Large Thrust Bearing Modeling: Influence of Thermal Boundary Conditions and Runner Deformations on Results of TEHD Analysis

2011 ◽  
Author(s):  
Michal Wodtke ◽  
Michel Fillon ◽  
Andreas Schubert ◽  
Michal Wasilczuk
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Thrust Bearing ◽  
Measurement Data ◽  
Water Power ◽  
Thermal Boundary Conditions ◽  
Side Walls ◽  
Theoretical Results ◽  
Bearing System

In the paper, numerical TEHD results for one of the biggest water power plant Itaipu were compared to available measurement data. Numerical simulations were carried out with the use of bearing model for which the accuracy was previously confirmed with the measurements available for smaller bearings. Several cases were analyzed. The only differences between the cases are the applied boundary conditions. The influence of heat transfer coefficient assumed at bearing pad side walls and collar deformation on predicted bearing performance was determined. Some conclusions concerning large thrust bearing modeling were drawn on the basis of comparisons of the theoretical results to measurements for analyzed bearing system.

Experimental Evidence of Temperature Ratio Effect on Turbine Blade Tip Heat Transfer

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
H. Jiang ◽  
Q. Zhang ◽  
L. He ◽  
S. Lu ◽  
L. Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Experimental Evidence ◽  
Turbine Blade ◽  
Tip Clearance ◽  
Temperature Ratio ◽  
Thermal Boundary Conditions ◽  
Thermal Measurements

Determination of a scalable Nusselt number (based on “adiabatic heat transfer coefficient”) has been the primary objective of the most existing heat transfer experimental studies. Based on the assumption that the wall thermal boundary conditions do not affect the flow field, the thermal measurements were mostly carried out at near adiabatic condition without matching the engine realistic wall-to-gas temperature ratio (TR). Recent numerical studies raised a question on the validity of this conventional practice in some applications, especially for turbine blade. Due to the relatively low thermal inertia of the over-tip-leakage (OTL) flow within the thin clearance, the fluids' transport properties vary greatly with different wall thermal boundary conditions and the two-way coupling between OTL aerodynamics and heat transfer cannot be neglected. The issue could become more severe when the gas turbine manufacturers are making effort to achieve much tighter clearance. However, there has been no experimental evidence to back up these numerical findings. In this study, transient thermal measurements were conducted in a high-temperature linear cascade rig for a range of tip clearance ratio (G/S) (0.3%, 0.4%, 0.6%, and 1%). Surface temperature history was captured by infrared thermography at a range of wall-to-gas TRs. Heat transfer coefficient (HTC) distributions were obtained based on a conventional data processing technique. The profound influence of tip surface thermal boundary condition on heat transfer and OTL flow was revealed by the first-of-its-kind experimental data obtained in the present experimental study.

Improved Turbine Blade Lifetime Prediction

2015 ◽  
Author(s):  
Cristhian Maravilla Herrera ◽  
Sergiy Yepifanov ◽  
Igor Loboda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Heating Temperature ◽  
Model Development ◽  
Lifetime Prediction ◽  
Thermal Boundary Conditions ◽  
And Performance ◽  
The Heat Transfer Coefficient

Algorithms for predicting the remaining lifetime of an engine play an important role in gas turbine monitoring systems. This paper addresses the improvement of models to determine the thermal boundary conditions that are necessary to calculate engine lifetime in critical hot components. Two methods for model development are compared. The first method uses physics-based models. The second method formulates the models based on a similarity concept. The object of analysis is a cooled blade of a high-pressure turbine. Two unmeasured thermal boundary conditions are considered: the heating temperature and the heat transfer coefficient. Instrumental and truncation errors are estimated for each model and 10 faulty conditions are considered to take into account the existing engine-to-engine differences and performance deterioration. The blade temperature and the thermal stress at the critical points are calculated using the results obtained by the developed models as boundary conditions. The results of the comparison show that the physics-based models are more robust to power plant faults. The best models for the heating temperature and the heat transfer coefficient were chosen. It is shown that the accuracy of the heating temperature model is more important for reliable lifetime prediction.

The Concept of Adiabatic Heat Transfer Coefficient and its Application to Turbomachinery

2013 ◽  
Author(s):  
Reinaldo A. Gomes ◽  
Reinhard Niehuis
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Constant Wall Temperature ◽  
Heat Transfer Coefficients ◽  
Thermal Boundary Conditions ◽  
Critical Components

Typical turbomachinery flows are too complex to be predicted by analytical solutions alone. Therefore numerous correlations and test data are used in conjunction with numerical tools in order to design thermally critical components. This approach can be problematic because these correlations and data are not fully independent of the boundary conditions applied. The heat transfer coefficients obtained are not only dependent on the aerodynamics of the flow but also on the thermal boundary layer created along the surface. The adiabatic heat transfer coefficient is the only one which is independent of the thermal boundary conditions, as long as the energy equation can be considered linear with respect to the temperature. However, a proper prediction of the surface temperature cannot be obtained with the adiabatic heat transfer coefficient alone. This paper first reviews the concept of adiabatic heat transfer coefficient and its application to turbomachinery flows. Later, a concept is introduced to allow interchanging between different definitions of heat transfer coefficient and boundary conditions, i.e. constant heat flux or constant wall temperature. Finally, a typical configuration for measuring the adiabatic heat transfer coefficient on a turbine blade and the conversion to other definitions of heat transfer coefficient is presented and evaluated. It is shown that with the technique presented here even small deficiencies of some experiments can be compensated for.

Optically Based Rapid Heat Transfer Measurements in Complex Internal Flows

2007 ◽  
Vol 129 (12) ◽  
pp. 1655-1665 ◽  
Author(s):  
Charles W. Booten ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Laser Heating ◽  
Heat Conduction Problem ◽  
Reynolds Numbers ◽  
Inverse Heat Conduction Problem ◽  
Inverse Heat Conduction ◽  
Thermal Boundary Conditions

Abstract An optically based technique was developed that involves fabrication of a thin-walled plastic model with laser heating applied to a small section of the outer surface. The heat flux distribution applied to the model by the laser was measured first using a short-duration, transient experiment. The external temperature distribution was then recorded using infrared thermography with steady laser heating. The measured heat flux and temperature distributions were used as thermal boundary conditions in a finite-element code to solve an inverse heat conduction problem for the heat transfer coefficient on the internal passage wall. Hydrodynamically fully developed turbulent flow in a round tube was used as a test case for the development of the new optical method. The Reynolds numbers used were 30,000 and 60,000. This flow was chosen because accurate computational tools were available to calculate the internal heat transfer coefficient for a variety of thermal boundary conditions. In addition, this geometry simplified both the model fabrication and the implementation of a finite-element model for the inverse heat conduction problem. Heat transfer coefficient measurements agreed with numerical simulations and semi-analytical solutions within 1.5% and 8.5% for the low and high Reynolds numbers, respectively. Additional simulations suggest that the method can be accurate with thermal boundary conditions more complex than in these experiments.

Inverse Determination of Steady Heat Convection Coefficient Distributions

1998 ◽  
Vol 120 (2) ◽  
pp. 328-334 ◽  
Author(s):  
T. J. Martin ◽  
G. S. Dulikravich
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Boundary Conditions ◽  
Measurement Data ◽  
Cost Effective ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Simple Modification ◽  
Heat Transfer Coefficients ◽  
Thermal Boundary Conditions

An inverse Boundary Element Method (BEM) procedure has been used to determine unknown heat transfer coefficients on surfaces of arbitrarily shaped solids. The procedure is noniterative and cost effective, involving only a simple modification to any existing steady-state heat conduction BEM algorithm. Its main advantage is that this method does not require any knowledge of, or solution to, the fluid flow field. Thermal boundary conditions can be prescribed on only part of the boundary of the solid object, while the heat transfer coefficients on boundaries exposed to a moving fluid can be partially or entirely unknown. Over-specified boundary conditions or internal temperature measurements on other, more accessible boundaries are required in order to compensate for the unknown conditions. An ill-conditioned matrix results from the inverse BEM formulation, which must be properly inverted to obtain the solution to the ill-posed problem. Accuracy of numerical results has been demonstrated for several steady two-dimensional heat conduction problems including sensitivity of the algorithm to errors in the measurement data of surface temperatures and heat fluxes.

Alternative and Relevant Representation to Heat Transfer Coefficient for Modeling the Heat Transfer Between a Fluid and a Non-Isothermal Wall in Transient Regime

2010 ◽  
Author(s):  
Benjamin Remy ◽  
Alain Degiovanni
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Flat Plate ◽  
Temperature Difference ◽  
Interfacial Heat Transfer ◽  
Thermal Boundary Conditions

This paper deals with the relevant model that can be proposed for modeling the interfacial heat transfer between a fluid and a wall in the case of space and time varying thermal boundary conditions. Usually, for a constant and uniform heat transfer (unidirectional steady-state regime), the problem can be solved introducing a heat transfer coefficient h, uniform in space and constant in time that linearly links the surface heat flux and the temperature difference between the wall temperature Tw and an equivalent fluid temperature Tf. The problem we consider in this work concerns the heat transfer between a steady-state fluid flow and a wall submitted to a transient and non uniform thermal solicitations, as for instance a steady-state flow on a flat plate submitted to a transient and space reduced heat flux. We will show that the more interesting representation for describing the interfacial heat transfer is not to define as usually done a non-uniform and variable heat transfer coefficient h(x,t) because as it depends on the thermal boundary conditions, it is not really intrinsic. We propose an alternative approach, which consists in introducing a generalized impedance Z(ω,p) that links in space and time domain the heat flux and the temperature difference through a double convolution product instead of a scalar product. After the presentation of the general problem, the simple case of a stationary piston flow that can be solved analytically will be considered for validation both in thermal steady-state and transient regimes. To conclude and show the interest of our approach, a comparison between a global approach and a numerical simulation in a more complex and realistic case taking into account the thermal coupling with a flat plate will be presented.

Heat Transfer Contributions of Pins and Endwall in Pin-Fin Arrays: Effects of Thermal Boundary Condition Modeling

1999 ◽  
Vol 121 (2) ◽  
pp. 257-263 ◽  
Author(s):  
M. K. Chyu ◽  
Y. C. Hsing ◽  
T. I.-P. Shih ◽  
V. Natarajan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Thermal Boundary Conditions ◽  
The Individual ◽  
Pin Fin Arrays

Short pin-fin arrays are often used for cooling turbine airfoils, particularly near the trailing edge. An accurate heat transfer estimation from a pin-fin array should account for the total heat transfer over the entire wetted surface, which includes the pin surfaces and uncovered endwalls. One design question frequently raised is the actual magnitudes of heat transfer coefficients on both pins and endwalls. Results from earlier studies have led to different and often contradicting conclusions. This variation, in part, is caused by imperfect or unrealistic thermal boundary conditions prescribed in the individual test models. Either pins or endwalls, but generally not both, were heated in those previous studies. Using a mass transfer analogy based on the naphthalene sublimation technique, the present experiment is capable of revealing the individual heat transfer contributions from pins and endwalls with the entire wetted surface thermally active. The particular pin-fin geometry investigated, S/D = X/D = 2.5 and H/D = 1.0, is considered to be one of the optimal array arrangement for turbine airfoil cooling. Both inline and staggered arrays with the identical geometric parameters are studied for 5000 ≤ Re ≤ 25,000. The present results reveal that the general trends of the row-resolved heat transfer coefficients on either pins or endwalls are somewhat insensitive to the nature of thermal boundary conditions prescribed on the test surface. However, the actual magnitudes of heat transfer coefficients can be substantially different, due to variations in the flow bulk temperature. The present study also concludes that the pins have consistently 10 to 20 percent higher heat transfer coefficient than the endwalls. However, such a difference in heat transfer coefficient imposes very insignificant influence on the overall array-averaged heat transfer, since the wetted area of the uncovered endwalls is nearly four times greater than that of the pins.

scholarly journals Heat Transfer Contributions of Pins and Endwall in Pin-Fin Arrays: Effects of Thermal Boundary Condition Modeling

1998 ◽  
Author(s):  
M. K. Chyu ◽  
Y. C. Hsing ◽  
T. I.-P. Shih ◽  
V. Natarajan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients ◽  
Thermal Boundary Conditions ◽  
The Individual ◽  
Pin Fin Arrays

Short pin-fin arrays are often used for cooling turbine airfoils, particularly near the trailing edge. An accurate heat transfer estimation from a pin-fin array should account for the total heat transfer over the entire wetted surface which includes the pin surfaces and uncovered end walls. One design question frequently raised is the actual magnitudes of heat transfer coefficients on both pins and endwalls. Results from earlier studies have led to different and often contradicting conclusions. This variation, in part, is caused by imperfect or unrealistic thermal boundary conditions prescribed in the individual test models. Either pins or endwalls, but generally not both, were heated in those previous studies. Using a mass transfer analogy based on the naphthalene sublimation technique, the present experiment is capable of revealing the individual heat transfer contributions from pins and endwalls with the entire wetted surface thermally active. The particular pin-fin geometry investigated, S/D = X/D = 2.5 and H/D = 1.0, is considered to be one of the optimal array arrangement for turbine airfoil cooling. Both inline and staggered arrays with the identical geometric parameters are studied for 5,000 ≤ Re ≤ 25,000. The present results reveal that the general trends of the row-resolved heat transfer coefficients on either pins or endwalls are somewhat insensitive to the nature of thermal boundary conditions prescribed on the test surface. However, the actual magnitudes of heat transfer coefficients can be substantially different, due to variations in the flow bulk temperature. The present study also concludes that the pins have consistently 10 to 20% higher heat transfer coefficient than the endwalls. However, such a difference in heat transfer coefficient imposes very insignificant influence on the overall array-averaged heat transfer, since the wetted area of the uncovered endwalls is nearly four times greater than that of the pins.

Simulation and validation of air flow and heat transfer in an autoclave process for definition of thermal boundary conditions during curing of composite parts

2017 ◽  
Vol 52 (12) ◽  
pp. 1677-1687 ◽  
Author(s):  
Tobias Bohne ◽  
Tim Frerich ◽  
Jörg Jendrny ◽  
Jan-Patrick Jürgens ◽  
Vasily Ploshikhin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Boundary Conditions ◽  
Transfer Coefficient ◽  
Fluid Dynamic ◽  
Fluid Velocity ◽  
Computational Effort ◽  
Autoclave Process ◽  
Thermal Boundary Conditions ◽  
The Heat Transfer Coefficient

Aerospace carbon fibre-reinforced components are cured under high pressure (7 bar) and temperature in an autoclave. As in an industrial environment, the loading of an autoclave usually changes from cycle to cycle causing different thermal masses and airflow pattern which leads to an inhomogeneous temperature distribution inside the carbon fiber-reinforced plastic part. Finally, the overall process can be delayed and the part quality can be compromised. In this paper, the heat transfer in a small laboratory autoclave has been investigated using calorimeter measurements and a fluid dynamic model. A complex turbulent flow pattern with locally varying heat transfer coefficient has been observed. Especially, the pressure and the inlet fluid velocity have been identified as sensitive process parameters. Further finite element simulations with adjusted boundary conditions provide accurate results of the curing process inside of the components for selective process control. The heat transfer coefficient has been found to be almost stationary during the observed constant pressure autoclave process allowing a separated investigation of the heat transfer coefficient and the curing of the components. The presented method promises therefore a detailed observation of the autoclave process with reduced computational effort.

Sign in / Sign up

Export Citation Format

Share Document