Computational Extrapolation of Turbine Sealing Effectiveness From Test Rig to Engine Conditions

2012 ◽  
Author(s):  
Roy Teuber ◽  
Mike Wilson ◽  
Yan Sheng Li ◽  
Gary Lock ◽  
John Maltson ◽  
...  
Keyword(s):  
Mach Number ◽  
Pressure Coefficient ◽  
Navier Stokes ◽  
Radial Clearance ◽  
Driving Mechanism ◽  
Test Rig ◽  
Flow Rates ◽  
Axial Clearance ◽  
The University ◽  
Good Agreement

The commercial computational fluid dynamics code ANSYS CFX 12.1 has been employed to carry out Unsteady Reynolds Averaged Navier Stokes (URANS) computations to investigate the fluid mechanics of two different rim-seal geometries in a 3D model of a turbine stage. The mainstream annulus, seal and wheel-space geometries are based on an experimental test rig used at the University of Bath. The calculated peak-to-trough pressure difference in the annulus, which is the main driving mechanism for ingestion, is in good agreement with experimental measurements. There is also good agreement between the computed and measured swirl ratios in the wheel-space. Computed values of concentration-based sealing effectiveness are obtained over a range of sealing flow rates for both an axial-clearance and a radial clearance rim-seal. Good agreement with gas concentration measurements is found for the axial-clearance seal over a certain range of sealing flow rates. Some under-prediction of the amount of ingestion for the radial-clearance seal is obtained. The computed mainstream pressure coefficient increases progressively with mainstream Mach number in moving from quasi-incompressible experimental rig conditions to the compressible flow conditions encountered in engines. It is shown that the minimum sealing flow rate required to prevent ingestion increases as mainstream Mach number increases. A scaling method is proposed to allow sealing flow rates to prevent ingestion obtained from low Mach number experiments to be extrapolated to engine-representative conditions.

Experimental Measurements of Ingestion Through Turbine Rim Seals—Part II: Rotationally Induced Ingress

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Carl M. Sangan ◽  
Oliver J. Pountney ◽  
Kunyuan Zhou ◽  
J. Michael Owen ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Experimental Results ◽  
Radial Clearance ◽  
Rotating Fluid ◽  
Flow Rates ◽  
Hot Gas ◽  
Wide Range ◽  
The Common ◽  
Axial Clearance ◽  
Better Than ◽  
Good Agreement

Part I of this two-part paper presented experimental results for externally-induced (EI) ingress, where the ingestion of hot gas through the rim seal into the wheel-space of a gas turbine is controlled by the circumferential variation of pressure in the external annulus. In Part II, experimental results are presented for rotationally-induced (RI) ingress, where the ingestion is controlled by the pressure generated by the rotating fluid in the wheel-space. Although EI ingress is the common form of ingestion through turbine rim seals, RI ingress or combined ingress (where EI and RI ingress are both significant) is particularly important for double seals, where the pressure asymmetries are attenuated in the annular space between the inner and outer seals. In this paper, the sealing effectiveness was determined from concentration measurements, and the variation of effectiveness with sealing flow rate was compared with theoretical curves for RI ingress obtained from an orifice model. Using a nondimensional sealing parameter Φ0 the data could be collapsed onto a single curve, and the theoretical variation of effectiveness with Φ0 was in very good agreement with the data for a wide range of flow rates and rotational speeds. It was shown that the sealing flow required to prevent RI ingress was much less than that needed for EI ingress, and it was also shown that the effectiveness of a radial-clearance seal is significantly better than that for an axial-clearance seal for both EI and RI ingress.

Experimental Measurements of Ingestion Through Turbine Rim Seals: Part 2—Rotationally-Induced Ingress

2011 ◽  
Author(s):  
Carl M. Sangan ◽  
Kunyuan Zhou ◽  
J. Michael Owen ◽  
Oliver J. Pountney ◽  
Mike Wilson ◽  
...  
Keyword(s):  
Experimental Results ◽  
Radial Clearance ◽  
Rotating Fluid ◽  
Flow Rates ◽  
Hot Gas ◽  
Wide Range ◽  
The Common ◽  
Axial Clearance ◽  
Better Than ◽  
Good Agreement

Part 1 of this two-part paper presented experimental results for externally-induced (EI) ingress, where the ingestion of hot gas through the rim seal into the wheel-space of a gas turbine is controlled by the circumferential variation of pressure in the external annulus. In Part 2, experimental results are presented for rotationally-induced (RI) ingress, where the ingestion is controlled by the pressure generated by the rotating fluid in the wheel-space. Although EI ingress is the common form of ingestion through turbine rim seals, RI ingress or combined ingress (where EI and RI ingress are both significant) is particularly important for double seals, where the pressure asymmetries are attenuated in the annular space between the inner and outer seals. In this paper, the sealing effectiveness was determined from concentration measurements, and the variation of effectiveness with sealing flow rate was compared with theoretical curves for RI ingress obtained from an orifice model. Using a nondimensional sealing parameter, Φ0, the data could be collapsed onto a single curve, and the theoretical variation of effectiveness with Φ0 was in very good agreement with the data for a wide range of flow rates and rotational speeds. It was shown that the sealing flow required to prevent RI ingress was much less than that needed for EI ingress, and it was also shown that the effectiveness of a radial-clearance seal is significantly better than that for an axial-clearance seal for both EI and RI ingress.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

scholarly journals Development of a new test rig for the analysis of hydrodynamic bearings for rotors of microGT

2019 ◽  
Vol 113 ◽  
pp. 03002
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Gas Turbines ◽  
Dynamic Interaction ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Test Rig ◽  
Small Clearance ◽  
Stiffness And Damping ◽  
Good Agreement

The aim of the present work is to design a test rig suited to investigate the dynamic interaction between rotor and hydrodynamic journal bearings in micro gas turbines (microGT), i.e. with reference to small bearings (diameter in the order of ten millimeters). Particularly, the device is capable of measuring the journal location. Therefore, the journal motion due to rotor vibrations can be displayed, in order to assess performance as well as stiffness and damping of the bearings. The new test rig is based on Bently Nevada Rotor Kit (RK), but substantial modifications are carried out. Indeed, the relative radial clearance of the original RK bearings is about 2/100, while it is in the order of 1/1000 in industrial bearings. Therefore, the same RK bearings are employed in the new test rig, but a new shaft has been designed in order to reduce the original clearance. The new shaft enables us to study the bearing behaviour for different clearances, as it is equipped with interchangeable journals. The experimental data yielded by the new test rig are compared with numerical results. These are obtained by means of a suitable finite element (FEM) code developed by our research group. It allows the Thermo Elasto-HydroDynamic (TEHD) analysis of the bearing in static and dynamic conditions. In the present paper, bearing static performances are analysed in order to assess the reliability of the journal location predictions by comparing numerical and experimental results. Such comparisons are presented for both large and small clearance bearings of original and modified RK, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance equal to 8/1000). Nevertheless, rotor alignment is quite difficult with small clearance bearings and a completely new test rig is designed for future experiments.

scholarly journals A DES Procedure Applied to a Wall-Mounted Hump

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Radoslav Bozinoski ◽  
Roger L. Davis
Keyword(s):  
Pressure Coefficient ◽  
Three Dimensional ◽  
Synthetic Jets ◽  
Navier Stokes ◽  
Separation Region ◽  
Detached Eddy Simulation ◽  
Three Dimensional Flow ◽  
Eddy Simulation ◽  
Turbulent Separation ◽  
Good Agreement

This paper describes a detached-eddy simulation (DES) for the flow over a wall-mounted hump. The Reynolds number based on the hump chord isRec=9.36×105with an in-let Mach number of 0.1. Solutions of the three-dimensional Reynolds-averaged Navier-Stokes (RANS) procedure are obtained using the Wilcoxk−ωequations. The DES results are obtained using the model presented by Bush and Mani and are compared with RANS solutions and experimental data from NASA's 2004 Computational Fluid Dynamics Validation on Synthetic Jets and Turbulent Separation Control Workshop. The DES procedure exhibited a three-dimensional flow structure in the wake, with a 13.65% shorter mean separation region compared to RANS and a mean reattachment length that is in good agreement with experimental measurements. DES predictions of the pressure coefficient in the separation region also exhibit good agreement with experiment and are more accurate than RANS predictions.

A Navier-Stokes Analysis of the Stall Flutter Characteristics of the Buffum Cascade

2000 ◽  
Author(s):  
Stefan Weber ◽  
Max F. Platzer
Keyword(s):  
Mach Number ◽  
Turbulence Modeling ◽  
Separation Bubble ◽  
Leading Edge ◽  
Navier Stokes ◽  
Implicit Time ◽  
Fully Implicit ◽  
High Incidence ◽  
Stall Flutter ◽  
Good Agreement

Numerical stall flutter prediction methods are highly needed as modern jet engines require blade designs close to the stability boundaries of the performance map. A Quasi-3D Navier-Stokes code is used to analyze the flow over the oscillating cascade designed and manufactured by Pratt & Whitney, and studied at the NASA Glenn Research Center by Buffum et al. The numerical method solves for the governing equations with a fully implicit time-marching technique in a single passage by making use of a direct-store, periodic boundary condition. For turbulence modeling the Baldwin-Lomax model is used. To account for transition, the criterion to predict the onset location suggested by Baldwin and Lomax is incorporated. Buffum et al. investigated two incidence cases for three different Mach numbers. The low-incidence case at a Mach number of 0.5 exhibited the formation of small separation bubbles at reduced oscillation frequencies of 0.8 and 1.2. For this case the present approach yielded good agreement with the steady and oscillatory measurements. At high-incidence at the same Mach number of 0.5 the measured steady-state pressure distribution and the separation bubble on the upper surface was also found in good agreement with the experiment. But computations for oscillations at high-incidence failed to predict the negative damping contribution caused by the leading edge separation.

Numerical Flow Prediction in Inlet Pipe of Vertical Inline Pump

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
Christopher Stephen ◽  
Shouqi Yuan ◽  
Ji Pei ◽  
Xing Cheng G
Keyword(s):  
Stokes Equations ◽  
Reverse Flow ◽  
Pressure Coefficient ◽  
Navier Stokes ◽  
Mean Flow ◽  
Inlet Pipe ◽  
Navier Stokes Equations ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean ◽  
Good Agreement

For a pump, the inlet condition of flow determines the outlet conditions of fluid (i.e., energy). As a rule to minimize the losses at the entry of pump, the bends should be avoided as one of the methods. But for the case of vertical inline pump, it is unavoidable in order to save the space for installation. For the purpose of investigation in inlet pipe of vertical inline pump, the unsteady Reynolds-averaged Navier–Stokes equations are solved using the computational fluid dynamics (CFD) code. The results have been shown that there is a good agreement between the performance characteristics obtained from the simulation and experiments. The velocity coefficient from the simulation along the inlet pipe sections is well matched with the theoretical values and found to have variation near the exit of inlet pipe. The pressure and velocity coefficients studies depict the flow physics at each section along with the study of helicity at the exit of inlet pipe to determine the recirculation effects. It is observed that the vortices associated with the motion of the particles are moved toward the surfaces and are more intense than the mean flow. The trends of pressure coefficient at the exit of inlet pipe were addressed with reference to the various flow rates for eight set of radial lines. Hence, this work concludes that for inlet pipe, the generation of circulation was due to the stream path and the reverse flow from the impeller and was reconfirmed with the literature.

A Shock Loss Model for Supersonic Compressor Cascades

1999 ◽  
Vol 121 (1) ◽  
pp. 28-35 ◽  
Author(s):  
G. S. Bloch ◽  
W. W. Copenhaver ◽  
W. F. O’Brien
Keyword(s):  
Mach Number ◽  
Boundary Layer Separation ◽  
Navier Stokes ◽  
Flow Angle ◽  
Loss Model ◽  
Viscous Profile ◽  
Loss Models ◽  
Profile Loss ◽  
Shock Loss ◽  
Good Agreement

Loss models used in compression system performance prediction codes are often developed from the study of two-dimensional cascades. In this paper, compressible fluid mechanics has been applied to the changes in shock geometry that are known to occur with back pressure for unstarted operation of supersonic compressor cascades. This physics-based engineering shock loss model is applicable to cascades with arbitrary airfoil shapes. Predictions from the present method have been compared to measurements and Navier–Stokes analyses of the LO30-4 and L030-6 cascades, and very good agreement was demonstrated for unstarted operation. A clear improvement has been demonstrated over previously published shock loss models for unstarted operation, both in the accuracy of the predictions and in the range of applicability. The dramatic increase in overall loss with increasing inlet flow angle is shown to be primarily the result of increased shock loss, and much of this increase is caused by the detached bow shock. For a given Mach number, the viscous profile loss is nearly constant over the entire unstarted operating range of the cascade, unless a shock-induced boundary layer separation occurs near stall. Shock loss is much more sensitive to inlet Mach number than is viscous profile loss.

Effect of Various Tip Clearance Squealer Design on Turbine Stage Efficiency

2015 ◽  
Author(s):  
Nikolay Lomakin ◽  
Andrey Granovskiy ◽  
Vladimir Shchaulov ◽  
Jaroslaw Szwedowicz
Keyword(s):  
Tip Clearance ◽  
Navier Stokes ◽  
Radial Clearance ◽  
Turbine Stage ◽  
Test Rig ◽  
Numerical Investigations ◽  
Blade Cascade ◽  
The Impact ◽  
Stage Efficiency ◽  
Insight Into

This paper presents investigation of nine tip squealer design variants based on full 3D Navier-Stokes CFD calculations. In particular two main design features have been studied: the impact of relative squealer cavity rim extension and the impact of pressure side squealer cavity rim inclination on stage efficiency. All these cases have been compared for two values of relative radial gaps 0.6% and 1.36%. Obtained numerical results were validated against the experimental data measured on the E3 blade cascade test rig given in the open literature. As the overall outcome for these numerical investigations two zones with different vortex structures and different sealing features have been found. Moreover the size of these zones determines the level of the tip clearance leakage and losses for various tip squealer designs. The obtained loss values and corresponding change of the stage efficiency level as well as flow structure details were compared for all studied cases, providing insight into turbine stage aerodynamics with respect to minimal and maximal radial clearance.

The Calculation of Deviation Angle in Axial-Flow Compressor Cascades

1983 ◽  
Vol 105 (3) ◽  
pp. 474-479 ◽  
Author(s):  
L. C. Wang ◽  
R. Hetherington ◽  
A. Goulas
Keyword(s):  
Stokes Equations ◽  
Pressure Coefficient ◽  
Axial Flow ◽  
Navier Stokes ◽  
Angle Of Incidence ◽  
Deviation Angle ◽  
Axial Flow Compressor ◽  
Flow Compressor ◽  
Vorticity Transport ◽  
Good Agreement

The deviation angles of axial flow compressor cascades have been predicted by solving the Reynolds averaged fully turbulent Navier-Stokes equations. A finite element method has been used. To close the problem an algebraic eddy viscosity turbulent model has been chosen. The introduction of the idea of vorticity to the governing equation enables the establishment of a relation between the entropy and the vorticity fields, and the vorticity transport differential equation in the stream function-vorticity method is replaced by a differential operation. A series of calculations have been carried out to examine the influence of cascade geometry on the devotion angle. Very good agreement has been obtained for small angles of incidence with the correlations produced by NASA and using Carter’s rule. Good agreement has also been shown for the variation of deviation angle with the angle of incidence with the experimental data of Felix and Emery, as well as for the distribution of the pressure coefficient along the blade axial chord.

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