Development of an On-Board Sensor System for Early Identification of Deposit Formations in Fuels Containing Biodiesel

(Fuels Joint Research Group) ... Since the design of the internal combustion engine is always a compromise between stable operation, low emissions and high efficiency, the importance of the three parameters must be determined during development (Figure 1). For example, high operational reliability and high efficiency play a decisive role in aircraft engines. This is where the fuel plays a crucial role, as the influence of the fuel on the combustion can minimise emissions. [5] Sensors for recognising the fuel composition in automobiles are useful in order to reduce emissions in the best possible way.[6]

By recognising the fuel composition and the degree of ageing or oxidation, the engine control device can be set specifically to the fuel present. A sensory fuel detection can also be used to detect regenerative fuels. Because the emissions of the combustion engine are mainly caused by the operation of the automobile (only a small part of the emissions are generated by production), a contribution can be made through regenerative fuel.[7] In combination with tax relief for regenerative fuels, an effective control mechanism can be implemented in the car that documents the use of regenerative fuels. In order to replace fossil fuels in the future, different raw material sources can be used to produce synthetic fuels.[8] This results in fuels that can differ greatly in their chemical composition.[9][33][10] For optimal combustion, the fuel components or the fuel composition must be recognised in the future so that the engine management can be optimally adjusted. Subsidised electromobility is also increasingly influencing electrification in the form of plug-in hybrids. In plug-in hybrids, the advantages of both technologies (electric drive and combustion engine) are combined:

This means that local emission-free driving and a long range can be guaranteed.[11] The short driving cycles in everyday life make it possible to charge the accumulator in a stationary manner from the mains. The short driving cycles mean that the fuel in plug-in hybrid vehicles is exposed to far more critical conditions than before. The fuel remains in the tank for longer, which can lead to changes in the physical and chemical properties of the fuel. Accordingly, the detection of the degree of ageing is an important property for a fuel sensor system.

The first part of the research project presented here discusses a detailed investigation of the ageing of rapeseed oil methyl ester (RME). For the increased use of biodiesel in the future, also in connection with new regenerative fuels, understanding ageing is an important aspect in order to be able to ensure stable fuel formulations. As a result, the ageing of biodiesel in its pure form must be understood and since fuel ageing is not the same for all fuels, the ageing in biodiesel blends must also be examined.

For RME ageing, the investigations presented below aim to answer the following questions:
x What products are produced by fuel ageing?
x What is the mechanism behind the creation of the products?
x What is the development of the individual products over time like?
x Influence of the fuel matrix on ageing behaviour?

The answer to these questions is based on the investigation of fuel ageing with high-resolution mass spectrometry, which describes the different stages of oxidation that increases over the ageing process.

By identifying the structures of ageing products, new insights into the ageing behaviour are presented in the area of the oligomerisation of RME. The second part presents the developed sensor system for recognising the fuel composition and the degree of ageing. In the following, the theoretical basics, the fuels used, the measuring methods and the procedure for evaluating high-resolution mass spectra for the structure identification of the ageing products are presented initially. After that, the results obtained in the course of this research project will then be discussed. READ MORE