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Common rail

By Annie Walker,2014-09-22 16:10
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Common railrail,Rail,RAIL

Common rail

    Common rail direct fuel injection is a modern variant of direct system for and.On

    diesel engines, it features a high- (over 1,000 or 15,000) feeding individual, as opposed to low-pressure feeding (Pumpe/Düse or pump nozzles). Third-generation common rail diesels now feature injectors for increased precision, with fuel pressures up to 1,800 bar or 26,000 psi.In, it is used in engine technology.

    History

    The common rail system prototype was developed in the late 1960s by Robert Huber of and the technology further developed by Dr. Marco Ganser at the in, later of Ganser-Hydromag AG (est.1995) in. The first successful usage in a production vehicle began in by the mid-1990s. Dr. Shohei Itoh and Masahiko Miyaki of the, a Japanese automotive parts manufacturer, developed the common rail fuel system for heavy duty vehicles and turned it into practical use on their ECD-U2 common-rail system mounted on the and sold for general use in 1995. Denso claims the first commercial high pressure common rail system in 1995.

    Modern common rail systems, whilst working on the same principle, are governed by an (ECU) which opens each injector electronically rather than mechanically. This was extensively prototyped in the 1990s with collaboration between, and. After by the, the design was acquired by the German company for completion of development and refinement for. In hindsight, the sale appeared to be a tactical error for Fiat, as the new technology proved to be highly profitable. The company had little choice but to sell, however, as it was in a poor financial state at the time and lacked the resources to complete development on its own. In 1997 they extended its use for passenger cars. The first passenger car that used the common rail system was the 1997 model 2.4, and later on that same year.Common rail engines have been used in marine and applications for some time. The Cooper-Bessemer GN-8 (circa 1942) is an example of a hydraulically operated common rail diesel engine, also known as a modified common rail.

    Vickers used common rail systems in submarine engines circa 1916.. (opposed-piston heavy marine engines) used a common rail system (from 1921 to 1980) whereby a multi-cylinder reciprocating fuel pump generated a pressure of approximately 600 bar, with the fuel being stored in accumulator bottles. Pressure control was achieved by means of an adjustable pump discharge stroke and a "spill valve". Camshaft-operated mechanical timing valves were used to supply the spring-loaded Brice/CAV/Lucas injectors, which injected through the side of the cylinder into the chamber formed between the pistons. Early engines had a pair of timing cams, one for ahead running and one for astern. Later engines had two injectors per cylinder, and the final series of constant-pressure turbocharged engines were fitted with four injectors per cylinder.

    This system was used for the injection of both diesel oil and heavy fuel oil (600cSt heated to a temperature of approximately 130 ?C).The common rail system is suitable for all types of road cars with diesel engines, ranging from such as the to such as the. Principles:

    Solenoid or valves make possible fine over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel. In order to lower engine, the engine's can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness and vibration, as well as optimising injection timing and quantity for variations in fuel quality, cold starting and so on. Some advanced common rail fuel systems perform as many as five injections per stroke. Common rail engines require very short (< 10

    []second) or no heating-up time at all, dependent on ambient temperature, and produce

    lower engine noise and emissions than older systems.Diesel engines have historically used various forms of fuel injection. Two common types include the unit injection system and the distributor/inline pump systems (See and for more information). While these older systems provided accurate fuel quantity and injection timing control, they were limited by several factors:

    ; They were cam driven, and injection pressure was proportional to engine

    speed. This typically meant that the highest injection pressure could only be

    achieved at the highest engine speed and the maximum achievable injection

    pressure decreased as engine speed decreased. This relationship is true with all

    pumps, even those used on common rail systems; with the unit or distributor

    systems, however, the injection pressure is tied to the instantaneous pressure

    of a single pumping event with no accumulator, and thus the relationship is

    more prominent and troublesome.

    ; They were limited in the number and timing of injection events that could be

    commanded during a single combustion event. While multiple injection events

    are possible with these older systems, it is much more difficult and costly to

    achieve.

    ; For the typical distributor/inline system, the start of injection occurred at a

    pre-determined pressure (often referred to as: pop pressure) and ended at a

    pre-determined pressure. This characteristic resulted from "dummy" injectors

    in the cylinder head which opened and closed at pressures determined by the

    spring preload applied to the plunger in the injector. Once the pressure in the

    injector reached a pre-determined level, the plunger would lift and injection

    would start. In common rail systems, a high-pressure pump stores a reservoir

    of fuel at high pressure up to and above 2,000 bars (29,000 psi). The term

    "common rail" refers to the fact that all of the are supplied by a common fuel

    rail which is nothing more than a pressure accumulator where the fuel is stored

    at high pressure. This accumulator supplies multiple fuel injectors with

    high-pressure fuel. This simplifies the purpose of the high-pressure pump in

    that it only has to maintain a commanded pressure at a target (either

    mechanically or electronically controlled). The fuel injectors are typically

    ECU-controlled. When the fuel injectors are electrically activated, a hydraulic

    valve (consisting of a nozzle and plunger) is mechanically or hydraulically

    opened and fuel is sprayed into the cylinders at the desired pressure. Since the

    fuel pressure energy is stored remotely and the injectors are electrically

    actuated, the injection pressure at the start and end of injection is very near the

    pressure in the accumulator (rail), thus producing a square injection rate. If the

    accumulator, pump and plumbing are sized properly, the injection pressure

    and rate will be the same for each of the multiple injection events. Common rail today

    , , , and (now owned by Continental AG) are the main suppliers of modern common rail systems. The car makers refer to their common rail engines by their own names: ; 's CRS Engines (used in U Truck and E4 Busses)

    ; 's D-engines (also used in the TD4)

    ; 's VCDi (licensed from )

    ; and 's XPI (Developed under joint venture)

    ; CCR ( pump with Injectors)

    ; 's CDI (and on 's vehicles simply as CRD)

    ; 's (, and ) (also branded as MultiJet, JTDm, Ecotec

    CDTi, TiD, TTiD, DDiS, Quadra-Jet)

    ; 's TDCi and

    ; 's i-CTDi & i-DTEC

    ; & 's CRDi

    ; 's which is one of the members of the EF family. Supplier TBD ; 's iTEQ

    ; 's Tier3, Tier4, 4D95 and higher - HPCR series Diesel engines.

    ; 's

    ; 's MZR-CD & Skyactiv-D (1.4 MZ-CD, 1.6 MZ-CD manufactured by joint

    venture /) and earlier DiTD

    ; 's (recently developed family uses next generation 200 MPa (2000 bar)

    injection system))

    ; 's , Infiniti uses dCi engines, but not branded as dCi.

    ; 's CDTI

    ; 's SCDi

    ; 's HDI or (1.4HDI, 1.6 HDI, 2.0 HDI, 2.2 HDI and V6 HDI developed under

    joint venture with )

    ; 's (joint venture with Nissan)

    ; 's XDi (most of these engines are manufactured by )

    ; 's (as of Jan 2008)

; 's DICOR & CR4

    ; 's D-4D & D-Cat

    ; : The 6.0 V12 , 4.2 TDI (V8), 2.7 and 3.0 TDI (V6), 1.6, 2.0 TDI (L4) and 1.2

    TDI (L3) engines featured on current Seat, Skoda, VW and Audi models use

    common rail, as opposed to the earlier engines.

    ; 2.4D and D5 engines (1.6D, 2.0D manufactured by and ), D-serie engines ; "largest reciprocating engine in the world" designed by the manufacturer

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