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Delphi Launches Diesel Direct Acting Piezo Injection System; Lower Emissions and Fuel Consumption, More Power and Torque
6 September 2008
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| Delphi Direct Acting Injector (DFI3) compared to a conventional servo-hydraulic injector. Click to enlarge. |
Delphi Corp. has launched the Delphi Direct Acting Common Rail system, its next generation of diesel fuel injection technology based on a new direct acting piezo injector, the DFI3 Piezo Injector. The new system is now entering production and will be available on a European production car to be launched later this year.
The DFI3 piezo injector needle is set in motion directly by a piezo ceramic actuator, rather than being moved via an electro-hydraulic circuit as with existing fuel injection technologies. This enables the injector to spray fuel into the combustion chamber faster and with much improved spray momentum and accuracy and provides extremely fast opening and closing of the needle valve, independent of injection pressure.
The resulting improved combustion control provides additional reductions in emissions (e.g., approximately 30% fewer NOx emissions versus current injection systems), more torque and power (approximately 10%) across all engine speeds and improved fuel economy and refinement.
Delphi competitor Continental also introduced a direct-drive piezo injector earlier this year. The first series production application of the new Continental technology will be in a light commercial vehicle in 2009. (Earlier post.)
Injector technology. Injector technology to date uses either a solenoid or piezo actuator to control a hydraulic circuit that moves the injector needle. Servo actuation can be split into two categories, referring to the pressures applied on both sides of the valve: balanced and unbalanced. The different types of injectors so far on the market are:
- Servo-solenoid unbalanced valve (first Common Rail type introduced in the market);
- Servo-solenoid balanced valve (a Delphi system currently in production); and
- Servo-piezo unbalanced valve (only type of piezo injector in production to date).
- There is no servo piezo balanced valve design currently in production.
The electrical energy required to move a balanced valve is lower than that required to move an unbalanced valve. The balanced valve therefore allows a smaller actuator that can be driven at 12v (battery voltage) and can be packaged inside the body of the injector and very close to the needle tip. This in turns allows for shorter hydraulic circuits and smaller moving masses, providing speed of needle actuation. Delphi uses this in its servo-solenoid balanced valve design to deliver performance equivalent to unbalanced servo-piezo systems.
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| Comparison of spray with the direct acting injector on top, and a conventional servo-hydraulic injector at the bottom. Click to enlarge. |
Direct acting piezo injector. The new direct-acting injector removes the hydraulic circuit along with the associated lag and energy consumption, and provides significant additional control possibilities for engine designers. Other benefits include stability over its life time, robustness of injected quantities for varying injection patterns, low shot to shot variation of injected quantities and high spray momentum.
The Delphi Direct Acting diesel common rail system uses the piezo ceramic actuator to operate the needle valve of the injector for initial lifts, such as those obtained in pilot injections, and a hydraulic amplifier to help complete the lift for large injections. This approach allows the injector to spray fuel into a diesel engine combustion chamber faster, with greater accuracy and at higher pressures (up to 2,000 bar) and with higher efficiency than current injection technologies.
This provides an advantage equivalent to raising the system pressure by about 200 bar. In other words, the 2000 bar of a Direct Acting Piezo injector has a performance comparable to a 2200 bar servo injector.
—Dr. Detlev Schöppe, Delphi Diesel Systems engineering director
The direct acting injector is also completely leak free, so no high pressure fuel is wasted into a return flow, saving up to 1 kW of lost energy used by today’ss servo systems and removing the requirement for expensive fuel coolers.
This system was initially developed to optimize certain key performance requirements expected to be enablers for future emissions legislation:
High mean effective injection pressure (Square rate of injection at any pressure up to 2,000 bar; today’s servo systems are far from square rate particularly in the low to mid rail pressures critical for emissions control).
Multiple injection flexibility (seven injection events or more).
Capable of zero hydraulic separation between injections.
Pressure reservoir within the injector thus avoiding pressure waves between the injector and pressure supply, and their effects on needle dynamics and injection quantity.
Fast opening/closing of the nozzle needle (close to 3m/s or three times faster than today's systems).
Elimination of back-leak flow.
Proportional control of needle lift by the Engine Control Unit (ECU) allowing the rate of injection to be mapped into the ECU. This allows separate optimization of idle noise, emissions and full load performance where as today the rate of injection is controlled by the injector hardware and is a compromise between the three different areas.
Benefits of the Direct Acting Injector
Fewer emissions. The faster needle actuation reduces the quantity of fuel injected at low needle lifts, minimizing the highly variable spray structure at the beginning and end of injection events, where much lower momentum reduces the ability of the fuel jet to penetrate the combustion chamber in a controlled manner and to provide the optimum air fuel mix, leading predominantly to particulate matter or soot formation.
The Direct Acting spray reduces particulate matter by up to 30% over today’s servo systems at the same fuel pressure and Exhaust Gas Circulation (EGR) levels. With the current fuel injection technology, at medium to high loads, the use of high levels of cooled EGR allows very low NOx levels to be reached but usually at the expense of increased soot. With Delphi’s Direct Acting piezo injector, for the same soot level and rail pressure, NOx can be reduced by up to 30% by using more EGR. This is possible since the Direct Acting injector provides higher spray momentum, particularly during the opening and closing phases of the injection event and therefore allows additional EGR to be tolerated.
This emission benefit of Direct Acting allows for cost optimization of the aftertreatment. Particulate filters can be reduced in size or, conversely, NOx aftertreatment may be avoided. In addition, ever increasingly priced precious metals for the oxidation catalysts can be significantly reduced.
Better fuel consumption. The direct acting piezo injectors do not require a return flow to operate—all fuel is injected and no fuel wasted in a return flow. This improves the injection system’s thermal circuit to such an extent that, even at a rail pressure of 2,000 bar, fuel cooling is not required.
This return-less design results in energy saving and permits downsizing of the high pressure pump which also contributes to fuel economy enhancement. The hydraulic concept offers a 1 - 2% improvement in fuel consumption with respect to other injector concepts, in addition to the emissions benefit.
If the engine is configured to maintain existing emission levels, the fuel consumption benefit from the direct acting injectors can increase to 3 - 5% as further fuel consumption benefits can be obtained by either reducing rail pressure or reducing the rate at which the particulate filter needs to be regenerated.
Delphi’s Direct Acting diesel common rail system also features Individual Injector Characterization (I3C), an exclusive Delphi technology that enables the ECU to be calibrated with the injection system to also contribute to accurate fuel delivery and reduced maintenance costs.
More power and more torque. Delphi’s Direct Acting common rail enables operation up to 2,000 bar. This rise in pressure, which represents an increase of more than 60% compared to the first common rail systems, helps to increase the engine’s output and torque.
Noise Vibration and Harshness. In addition to the power and torque improvements, noise is reduced by up to 5dBA thanks to the use of the multiple injection strategy. Moreover, by offering the ability to control the needle opening rate electronically and independently of hydraulic constraints, the engine calibrator is able to satisfy the conflicting requirements of NVH optimization and minimization of exhaust emissions. At idle, the Direct Acting injector concept makes no perceptible noise above the engine itself.
Delphi says that the Direct Acting Piezo advantages of higher spray momentum and highly flexible multi-injection make it an promising choice for the next generation combustion systems (e.g., HCCI, PCCI, etc.)
With the introduction of the Direct Acting Common Rail, Delphi now offers two families of Diesel Common Rail Systems: the Balanced Valve Fast Servo Solenoid Injector and the Direct Acting Common Rail with the Direct Acting Piezo Injector.
Resources
Detlev Schöppe (2008) Exceeding Customer Expectations with the Innovative Direct Acting Diesel Fuel Injection System: Unique Advantages of a Breakthrough Technology (Paper presented at the Vienna Symposium)
Guillaume Bression, Dominique Soleri, Stephane Dehoux, David Azoulay, Hedi Hamouda, Laurent Doradoux, Noureddine Guerrassi, Nicholas James Lawrence (2008) A Study of Methods to Lower HC and CO Emissions in Diesel HCCI (SAE 2008-01-0034)
September 6, 2008 in Diesel, Emissions, Engines, Fuel Efficiency, Vehicle Systems | Permalink | Comments (16) | TrackBack (0)
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Comments
I listened to several of papers by Delphi, amongst Bosch, (then Siemens) VDO and several OEMs at a GDI conference last year. Direct-piezo actuation was one subject of discussion. There's a lot of technical synergy between DI Diesel technology with DI Gasoline, but there can be even more.
In most companies like Bosch, Delphi and Continental VDO, the Diesel injection group has separate staff and management from the gasoline injection group; which sort of makes sense in some respects, but it's funny to gauge the attitudes of one group to the other. There's intense competition between the two groups within each company, to the point that there's even some animosity. I heard snickers and could sense groans whenever questions or discussions came up to compare and contrast DI Gasoline with DI Diesel.
The aforementioned HCCI and PCCI combustion processes will only mean a further blurring of the lines between traditional gasoline and Diesel engines, and their respective fuel injection equipment. The two groups better get to talking a lot more to each other that snickering about the others' inferiority.
Posted by: TDIMeister | Sep 6, 2008 11:57:16 AM
30% reduction in NOx emissions over CURRENT systems is quite impressive as is the 5dba noise reduction. A 10% increase in hp/tq is also impressive (though I don't know their baseline).
If their basline is against BAT, that would mean BMW could get ~110hp/liter out of its turbo diesel fours.
Whoa!
Posted by: GreenPlease | Sep 6, 2008 3:16:27 PM
This is good stuff, because a lot of people in Europe use diesel and we will get lower NOx omissions.
Also, with lower Nox, the day of getting diesel into the US is getting closer.
Posted by: mahonj | Sep 7, 2008 5:14:38 AM
p.s. anyone seen Rafael - we could use his comments on stuff like this.
Posted by: mahonj | Sep 7, 2008 5:16:26 AM
Rafael is missed. His insights were educational and invaluable to the community.
BTW, at a certain point, NOx emissions are low enough to simply use an LNT in place of SCR. Several companies are working on an LNT/DPF combination aftertreatement system that would reduce backpressure. Someone should try to figure out a way to eliminate the muffler while keeping noise low to further reduce backpressure.
Perhaps small perforations along the wall of the exhaust would serve this purpose?
Posted by: GreenPlease | Sep 7, 2008 7:05:06 AM
GreenPlease:
Our make believe F-1 foolhardy young drivers drill holes in their old Honda Civic exhaust system to multiply exhaust noise level by up to 300+%.
Multiplied 100 folds, it is the most anoying thing in our small town. We have to endure something close to F-1 race track noise for hours every day. We can hear those modified Hondas up to 2 Km away.
We are moving out to go as far as we can from those modified exhaust systems. (if we can find such a place).
The day of the last ICE machine on our roads and streets will be a glorious day.
Posted by: HarveyD | Sep 7, 2008 8:32:38 AM
@Harvey
Curious. I've seen the inside of OEM BMW exhausts (7 and 3, I'm guilty of curiosity) and both have perforations but to differnt effect. The 3 is noisy while the 7 is quiet. Placement of the holes/bumps relative to the frequency of the sound and its source probably determines whether or not the sound is silenced or amplified.
Posted by: GreenPlease | Sep 7, 2008 8:49:34 AM
@ GreenPlease
The young drivers (or the local body shops) must know where to drill the proper size holes to maximize the exhaust system noise on their jelopies.
That type of noise pollution will probably last as long as we have ICE vehicles on our streets.
Posted by: HarveyD | Sep 7, 2008 9:31:40 AM
It interesting that multi point injection getting very popular in last few years.
I belief that they doing that from wrong location of the combustion chamber, that why the relatively high emission in contemporaneity Diesel engine.
Even with Delphi Direct Acting Piezo Injector you can avoid the fuel hitting the cold parts of the combustion chamber. That is a main reason for particle emission. The NOx emission is connected to localized temperature increment during the combustion. To minimize the localization the multi point injection is used. The ultimate goal is the Homogeneous Combustion, but with current approach that not gonna happen.
I got a patent (5,385,127) back in 1995 that solve some of that problems. The idea was to inject the fuel from outer walls of the combustion chamber towards center. The number of injection point could be more then 100. It will be interesting to couple that patent with the piezo actuators.
Here is the link to US Patent Office, check it out specially the image link in there (you will need AlternaTIFF plug in to viewed):
The Patent link)
http://patimg1.uspto.gov/.piw?docid=US005385127&PageNum=2&IDKey=BEB1F1450F50&HomeUrl=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2%2526Sect2=HITOFF%2526p=1%2526u=%25252Fnetahtml%25252FPTO%25252Fsearch-bool.html%2526r=2%2526f=G%2526l=50%2526co1=AND%2526d=PTXT%2526s1=5,385,127%2526OS=5,385,127%2526RS=5,385,127
Posted by: mki | Sep 7, 2008 10:42:14 AM
I would love to see the Locomotive manufactures find ways to use this technology and then offer retro fit options for the existing locomotives.
The railroads are efficient compared to other transportation options when looking at ton miles per gallon. Even so, railroads are some of the largest private consumers of diesel in North America, and any further efficiency improvements would be a large benefit to all of us. Reduced fuel usage, reduced fuel prices, reduced fuel surcharges imposed by the transportation industry.
Posted by: Rod | Sep 7, 2008 12:56:46 PM
I believe that locomotive manufactures could adopt Delphi injector .
On the other hand railroads in US should choose the same path as other develop countries: electrification of the system. That the most efficient and cleanest way to transport good over very long distance. Such system can be supply by solar energy in the future. Any way the railroad car should have solar panel on the roofs. The boxcar could have up to 60 square meter roof area (20x3m). With 10% efficiency solar panels will give you 6KW at noon and with 20% efficiency 12KW. 10 ton boxcar at 25 mph require 3KW to overcome roiling losses. I am not sure if the loses expand in linear fashion, if yes then for realistic boxcar with 60 tons will need 18KW at 25mph . Such approach could be more suitable for passenger cars as they weight less and cost more so adding additional $48 thousand ($4000 per KW of solar panel) will not brake the bank.
Buy the way the solar energy even with today list efficient solar panels is at list 5-100 time more efficient then any plant base fuel.
I just start reading book by David J.C. MacKay Sustainable Energy - Without the Hot Air. It is analysis of UK capability, however most of the information can be apply to any place on the earth. It is truly eyes opener about what energy is really sustainable on the earth. It is draft – as for now it is free . Find it in there :
http://withouthotair.com/
The book is in draft form
Posted by: mki | Sep 7, 2008 5:25:20 PM
Nice link mki. I'll be sure to read the draft. I've also had similar musings about placing solar panels on the roof of rail cars.
I've also wondered about the practicality of using carbon fiber and/or aluminum in passenger rail cars. They have long life spans and thus the additional cost could be justified as the weight reduction would significantly reduce fuel consumption. For freight, the weight reduction probably wouldn't justify the additional cost as the weight of the car is a fraction of what is being moved.
Posted by: GreenPlease | Sep 7, 2008 7:14:24 PM
GreenPlease:
I believe you were thinking of fuel percent savings and not fuel amount savings.
The fuel amount saved by reducing the weight of a rail car depends upon the miles of usage. The freight weight or passenger weight doesn't change that.
Visualize it for a car or truck. The fuel savings from the lighter vehicle depends upon how far you drive it.
Posted by: K | Sep 8, 2008 2:12:56 AM
@K
You are correct. That was my error.
Posted by: GreenPlease | Sep 8, 2008 5:06:36 AM
I wonder what sort of injection technology is currently used by rail cars...
I also see potential for the use of super conducting motors in the genset to increase power density an, to a lesser extent, efficiency.
Posted by: GreenPlease | Sep 8, 2008 5:16:32 AM
GreenPlease
EMD has been using Interstate Diesel ECOTIP injectors for Union Pacific orders since 2001.
Posted by: | Sep 8, 2008 10:56:59 AM
