Quote:
Originally Posted by tsk1979 It was actually invented by bosch I think. |
Sir, Bosch is by no means the first to employ common-rail technology.
The 1942 Cooper-Bessemer GN-8 marine engine, developing 700 bhp (1200 shaft horse-power) had a hydraulically operated common rail diesel engine.
In the late 1960s, Mr. Hiber of Switzerland developed a common rail system prototype for research. At the Swiss Federal Institute of Technology, Mr. Ganser focused on Hiber's research and developed the technology further.
In 1995, Denso Corp., Japan developed the Common Rail Fuel System. Its first practical use was on the 1995 Hino Raising Ranger truck. They called theiir CRDi system: ECD-U2.
It was as late as 1997, when Bosch extended its use for passenger cars.
A little background and how it works
(for those interested)
As you know most old diesel engines have something called an injection-pump with a selector valve. This may be reciprocating or rotary. The old diesel engines had simple, flat-top pistons. They had a noisy clatter to them. They used indirect injection and bulky diesel injectors (nothing more than nozzles at the end of high pressure pipes).
Modern diesel engines are usually direct injection.
The pistons have a depressed bowl in the top surface. They also use a high pressure fuel supply line.
There are two kinds of direct injection,
CRDi and
UDi (Unit direct injection).
Unit Direct Injection
In a UDi system each cylinder has its own injector-pump combo. This prevents pressure fluctuations and produces smoother quieter running. UDi engines are used in Volkswagen diesels as well as big bulldozer diesel engines.
Volkswagen's unique Pumpe Düse (meaning 'pump injector') beats the usual diesel pressure loss in the fuel pipes.
Each cylinder has its own Pumpe Düse (integrated injector and pump) unit mounted in the cylinder head. The Pumpe Düse is operated by the camshaft, injecting fuel directly into the combustion chamber at pressures up to 2,069 bar (207 MPa) - 30,000 psi.
The result: efficiently blended mixture, precise control of fuel quantity and injection timings, higher fuel economy, reduced emissions, higher torque and petrol-engine-like silent running!
Common Rail Direct Injection
Even in Common Rail Direct Injection, Alfa Romeo (Fiat subsidiary) beat Bosch. Alfa were first to use the common rail technology which they called
MultiJet.
In common rail systems, an extremely high pressure pump fills the
common rail (a tubular reservoir of fuel) at high pressure - up to 1,800 bar (180 MPa) - 26,100 psi!
The common rail, in turn, routes diesel to computer-controlled injector valves.
Each valve contains a precision-machined nozzle and a solenoid driven plunger.
The embedded ECU computer calculates how much fuel to send to the pump and operates the valves to decide the precise moment when fuel is injected into the cylinder. It also controls the diesel injection pressure into the cylinders.
The result: injected diesel atomizes easily and burns efficiently with low emissions.
A high-tech ECU computer can also pre-inject a small amount of diesel ("pilot" injection). This reduces noise and vibration and optimizes injection timing and quantity for variations in diesel quality, cold temperature, etc.