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O+P Fluidtechnik 9/2018

O+P Fluidtechnik 9/2018

FORSCHUNG UND

FORSCHUNG UND ENTWICKLUNG IFAS JUBILÄUM 50 YEARS OF FLUID POWER RESEARCH AT RWTH AACHEN UNIVERSITY – HIGHLIGHTS AND FUTURE CHALLENGES PART 3 – 2010 - TODAY Prof. Dr.-Ing. Hubertus Murrenhoff and Prof. Dr.-Ing. Katharina Schmitz The 11 th IFK 2018 took place from March 19 th through 21 st at the Eurogress in Aachen. During the concluding session on the last day of the event, Prof. Ernst Schmachtenberg, Rector of RWTH Aachen University, conducted the handover of the directorship at ifas. A talk followed with regard to the above title and for all readers of O+P Fluidtechnik that didn’t have the chance to attend the conference, the contents of that presentation are summarized in this three-part-series. This first two parts (published in O+P Fluidtechnik, issues 6 and 7-8, 2018) highlighted the history of the institute starting with its establishment in 1968 by Prof. Wolfgang Backé till 2009. The following chapter deals with exemplary research highlights of our current decade. Finally, an outlook on the future research contents will conclude this comprehensive review of the institute‘s history. 36 O+P Fluidtechnik 9/2018

IFAS JUBILÄUM 5 TH DECADE – THE 2010 TH The fifth decade brings us to three examples of most recent research achievements and delivers a smooth transition to the new period under the future direction of Prof. Katharina Schmitz. Based on the knowledge gained through the collaborative research center SFB 442 ifas qualified to join the cluster of excellence (CoE) called “Tailor Made Fuels from Biomass (TMFB)”. Goal of the cluster is an interdisciplinary research approach towards new synthetic fuels based on biomass feedstock researching applicable synthesis pathways and production processes and at the same time preparing the combustion process, the engines and the fuel injection for these new fuels. With different fuel characteristics the unknown properties need to be determined by experiments and all applicable tribological attributes must be researched. This was and still is the task of ifas within the CoE. Therefore high pressure rheometer and specific tribological test set ups had to be designed determining properties needed by the interdisciplinary scientists in the cluster. Regarding pumping and injecting characteristics it was important to research lubrication and wear in realistic models and hardware near to real high pressure pumps. Fig. 1 provides examples of the related research. On the left hand side an HFRR wear tester is depicted. A small ball is weight loaded and moved with a set frequency across a surface. This way a wear scar remains and the dimension is documented. An analytical approach was developed together with Prof. Leonhard, LTT of RWTH Aachen University, using a QSPR model where lubrication and wear properties are deduced from simulated quantummechanical molecule properties. A comparison to measurements showed a good correlation with pure fuels. On the right hand side a developed hollow piston of a high pressure pump is shown. It enables sufficient volumetric efficiencies even for low viscosity fuels at high pumping pressures. Along the way four dissertations were accomplished, and more information is available studying those and all the references in the theses. The next example is selected because it closes the loop regarding the development of secondary controls. One can say that it took more than 3 decades of first research into the subject until it founds its way into an application with significant fuel improvements. The basic circuit developed is displayed in the upper left part of Fig. 2 following a holistic approach for fuel efficiency using a balance including the diesel engine in it. It uses impressed pressure nets with a medium and high pressure rail 01 and the necessary reservoir pressure rail. The basic idea is to operate the combustion engine all the time in its sweet point at low speed and high load torque as depicted in the lower part where it is compared to the LS situation. When no energy is needed at the shaft the engine decelerates to idle or off modus depending on the cycle performed. In order to achieve almost constant high torque the pump is at full stroke charging the medium pressure rail and at part stroke charging the high pressure rail. The boxes include valve connections that allow independent metering and the best suited pressure on both chambers of the differential cylinders. An alternative would be a single pressure rail using digital cylin­ ders. But here the hardware is very expensive and the cylinder design becomes awkward. In typical cycles only a few switches between pressure nets are necessary. It would take too much space to elaborate more on the subject here so it is recommended to study the dissertations referenced in Fig. 2 with its entire links to further research and publications. The 18 to study excavator of Volvo showed a measured improvement of 30+% driving a 90 degree dig and dump cycle. ifas was awarded the 2nd prize at the 2016 Bauma in Munich for research and the 2 nd prize of the project financing ministry within the VIP program. The final example deals with research into dynamic sealing. Here ifas was successful in obtaining a DFG Koselleck grant for high risk research. ifas collaborates on the subject with Dr. Bo Persson of the PGI (Peter Grünberg Institute) within FZ Jülich. The basic research idea is displayed in Fig. 3. The fluid power discipline concentrates on the macroscopic part with test runs and EHD simulation. At PGI the research deals with fundamental tribological science developing an involved contact model that allows describing even dynamic changes in the contact during movement. It is a true interdisciplinary approach and unique by the application of a contact model that was developed for the tire concrete contact for formula 1 racing cars. The model covers multiple length and time scales and it is possible to visualize the height build up in the gap between an elastomer seal and its steel counterpart with a rough surface depending on manufacturing technology. A snap shot of such an application is taken from a video sequence in the lower left part. During acceleration the responding gap can be analyzed. For static performances as a precondition it was possible to achieve a good correla tion between simulation and experiment as displayed in the right characteristic. Again it would be too involved to elaborate it here in more detail so it is recommended to study the literature of Julian Angerhausen, working on his dissertation on the project, and Dr. Bo Persson. References are available on the ifas homepage. FUTURE CHALLENGES As it can be seen from the last 5 decades, every time sets new requirements and research focuses follow these demands. To meet the challenges of today, the research focus at ifas has been adapted and the research groups of the institute have been reorganized. Tribological tests within the excellence cluster TMFB O+P Fluidtechnik 9/2018 37

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