Effect of Stagger Angle on the Three-Dimensional Separation Around a NACA65 Blade in a Decelerating Flow

2021 ◽  
Vol 14 (1) ◽  
pp. 34-41
Author(s):  
Yoichi Kinoue ◽  
Yuya Matsumoto ◽  
Masaki Sakaguchi ◽  
Norimasa Shiomi
Keyword(s):  
Three Dimensional ◽  
Stagger Angle

Mechanism and Flow Control on the Mismatching of Impeller and Vaned Diffuser Caused by Inlet Prewhirl for Centrifugal Compressors

2016 ◽  
Author(s):  
Qiangqiang Huang ◽  
Xinqian Zheng ◽  
Aolin Wang
Keyword(s):  
Flow Control ◽  
Control Method ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Vaned Diffuser ◽  
Inlet Distortion ◽  
Computational Fluid Dynamics Cfd ◽  
Stagger Angle ◽  
Good Agreement ◽  
Matching Relation

Air often flows into compressors with inlet prewhirl, because it will obtain a circumferential component of velocity via inlet distortion or swirl generators such as inlet guide vanes. A lot of research has shown that inlet prewhirl does influence the characteristics of components, but the change of the matching relation between the components caused by inlet prewhirl is still unclear. This paper investigates the influence of inlet prewhirl on the matching of the impeller and the diffuser and proposes a flow control method to cure mismatching. The approach combines steady three-dimensional Reynolds-averaged Navier-Stokes (RANS) simulations with theoretical analysis and modeling. The result shows that a compressor whose impeller and diffuser match well at zero prewhirl will go to mismatching at non-zero prewhirl. The diffuser throat gets too large to match the impeller at positive prewhirl and gets too small for matching at negative prewhirl. The choking mass flow of the impeller is more sensitive to inlet prewhirl than that of the diffuser, which is the main reason for the mismatching. To cure the mismatching via adjusting the diffuser vanes stagger angle, a one-dimensional method based on incidence matching has been proposed to yield a control schedule for adjusting the diffuser. The optimal stagger angle predicted by analytical method has good agreement with that predicted by computational fluid dynamics (CFD). The compressor is able to operate efficiently in a much broader flow range with the control schedule. The flow range, where the efficiency is above 80%, of the datum compressor and the compressor only employing inlet prewhirl and no control are just 25.3% and 31.8%, respectively. For the compressor following the control schedule, the flow range is improved up to 46.5%. This paper also provides the perspective of components matching to think about inlet distortion.

scholarly journals Implementation of a Compressor Face Boundary Condition Based on Small Disturbances

2000 ◽  
Vol 123 (2) ◽  
pp. 386-391 ◽  
Author(s):  
John W. Slater ◽  
Gerald C. Paynter
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Acoustic Response ◽  
Acoustic Disturbance ◽  
Disturbance Model ◽  
Stagger Angle ◽  
Large Improvement ◽  
Small Disturbances

A compressor-face boundary condition that models the unsteady interactions of acoustic and convective velocity disturbances with a compressor has been implemented into a three-dimensional computational fluid dynamics code. Locally one-dimensional characteristics along with a small-disturbance model are used to compute the acoustic response as a function of the local stagger angle and the strength and direction of the disturbance. Simulations of the inviscid flow in a straight duct, a duct coupled to a compressor, and a supersonic inlet demonstrate the behavior of the boundary condition in relation to existing boundary conditions. Comparisons with experimental data show a large improvement in accuracy over existing boundary conditions in the ability to predict the reflected disturbance from the interaction of an acoustic disturbance with a compressor.

Assessment of Three-Dimensional Inviscid Effects in Turbomachinery Using Simple Models

1976 ◽  
Vol 98 (2) ◽  
pp. 163-172 ◽  
Author(s):  
A. Tamura ◽  
B. Lakshminarayana
Keyword(s):  
Radial Direction ◽  
Three Dimensional ◽  
Axial Flow ◽  
Velocity Fields ◽  
Dimensional Effects ◽  
Vortex Lines ◽  
Source Line ◽  
Constant Strength ◽  
Stagger Angle ◽  
Modified Theory

The general objective of the investigation reported in this paper is to obtain a reliable understanding of the three-dimensional inviscid effects in axial flow turbomachinery. The calculation is based on the method of distributed singularities. The baldes are represented by a series of line vortices and line sources which have their axes along the radial direction and are arranged along the blade mean camber surface. The basic perturbed velocity fields due to radial vortex lines of constant strength and radial source lines of variable strength are computed from a modified theory based on Tyson’s and Rossow’s formulation. Examples illustrating the three-dimensional effects due to hub/tip ratio, stagger angle, and number of blades are carried out. The effects of the radial variation of the strength of the radial source line are examined. The three-dimensional effects are found to be appreciable for a low hub/tip configuration with small number of blades.

Transonic shear flow in a three-dimensional channel

1982 ◽  
Vol 123 ◽  
pp. 443-457
Author(s):  
T. C. Adamson ◽  
M. Sichel
Keyword(s):  
Shock Wave ◽  
Shear Flow ◽  
Relative Velocity ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Axial Flow ◽  
Region Of Interest ◽  
Problem Formulation ◽  
Flow Area ◽  
Stagger Angle

Inviscid transonic shear flow in a rectangular channel is considered; opposite walls are parallel except in the region of interest, where one pair of opposing walls form a nozzle-like constriction. The flow exhibits the essential features found in an axial-flow rotor of zero stagger angle, where the relative velocity is transonic, the constricted passage being similar to the channel formed between two adjacent blades. Analytical solutions, valid to second order, are presented for the case where the ratio of the order of the change in velocity caused by the variation in flow area to the order of the change in velocity across the channel due to the shear is unity. The case where this ratio is small compared with one is discussed, as is the problem formulation for a flow with a shock wave in the passage

Rotating Stall Inception From Spike and Rotating Instability in a Variable-Pitch Axial-Flow Fan

2008 ◽  
Author(s):  
Takahiro Nishioka ◽  
Toshio Kanno ◽  
Hiroshi Hayami
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Rotating Stall ◽  
Tip Leakage Flow ◽  
Axial Flow Fan ◽  
Trailing Edge ◽  
Stall Inception ◽  
Tip Leakage ◽  
Rotating Instability ◽  
Stagger Angle

End wall flow fields at the two stagger-angle settings for the rotor blades in the low-speed axial-flow fan are experimentally and numerically investigated to elucidate the mechanism of stall inception. Rotating instability is confirmed near the maximum pressure-rise point at both design and large stagger-angle settings. This instability is induced by the interaction between the incoming flow, tip leakage flow, and backflow from the trailing edge. The stall-inception pattern, however, differs at the two stagger-angle settings. The stall inception from a spike is observed at the design stagger-angle setting, and the stall inception without the spike and modal disturbance is observed at the large stagger-angle setting. The rotating instability seems to influence the formation of stall cell at the large stagger-angle setting. Tip-leakage vortex breakdown occurs at both design and large stagger angle settings. This breakdown induces the three-dimensional separation on the suction surface of the rotor blade at the tip. Three-dimensional separation at the design stagger-angle setting is stronger than that at the large stagger-angle setting. The strong separation grows into a three-dimensional separation vortex, which crosses the blade passage near the trailing edge. This separation vortex seems to be one of the conditions for spike initiation.

A Study on Stirring Characteristics in a Microchannel With Various Arrangement of Blocks

2003 ◽  
Author(s):  
Hyeung Seok Heo ◽  
Yong Kweon Suh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Commercial Code ◽  
Block Height ◽  
Stirring Effect ◽  
Particles Trajectories ◽  
Stagger Angle ◽  
Block Arrangement

In this study a newly designed microchannel is proposed. This design comprises periodically arranged simple blocks. In this configuration, the stirring is greatly enhanced at a certain parameter set. To characterize the flow field and the stirring effect both the numerical and experimental methods were employed. To obtain the velocity field, three-dimensional numerical computation to the Navier Stokes equations are performed by using a commercial code, FLUENT 6.0. The fluid-flow solutions are then cast into studying the characteristics of stirring with the aid of Lyapunov exponent. In this study the Lyapunov exponents are computed manually because the commercial code does not provide the corresponding option. In the experiment, flow visualization for the stirring effect is performed by using pure glycerin in one tank and glycerin mixed with a fluorescent dye in the other. The numerical results show that the particles’ trajectories in the microchannel heavily depend on the block arrangement. It was shown that the stirring is significantly enhanced at larger block-height and it reaches maximum when the height is 0.8 times the channel width. We also studied the effect of the block stagger angle, and it turns out that the stirring performance is the best at the block angle 45°.

scholarly journals Implementation of a Compressor Face Boundary Condition Based on Small Disturbances

2000 ◽  
Author(s):  
John W. Slater ◽  
Gerald C. Paynter
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Acoustic Response ◽  
Acoustic Disturbance ◽  
Disturbance Model ◽  
Stagger Angle ◽  
Large Improvement ◽  
Small Disturbances

A compressor-face boundary condition that models the unsteady interactions of acoustic and convective velocity disturbances with a compressor has been implemented into a three-dimensional computational fluid dynamics code. Locally one-dimensional characteristics along with a small-disturbance model are used to compute the acoustic response as a function of the local stagger angle and the strength and direction of the disturbance. Simulations of the inviscid flow in a straight duct, a duct coupled to a compressor, and a supersonic inlet demonstrate the behavior of the boundary condition in relation to existing boundary conditions. Comparisons with experimental data show a large improvement in accuracy over existing boundary conditions in the ability to predict the reflected disturbance from the interaction of an acoustic disturbance with a compressor.

The orbit of Pluto over a long interval of time

1966 ◽  
Vol 25 ◽  
pp. 227-229 ◽  
Author(s):  
D. Brouwer
Keyword(s):  
Periodic Orbit ◽  
Numerical Integration ◽  
Restricted Problem ◽  
Three Dimensional ◽  
The Third ◽  
Circular Restricted Problem ◽  
Resonance Relation

The paper presents a summary of the results obtained by C. J. Cohen and E. C. Hubbard, who established by numerical integration that a resonance relation exists between the orbits of Neptune and Pluto. The problem may be explored further by approximating the motion of Pluto by that of a particle with negligible mass in the three-dimensional (circular) restricted problem. The mass of Pluto and the eccentricity of Neptune's orbit are ignored in this approximation. Significant features of the problem appear to be the presence of two critical arguments and the possibility that the orbit may be related to a periodic orbit of the third kind.

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