EAAT supplies TU Darmstadt with active magnetic bearings for experimental testing of pump systems
Since the company was founded, EAAT has been supplying its customers with tailor-made active magnetic bearing systems, both for research tasks and for industrial use, including now the TU Darmstadt. The Chair of Fluid Systems research into acoustics, vibrations, cavitation and tribology in order to bring targeted product innovations in the field of highly flexible pump systems to the market. To this end, the scientists rely on EAAT's active magnetic bearing technology.
The goal of developing highly flexible pump systems is to meet the increasing demands on pumps under highly variable operating conditions. These conditions include high pressure ratios, temperature fluctuations, and varying flow rates, as encountered, for example, in steam power plants (water-steam cycle, cooling cycle, as well as upstream and downstream process cycles) or in chemical and process engineering applications. The focus is on enhancing the flexibility of these systems while simultaneously improving their partial load efficiency and extending their service life. These requirements are addressed by developing pumps with an extended partial-load operating range, higher load gradients, and improved efficiency in partial-load conditions. Such systems are essential, particularly for flexible combined-cycle power plants, solar-powered steam power plants, and various industrial processes.
A central challenge in centrifugal pumps is the axial thrust on the rotor generated by the pressure increase, which can be particularly pronounced in multistage pumps. Axial thrust balancing devices are employed to relieve the axial bearings and reduce wear. These devices typically consist of a combination of axially and radially flowing gaps (axial throttle path, radial gap, and axial gap). These measures reduce the load on the axial bearing, allow for smaller bearing dimensions, and minimize wear. However, the influence of such balancing devices on the pump's rotor dynamics remains largely unexplored. To characterize this influence, the devices are modeled using mechanical elements such as stiffness, damping, and inertia, with parameters identified through complex flow simulations or experimental investigations.
For the experimental investigation of the dynamic properties, it is necessary to precisely excite the rotor in the annular gap with a defined amplitude and circular frequency. Both the imposed motions and the resulting forces and moments on the rotor must be measured. Active magnetic bearings are an ideal tool for this purpose, as they enable precise and controlled excitation. In the current project, new magnetic bearings are being developed and implemented to replace the outdated system previously in use. The new bearings are characterized by their significantly improved performance in terms of static and dynamic forces, as well as an enlarged air gap between the rotor and stator within the magnetic bearings. This larger air gap allows for greater tilting of the shaft within the axial thrust balancing devices during operation, enabling a detailed investigation of its impact on rotor dynamics. Additionally, a multifrequency excitation system has been integrated, significantly reducing measurement times