Plenary Lecture

Rotor-Stator Interactions in Centrifugal Diffuser Pumps

Professor F.-K. Benra
University of Duisburg-Essen
Faculty of Engineering Science
Institute of Energy and Environmental Engineering
Chair of Turbomachinery
Lotharstr. 1
47048 Duisburg, Germany

Abstract: The flow in vaned diffuser pumps is dominated by strongly unsteady interactions due to the relative motion and close proximity between the rotating impeller and the stationary diffuser. This phenomenon is known as rotor-stator interaction, resulting in pressure and velocity fluctuations both upstream and downstream. In the past, some research work was conducted to investigate impeller-diffuser interactions both numerically and experimentally. LDV (Laser Doppler Velocimetry) and PIV (Particle Image Velocimetry) were applied to measure the unsteady flow field. Here important work was done for example by Hajem et al., Akhras et al., Sinha et al., and Wuibaut et al.. Some other work was performed to study the pressure fluctuations in the diffuser region. For example, Qin and Tsukamoto calculated pressure fluctuations in the diffuser region by a two-dimensional singularity method. Wang and Tsukamoto developed a two-dimensional vortex method to investigate pressure fluctuations both in the impeller and diffuser regions. Shi and Tsukamoto studied pressure fluctuations in the diffuser region by a CFD code. Furthermore, experiments were conducted to measure pressure fluctuations in centrifugal diffuser pumps by Arndt et al., Furukawa et al., Guo and Maruta. All the above mentioned experimental and numerical investigations contribute to a better understanding of rotor-stator interactions in centrifugal diffuser pumps; however the amount of available data is still not sufficient. Particularly, most research on the unsteady pressure fluctuations has been conducted only in the diffuser region, but less for the impeller region. At the chair of turbomachinery of University Duisburg-Essen recently the unsteady phenomena induced by rotor-stator interactions have been investigated in a centrifugal diffuser pump which had a small specific speed. The pressure and velocity fluctuations and also associated unsteady effects were investigated numerically and experimentally in a wide range of flow rates and for different radial gaps and blade number configurations. Experimental results for some cases were compared with numerical results and discussed in detail, in order to enhance the comprehension of rotor-stator interactions in centrifugal diffuser pumps.

Brief Biography of the speaker:
Dr. Benra graduated with a diploma degree in Mechanical Engineering at University of Duisburg in 1979. Afterwards he worked as a research assistant at the University of Duisburg and obtained his doctoral degree in Mechanical Engineering in the field of Turbomachinery in 1986. From 1986 to 1989 he was chief of the department for design and development of radial compressors at Mannesmann Demag Company and from 1989 to 1993 he was chief of department for research and development of centrifugal pumps at company Pleiger. Since 1993 he is full Professor for Mechanical Engineering at University Duisburg-Essen in the field of Turbomachinery and since 2002 he is the head of the Chair for Turbomachinery at University Duisburg-Essen, Germany. His area of expertise in teaching are: Thermofluid Engineering and Energy Conversion in all kinds of Turbomachines. His current research topics are: Numerical and experimental investigation of time-variant flow in Turbomachines (rotor/stator interaction, fluid/structure interaction, flow along rough or structured surfaces).