A Database of Optimal Airfoils for Axial Compressor Throughflow Design

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Markus Schnoes ◽  
Eberhard Nicke
Keyword(s):  
Numerical Optimization ◽  
Axial Compressor ◽  
Large Set ◽  
Performance Potential ◽  
Flow Solver ◽  
Five Dimensions ◽  
Aerodynamic Loading ◽  
Significant Performance ◽  
Stagger Angle ◽  
Inflow Conditions

Airfoil shapes tailored to specific inflow conditions and loading requirements can offer a significant performance potential over classic airfoil shapes. However, their optimal operating range has to be matched thoroughly to the overall compressor layout. This paper describes methods to organize a large set of optimized airfoils in a database and its application in the throughflow design. Optimized airfoils are structured in five dimensions: inlet Mach number, blade stagger angle, pitch–chord ratio, maximum thickness–chord ratio, and a parameter for aerodynamic loading. In this space, a high number of airfoil geometries are generated by means of numerical optimization. During the optimization of each airfoil, the performance at design and off-design conditions is evaluated with the blade-to-blade flow solver MISES. Together with the airfoil geometry, the database stores automatically calibrated correlations which describe the cascade performance in throughflow calculation. Based on these methods, two subsonic stages of a 4.5-stage transonic research compressor are redesigned. Performance of the baseline and updated geometry is evaluated with 3D CFD. The overall approach offers accurate throughflow design incorporating optimized airfoil shapes and a fast transition from throughflow to 3D CFD design.

A Database of Optimal Airfoils for Axial Compressor Throughflow Design

2016 ◽  
Author(s):  
Markus Schnoes ◽  
Eberhard Nicke
Keyword(s):  
Mach Number ◽  
Relational Database ◽  
Numerical Optimization ◽  
Axial Compressor ◽  
Large Set ◽  
Flow Solver ◽  
Five Dimensions ◽  
Maximum Thickness ◽  
Aerodynamic Loading ◽  
Stagger Angle

This text describes methods to organize a large set of optimized airfoils in a relational database and its application in throughflow design. Optimized airfoils are structured in five dimensions: inlet Mach number, blade stagger angle, pitch-chord ratio, maximum thickness-chord ratio and a parameter for aerodynamic loading. In this space, a high number of airfoil geometries is generated by means of numerical optimization. Each airfoil geometry is tailored to its specific requirements and optimized for a wide working range as well as low losses. During the optimization of each airfoil, performance in design and off-design conditions is evaluated with the blade-to-blade flow solver MISES. Together with airfoil geometry, the database stores automatically calibrated correlations which describe cascade performance in throughflow calculation. Based on these methods, two subsonic stages of a 4.5-stage transonic research compressor are redesigned. Performance of baseline and updated geometries is evaluated with 3D CFD. The overall approach offers accurate throughflow design incorporating optimized airfoil shapes and a fast transition from throughflow to 3D CFD design.

Numerical Investigation of a Highly Loaded Axial Compressor Stage With Inlet Distortions

2011 ◽  
Author(s):  
Andreas Lesser ◽  
Jens Iseler ◽  
Reinhard Niehuis
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Flow Simulation ◽  
Numerical Calculations ◽  
Angle Distribution ◽  
Compressor Stage ◽  
Flow Solver ◽  
Transonic Compressor ◽  
Numerical Flow Simulation ◽  
Inflow Conditions

This paper deals with the numerical flow-simulation of a transonic compressor stage, which has been investigated for baseline as well as distorted inflow conditions at the Institute of Propulsion Technology of the DLR in Cologne (Dunker [1] and Lecht [2]). The inlet distortions are generated in the experiment upstream of the compressor stage by non-rotating steel bars, while in the numerical calculations the total pressure and inflow angle distribution measured downstream of the bars are taken as inflow boundary conditions. The circumferential extent of the generated total pressure and inflow angle distortion is 120 degrees. Numerical simulations were performed for uniform inflow conditions at 85% and 100% rotational speed. For disturbed inflow conditions, a full-annulus calculation has been carried out for an operational point at peak efficiency. The object of the investigations is to validate the flow solver for compressor flow with distorted inflow. The results from time-averaged numerical and experimental data are compared extensively. The experimental trends are qualitativly and in the most part also quantitativly well reproduced in the numerical calculations.

Studies on Downstream Stator With Rotor Re-Staggering and Forward Sweeping in a Subsonic Axial Compressor Stage

2011 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Flow Field ◽  
Computational Model ◽  
Flow Rate ◽  
Total Pressure ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Axial Distance ◽  
Compressor Stage ◽  
Numerical Work ◽  
Stagger Angle

The present numerical work studies the flow field in subsonic axial compressor stator passages for: (a) preceding rotor sweep (b) preceding rotor re-staggering (three stagger angle changes: 0°, +3° and +5°); and (c) stator sweeping (two 20° forward sweep schemes). The following are the motives for the study: at the off-design conditions, compressor rotors are re-staggered to alleviate the stage mismatching by adjusting the rows to the operating flow incidence. Fundamental to this is the understanding of the effects of rotor re-staggering on the downstream component. Secondly, sweeping the rotor stages alters the axial distance between the successive rotor-stator stages and necessitates that the stator vanes must also be swept. To the best of the author’s knowledge, stator sweeping to suit such scenarios has not been reported. The computational model for the study utilizes well resolved hexahedral grids. A commercial CFD package ANSYS® CFX 11.0 was used with standard k-ω turbulence model for the simulations. CFD results were well validated with experiments. The following observations were made: (1) When the rotor passage is closed by re-staggering, with the same mass flow rate and the same stator passage area, stators were subjected to negative incidences. (2) Effect of stator sweeping on the upstream rotor flow field is insignificant. Comparison of total pressure rise carried by the downstream stators suggests that an appropriate redesign of stator is essential to match with the swept rotors. (3) While sweeping the stator is not recommended, axial sweeping is preferable over true sweeping when it is necessary.

Experimental Investigation of Numerically Optimized Wavy Microchannels Created Through Additive Manufacturing

2017 ◽  
Author(s):  
Kathryn L. Kirsch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Pressure Drop ◽  
Numerical Optimization ◽  
High Surface ◽  
Direct Metal Laser Sintering ◽  
Flow Solver ◽  
Skin Cooling ◽  
End Use ◽  
Optimization Schemes

The increased design space offered by additive manufacturing can inspire unique ideas and different modeling approaches. One tool for generating complex yet effective designs is found in numerical optimization schemes, but until relatively recently, the capability to physically produce such a design had been limited by manufacturing constraints. In this study, a commercial adjoint optimization solver was used in conjunction with a conventional flow solver to optimize the design of wavy microchannels, the end use of which can be found in gas turbine airfoil skin cooling schemes. Three objective functions were chosen for two baseline wavy channel designs: minimize the pressure drop between channel inlet and outlet, maximize the heat transfer on the channel walls and maximize the ratio between heat transfer and pressure drop. The optimizer was successful in achieving each objective and generated significant geometric variations from the baseline study. The optimized channels were additively manufactured using Direct Metal Laser Sintering and printed reasonably true to the design intent. Experimental results showed that the high surface roughness in the channels prevented the objective to minimize pressure loss from being fulfilled. However, where heat transfer was to be maximized, the optimized channels showed a corresponding increase in Nusselt number.

On the Recessed Blade Tip With and Without a Porous Material in an Axial Compressor

2014 ◽  
Author(s):  
Young-Jin Jung ◽  
Tae-Gon Kim ◽  
Minsuk Choi
Keyword(s):  
Porous Material ◽  
Axial Compressor ◽  
Internal Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Flow Solver ◽  
Stall Margin ◽  
Tip Leakage ◽  
Blade Tip ◽  
Strong Vortex

This paper addresses the effect of the recessed blade tip with and without a porous material on the performance of a transonic axial compressor. A commercial flow solver was employed to analyze the performance and the internal flow of the axial compressor with three different tip configurations: reference tip, recessed tip and recessed tip filled with a porous material. It was confirmed that the recessed blade tip is an effective method to increase the stall margin in an axial compressor. It was also found in the present study that the strong vortex formed in the recess cavity on the tip pushed the tip leakage flow backward and weakened the tip leakage flow itself, consequently increasing the stall margin without any penalty of the efficiency in comparison to the reference tip. The recessed blade tip filled with a porous material was suggested with hope to obtain the larger stall margin and the higher efficiency. However, it was found that a porous material in the recess cavity is unfavorable to the performance in both the stall margin and the efficiency. An attempt has been made to explain the effect of the recess cavity with and without a porous material on the flow in an axial compressor.

Desensitization of Axial Compressor Performance and Stability to Tip Clearance Size

2015 ◽  
Author(s):  
Engin Erler ◽  
Huu Duc Vo ◽  
Hong Yu
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Aerodynamic Stability ◽  
Tip Leakage ◽  
Compressor Rotor ◽  
Flow Features ◽  
Parametric Studies ◽  
Compressor Performance ◽  
Flow Effects ◽  
Stagger Angle

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design change on a baseline double circular arc axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely full forward chordwise sweep and partially low stagger angle, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower performance and aerodynamic stability sensitivity to tip clearance.

Effect of Tip Clearance on the Performance of Forward Swept Subsonic Axial Compressor Rotors at High Stagger Angles

2011 ◽  
Author(s):  
P. V. Ramakrishna ◽  
M. Govardhan
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Geometric Flow ◽  
Suction Surface ◽  
Local Flow ◽  
Vena Contracta ◽  
Flow Acceleration ◽  
Pressure Surface ◽  
Stagger Angle

Tip leakage phenomenon in axial compressors is sensitive to the flow incidence, flow coefficient, tip gap height and the pressure gradients. All these geometric/flow features are considerably altered by blade stagger angle. Literature on the stagger angle effects in compressors is scarce; and indeed, such studies for various tip gap heights have not been reported yet. The present paper reports the effect of rotor stagger angle on the performance of subsonic axial compressor rotor with different forward sweep configurations and for various rotor tip clearances. The computational model for the study utilizes finest hexahedral grids. A commercial CFD package ANSYS® CFX 11.0 was used with standard k-ω turbulence model for the simulations. CFD results were well validated with experiments. The following observations were made: At higher stagger angles, flow separates from upstream suction surface locations. Little tip clearance had a positive effect for certain stagger angle increments owing to beneficial interaction of leakage flows with the local flow field. However, severe performance loss was observed at higher stagger settings with large clearances. As the stagger angle was increased, vena contracta effect was highly reduced. At high stagger angles, the flow was observed to leak in a more “axially-reversed” fashion through the tip gap. The deep lowest pressure zones near the pressure surface of the tip are due to the effect of ‘vena contracta.’ Such zones near the suction surface edge of the tip are due to flow acceleration. This particular feature is directly correlated with the tip aerofoil loading and thickness-to-tip gap ratio.

Desensitization of Axial Compressor Performance and Stability to Tip Clearance Size

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Engin Erler ◽  
Huu Duc Vo ◽  
Hong Yu
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Lower Sensitivity ◽  
Aerodynamic Stability ◽  
Compressor Rotor ◽  
Design Changes ◽  
Flow Features ◽  
Parametric Studies ◽  
Flow Effects ◽  
Stagger Angle

This paper presents a computational and analytical study to identify and elucidate fundamental flow features associated with the desensitization of performance and aerodynamic stability of an axial compressor rotor to tip clearance change. Parametric studies of various design changes to a baseline double circular arc airfoil axial rotor led to the identification of two flow features associated with reducing sensitivity to tip clearance, namely, high incoming meridional momentum in the tip region and reduction/elimination of double tip leakage. Numerical experiments were subsequently performed on the baseline rotor geometry to validate these two flow features and explain the associated flow physics by variations in incoming meridional momentum and pitch size. Finally, two designs were proposed, namely, a full forward chordwise sweep (FFCS) rotor and a rotor with gradual stagger angle reduction in the outer span, to exploit these flow features. The results indicated that both designs produce the intended flow effects and exhibit lower sensitivity of performance and aerodynamic stability to tip clearance.

Computation of Three-Dimensional Flow Fields Through Rotating Blade Rows and Comparison With Experiment

1982 ◽  
Vol 104 (2) ◽  
pp. 394-400 ◽  
Author(s):  
K. P. Sarathy
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Peak Efficiency ◽  
Three Dimensional Flow ◽  
Flow Solver ◽  
Rotating Blade ◽  
Blade Row ◽  
Time Marching ◽  
Design Speed

A three-dimensional inviscid time-marching calculation solving the unsteady Euler equations in a coordinate system rotating with the blade row has been developed, based on the Denton flow solver. This calculation was used to compute the flow field through the rotor of a transonic axial compressor and compared to measurements made with an advanced laser velocimeter at DFVLR. The comparison is made at design speed at pressure ratio corresponding to peak efficiency. Comparisons of the calculated and experimentally determined Mach number contours indicate excellent agreement in the entrance region where the viscous blockage effects are small. The methodology of the analysis is also described in this paper.

Influence of Stagger Angle Variation on Aerodynamic Damping and Frequency Shifts

2007 ◽  
Author(s):  
I. Sladojevic´ ◽  
A. I. Sayma ◽  
M. Imregun
Keyword(s):  
Structural Properties ◽  
Natural Frequencies ◽  
Rotor Blades ◽  
Angle Variation ◽  
Frequency Shifts ◽  
Aerodynamic Damping ◽  
Aerodynamic Loading ◽  
Aeroelastic Model ◽  
Aero Engine ◽  
Stagger Angle

The paper presents the results of a study focusing on aerodynamic non-uniformities and their effect on frequency and damping variations. Small tolerances of stagger angle or camber can affect the aerodynamic loading of rotor blades, without significantly altering the structural properties. This investigation looks into the degree of change of natural frequencies and damping of the aeroelastic model caused by blade stagger angle variations. The model used in the study is a simplified aero-engine fan model. The investigation involved three different patterns at two operating speeds. The results suggest that damping in a mis-staggered structure is more prone to variation than frequencies.

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