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.

scholarly journals Steady flow separation patterns in a 45 degree junction

2000 ◽  
Vol 411 ◽  
pp. 1-38 ◽  
Author(s):  
C. ROSS ETHIER ◽  
SUJATA PRAKASH ◽  
DAVID A. STEINMAN ◽  
RICHARD L. LEASK ◽  
GREGORY G. COUCH ◽  
...  
Keyword(s):  
Flow Separation ◽  
Stokes Equations ◽  
Bypass Graft ◽  
Three Dimensional ◽  
Symmetry Plane ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Measured Velocity ◽  
Curved Tube

Numerical and experimental techniques were used to study the physics of flow separation for steady internal flow in a 45° junction geometry, such as that observed between two pipes or between the downstream end of a bypass graft and an artery. The three-dimensional Navier–Stokes equations were solved using a validated finite element code, and complementary experiments were performed using the photochromic dye tracer technique. Inlet Reynolds numbers in the range 250 to 1650 were considered. An adaptive mesh refinement approach was adopted to ensure grid-independent solutions. Good agreement was observed between the numerical results and the experimentally measured velocity fields; however, the wall shear stress agreement was less satisfactory. Just distal to the ‘toe’ of the junction, axial flow separation was observed for all Reynolds numbers greater than 250. Further downstream (approximately 1.3 diameters from the toe), the axial flow again separated for Re [ges ] 450. The location and structure of axial flow separation in this geometry is controlled by secondary flows, which at sufficiently high Re create free stagnation points on the model symmetry plane. In fact, separation in this flow is best explained by a secondary flow boundary layer collision model, analogous to that proposed for flow in the entry region of a curved tube. Novel features of this flow include axial flow separation at modest Re (as compared to flow in a curved tube, where separation occurs only at much higher Re), and the existence and interaction of two distinct three-dimensional separation zones.

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