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Ricardo Announces Demonstration of Tier 2 Bin 2 (SULEV) Diesel
13 August 2007
Ricardo President Dean Harlow announced that the company has achieved a breakthrough with its low-emissions diesel work and is demonstrating a Tier 2 Bin 2 (SULEV) solution (0.02 g/mi NOx) as well as an optimized Tier 2 Bin 5 solution that requires no NOx aftertreatment. (Earlier post.) Harlow made the announcement during the opening session of the 13th Diesel Engine-Efficiency and Emissions Research (DEER) conference this morning in Detroit.
Partnering with an automaker, Ricardo modified a small displacement, Euro-4 compliant light duty diesel engine, adding a sequential turbocharging system, pre-turbine oxidation catalysts, lean NOx trap and particulate filter in the exhaust system.
The Tier 2 Bin 2 engine uses a low-temperature cooling circuit for the EGR and charge air coolers. The combustion strategy uses premixed combustion to lower both engine-out NOx and PM. LNT regeneration and desulfation were calibrated for the vehicle.
Harlow said that a Tier 2 Bin 2 demonstrator vehicle should be available in December 2007, and will be the final deliverable of this particular program. More details on the Ricardo low-emissions diesels will be presented during the course of the DEER conference this week.
Earlier this month, Nissan announced that it was developing a SULEV diesel with a powertrain that includes a new HC-NOx trap for emissions control. (Earlier post.)
August 13, 2007 in Diesel | Permalink | Comments (17) | TrackBack (0)
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Great news! Hope it works and ends up being cost-effective.
It'd be nice to see cost-effective aftermarket treatments like this for large diesel vehicles as well.
Posted by: jack | Aug 13, 2007 10:14:04 AM
Who could the "automaker partner" be? The fact that it is a 4 cyl is encouraging. 4 cyl enignes are plenty for 90% of drivers out there.
I hope it is someone other than Honda. Honda is already on record for developing HC-NOx trap-free Tier 2 Bin 5 compliant engines. Hopefully the mystery automaker partner is from Detroit. The more competition the better!
Posted by: DieselHybrid | Aug 13, 2007 10:19:32 AM
Great news. Diesel emissions technology is making very good progress.
Genuine "clean diesels" need to be better than T2B5. T2B5 merely equates to primitive gasoline emissions levels of the 1970s. T2B2 matches the current best of the gasoline emissions cycle.
It is also encouraging that it was accomplished without using an SCR urea injection system too.
Technology marches forward. I could see the USA advancing to T2B2 for diesels, and a new T2B1.5 "ZEV-ICE" standard, for ICE engines before the blowhard talk-a-good-show "Greens" in Europe, and
Japan even get around to a T2B5+ phony EU6 standard around 2018-2020.
With those levels of emissions, every American locale will be a clean air attainment area, and stay there. Even with the "attainment creep", and increased numbers of vehicles expected in the Future.
The work begun in the late 1960s to clean our country's air and water,and symbolized by the first Earth Day, will have reached fulfillment. Isn't it wonderful to see America achieve an national objective that is approaching success?
Posted by: Stan Peterson | Aug 13, 2007 10:39:33 AM
I've been waiting for that pre-turbine catalytic convertor. By running at a higher temperature and pressure, you increase the reaction rate and the effectiveness of the right catalyst. Now the next step I claim is to put a generator on the turbo shaft, so that you can make that pressure higher yet, more of the time. Taking some of the engine power off of that shaft should be a bit more efficient as well, and the high-speed generator could be quite small. (Actually it should be a motor/generator, to also help shorten turbo lag.)
Now make the car into a PHEV, and I think you've got something. Also, it's a shame for the regulatory framework not to give anybody any credit for the less-toxic residual emissions of certain fuel formulas, and especially methyl ester biodiesel.
Posted by: P Schager | Aug 13, 2007 11:51:19 AM
The "automaker partner" is likely the PSA. Ricardo once worked with PSA on a diesel hybrid demostration project. The diesel for that vehicle is a 1.6L HDi.
Posted by: Mai | Aug 13, 2007 12:07:28 PM
SCR systems are complex, expensive beasts. Also, the additive tank is bulky and adds weight. Clearly, reducing the amount of NOx produced in the first place is an attractive proposition. Sequential turbos (cp. BMW 535d) plus aggressive intercooling are a good start, especially when combined with high-power glow plugs.
Traditionally, compression ratios of LDV diesels had to be in the 17-21 range just so the things would reliably start on a bitterly cold day. Reduced compression ratios reduce peak temperatures and hence NOx production, at the expense of a small drop in thermodynamic efficiency. That, however, is overcompensated by the displacement reduction made possible by the high boost levels. Smaller engine = reduced weight = improved vehicle fuel economy.
Note that Ricardo's strategy for achieving engine-out T2B5 relies on external cooled EGR, highly pre-mixed combustion, in-cylinder pressure guages and tight closed loop control: all code for their variation on diesel HCCI.
@ Jack -
this is NOT an aftermarket solution.
@ DieselHybrid -
Honda is on record stating its NOx aftertreatment is based on a catalyst that generates NH3 ad hoc, enabling SCR chemistry without having to maintain a separate tank of urea solution. M-B claims that system requires incredibly low engine-out NOx as the amount of NH3 produced is miniscule unless you sacrifice fuel economy at low power levels. Then again, Honda may be further along on HCCI combustion than even M-B.
@ P Schager -
placing the catalyst upstream of the thermally powered boost system is possible if you use a pressure wave supercharger instead of one or more turbochargers.
Btw, Garrett and Caterpillar have each developed electrically assisted turbochargers. In the UK, the Foresight public-private partnership is developing TIGERS, a secondary genset for naturally aspirated gasoline engines. All of these are constrained by the low voltages used in today's automotive electric grids. Scania uses mechanical transmission to the crankshaft in its turbocompound.
@ Mai -
I doubt that, Citroen PSA has no presence in the US market and therefore no need to meet T2B5, never mind T2B2. They have given no indication of any plans to re-enter the fray there. European emissions limits will not approach those in the US for many years yet.
Posted by: Rafael Seidl | Aug 13, 2007 1:08:12 PM
Rafael
Ricardo's strategy is clearly not a variation of HCCI. Note that they are employing cooled external EGR and there is no mention of variable valve timing. Just because they are using premixed combustion does not infer HCCI which relies on a flameless combustion process.
In order to control a deflagration flame combustion with Diesel fuel they are likely using EGR to suppress uncontrolled combustion i.e. detonation. The fuel injection strategy relies on multiple injections to achieve a controlled combination of premixed and non-premixed combustion. Naturally enough feedback on cylinder pressure is a handy tool in controlling the process.
Reducing the compression ratio (to levels of around 15:1) is in no way a brake thermal efficiency penalty since it allows for reduced mechanical friction losses. But you are right that improved glow plug technology allows for that. I doubt that there is much saving in engine mass when all additional components are included.
Posted by: extracomment | Aug 13, 2007 2:30:43 PM
Rafael
Ricardo's strategy is clearly not a variation of HCCI. Note that they are employing cooled external EGR and there is no mention of variable valve timing. Just because they are using premixed combustion does not infer HCCI which relies on a flameless combustion process.
In order to control a deflagration flame combustion with Diesel fuel they are likely using EGR to suppress uncontrolled combustion i.e. detonation. The fuel injection strategy relies on multiple injections to achieve a controlled combination of premixed and non-premixed combustion. Naturally enough feedback on cylinder pressure is a handy tool in controlling the process.
Reducing the compression ratio (to levels of around 15:1) is in no way a brake thermal efficiency penalty since it allows for reduced mechanical friction losses. But you are right that improved glow plug technology allows for that. I doubt that there is much saving in engine mass when all additional components are included.
Posted by: extracomment | Aug 13, 2007 2:31:12 PM
@ extracomment -
diesel HCCI requires a completely different approach to gasoline CAI, because the fuels have very different properties. In particular, the long alkane molecules that make up the bulk of gasoil exhibit a negative temperature coefficient, which means some precursor reactions are actually endothermic and delay the ignition.
This property is absolutely central to conventional CI: it permits a fraction of the fuel to vaporize and support conical flame front; the heat released then vaporizes the droplets in the center of each spray, which burn in a diffusion flame. The downside is that ignition delay limits diesels to ~4500 RPM and therefore, relatively poor specific power.
Virtually all modern LDV diesels use some level of EGR to limit NOx formation rates by slowing down the combustion, even with conventional CI. The recirculation is always external via an EGR cooler. On the plus side, there is no need for a variable valve train. If the EGR rate is very high (30-50%), the ignition delay becomes so long that a highly premixed mixture can form. If this is carefully controlled, volume ignition and flameless combustion then follows.
AVL List refers to this as HPLI. Injection is a single event at 1300-1500 bar pressure and quite late. At intermediate load levels, it actually occurs just *after* TDC.
Posted by: Rafael Seidl | Aug 13, 2007 5:36:08 PM
Well, this is extremely encouraging news. Considering the speed at which exhaust treatment is being developed one wonders why we didn't start on this sooner ... well, that's water under the bridge.
A question for extracomment and Rafael S, who both mention compression ratio. What is the point of that? AIUI all modern LDV diesels are turbocharged, so the volumetric compression ratio serves only as a minimum bound, and actual CRs will vary with load. I suppose I can see an efficiency advantage to reducing volumetric compression ratios and scavenging more heat from the exhaust (higher boost pressure), but I am not an engine designer and do not know what other tradeoffs may be involved.
Posted by: cidi | Aug 13, 2007 7:15:16 PM
Rafael
You can hardly expect premixed combustion to be initiated by a late single injection, especially after TDC. "Cooled" EGR is used in Diesels because of necessity. The Diesel engine is operated unthrottled and therefore load is controlled by fueling. Hot EGR displaces air and therefore its range of use is less than cooled EGR. Furthermore there is a thermodynamic penalty to heating the charge. Note that Diesel engine efficiency does not improve by using EGR and most often is degraded.
To answer the question about compression ratio, you need only consider what influences indicated thermal efficiency. Have a look and you will see no mention of pressure for Diesel or Otto cycles. There is a misconception that inlet pressure boosting increases gross indicated thermal efficiency (excluding pumping losses) by virtue of the increased pressure alone. That is false and it's the compression ratio along with the ratio of specific heats of the charge which influence efficiency. Compression ratio is a geometric consideration and does not vary according to charge pressure.
Posted by: extracomment | Aug 13, 2007 11:54:16 PM
@ extracomment -
I've merely relayed to you the essence of how AVL List, who spent the better part of a decade researching this, implement flameless combustion of diesel fuel. The information came from a technical lecture I attended on their emIQ strategy by their CTO.
EGR as such does not improve thermodynamic efficiency, I never claimed it did. The objective is to reduce NOx formation, so you can keep using a diesel at all in spite of tightening emissions standards.
As for reduced compression ratios, those too reduce an ICEs's thermodynamic efficiency. However, what matters in the end is vehicle fuel economy, which is not the same thing. It includes secondary effects such as energy recovery by turbochargers and, reduced vehicle resistance (rolling, acceleration, hill climb) thanks to lower total vehicle weight. A smaller engine with thinner walls is lighter, so are its mounts and their support structure, so is the NVH mitigation, so is the fuel tank for the same range etc.
Posted by: Rafael Seidl | Aug 14, 2007 4:45:22 AM
I bet Ford or Nissan. Ford has existing diesel hookup with PSA, so trying to get those engines T2B5 makes sense. Ford has no announced plans for U.S. car diesel, unlike GM, so they need something. Nissan also needs diesels in the worst way, and again, there is the French connection. I would think that Honda can handle its own development work. Any one else got a guess?
Posted by: factory rat | Aug 14, 2007 4:48:02 AM
Is the current bigoil industry even capable of providing ULSD thats more than 40 Cetane? None of these geewhiz specs are going to be able to be met until 50 starts showing up on the stickers THAT ARE SUPPOSED TO BE ON EVERY PUMP.
Posted by: fred | Aug 14, 2007 1:05:16 PM
Rafael
You are still confusing the compression ratio for an ideal cycle. The fact remains that high compression ratios result in high mechanical friction losses in real engines. the trend to limit the compression ration to around 14 to 16:1 is a practical consideration of real engines. Ideal thermodynamic cycles should never be confused with real engine operation which is not a closed cycle and is in reality a succession of irreversible processes.
EGR is not required to ensure that Diesel fuel can be combusted to meet emissions requirements. There are no laws which state how Diesel fuel should be combusted. It is only the long established view of the auto industry which limits the discussion of what is possible with respect to combustion processes.
Posted by: extracomment | Aug 14, 2007 1:30:52 PM
@ extracomment -
yes, reducing the compression ratio also reduces friction in the cranktrain. However, that gain is typically smaller than the efficiency loss in the real thermodynamic cycle. Only when you consider the fuel economy of the whole light duty vehicle does it become apparent that ratios of 14-16 would actually be optimal. The question is, how do you get there and still meet other constraints, e.g. reliable engine start on extremely cold days.
EGR is not a legal requirement, but it has been the cheapest way to meet rapidly tightening NOx emissions limits in Europe. The auto industry is open to alternatives, provided they work reliably, don't inconvenience the customer and don't cost an arm and a leg.
Posted by: Rafael Seidl | Aug 14, 2007 6:27:36 PM
16:1 compression, 30:1 expansion for me please.
Posted by: clett | Aug 15, 2007 3:19:05 AM
