Numerical Unsteady Flow Analysis of a Turbine Stage With Extremely Large Blade Loads

2001 ◽  
Author(s):  
Markus Jöcker ◽  
Francois X. Hillion ◽  
Torsten H. Fransson ◽  
Ulf Wåhlén
Keyword(s):  
Rocket Engine ◽  
Flow Analysis ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Design Parameters ◽  
Turbine Stage ◽  
Flow Solver ◽  
Flow Disturbances ◽  
Excitation Mechanisms ◽  
Blade Loads

This paper presents the detailed numerical analysis including parametric studies on the aerodynamic excitation mechanisms in a turbine stage due to the unsteady stator-rotor interaction. The work is part of the pre-design study of a high pressure subsonic turbine for a rocket engine turbopump. The pressure level in such turbines can be remarkably high (in this case 54 MPa inlet total pressure). Hence, large unsteady rotor blade loads can be expected, which impose difficult design requirements. The parameter studies are performed at midspan with the numerical flow solver UNSFLO, a 2D/Q3D unsteady hybrid Euler/Navier-Stokes solver. Comparisons to 2D and steady 3D results obtained with a fully viscous solver, VOLSOL, are made. The investigated design parameters are the axial gap (∼8%–29% of rotor axial chord length) and the stator vane size and count (stator-rotor pitch ratio ∼1–2.75). For the nominal case the numerical solution is analyzed regarding the contributions of potential and vortical flow disturbances at the rotor inlet using rotor gust computations. It was found that gust calculations were not capable to capture the complexity of the detected excitation mechanisms, but the possibility to reduce excitations by enforcing cancellation of the vortical and potential effects has been elaborated. The potential excitation mechanism in the present turbine stage is found dominant compared to relatively small and local wake excitation effects. The parameter studies indicate design recommendations for the axial gap and the stator size regarding the unsteady rotor load.

Numerical Unsteady Flow Analysis of a Turbine Stage With Extremely Large Blade Loads

2002 ◽  
Vol 124 (3) ◽  
pp. 429-438 ◽  
Author(s):  
Markus Jo¨cker ◽  
Francois X. Hillion ◽  
Torsten H. Fransson ◽  
Ulf Wa˚hle´n
Keyword(s):  
Rocket Engine ◽  
Flow Analysis ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Design Parameters ◽  
Turbine Stage ◽  
Flow Solver ◽  
Flow Disturbances ◽  
Excitation Mechanisms ◽  
Blade Loads

This paper presents the detailed numerical analysis including parametric studies on the aerodynamic excitation mechanisms in a turbine stage due to the unsteady stator-rotor interaction. The work is part of the predesign study of a high-pressure subsonic turbine for a rocket engine turbopump. The pressure level in such turbines can be remarkably high (in this case 54 MPa inlet total pressure). Hence, large unsteady rotor blade loads can be expected, which impose difficult design requirements. The parameter studies are performed at midspan with the numerical flow solver UNSFLO, a 2-D/Q3-D unsteady hybrid Euler/Navier-Stokes solver. Comparisons to 2-D and steady 3-D results obtained with a fully viscous solver, VOLSOL, are made. The investigated design parameters are the axial gap (∼8–29 percent of rotor axial chord length) and the stator vane size and count (stator-rotor pitch ratio ∼1–2.75). For the nominal case the numerical solution is analyzed regarding the contributions of potential and vortical flow disturbances at the rotor inlet using rotor gust computations. It was found that gust calculations were not capable to capture the complexity of the detected excitation mechanisms, but the possibility to reduce excitations by enforcing cancellation of the vortical and potential effects has been elaborated. The potential excitation mechanism in the present turbine stage is found dominant compared to relatively small and local wake excitation effects. The parameter studies indicate design recommendations for the axial gap and the stator size regarding the unsteady rotor load.

The Development of an Aerodynamic Performance Prediction Tool for Modern Axial Flow Compressor Profiles

2006 ◽  
Author(s):  
Dario Bruna ◽  
Carlo Cravero ◽  
Mark G. Turner
Keyword(s):  
Performance Prediction ◽  
Parametric Design ◽  
Flow Analysis ◽  
Axial Flow ◽  
Navier Stokes ◽  
Flow Angle ◽  
Flow Solver ◽  
Aerodynamic Loss ◽  
Axial Flow Compressor ◽  
Flow Compressor

The development of a computational tool (MP-LOS) for the aerodynamic loss modeling and prediction for axial-flow compressor blade sections is presented in this paper. A state-of-the-art quasi 3-D flow solver, MISES, has been used for the flow analysis on existing airfoil geometries in many working conditions. Different values of inlet flow angle, inlet Mach number, AVDR, Reynolds number and solidity have been chosen to investigate a possible working range. The target is a loss prediction formulation that will be introduced into throughflow or axisymmetric Navier-Stokes codes for the performance prediction of multistage axial flow compressors. The loss coefficient has been correlated to the flow parameters that have shown an influence on the profile loss for the blades under study. The proposed correlation, using the described computational approach, can be extended to any profile family with the aid of any code for the parametric design of blade profiles.

The Combined Use of Navier-Stokes Solvers and Optimization Methods for Decelerating Cascade Design

2000 ◽  
Author(s):  
Marcello Manna ◽  
Raffaele Tuccillo
Keyword(s):  
Optimization Method ◽  
Initial Guess ◽  
Computational Effort ◽  
Navier Stokes ◽  
Design Parameters ◽  
Analysis Tool ◽  
Optimization Strategy ◽  
Flow Solver ◽  
Geometrical Characteristics ◽  
Combined Use

The authors present an optimization strategy applied to decelerating cascades, with the combined use of a Navier-Stokes flow solver, correlation functions and a gradient based optimization method. In the initial stages of the searching the configurations proposed by the optimizer are mainly investigated with a semi-empirical analysis tool so to provide the flow solver with an improved initial guess. In the later stages the optimizer directly controls the flow solver. The objective of the optimization is two fold: determining the geometrical characteristics of the cascade yielding the best aerodynamic performances, and defining an appropriate cost function accounting for optimality conditions in a more general sense. The method is applied to blade profiles of the C4 type, whose geometrical characteristics are determined as a function of a few parameters (typically the camber angle, the maximum thickness to chord ratio, and the chord). By doing so the number of design parameters is substantially reduced, and the validity of the present methodology is correctly demonstrated, without loss of generality, with a limited computational effort. The examples deal with the design of decelerating cascades realizing considerable flow turning both in subsonic and transonic regimes and demonstrate the potential of the method.

Unsteady flow analysis in a high work turbine stage with two three-dimensional Navier-Stokes codes

1997 ◽  
Author(s):  
C. Hah ◽  
F.-L. Tsung ◽  
J. Loellbach ◽  
C. Hah ◽  
F.-L. Tsung ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Turbine Stage ◽  
Unsteady Flow Analysis ◽  
High Work

scholarly journals 3-D Viscous Flow Analysis of an Axial Flow Pump Impeller

1997 ◽  
Vol 3 (3) ◽  
pp. 153-161 ◽  
Author(s):  
Steven M. Miner
Keyword(s):  
Stokes Equations ◽  
Flow Analysis ◽  
Axial Flow ◽  
Flow Coefficient ◽  
Navier Stokes ◽  
Design Parameters ◽  
Pump Impeller ◽  
Flow Angle ◽  
Axial Flow Pump ◽  
Flow Pump

A commercial CFD code is used to compute the flow field within the first stage impeller of a two stage axial flow pump. The code solves the 3-D Reynolds Averaged Navier Stokes equations in a rotating cylindrical coordinate system using a standardk−εturbulence model. Stage design parameters are, rotational speed 870 rpm, flow coefficientφ=0.12, head coefficientψ=0.06, and specific speed 2.86 (8070 US). Results from the study include relative and absolute velocities, flow angles, and static and total pressures. Comparison is made to measured data available for the same impeller at two planes, one upstream of the impeller and the other downstream. The comparisons are for circumferentially averaged results and include axial and tangential velocities, impeller exit flow angle, static pressure, and total pressure. Results of this study show that the computational results closely match the shapes and magnitudes of the measured profiles, indicating that CFD can be used to accurately predict performance.

Experimental and Numerical Investigation of Optimized Blade Tip Shapes—Part II: Tip Flow Analysis and Loss Mechanisms

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Marek Pátý ◽  
Bogdan C. Cernat ◽  
Cis De Maesschalck ◽  
Sergio Lavagnoli
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Thermal Stresses ◽  
Flow Analysis ◽  
Vortical Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Blade Tip ◽  
The Impact ◽  
Blade Tip Geometry

The leakage flows within the gap between the tips of unshrouded rotor blades and the stationary casing of high-speed turbines are the source of significant aerodynamic losses and thermal stresses. In the pursuit for higher component performance and reliability, shaping the tip geometry offers a considerable potential to modulate the rotor tip flows and to weaken the heat transfer onto the blade and casing. Nevertheless, a critical shortage of combined experimental and numerical studies addressing the flow and loss generation mechanisms of advanced tip profiles persists in the open literature. A comprehensive study is presented in this two-part paper that investigates the influence of blade tip geometry on the aerothermodynamics of a high-speed turbine. An experimental and numerical campaign has been performed on a high-pressure turbine stage adopting three different blade tip profiles. The aerothermal performance of two optimized tip geometries (one with a full three-dimensional contoured shape and the other featuring a multicavity squealer-like tip) is compared against that of a regular squealer geometry. In the second part of this paper, we report a detailed analysis on the aerodynamics of the turbine as a function of the blade tip geometry. Reynolds-averaged Navier-Stokes (RANS) simulations, adopting the Spalart–Allmaras turbulence model and experimental boundary conditions, were run on high-density unstructured meshes using the numecafine/open solver. The simulations were validated against time-averaged and time-resolved experimental data collected in an instrumented turbine stage specifically setup for the simultaneous testing of multiple blade tips at scaled engine-representative conditions. The tip flow physics is explored to explain variations in turbine performance as a function of the tip geometry. Denton's mixing loss model is applied to the predicted tip gap aerodynamic field to identify and quantify the loss reduction mechanisms of the alternative tip designs. An advanced method based on the local triple decomposition of relative motion is used to track the location, size and intensity of the vortical flow structures arising from the interaction between the tip leakage flow and the main gas path. Ultimately, the comparison between the unconventional tip profiles and the baseline squealer tip highlights distinct aerodynamic features in the associated gap flow field. The flow analysis provides guidelines for the designer to assess the impact of specific tip design strategies on the turbine aerodynamics and rotor heat transfer.

Experimental and Numerical Investigation of Optimized Blade Tip Shapes: Part II — Tip Flow Analysis and Loss Mechanisms

2018 ◽  
Author(s):  
Marek Pátý ◽  
Bogdan Cernat ◽  
Cis De Maesschalck ◽  
Sergio Lavagnoli
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Thermal Stresses ◽  
Flow Analysis ◽  
Vortical Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Blade Tip ◽  
The Impact ◽  
Blade Tip Geometry

The leakage flows within the gap between the tips of unshrouded rotor blades and the stationary casing of high-speed turbines are the source of significant aerodynamic losses and thermal stresses. In the pursuit for higher component performance and reliability, shaping the tip geometry offers a considerable potential to modulate the rotor tip flows and to weaken the heat transfer onto the blade and casing. Nevertheless, a critical shortage of combined experimental and numerical studies addressing the flow and loss generation mechanisms of advanced tip profiles persists in the open literature. A comprehensive study is presented in this two-part paper that investigates the influence of blade tip geometry on the aerother-modynamics of a high-speed turbine. An experimental and numerical campaign has been performed on a high-pressure turbine stage adopting three different blade tip profiles. The aerothermal performance of two optimized tip geometries (one with a full three-dimensional contoured shape and the other featuring a multi-cavity squealer-like tip) is compared against that of a regular squealer geometry. In the second part of this paper, we report a detailed analysis on the aerodynamics of the turbine as a function of the blade tip geometry. Reynolds-averaged Navier-Stokes simulations, adopting the Spalart-Allmaras turbulence model and experimental boundary conditions, were run on high-density unstructured meshes using the Numeca FINE/Open solver. The simulations were validated against time-averaged and time-resolved experimental data collected in an instrumented turbine stage specifically set up for the simultaneous testing of multiple blade tips at scaled engine-representative conditions. The tip flow physics is explored to explain variations in turbine performance as a function of the tip geometry. Denton’s mixing loss model is applied to the predicted tip gap aerodynamic field to identify and quantify the loss reduction mechanisms of the alternative tip designs. An advanced method based on the local triple decomposition of relative motion is used to track the location, size and intensity of the vortical flow structures arising from the interaction between the tip leakage flow and the main gas path. Ultimately, the comparison between the unconventional tip profiles and the baseline squealer tip highlights distinct aerodynamic features in the associated gap flow field. The flow analysis provides guidelines for the designer to assess the impact of specific tip design strategies on the turbine aerodynamics and rotor heat transfer.

Automatic Three-Dimensional Optimisation of a Modern Tandem Compressor Vane

2014 ◽  
Author(s):  
R. C. Schlaps ◽  
S. Shahpar ◽  
V. Gümmer
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Trust Region ◽  
Automatic Generation ◽  
Navier Stokes ◽  
Design Parameters ◽  
High Fidelity ◽  
Stall Margin ◽  
Design Choice ◽  
Multipoint Approximation

In order to increase the performance of a modern gas turbine, compressors are required to provide higher pressure ratio and avoid incurring higher losses. The tandem aerofoil has the potential to achieve a higher blade loading in combination with lower losses compared to single vanes. The main reason for this is due to the fact that a new boundary layer is generated on the second blade surface and the turning can be achieved with smaller separation occurring. The lift split between the two vanes with respect to the overall turning is an important design choice. In this paper an automated three-dimensional optimisation of a highly loaded compressor stator is presented. For optimisation a novel methodology based on the Multipoint Approximation Method (MAM) is used. MAM makes use of an automatic design of experiments, response surface modelling and a trust region to represent the design space. The CFD solutions are obtained with the high-fidelity 3D Navier-Stokes solver HYDRA. In order to increase the stage performance the 3D shape of the tandem vane is modified changing both the front and rear aerofoils. Moreover the relative location of the two aerofoils is controlled modifying the axial and tangential relative positions. It is shown that the novel optimisation methodology is able to cope with a large number of design parameters and produce designs which performs better than its single vane counterpart in terms of efficiency and numerical stall margin. One of the key challenges in producing an automatic optimisation process has been the automatic generation of high-fidelity computational meshes. The multi block-structured, high-fidelity meshing tool PADRAM is enhanced to cope with the tandem blade topologies. The wakes of each aerofoil is properly resolved and the interaction and the mixing of the front aerofoil wake and the second tandem vane are adequately resolved.

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