Heat Transfer in Stepped Labyrinth Seals

1988 ◽  
Vol 110 (1) ◽  
pp. 63-69 ◽  
Author(s):  
S. Wittig ◽  
K. Jacobsen ◽  
U. Schelling ◽  
S. Kim
Keyword(s):  
Heat Transfer ◽  
Wall Friction ◽  
Leakage Flow ◽  
Test Rig ◽  
Transfer Coefficients ◽  
Labyrinth Seals ◽  
Finite Element Program ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Element Program

Leakage flow and heat transfer of scaled-up stepped labyrinth seals were investigated experimentally and numerically. The experiments were conducted in a test rig under steady conditions. For different geometries and pressure ratios a finite element program was used to determine the temperature distribution and subsequently the heat transfer coefficients. In verifying the experimental results, the flow field of the seals was calculated numerically by a finite difference program. Heat transfer coefficients were derived utilizing the well-known analogies between heat transfer and wall friction.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low Speed Cascade

2003 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the 2-D blade. The wind tunnel accommodates an 116° turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83 × 105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required free-stream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

scholarly journals Heat Transfer and Fluid Dynamics Measurements in the Expansion Space of a Stirling Cycle Engine

2006 ◽  
Author(s):  
Nan Jiang ◽  
Terrence W. Simon
Keyword(s):  
Heat Transfer ◽  
High Efficiency ◽  
Stirling Engine ◽  
Transfer Coefficients ◽  
Head Region ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Engine Design ◽  
Region Flow ◽  
Design Calculations

The heater (or acceptor) of a Stirling engine, where most of the thermal energy is accepted into the engine by heat transfer, is the hottest part of the engine. Almost as hot is the adjacent expansion space of the engine. In the expansion space, the flow is oscillatory, impinging on a two-dimensional concavely-curved surface. Knowing the heat transfer on the inside surface of the engine head is critical to the engine design for efficiency and reliability. However, the flow in this region is not well understood and support is required to develop the CFD codes needed to design modern Stirling engines of high efficiency and power output. The present project is to experimentally investigate the flow and heat transfer in the heater head region. Flow fields and heat transfer coefficients are measured to characterize the oscillatory flow as well as to supply experimental validation for the CFD Stirling engine design codes. Presented also is a discussion of how these results might be used for heater head and acceptor region design calculations.

Numerical Simulation of Flow and Heat Transfer Past a Turbine Blade With a Squealer-Tip

2002 ◽  
Author(s):  
Huitao Yang ◽  
Sumanta Acharya ◽  
Srinath V. Ekkad ◽  
Chander Prakash ◽  
Ron Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Stress ◽  
Pressure Ratio ◽  
Reynolds Stress Model ◽  
Leakage Flow ◽  
Stress Model ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Model Calculations ◽  
Flow And Heat Transfer

Numerical calculations are performed to simulate the tip leakage flow and heat transfer on the squealer (recessed) tip of GE-E3 turbine rotor blade. A squealer tip with a 3.77% recess of the blade span is considered in this study, and the results are compared with the predictions for a flat-tip blade. The calculations have been performed for an isothermal blade with an overall pressure ratio of 1.32, an inlet turbulence intensity of 6.1%, and for three different tip gap clearances of 1%, 1.5% and 2.5% of the blade span. These conditions correspond to the experiments reported by Azad et al. [1]. The calculations have been performed for three different turbulence models (the standard high Re k-ε model, the RNG k-ε and the Reynolds Stress Model) in order to assess the capability of the models in correctly predicting the blade heat transfer. The predictions show good agreement with the experimental data, with the Reynolds stress model calculations clearly providing the best results. Substantial reductions in the tip heat transfer and leakage flow is obtained with the squealer tip configuration. With the squealer tip, the heat transfer coefficients on the shroud and on the suction surface of the blade are also considerably reduced.

scholarly journals Heat flow and heat transfer coefficient during crystallization under the pressure

2018 ◽  
Vol 157 ◽  
pp. 02036
Author(s):  
Richard Pastirčák ◽  
Ján Ščury ◽  
Tomáš Fecura
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Solidification Process ◽  
Metal Mold ◽  
Transfer Coefficients ◽  
Microstructure Modeling ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Solidification Processes ◽  
Precise Prediction

Estimation of the heat flow at the metal-mold interface is necessary for accurate simulation of the solidification processes. For the numerical simulation, a precise prediction of boundary conditions is required to determine the temperature distribution during solidification, porosity nucleation, microstructure development, and residual stresses. Determination of the heat transfer coefficients at the metal-mold interface is a critical aspect for simulation of the solidification process and the microstructure modeling of the castings. For crystallization under the pressure and for thin-walled castings, HTC evaluation is important due to the very limited freezing time.

The Effect of Combustor-Turbine Interface Gap Leakage on the Endwall Heat Transfer for a Nozzle Guide Vane

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
S. P. Lynch ◽  
K. A. Thole
Keyword(s):  
Heat Transfer ◽  
Guide Vane ◽  
Flux Ratio ◽  
Slot Width ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Coverage Area ◽  
Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Nozzle Guide

To enable turbine components to withstand high combustion temperatures, they are cooled by air routed from the compressor, which can leak through gaps between components. These gaps vary in size from thermal expansions that take place. The leakage flow between the interface of the combustor and the turbine, in particular, interacts with the flowfield along the endwall. This study presents measurements of adiabatic cooling effectiveness and heat transfer coefficients on the endwall of a first vane, with the presence of leakage flow through a flush slot upstream of the vane. The effect of axial contraction of the slot width due to thermal expansion of the engine was tested for two blowing rates. Contracting the slot width, while maintaining the slot mass flow, resulted in a larger coolant coverage area and higher effectiveness values, as well as slightly lower heat transfer coefficients. Matching the momentum flux ratio of the leakage flow from the nominal and contracted slot widths lowered both cooling effectiveness and heat transfer coefficients for the contracted slot flow. Comparison of the coolant coverage pattern to the measured endwall shear stress topology indicated that the trajectory of the slot coolant was dictated by the complex endwall flow.

Effect of Blade Tip Geometry on Tip Flow and Heat Transfer for a Blade in a Low-Speed Cascade

2004 ◽  
Vol 126 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Vikrant Saxena ◽  
Hasan Nasir ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Wind Tunnel ◽  
Flow Direction ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Transfer Coefficients ◽  
Wake Effect ◽  
Low Speed ◽  
Heat Transfer Coefficients ◽  
Blade Tip

A comprehensive investigation of the effect of various tip sealing geometries is presented on the blade tip leakage flow and associated heat transfer of a scaled up HPT turbine blade in a low-speed wind tunnel facility. The linear cascade is made of four blades with the two corner blades acting as guides. The tip section of a HPT first stage rotor blade is used to fabricate the two-dimensional blade. The wind tunnel accommodates an 116 deg turn for the blade cascade. The mainstream Reynolds number based on the axial chord length at cascade exit is 4.83×105. The upstream wake effect is simulated with a spoked wheel wake generator placed upstream of the cascade. A turbulence grid placed even farther upstream generates the required freestream turbulence of 4.8%. The center blade has a tip clearance gap of 1.5625% with respect to the blade span. Static pressure measurements are obtained on the blade surface and the shroud. The effect of crosswise trip strips to reduce leakage flow and associated heat transfer is investigated with strips placed along the leakage flow direction, against the leakage flow and along the chord. Cylindrical pin fins and pitch variation of strips over the tip surface are also investigated. Detailed heat transfer measurements are obtained using a steady-state HSI-based liquid crystal technique. The effect of periodic unsteady wake effect is also investigated by varying the wake Strouhal number from 0. to 0.2, and to 0.4. Results show that the trip strips placed against the leakage flow produce the lowest heat transfer on the tips compared to all the other cases with a reduction between 10–15% compared to the plain tip. Results also show that the pitch of the strips has a small effect on the overall reduction. Cylindrical pins fins and strips along the leakage flow direction do not decrease the heat transfer coefficients and in some cases enhance the heat transfer coefficients by as much as 20%.

Heat Transfer and Film Cooling on a Contoured Blade Endwall With Platform Gap Leakage

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Stephen P. Lynch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Film Cooling ◽  
Vortical Flow ◽  
Leakage Flow ◽  
Transfer Coefficients ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Manufacturing Assembly

Turbine blade components in an engine are typically designed with gaps between parts due to manufacturing, assembly, and operational considerations. Coolant is provided to these gaps to limit the ingestion of hot combustion gases. The interaction of the gaps, their leakage flows, and the complex vortical flow at the endwall of a turbine blade can significantly impact endwall heat transfer coefficients and the effectiveness of the leakage flow in providing localized cooling. In particular, a platform gap through the passage, representing the mating interface between adjacent blades in a wheel, has been shown to have a significant effect. Other important turbine blade features present in the engine environment are nonaxisymmetric contouring of the endwall, and an upstream rim seal with a gaspath cavity, which can reduce and increase endwall vortical flow, respectively. To understand the platform gap leakage effect in this environment, measurements of endwall heat transfer, and film cooling effectiveness were performed in a scaled blade cascade with a nonaxisymmetric contour in the passage. A rim seal with a cavity, representing the overlap interface between a stator and rotor, was included upstream of the blades and a nominal purge flowrate of 0.75% of the mainstream was supplied to the rim seal. The results indicated that the endwall heat transfer coefficients increased as the platform gap net leakage increased from 0% to 0.6% of the mainstream flowrate, but net heat flux to the endwall was reduced due to high cooling effectiveness of the leakage flow.

The Effect of Entrance Configuration on Local Heat-transfer Coefficients in Subsonic Diffusers

1972 ◽  
Vol 94 (4) ◽  
pp. 355-359 ◽  
Author(s):  
E. O. Stoffel ◽  
J. R. Welty
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Subsonic Diffuser

The effects of square and reentrant entrances on flow regimes (no “appreciable” separation, large transitory stall, and fully developed two-dimensional stall) and local heat-transfer coefficients were determined with air flowing through a symmetrical, plane-wall, two-dimensional subsonic diffuser with one of the diverging walls heated and maintained isothermal. Flow and heat-transfer studies were made for the following ranges: 2θ = 0 to 45 deg, L/W = 6 to 18, and Rextut = 4 × 104 to 3 × 105. Results indicated that 2θ, L/W, and entrance configuration greatly affected the flow regime and heat transfer. Equations relating Um′ to Ut, Ur to Ut, and equations of the type Nu = C Pr0.6Rex0.8 are presented. For the configurations tested, heat-transfer rates were greater for reentrant than for square entrances.

Heat Transfer to Supercritical Water in Advanced Power Engineering Applications: An Industrial Scale Test Rig

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Gerrit A. Schatte ◽  
Andreas Kohlhepp ◽  
Tobias Gschnaidtner ◽  
Christoph Wieland ◽  
Hartmut Spliethoff
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Supercritical Water ◽  
Test Section ◽  
Power Plants ◽  
Thermal Power ◽  
Internal Diameter ◽  
Test Rig ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Heat transfer to supercritical water in heated tubes and channels is relevant for steam generators in conventional power plants and future concepts for supercritical nuclear and solar-thermal power plants. A new experimental facility, the high pressure evaporation rig, setup at the Institute for Energy Systems (Technische Universität München) aims to provide heat transfer data to fill the existing knowledge gaps at these conditions. The test rig consists of a closed-loop high pressure cycle, in which de-ionized water is fed to an instrumented test section heated by the application of direct electrical current. It is designed to withstand a maximum pressure of 380 bar at 580 °C in the test section. The maximum power rating of the system is 1 MW. The test section is a vertical tube (material: AISI A213/P91) with a 7000 mm heated length, a 15.7 mm internal diameter, and a wall thickness of 5.6 mm. It is equipped with 70 thermocouples distributed evenly along its length. It enables the determination of heat transfer coefficients in the supercritical region at various steady-state or transient conditions. In a first series of tests, experiments are conducted to investigate normal and deteriorated heat transfer (DHT) under vertical upward flow conditions. The newly generated data and literature data are used to evaluate different correlations available for modeling heat transfer coefficients at supercritical pressures.

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