24th International Colloquium Tribology - January 2024 29 Supporting Mobility Transition - Alternative Energy Carriers in Tribology Marcella Frauscher 1* , Adam Agocs 1 , Charlotte Besser 1 , Michael Adler 1 , Hannes Hick 2 1 AC2T research GmbH, Wiener Neustadt, Austria 2 Institute for Machine Components, University of Technology Graz, Austria * Corresponding author: marcella.frauscher@ac2t.at 1. Introduction Figure 1: Lab-to-field approach combining artificial ageing and identification of lubricant degradation (e.g., via MS and sensors) to understand the impact of alternative energy carriers on lubricant performance. In addition to e-mobility, which is seen as most promising future technique for passenger cars, fuels with zero-carbon emissions are necessary within the next years or in applications where e-mobility cannot be (easily) realised such as aviation, marine transport, and off-road vehicles. Besides carbon-based fuels from synthetic sources (synfuels), hydrogen and ammonia are considered as emerging sustainable fuels. While the influence on emissions of internal combustion engines was investigated in scientific studies, their impact on lubricants and engine components, and consequently friction and wear are not yet analysed in detail. For this purpose, the so-called Lab-to-Field approach (see figure 1) combines techniques such as artificial ageing and mass spectrometry to investigate the influence of alternative energy carriers on lubricant degradation, lubricant condition, and its influence on lubrication performance [1, 2]. In this presentation, the tribological challenges of alternative energy carriers will be discussed by means of selected examples of synthetic fuels, ammonia and hydrogen. 2. Alternative energy carriers in tribology 2.1 Synthetic fuels To determinate the impact of synfuels on engine components as well as on the friction and wear behavior a fundamental analysis of their application in existing passenger car fleets utilizing a turbo charged single cylinder engine was performed. Periodical oil sampling was done, and oil analysis consisted, amongst others, of fourier-transformed infrared spectroscopy (FTIR) to characterize the degradation of antioxidant and anti-wear additives. Gas chromatography (GC) was applied to measure the accumulation of fuel components in the lubricant. This revealed a higher impact on viscosity due to dilution for the investigated experimental synthetic fuels compared to a conventional fuel. High-resolution mass spectrometry (MS) characterized additive depletion and degradation products on the molecular level, and, hence, the influence of synthetic components, showing remarkable effects on the lubricant. Based on this comprehensive study including tribometry and lubricant condition, new effects of synthetic blends on engine mechanics can be observed, which sup- 30 24th International Colloquium Tribology - January 2024 Supporting Mobility Transition - Alternative Energy Carriers in Tribology ports optimization of fuel and lubricant composition in terms of friction and wear [3]. 2.2 Ammonia based fuels The application of ammonia as prospective zero-carbon emission fuel for use in large marine diesel engines inhibits challenges regarding stability of engine oil and engine components. Thus, a methodology to evaluate this phenomenon was proposed based on an artificial oil alteration (see figure 2) [4,5]. Subsequently, performance tests with the altered oils focussed on corrosion properties, deposit formation, and load-bearing capability. It was shown the application of ammonia resulted in less pronounced thermo-oxidative degradation compared to alterations with air. However, static and dynamic de-posit formation as well as corrosion properties and load-bearing capability were severely impacted by the presence of ammonia [5]. Figure 2. Schematic set-up of artificial ageing under ammoniac atmosphere to determine the influence on engine oil. 2.3 Hydrogen In terms of H2 as energy carrier in mobility, the supply chain is one of the main challenges. For compression, high pressure equipment is needed, which enables easier liquification. However, effects of the pressurised gas and H2-oil interactions must be considered. To exert hydrostatic pressure of up to 1000 bar on hydrogen, a lubricant must fulfil a set of critical requirements such as limited solubility of hydrogen in the fluid. For assessment of the solubility of hydrogen in a potential fluid for high pressure storage, an in-house test rig at AC2T research GmbH was utilized, designed to evaluate the physisorption of gases into fluids at pressures up to 100 bar. Tribological performance was measured using a rheometer with a ball-on-three-pins setup. Promising lubricants from sustainable sources were tested in comparison with conventional ones, and gas absorption was found to be almost negligible [6]. 3. Conclusion Based on the comprehensive Lab-to-Field approach, effects of carbon-free or synthetic fuel blends on lubricants and tribological performance are investigated. The presented examples show how advanced stability assessment and tribotests together with advanced analytical methods lead to deep knowledge used to push investigations on alternative energy carriers and modern lubricant design [7]. Acknowledgements The work presented was funded by the Austrian COMET program (Project InTribology, Nr. 872176) and carried out at the “Excellence Centre of Tribology” (AC2T research GmbH). References [1] Engine oils in the field - comprehensive chemical assessment of engine oil degradation in a passenger car. Dörr N.,-Agocs A.,-Besser C.,-Ristic A.,-Frauscher M. Tribology Letters, Vol 67, Art.Nr. 68. 2019 [2] Improving sustainability by enhanced engine component lifetime through friction modifier additives in fuels. Frauscher M., Agocs A., Wopelka T., Ristic A., Ronai B., Holub F., Payer W. Fuel - The Science and Technology of Fuel and Energy, Vol 358, 130102. 2023 [3] The influence of synthetic fuels on tribology in engine operation. Hick H., Frauscher M., Kopsch P., Agocs A., Plettenberg M., Gell J. European Conference on Tribology 2023 Bari (IT) [4] Generation of engine oils with defined degree of degradation by means of a large scale artificial alteration method. Besser C., Agocs A., Ronai B., Ristic A., Repka M., Jankes E., McAleese C., Dörr N. Tribology International, Vol 132, p 39-49. 2018 [5] The impact of ammonia fuel on marine engine lubrication: An artificial lubricant ageing approach. Agocs A., Rappo M., Obrecht N., Schneidhofer C., Frauscher M., Besser C. Lubricants, Vol 11, 165. 2023 [6] Innovative lubricant solutions for high-pressure hydrogen systems. Adler M., Nagl C., Eder R.M. European Conference on Tribology 2023 Bari (IT) [7] Assessment and design of modern lubricants supported by mass spectrometry. Frauscher M. European Conference on Tribology 2023 Bari (IT)