Unsteady Effects on Transonic Turbine Blade-Tip Heat Transfer

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Nicholas R. Atkins ◽  
Steven J. Thorpe ◽  
Roger W. Ainsworth
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Flow Distribution ◽  
Potential Interaction ◽  
Rotor Blades ◽  
Time Varying ◽  
Trailing Edge ◽  
Blade Tip ◽  
Transonic Turbine ◽  
The Impact

In a gas turbine engine the blade tips of the high-pressure turbine are exposed to high levels of convective heat transfer, because of the so-called tip-leakage phenomenon. The blade-lift distribution is known to control the flow distribution in the blade–tip gap. However, the interaction between upstream nozzle guide vanes and the rotor blades produces a time-varying flow field that induces varying flow conditions around the blade and within the tip gap. Extensive measurements of the unsteady blade-tip heat transfer have been made in an engine representative transonic turbine. These include measurements along the mean camber line of the blade tip, which have revealed significant variation in both time-mean and time-varying heat flux. The influences of potential interaction and the vane trailing edge have been observed. Numerical calculations of the turbine stage using a Reynolds-averaged-Navier-Stokes-based computational fluid dynamics code have also been conducted. In combination with the experimental results, these have enabled the time-varying flow field to be probed in the blade-relative frame of reference. This has allowed a deeper analysis of the unsteady heat-transfer data, and the quantification of the impact of vane potential field and vane trailing edge interaction on the tip-region flow and heat transfer. In particular, the separate effects of time-varying flow temperature and heat-transfer coefficient have been established.

Unsteady Effects on Transonic Turbine Blade-Tip Heat Transfer

2008 ◽  
Author(s):  
N. R. Atkins ◽  
S. J. Thorpe ◽  
R. W. Ainsworth
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Flow Distribution ◽  
Potential Interaction ◽  
Rotor Blades ◽  
Time Varying ◽  
Trailing Edge ◽  
Blade Tip ◽  
Transonic Turbine ◽  
The Impact

In a gas turbine engine the blade-tips of the high-pressure turbine are exposed to high levels of convective heat transfer due to the so-called tip-leakage phenomenon. The blade-lift distribution is known to control the flow distribution in the blade tip-gap. However, the interaction between upstream nozzle guide vanes and the rotor blades produces a time-varying flow field that induces varying flow conditions around the blade and within the tip-gap. Extensive measurements of the unsteady blade-tip heat transfer have been made in an engine representative transonic turbine. These include measurements along the mean camber line of the blade-tip which have revealed significant variation in both time-mean and time-varying heat flux. The influences of potential interaction and the vane trailing edge have been observed. Numerical calculations of the turbine stage using a Reynolds averaged Navier-Stokes based computational fluid dynamics code have also been conducted. In combination with the experimental results these have enabled the time-varying flow-field to be probed in the blade-relative frame of reference. This has allowed a deeper analysis of the unsteady heat transfer data, and the quantification of the impact of vane potential field and vane trailing edge interaction on the tip-region flow and heat transfer. In particular, the separate effects of time-varying flow temperature and heat transfer coefficient have been established.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

Unsteady Rotor Heat Transfer in a Transonic Turbine Stage

2002 ◽  
Author(s):  
F. Didier ◽  
R. De´nos ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Convective Heat Transfer Coefficient ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Trailing Edge ◽  
Time Resolved ◽  
Number Distribution ◽  
Transonic Turbine

This experimental investigation reports the convective heat transfer coefficient around the rotor of a transonic turbine stage. Both time-resolved and time-averaged aspects are addressed. The measurements are performed around the rotor blade at 15%, 50% and 85% span as well as on the rotor tip and the hub platform. Four operating conditions are tested covering two Reynolds numbers and three pressure ratios. The tests are performed in the compression tube turbine test rig CT3 of the von Karman Institute, allowing a correct simulation of the operating conditions encountered in modern aero-engines. The time-averaged Nusselt number distribution shows the strong dependence on both blade Mach number distribution and Reynolds number. The time-resolved heat transfer rate is mostly dictated by the vane trailing edge shock impingement on the rotor boundary layer. The shock passage corresponds to a sudden heat transfer increase. The effects are more pronounced in the leading edge region. The increase of the stage pressure ratio causes a stronger vane trailing edge shock and thus larger heat transfer fluctuations. The influence of the Reynolds number is hardly visible.

Numerical Simulation and Experiment on the Electrolyte Flow Distribution for All Vanadium Redox Flow Battery

2011 ◽  
Vol 236-238 ◽  
pp. 604-607 ◽  
Author(s):  
Jin Qing Chen ◽  
Bao Guo Wang ◽  
Hong Ling Lv
Keyword(s):  
Flow Field ◽  
Flow Distribution ◽  
Parallel Flow ◽  
Vanadium Redox Flow Battery ◽  
Redox Flow Battery ◽  
Flow Battery ◽  
Electrolyte Flow ◽  
Cfd Method ◽  
The Impact ◽  
Vanadium Redox

The electrolyte flow states of all vanadium redox flow battery (VRB) have a direct effect on the battery performance and life. To reveal the electrolyte distribution in the battery, the computation fluid dynamics (CFD) method was used to simulate a parallel flow field. A hydraulics experiment and a battery performance experiment were carried out to confirm the simulated results. The results show that the predicted information agreed well with the experimental results. The electrolyte has a concentrated distribution in the central region of the parallel flow field and the disturbed flow and then vortex flow areas mainly appear in the inlet and outlet regions. The higher flux of electrolyte is helpful to uniform the distributions and to reduce the impact of flow irregularity on the battery performance. The battery with the flow field generates a power density of 15.9 mW∙cm-2, and the coulombic, voltage and energy efficiency is up to 90.5%, 74.0% and 67.2% at a current density of 20 mA·cm-2.

scholarly journals Endwall Heat Transfer Measurements in a Transonic Turbine Cascade

1998 ◽  
Vol 120 (2) ◽  
pp. 305-313 ◽  
Author(s):  
P. W. Giel ◽  
D. R. Thurman ◽  
G. J. Van Fossen ◽  
S. A. Hippensteele ◽  
R. J. Boyle
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbine Blade ◽  
Large Scale ◽  
Model Verification ◽  
Quality Data ◽  
Free Stream Turbulence ◽  
Transonic Turbine ◽  
Mach Numbers ◽  
Inlet Conditions

Turbine blade endwall heat transfer measurements are presented for a range of Reynolds and Mach numbers. Data were obtained for Reynolds numbers based on inlet conditions of 0.5 and 1.0 × 106, for isentropic exit Mach numbers of 1.0 and 1.3, and for free-stream turbulence intensities of 0.25 and 7.0 percent. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The test article was a turbine rotor with 136 deg of turning and an axial chord of 12.7 cm. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for CFD code and model verification. The flow field in the cascade is highly three dimensional as a result of thick boundary layers at the test section inlet. Endwall heat transfer data were obtained using a steady-state liquid crystal technique.

Unsteady Rotor Heat Transfer in a Transonic Turbine Stage

2002 ◽  
Vol 124 (4) ◽  
pp. 614-622 ◽  
Author(s):  
F. Didier ◽  
R. De´nos ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Convective Heat Transfer Coefficient ◽  
Operating Conditions ◽  
Turbine Stage ◽  
Trailing Edge ◽  
Time Resolved ◽  
Number Distribution ◽  
Transonic Turbine

This experimental investigation reports the convective heat transfer coefficient around the rotor of a transonic turbine stage. Both time-resolved and time-averaged aspects are addressed. The measurements are performed around the rotor blade at 15, 50, and 85% span as well as on the rotor tip and the hub platform. Four operating conditions are tested covering two Reynolds numbers and three pressure ratios. The tests are performed in the compression tube turbine test rig CT3 of the von Karman Institute, allowing a correct simulation of the operating conditions encountered in modern aero-engines. The time-averaged Nusselt number distribution shows the strong dependence on both blade Mach number distribution and Reynolds number. The time-resolved heat transfer rate is mostly dictated by the vane trailing edge shock impingement on the rotor boundary layer. The shock passage corresponds to a sudden heat transfer increase. The effects are more pronounced in the leading edge region. The increase of the stage pressure ratio causes a stronger vane trailing edge shock and thus larger heat transfer fluctuations. The influence of the Reynolds number is hardly visible.

scholarly journals TIP LEAKAGE FLOW AND HEAT TRANSFER ON TURBINE STAGE TIP AND CASING: EFFECT OF UNSTEADY STATOR–ROTOR INTERACTIONS

2014 ◽  
Vol 11 (04) ◽  
pp. 1350058 ◽  
Author(s):  
MD HAMIDUR RAHMAN ◽  
SUNG IN KIM ◽  
IBRAHIM HASSAN
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Structures ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Tip Leakage ◽  
Flow And Heat Transfer ◽  
Blade Tip

Unsteady simulations were performed to investigate time dependent behaviors of the leakage flow structures and heat transfer on the rotor blade tip and casing in a single stage gas turbine engine. This paper mainly illustrates the unsteady nature of the leakage flow and heat transfer, particularly, that caused by the stator–rotor interactions. In order to obtain time-accurate results, the effects of varying the number of time steps, sub iterations, and the number of vane passing periods was firstly examined. The effect of tip clearance height and rotor speeds was also examined. The results showed periodic patterns of the tip leakage flow and heat transfer rate distribution for each vane passing. The relative position of the vane and vane trailing edge shock with respect to time alters the flow conditions in the rotor domain, and results in significant variations in the tip leakage flow structures and heat transfer rate distributions. It is observed that the trailing edge shock phenomenon results in a critical heat transfer region on the blade tip and casing. Consequently, the turbine blade tip and casing are subjected to large fluctuations of Nusselt number (about Nu = 2000 to 6000 and about Nu = 1000 to 10000, respectively) at a high frequency (coinciding with the rotor speed).

Application of a Multi-Block CFD Code to Investigate the Impact of Geometry Modeling on Centrifugal Compressor Flow Field Predictions

1996 ◽  
Author(s):  
Michael D. Hathaway ◽  
Jerry R. Wood
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Block Code ◽  
Tip Clearance ◽  
Trailing Edge ◽  
Flow Angle ◽  
Significant Difference ◽  
Single Block ◽  
The Impact ◽  
Actual Geometry

CFD codes capable of utilizing multi-block grids provide capability to analyze the complete geometry of centrifugal compressors including, among others, multiple splitter rows, tip clearance, blunt trailing edges, fillets, and slots between moving and stationary surfaces. Attendant with this increased capability is potentially increased grid setup time and more computational overhead — CPU time and memory requirements — with the resultant increase in “wall clock” time to obtain a solution. If the increase in “difficulty” of obtaining a solution significantly improves the solution from that obtained by modeling the features of the tip clearance flow or the typical bluntness of a centrifugal compressor’s trailing edge, then the additional burden is worthwhile. However, if the additional information obtained is of marginal use then modeling of certain features of the geometry may provide reasonable solutions for designers to make comparative choices when pursuing a new design. In this spirit a sequence of grids were generated to study the relative importance of modeling versus detailed gridding of the tip gap and blunt trailing edge regions of the NASA large low speed centrifugal compressor for which there is considerable detailed internal laser anemometry data available for comparison. The results indicate: 1) There is no significant difference in predicted tip clearance mass flow rate whether the tip gap is gridded or modeled. 2) Gridding rather than modeling the trailing edge results in better predictions of some flow details downstream of the impeller, but otherwise appears to offer no great benefits. 3) The pitchwise variation of absolute flow angle decreases rapidly up to 8% impeller radius ratio and much more slowly thereafter. Although some improvements in prediction of flow field details are realized as a result of analyzing the actual geometry there is no clear consensus that any of the grids investigated produced superior results in every case when compared to the measurements. However, if a multi-block code is available it should be used as it has the propensity for enabling better predictions than a single block code which requires modeling of certain geometry features. If a single block code must be used some guidance is offered for modeling those geometry features which can’t be directly gridded.

Investigation of Fan Rotor Interaction With Pressure Disturbance Produced by Downstream Pylon

2013 ◽  
Author(s):  
Tomonori Enoki ◽  
Hidekazu Kodama ◽  
Shinya Kusuda
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Numerical Results ◽  
Rotor Blades ◽  
Flow Structures ◽  
Coupled Analysis ◽  
Unsteady Forces ◽  
Rotor Stator Interaction ◽  
The Impact ◽  
Potential Pressure

This paper presents an investigation of fan rotor interaction with potential pressure disturbances produced by a downstream pylon. Three-dimensional unsteady viscous analyses are performed for two fan rotor-stator-pylon configurations with different axial gaps between the stator and the pylon, and compared with the experimental results. To clarify the impact of the rotor-pylon interaction on the potential pressure flow field, a numerical analysis for the configuration in which a fan rotor is removed is also performed and compared with the numerical results with fan rotor. Actuator disk analyses are also performed to interpret the flow structures observed in the experiments and the numerical results. It is found that a fan rotor-stator interaction also exists in the fan flow field, and this may impact on the upstream propagating potential flow that dominates the unsteady forces acting on the rotor blades. A coupled analysis between fan rotor and stator is essential to accurately predict the unsteady blade force.

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