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BorgWarner Develops Hybrid Low- and High-Pressure EGR System for Low Engine-Out NOx
4 August 2008
BorgWarner has developed a multi-loop hybrid (low- and high-pressure, LP and HP) EGR system targeted at meeting US Tier 2 Bin 5, Euro 6 and future emissions standards without the need for NOx aftertreatment, thereby keeping down the cost of diesel systems. Robert Czarnowski from BorgWarner presented the work at the 2008 Diesel Engine-Engine Efficiency and Emissions Research (DEER) conference in Dearborn, Michigan (4-7 August).
Meeting NOx standards through the reduction of engine-out emissions is of increasing interest to OEMs, who are faced, on the one hand, with higher system costs to meet advanced emissions requirements as well as rising prices for diesel fuel. On the other hand, they are competing with ongoing improvements in spark-injected engine efficiency combined with hybridization. Czarnowski said that one European OEM has told him diesel in Europe had reached its peak because of the combination of those competitive issues and the related costs.
As a result of that pressure, there are a number of initiatives seeking to meet advanced emissions requirements without aftertreatment, including Ricardo’s work on a Tier 2 Bin 5 system without aftertreatment (earlier post). At the 29th International Vienna Motor Symposium in April, Daimler presented the concept of downspeeding—lowering the speed of engine and increasing the load on the engine—to reduce engine-out emissions.
BorgWarner’s hybrid EGR system uses the two or more loops in synergy to minimize NOx emissions and fuel consumption.
If you can control the split of the EGR and the cooling of the EGR gas, you can place yourself on the best efficiency of the compressor map...When you do get into the low-pressure loop, you have to recompress the EGR. There can be significant pumping losses to due high mass flow through the closed VTG and compressor conditions near the choke limit. In spite of that, the specific fuel consumption favors the LP loop in most areas.
—Robert Czarnowski
In simulations and in tests with an inline-four diesel on a dyno, BorgWarner delivered engine-out performance close to the coming Euro 6 standard while under high load on the NEDC cycle.
We maintained HP EGR through the city cycle—the first 800 seconds of the NEDC&mash; and at the point we went into high-load cycle, we switched to LP loop EGR [with a resulting] dramatic drop in NOx. We were close to the Euro 6 proposal. Once we improve switching control, we will be able to do so in high peaks of the city cycle as well.
—Robert Czarnowski
BorgWarner developed a number of new components for the system including a lower pressure EGR valve, an exhaust throttle valve, and an air controller system architecture. The system also requires an EGR resistant compressor wheel, which Borg Warner had announced earlier (earlier post).
If combined with a two-stage boosting system, the hybrid EGR approach could provide further emission reduction and improved fuel consumption, Czarnowski said. Asked if the system could meet Euro 6 with a 3.0-liter engine for an SUV, Czarnowski said that he thought the “potential is very good”, using the hybrid system and a regulated two-stage turbo.
Resources
Philip S. Keller, Robert Czarnowski, Olaf Weber, Volker Joergl (2008) Enabling Components for Future Clean Diesel Engines (SAE 2008-01-1530)
August 4, 2008 in Diesel, Emissions | Permalink | Comments (14) | TrackBack (0)
Comments
Posted by: John Taylor | August 04, 2008 at 04:30 PM
Not only that, but they had already changed the definition of "hybrid" from meaning selected corn seeds to some gas-electric automobile contraption. Next thing you know "green" and "parallel" won't mean two rows of healthy corn.
Posted by: ToppaTom | August 04, 2008 at 05:37 PM
OK, so “Engine-out” is NOT as opposed to "engine-in" (nor an bad aircraft situation), but as opposed to “exhaust pipe-out"; to reduce the complexity of the NOx aftertreatment package.
Then I think they want to inject the EGR into the “post turbocharger compressor” air as often as possible to avoid (re)compressing the EGR gas; but they can’t at higher power and speeds due to the higher pressures required . So they need to computer control where they inject the EGR. Makes good thermodynamic sense.
“Gas” engines are improving and closing in on diesels. We all win if diesels also improve or at least regain any efficiency lost through emissions reduction.
Posted by: ToppaTom | August 04, 2008 at 06:01 PM
EGR is not a great thing for diesel engines. It increases the soot loading of the oil, reduces piston ring, piston, cylinder and valve life. But worst of all, it reduces output and BSFC. Sure, mega pressure injection systems and high boost turbo's help, But, the diesel is trending downward in fuel economy. Not exactly what we need in the current situation.
In addition to EGR, adding multiple injection cycles, with major injection timings coming quite late improves NOx. Again at the expense of BSFC. Each subsequent reduction in emissions is coupled with a reduction in real world fuel economy. Why exactly are we doing this? They are clean enough!
Posted by: Franklin E. Fraitus | August 04, 2008 at 06:45 PM
New fuels with lower CN, allowing for premixed combustion, will be the next new break through for CI engines to allow for low engine out emissions and good BSFC.
Gasoline is actually looking very promising in this area...
Posted by: Reed | August 04, 2008 at 08:57 PM
Franklin E. Fraitus wrote:
> They are clean enough!
Great - feel free to suck on the tailpipe of one of those "clean enough" diesels at any time...
Until the air coming out of the tailpipe is as clean as the air going in, it is not clean enough when you multiply the effects by hundreds of millions of vehicles.
Posted by: Dave | August 05, 2008 at 01:42 AM
Franklin,
If Diesels are "clean enough," then how come the air quality was better in Chicago this July than it was in Paris? Keep in mind that Chicago has a higher population and is far behind in public transit use, while Paris has "clean" diesels, great public transit and nuclear-generated electricity (and smog alerts...).
Posted by: Bernard | August 05, 2008 at 10:07 AM
Im sure it has nothing to do with the geographical differences in the Chicago has a lake on the east side to allow the smog to go and Paris has the Alps to help keep smog in.
Its those damn dirty diesels.
Posted by: Reed | August 05, 2008 at 11:05 AM
"Paris has the Alps to help keep smog in."
um, Paris is rather far from the Alps actually, so doubt that's a factor. however, the air seemed perfectly pleasant in Paris when I went there this summer on holiday, so not really sure where Bernard is getting his info from.
Posted by: eric | August 05, 2008 at 12:03 PM
Again...its rather sanctimonious to be trying to meet T2B5 with alleged 40 Cetane fuel. Ya just cant meet "silk purse" regs with "sows ear" fuel. And then to disregard marine and off-road emissions, prevailing westerlies and mountains surrounding west coast ports, causing the whole rest of the country to have to "make do" with less-efficient engines is bass-ackwards and short-sighted as well.
Posted by: fred | August 05, 2008 at 02:03 PM
"not really sure where Bernard is getting his info from"
The Paris smog alerts are not a closely guarded secret; they were on the Paris morning news. Right after the weather info, if I recall.
Illinois provides a searchable database of air quality readings, you can google for it.
I am not saying that diesel is the only source of air quality differences between these two cities, just that we shouldn't assume that European cities have clean air while American cities have dirty air. Other than LA, which is in a peculiar location, most large American cities have fairly clean air in 2008. Some of that has to be thanks to EPA policies (including emission controls).
Mind you, one of the Olympic stories I heard mentioned that the worst recorded smog day in LA this year was still much better than the average day in Beijing, so even LA's not too bad...
Posted by: Bernard | August 05, 2008 at 03:20 PM
Actually you can survive breathing Diesel exhaust due to its high O2 content. But gas engines have no O2, so they are fatal!
Posted by: GdB | August 05, 2008 at 07:58 PM
We are the BorgWarner...
Your NOx will be assimilated...
Emissions are futile!
Posted by: Hal | August 05, 2008 at 09:29 PM
Interesting set of comments!
That diesels are required to be clean, is not the issue for me. The EPA has set the bar so high, small diesels have been effectively "removed" from the American experience. In other words, instead of allowing small diesel engines American manufacturers can produce, then raising the bar incrementally, the limits have been beyond reach.
This has prevented me from owning a Ford F150 diesel (which is what I really need). And forced me to own a V8 powered one which achieves a stunning 13MPG. (the 250-2500's won't fit in my garage and are beyond my reach) Yet the large diesel pickups achieve 18+ MPG in the same conditions.
For the folks in the United states, diesel cars and compact trucks (with the exception of certain wonky VW models) have been out of reach for 20 years! Tell me how this has helped cut our dependance on foreign oil.
Posted by: Franklin E. Fraitus | August 06, 2008 at 04:07 AM
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They changed the definition of "hybrid" from indicating an electric drive system to now being just a multi-functioning component. I think this is a deliberate advertising cheat.
But it is nice to see Europe being more strict on emissions.