@inproceedings{BiedermannMoutamassikKameier2022, author = {Biedermann, Till M. and Moutamassik, Youssef and Kameier, Frank}, title = {Assessment of the Impeller/Volute Relationship of Centrifugal Fans From an Aerodynamic and Aeroacoustic Perspective}, series = {ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition}, volume = {Volume 5: Education; Electric Power; Fans and Blowers}, booktitle = {ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition}, publisher = {American Society of Mechanical Engineers}, doi = {10.1115/GT2022-79389}, year = {2022}, abstract = {Heavy-duty centrifugal fans require high reliability and first-class performance. Besides, extreme conditions and harsh environments are often encountered, such as in the papermaking process, in steel or cement plants or the chemical and petrochemical industry. Therefore, the design of high performance heavy-duty industrial fans requires robust yet efficient solutions. Previous work indicates a high aerodynamic and aeroacoustic sensitivity concerning the specific position of the volute cut-off (tongue). This effect will be further investigated, not by directly changing the orientation of the cutoff, but by varying the position of the impeller relative to a fixed volute casing. The initial evaluation is done through a numerical study of three influencing parameters, which allows the aerodynamic dependencies to be modelled using low-layer artificial networks. Subsequently, extensive experimental studies were carried out to validate the aerodynamic dependencies and also to incorporate information on the aeroacoustic performance. The obtained results show that the operating point represents the key factor in determining the optimal positioning, with qualitatively comparable dependencies found for both tested fans. From an aeroacoustic point of view, the determined optimal configuration does not necessarily coincide with the observed aerodynamic desires, so careful analysis and a reasonable compromise are required, motivating for a multi-objective optimisation process.}, subject = {Ventilator}, language = {en} } @phdthesis{Biedermann2019, author = {Biedermann, Till M.}, title = {Aeroacoustic transfer of leading edge serrations from single aerofoils to low-pressure fan applications}, publisher = {Technische Universit{\"a}t Berlin}, address = {Berlin}, organization = {Technische Univerit{\"a}t Berlin}, doi = {10.14279/depositonce-9075}, school = {Hochschule D{\"u}sseldorf}, pages = {221}, year = {2019}, abstract = {Leading edge serrations are well-known for their aeroacoustic potential in reducing aerofoil-turbulence interaction noise and are also associated with certain aerodynamic advantages. To prepare leading edge serrations for industrial application, two obstacles remain to be addressed. First is a combined analysis of the aeroacoustic and the aerodynamic performance of leading edge serrations to develop optimum designs. Second is the need to examine the transferability of the known effects of leading edge serrations from a single aerofoil to full rotors, which are considered to be the final area of application. This thesis aims to assist in the transfer of a well-investigated aerofoil with serrated leading edges from the rigid to the rotating domain. With this purpose, a single aerofoil type is selected and thoroughly analysed, experimentally and numerically, to generate a reliable data basis for aerodynamic performance and noise reduction capability. Aside from gathering information on the overall performance, the spatial distribution of the noise sources is localised, and the spectral composition of the noise reduction is found to follow a clearly defined scaling law. Aerodynamically, generated vortices are found to be responsible for a complex three-dimensional separation mechanism of the leading edge serrations, causing a delay of stall. The generated data basis is then used to design low-pressure axial fans of minimum complexity by keeping the initially chosen aerofoil type. The experimentally identified noise reduction mechanisms for the serrated axial fans are found to be more diverse than the single aerofoil and highly dependent on the inflow conditions and the operation point of the fan. A highly similar pattern for the spectral scaling of the noise reduction supports the finding that at optimum operation conditions, the previously identified noise reduction mechanisms for the single aerofoils are transferable to the rotating domain. On the other hand, additional aerodynamic mechanisms are found to dominate the noise reduction for the instability region of the fan, also contributing to reduced blade-to-blade interaction effects. Moreover, the blade-tip leakage flow is altered by delaying the development of coherent structures. The next step towards a more general description of the aeroacoustic and aerodynamic dependencies is developing a comprehensive model based on artificial neural networks. This model allows a combined analysis of the aerodynamic and acoustic performance of rotors with serrated leading edges and shows an accurate prediction of the overall performance and the spectral composition of the radiated noise. It also enables the development of multi-objective optima for serration designs and motivates further studies into the generalisability of the observed trends. Furthermore, the developed model represents a feasible tool to create tailored serration designs for maximum efficiency in both aeroacoustics and aerodynamics, contributing to the development of future low-noise fans and rotating machinery.}, language = {en} }