scholarly journals Parametric study on the aeroelastic stability of rotor seals

2019 ◽  
Vol 3 ◽  
pp. 569-579 ◽  
Author(s):  
Qingyuan Zhuang ◽  
Ronnie Bladh ◽  
Erik Munktell ◽  
Yong Lee
Keyword(s):  
Design Space Exploration ◽  
Rapid Development ◽  
Pressure Ratio ◽  
Numerical Approach ◽  
Travelling Wave ◽  
Navier Stokes ◽  
High Fidelity ◽  
Three Dimension ◽  
Wave Direction ◽  
Labyrinth Seals

Labyrinth seals are widely used in rotating machinery and can be prone to aeroelastic instabilities. The rapid development of computational fluid dynamics now provides a high-fidelity approach for predicting the aeroelastic behavior of labyrinth seals in three dimension and exhibits great potential within industrial application, especially during the detailed design stages. In the current publication a time-marching unsteady Reynolds-averaged Navier-Stokes solver was employed to study the various historically identified parameters that have essential influence on the stability of labyrinth seals. The findings from the numerical approach agree well with analytical criteria in determining the overall stability of the seal structure while being able to capture the acoustic behavior of the upstream or downstream large cavities and its influence on the inter-fin cavities. The high-fidelity approach provides additional insights on the effects of nodal diameter, travelling wave direction, pressure ratio, and the linearity of the phenomenon for relatively large vibration amplitudes, all of which can aid during the design space exploration.

Investigations on the Discharge and Total Temperature Increase Characteristics of the Labyrinth Seals With Honeycomb and Smooth Lands

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Xin Yan ◽  
Jun Li ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Temperature Increase ◽  
Pressure Ratio ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
Total Temperature ◽  
Direct Loss ◽  
Sufficient Precision

The viscous work generated by the rotating components of a seal not only represents a direct loss of power but also causes an increase in the total temperature of fluid (windage effect). In order to study the discharge and total temperature increase characteristics of the stepped labyrinth seals with smooth and honeycomb lands, 3D Reynolds-averaged Navier–Stokes solutions from CFX is used in this work. At first, the influences of the inlet preswirl, leakage flow rate, and rotational speed on the total temperature increase in the convergent and divergent stepped labyrinth seals with smooth and honeycomb lands are conducted. The obtained 3D numerical results are well in agreement with the referenced experimental data. It shows that the utilized numerical approach has sufficient precision to predict the total temperature increase in seals. Then, a range of pressure ratios and four sizes of sealing clearance are performed to investigate the effects of sealing clearances and pressure ratio impact on the discharge and total temperature increase of the stepped labyrinth seals with honeycomb and smooth liners.

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.

Effects of Pressure Ratio and Sealing Clearance on Leakage Flow Characteristics in the Rotating Honeycomb Labyrinth Seal

2007 ◽  
Author(s):  
Jun Li ◽  
Xin Yan ◽  
Guojun Li ◽  
Zhenping Feng
Keyword(s):  
Pressure Ratio ◽  
Flow Characteristics ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Aerodynamic Efficiency ◽  
Flow Losses ◽  
Leakage Flow Rate ◽  
Swirl Velocity

Honeycomb stepped labyrinth seals in turbomachinery enhance aerodynamic efficiency by reducing leakage flow losses through the clearance between rotating and stationary components. The influence of pressure ratio and sealing clearance on the leakage flow characteristics in the honeycomb stepped labyrinth seal is numerically determined. The geometries investigated represent designs of the honeycomb labyrinth seal typical for modern turbomachinery. The leakage flow fields in the honeycomb and smooth stepped labyrinth seals are obtained by the Reynolds-Averaged Navier-Stokes solution using the commercial software FLUENT. Numerical simulations covered a range of pressure ratio and three sizes of sealing clearance for the honeycomb and smooth stepped labyrinth seals. The numerical discharge coefficients of the non-rotating honeycomb and smooth stepped labyrinth seals are in good agreement with previous experimental data. In addition rotational effects are also taken into account in numerical computations. The numerical results show that the leakage flow rate increases with the increasing pressure ratio at the fixed sealing clearance for the rotating and non-rotating honeycomb labyrinth seal. The influence of the sealing clearance on the leakage flow pattern for the rotating and non-rotating honeycomb labyrinth seal are observed. Moreover, the similar leakage flow rates are obtained at the same flow condition between the rotating and non-rotating honeycomb labyrinth seal due to the honeycomb acts to kill swirl velocity development for the rotating honeycomb labyrinth seal.

scholarly journals A Laplace transform finite difference scheme for the Fisher-KPP equation

2021 ◽  
Vol 15 ◽  
pp. 174830262199958
Author(s):  
Colin L Defreitas ◽  
Steve J Kane
Keyword(s):  
Finite Difference ◽  
Laplace Transform ◽  
Difference Scheme ◽  
Finite Difference Scheme ◽  
Finite Difference Methods ◽  
Reaction Diffusion ◽  
Numerical Approach ◽  
Travelling Wave ◽  
Reaction Diffusion Equation ◽  
Kpp Equation

This paper proposes a numerical approach to the solution of the Fisher-KPP reaction-diffusion equation in which the space variable is developed using a purely finite difference scheme and the time development is obtained using a hybrid Laplace Transform Finite Difference Method (LTFDM). The travelling wave solutions usually associated with the Fisher-KPP equation are, in general, not deemed suitable for treatment using Fourier or Laplace transform numerical methods. However, we were able to obtain accurate results when some degree of time discretisation is inbuilt into the process. While this means that the advantage of using the Laplace transform to obtain solutions for any time t is not fully exploited, the method does allow for considerably larger time steps than is otherwise possible for finite-difference methods.

Interaction Between Coriolis Forces and Mistuning on a Cyclic Symmetric Structure With Geometrical Nonlinearity

2020 ◽  
Author(s):  
Anthony Tacher ◽  
Fabrice Thouverez ◽  
Jason Armand
Keyword(s):  
Standing Wave ◽  
Geometrical Nonlinearity ◽  
Numerical Approach ◽  
Travelling Wave ◽  
Lumped Parameter Model ◽  
Coriolis Forces ◽  
High Speeds ◽  
Symmetric Structure ◽  
Lumped Parameter ◽  
Cyclic Symmetric

Abstract An investigation of the interaction between Coriolis forces and mistuning on a cyclic symmetric structure is presented in this paper. The sensitivity of the eigenvalues and eigenvectors to mistuning is first studied with the perturbation method. A lumped parameter model is used to perform a modal analysis using a numerical approach after which geometrical nonlinearity is added to compare behavior with the linear case. Two different modes are thoroughly investigated for different rotational speeds, the first with an eigenvalue isolated from the others and the second presenting a frequency veering zone. The evolution from a standing wave domination at low speeds to a travelling wave domination at high speeds is observed for the isolated mode, whereas a standing wave domination remains around the veering zone for the second mode studied. It is also shown that the geometrical nonlinearity reinforces the mistuning effect versus the Coriolis forces.

Investigation of Recirculating Casing Treatment for Low-Pressure Ratio Mixed-Flow Micro-Compressor

2020 ◽  
Author(s):  
Kewei Xu ◽  
Gecheng Zha
Keyword(s):  
Pressure Ratio ◽  
Numerical Approach ◽  
Efficiency Loss ◽  
Stall Margin ◽  
Design Point ◽  
Casing Treatment ◽  
Final Design ◽  
Upstream Flow ◽  
Total Pressure Ratio ◽  
Good Agreement

Abstract This paper investigates the recirculating casing treatment (RCT) of a low total pressure ratio micro-compressor to achieve stall margin enhancement while minimizing the design point efficiency penalty. Three RCT injection and extraction configurations are studied, including combined slot-duct, ducts only, and slot only. The numerical approach is validated with a tested micro-compressor using RCT. A very good agreement is achieved between the predicted speedlines and the measured results. To minimize the design point efficiency loss, it is observed that the optimal location of extraction and injection is where the recirculated flow rate can be minimized at the design point. To maximize stall margin, extraction location should favor minimizing the tip blockage such as at the location where the tip flow separation of the baseline blade is fully developed. In addition, the slot configuration that generates pre-swirl to the upstream flow is beneficial to improve stall margin due to reduced incidence. The highest stall margin enhancement achieved is 9.49% with the slot geometry that has the extraction at the 62%C chordwise location, but has a design point efficiency loss of 1.9%. Overall, a small efficiency penalty of 0.6% at the design point is achieved for the final design with the stall margin increased by 6.2%.

Aero-Thermal Characterization of Accelerating and Diffusing Passages Downstream of Rotating Detonation Combustors

2021 ◽  
Author(s):  
James Braun ◽  
Guillermo Paniagua ◽  
Donald Ferguson
Keyword(s):  
Pressure Ratio ◽  
Thermal Characterization ◽  
Navier Stokes ◽  
Computational Time ◽  
Efficiency Gain ◽  
Precise Knowledge ◽  
Potential Gain ◽  
One Step ◽  
Turbine Design ◽  
Rotating Detonation

Abstract Cycle benefits of rotating detonation engines show up to five percentage points of efficiency gain for low-pressure ratio engines. An optimal integration between the combustor and the turbine needs to be guaranteed to realize this potential gain. The rotating detonation combustor (RDC) exhausts transonic flow with shocks rotating at frequencies ranging from a few to tens of kilohertz depending on the number of present waves. Hence, the turbine design requires precise knowledge of the fluctuations and losses downstream of the combustor. This paper focuses on the quantification of fluctuations and losses for accelerating and diffusing passages. The analysis of the combustor is performed via reactive unsteady Reynolds Averaged Navier-Stokes (URANS) simulations. The unsteady RANS equations are solved via CFD++ from Metacomp with a one-step reaction mechanism for an H2-air mixture. The resolving of the boundary layer is achieved with a structured mesh of around 36 million cells. Inlet pressure of 10 bar and two different back pressures are applied to the combustor to model the interconnection with downstream turbines. Finally, we present and assess a methodology to reduce the computational time to model these passages ten times.

Effect of Outer Fin Axial Gap on the Sealing Effectiveness and Fluid Dynamics of Radial Rim Seal

2017 ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Liming Song ◽  
Qing Gao ◽  
Xin Yan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Flow Rate ◽  
Gas Turbines ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Navier Stokes ◽  
Hot Gas

The modern gas turbine is widely applied in the aviation propulsion and power generation. The rim seal is usually designed at the periphery of the wheel-space and prevented the hot gas ingestion in modern gas turbines. The high sealing effectiveness of rim seal can improve the aerodynamic performance of gas turbines and avoid of the disc overheating. Effect of outer fin axial gap of radial rim seal on the sealing effectiveness and fluid dynamics was numerically investigated in this work. The sealing effectiveness and fluid dynamics of radial rim seal with three different outer fin axial gaps was conducted at different coolant flow rates using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and SST turbulent model solutions. The accuracy of the presented numerical approach for the prediction of the sealing performance of the turbine rim seal was demonstrated. The obtained results show that the sealing effectiveness of radial rim seal increases with increase of coolant flow rate at the fixed axial outer fin gap. The sealing effectiveness increases with decrease of the axial outer fin gap at the fixed coolant flow rate. Furthermore, at the fixed coolant flow rate, the hot gas ingestion increases with the increase of the axial outer fin gap. This flow behavior intensifies the interaction between the hot gas and coolant flow at the clearance of radial rim seal. The preswirl coefficient in the wheel-space cavity is also illustrated to analyze the flow dynamics of radial rim seal at different axial outer fin gaps.

Turbine Airfoil Heat Transfer Predictions Using CFD

2005 ◽  
Author(s):  
Anil K. Tolpadi ◽  
James A. Tallman ◽  
Lamyaa El-Gabry
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulence Modeling ◽  
Three Dimensional ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Design System ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Airfoils ◽  
Typical Design

Conventional heat transfer design methods for turbine airfoils use 2-D boundary layer codes (BLC) combined with empiricism. While such methods may be applicable in the mid span of an airfoil, they would not be very accurate near the end-walls and airfoil tip where the flow is very three-dimensional (3-D) and complex. In order to obtain accurate heat transfer predictions along the entire span of a turbine airfoil, 3-D computational fluid dynamics (CFD) must be used. This paper describes the development of a CFD based design system to make heat transfer predictions. A 3-D, compressible, Reynolds-averaged Navier-Stokes CFD solver with k-ω turbulence modeling was used. A wall integration approach was used for boundary layer prediction. First, the numerical approach was validated against a series of fundamental airfoil cases with available data. The comparisons were very favorable. Subsequently, it was applied to a real engine airfoil at typical design conditions. A discussion of the features of the airfoil heat transfer distribution is included.

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