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"Too late" was also the verdict on this engine. Perhaps it could have been competitive with this "open fan" propeller.
Thanks, SJC, for the comment about NOx! I was about to write that myself. Hydrogen has among the highest flame temperatures of any fuel. Thus, its NOx production is the highest I know among potential engine fuels. NOx production can be abated with “in-cylinder” measures and in the aftertreatment system, but this is far from trivial. I will not elaborate on that further here. Regarding NOx, hydrogen is far from a “clean” fuel.
Why do you need a V8 in a school bus? This would be an ideal application for hybridization and downsizing of the engine.
As I have mentioned many times before, EVs will not make the particle problem go away. It could even be worse...
DME might be a diesel engine developer’s wet dream. However, it will be very difficult to create a new fuel infrastructure for a new fuel with completely different properties than most of the mainstream fuels.
Has anyone seen any comprehensive information on this engine? The article does not say anything. Another information that came out recently was about a Chinese diesel engine with 50% efficiency. While the relative difference between these engines is about what we could expect for diesel and otto engines in general, the article about the diesel engines does not say anything either. Is this just a coincidence?
I would say that real advancement in engine technology is usually difficult to find. Most of the technology we find on new engines has normally been known for some time before we see it in production. Oftentimes, we can receive such information from the suppliers to the automotive industry. Sometimes such innovation never seems to mature or tends to be too expensive or, by the end of the day, has significant drawbacks or some other issues.
The limit for Environmental Class 1 fuel is 10 ppm but actual fuel on the market is usually much lower than this limit, i.e. around 2 ppm, as a typical value. Environmental Class 1 diesel fuel was first launched in 1990. In vehicle exhaust, the contribution of sulphur from engine oil (i.e. oil additives) is much lower than from the (EC1) fuel.
@mahonj, Well, it depends on what technology and engine size you refer to. We could compare to a 2-liter 4-cylinder engine there is really not much difference in technology compared to this V6. Valve layout, piston and combustion chamber might even be close – or identical – to other VW products. An injection pressure of 2500 bar and twin-dosing of urea is also applied on 4-cylinder engines. In fact, VW was one of the pioneers when it comes to twin-dosing and I think it came first on the 2-liter engine. MHEV is also available on smaller engines. It basically boils down to the e-compressor. Is this superior to twin-turbo, as Audi wants us to believe? I would say: not… very much difference. A state-of-the-art 2-stage turbocharging system can provide at least as high specific power density and similar transient response. Recall that the state-of-the-art power level on a 2-liter engine is in the 240-250 hp range. That is far better than for the Audi V6 engine. One should also note that twin-turbo system is very difficult to apply on a V6 engine due to packaging reasons and the large volume of the plumbing on the exhaust side decrease performance and transient response. This is, of course, a rationale for using the e-compressor instead of twin-turbo on this engine. Besides packaging, however, there is little gain. The basis for benchmarking could, instead, be an in-line 6-cylinder engine with twin-turbo. The Mercedes OM656 engine (e.g. S 400d) is such an engine and it provides 340 hp and 700 Nm of torque. Pretty close to the Audi V6 TDI! Moreover, the OM656 has slightly smaller engine displacement than the Audi. Yet another comparison would be the 4-cylinder engine (OM654) from the same Mercedes engine family, which has an output of 245 hp and torque of 500 Nm.
Synfuels are way too expensive for aviation. It will take some time before you will hear this in the news media, but it will come. Eventually... In Europe, where diesel fuel is heavily taxed, synfuels are not even cost competitive with tax exemption. The situation gets significantly "worse" for aviation fuels, since they do not have any tax. Therefore, it is quite strange to see the interest from the aviation industry. I presume this is just another example of greenwashing. They simply pretend that they have a solution in the pipeline and by claiming this, they can avoid– or at least postpone– any taxes or other economic measures; at least in the near future. We have seen this in the past. Recall that VW and Shell, two of the biggest companies in each of their sector, invested heavily in synfuels, and particularly, in the company Choren. The fuel was called SunDiesel. We saw no sun, but yet another smokescreen, one could say in a rude way
We know that H2 storage and transport is very expensive and consumes a lot of energy. Regarding current and near-future production capacity, it is clear that any "green" H2 produced today could be utilized in refineries. I have not looked at any studies of efficiency of use in each case, but I would guess that the refinery route would be more efficient than using “pure” H2. In contrast, however, the use of pure H2 gives better PR and headlines. With current legislation and incentives refineries would not get full credit for using green H2. Another prohibitive factor is the cost of green H2. The PREEM refinery in Sweden just recently ditched an investment of upgrading heavy oils to fuels. This is said to be due to “commercial reasons”, but also public opinion played a part. The project would have significantly increased CO2 emissions in Sweden. However, when I last time I checked, it seemed as if CO2 emissions was a global problem... By the end of the day, of course, another refinery in another part of the world will make necessary investments to do this job. Probably with lower environmental constraints and higher CO2. Sad. I should point out that PREEM currently make H2 from NG. Needless to say, “green” H2 is prohibitively expensive.
I am glad to see that Carl brought up the NOx/VOC problem. I would also say that EPA's statement that "NOx reductions can actually increase local ozone under certain circumstances..." is somewhat prudent. This is rather rule than exception, i.e. ozone formation is limited by VOC in close to 100% of all cases (in densely populated areas). This is, for example, manifested in the "weekend ozone" paradox that we see in most cities (also in Europe). Ozone is higher during weekends when heavy-duty traffic is limited. This means that further reduction of NOx from heavy-duty vehicles might actually increase ozone levels. Besides that, reduction of NOx will provide positive health effects, so in general, tighter emission limits on NOx is positive, particularly if also VOC (mainly from light-duty) traffic could be reduced simultaneously. There is, however, most likely a threshold effect when there is no positive impact of further reductions of NOx. Note that the lung itself produces NO (you exhale it). Moreover, NO is a natural compound in the body that has several positive health effects, for example, vascular dilatation, which reduces blood pressure. NO is also first defense against pathogens. Sun exposure and ingestion of nitrates, e.g. from vegetables (for example beet root juice, frequently used in sports), are sources of NO in the body. In contrast, there seems to be no threshold level for particulates. Here, a lower level is always better.
Hydrogen is also needed to produce diesel fuel; in some cases, even more than for producing gasoline. Hydrocracking of heavy components to make diesel fuel and jet fuel is a specialty of Swedish refineries. A large expansion is in progress, provided that a permission is granted by authorities and the Swedish Government. Hydrogenation of biocomponents to enable blending in diesel and gasoline fuels is also part of the concept and this will further increase the need for hydrogen. Use of fossil-free hydrogen as a substitute for hydrogen from NG would be complimentary to blending biofuels into gasoline or diesel fuel. The real problem is to produce hydrogen from non-fossil sources in an affordable way. Currently, fossil-free hydrogen is far too expensive.
It continuously surprises me that the VW group always seems to pair the "old" 1.4-liter TSI engine with plug-in hybrid drivelines and not the modern 1.5-liter TSI engine with Miller System (or the VW denotation for it, if you prefer...). The 1.5 engine has higher efficiency, particularly at high loads, and with hybrid drive, you tend to run the engine at a higher load to gain efficiency. Moreover, a larger engine size normally leads to lower efficiency on low load, due to increased friction losses, but this is particularly what a hybrid drive tries to avoid, as indicated above. It is as if you would say that VW tries to avoid the optimal solution. I would love to hear their comments on this.
Some short comments are (I can provide more if anyone is interested…): The e-machine significantly increases the inertia compared to a conventional turbo. Therefore, considerable power is needed just to maintain equal transient response compared to a conventional turbo. Of course, even higher power will improve response and for that, you need a 48 V system. In essence, this is why we have not seen the e-turbo in production so far. Boost pressure at low engine rpm is limited by pumping of the compressor and that potential is more or less exploited already today. Probably the biggest gain might be engine power at high rpm; for sure an important feature for AMG. A bigger turbine than a conventional turbocharger will not choke and reduces backpressure at high engine speed. This facilitates higher power, although boost pressure is not much affected. Will the gain be worth the effort? Well, let’s see if anybody else will adopt the e-turbo... It looks expensive but this is the case also for twin-turbo, e-compressor, and some other options.
To give an example: Twin-dosing of urea reduces NOx by approximately 80% on passenger cars.
@The Lurking Jerk & Michael Some parts of this concept are already in production on passenger cars. I suppose this answers most of your questions/concerns.
Then, the efficiency should be higher than 45% since this can be achieved in a rather conventional diesel engine running on ethanol. Moreover, a practical hydrogen fuel cell seems to be limited to about 60%. This should also be compared to a level of up to 55%, which seems feasible with an advanced diesel cycle and compound turbine in a not so distant future. Options, or extensions to turbo compounding, could be a rankine bottoming cycle, dissociation of ethanol, or a more advanced combustion cycle (e.g. something like HCCI). A fuel cell has "cool" exhaust and no option for recovering waste energy. It is not as if a fuel cell, per definition, would be superior. Moreover, it is not easy to aim at a moving target. Nevertheless, the use of alcohol fuels in fuel cells would overcome the problems in the distribution and storage of hydrogen. This is, more or less, a show-stopper today.
@SJC_1 Yeah, but only if efficiency is high (preferably approaching 96%); not around 30%. I see no information about efficiency (?). The case for the direct methanol fuel cell is similar. Interesting, but not feasible at current efficiency levels.
All right, here we have better info:
I found this quote after a quick search: "There are many similarities,” Bailey said. “Whether it’s a gasoline, spark-ignited engine or compression-ignited engine, you have to modify the valvetrain. So we need the capability to deactivate cylinders on an individual basis."