Session: 12-02: Hydrogen Energy, Alternative Fuels, Bioenergy, and Biofuels

Paper Number: 130832

130832 - Challenges in the Use of Bio-Hybrid Fuels As Drop-in Fuels 

Abstract: 

Bio-hybrid fuels can be produced based on sustainable raw materials and green energies. This way a closed carbon loop can be realized, and a CO2-neutral production is feasible. Thus, they are a promising alternative to conventional fuels made of mineral oil. Within the cluster of excellence “The Fuel Science Center” funded by funded by Deutsche Forschungsgemeinschaft bio-hybrid fuels are investigated on a holistic level. The cluster's research work includes the development of methods for predicting fuel properties. By using these methods, fuels can be optimized and designed regarding their combustion behavior, their efficiency, and the emission of soot or nitrogen oxide. Therefore, the targeted adjustment of fuel properties represents a further advantage over conventional fuels. An advantage of bio-hybrid fuels over other alternative energy sources, such as fuel cells or electrical energy, is the use of existing infrastructure. If bio-hybrid fuels are used as so called “drop-in fuels”, an extensive network of filling stations and petrochemical industry production sites can be used in many parts of the world. To benefit from the mentioned advantages, material compatibility must be ensured. However, swelling of sealing materials is a major issue since some bio-hybrid fuels lead to a volume increase of more than 200 % and a significant decrease of hardness. Insufficient lubricating properties are responsible for impermissibly high wear in the tribological contacts of injection pumps and injection nozzles. Additionally, deviating fluid mechanical properties influence the injection behavior and contradict the requirements of common fuel standards.

The article is intended to highlight the problems mentioned regarding compatibility and discuss methods for improving the compatibility of bio-hybrid fuels. For this purpose, various measurements were performed for selected bio-hybrid fuels. This includes the determination of fluid-mechanical properties, such as viscosity and density, as well as wear and friction behavior and the filter capability. Regarding sealing compatibility, immersion tests according to ISO 1817 were conducted and the results of a radial shaft seal tribometer are to be evaluated. Based on the fluid mechanical properties the dimensionless measures Reynolds, Weber and Ohnesorge number were calculated to characterize the spray behavior. To assess the lubricity of dynamic seals the wetting parameter penetrativity and spreading coefficient are determined.

Selected bio-hybrid diesel fuels were evaluated. This includes so-called HyFit fuels, which are produced using a Fischer-Tropsch synthesis, and a mixture of methyl ketones derived from a microbiological process were used. Further bio-hybrid fuels investigated are ethyl acetate, 1,3-dioxolane, dimethoxymethane and diethoxymethane. The results will be compared with measurements of conventional diesel fuel and common international diesel standards such as EN 590 and ASTM D 975.

Finally, different methods for the improvement of fuel properties like friction or wear behavior will be discussed. This includes for example blending or adding additives to decrease friction and wear.

Presenting Author: Felix Justin Fischer RWTH Aachen University

Presenting Author Biography: Felix Fischer completed a Bachelor's degree in Physics from 2014 to 2017 and a Master's degree in Theoretical Solid State Physics from 2017 to 2019 at RWTH Aachen University.
Currently, since 2019, he serves as a research associate at the Institute for Fluid Power Drives and Systems at RWTH Aachen University, specializing in Tribology.
As part of the VDMA research grant "Air2H2", Mr. Fischer conducts research on developing and evaluating the leak-tightness of valves used in the hydrogen industry. His research centers around investigating the influence of rough surfaces in seals on valve tightness and longevity.

Authors:

Marius Hofmeister RWTH Aachen University
Felix Justin Fischer RWTH Aachen University
Lukas Boden RWTH Aachen University
Katharina Schmitz RWTH Aachen University