Unsteady Aerodynamical Blade Row Interaction in a New Multistage Research Turbine: Part 2 — Numerical Investigation

2001 ◽  
Author(s):  
Wolfgang Höhn ◽  
Ralf Gombert ◽  
Astrid Kraus
Keyword(s):  
Boundary Layer ◽  
Grid Method ◽  
Low Pressure ◽  
Equation Model ◽  
Navier Stokes ◽  
Viscous Boundary Layer ◽  
Low Pressure Turbine ◽  
Blade Row ◽  
Multistage Turbine ◽  
Blade Row Interaction

This paper is the second part of a two part paper, which describes in part one the experimental setup and results of a new multistage turbine. Part two presents results of unsteady viscous flow calculations based on cold flow experiments of that three stage low pressure turbine. The present paper emphasizes the investigation of stator-stator interaction of a low pressure turbine section of a commercial jet engine. Different positions for the second and third stator are studied numerically and experimentally with respect to the blade row interaction, unsteady blade loading and unsteady boundary layer effects. A time accurate Reynolds averaged Navier-Stokes solver is applied for the computations. Turbulence is modeled using the Spalart-Allmaras one equation model turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed by a four stage Runge-Kutta scheme, which is accelerated by a two grid method in the viscous boundary layer around the blades and alternatively by a dual time stepping method. At the inlet and outlet reflecting or non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness. In particular, the flow field with respect to time averaged and unsteady quantities such as surface pressure, vorticity, unsteady velocity field and skin friction are compared with the experiments conducted in the cold air flow test rig.

Numerical and Experimental Investigation of Unsteady Flow Interaction in a Low-Pressure Multistage Turbine

2000 ◽  
Vol 122 (4) ◽  
pp. 628-633 ◽  
Author(s):  
Wolfgang Ho¨hn ◽  
Klaus Heinig
Keyword(s):  
Unsteady Flow ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Grid Method ◽  
Low Pressure ◽  
Navier Stokes ◽  
Viscous Boundary Layer ◽  
Low Pressure Turbine ◽  
Flow Interaction ◽  
Multistage Turbine

This paper presents results of unsteady viscous flow calculations and corresponding cold flow experiments of a three-stage low-pressure turbine. The investigation emphasizes the study of unsteady flow interaction. A time-accurate Reynolds-averaged Navier–Stokes solver is applied for the computations. Turbulence is modeled using the Spalart–Allmaras one-equation turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed with a four-stage Runge–Kutta scheme, which is accelerated by a two-grid method in the viscous boundary layer around the blades. At the inlet and outlet, nonreflecting boundary conditions are used. The quasi-three-dimensional calculations are conducted on a stream surface around midspan, allowing a varying stream tube thickness. In order to study the unsteady flow interaction, a three-stage low-pressure turbine rig of a modern commercial jet engine is built up. In addition to the design point, the Reynolds number, the wheel speed, and the pressure ratio are also varied in the tests. The numerical method is able to capture important unsteady effects found in the experiments, i.e., unsteady transition as well as the blade row interaction. In particular, the flow field with respect to time-averaged and unsteady quantities such as surface pressure, entropy, and skin friction is compared with the experiments conducted in the cold air flow test rig. [S0889-504X(00)02004-3]

Numerical and experimental investigation of unsteady flow interaction in a low-pressure multistage turbine

2003 ◽  
Vol 217 (2) ◽  
pp. 211-217 ◽  
Author(s):  
W Höhn
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Grid Method ◽  
Low Pressure ◽  
Navier Stokes ◽  
Viscous Boundary Layer ◽  
Low Pressure Turbine ◽  
Flow Interaction ◽  
Multistage Turbine ◽  
Viscous Boundary

The paper presents results of unsteady viscous flow calculations and corresponding cold flow experiments on a three-stage low-pressure turbine. The investigation emphasizes the study of unsteady flow interaction. A time-accurate, Reynolds-averaged Navier-Stokes solver is applied for the computations. Turbulence is modelled using the Spalart-Allmaras one-equation turbulence model. The influence of modern transition models on the unsteady flow predictions is investigated. Integration of the governing equations in time is performed with a four-stage Runge-Kutta scheme, which is accelerated by a two-grid method in the viscous boundary layer around the blades. At the inlet and outlet, non-reflecting boundary conditions are used. The quasi-three-dimensional calculations are conducted on a stream surface around mid-span, allowing a varying stream tube thickness. A three-stage, low-pressure turbine rig of a modern commercial jet engine is used for a study of the unsteady flow interaction. The numerical method is able to capture important unsteady effects found in the experiments, i.e. unsteady transition as well as the bladerow interaction. In particular, the flowfield with respect to time-averaged and unsteady quantities such as surface pressure, vorticity and turbulence intensity is compared with the experiments conducted in the cold airflow test rig.

Numerical and Experimental Investigation of Unsteady Flow Interaction in a Low Pressure Multistage Turbine

2000 ◽  
Author(s):  
Wolfgang Höhn ◽  
Klaus Heinig
Keyword(s):  
Unsteady Flow ◽  
Pressure Ratio ◽  
Grid Method ◽  
Low Pressure ◽  
Navier Stokes ◽  
Viscous Boundary Layer ◽  
Low Pressure Turbine ◽  
Flow Interaction ◽  
Multistage Turbine ◽  
Viscous Boundary

The paper presents results of unsteady viscous flow calculations and corresponding cold flow experiments of a three stage low pressure turbine. The investigation emphasize the study of unsteady flow interaction. A time accurate Reynolds averaged Navier-Stokes solver is applied for the computations. Turbulence is modeled using the Spalart-Allmaras one equation turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed with a four stage Runge-Kutta scheme, which is accelerated by a two grid method in the viscous boundary layer around the blades. At the inlet and outlet non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness. In order to study the unsteady flow interaction a three stage low pressure turbine rig of a modern commercial jet engine is built up. Besides the design point, the Reynolds number, the wheel speed and the pressure ratio are varied in the tests. The numerical method is able to capture important unsteady effects found in the experiments, i.e. unsteady transition as well as the blade row interaction. In particular, the flow field with respect to time averaged and unsteady quantities such as surface pressure, entropy and skin friction is compared with the experiments conducted in the cold air flow test rig.

The Unsteady Development of a Turbulent Wake Through a Downstream Low-Pressure Turbine Blade Passage

2005 ◽  
Vol 127 (2) ◽  
pp. 388-394 ◽  
Author(s):  
R. D. Stieger ◽  
H. P. Hodson
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Production Mechanism ◽  
Blade Passage ◽  
Low Pressure Turbine ◽  
Blade Row ◽  
Turbulence Production

This paper presents two-dimensional LDA measurements of the convection of a wake through a low-pressure turbine cascade. Previous studies have shown the wake convection to be kinematic, but have not provided details of the turbulent field. The spatial resolution of these measurements has facilitated the calculation of the production of turbulent kinetic energy, and this has revealed a mechanism for turbulence production as the wake convects through the blade row. The measured ensemble-averaged velocity field confirmed the previously reported kinematics of wake convection while the measurements of the turbulence quantities showed the wake fluid to be characterized by elevated levels of turbulent kinetic energy (TKE) and to have an anisotropic structure. Based on the measured mean and turbulence quantities, the production of turbulent kinetic energy was calculated. This highlighted a TKE production mechanism that resulted in increased levels of turbulence over the rear suction surface where boundary-layer transition occurs. The turbulence production mechanism within the blade row was also observed to produce more anisotropic turbulence. Production occurs when the principal stresses within the wake are aligned with the mean strains. This coincides with the maximum distortion of the wake within the blade passage and provides a mechanism for the production of turbulence outside of the boundary layer.

Experimental and Numerical Verification of the Core-Flow in a New Low-Pressure Turbine

2016 ◽  
Author(s):  
Michael Henke ◽  
Lars Wein ◽  
Tim Kluge ◽  
Yavuz Guendogdu ◽  
Marc Heinz-Otto Biester ◽  
...  
Keyword(s):  
Flow Field ◽  
Low Pressure ◽  
Numerical Verification ◽  
Two Dimensional ◽  
Core Flow ◽  
Low Pressure Turbine ◽  
The Core ◽  
Blade Row ◽  
Unsteady Effects ◽  
Blade Row Interaction

The flow field in modern axial turbines is non-trivial and highly unsteady due to secondary flow and blade row interaction. In recent years, existing design-tools like two-dimensional flow solvers as well as fully three-dimensional CFD methods have been validated for the assumption of a quasi-steady flow field. Since the inevitable unsteadiness of the flow field has a direct impact on unsteady loss generation and work transfer, existing design methods stand in need of validation for local unsteady effects within the flow field. In order to clearly separate end-wall losses from those generated by blade row interaction within the blade passage, a two-dimensional core-flow is essential for the investigation. Hence, a new 1.5-stage high aspect ratio low pressure turbine has been designed to determine the intensity of core-flow blade row interaction for different axial gaps. First, inlet and outlet conditions of the test rig are evaluated with regard to homogeneity of the flow parameters in their radial and circumferential distributions. Secondly, the measurement data gained from rig tests have been applied as boundary conditions to time-averaged numerical computations. The flow field analysis for two different axial gaps focuses on the verification of the core flow. The authors show that the new turbine has been successfully verified using both test data and the numerical predictions, serving as a precondition for the validation of the numerical model for unsteady effects within the core-flow.

Numerical and Experimental Investigation of Aerodynamics on Flow Around a Highly Loaded Low-Pressure Turbine Blade With Flow Separation Under Steady and Periodic Unsteady Inlet Flow Condition

2016 ◽  
Author(s):  
Ali Nikparto ◽  
Meinhard T. Schobeiri
Keyword(s):  
Boundary Layer ◽  
Turbine Blade ◽  
Flow Condition ◽  
Turbulence Models ◽  
Low Pressure ◽  
Rotor Blades ◽  
Navier Stokes ◽  
Inlet Flow ◽  
Low Pressure Turbine ◽  
Highly Loaded

Understanding the behavior of flow field around a turbine blade is of importance in gas turbine engineering and it can affect the design and performance of engine elements. An important phenomena that can affect the flow regime is the effect that impinging wakes, originating from stator blades, have on the flow around rotor blades. Reynolds Averaged Navier-Stokes (RANS) equation, in conjunction with turbulence models enables us to model flow fields. This study numerically and experimentally investigates the behavior of the boundary layer development along the suction and pressure surfaces of a highly loaded low-pressure turbine blade under steady and unsteady inlet flow condition. For unsteady case a range of reduced frequencies of the incoming wakes were modeled and studied. Also it includes a comprehensive assessment of predictive capability of RANS numerical tools. To evaluate the reliability of current RANS-based numerical method, a rigorous boundary layer and heat transfer measurement were done in unsteady boundary layer cascade facility of Turbomachinery Performance and Flow Research Lab (TPFL) of Texas A&M University. Aerodynamics experiments include measuring the onset of the boundary layer, its transition, separation and re-attachment using miniature hot wire probes. All measurements were performed for different wake frequencies and flow conditions and results were compared to the obtained simulation results. Comparisons of the experimental and numerical results detail the differences in predictive capabilities of the RANS methods in terms of the locating the onset and length of separation, velocity profile inside boundary layer, velocity fluctuations.

The Effect of Pulsed Blowing on the Boundary Layer of a Highly Loaded Low Pressure Turbine Blade

2013 ◽  
Author(s):  
Marion Mack ◽  
Roland Brachmanski ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Mach Number ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Trailing Edge ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Highly Loaded

The performance of the low pressure turbine (LPT) can vary appreciably, because this component operates under a wide range of Reynolds numbers. At higher Reynolds numbers, mid and aft loaded profiles have the advantage that transition of suction side boundary layer happens further downstream than at front loaded profiles, resulting in lower profile loss. At lower Reynolds numbers, aft loading of the blade can mean that if a suction side separation exists, it may remain open up to the trailing edge. This is especially the case when blade lift is increased via increased pitch to chord ratio. There is a trend in research towards exploring the effect of coupling boundary layer control with highly loaded turbine blades, in order to maximize performance over the full relevant Reynolds number range. In an earlier work, pulsed blowing with fluidic oscillators was shown to be effective in reducing the extent of the separated flow region and to significantly decrease the profile losses caused by separation over a wide range of Reynolds numbers. These experiments were carried out in the High-Speed Cascade Wind Tunnel of the German Federal Armed Forces University Munich, Germany, which allows to capture the effects of pulsed blowing at engine relevant conditions. The assumed control mechanism was the triggering of boundary layer transition by excitation of the Tollmien-Schlichting waves. The current work aims to gain further insight into the effects of pulsed blowing. It investigates the effect of a highly efficient configuration of pulsed blowing at a frequency of 9.5 kHz on the boundary layer at a Reynolds number of 70000 and exit Mach number of 0.6. The boundary layer profiles were measured at five positions between peak Mach number and the trailing edge with hot wire anemometry and pneumatic probes. Experiments were conducted with and without actuation under steady as well as periodically unsteady inflow conditions. The results show the development of the boundary layer and its interaction with incoming wakes. It is shown that pulsed blowing accelerates transition over the separation bubble and drastically reduces the boundary layer thickness.

Profiled End-Wall Design Using an Adjoint Navier-Stokes Solver

2006 ◽  
Author(s):  
Roque Corral ◽  
Fernando Gisbert
Keyword(s):  
Kinetic Energy ◽  
Cost Function ◽  
Unstructured Mesh ◽  
Low Pressure ◽  
Navier Stokes ◽  
Low Pressure Turbine ◽  
Gradient Based ◽  
Parallel Multigrid ◽  
End Wall ◽  
Discrete Formulation

A methodology to minimize blade secondary losses by modifying turbine end-walls is presented. The optimization is addressed using a gradient-based method, where the computation of the gradient is performed using an adjoint code and the secondary kinetic energy is used as a cost function. The adjoint code is implemented on the basis of the discrete formulation of a parallel multigrid unstructured mesh Navier-Stokes solver. The results of the optimization of two end-walls of a low pressure turbine row are shown.

scholarly journals Navier-Stokes and Potential Calculations of Axial Spacing Effect on Vortical and Potential Disturbances and Gust Response in an Axial Compressor

1995 ◽  
Author(s):  
Meng-Hsuan Chung ◽  
Andrew M. Wo
Keyword(s):  
Lower Order ◽  
Spacing Effect ◽  
Axial Compressor ◽  
Interaction Effects ◽  
Moving Frame ◽  
Navier Stokes ◽  
Blade Row ◽  
Vortical Disturbance ◽  
Blade Row Interaction ◽  
Gust Response

The effect of blade row axial spacing on vortical and potential disturbances and gust response is studied for a compressor stator/rotor configuration near design and at high loadings using 2D incompressible Navier-Stokes and potential codes, both written for multistage calculations. First, vortical and potential disturbances downstream of the isolated stator in the moving frame are defined; these disturbances exclude blade row interaction effects. Then, vortical and potential disturbances for the stator/rotor configuration are calculated for axial gaps of 10%, 20%, and 30% chord. Results show that the potential disturbance is uncoupled; the potential disturbance calculated from the isolated stator configuration is a good approximation for that from the stator/rotor configuration for all three axial gaps. The vortical disturbance depends strongly on blade row interactions. Low order modes of vortical disturbance are of substantial magnitude and decay much more slowly downstream than do those of potential disturbance. Vortical disturbance decays linearly with increasing mode except very close to the stator trailing edge. For a small axial gap, lower order modes of both vortical and potential disturbances must be included to determine the rotor gust response.

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