Bosch is developing a higher pressure version of its modular common-rail fuel injection system—MCRS—for large diesel engines that have high engine speeds, up to 2.2 MW of power, and more than 2.5 liters of displacement per cylinder. Bosch says it is the only company to offer common-rail systems for the entire engine spectrum, from passenger-car and diesel commercial-vehicle engines to large diesel engines.
The MCRS extends all the advantages of common-rail injection technology to diesel engines, which in the marine market are used in cargo ships, ferries, and yachts. With the system, Bosch can help engine manufacturers meet their goals of complying with future emission standards for ship drives. Moreover, the use of common-rail technology cuts fuel consumption in marine engines just as it does elsewhere, offering economic benefits for ship operators.
The Bosch MCRS is a modular common-rail system without the separate high-pressure accumulator that, in conventional systems, provides each injector with fuel. The fuel accumulator volume in the MCRS is integrated instead into the high-pressure pump and the injectors. The injectors themselves are connected to each other via short high-pressure lines. The system is designed so that the pressure at the nozzle is constant and independent of the engine speed. Since there is no separate high-pressure accumulator, the system can be flexibly adapted to different numbers of cylinders, thus making it appropriate for everything from four-cylinder in-line engines to 20-cylinder V engines. The only thing that must be changed is the number of injectors and pump elements.
Each injector is equipped with a solenoid ball valve to allow up to three injections per combustion cycle. The CP9.1 high-pressure in-line piston pump, which is controlled electronically and lubricated with oil, generates pressures of up to 1800 bar for these injections. Depending on the level of performance needed, the CP9.1 can be equipped with anywhere from two to five pump elements. To guarantee reliable operation and a long service life even when fuel quality is inferior, the high-pressure pumps and injectors have an especially solid construction. Appropriate engine control units for the MCRS include the Bosch EDC17 series.
In improving the MCRS common-rail platform to offer injection pressures of up to 2200 bar, Bosch is making it possible to comply with both current and future ship-engine emission standards such as EPA/EU Tier 4 as of 2015 and IMO Tier III as of 2016. The higher-pressure MCRS will be available starting in 2014.