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Common Rail

evaluated

Whereas in conventional diesel engines injection pressure is generated for each injector individually, a common rail engine stores the fuel under high pressure in a central container ("common rail") and delivers it to the individual injectors on demand. Benefits of common rail injection are reduced noise levels, stronger performance, improved emission control and greater efficiency.

Technology field: Optimisation of traction technologies



General information

	Description

General criteria

	Status of development: in use
		Diesel engines using common rail injection are available in the power classes needed for railway applications but are still rare in railway fleets. At DB AG, common rail engines are integrated into 400 old shunting locomotives as part of a re-engining programme.

	Time horizon for broad application: 5 - 10 years
		Given the long life-time of rail vehicles, diffusion of common rail engines into rolling stock will be slow. In addition, invitations for tender are usually functional, i.e. they only specify fuel consumption and emission limits but leave it to manufacturers to realise these targets. So in principle there is no bias for common rail technology on the part of railways.

	Expected technological development: dynamic
		cf. Application outside railway sector - Expected technological development outside railway sector

	Motivation:
		High power and torque Emission control Reduced noise emission Low fuel consumption

	Benefits (other than environmental): big
		Power and torque Especially at low speeds common rail systems yield higher engine torques than conventional injection systems. Noise Reduced noise and vibration. Reliability and engine life Constant pressure supply in injection systems puts less stress on material than conventional systems. This leads to longer engine life.

	Barriers: low
		(no details available)

	Success factors:
		(no details available)

	Applicability for railway segments: medium
	Type of traction: diesel
	Type of transportation: passenger - main lines, passenger - regional lines, passenger - suburban lines, freight
		In principle, common rail technology can be used on diesel vehicles of all power classes.

	Grade of diffusion into railway markets:
	Diffusion into relevant segment of fleet: < 5%
	Share of newly purchased stock: (no data)
		(no details available)

	Market potential (railways): medium
		Most railways do not plan to pull out of diesel traction in the next decades. So there will be a market for modern diesel technologies in power classes suited for railways even in long-term perspective.

	Example:
		DB re-engining programme As a part of their re-engining programme German DB AG is currently replacing the engines of 400 old shunting locomotives by common rail engines.

Environmental criteria

	Impacts on energy efficiency:
	Energy efficiency potential for single vehicle: > 10%
	Energy efficiency potential throughout fleet: 1 - 2%

	Other environmental impacts: positive

Economic criteria

Application outside railway sector

	Status of development outside railway sector: in use
		Major automotive manufacturers offer vehicles equipped with common rail technology (e.g. Mercedes Vito CDI).

	Time horizon for broad application outside railway sector: now
		(no details available)

	Expected technological development outside railway sector: dynamic
		There is intensive R&D in industry on the optimisation of the common rail injection system. An example for the development potential of the technology is the development of piezoelectronic actuators at Siemens VDO. As these switching elements operate much faster than conventional solenoid valves, it will be possible in the future to split the fuel volume into several individual injections: Two pre-injections with very small volumes of fuel are followed by the main injection and, if necessary, two smaller post-injections. While the pre-injections serve primarily to build up the pressure in the combustion chamber evenly and thus reduce the noise of combustion, the post-injections are provided for post-treatment of the exhaust gas. Fuel economy will also be increased. Piezoelectronic actuators exploit the behavior of piezoelectric crystals. If an electric charge is connected to such a crystal, the crystal lattice reacts within a few milliseconds by expanding. When discharged the material returns to its original size.

	Market potential outside railway sector: high
		By 2004, 70% of new diesel vehicles will incorporate Common Rail injection systems and 5 million such systems will already be on the road, according to Delphi Diesel Aftermarket.

Overall rating

	Overall potential: very promising
	Time horizon: mid-term