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This week, diesel truck engine company Cummins made an unusual announcement. In addition to several new high-efficiency diesel engines, it also showed off an all-electric truck called the Concept Class 7 Urban Hauler EV. The truck is just a concept at the moment, but it's coming in the nick of time—just as Tesla is about to announce its own semi EV.
The 18,000-pound tractor cab, built by Roush, comes with a 140kWh battery and is capable of hauling a 22-ton trailer. According to Forbes, Cummins hopes to be able to sell its battery to truck and bus manufacturers by 2019. Forbes says the truck can run for 100 miles and be recharged in an hour, although Cummins is allegedly working on improving the battery so that by 2020, that recharge time is reduced to 20 minutes.
In a press release, Cummins also said that its EV would come with a diesel-engine generator that could extend the range of the battery to 300 miles, which would offer 50-percent fuel savings compared to straight diesel trucks.
Cummins' news comes just after Reuters reported that Tesla's electric semis will likely have a range of 200 to 300 miles and come with autonomous functions. The trucking industry is a major polluter, and electrification is seen as an important component in reducing greenhouse gases from that sector, in addition to implementing fuel efficiency measures.
(Score: 4, Informative) by CCTalbert on Saturday September 02 2017, @02:10AM (8 children)
You're kind of missing the context/meaning of this.
Typically, Diesel engines don't really throttle the air entering the engine- the power output is regulated by how much fuel is injected. The "gas pedal" is in no way connected to something "throttling" the airflow. Gas engines require this (even if it is computer controlled versus mechanical).
This is one of the efficiency advantages that a Diesel has- the engine isn't continuously working drawing a vacuum, so that "pumping loss" is eliminated. At idle and part throttle there is excess air, essentially it is just compressed and then expanded, sort of like a spring- in a perfect no friction world (which of course doesn't exist) there is no cost for this.
Your "effective compression ratio" is (ignoring all those different real work issues) always the same. (And the higher the compression ratio the more energy you extract from expanding the combustion products = higher efficency.)
In comparison, a gas engine with a throttle restricts the air so the engine expends extra work drawing this air in -> pumping losses. This takes energy and you've lost efficiency. And at idle and part throttle your effective compression ratio is lower- so less energy is extracted. And to make it all worse, at idle and light throttle you need a richer mixture to ensure reliable ignition and combustion- another efficiency hit.
A huge difference is seen at idle- Diesels idle very efficiently- in comparison a gas engine uses much more fuel just sitting at idle. A gasoline engine is most efficient under heavy load. This is why newer cars shutting off and re-starting at stoplights improves mileage and reduces emissions.
Having said all of that- most modern diesels have "throttles" that are used for specific purposes- at shutdown if you don't shut off the air the engine tends to shudder rather alarmingly; there are different strategies used for partial reductions of air to manage emissions and in conjunction with some exhaust gas re-circulation (again emission related). As such they're not even referred to as throttles- for example my TDI has a "anti shudder valve".
Excepting VWs shenanigans, a modern Diesel engine is a rather remarkably refined device for extracting energy from burning fuel.
(Score: 1) by anubi on Saturday September 02 2017, @04:08AM (7 children)
I'll add that gasoline engine operation requires a precise mix of fuel to air to sustain combustion ( stoichiometric ratio ). This was first done by carburetion, but later fuel injectors were more precise and had the ability to adjust on-the-fly, closed loop to compensate for variations so precise combustion ratios could be maintained over all operating conditions. Hence, the "oxygen sensor", used to zero in on the fine line between "too much" gasoline, and "not enough", for the air admitted to the engine via the throttle plate.
The "throttle position sensor" and "mass air-flow sensor" give the vehicle's computer enough info for a pretty good estimate, but that estimate will always be trimmed with internal tables maintained by the computer with historical values required to achieve complete combustion as verified by the "oxygen sensor". When things get too far out of line... that's when that little red "check engine" light turns on, and some people end up with a nasty repair bill.
Diesels... they always run lean. In my diesel van, the air path is wide open from the air cleaner to the air intake manifold. I have a high pressure mechanical injection pump, gear driven from the engine, which sends a squirt of fuel to each cylinder, via an injector - one for each cylinder - at the appropriate time. The amount of fuel delivered per squirt is set by a little lever on the side of the injection pump, which is connected by a control cable to the accelerator pedal.
There are adjustments on the pump which set timing advance/retard, max and idle fuel delivery setpoints.
Now, some people goose up their injection pump to squirt more fuel into the engine, thinking it gives them more power. I flat won't do this. All it does is put more fuel into the cylinder than I have air to burn it with, with the result of producing substantial quanties of black smoke, as there is not enough oxygen to burn off the carbon.. the hydrogens get the oxygen first, leaving the carbon behind. Hence, you often see diesels spouting off prodigious amounts of black smoke when accelerating from stops. Very commonly seen as truckers try to get back up to speed after being stopped at traffic lights. That black smoke is just an indicator you have more fuel than air... so you get to pay for fuel... make a mess in the air.... and benefit nobody. I have my pump adjusted so I do not go into this region... I hate black smoke as much as everyone else.
But the flip side of continuously having a surplus of air for combustion is the production of nitrous oxides, especially on a hot engine. A lean-burning diesel is going to put out very little CO or HC, but will put out NOx. And that's what all this stuff about Blue Def and urea treatments are for... and from what I can tell what the emissions fuss is all about. I note my van seems to run quite clean as far as emissions until I load the engine heavily.... most noticeable if jackrabbit driving during stop and go traffic. I have at times had to "floor it", but I really *hate* do do so.
So far, I have been quite puzzled over the NOx furor. Isn't it NOx that is atmospherically produced during thunderstorms, with the resulting rainwater carrying the now biologically available nitrogen to the soil? Plants cannot get to the nitrogen in the air until that nitrogen is linked to oxygen ( nitrates ) or hydrogen ( ammonia, urea ). Some plants ( legumes ) even have nodes of bacteria in their roots that do this. From what I can tell, I am doing the plants a favor by emitting biologically available nitrogen.... something commonly applied to crops if it was called a "nitrate fertilizer". Certainly do not want the levels of NOx too high ( H2O + NO2 -> H2NO3 aka "Nitric Acid" .... ummm best not to breathe that stuff in high concentrations, and erodes alkali stuff like concrete at even low levels. ).
Its just part of the chemistry physics of diesel engine operation. I believe the higher pressure operation of turbocharging will only exacerbate this effect ( I am not turbo). I believe that this was what all that Volkswagen emissions fiasco was all about... as they tried to meet requirements with "creative financing", which did nothing but obfuscate everything so they could get approvals.
I would use a urea reactor on the van exhaust should I find a low TCO unit... sure wish some hacking group will show how to make one that runs on pee, or sans that, inexpensive fertilizer-grade urea that can be re-used as fertilizer when its use as an exhaust cleaner is spent. I am really fed up with being forced to buy and dispose of "hazardous wastes". Can't this stuff be made so its useful to plants when its life as a exhaust filter is done?
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by fraxinus-tree on Saturday September 02 2017, @06:29AM (2 children)
NOx is good for agriculture, but very bad for people breathing it. Cars produce it a lot in densely populated areas and less in farmlands. So, generally, it is bad. And no, you cannot use pee instead of urea solution. You cannot pee that much urea.
As for fertilizer part, I found it actually cheaper (here in Bulgaria) to buy truck-grade "ad blue" urea solution than fertilizer-grade urea. I used it for de-icing instead of salt, because it ended up in landlord's garden afterwards.
(Score: 0, Disagree) by Anonymous Coward on Saturday September 02 2017, @02:24PM (1 child)
NOx are not particularly bad for people to breathe -- the real problem is that they react with other pollutants to form ozone. See photochemical smog. [wikipedia.org] But you're absolutely right about the distribution problem.
Since smog is mainly a problem in urban areas, I like to envision a world where diesels could run high temperatures, and thus high efficiency, out on the highway, and cut back when they enter town; the difficulty is in implementing it. You can hardly rely on even well-meaning drivers to flip a switch every time, and nobody wants a vehicle that uses GPS to decide whether or how well it's going to run.
(Score: 0) by Anonymous Coward on Sunday September 03 2017, @12:20AM
Nitrogen dioxide (NO2) is harmful when we breathe it. Nitric oxide (NO) and nitrous oxide (N2O), not so much.
(Score: 2) by sjames on Saturday September 02 2017, @08:27AM (3 children)
Not sure what you're doing, but DEF isn't disposed of, it goes out the exhaust as water, CO2, and N2. It's also not hazardous.
VW's problem was they wanted to avoid adding a urea system to their cars and so gain a bit of an advantage over non--cheating manufacturers.
You actually answered your own question. We don't want concentrations of nitric acid in the air of our cities and roadways.
(Score: 1) by anubi on Saturday September 02 2017, @10:41AM (2 children)
Thanks... my old van does not use DEF, but I know the newer diesels require it, and WalMart has shelf-fulls of it.
I guess (NH2)2CO + NOx -> N2 + CO2 + H2O one way or the other...
Maybe some sort of catalyst involved? I know the exhaust can get pretty hot if I am towing. This is something I have not looked too much into yet, but have an interest in retrofitting if I can do it cheaply and not affect the machine's reliability.
Thought some chemistry hacker might come up with a reactor I pee in once in a while to replenish the urea... albeit I would have to clean it out once in a while because other salts are also involved.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by sjames on Sunday September 03 2017, @01:52AM (1 child)
There is a catalyst, but I don't know what it is. I imagine using urine rather than somewhat pure urea would foul the reactor in short order.
(Score: 1) by anubi on Sunday September 03 2017, @05:24AM
I guess I am typical ol' farm boy... trying to find a use for everything.
Waste not, want not, or so some say.
I appreciate your observations... sure gives me a lotta help when I am likely to do something I'll soon regret.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]