An Analytical Model for Boundary Layer Control Via Steady Blowing and Its Application to NACA-65-410 Cascade

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Mehmet N. Sarimurat ◽  
Thong Q. Dang
Keyword(s):  
Boundary Layer ◽  
Analytical Model ◽  
Integral Method ◽  
Velocity Ratio ◽  
Control Technique ◽  
Momentum Thickness ◽  
Compressor Cascade ◽  
Low Speed ◽  
Momentum Coefficient ◽  
Velocity Magnitude

In this paper, boundary-layer flow-control technique via steady blowing for low-speed compressor cascade applications is investigated using an analytical model based on the integral method and computational fluid dynamics (CFD). The integral method is developed and used to investigate the effect of the momentum, the velocity magnitude, and the angle of the blowing flow on the behavior of the boundary layer. It is found that the change in the boundary layer momentum thickness across the blowing location is a linear function of the blown-flow momentum coefficient and a decaying function of the blown-flow velocity ratio. For the case when the size of the blowing slot and the velocity magnitude of the blown-flow are kept constant and the blowing mass flow rate is increased by increasing the blowing angle, there is an “optimum” blowing angle that maximizes the benefit of the boundary layer blowing. This angle increases with increasing velocity ratio and reaches an asymptotic value of 45 deg. According to the model, the change in the momentum thickness across the blowing location is conveyed exponentially downstream; thus, a small change in the momentum thickness due to flow blowing can have significant effect downstream. The developed model is applied to the NACA-65-410 low speed cascade using CFD, and good agreement between theory and CFD is obtained.

An Analytical Model for Boundary Layer Control via Steady Blowing and its Application to NACA-65-410 Cascade

2013 ◽  
Author(s):  
Mehmet N. Sarimurat ◽  
Thong Q. Dang
Keyword(s):  
Boundary Layer ◽  
Analytical Model ◽  
Integral Method ◽  
Velocity Ratio ◽  
Control Technique ◽  
Momentum Thickness ◽  
Compressor Cascade ◽  
Low Speed ◽  
Momentum Coefficient ◽  
Velocity Magnitude

In this paper, boundary-layer flow-control technique via steady blowing for low-speed compressor cascade applications is investigated using an analytical model based on the integral method and Computational Fluid Dynamics (CFD). The integral method is developed and used to investigate the effect of the momentum, the velocity magnitude and the angle of the blowing flow on the behavior of the boundary layer. It is found that the change in the boundary layer momentum thickness across the blowing location is a linear function of the blown-flow momentum coefficient and a decaying function of the blown-flow velocity ratio. For the case when the size of the blowing slot and the velocity magnitude of the blown flow are kept constant, and the blowing mass flow rate is increased by increasing the blowing angle, there is an “optimum” blowing angle that maximizes the benefit of the boundary layer blowing. This angle increases with increasing velocity ratio and reaches an asymptotic value of 45°. According to the model, the change in the momentum thickness across the blowing location is conveyed exponentially downstream, thus a small change in the momentum thickness due to flow blowing can have significant effect downstream. The developed model is applied to the NACA-65-410 low speed cascade using CFD, and good agreement between theory and CFD is obtained.

Endwall Boundary Layer Control in Compressor Cascades

2004 ◽  
Author(s):  
Ralf Mu¨ller ◽  
Konrad Vogeler ◽  
Helmut Sauer ◽  
Martin Hoeger
Keyword(s):  
Boundary Layer ◽  
Leading Edge ◽  
Suction Side ◽  
Boundary Layer Control ◽  
Compressor Cascade ◽  
Low Speed ◽  
Passage Vortex ◽  
Additional Losses ◽  
Layer Control ◽  
Horse Shoe Vortex

Recent investigations have shown a reduction of secondary losses in compressor cascades using a bulb like modification of the profile at the endwall. This paper is focussed on experimental work in comparison of 5 different endwall modifications at a compressor cascade. The cascade is modified near the endwall with a bulb, a medium and a large fillet. The fillet configurations are modified by an axial blunt cut-off at the leading edge. The investigations have been carried out at a profile developed from a hub section of the Dresden Low Speed Research Compressor (LSRC) blade, a compressor profile with a nominal turning of 18 deg. A datum configuration and the 5 other configurations were tested at the Low Speed Cascade Windtunnel (LSCW). For the bulb configuration, an intensified horse shoe vortex was suspected and observed counterrotating to the passage vortex with an influence on its propagation. The interaction of the passage vortex and the suction side profile boundary layer is influenced. The superposition of both is minimized and the losses developing from this effect are significant lower. For the fillet and blunt-fillet configurations, a fillet vortex develops and was observed co-rotating to the passage vortex with an influence on the mentioned interaction as well. Blunt leading edges produce additional losses but the superposition of the growing vortices may reduce the overall losses. The cases show a reduction in losses of 1.9% for 3 deg incidence and a range of 1.2% rise to 1.9% reduction in dependence of the incidence. This equals a reduction of the isolated secondary losses up to 28% with respect to the reference profile. Detailed results of the experiments are presented for the reference and all modified cascades.

Blunt Trailing Edge Shear Wake Development With Turbulent In-Flow Boundary Layers

2005 ◽  
Author(s):  
Dhanalakshmi Challa ◽  
Joe Klewicki
Keyword(s):  
Boundary Layer ◽  
Shear Layer ◽  
Boundary Layers ◽  
High Speed ◽  
Velocity Ratio ◽  
Free Shear Layer ◽  
Low Speed ◽  
Axial Pressure Gradient ◽  
Layer Flow ◽  
Good Agreement

Experiments are conducted to explore the structural mechanisms involved in the post-separation evolution of a wall-bounded to a free-shear turbulent flow. At the upstream, both the boundary layers are turbulent. Experiments were conducted in a two-stream shear-layer tunnel, under a zero axial pressure gradient shear-wake configuration. A velocity ratio near 2 was explored. Profile data were collected with a single wire probe at various locations downstream of the blunt separation lip. With this set of measurements, mean profile, axial intensity and measures of profile evolution indicate that the predominant shift from turbulent boundary layer to free shear-layer like behavior occurs between the downstream locations x/θ = 13.7 & 27.4, where θ is the upstream momentum deficit thickness on the low-speed stream. The shear wake width is observed to be nominally constant with the downstream position. Axial velocity spectra show that the transition from boundary layer flow to shear flow occurs earlier in high-speed stream when compared to low speed stream. Strouhal number, Sto, of initial vortex rollup based on initial momentum thickness was found to be 0.034, which is in very good agreement with the existing literature. Other measures are in good agreement with linear stability considerations found in the literature.

Numerical Investigation of the Solidity Effect on Linear Compressor Cascades

2014 ◽  
Author(s):  
J. Sans ◽  
M. Resmini ◽  
J.-F. Brouckaert ◽  
S. Hiernaux
Keyword(s):  
Numerical Investigation ◽  
State Of The Art ◽  
Leading Edge ◽  
Operating Conditions ◽  
Compressor Cascade ◽  
Minimum Loss ◽  
Low Speed ◽  
High Mach ◽  
The Stability ◽  
The Impact

Solidity in compressors is defined as the ratio of the aerodynamic chord over the peripheral distance between two adjacent blades, the pitch. This parameter is simply the inverse of the pitch-to-chord ratio generally used in turbines. Solidity must be selected at the earliest design phase, i.e. at the level of the meridional design and represents a crucial step in the whole design process. Most of the existing studies on this topic rely on low-speed compressor cascade correlations from Carter or Lieblein. The aim of this work is to update those correlations for state-of-the-art controlled diffusion blades, and extend their application to high Mach number flow regimes more typical of modern compressors. Another objective is also to improve the physical understanding of the solidity effect on compressor performance and stability. A numerical investigation has been performed using the commercial software FINE/Turbo. Two different blade profiles were selected and investigated in the compressible flow regime as an extension to the low-speed data on which the correlations are based. The first cascade uses a standard double circular arc profile, extensively referenced in the literature, while the second configuration uses a state-of-the-art CDB, representative of low pressure compressor stator mid-span profile. Both profiles have been designed with the same inlet and outlet metal angles and the same maximum thickness but the camber and thickness distributions, the stagger angle and the leading edge geometry of the CDB have been optimized. The determination of minimum loss, optimum incidence and deviation is addressed and compared with existing correlations for both configurations and various Mach numbers that have been selected in order to match typical booster stall and choke operating conditions. The emphasis is set on the minimum loss performance at mid-span. The impact of the solidity on the operating range and the stability of the cascade are also studied.

Performance and Boundary Layer Development of a High Turning Compressor Cascade at Sub- and Supercritical Flow Conditions

2012 ◽  
Author(s):  
Christoph Bode ◽  
Dragan Kožulović ◽  
Udo Stark ◽  
Heinz Hoheisel
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Density Ratio ◽  
Boundary Layer Separation ◽  
Experimental Results ◽  
Numerical Code ◽  
Compressor Cascade ◽  
Boundary Layer Development ◽  
Boundary Layer Interaction ◽  
Inlet Angle

Based on current numerical investigations, the present paper reports on new Q2D midspan-calculations and results for the well known high turning (Δβ = 50°) supercritical (Ma1 = 0.85) compressor cascade V2. A Q2D treatment of the problem was chosen in order to avoid the difficult modelling of the porous endwalls in a corresponding 3D approach. All simulations were done with the RANS solver TRACE of the DLR Cologne in combination with modified versions of the Wilcox turbulence model and Langtry/Menter transition model. Existing experimental Q2D midspan-results for the V2 compressor cascade were used to demonstrate the improved ability of the numerical code to determine performance characteristics, blade pressure and Mach number distributions as well as boundary layer parameter and velocity distributions. The loss characteristics show minimum loss regions when plotted against inlet angle or axial velocity density ratio. Within these regions, increasing with decreasing Mach number, the experimental results were adequately predicted. Outside these regions it turned out difficult to reproduce the experimental results due to increasing boundary layer separation. Furthermore, the prediction quality was very good for subsonic conditions (Ma1 = 0.60) and still reasonable for supercritical conditions (Ma1 = 0.85), where shock/boundary layer interaction made the prediction more difficult.

Effect of Boundary Layer Suction on Aerodynamic Performance of High-Turning Compressor Cascade

2013 ◽  
Author(s):  
Longxin Zhang ◽  
Shaowen Chen ◽  
Hao Xu ◽  
Jun Ding ◽  
Songtao Wang
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Studies ◽  
Aerodynamic Performance ◽  
Parameter Distribution ◽  
Compressor Cascade ◽  
Boundary Layer Suction ◽  
End Wall ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

Compared with suction slots, suction holes are (1) flexible in distribution; (2) alterable in size; (3) easy to fabricate and (4) high in strength. In this paper, the numerical and experimental studies for a high turning compressor cascade with suction air removed by using suction holes in the end-wall at a low Mach numbers are carried out. The main objective of the investigation is to study the influence of different suction distributions on the aerodynamic performance of the compressor cascade and to find a better compound suction scheme. A numerical model was first made and validated by comparing with the experimental results. The computed flow visualization and exit parameter distribution showed a good agreement with experimental data. Second, the model was then used to simulate the influence of different suction distributions on the aerodynamic performance of the compressor cascade. A better compound suction scheme was obtained by summarizing numerical results and tested in a low speed wind tunnel. As a result, the compound suction scheme can be used to significantly improve the performance of the compressor cascade because the corner separation gets further suppressed.

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