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
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.
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
Economic criteria
Vehicle - fix costs: low
Depends on power class and engine charcteristics. In general common rail is a mature technology which is comparable in price to other engines (at least in the automotive sector).
Vehicle - running costs: significant reduction
The reduction of running costs depend on point of reference but is generally considerable. If old engines are replaced, both fuel consumption and maintenance efforts are substantially reduced.
The total diesel-engine-related costs are typically composed as follows (Source: Günther 1998):
Costs for fuel and lubricants: 65 %
Maintanace costs: 15 %
Initial investment: 20 %
This gives an idea of the economic relevance of fuel consumption.
Infrastructure - fix costs: none
(no details available)
Infrastructure - running costs: unchanged
(no details available)
Scale effects: medium
Common rail technology in high power classes is still rare. Therefore certain scale effects are to be expected if appreciable numbers are ordered.
Amortisation: not applicable
Payback times obviously depend on application context. Re-engining measures typically pay off in about 5 years.