scholarly journals Analysis of Secondary Flow Behavior in Low Solidity Cascade Diffuser of a Centrifugal Blower : 2nd Report, Effect of Blade Tip Groove near Leading Edge(Fluids Engineering)

2010 ◽  
Vol 76 (770) ◽  
pp. 1491-1498
Author(s):  
Tengen MURAKAMI ◽  
Masahiro ISHIDA ◽  
Daisaku SAKAGUCHI ◽  
Hironobu UEKI ◽  
Hiroshi HAYAMI
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Leading Edge ◽  
Centrifugal Blower ◽  
Blade Tip ◽  
Low Solidity Cascade Diffuser

Analysis of Secondary Flow Behavior in Low Solidity Cascade Diffuser of a Centrifugal Blower

2010 ◽  
Author(s):  
Masahiro Ishida ◽  
Tengen Murakami ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki ◽  
Hiroshi Hayami ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Vortex Formation ◽  
Leading Edge ◽  
Centrifugal Blower ◽  
Flow Rates ◽  
Noise Characteristics ◽  
Small Flow ◽  
Blade Tip ◽  
Low Solidity Cascade Diffuser

Aiming at reducing noise without deterioration of diffuser performance in a low solidity cascade diffuser (LSD) of a centrifugal blower, the authors have proposed to locate a shallow and short groove or a slot between the diffuser wall and the LSD blade tip limiting to near the blade leading edge. The effect of the LSD blade tip-groove on the blower characteristics and the noise characteristics were investigated experimentally as well as numerically. The mechanism being able to maintain the high LSD blade loading even at small flow rates was pursued in view points of the vortex formation and the induced secondary flow. In addition, the effect of the tip-groove length on the vortex formation in the shroud tip-groove and the secondary flow behavior in the LSD were analyzed numerically and an optimum tip-groove configuration was proposed. It is concluded that formations of the stable and intense vortex in the shroud tip-groove and the recirculating secondary flow along the shroud wall toward the impeller exit are the key factors for achieving a high LSD performance and reducing noise simultaneously at small flow rates.

Analysis of Noise Generated by Low Solidity Cascade Diffuser in a Centrifugal Blower

2008 ◽  
Author(s):  
Daisaku Sakaguchi ◽  
Masahiro Ishida ◽  
Hironobu Ueki ◽  
Hiroshi Hayami ◽  
Yasutoshi Senoo
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Centrifugal Blower ◽  
Discrete Frequency ◽  
Edge Location ◽  
Rotating Impeller ◽  
Low Solidity Cascade Diffuser ◽  
Blade Leading Edge

This paper deals with the effect of the blade leading edge location (RLSD) of a low solidity cascade diffuser (LSD) on noise and diffuser performance in a centrifugal blower. The noise of the LSD was measured and analyzed comparing with that of vaneless diffuser (VLD) in view points of overall noise, discrete frequency noise and broadband noise. The numerical flow analysis was conducted in the impeller and the diffuser by using a Navier-Stokes solver. The noise of the VLD varied little in a wide flow rate range, on the other hand, that of the LSD increased remarkably in the small flow rate by about 7 dB. The noise of the LSD did not increase near the design flow and was almost equal to that of the VLD. It was found that the increase in noise due to LSD is dependent mainly on the broadband noise between 600∼1000Hz, which was closely correlated to the lift force of the LSD blade. The two kinds of discrete frequency noise appeared due to an interaction between the rotating impeller and the LSD blade and another interaction between the rotating impeller blades and the reverse flow toward the impeller exit, but their influence on the overall noise were relatively small. By shifting the LSD blade leading edge location downstream from RLSD = 1.1 to 1.2, the noise was reduced by about 3 dB at the maximum without deterioration of the diffuser performance. The maximum lift coefficient of the LSD blade was achieved as high as 1.5 at the high attack angle of 17 degrees even in the case of RLSD = 1.2, resulting in improvement of the diffuser performance by about 40% and in reduction of the unstable flow range by about 11%.

B22 Noise Characteristics of Centrifugal Blower with Low Solidity Cascade Diffuser : Control of Secondary Flow by Local Tip-Groove

2009 ◽  
Vol 2009.62 (0) ◽  
pp. 55-56
Author(s):  
Yu KOBA ◽  
Keiichi NAGOSHI ◽  
Tengen MURAKAMI ◽  
Masahiro ISHIDA ◽  
Daisaku SAKAGUCHI ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Centrifugal Blower ◽  
Noise Characteristics ◽  
Low Solidity Cascade Diffuser

Impact of Secondary Flow on the Accuracy of Simplified Design Methods for Steam Turbine Stages

2012 ◽  
Author(s):  
Jan Schumann ◽  
Ulrich Harbecke ◽  
Daniel Sahnen ◽  
Thomas Polklas ◽  
Peter Jeschke ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Steam Turbine ◽  
Design Process ◽  
Design Method ◽  
Computing Time ◽  
Leading Edge ◽  
Design Methods ◽  
Preliminary Design ◽  
Line Design ◽  
Radial Equilibrium

The subject of the presented paper is the validation of a design method for HP and IP steam turbine stages. Common design processes have been operating with simplified design methods in order to quickly obtain feasible stage designs. Therefore, inaccuracies due to assumptions in the underlying methods have to be accepted. The focus of this work is to quantify the inaccuracy of a simplified design method compared to 3D Computational Fluid Dynamics (CFD) simulations. Short computing time is very convenient in preliminary design; therefore, common design methods work with a large degree of simplification. The origin of the presented analysis is a mean line design process, dealing with repeating stage conditions. Two features of the preliminary design are the stage efficiency, based on loss correlations, and the mechanical strength, obtained by using the beam theory. Due to these simplifications, only a few input parameters are necessary to define the primal stage geometry and hence, the optimal design can easily be found. In addition, by using an implemented law to take the radial equilibrium into account, the appropriate twist of the blading can be defined. However, in comparison to the real radial distribution of flow angles, this method implies inaccuracies, especially in regions of secondary flow. In these regions, twisted blades, developed by using the simplified radial equilibrium, will be exposed to a three-dimensional flow, which is not considered in the design process. The analyzed design cases show that discrepancies at the hub and shroud section do exist, but have minor effects. Even the shroud section, with its thinner leading-edge, is not vulnerable to these unanticipated flow angles.

scholarly journals Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

1999 ◽  
Author(s):  
Dieter E. Bohn ◽  
Karsten A. Kusterer
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Blade Surface ◽  
Cooling Fluid ◽  
Flow Phenomena ◽  
Vortex Systems

A leading edge cooling configuration is investigated numerically by application of a 3-D conjugate fluid flow and heat transfer solver, CHT-Flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multi-block technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row is on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45°. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical domain includes the internal cooling fluid supply, the radially inclined holes and the complete external flow field of the turbine vane in a high resolution grid. Periodic boundary conditions have been used in the radial direction. Thus, end wall effects have been excluded. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three dimensional and asymmetric jet flow field. Within a secondary flow analysis it can be shown that complex vortex systems are formed in the ejection holes and in the cooling fluid jets. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a good agreement concerning the vortex development. The phenomena on the suction side and the pressure side are principally the same. It can be found that the jets are barely touching the blade surface as the dominating vortex transports hot gas under the jets. Thus, the cooling efficiency is reduced.

scholarly journals Flow responses alteration by geometrical effects of tubercles on plates under the maximal angle of attack

2020 ◽  
pp. 095440622097543
Author(s):  
KS Mu ◽  
ABH Kueh ◽  
PN Shek ◽  
MR Mohd Haniffah ◽  
BC Tan
Keyword(s):  
Flow Direction ◽  
Flow Behavior ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Control Case ◽  
Reattachment Length ◽  
Flow Recirculation ◽  
Pressure Profiles ◽  
Maximal Angle ◽  
Geometrical Effects

Plates with leading-edge tubercles experience beneficially more gradual aerodynamics stalling when entering the post-stall regime. Little is known, however, about the corresponding aquatic flow responses when these tubercles-furnished plates are subjected to the maximal angle of attack, with the flow direction perpendicular to their planar area. Hence, this study presents numerically, by means of the flow behavior solver ANSYS, the flow responses alteration in terms of the geometrical effects of tubercles on plates through changes in amplitudes (5 mm, 10 mm, 15 mm) and wavelengths (50 mm, 100 mm, 150 mm) under the maximal angle of attack in comparison to a control case, i.e., without tubercles. Additional to the commonly examined flow velocity and pressure, characteristics such as wake (area, reattachment length, flow recirculation intensity) and newly defined downstream vortical parameters (area, perimeter, and Feret diameters) for the vortex region have been proposed and assessed. It is found that the drag increases with the tubercle wavelength but corresponds inversely with the tubercle amplitude. By correlating with the best beneficial velocity and pressure profiles, it has been characterized that the optimally performing plate is the one that generates the greatest flow recirculation intensity, wake area, and reattachment length, corresponding to the capability to produce also the highest vortical area, perimeter, and major Feret diameter. Compared to the control case, all plates with tubercles alter beneficially these flow behaviors. In conclusion, plates with tubercles contribute favorably to the flow behaviors under the maximal angle of attack compared to the control case while the newly proposed downstream parameters could serve capably as alternatives in corroborating the flow physics description in future studies.

scholarly journals Secondary Flow Control in Low Aspect Ratio Vanes Using Splitters

2016 ◽  
Author(s):  
Christopher Clark ◽  
Graham Pullan ◽  
Eric Curtis ◽  
Frederic Goenaga
Keyword(s):  
Kinetic Energy ◽  
Aspect Ratio ◽  
Secondary Flow ◽  
Current Practice ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Optimization Approach ◽  
Flow Strength ◽  
Low Aspect Ratio

Low aspect ratio vanes, often the result of overall engine architecture constraints, create strong secondary flows and high endwall loss. In this paper, a splitter concept is demonstrated that reduces secondary flow strength and improves stage performance. An analytic conceptual study, corroborated by inviscid computations, shows that the total secondary kinetic energy of the secondary flow vortices is reduced when the number of passages is increased and, for a given number of vanes, when the inlet endwall boundary layer is evenly distributed between the passages. Viscous computations show that, for this to be achieved in a splitter configuration, the pressure-side leg of the low aspect ratio vane horseshoe vortex, must enter the adjacent passage (and not “jump” in front of the splitter leading edge). For a target turbine application, four vane designs were produced using a multi-objective optimization approach. These designs represent: current practice for a low aspect ratio vane; a design exempt from thickness constraints; and two designs incorporating splitter vanes. Each geometry is tested experimentally, as a sector, within a low-speed turbine stage. The vane designs with splitters geometries were found to reduce the measured secondary kinetic energy, by up to 85%, to a value similar to the design exempt from thickness constraints. The resulting flowfield was also more uniform in both the circumferential and radial directions. One splitter design was selected for a full annulus test where a mixed-out loss reduction, compared to the current practice design, of 15.3% was measured and the stage efficiency increased by 0.88%.

A study of sound sources and unsteady surface pressure in an axial fan

2021 ◽  
pp. 2150267
Author(s):  
Bo Luo ◽  
Wuli Chu ◽  
Song Yan ◽  
Zhengjing Shen ◽  
Haoguang Zhang
Keyword(s):  
Leading Edge ◽  
Noise Spectrum ◽  
Industrial Applications ◽  
Acoustic Analogy ◽  
Dynamics Modeling ◽  
Axial Fan ◽  
Sound Sources ◽  
Recirculating Flow ◽  
Aerodynamic Interaction ◽  
Blade Tip

The noise emitted from an axial fan has become one of the primary concerns for many industrial applications. This paper presents the work to predict the noise generation and investigate sound sources in a low speed axial fan. Computational fluid dynamics modeling is conducted using Scale Adaptive Simulation for the unsteady flow field. The sound predictions by the acoustic analogy are in good agreement with the experimental data. The results from this study show that the aerodynamic interaction between the blades and outlet vanes has a major contribution to the radiated noise spectrum. Two types of sources of narrowband humps are identified in the axial fan. The first is found at the leading edge of the blade tip, which is related to the interaction of coherent flow structures in the blade tip region. The second is found in the vicinity of the blade hub, which can be attributed to the recirculating flow and hub vortex. The noise below the frequency of 1500 Hz is mainly due to the blade-outlet vane aerodynamic interaction, manifested as the tonal sound at BPF and its harmonics, whereas above 1500 Hz the broadband component of sound is mainly related to the turbulent boundary layers.

Numerical Investigation on a High Endwall Angle Turbine With Swept-Curved Vanes

2018 ◽  
Author(s):  
Fusheng Meng ◽  
Jie Gao ◽  
Weiliang Fu ◽  
Xuezheng Liu ◽  
Qun Zheng
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Heat Load ◽  
Leading Edge ◽  
Field Calculation ◽  
Prediction Ability ◽  
Expansion Turbine ◽  
Sst Turbulence Model ◽  
Flow Loss ◽  
Lp Turbine

In a high endwall angle turbine, large meridional expansion can cause the strong secondary flow at the endwall, which results in a larger endwall flow loss than the small meridional expansion turbine. The endwall heat transfer is strongly affected by secondary flow effect. In order to optimize the endwall flow to reduce the flow loss and optimize the distribution of heat load, the swept-curved method was used in this study. The swept-curved method was investigated on a transonic second stator (S2) with large meridional expansion in a Low-Pressure (LP) Turbine. Validation studies were performed to investigate the aerodynamic and the heat transfer prediction ability of shear stress transport (SST) turbulence model. The influence of different shapes of the stacking line, including forward-swept, backward-swept, positive-curved and negative-curved, were investigated through numerical simulation. The parameterized control of swept-curved height and angle were adopted to optimize the performance of the aerodynamic and heat transfer. 3D flow field calculation captured the relatively accurate flow structures in the parts of endwall and near endwall. Heat transfer behaviors were explored by means of isothermal wall temperature and Nusselt number (Nu) distribution. The results show that the maximal heat transfer coefficient at the leading edge, for the formation of horseshoe vortexes that cause the high velocity towards the endwall. The swept vane can improve the static pressure and heat load distribution at the endwall region, which decreases the area-averaged shroud heat flux by 2.6 percent and the loss coefficient 1.3 percent.

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