Comparison of Sweep and Dihedral Effects on Compressor Cascade Performance

1998 ◽  
Vol 120 (3) ◽  
pp. 454-463 ◽  
Author(s):  
T. Sasaki ◽  
F. Breugelmans
Keyword(s):  
Secondary Flow ◽  
Parametric Study ◽  
Three Dimensional ◽  
High Energy ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Upstream Direction ◽  
Dimensional Measurements ◽  
Linear Compressor Cascade

The influence of two stacking lines, namely sweep and dihedral, has been investigated in a linear compressor cascade. Both types of blade considered are symmetric about midspan and consist of a straight central section with either swept or dihedral sections toward the endwalls. Two types of experiment have been carried out. First, a parametric study was performed by changing both the magnitude and the extent of the sweep or dihedral. In the case of swept blades, those with forward sweep (SWF), for which the stacking line is swept in the upstream direction toward the endwall, were found to have better performance than backward-swept blades. Subsequently, four sets of SWFs were compared. In the case of dihedral blades, it is well known that the dihedral is advantageous when the angle between the suction surface and the endwall is obtuse, i.e., positive dihedral. Thus, four sets of positive dihedral blades (DHP) were compared. In both SWF and DHP blades, those configurations that have better efficiency than straight blades were determined. Second, detailed three-dimensional measurements inside the blade passage were performed in the cases that showed the best performance in the parametric study. Both SWF and DHP showed significant effects on the flowfield. In the SWF case, a vortex, which has the opposite sense to the passage vortex, was observed in the forward portion inside the blade passage. This vortex supplies high-energy fluid to the endwall region and reduces the corner stall. The secondary flow is greatly reduced. In the DHP, the blade loading was reduced at the endwall and increased at the midspan. Reduction of the corner stall and the secondary flow was also observed.

scholarly journals Comparison of Sweep and Dihedral Effects on Compressor Cascade Performance

1997 ◽  
Author(s):  
T. Sasaki ◽  
F. Breugelmans
Keyword(s):  
Secondary Flow ◽  
Parametric Study ◽  
Three Dimensional ◽  
High Energy ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Upstream Direction ◽  
Dimensional Measurements ◽  
Linear Compressor Cascade

The influence of two stacking lines, namely sweep and dihedral, has been investigated in a linear compressor cascade. Both types of blades considered are symmetrical about midspan and consist of a straight central section with either swept or dihedral sections towards the endwalls. Two types of experiments have been carried out. Firstly, a parametric study was performed by changing both the magnitude and the extent of the sweep or dihedral. In the case of swept blades, those with forward sweep (SWF), for which the stacking line is swept in the upstream direction towards the endwall, were found to have better performance than backward swept blades. Subsequently, four sets of SWFs were compared. In the case of dihedral blades, it is well-known that the dihedral is advantageous when the angle between the suction surface and the endwall is obtuse, i.e. positive dihedral. Thus, four sets of positive dihedral blades (DHP) were compared. In both SWF and DHP blades, those configurations which have better efficiency than straight blades were determined. Secondly, detailed three-dimensional measurements inside the blade passage were performed in the cases which showed the best performance in the parametric study. Both SWF and DHP showed significant effects on the flowfield. In the SWF case, a vortex, which has the opposite sense to the passage vortex, was observed in the forward portion inside the blade passage. This vortex supplies high-energy fluid to the endwall region and reduces the corner stall. The secondary flow is greatly reduced. In the DHP, the blade loading was reduced at the endwall and increased at the midspan. Also reduction of the corner stall and the secondary flow was observed.

Vortex Structures for Highly-Loaded Subsonic Compressor Cascades With Slot Injection

2017 ◽  
Author(s):  
Huanlong Chen ◽  
Huaping Liu ◽  
Dongfei Zhang ◽  
Linxi Li
Keyword(s):  
Suction Side ◽  
Compressor Blade ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Vortex Control ◽  
Analysis Theory ◽  
Numerical Simulation Methods ◽  
Linear Compressor Cascade ◽  
Highly Loaded

A promising flow analytical way to offset the respective shortcomings for the experimental measure and numerical simulation methods is presented. First, general topological rules which are applicable to the skin-friction vector lines on the passage surface, to the flow patterns in the cross-section of the cascade as well as on the blade-to-blade surface were deduced for the turbomachinery cascades with/without suction/blowing slots in this paper. Second, the qualitative analysis theory of the differential equation was used to investigate the distribution feature of the flow singular points for the limiting streamlines equation. The topological structure of the flow pattern on the cascade passage surfaces was discussed in detail. Third, the experiment and numerical simulations results for a linear compressor cascade passage with highly-loaded compound-lean slotted blade, which were combined to topologically examine the flow structure with penetrating slot injections through the blade pressure side and suction side. The results showed that the general topological rules are applicable and effective for flow diagnosis in highly-loaded compressor blade passage with slots. Finally, an integrated vortex control model, in which the blade compound-lean effect and the injection flow through the slots were coupled, was presented. The model shows that reasonable slot injection configurations can effectively control the concentrated shedding vortices from the suction surface of a highly-loaded compressor cascades passage, thereby the aerodynamic performance for the blade passage is remarkably improved. The present work provides a novel theoretical analysis method and insights of the flow for the turbine blade passage with cooling structures, aspirated compressor blade passage and other applications with new flow control configurations in turbomachinery field.

Investigations of Three-Dimensional Flow Field Development in an Axial Compressor Cascade

2019 ◽  
Author(s):  
Saeed A. El-Shahat ◽  
Hesham M. El-Batsh ◽  
Ali M. A. Attia ◽  
Guojun Li ◽  
Lei Fu
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Computational Results ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Blade Passage ◽  
Field Development ◽  
Hole Pressure ◽  
Sensor Module ◽  
Linear Compressor Cascade

Abstract This paper presents a complete study about three-dimensional (3-D) flow field development in a linear compressor cascade where flow field in the blade passage has been studied experimentally as well as numerically. In the experimental work, a linear compressor cascade test section was installed in an open loop wind tunnel. The experimental data was acquired for a Reynolds number of 2.98 × 105 based on the blade chord and the inlet flow conditions. The flow field characteristics in blade passage including 3-D flow velocity and velocity magnitude have been measured by using calibrated five and seven-hole pressure probes connected to ATX sensor module data acquisition system (DAQ). To investigate flow development in the blade passage, velocity coefficient through streamwise planes has been calculated from the measured data. The computational fluid dynamics (CFD) study of the flow field was performed to gain a better understanding of the flow features. Present computational study was first validated with previous experimental and numerical work to check mesh accuracy and give confidence for computational results. Then, two turbulence models, Spalart-Allmaras (S-A) and shear stress transport SST (k-ω) were used for the present work. From both parts of study, the flow field development through the cascade have been investigated and compared. Moreover, the received data demonstrated a good agreement between the experimental and computational results. The predicted flow streamlines by numerical calculations showed regions characterized by flow separation and recirculation zones such as corner separation that could be used to enhance the understanding of the loss mechanism in compressor cascades. All measurements taken by the two probes, 5 and 7-hole pressure probes, have been analyzed and compared. The 5-hole pressure probe measurements have showed more agreements with computational results than 7-hole probe. Furthermore S-A turbulence model calculations showed more consistencies with experimental results than SST (k-ω) model.

Three Dimensional Flow in a Linear Compressor Cascade at Design Conditions

1991 ◽  
Author(s):  
Shun Kang ◽  
Ch. Hirsch
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Leading Edge ◽  
Vortex Sheet ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Three Dimensional Flow ◽  
Linear Compressor ◽  
Dimensional Flow ◽  
Linear Compressor Cascade

Experimental data measured upstream, inside and downstream of a large scale linear compressor cascade with NACA 65-1810 blade profile are presented. The flow is surveyed at 15 traverse planes with 14 (in half span) × 24 (in pitch) points inside a passage, and 14 × 33 points downstream exit plane. The measurements are obtained with a small size five hole probe, and wall static pressure taps. It is observed that the three dimensional flow inside and behind the cascade is characterized, not only by the conventional aspects, such as leading edge horseshoe vortices, passage vortices, trailing edge vortex sheet and corner vortices, but also by two spiral node points, formed from the three dimensional separation lines, on suction surface, and the resulting concentrated vortices.

Control of Three-Dimensional Separations in Axial Compressors by Tailored Boundary Layer Suction

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
Semiu A. Gbadebo ◽  
Nicholas A. Cumpsty ◽  
Tom P. Hynes
Keyword(s):  
Boundary Layer ◽  
Static Pressure ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Surface Flow ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Blade Passage ◽  
Boundary Layer Suction ◽  
End Wall

One of the important ways of improving turbomachinery compressor performance is to control three-dimensional (3D) separations, which form over the suction surface and end wall corner of the blade passage. Based on the insights gained into the formation of these separations, this paper illustrates how an appropriately applied boundary layer suction of up to 0.7% of inlet mass flow can control and eliminate typical compressor stator hub corner 3D separation over a range of operating incidence. The paper describes, using computational fluid dynamics, the application of suction on the blade suction surface and end wall boundary layers and exemplifies the influence of end wall dividing streamline in initiating 3D separation in the blade passage. The removal of the separated region from the blade suction surface is confirmed by an experimental investigation in a compressor cascade involving surface flow visualization, surface static pressure, and exit loss measurements. The ensuing passage flow field is characterized by increased blade loading (static pressure difference between pressure and suction surface), enhanced average static pressure rise, significant loss removal, and a uniform exit flow. This result also enables the contribution of the 3D separation to the overall loss and passage blockage to be assessed.

An experience-independent inverse design optimization method of compressor cascade airfoil

2019 ◽  
Vol 233 (4) ◽  
pp. 431-442 ◽  
Author(s):  
Yujie Zhu ◽  
Yaping Ju ◽  
Chuhua Zhang
Keyword(s):  
Design Optimization ◽  
Design Method ◽  
Three Dimensional ◽  
Optimal Solution ◽  
Leading Edge ◽  
Optimization Method ◽  
Inverse Design ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Inverse Design Method

Most of the inverse design methods of turbomachinery experience the shortcoming where the target aerodynamic parameters need to be manually specified depending on the designers’ experience and insight, making the design result aleatory and even deviated from the real optimal solution. To tackle this problem, an experience-independent inverse design optimization method is proposed and applied to the redesign of a compressor cascade airfoil in this study. The experience-independent inverse design optimization method can automatically obtain the target pressure distribution along the cascade airfoil through the genetic algorithm, rather than through the manual specification approach. The shape of cascade airfoil is then solved by the adjoint method. The effectiveness of the experience-independent inverse design optimization method is demonstrated by two inverse design cases of the compressor cascade airfoil, i.e. the inverse design of only the suction surface and the inverse design of both the suction and pressure surfaces. The results show that the proposed inverse design method is capable of significantly improving the aerodynamic performance of the compressor cascade. At the examined flow condition, a thin airfoil profile is beneficial to flow accelerations near the leading edge and flow separation avoidance near the trailing edge. The proposed inverse design method is quite generic and can be extended to the three-dimensional inverse design of advanced compressor blades.

Unsteady Pressure Investigations of Corner Separated Flow in a Linear Compressor Cascade

2015 ◽  
Author(s):  
Gherardo Zambonini ◽  
Xavier Ottavy
Keyword(s):  
Transfer Functions ◽  
Leading Edge ◽  
Positive Pressure ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Linear Compressor ◽  
Corner Separation ◽  
Unsteady Pressure ◽  
Linear Compressor Cascade ◽  
End Wall

The aim of this work is to present detailed unsteady pressure measurements of three-dimensional flow field in a NACA 65 linear compressor cascade. Chord-based Reynolds number of 382000 and incidence angle of 4 degrees were chosen as target configuration of the rig, which clearly presents the corner separation phenomenon at the juncture of the blade suction side and the end-wall. Concerning the experiments, a characterization of the mean and fluctuating component of wall static pressure on the surface of a specially developed blade is achieved at first. This fluctuating component is investigated utilizing nineteen high sensitivity condenser microphones plugged into blade cavities which have been carefully calibrated. Transfer functions obtained by calibration are exploited to reconstruct the time-dependent pressure signal and finally statistics, conditional ensemble averages, coherence and spectra analyses of fluctuations are presented in order to investigate the unsteady characteristics of the corner separation. High values of root mean square are individuated near the leading edge and in the separation region on the suction surface of the blade. Skewness and kurtosis show an intermittent behavior of the separation onset, which moves upstream and downstream on the suction surface. This intermittency of the separation line is probably linked with the existence of a bimodal behavior of the size of the corner separation. The analyses of coherence and conditional ensemble average between the signals at the leading edge and at the onset of the separation suggest a critical influence of angle and velocity of the incoming end-wall boundary layer on the positive pressure signatures of the shear layer, which characterize the inception of the separation.

Location Effect of Boundary Layer Suction on Compressor Hub-Corner Separation

2014 ◽  
Author(s):  
Ping-Ping Chen ◽  
Wei-Yang Qiao ◽  
Karsten Liesner ◽  
Robert Meyer
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Three Dimensional ◽  
Base Flow ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Corner Separation ◽  
Boundary Layer Suction

The large secondary flow area in the compressor hub-corner region usually leads to three-dimensional separation in the passage with large amounts of total pressure loss. In this paper numerical simulations of a linear high-speed compressor cascade, consisting of five NACA 65-K48 stator profiles, were performed to analyze the flow mechanism of hub-corner separation for the base flow. Experimental validation is used to verify the numerical results. Active control of the hub-corner separation was investigated by using boundary layer suction. The influence of the selected locations of the endwall suction slot was investigated in an effort to quantify the gains of the compressor cascade performance. The results show that the optimal chordwise location should contain the development section of the three-dimensional corner separation downstream of the 3D corner separation onset. The best pitchwise location should be close enough to the vanes’ suction surface. Therefore the optimal endwall suction location is the MTE slot, the one from 50% to 75% chord at the hub, close to the blade suction surface. By use of the MTE slot with 1% suction flow ratio, the total-pressure loss is substantially decreased by about 15.2% in the CFD calculations and 9.7% in the measurement at the design operating condition.

Aerodynamic Aspects of Endwall Film-Cooling

1996 ◽  
Author(s):  
S. Friedrichs ◽  
H. P. Hodson ◽  
W. N. Dawes
Keyword(s):  
Secondary Flow ◽  
Film Cooling ◽  
Large Scale ◽  
Static Pressure ◽  
Three Dimensional ◽  
Surface Flow ◽  
Flow Visualisation ◽  
Film Cooling Effectiveness ◽  
Blade Passage ◽  
Endwall Film Cooling

This paper describes an investigation of the aerodynamic aspects of endwall film-cooling, in which the flow field downstream of a large-scale low-speed linear turbine cascade has been measured. The integrated losses and locations of secondary flow features with and without end wait film-cooling have been determined for variations of both the coolant supply pressure and injection location. Together with previous measurements of adiabatic film-cooling effectiveness and surface-flow visualisation, these results reveal the nature of the interactions between the ejected coolant and the flow in the blade passage. Measured hole massflows and a constant static pressure mixing analysis, together with the measured losses, allow the decomposition of the losses into three distinct entropy generation mechanisms: loss generation within the hole, loss generation due to the mixing of the coolant with the mainstream, and change in secondary loss generation in the blade passage. Results show that the loss generation within the coolant holes is substantial and that ejection into regions of low static pressure increases the loss per unit coolant massflow. Ejection upstream of the three-dimensional separation lines on the endwall changes secondary flow and reduces its associated losses. The results show that it is necessary to take the three-dimensional nature of the endwall flow into account in the design of endwall film-cooling configurations.

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