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Analysis of Tonal Noise Generating Mechanisms in Low-Speed Axial-Flow Fans

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Journal of Thermal Science 2016年第4期25卷 302-311页

作者： Edward Canepa Andrea Cattanei Fabio Mazzocut Zecchin dime-universita di genova via montallegro 1 1-16145 Genoa Italy

The present paper reports a comparison of experimental SPL spectral data related to the tonal noise generated by axial-flow fans.A nine blade rotor has been operated at free discharge conditions and in four geometrical configurations in which different kinds of tonal noise generating mechanisms are present:large-scale inlet turbulent structures,tip-gap flow,turbulent wakes,and rotor-stator *** measurements have been taken in a hemi-anechoic chamber at constant rotational speed and,in order to vary the acoustic source strength,during low angular acceleration,linear speed *** order to avoid erroneous quantitative evaluations if the acoustic propagation effects are not considered,the acoustic response functions of the different test configurations have been computed by means of the spectral decomposition ***,the properties of the tonal noise generating mechanisms have been *** this aim,the constant-Strouhal number SPL,obtained by means of measurements taken during the speed ramps,have been compared with the propagation ***,the analysis of the phase of the acoustic pressure has allowed to distinguish between random and deterministic tonal noise generating mechanisms and to collect information about the presence of important propagation effects.

关键词： Axial-flow fans Tonal noise Acoustic response

Experimental Investigation of Flow Instabilities in a Laminar Separation Bubble

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Journal of Thermal Science 2014年第3期23卷 203-214页

作者： Simoni D. Ubaldi M. Zunino P. dime-Università di genovavia montallegro 1 I-16145 Genova Italy dime-Università di genova Via Montallegro 1 I-16145 Genova Italy

The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large scale co- herent structures generated as a consequence of the Kelvin-Helmholtz instability process. Measurements have been performed along a fiat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble at low Reynolds number condition. Measurements have been carried out by means of comple- mentary techniques： hot-wire （HW） anemometry, Laser Doppler Velocirnetry （LDV） and Particle Image Veloci- metry （PIV）. The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the separated flow region, while the high frequency response of the HW anemometer allows analyzing the amplification process of flow oscillations induced by instability mechanisms. PIV results complement the flow field analysis providing information on the generation and evolu- tion of the large scale coherent structures shed as a consequence of the separated shear layer roll-up, through in- stantaneous velocity vector maps. The simultaneous analysis of the data obtained by means of the different meas- uring techniques allows an in depth view of the instability mechanisms involved in the transition/reattachrnent processes of the separated shear layer.

关键词： Ultra-High-Lift turbine profiles separated flow transition mode streaks Kelvin-Helmholtz instabil- ity linear stability theory

Design of Off-statistics Axial-flow Fans by Means of Vortex Law Optimization

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Journal of Thermal Science 2014年第6期23卷 505-515页

作者： Andrea Lazari Andrea Cattanei dime-Università degli Studi di genova Via Montallegro 1I-16145 GenovaItaly Presently with FPZ S.p.A. Via Fratelli Cervi16I-20863ConcorezzoItaly

Off-statistics input data sets are common in axial-flow fans design and may easily result in some violation of the requirements of a good aerodynamic blade *** order to circumvent this problem,in the present paper,a solution to the radial equilibrium equation is found which minimizes the outlet kinetic energy and fulfills the aerodynamic constraints,thus ensuring that the resulting blade has acceptable aerodynamic *** presented method is based on the optimization of a three-parameters vortex law and of the meridional channel *** aerodynamic quantities to be employed as constraints are individuated and their suitable ranges of variation are *** method is validated by means of a design with critical input data values and CFD ***,by means of systematic computations with different input data sets,some correlations and charts are obtained which are analogous to classic correlations based on statistical investigations on existing *** new correlations help size a fan of given characteristics as well as study the feasibility of a given design.

关键词： axial flow fan statistical correlations optimum design feasibility study

Aerodynamic Loading distribution Effects on the Overall Performance of Ultra-High-Lift LP Turbine Cascades

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Journal of Thermal Science 2014年第1期23卷 1-12页

作者： M.Berrino F.Satta D.Simoni M.Ubaldi P.Zunino F.Bertini dime Università degli Studi di genova Via Montallegro 1I-16145 GenovaItaly Avio S.p.A. Professors I Maggio 56I-10040 Rivalta (TO) Italy

The present paper reports the results of an experimental investigation aimed at comparing aerodynamic perform- ance of three low-pressure turbine cascades for several Reynolds numbers under steady and unsteady inflows. This study is focused on finding design criteria useful to reduce both profile and secondary losses in the aero-engine LP turbine for the different flight conditions. The baseline blade cascade, characterized by a standard aerodynamic loading （Zw=1.03）, has been compared with two Ultra-High-Lift profiles with the same Zweifel number （Zw=1.3 for both cascades）, but different velocity peak positions, leading to front and mid-loaded blade cascade configurations. The aerodynamic flow fields downstream of the cascades have been experimentally in- vestigated for Reynolds numbers in the range 70000〈Re〈300000, where lower and upper limits are typical of cruise and take-off/landing conditions, respectively. The effects induced by the incoming wakes at the reduced frequency ./＋=0.62 on both profile and secondary flow losses for the three different cascade designs have been studied. Total pressure and velocity distributions have been measured by means of a miniaturized 5-hole probe in a tangential plane downstream of the cascade for both inflow conditions. The analysis of the results allows the evaluation of the aerodynamic performance of the blade cascades in terms of profile and secondary losses and the understanding of the effects of loading distribution and Zweifel number on secondary flows. When operating un- der unsteady inflow, contrarily to the steady case, the mid-loaded cascade has been found to be characterized by the lowest profile and secondary losses, making it the most attractive solution for the design of blades working in real conditions where unsteady inflow effects are present.

关键词： Low-Pressure Turbine Ultra-High-Lift Prof'des Profile Losses Secondary Losses Mid-Loaded Blade Cascades Aft-Loaded Blade Cascades.

Profile and Secondary Flow Losses in a High-Lift LPT Blade Cascade at different Reynolds Numbers under Steady and Unsteady Inflow Conditions

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Journal of Thermal Science 2012年第6期21卷 483-491页

作者： Satta F. Simoni D. Ubaldi M. Zunino P. Bertini F. diMSET-Università di genova Via Montallegro 1I-16145 GenovaItaly Avio S.p.A. Viale I Maggio 56I-10040 Rivalta(TO)-Italy

The aerodynamic flow field downstream of a Low-Pressure High-Lift(HL)turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the cascade performance under real engine operating *** Reynolds number has been varied in the range 100000ding conditions,*** effects induced by the incoming wakes at the reduced frequency f+=0.62 on both profile and secondary flow losses have been *** pressure,velocity and secondary kinetic energy distributions at the downstream tangential plane have been measured by means of a miniaturized 5-hole *** quantities provide information on both blade wake and secondary flow structures(passage and horse-shoe vortices).The analysis of the results allows the evaluation of the aerodynamic performance of the HL front-loaded blade in terms of both profile and secondary losses.

关键词： profile losses secondary flow losses high-lift profdes unsteady inflow LPT blade.

Experimental Investigation of Separation and Transition Processes on a High-Lift Low-Pressure Turbine Profile Under Steady and Unsteady Inflow at Low Reynolds Number

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Journal of Thermal Science 2010年第1期19卷 26-33页

作者： Satta F Simoni D Ubaldi M Zunino P Bertini F diMSET-Università di genova Via Montallegro 1I-16145 GenovaItaly Avio R&D V.I Maggio99 I-10040 Rivalta(TO)-Italy

The effects induced by the presence of incoming wakes on the boundary layer developing over a high-lift low-pressure turbine profile have been investigated in a linear cascade at *** tested Reynolds number is 70000,typical of the cruise operating *** results of the investigations performed under steady and unsteady inflow conditions are *** unsteady investigations have been performed at the reduced frequency of f+=0.62,representative of the real engine operating *** aerodynamic loadings as well as boundary layer velocity profiles have been measured to survey the separation and transition *** analysis has been also performed to better understand the phenomena associated with the transition process under steady *** the unsteady case,a phase-locked ensemble averaging technique has been employed to reconstruct the time-resolved boundary layer velocity distributions from the hot-wire instantaneous signal *** ensemble-averaging technique allowed a detailed analysis of the effects induced by incoming wakes-boundary layer interaction in separation ***-resolved results are presented in terms of mean velocity and unresolved unsteadiness time-space plots.

关键词： boundary layer separation boundary layer transition wake-boundary layer interaction high-liftprofile low-pressure turbine

Three-dimensional Fluid-Structure Interaction Case Study on Cubical Fluid Cavity with Flexible Bottom

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Journal of Marine Science and Application 2017年第4期16卷 382-394页

作者： Stefano Ghelardi Cesare Rizzo diego Villa diTEN - Polo Navale Università degli Studi di Genova via Montallegro Genova 1 I-16145 Italy

In this paper, we report our study on a numerical fluid-structure interaction problem originally presented by Mok et al.(2001) in two dimensions and later studied in three dimensions by Valdés Vazquez(2007), Lombardi(2012), and Trimarchi(2012). We focus on a 3D test case in which we evaluated the sensitivity of several input parameters on the fluid and structural results. In particular, this analysis provides a starting point from which we can look deeper into specific aspects of these simulations and analyze more realistic cases, e.g., in sails design. In this study, using the commercial software AdiNATM, we addressed a well-known unsteadiness problem comprising a square box representing the fluid domain with a flexible bottom modeled with structural shell elements. We compared data from previously published work whose authors used the same numerical approach, i.e., a partitioned approach coupling a finite volume solver(for the fluid domain) and a finite element solver(for the solid domain). Specifically, we established several benchmarks and made comparisons with respect to fluid and solid meshes, structural element types, and structural damping, as well as solution algorithms. Moreover, we compared our method with a monolithic finite element solution method. Our comparisons of new and old results provide an outline of best practices for such simulations.

关键词： fluid-structure interaction benchmark finite volume method finite element method partitioned monolithic AdiNA^(TM)

Combined Experimental and Numerical Investigations on the Roughness Effects on the Aerodynamic Performances of LPT Blades

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Journal of Thermal Science 2016年第1期25卷 32-42页

作者： Marco Berrino Fabio Bigoni Daniele Simoni Matteo Giovannini Michele Marconcini Roberto Pacciani Francesco Bertini dime-universita di genova Via Montallegro116145GenovaItaly diEF-universita di Firenze Via Santa Marta350139FirenzeItaly GE Avio R&D Via I Maggio9910140Rivalta(TO)Italy

The aerodynamic performance of a high-load low-pressure turbine blade cascade has been analyzed for three different distributed surface roughness levels(Ra) for steady and unsteady inflows. Results from CFD simulations and experiments are presented for two different Reynolds numbers(300000 and 70000 representative of take-off and cruise conditions, respectively) in order to evaluate the roughness effects for two typical operating conditions. Computational fluid dynamics has been used to support and interpret experimental results, analyzing in detail the flow field on the blade surface and evaluating the non-dimensional local roughness parameters, further contributing to understand how and where roughness have some influence on the aerodynamic performance of the blade. The total pressure distributions in the wake region have been measured by means of a five-hole miniaturized pressure probe for the different flow conditions, allowing the evaluation of profile losses and of their dependence on the surface finish, as well as a direct comparison with the simulations. Results reported in the paper clearly highlight that only at the highest Reynolds number tested(Re=300000) surface roughness have some influence on the blade performance, both for steady and unsteady incoming flows. In this flow condition profile losses grow as the surface roughness increases, while no appreciable variations have been found at the lowest Reynolds number. The boundary layer evolution and the wake structure have shown that this trend is due to a thickening of the suction side boundary layer associated to an anticipation of transition process. On the other side, no effects have been observed on the pressure side boundary layer.

关键词： low-pressure turbine high-load profile roughness unsteady inflow CFD

The Riemann Problem for the dispersive Nonlinear Shallow Water Equations

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Communications in Computational Physics 2010年第1期7卷 64-102页

作者： Giovanna Grosso Matteo Antuono Eleuterio Toro diCAT University of GenovaVia Montallegro 1I-16145 GenovaItaly INSEAN(The Italian Ship Model Basin) Via di Vallerano 13900128RomaItaly Laboratory of Applied Mathematics University of TrentoVia Mesiano 77I-38100 TrentoItaly

The complete analytical solution of the Riemann problem for the homo-geneous dispersive Nonlinear Shallow Water Equations [Antuono, Liapidevskii andBrocchini, Stud. Appl. Math., 122 (2009), pp. 1-28] is presented, for both wet-bed anddry-bed conditions. Moreover, such a set of hyperbolic and dispersive depth-averagedequations shows an interesting resonance phenomenon in the wave pattern of the solu-tion and we define conditions for the occurrence of resonance and present an algorithmto capture it. As an indirect check on the analytical solution we have carried out a de-tailed comparison with the numerical solution of the government equations obtainedfrom a dissipative method that does not make explicit use of the solution of the localRiemann problem.

关键词： Riemann problem dispersive Nonlinear Shallow Water Equations compound waves resonance