Unsteady Flow Interaction Caused by Stator Secondary Vortices in a Turbine Rotor

1987 ◽  
Vol 109 (2) ◽  
pp. 251-256 ◽  
Author(s):  
A. Binder ◽  
W. Forster ◽  
K. Mach ◽  
H. Rogge
Keyword(s):  
Unsteady Flow ◽  
Turbulent Flow ◽  
Turbine Rotor ◽  
Turbulence Energy ◽  
Sudden Increase ◽  
Passage Vortex ◽  
Air Turbine ◽  
Time Distance ◽  
Turbulence Production ◽  
Secondary Vortices

Nonintrusive measurements near and within the rotor of a cold-air turbine showed a sudden increase of turbulence energy when the wake portion of the incoming fluid entered the rotor. It has been suggested that this was due to the cutting of the passage vortices and trailing-edge shed vortices which emerge from the stator row. Since these secondary vortices are located very close to the stator wakes, it was very difficult to distinguish between the effects of shed vortex and passage vortex cutting on turbulence intensification. In the present paper, a method is shown which, with the help of time–distance diagrams, made it possible to attribute the turbulence increase to the breakdown of the secondary vortices. Further, the time–distance diagrams made it possible to locate the origin of turbulence production and follow the spreading of the highly turbulent flow regions through the rotor channel.

scholarly journals Unsteady Flow Interaction Caused by Stator Secondary Vortices in a Turbine Rotor

1986 ◽  
Author(s):  
A. Binder ◽  
W. Förster ◽  
K. Mach ◽  
H. Rogge
Keyword(s):  
Unsteady Flow ◽  
Turbulent Flow ◽  
Turbine Rotor ◽  
Turbulence Energy ◽  
Sudden Increase ◽  
Passage Vortex ◽  
Air Turbine ◽  
Time Distance ◽  
Turbulence Production ◽  
Secondary Vortices

Nonintrusive measurements near and within the rotor of a cold-air turbine showed a sudden increase of turbulence energy when the wake portion of the incoming fluid entered the rotor. It has been suggested that this was due to the cutting of the passage vortices and trailing-edge shed vortices which emerge from the stator row. Since these secondary vortices are located very close to the stator wakes, it was very difficult to distinguish between the effects of shed vortex and passage vortex cutting on turbulence intensification. In the present paper, a method is shown which, with the help of time-distance diagrams, made it possible to attribute the turbulence increase to the breakdown of the secondary vortices. Further, the time-distance diagrams made it possible to locate the origin of the turbulence production and follow the spreading of the highly turbulent flow regions through the rotor channel.

Turbulence Production Due to Secondary Vortex Cutting in a Turbine Rotor

1985 ◽  
Vol 107 (4) ◽  
pp. 1039-1046 ◽  
Author(s):  
A. Binder
Keyword(s):  
Energy Production ◽  
Vortex Breakdown ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Turbulence Energy ◽  
Front Part ◽  
Flow Angle ◽  
Air Turbine ◽  
Turbulence Production ◽  
Secondary Vortices

Measurements of the unsteady flow field near and within a turbine rotor were made by means of a Laser-2-Focus velocimeter. The testing was performed in a single-stage cold-air turbine at part-load and near-design conditions. Random unsteadiness and flow angle results indicate that the secondary vortices of the stator break down after being cut and deformed by the rotor blades. A quantitative comparison shows that some of the energy contained in these secondary vortices is thereby converted into turbulence energy in the front part of the rotor. An attempt is made to explain this turbulence energy production as caused by the vortex breakdown.

Unsteady Flow Field of an Axial-Flow Turbine Rotor at a Low Reynolds Number

2006 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Unsteady Flow ◽  
Low Reynolds Number ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Frame Of Reference ◽  
Flow Angle ◽  
Low Reynolds ◽  
Secondary Vortices

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, and turbulence intensity, etc. were carried out at a very low Reynolds number condition, Reout = 3.5 × 104. The data obtained were analyzed from the viewpoints of both an absolute (stationary) frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage.

Unsteady Flow Field of an Axial-Flow Turbine Rotor at a Low Reynolds Number

2006 ◽  
Vol 129 (2) ◽  
pp. 360-371 ◽  
Author(s):  
Takayuki Matsunuma
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Unsteady Flow ◽  
Low Reynolds Number ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Frame Of Reference ◽  
Flow Angle ◽  
Low Reynolds ◽  
Secondary Vortices

The unsteady flow field of an annular turbine rotor was investigated experimentally using a laser Doppler velocimetry (LDV) system. Detailed measurements of the time-averaged and time-resolved distributions of the velocity, flow angle, turbulence intensity, etc., were carried out at a very low Reynolds number condition, Reout=3.5×104. The data obtained were analyzed from the viewpoints of both an absolute (stationary) frame of reference and a relative (rotating) frame of reference. The effect of the turbine nozzle wake and secondary vortices on the flow field inside the rotor passage was clearly captured. It was found that the nozzle wake and secondary vortices are suddenly distorted at the rotor inlet, because of the rotating potential field of the rotor. The nozzle flow (wake and passage vortices) and the rotor flow (boundary layer, wake, tip leakage vortex, and passage vortices) interact intensively inside the rotor passage.

Computational Predictions of Endwall Film Cooling for a Turbine Nozzle Vane With an Asymmetric Contoured Passage

2008 ◽  
Author(s):  
Yoji Okita ◽  
Chiyuki Nakamata
Keyword(s):  
Film Cooling ◽  
Computational Study ◽  
Suction Side ◽  
Geometrical Parameters ◽  
Passage Vortex ◽  
Rear Part ◽  
Cooling Hole ◽  
Secondary Vortices ◽  
Endwall Film Cooling ◽  
Film Cooling Holes

This paper presents results of a computational study for the endwall film cooling of an annular nozzle cascade employing a circumferentially asymmetric contoured passage. The investigated geometrical parameters and the flow conditions are set consistent with a generic modern HP-turbine nozzle. Rows of cylindrical film cooling holes on the contoured endwall are arranged with a design practice for the ordinary axisymmetric endwall. The solution domain, which includes the mainflow, cooling hole paths, and the coolant plenum, is discretized in the RANS equations with the realizable k-epsilon model. The calculated flow field shows that the pressure gradients across the passage between the pressure and the suction side are reduced with the asymmetric endwall, and consequently, the rolling up of the inlet boundary layer into the passage vortex is delayed and the separation line has moved further downstream. With the asymmetric endwall, because of the effective suppression of the secondary flow, more uniform film coverage is achieved especially in the rear part of the passage and the laterally averaged effectiveness is also significantly improved in this region. The closer inspection of the calculated thermal field reveals that, with the asymmetric passage, the coolant ejected from the holes are less deflected by the secondary vortices, and it attaches better to the endwall in this rear part.

Physical Interpretation of Flow and Heat Transfer in Preswirl Systems

2006 ◽  
Vol 129 (3) ◽  
pp. 769-777 ◽  
Author(s):  
Paul Lewis ◽  
Mike Wilson ◽  
Gary Lock ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Gas Turbines ◽  
Flow Parameter ◽  
Rotating Disk ◽  
Turbine Rotor ◽  
Scaled Model ◽  
Flow Rates

This paper compares heat transfer measurements from a preswirl rotor–stator experiment with three-dimensional (3D) steady-state results from a commercial computational fluid dynamics (CFD) code. The measured distribution of Nusselt number on the rotor surface was obtained from a scaled model of a gas turbine rotor–stator system, where the flow structure is representative of that found in an engine. Computations were carried out using a coupled multigrid Reynolds-averaged Navier-Stokes (RANS) solver with a high Reynolds number k-ε∕k-ω turbulence model. Previous work has identified three parameters governing heat transfer: rotational Reynolds number (Reϕ), preswirl ratio (βp), and the turbulent flow parameter (λT). For this study rotational Reynolds numbers are in the range 0.8×106<Reϕ<1.2×106. The turbulent flow parameter and preswirl ratios varied between 0.12<λT<0.38 and 0.5<βp<1.5, which are comparable to values that occur in industrial gas turbines. Two performance parameters have been calculated: the adiabatic effectiveness for the system, Θb,ad, and the discharge coefficient for the receiver holes, CD. The computations show that, although Θb,ad increases monotonically as βp increases, there is a critical value of βp at which CD is a maximum. At high coolant flow rates, computations have predicted peaks in heat transfer at the radius of the preswirl nozzles. These were discovered during earlier experiments and are associated with the impingement of the preswirl flow on the rotor disk. At lower flow rates, the heat transfer is controlled by boundary-layer effects. The Nusselt number on the rotating disk increases as either Reϕ or λT increases, and is axisymmetric except in the region of the receiver holes, where significant two-dimensional variations are observed. The computed velocity field is used to explain the heat transfer distributions observed in the experiments. The regions of peak heat transfer around the receiver holes are a consequence of the route taken by the flow. Two routes have been identified: “direct,” whereby flow forms a stream tube between the inlet and outlet; and “indirect,” whereby flow mixes with the rotating core of fluid.

scholarly journals Numerical investigation of unsteady flow past a circular cylinder using 2-D finite volume method

1970 ◽  
Vol 4 (1) ◽  
pp. 27-42 ◽  
Author(s):  
Md Mahbubar Rahman ◽  
Md. Mashud Karim ◽  
Md Abdul Alim
Keyword(s):  
Circular Cylinder ◽  
Unsteady Flow ◽  
Turbulent Flow ◽  
Finite Volume Method ◽  
Finite Volume ◽  
Turbulence Models ◽  
Drag Coefficients ◽  
Pressure Formulation ◽  
Lift And Drag ◽  
Volume Method

The dynamic characteristics of the pressure and velocity fields of unsteady incompressible laminar and turbulent wakes behind a circular cylinder are investigated numerically and analyzed physically. The governing equations, written in the velocity pressure formulation are solved using 2-D finite volume method. The initial mechanism for vortex shedding is demonstrated and unsteady body forces are evaluated. The turbulent flow for Re = 1000 & 3900 are simulated using k-? standard, k-? Realizable and k-? SST turbulence models. The capabilities of these turbulence models to compute lift and drag coefficients are also verified. The frequencies of the drag and lift oscillations obtained theoretically agree well with the experimental results. The pressure and drag coefficients for different Reynolds numbers were also computed and compared with experimental and other numerical results. Due to faster convergence, 2-D finite volume method is found very much prospective for turbulent flow as well as laminar flow.Keywords: Viscous unsteady flow, laminar & turbulent flow, finite volume method, circular cylinder.DOI: 10.3329/jname.v4i1.914Journal of Naval Architecture and Marine Engineering 4(2007) 27-42

Turbulent Flow Between Two Disks Contrarotating at Different Speeds

1996 ◽  
Vol 118 (2) ◽  
pp. 408-413 ◽  
Author(s):  
M. Kilic ◽  
X. Gan ◽  
J. M. Owen
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Unsteady Flow ◽  
Turbulent Flow ◽  
Boundary Layers ◽  
Axial Flow ◽  
Radial Component ◽  
Velocity Measurements ◽  
Type Flow ◽  
Radial Outflow

This paper describes a combined computational and experimental study of the turbulent flow between two contrarotating disks for −1 ≤ Γ ≤ 0 and Reφ ≈ 1.2 × 106, where Γ is the ratio of the speed of the slower disk to that of the faster one and Reφ is the rotational Reynolds number. The computations were conducted using an axisymmetric elliptic multigrid solver and a low-Reynolds-number k–ε turbulence model. Velocity measurements were made using LDA at nondimensional radius ratios of 0.6 ≤ x ≤ 0.85. For Γ = 0, the rotor–stator case, Batchelor-type flow occurs: There is radial outflow and inflow in boundary layers on the rotor and stator, respectively, between which is an inviscid rotating core of fluid where the radial component of velocity is zero and there is an axial flow from stator to rotor. For Γ = −1, antisymmetric contrarotating disks, Stewartson-type flow occurs with radial outflow in boundary layers on both disks and inflow in the viscid nonrotating core. At intermediate values of Γ, two cells separated by a streamline that stagnates on the slower disk are formed: Batchelor-type flow and Stewartson-type flow occur radially outward and inward, respectively, of the stagnation streamline. Agreement between the computed and measured velocities is mainly very good, and no evidence was found of nonaxisymmetric or unsteady flow.

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