In view of the fact that subsidies supporting diesel fuel for agricultural applications have been reduced since the beginning of 2005 the interest in tractor engines, which can be operated with alternative fuels, has been increasing in Germany. DEUTZ has continuously further developed its engine range with particular emphasis on these requirements. Contrary to diesel fuels, however, bio-fuels (vegetable oils) feature a completely different molecular structure involving combustion process problems in the engine. Pure vegetable oils are usable therefore only in a few engines. Only through chemical conversion to methyl esters can these oils be more easily burnt in the diesel engine. A typical bio-fuel of this type is rape oil methyl ester (RME).
Most compact engines supplied by DEUTZ are approved for operation with RME according to European standard EN 14214. At present this applies, however, only up to exhaust emission standard level 2. To make the engines fit for operation with RME, the company prepared relevant service kits. A brochure provides information about the mayor aspects.
To ensure reliable operation with this bio-diesel, the engine user has to observe some restrictions. This includes among other things:
- The mean engine load must not exceed 80 %.
- The oil change intervals, mostly 500 hours, are to be halved.
- Rubber hoses and diaphragms of fuel pumps (if any) are to be replaced yearly.
- Following the initial switchover to bio-diesel the fuel filter is to exchange after 30 to 50 running hours.
- Downtimes in excess of four weeks are to be avoided. Otherwise, prior conversion of the engine to diesel fuel operation is mandatory.
These restrictions apply to all admixtures of bio-diesel to diesel fuel above 5 %. For practical use, it is very important to carefully select the relevant fuel supplier as the limits specified by
EN 14214 must be guaranteed and in case of any damage attributable to inadequate fuel the engine manufacturer cannot take over any warranty.
As the calorific value of RME is lower than that of diesel fuel a 5 to 7 % lower rated power must be expected during operation, which must not be compensated by up-fuelling the engine. The lower calorific value increases fuel consumption by 7 to 10 %. The nitrogen oxide emission of the engines increases by about 10 %, whereas the particulate emission is reduced by 50 %.
The field testing department of DEUTZ has attended to several engine installations running on RME. Successful operating results can be reported on the whole. Furthermore, there exists a research report on 1012 and 1013 series engines according to which the engines have run reliably during many thousands of hours over more than four years.
In view of the different molecular structure of pure vegetable oils DEUTZ has only approved swirl-chamber engines for the use with these fuels. To guarantee safe and reliable operation with rape seed oil according to the standard DIN V 51605, it is necessary to start the engine with diesel fuel and than switch over to rape seed oil after some minutes. This procedure must be repeated vice versa before the engine is shut down. The relevant equipment must therefore be provided with a dual-tank system. It is also necessary to shift over to diesel fuel under extended idling and low-load conditions. Beyond that, operation at low ambient temperatures requires fuel pre-heating. To make up for the poor ignition quality of this fuel trouble-free operation needs an electronic injection system. Due to the ingress of fuel into the lube oil and possible coking of injectors increased service input will be inevitable.
As several retrofitters offer also for direct injection engines conversions for operation with rape seed oil, DEUTZ expressly points out herewith that no approvals have been given for these engines and that their warranty will expire in such case.
To all those interested in alternative fuels DEUTZ can offer solutions which have proved their worth under tough operating conditions. Successful operation necessitates, however, that the required service jobs are carried out professionally. In such a case the use of alternative fuels will pay, both for the user and the environment.
