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Sales of BEVs in Sweden has stagnated in January-February this year.
You want both good fuel economy and low emissions. E85 is terrible during cold starts, even with port injection. Low-level blends are not significantly better than gasoline. Consequently, there is no other solution but DI and GPF/DPF for good fuel economy and low emissions. The results in the paper are quite clear about the benefit of GPF. This year, many cars with GPFs are introduced in the EU, who leads the world in this field. Yes, those alcohols and ethers without carbon-carbon bonds are good. Under low air/fuel ratio, you can generate soot with ethanol (and higher alcohols) and ethers heavier than DME. Re. methanol, I have no own test data but soot production according to literature will be significantly less than for ethanol, albeit perhaps not quite at the zero level. It should also be made clear that there are no E100, M100 or DME vehicles in series production today, so we can only speculate about the technology that could be used and the corresponding emission levels.
No mention about GPF. The previously launched 4-cylinder gasoline engine in XC40 has GPF. It is, of course, impossible to see what is in the can in the picture. The need for GPF on all gasoline cars is obvious. If only US EPA could understand that... No GPF forcing-legislation in sight until 2025 and if they, eventually, would convince themselves, it might last another 5 years.
My personal communication with bodies who conduct on-road tests for EU member states confirms what Carl stated. NOx emissions are rapidly decreasing from new diesel cars to levels comparable to modern gasoline cars, i.e. practically zero. Moreover, it has also been shown that tailpipe PN emissions from modern diesel cars are lower than in ambient air in densely populated cities.
@Bernard This will definitely come when Mercedes has released more info.
Child miners aged four living a hell on Earth so YOU can drive an electric car:
@HarveyD A recent paper in the scientific journal shows that PN emissions from the tailpipe of a diesel car is ~50% lower than in ambient air. Thus, diesel cars clean the ambient air from the most hazardous pollutant, particle emissions. This, an electrified machine could never do.
With the other cars just recently launched, PSA now offers the first affordable cars with GPFs. Albeit not quite as efficient as diesel DPFs, 75% reduction of particle number emissions is still a giant leap. For the diesel engines, note the combination of NOx storage catalyst (NSC) and SCR that enables these engines to fulfil the RDE limits in future Euro 6d legislation.
Well, it depends on what you compare with. "Half of the greenhouse gas emissions of an average European passenger car" might be true but my family-size diesel car har tailpipe CO2 of 88 g/km, which is comparable to the electric car. This simple example illustrates that conventional and contemporary ICE technology can be competitive with electric cars regarding CO2.
GDI does not necessarily give more NMOG than PFI. During cold starts at low ambient temperature GDI might even be advantageous. Other driving patterns might give opposite results. On average, about equal, as they state. The BIG environmental problem with GDI is particle emissions and this can only be solved by using GPF.
I forgot to mention that Achates consider the oil consumption problem to be solved. At least they have published data (e.g. SAE papers) on very low oil consumption. It is, for sure, more difficult to get low oil consumption on a port-scavenged 2-stroke engine than on a 4-stroke engine but if they have reached a low and acceptable level, it is fine with me. This is not a likely show-stopper anyway.
The ability to use compression ignition (HCCI, or whatever you want to call it) of low-octane and low-cetane fuel in an opposed piston engine has nothing to do with surface/volume ratio of the combustion chamber (though it is good for efficiency). However, it is well-known in the past that 2-stroke engines are better suited to compression ignition of low-cetane fuel than 4-stroke engines. The main enabling feature is that the level of rest gas – call it “internal EGR” if you like – can be controlled in a way which is very, very difficult on a 4-stroke engine. In essence, you control the scavenging process. It is plausible, in my mind, that an opposed piston engine is even better in this respect than a conventional 2-stroke engine. Recall that longitudinal scavenging improves with increasing stroke/bore ratio. Large marine 2-stroke engines can have a stroke to bore ratio of up to 3.5:1 and they are the most efficient combustion engines we know of (~55%). This ratio is lower for Achates but it is still a factor of 2 better than a conventional 2-stroke engine, e.g. the Detroit Diesel engines. In addition, you can use cooled and uncooled EGR. This gives you almost total control of EGR and in-cylinder temperature; crucial factors for obtaining a large speed-load area of HCCI (ideally: 100%). Detroit Diesel once had a 92-series engine that ran compression ignition with CNG. Due to the very low cetane level of CNG, they had to use a glow plug. Glow plugs were already in use on their methanol (M100) engines. One aspect to consider here is that glow plugs at that time were unreliable, if you had to use them more than only for starting the engine. Today, this is not an issue (e.g. ceramic glow plugs). The engine was never launched in production and DDC had already then started the shift to 4-stroke engines for many other reasons. Note that a low-octane gasoline, or naphtha, should have much better properties than CNG. In summary, we know that Achates has many advantages over the mentioned known technology with their OPGCI. Whether they will experience any show-stoppers on the road remains to be seen.
It is normal that EGR is reduced at high rpm. Another factor might be that the capacity of the NOx storage catalyst is limited. If the catalyst is almost “full”, I doubt that regeneration of the catalyst could be done if the driver starts very aggressive driving at highway in that situation. There are some thermal limitations for running an engine slightly below lambda 1 (for NOx regeneration) at very high load. This might explain the great variation between their tests. It is obvious that they tried their best to frame BMW. Given the fact that TÜV Süd has thoroughly investigated this car, I would doubt that there is any defeat device in the software. Everything that DUH showed can be explained by applying some knowledge and common (engineering) sense. Having said that, one could add that there will always be off-cycle driving conditions when a grey zone is entered and some measures have to be taken to protect the engine and aftertreatment. This is allowed in the regulation. The same can also be seen for gasoline engines. One such example is the full load enrichment, which also increase emissions, albeit other emission components than NOx (e.g. CO, HC and PM). Without fuel enrichment many engines would destroy the catalyst, with even worse emissions as a result.
@Thomas Pedersen I can agree with you, although I do not have so many horses in my Ford Focus as you have in your car. It almost never happens that I break 3000 rpm. Normal shift point is just under 2000 rpm. In dense traffic, I would run over the car in front of me if I went over 3500 rpm.
The emission limit for on-road measurements is not 80 mg/km; it is 168 mg/km. Axel Friedrich, a “global” expert on emissions, should know this but one could presume that he chose not to mention this, since it would speak against his arguments. Moreover, the 168 mg/km limit is enforced for NEW vehicles starting this autumn and for ALL vehicles in 2019. The limit does not apply retroactively, i.e. on cars manufactured in 2016, such as this car. If we look at data not so biased as this study, we find that, e.g. the German magazine ams, has ranked BMW as the best one of all manufacturers tested so far. We can also note that the certifying body TÜV Süd backs up BMW. They have tested a similar car of the same model. Neither in the lab nor in on-road measurements could they see any signs of illegal defeat devices. Overall, the tested vehicles showed a very robust emission behavior. We can also note that all new (I presume?) BMW diesel engines will have more advanced emission control than this car, which only has a NOx storage catalyst. New engines have a combination of NOx storage and SCR catalysts. One example is the BMW 520d that (so far) has the lowest level of all diesel cars tested by ams. Starting late this year, BMW is also introducing a new engine with; presumably, even lower emissions than the mentioned 520d, which had the old engine but SCR catalyst.
Well, this is no proof. They have not investigated the WLTP. Find a scientific study! In my opinion WLTP is the best we have for the time being. The claim that US EPA figures are right is a joke. How could a test procedure and driving pattern from the 70's be representative for modern vehicles? No way! Not even with a correction factors.
@HarveyD. You have fudged yourself! A Nissan sold in your country has not been certified according to WLTP!!! US EPA has no plans whatsoever to introduce WLTP in the near future. WLTP was introduced in Europe from September 1 this year. For new cars. Next year for all cars. WLTP is based on logging of real-life driving style in many countries. This was done fairly recently. Your Nissan has been certified according to FTP-75, which is based on logging in the early 70’s. In contrast to NEDC and FTP-75, WLTP has also plugged many loopholes in the testing methodology. Those who are not completely blind have already seen (on this site) that fuel consumption levels for cars certified according to WLTP are much, much higher than for corresponding cars certified according to NEDC. Show me some reference that proof that WLTP is easy to fudge.
The best use of e-H2 would be to put it directly into the refinery, where there already is a lack of H2. Efficiency would be much higher and cost would be much lower. Or, is this route too obvious to be of any interest?
@Mahonj Why is WLTP too easy to fudge? Where did you get that from??? Reference, please! (You could say that about NEDC, though.)
Why would Lamborghini bother about emissions and GHGs? They aim for something completely different.
Organic fluids are not well-suited for high temperatures and pressures, so in case a piston expander is used, water or CO2 would be better options. With water, dimensions could be very small as can be seen in the two references below. At 250 bar, 450°C and 6 000 rpm, you get 1 200 kW per liter of displacement (fig. 8 in the first reference). That is sufficiently small for most applications and certainly much smaller than any conventional ICE today.
It seems as most of you are assessing this invention as if it would be almost production-ready unit. It is just a laboratory set-up, which, at most, qualifies as a proof-of-concept. For example, you cannot make a compact unit if you run at maximum at peak velocity of 0.69 m/s. A free-piston unit should achieve (mean) piston speed in the range of (or above!) modern light and heavy-duty engines, i.e. at least >10 m/s. Modern steam engine concepts also aim at similar piston speeds. Operating at higher pressures also decrease the size considerably. Note the comment: “…the researchers will next investigate the effects of higher pressure and operation frequency on the FPLG…”. Furthermore, note that steam engines are, per definition, 2-strokes, which gives double the number of power strokes compared to a 4-stroke design (in this case, without the drawbacks that plague 2-stroke ICEs). A power cylinder of a steam engine does virtually no compression work in the cylinder; only expansion, which also increase power density. With all positive factors combined, there is potential for very high power density, which also modern steam engines prove by being much more compact that a corresponding 4-stroke gasoline or diesel engine. Whether they will succeed in developing the concept to a commercial unit is another story.
Current hydrofracking in the USA for producing oil and gas is also insane.
The more you pump (or mine) out of the ground, the more CO2 we will have in the atmosphere. This will result in cheap fuel, no restrictions for gas guzzlers and, as a result, an increase of global warming. The only hope for the globe is that Americans eventually (?) will understand the connection between global warming and the hurricanes that tend to plague the country.