Discussion: “Secondary Flow Effects in a Bounded Rectangular Jet” (Foss, J. F., and Jones, J. B., 1968, ASME J. Basic Eng., 90, pp. 241–248)

1968 ◽  
Vol 90 (4) ◽  
pp. 632-632
Author(s):  
Pasquale M. Sforza
Keyword(s):  
Secondary Flow ◽  
Rectangular Jet ◽  
Flow Effects

Secondary Flow Effects in a Bounded Rectangular Jet

1968 ◽  
Vol 90 (2) ◽  
pp. 241-248 ◽  
Author(s):  
J. F. Foss ◽  
J. B. Jones
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Flow Structure ◽  
Flow Model ◽  
Three Dimensional ◽  
Dimensional Effects ◽  
Rectangular Jet ◽  
Secondary Flow Structure ◽  
Flow Effects

The isotach pattern in a bounded jet with an aspect ratio of 6 suggests the presence of a secondary flow structure. A physical flow model is presented, and further measurements substantiate the model and support the conclusion that three-dimensional effects are highly significant in bounded jets of modest aspect ratio, even in the mid plane between the bounding walls.

End-Wall Film Cooling Through Fan-Shaped Holes With Different Area Ratios

2006 ◽  
Vol 129 (2) ◽  
pp. 212-220 ◽  
Author(s):  
Giovanna Barigozzi ◽  
Giuseppe Franchini ◽  
Antonio Perdichizzi
Keyword(s):  
Secondary Flow ◽  
Mass Flow ◽  
Film Cooling ◽  
Three Dimensional ◽  
Wide Band ◽  
Lateral Spreading ◽  
Area Ratio ◽  
Adiabatic Effectiveness ◽  
Flow Effects ◽  
End Wall

The present paper reports on the aerothermal performance of a nozzle vane cascade, with film-cooled end walls. The coolant is injected through four rows of cylindrical holes with conical expanded exits. Two end-wall geometries with different area ratios have been compared. Tests have been carried out at low speed (M=0.2), with coolant to mainstream mass flow ratio varied in the range 0.5–2.5%. Secondary flow assessment has been performed through three-dimensional (3D) aerodynamic measurements, by means of a miniaturized five-hole probe. Adiabatic effectiveness distributions have been determined by using the wide-band thermochromic liquid crystals technique. For both configurations and for all the blowing conditions, the coolant share among the four rows has been determined. The aerothermal performances of the cooled vane have been analyzed on the basis of secondary flow effects and laterally averaged effectiveness distributions; this analysis was carried out for different coolant mass flow ratios. It was found that the smaller area ratio provides better results in terms of 3D losses and secondary flow effects; the reason is that the higher momentum of the coolant flow is going to better reduce the secondary flow development. The increase of the fan-shaped hole area ratio gives rise to a better coolant lateral spreading, but appreciable improvements of the adiabatic effectiveness were detected only in some regions and for large injection rates.

Reduction of Secondary Flow Effects in a Linear Cascade by Use of an Air Suction From the Endwall

1996 ◽  
Author(s):  
K. Funazaki ◽  
T. Endo ◽  
T. Tanuma
Keyword(s):  
Secondary Flow ◽  
Flow Rate ◽  
Pressure Measurement ◽  
Gas Turbines ◽  
Stagnation Pressure ◽  
Working Fluid ◽  
Steam Turbines ◽  
Linear Cascade ◽  
Oil Flow ◽  
Flow Effects

The objective of this study is to reduce secondary flow effects in a linear cascade by sucking the working fluid from the endwall. It is widely known that the secondary flow developed in a cascade has a significant impact on the cascade loss or blade erosion in steam turbines. Therefore, a number of studies have been made on the physics of the secondary flow and several devices to control the secondary flow, such as a fence, have been examined. In this study, considering the application to nozzles in gas turbines or steam turbines, the air suction approach is investigated for reducing the secondary flow effects. A suction slit is provided on the lower endwall of the cascade and a flow rate of the sucked air is controlled by adjusting the exit pressure of the slit. The effects of the suction upon the flow nearby the endwall and the secondary flow are observed through several flow visualizing techniques, for example an oil flow method or a tuft method. Furthermore, velocity and stagnation pressure measurement are conducted by a five-hole pressure tube. This clearly demonstrates the vorticity and loss profiles downstream of the cascade with and without the endwall suction.

A Geometry Generation Framework for Contoured Endwalls

2019 ◽  
Author(s):  
L. E. Wood ◽  
R. R. Jones ◽  
O. J. Pountney ◽  
J. A. Scobie ◽  
D. A. S. Rees ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Three Dimensional ◽  
Aerodynamic Loss ◽  
Construction Methods ◽  
Novel Approach ◽  
Wide Range ◽  
Blade Row ◽  
Flow Features ◽  
Flow Effects ◽  
Geometric Variation

Abstract The mainstream, or primary, flow in a gas turbine annulus is characteristically two-dimensional over the mid-span region of the blading, where the radial flow is almost negligible. Contrastingly, the flow in the endwall and tip regions of the blading is highly three-dimensional, characterised by boundary layer effects, secondary flow features and interaction with cooling flows. Engine designers employ geometric contouring of the endwall region in order to reduce secondary flow effects and subsequently minimise their contribution to aerodynamic loss. Such is the geometric variation of vane and blade profiles — which has become a proprietary art form — the specification of an effective endwall geometry is equally unique to each blade-row. Endwall design methods, which are often directly coupled to aerodynamic optimisers, are widely developed to assist with the generation of contoured surfaces. Most of these construction methods are limited to the blade-row under investigation, while few demonstrate the controllability required to offer a universal platform for endwall design. This paper presents a Geometry Generation Framework (GGF) for the generation of contoured endwalls. The framework employs an adaptable meshing strategy, capable of being applied to any vane or blade, and a versatile function-based approach to defining the endwall shape. The flexibility of this novel approach is demonstrated by recreating a selection of endwalls from the literature, which were selected for their wide-range of contouring approaches.

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