. So for those that tailgate me, you get NOx'd as a lesson: back off!
Tosh Outdoors
Diesel engines run cooler with excess air, the EGTs are lower and the cylinders remain cooler because of the excess volume of air. This is part of the cooling system on larger diesels. When you have insufficient air, you get smoke because there is too much fuel and not enough air, this causes EGTs to go up and in-cylinder temperatures to go up. Failure due to hotrodding an engine and towing too heavy a load is common, the failure mode is a melted, cracked, or damaged piston, valves, and turbine, all due to excess fuel (insufficient excess air in combustion cycle) and increased timing. The Northstar engines were advertised as being able to drive without coolant for a significant distance, this is due to a strategy that skips cylinders, causing them to pump excess air through the engine and out the exhaust. Ford (who didn't make the northstar) actually patented this overheat strategy back in the early 80's.
Tosh Outdoors
I'd also like to point out that the alcohol example you provide is based on the latent heat of vaporization, this effect is much more pronounced in spark ignition engines because the fuel must be converted from a liquid into a vapor prior to ignition. Diesel engines inject liquid fuel directly onto the piston, the compressed air causes the highly atomized liquid to ignite, largely skipping the vapor state. Because the fuel is injected at or near TDC, the effects of the fuel chilling are very small.
total heat verses temperature verses combustion rates? Less fuel equals less heat to raise the average temperature inside the cylinder. However a lean mixture has more oxygen available to support combustion, so the combustion is more intense. And that results in higher temperatures right next to the flame.
Also combustion of lean mixtures "complete" at a crank angle closer to TDC. mixture has had less of a chance to expand and that too encourages the formation of NO2 via Le Chatelier's principle.
+Cranston Snord I'm waiting for neither a junior or senior engineer to say anything, and instead for an attorney to say it if you read the regulations, it was permissible. I remember there was a rear bumper test on a car and the car company installed a block right where the testing device would strike. The bumper would't work well if struck at different angles or at different positions, but the task was to specifically survive the impact as described in the test. Wait till their attorney says, the emissions depend on the variables driving conditions. The regulations require us to demonstrate to the sensors how the urea system works when tested under the conditions described in the regulations.
That engine in your diagram sure looks like it has a balance problem... It's bouncing all over the place...
In diesel engine, there really is no spark plug, but you don't compress mixture of air and fuel.
Pure air gets compressed and then diesel fuel is injected at high pressure (>1000 bar if I'm not mistaken) and spontaneous combustion occurs immediately.
+zlac That's how Common Rail diesels work, yes, and today 99% of diesels in cars are Common Rail. Older pump diesels didn't work like that though, as they had something akin to a petrol engine's carburator that pre-mixed fuel and air.
+Robert Faber Old ones had a thing we call "Bosch pump" that did pretty much the same thing as Common Rail, but each cylinder had one pump while Common Rail is one pump for all cylinders.
+zlac common rail can fire more than one time per stroke..
+Robert Faber No, old Diesels also inducted and compressed pure air, but injection happened at much lower pressure in a pre-combustion chamber and much earlier in the cycle (although after the intake stroke). Modern direct-injection happens just before TDC and yes, at pressures between 120 MPa and 300 MPa.
Direct injection allows much better combustion control, and high pressure injection allows much more complete combustion because of much smaller droplets. The downside is that particulate matter is also much finer and thus more toxic, and combustion peak temperature is higher creating more NOx.
pinkdispatcher A significant cause for killing off VW-style pump diesels, as far as I can tell from people who have owned diesels of that or similar nature, is the absolute racket they make. It's hard to conceive of a more unpleasant engine noise than that coming off of an old TDI diesel.
Hi Periodic Videos,
This is a great explanation of how Urea reduction works on diesels, but unfortunately your explanation of the scandal and the tech used in the VW clean diesels is wrong- they dont use Urea at all.
The VW 'clean diesels' that we are talking about dont use the Urea tank technology, which is used by Mercedes, BMW etc. VW found a way to do it without the urea, which saved alot of money, and they called it a NOx Trap. This cheaper solution however relies on the engine running 'rich' to work properly- meaning that unburnt fuel makes its way into the exhaust which assists the N0x traps function.
Unfortunately this reduces fuel economy and performance- so VWs solution was to only use this system properly when the car was being tested. So ironically the actual issue here was that they didnt use a Urea system at all.
Here are some sources: www.livescience.com/52284-volkswagen-scandal-clean-diesel-challenges.html
www.wired.com/2015/09/vw-owners-arent-going-like-fixes-diesels/
Anyhow, I still love these videos, keep it up.
Yes, they did not use a urea tank at all, but I believe the solution was to retrofit a urea tank after they were caught cheating.
Landrew0 The earlier engine did skip the urea injection systems. Later engines had he urea system but used the software module was left in to reduce urea consumption when not on the test.
Brilliant explanation.
Thanks for sharing!
I am a truck driver in the states. The urea additive, is called DEF here. Diesel Exhaust Fluid.
It also has the name 'AdBlue'.
Very informative, thank you professor.
Some people seem to be under the impression that the glow plugs are needed for the engine to run which is completely wrong,they ere there solely to warm the air in the cylinders in cold conditions so the engine will start, in some engines they stay on for a few seconds after starting while the cylinder warns up enough to stop the clouds of smoke older engines used to produce during winter start ups, in summer conditions they are rarely used if at all.
Is that urea computer that appears at 4:29 a Commodore Amiga 2000?
@Subparanon Thank you! That completely answered the questions in my head.
Thank you for the great comments!
Thanks for such a great explanation.
It was actually LNT technology not urea-SCR. Same sort of thing though. The NOx trap fills with NOx under lean efficient conditions and is periodically cleaned by running the engine rich. VW just decided to not run rich as often to save fuel. Modern GDI petrol car also run lean and are having similar problems.
The concentration of Urea is 32,5% to distilled Water if you were curious. And there are indeed a few cars that have a EA189 engine and a AdBlue system.
Dear professor, what about Bio-diesel, any chance of an episode explaining the differences between that and regular diesel when it goes through an engine?
What powers the piston of the diesel engine on start up? The battery alone? It has enough power to move the piston?
Thank you for the explanation!
I know this would probably sound ridiculous to many people but:We could use nitrogen fixing enzymes that converts atmospheric dinitrogen molecules into NH3 ammonia via reduction. The reducing agent could be ferrodoxin. A simple input of energy could overcome the activation barrier (Ea) and would lead to the synthesis of ammonia. You can substitute chemical energy in the form of phosphoralysing molecules like ATP (which uses hydrolysis for catalytic reactions and condensation for anabolic reactions) with a different molecule for production of chemical energy or possibly kinetic energy. You can then use various catalytic molecules that could mimic the enzymes that are present in the ornithine (Urea) cycle. The product would be (( NH2)2CO)), basically urea. This urea can mix with the fuel to help reduce NOX production after combustion. Basically we use what mother nature has given us to help protect mother nature :)
can you examin v-power and regular diesel and petrol and tell us if there is any different between this two fuels ??
do you guys intend on making a vídeo on vantablack?
With reference to the clarification in the description: The quick version of how you tune a diesel to lower NOx levels without urea is to inject more fuel, later. Chemists and biologists will probably appreciate that generating nitrogen oxides is a fairly high-energy process, in engines it occurs most at high temperature and when there is extra free oxygen. If you inject fuel later the peak cylinder temperatures are lower as you have less overlap of combustion/compression, if you inject more fuel then you quench the formation of NOx with simple dilution. Both of these techniques give a less complete burn which means more CO and hydrocarbon emissions (which are a less significant portion of a diesel's emissions than NOx are) and less power.
Sorry to correct you professor. The NOx issue is not only a diesel problem but any "blown engine' s" problem due to high pressures at combustion, since N2 is quite inert to form oxides even at high temperatures, but prone to form them on high pressure and temperature. Modern Turbo petrol engines "do that" too. Plus VW software did not cutoff any urea - they simply sold an engine without urea injection as "clean". The software hack was very simple - it did not allow high power during the test cycle. No high power=no high pressure in the cylinder = no NOx. Test passed.
I work at a heavy equipment Caterpillar dealership and have up to date emissions training here in the states. The mixture is 32.5% urea in 67.5% de-ionized water.
Thank you for your excellent videos.
i have a 2015 golf with the urea tank and despite the software "turning off" the emissions systems. The Urea tank still gets empty about every other oil change. So I don't believe that the system is in fact completely off except when on a dyno. If that was the case wouldn't I hardly ever have to refill the Urea tank?
also curious about having the "fix" done on my car and then simply getting a tune on my car afterwards to help bump up the hp and Torque to what I would be more happy with?
I love how all the educational videos on YT end up having a US vs Non-US(other country) flame war or banter. On-topic, this was a nice peek at the basics or superficial parts of the problem.
Can you do a video about electrolysis? I think its quite cool and I want to know what you guys think about it!
Could you perhaps make a video discussing metallic and liquid hydrogen, are we able to create such incredible states of this element?
I always wondered if there is any HCN in the exhaust gas, regardless of the fuel used by teh car
I always wondered what Adblue was! Never got around to investigating it.
whats the purpose of a glow plug? is it a pre heat for the fuel when the engine is cold?
The aqueous liquid is called AdBlue and the concentration of urea is 32.5% mixed with demineralised and de-ionized water. I manufacture 24 million litres a year here in Australia
Always wondered what a Catalytic Converter was since they were introduced. You'd always hear people talking about them, not so much any more though.
I have a question for the professor. Hypothetically, if the majority of combustion engines on the road ran off of " Brown's gas" or oxyhydrogen, the exhaust product being steam, would this have a large impact on the environment? i feel it would accelerate the water cycle and cause larger storm systems/ more overall precipitation...what are your thoughts? can you do a simple video on browns gas?
well think about it, like all the other things that produced steam as exhaust, such as countless powerplants, trains, and ships during the industrial revolution...
(Also its a relatively large component of Jet fuel exhaust)
very interesting, and timely
NOx is reduced in SCR system by injecting the urea-water-solution (UWS) into the exhaust system. If I remember right AdBlue is the European brand for UWS and it's 32,5 wt% of urea in some applications 40 wt% solution is used. When the UWS is injected into the system water evaporates from the droplets and urea decomposes into ammonia and isocyanic acid through thermolysis and hydrolysis. Once the ammonia reaches the catalyst cell, two main reactions occur: Standard SCR and fast SCR reactions. In the reactions ammonia converts NOx into nitrogen and water.
Unless i'm mistaken catalytic converters are passive aren't they? I mean not controlled by a computer. They're more of a filter at the end of the exhaust line right?
From what I understand, VW is running a richer mixture during the emissions test and a leaner mixer during regular driving. The richer mixture works with the emissions system to reduce NOx. The leaner mixture during driving gives more power and greater fuel mileage. The engines don't have a urea system.
Hi can you do a experiment by mixing petrol with diesel and see if you can re separate them by freezing and at what temperature diesel freezes at sufficiently enough that you could then strain the petrol out. Please any feedback would be nice
The solution you are talking about is AdBlue. We can literally buy IBCs (1000L tanks) of the stuff here in australia. On some of the kenworths in 2011 and many other diesels in recent years, they have had these tanks in the vehicle. Including in some mercedes benzes. BUT they worked out some other way, like some way using a catalytic convertor that after it HEATS UP starts to work. they will work, but ONLY after several kilometers of driving.
I put Urea in my planted aquarium, plants love it
Plants love urea or more probably the nitrates it converts to.
bacteria
urea -----> nitrites
other bacteria
nitrites ---------> nitrates
plants
nitrates -----≥ removed
Brown sluge contains the needed bacteria.
I cannot overstate how much of an impact this has had on the automotive world, in which I work. Countless engineers have lost their jobs, even in departments that have nothing to do with SCR or NOx tech. It´s incredible and scary to see the implications and ramifications.
Nice
You mention that gasoline engines have a maximum size (I assume you mean displacement), but I can't find more about that. Anyone got any leads?
I have a question for the Proff, I drive a truck that holds 120ltrs of adblue in a tank in front of another tank that holds 450ltrs of diesel.......If by chance another vehicle impacted the urea tank forcing it into the diesel what are the chances of the impact creating an explosion?
I'm so glad you made this video!
Dear Professor. Diesel engines doesn't compress mix, they compress only air, and when de air is compressed and hot, the fuel is injected at higher pressure than the compressed air and in that point the ignition takes place.
I enjoy preiodic videos so much.
ciudadanubis de end
there is no lack of power with the idea system ?? ie trucks in the UK and eu have been using the system for about 12years now ?.
I specifically remember thinking "Urea? Really?". Periodic videos to the rescue!
Professor, diesel exhaust fluid AKA adblue is 32% urea and RO water
What about engines operating on Liquefied Petroleum Gas (LPG--usually some mixture of propane and butane) and those operating on CNG (compressed natural gas--methane)? They're definitely uncommon in Anglosphere countries, but they're very common elsewhere. Any possibility to cover these in a future video? Or better yet, engines which run on plant-derived biofuels, like ethanol-rich gasoline/petrol (E85, for instance) or even with modified coconut oil!
Could you try an experiment of sugar and sulphuric acid
Gasoline is more correct. “Petrol” was originally a trade name that was registered by a company called Carless Capel & Leonard in 1870 as a substitute for the word gasoline.
Would it work to inject aqueous ammonia into the gas engine? To reduce the nox
I think they inject ammonia in coal power plants.
Just for reference Urea used in diesel engines is at a concentration of 30-35%. Its marketed and sold under the common name of "AddBlue" as i think urea sounds like urine and not something people want associated with their car/truck. I work for Volvo trucks and often test the concentration level when working on "AddBlue" faults, most of the time faults in system occur from crystallization of the Urea within the spray nozzle or water contamination of the urea tank ie use water not addblue
I never even really cared to think about why, now I'm glad I know!
Thanks for the video! :)
Sir Professor Rocks! I wish my students had the attention span to pay attention, but they are too broke to pay. Perhaps if I could spin chemistry from a farming/ag perspective. It might pique their interest. So, I'm putting forth, politely requesting, that Periodic Videos could help me out. Please.
Isn't diesel injected into the cylinder while the air is hot and compressed?
Just to be precise... Diesel engine IS NOT compressing fuel+air mixture to ignite. It's just compressing air.
Fuel is injected at the moment of ignition, which occurs because of adiabatic process, when suddenly compressed air gets much hotter than uncompressed.
In a diesel engine - The piston compresses air, NOT a fuel/air mix. The intake stroke draws in ONLY air - The air is compressed at ~20:1 and then near the top of the stroke diesel is vented in at ~20k PSI. The diesel almost instantaneously ignites on contact with that environment which gives you the power stroke.
There is a slight error in the explanation of the diesel process.
The fuel is only added at the end of the compression phase which allows diesel engines to have far higher compression rates than petrol engines. (a fuel/air mixture would catch fire halfway trough the compression phase)
And the oxigen sensors are almost only present in petrol cars. (Very large Diesel engines have them but not those in normal cars) because reducing the amount of air entering the engine per stroke could cause the whole process to fail because the necessary pressures can only be obtained with a much air in the burning chamber.
Prof Martyn Poliakoff reminds me of my high-school chemistry teacher!
Correction. A diesel compresses only air, so pre-ignition is not possible and the compression can be much higher and get more energy out of the eventual combustion. At maximum compression, the diesel fuel is sprayed into the air that has been compressed enough to produce instantaneous combustion. Of course, that extra combustion produces more nitrogen oxides.
Hello Professor
I saw this other video that explained a slightly different reasons for the scam.
I am not able to past the link here. Please search "Verge Volkswagen diesel scandal explained" in you tube.
Please comment if possible.
That typo at 2:05 H20 ist real bad. It's definately a 0 (zero) and not O. Right?
this is the same stuff as Ad Blue right? that stuff lorrys put in them
DameAndThatGame Yes. That's one trademark name for the urea solution for Diesel engines.
*note* sometimes emission limits can create more emissions to be made because of loss of fuel mileage
But fuel and air is not being mixed before the compression stroke in a 4 stroke diesel engine, the diesel is injected at the end of the compression stroke where the hot air ignites the directly or indirectly injected fuel. What professor Poliakoff says in the video about diesel engine compression cycle is wrong.
I was cleaning my subscription list and decided to unsubscribe from Periodic Videos. Then i watched a video for the last time, i learned something new again so, subscribed again..😂😂😂
Very informative!
Very interesting!
Just make sure you normalise the video volume before uploading, because it's too low.
Why won't they use catalitic converters to reduce NOx, instead of urea?
I also like how the Prof pronounces con-TRUH-versy.
to my knowledge the VW's in question didn't have Urea injection at all. that was part of the controversy, that VW was able to meet emissions standards without Urea injection in those engines.
You are slightly wrong on the function of a diesel engine, in that the air and fuel are not mixed prior to entering the cylinder, but air alone is compressed, and at the top of the piston's stroke when the air is hot a measured amount of fuel is injected at high pressure (1500+psi) into the hot air, causing ignition.
you say the two fuels are "slightly" different, are they not "significantly" different ? or am i missing something here ?
Great vid, thanks :)
One of the key differences between gas/petrol engines and diesel - is that the combustion energy for diesel comes entirely from the compression. Does the higher pressure cause more NOx to be generated?
NOx is sometimes used as a fuel additive, at least in movies. Thoughts on a reclamation device?
Suddenly, I want to rewrite Fast and the Furious to be a remake of Fight Club, where they make engine additives from rich people's pee.
Nitrous Oxide is not the same as NOx
Another UA-cam channel swept up a 10 foot section of heavily driven highway shoulder, and was able to refine a tiny ball of platinum from that dust. So not all of the catalyst remains within the converter through the life of the car.
I don't get the problem americans have with volkswagen, I mean, have they not seen their american trucks lifted up and rolling more coal than 50s great britain? :D
+Jason W. Morningwood Well these idiots that drive coal rollers are just a few individuals, that exploit a loop hole in the regulations. And to my knowledge they already closed the loop hole. So there is reason to be upset.
+NinjaEule To be perfectly fair, "coal rolling" doesn't produce more NOx. What it does produce is more unbuned carbon in the form of smoke and soot, which, while a serious pollutant, isn't the same thing. It's also not made in the same way. Excess soot, "coal rolling", means a diesel is burning extra rich, or with more diesel per volume of air. This increases horsepower and torque at the cost of efficiency. This is why diesels seen in motorsport tend to be a little sooty, excluding things like the audi le mans ubercars. More NOx is produced with a higher compression, which can increase both power and efficiency, but cars using this technology require more advanced engine designs, heavier duty engine block components, and more advanced and expensive emissions controls. Unless you're Volkswagen.
No loophole has been required to allow someone to modify their exhaust system or engine programming in anything short of a tractor trailer. In fact, legislation expressly made to stop the practice is fairly new. In addition, vehicles not intended to be road legal aren't required to be compliant with anything at all.
If you want to be mad at diesels, be mad at large ships, which produce a disproportionate amount of pollutants, especially when burning heavy fuel oils. Or, perhaps, logging in less developed countries, where burning of excess wood produces more particulate matter and dangerous chemicals than an entire fleet for coal rolling pickups.
+Jason W. Morningwood The thing is that probably well over 99% of cars are fairly new and drive in stock form, so that "coal rolling" and other issues with old cars are quite limited, but when you suddenly have thousands of cars that pollute, even way less much as 70's diesel with smoke tune then they add up and for a serious issue.
I personally think that rolling coal is only done by dusche bags. That's just a professional truck drivers opinion.
+William Warner I love the new exhaust systems no soot, my 3year old stacks are still shiny and the front of my trailer is clean. Rolling coal is for little boys with little dicks.
I am curious as to how the computer knows when it is being tested, and when it is not. Is some electronics connected to the computer during the test?
+geocarey the on board computer checks if the wheels are turning when the engine rpm is above a set level then activates the test mode if the car is not moving
+colinvanful Thanks. Very sneaky!
What nobody seems to mention about these systems is they worsen your fuel economy by ~50%. In the old days a semi truck would get 9mpg on average and today it's 5mpg. That's why truckers go to extremes like putting their own older engines in trucks
nice video!
Adblue is 30-40% (by weight i assume) the rest is distilled water.
5.52. Please tell me about this "cheap petrol". I'm 48, I remember 2 star, 4 star, unleaded, leaded. Now we have normal and super, and there's nothing super about super.