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The Guardian has a report which says that four of the world's biggest cities are to ban diesel vehicles from their centres within the next decade, as a means of tackling air pollution, with campaigners urging other city leaders to follow suit.
The mayors of Paris, Madrid, Athens and Mexico City announced plans on Friday to take diesel cars and vans off their roads by 2025.
[...] "Soot from diesel vehicles is among the big contributors to ill health and global warming," added Helena Molin Valdés, head of the United Nations' climate and clean air coalition, noting that more than nine out of 10 people around the globe live where air pollution exceeds World Health Organisation safety limits.
Miguel Ángel Mancera, mayor of Mexico City, said increasing investments in public transport would also help clean the city's air, and reduce greenhouse gas emissions. Giorgos Kaminis, mayor of Athens, said his goal was to remove all cars from the city centre. The city authorities will also work with national governments and manufacturers, and promote electric vehicles and cleaner transport.
Recent research has uncovered the scale of the problem, with 3 million premature deaths a year attributed to dirty air, as well as millions of other illnesses, particularly in children.
We seem to have a bunch of bad choices for medium term transport - carbon dioxide or nitrogen dioxide, direct pollution (vehicles) or upstream pollution (power stations).
Diesel trucks and buses seem to have urea containers - maybe they are needed in more cars? Adblue retro-fits for everyone?
(Score: 1, Informative) by Anonymous Coward on Wednesday December 07 2016, @01:41PM
Diesel trucks and buses seem to have urea containers - maybe they are needed in more cars?
Its the udrea "solution" that is the cause of the problem ...
Just imagine, in a matter of yards, a truck with a 16 litre engine changing gear anything up to 20 times
as it accelerates away from the lights and then stops. The exhaust goes from cold (diesel engines cool
down drastically when used for breaking) to red hot, and the NOx content oscillates wildly. There is no way
a microprocessor with a brain the size of an ant can get the urea level correct. Of course there is an NOx
problem. There was not one before, because the engines were not run so hot.
However, admitting that there is a problem with the current "solution" is politically unacceptable,
as a lot of people have their fingers in the pie.
Disclaimer: I know, I was that truck driver.
(Score: 1) by Scruffy Beard 2 on Wednesday December 07 2016, @04:24PM
I checked wikipedia [wikipedia.org] before moderating that informative.
Apparently the injection rate is/em dependent on temperature. Start-stop driving does sound like a degenerate corner-case. The size of the microchip has nothing to do with it though.
(Score: 2) by sjames on Wednesday December 07 2016, @04:26PM
The microprocessor can easily anticipate the changing demand and get it approximately right. Since injecting too much is of little consequence, it can even deliberately overshoot when the accelerator is pressed.
The engines are run hotter now to burn off the fine soot from the exhaust.
(Score: 2) by bob_super on Wednesday December 07 2016, @05:29PM
The microprocessor doesn't have to approximate the exhaust change these days. The injection control knows exactly what's going to happen a few thousand clock cycles later at the exhaust.
(Score: 3, Informative) by LoRdTAW on Wednesday December 07 2016, @07:33PM
No, the problem with the increase in combustion temperature is related to the increase in exhaust gas recirculation (EGR) to meet NOx emission standards. EGR puts some exhaust back into the intake to try and limit the amount of oxygen leftover from combustion which will form NOx under heat and pressure. The problem is the exhaust is hot which raises intake temperatures which translates into higher combustion temperatures creating a better opportunity for NOx formation. They have cooled EGR systems but the heat exchangers can clog with soot pretty fast. They also had problems with leaks and exhaust gas getting into the coolant system causing all sorts of major problems. Plus, it increased the amount of heat dumped into the coolant which meant larger radiators and cooling systems.
A while ago, I was looking at a Q&A page Mack had and one question asked was along the lines of "If SCR reduces NOx, will that reduce the amount of EGR needed?" The answer was no. The reason is because EGR doesn't completely eliminate NOx, but it does reduce a MAJOR portion of it. The SCR system is there to catch whatever NOx EGR didn't prevent. An SCR system needed for a reduced or non existent EGR system would be impractical.
And you are correct, those systems suck big time for an OO or small business because repairs are inevitable, costly, and probably only done at a dealership. The big PITA was the DPF for soot control. Time sucking Regens, clogged injector, bad sensors derating engines, etc. All headaches that don't impact performance, fuel economy (can even reduce fuel economy), or help lower operating costs. That's why I know plenty of guys who are all "fuck the EPA!" and run their pre-2006/2000 trucks just so they can do their own maintenance work and increase up time. I get both sides of the argument for better diesel emissions. I don't want to breathe soot or NOx but I also don't want to see people loose their businesses that already run on thin margins. Saw a post from a friend who runs a dump truck. Blew a $460 steer tire on a $462 load. He made a whole $2 that day not counting food or fuel which put him squarely in the red. Tough business.
A while ago I read about a system Meritor was working on. Something to do with plasma fuel reforming or something. Looks like it never panned out. https://www.meritor.com/ourcompany/news/Lists/News/DispForm.aspx?ID=622 [meritor.com]
Also, those micro controllers might be small. But a loop looking at a sensor or two and adjusting a dose can be run with sub millisecond precision at a few MHz processor speed. The only bottleneck would be the sensor and dosing system speed.
(Score: 2) by Techwolf on Thursday December 08 2016, @01:05AM
The main problem was that in order to clean the DPF, the system inject raw fuel into it, creating that white smoke you see now a days, that is defiantly not cleaner then pre-DPF systems. Due to trucks burning down in CA and excessive emissions from the problems, I don't think it really reduced total emissions due to dumping of worse emissions when things go wrong.