Delphi Enters High Volume Production With the World’s First Diesel Fuel Injection System to Use Revolutionary Direct Acting Piezo Injectors
A new generation of diesel injector technology will help vehicle manufacturers meet tough Euro 6 emissions standards while also improving torque, power, fuel economy, refinement and driveability
Paris, France.—Delphi Corp. (Pinksheets: DPHIQ) is launching the next generation of diesel fuel injectors—the Delphi Direct Acting Common Rail system. This launch follows five years of development by Delphi, working closely with its vehicle manufacturer customers to help them address stringent future emissions requirements. The new system is now entering production and will be available on a European production car to be launched later this year.
“I’m very excited and proud today because Delphi is bringing a real product, not a concept, to the market well ahead of competitors,” said Jose Avila, general manager of Delphi Diesel Systems. “Consumers will be able to drive this system on the roads on a premium vehicle before the end of this year,” adds Avila.
In the patented Delphi Direct Acting Common Rail system, the 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 a considerable reduction in emissions, more torque and power across all engine speeds and significantly improved fuel economy and refinement.
“To help address the worldwide pressure on fuel prices and the increasing concerns about global warming, our customers are accelerating the introduction of technologies that reduce fuel consumption and cut emissions of all pollutants, including those that are not regulated,” said Avila.
One of the challenges for diesel engines is to reduce emissions of Nitrogen Oxide (NOx). When Euro 6 is introduced in Europe in 2014, NOx limits will have reduced by a factor of three1 and particulate matter limits by a factor of five2 compared with current Euro 4 levels. In North America, the challenge is even greater as the Tier II bin5 NOx level, already in place, is equivalent to just 43mg/km compared with 250mg/km for today’s Euro 4 and 80mg/km for Euro 6 (although these figures are not absolutely comparable as legislated test cycles in European and the United States are different).
An additional challenge is the current debate, led by Europe but also in Japan and the United States, on the CO2 emission reduction to counteract global warming. Targets for CO2 are today under discussion at a regulatory level (the EU has proposed a very challenging 120g/km target by 2012) while consumers are increasingly taking fuel economy and CO2 emissions into account when making their purchasing decision.
“There is unfortunately a trade-off, as reducing NOx either through in-engine measures or through de-NOx systems, can increase fuel consumption and CO2 emissions,” said Avila. “These challenges have led Delphi to develop a range of new technologies, including the innovative Direct Acting Diesel Common Rail.”
Current injector technologies:
So far, injector technology has been catagorized as either “solenoid” or “piezo.” In both cases, the injector needle is moved via a hydraulic circuit controlled by a valve that is set in motion by an actuator—either a ’solenoid’ device or a ’piezo’ device. This concept is called “servo actuation.”
The servo actuation family can furthermore be split into two categories, referring to the pressures applied on both sides of the valve: one called “balanced” and the other “unbalanced.”
Therefore, the different types of injectors existing so far were:
* servo-solenoid unbalanced valve (first Common Rail type introduced in the market);
* servo-solenoid balanced valve (Delphi’s concept in production)
* 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 much 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 in Delphi’s servo-solenoid balanced valve design, equivalent to unbalanced servo-piezo systems. This means that there are no significant differences in performance between Delphi’s balanced valve servo-solenoid and competitors’ unbalanced servo-piezo systems—making Delphi’s Multec servo solenoid injector the best value solution in the market today, offering equivalent performance to more expensive servo-piezo technologies.
Direct Acting injector:
The new Direct Acting Common Rail from Delphi represents a further radical break-through in diesel injection technology as for the first time the injector needle is directly activated by the piezo stack, removing the hydraulic circuit and its associated lag and energy consumption and providing 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 a patented Direct Acting concept, where the piezo ceramic actuator directly operates the needle valve of the injector for initial lifts, such as those obtained in pilot injections, and a hydraulic amplifier is used to help complete the lift for large injections. The concept eliminates the servo-hydraulic circuit that other common rail injectors use. This allows the injector to spray fuel into a diesel engine combustion chamber faster, with greater accuracy and at higher pressures (up to 2000 bar) and with higher efficiency than current injection technologies.
Piezo injectors use piezoelectric material to produce motion when excited by an electrical voltage. It takes less than 100 microseconds to open and close the needle valve of the injector and spray the high pressure diesel fuel into the engine, allowing seven (or more) injection events per engine cycle. Delphi’s hydraulic circuit design makes best use of the characteristics of piezo ceramic actuators: high force and speed with efficient packaging. “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,” said Delphi Diesel Systems engineering director Dr. Detlev Schoeppe. The injector’s radically new operating principle is also completely leak free, so no high pressure fuel is wasted into a return flow, saving up to one kilowatt of lost energy used by today’s 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 2000 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)
o Capable of zero hydraulic separation between injections
o 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.
Technology benefits: Less emissions, improved fuel economy and more torque and power for greater driving pleasure
* Less 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 percent 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 percent, 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 with the following measures:
o Particulate filters can be reduced in size or, conversely, NOx aftertreatment may be avoided
o In addition, ever increasingly priced precious metals for the oxidation catalysts can be significantly reduced.
* Better fuel consumption: the radically new operating principle of Delphi’s piezo injectors does not require a return flow to operate. Thus 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 2000 bar, fuel cooling is not required. This unique 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 one to two percent fuel consumption improvement with respect to other injector concepts. However, this fuel benefit comes on top of the emission benefit discussed previously. For similar emission levels the fuel consumption benefit jumps to three to five percent 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 2000 bar. This rise in pressure, which represents an increase of over 60 percent with respect to the first common rail systems, helps to increase the engine’s output and torque.
* Fun to drive: 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, which is a remarkable achievement when compared with today’s servo piezo injection systems.
To summarize, the system offers improved injection fuel atomization and speed to help reduce emissions and engine noise, while providing unequalled driving performance. Indeed, the Direct Acting Piezo advantages of higher spray momentum and highly flexible multi-injection make it an ideal choice for the next generation combustion systems (i.e. HCCI or PCCI etc.) as demonstrated in SAE tech paper “A Study of Methods to Lower HC and CO Emissions in Diesel HCCI.”3
Delphi Diesel portfolio: two solutions to better fit customers’ requirements
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.
All key components of both families have been designed in a way that they can easily be interchanged. As such, one can switch from Fast Solenoid to Direct Acting injector technology without having to make any design change to the base engine. Pump and rail can be kept similar, and, having exactly the same packaging for both injector types, they can be interchanged without any changes to the base cylinder head.
The Balanced Valve Fast Servo Solenoid Injector family is capable of system pressures up to 2000 bar. It is based on a unique injector design with balanced servo valve technology. The small size of this actuator allows it to be packaged in-line and in close proximity to the needle providing extremely fast actuation and precise metering.
“The performance is state-of-the-art and exceeds current ’servo-piezo’ injector technologies,” said Avila. “It delivers a unique performance/cost value proposition and a step change in technology that provides considerable potential for further refinement.”
“With the introduction of the Direct Acting diesel Common Rail technology, Delphi is able to deliver the best solution for the customers’ requirements: the Balanced-valve solenoid technology offering high performance, yet cost effective solution for the majority of vehicles and the Direct Acting piezo for very demanding applications that require high fuel flow with exceptional control” said Jose Avila, Delphi Diesel Systems General Manager. Thus “again demonstrating Delphi’s technology leadership in diesel fuel injection technologies,” added Avila.
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