scholarly journals Analysis of Secondary Flow Behavior in Low Solidity Cascade Diffuser of a Centrifugal Blower : 1st Report, Effect of Radial Location of Blade Leading Edge(Fluids Engineering)

2010 ◽  
Vol 76 (768) ◽  
pp. 1169-1175
Author(s):  
Daisaku SAKAGUCHI ◽  
Masahiro ISHIDA ◽  
Tengen MURAKAMI ◽  
Hironobu UEKI ◽  
Hiroshi HAYAMI
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Leading Edge ◽  
Centrifugal Blower ◽  
Radial Location ◽  
Low Solidity Cascade Diffuser ◽  
Blade Leading Edge

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

Effects of endwall profiling near the blade leading edge on the sealing effectiveness of turbine rim seal

2019 ◽  
Vol 233 (7) ◽  
pp. 821-833
Author(s):  
Cheng Shuxian ◽  
Li Zhigang ◽  
Li Jun
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Pressure Fluctuation ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Numerical Comparison ◽  
Local Pressure ◽  
Flow Loss ◽  
Circumferential Pressure ◽  
Blade Leading Edge

Endwall profiling designed to reduce secondary flow loss may change the local pressure distribution which has an impact on the sealing effectiveness of a rim seal. This paper presents a numerical comparison of the sealing effectiveness of the rim seal and the aerodynamic performance of the blade with five different endwall profiling near the blade leading edge. Three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations coupled with a fully developed shear stress transport (SST) turbulent model are utilized to investigate the sealing effectiveness and the flow characteristics of turbine rim seal. The numerical method for the pressure field and sealing performance of turbine rim seal is validated on the basis of published experimental data. The total-to-static efficiency of the blade and the minimum sealing rates of the rim seal with five endwall profiling near blade leading edge are compared. The baseline, convex and concave cases are selected to investigate the transient variation of the sealing effectiveness and the flow field in the disc cavity. In comparison with baseline case, the convex endwall makes the high pressure area move forward, increases the mainstream circumferential pressure fluctuation, and reduces the sealing effectiveness. The concave endwall reduces the local pressure and the mainstream circumferential pressure fluctuation, and increases the sealing effectiveness. However, the concave endwall profiling enhances the vortex in the blade passage and increases the secondary flow loss. The flow field near the rim seal with different endwall profiling is illustrated and analyzed.

Overall Effectiveness for a Film Cooled Turbine Blade Leading Edge With Varying Hole Pitch

2010 ◽  
Author(s):  
Thomas E. Dyson ◽  
Dave G. Bogard ◽  
Justin D. Piggush ◽  
Atul Kohli
Keyword(s):  
Turbine Blade ◽  
Hot Spots ◽  
Leading Edge ◽  
Stagnation Line ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Overall Effectiveness ◽  
Blade Leading Edge

Overall effectiveness, φ, for a simulated turbine blade leading edge was experimentally measured using a model constructed with a relatively high conductivity material selected so that the Biot number of the model matched engine conditions. The model incorporated three rows of cylindrical holes with the center row positioned on the stagnation line. Internally the model used an impingement cooling configuration. Overall effectiveness was measured for pitch variation from 7.6d to 9.6d for blowing ratios ranging from 0.5 to 3.0, and angle of attack from −7.7° to +7.7°. Performance was evaluated for operation with a constant overall mass flow rate of coolant. Consequently when increasing the pitch, the blowing ratio was increased proportionally. The increased blowing ratio resulted in increased impingement cooling internally and increased convective cooling through the holes. The increased internal and convective cooling compensated, to a degree, for the decreased coolant coverage with increased pitch. Performance was evaluated in terms of laterally averaged φ, but also in terms of the minimum φ. The minimum φ evaluation revealed localized hot spots which are arguably more critical to turbine blade durability than the laterally averaged results. For small increases in pitch there was negligible decrease in performance.

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.

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