Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
D. Bohn ◽  
R. Krewinkel ◽  
A. Wolff
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Gas Turbines ◽  
Cooling System ◽  
Numerical Study ◽  
Internal Cooling ◽  
Maximum Entropy Production ◽  
Rotating Cavity

The flow field and heat transfer in the internal cooling system of gas turbines can be modeled using rotating-disk systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the maximum entropy production (MEP) principle as a possible means of simplifying numerical computations for these complex flows since this would enable us to use stationary numerical calculations to predict the flow field. Simply said, this theory is based on the heat flux out of the cavity. In this numerical study, the computed Nusselt numbers on the disk walls inside an open rotating cavity with a Rayleigh number of approximately 4.97 × 108. This is representative of the lower values encountered in the flow inside rotating cavities. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximized, or, conversely, the system is unstable when the heat transfer is minimized. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.

Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle

2010 ◽  
Author(s):  
D. Bohn ◽  
R. Krewinkel ◽  
A. Wolff
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Gas Turbines ◽  
Cooling System ◽  
Numerical Study ◽  
Internal Cooling ◽  
Maximum Entropy Production ◽  
Nusselt Numbers ◽  
Rotating Cavity

The flow field and heat transfer in the internal cooling system of gas turbines can be modelled using rotating-disc systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the Maximum Entropy Production (MEP) Principle as a possible means of simplifying numerical computations for these complex flows. This theory is based on the heat flux out of the cavity. In this numerical study, the Nusselt numbers on the disc walls inside an open rotating cavity with a Rayleigh number of approximately 4.97×108 are evaluated with regard to the computed Nusselt numbers on the disc walls. These can be considered to be representative of the flow inside the cavity. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximised, or, conversely, the system is unstable when the heat transfer is minimised. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.

Effect of Rotation on a Gas Turbine Blade Internal Cooling System: Numerical Investigation

2016 ◽  
Author(s):  
E. Burberi ◽  
D. Massini ◽  
L. Cocchi ◽  
L. Mazzei ◽  
A. Andreini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Numerical Investigation ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Cooling System ◽  
Leading Edge ◽  
Internal Cooling

Increasing turbine inlet temperature is one of the main strategies used to accomplish the demands of increased performance of modern gas turbines. As a consequence, optimization of the cooling system is of paramount importance in gas turbine development. Leading edge represents a critical part of cooled nozzles and blades, given the presence of the hot gases stagnation point and the unfavourable geometry for cooling. This paper reports the results of a numerical investigation aimed at assessing the rotation effects on the heat transfer distribution in a realistic leading edge internal cooling system of a high pressure gas turbine blade. The numerical investigation was carried out in order to support and to allow an in-depth understanding of the results obtained in a parallel experimental campaign. The model is composed of a trapezoidal feeding channel which provides air to the cold bridge system by means of three large racetrack-shaped holes, generating coolant impingement on the internal concave leading edge surface, whereas four big fins assure the jets confinement. Air is then extracted through 4 rows of 6 holes reproducing the external cooling system composed of shower-head and film cooling holes. Experiments were performed in static and rotating conditions replicating the typical range of jet Reynolds number (Rej) from 10000 to 40000 and Rotation number (Roj) up to 0.05, for three crossflow cases representative of the working condition that can be found at blade tip, midspan and hub, respectively. Experimental results in terms of flow field measurements on several internal planes and heat transfer coefficient on the LE internal surface have been performed on two analogous experimental campaigns at University of Udine and University of Florence respectively. Hybrid RANS-LES models were used for the simulations, such as Scale Adaptive Simulation (SAS) and Detached Eddy Simulation (DES), given their ability to resolve the complex flow field associated with jet impingement. Numerical flow field results are reported in terms of both jet velocity profiles and 2D vector plots on symmetry and transversal internal planes, while the heat transfer coefficient distributions are presented as detailed 2D maps together with radial and tangential averaged Nusselt number profiles. A fairly good agreement with experimental measurements is observed, which represent a validation of the adopted computational model. As a consequence, the computed aerodynamic and thermal fields also allow an in-depth interpretation of the experimental results.

ICAS-GT: A European Collaborative Research Programme on Internal Cooling Air Systems for Gas Turbines

2002 ◽  
Author(s):  
Peter D. Smout ◽  
John W. Chew ◽  
Peter R. N. Childs
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Research Programme ◽  
Cavity Flow ◽  
Internal Cooling ◽  
Manufacturing Companies ◽  
Flow And Heat Transfer ◽  
Rotating Cavity ◽  
Internal Fluid Flow ◽  
Cooling Air

The Internal Cooling Air Systems for Gas Turbines (ICAS-GT) research programme, sponsored by the European Commission, ran from January 1998 to December 2000, and was undertaken by a consortium of ten gas turbine manufacturing companies and four universities. Research was concentrated in five discrete but related areas of the air system including turbine rim seals, rotating cavity flow and heat transfer, and turbine pre-swirl system effectiveness. In each case, experiments were conducted to extend the database of pressure, temperature, flow and heat transfer measurements to engine representative non-dimensional conditions. The data was used to develop correlations, and to validate CFD and FE calculation methods, for internal fluid flow and heat transfer. This paper summarises the outcome of the project by presenting a sample of experimental results from each technical work package. Examples of the associated CFD calculations are included to illustrate the progress made in developing validated tools for predicting rotating cavity flow and heat transfer over an engine representative range of flow conditions.

scholarly journals Effect of Rotation on a Gas Turbine Blade Internal Cooling System: Experimental Investigation

2016 ◽  
Author(s):  
Daniele Massini ◽  
Emanuele Burberi ◽  
Carlo Carcasci ◽  
Lorenzo Cocchi ◽  
Bruno Facchini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Cross Flow ◽  
Leading Edge ◽  
Impinging Jets ◽  
Internal Cooling ◽  
Transfer Pattern

A detailed aerothermal characterization of an advanced leading edge cooling system has been performed by means of experimental measurements. Heat transfer coefficient distribution has been evaluated exploiting a steady-state technique using Thermocromic Liquid Crystals (TLC), while flow field has been investigated by means of Particle Image Velocimetry (PIV). The geometry key features are the multiple impinging jets and the four rows of coolant extraction holes, which mass flow rate distribution is representative of real engine working conditions. Tests have been performed in both static and rotating conditions, replicating a typical range of jet Reynolds number (Rej), from 10000 to 40000, and Rotation number (Roj) up to 0.05. Different cross-flow conditions (CR) have been used to simulate the three main blade regions (i.e. tip, mid and hub). The aerothermal field turned out to be rather complex, but a good agreement between heat transfer coefficient and flow field measurement has been found. In particular, jet bending strongly depends on crossflow intensity, while rotation has a weak effect on both jet velocity core and area-averaged Nusselt number. Rotational effects increase for the lower cross-flow tests. Heat transfer pattern shape has been found to be substantially Reynolds-independent.

Heat Transfer and Pressure Drop Measurements in a Rib Roughened Leading Edge Cooling Channel

2009 ◽  
Author(s):  
Norbert Domaschke ◽  
Jens von Wolfersdorf ◽  
Klaus Semmler
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Cooling System ◽  
Leading Edge ◽  
Suction Side ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Number Range ◽  
Ribbed Channel

In order to enhance convective heat transfer in internal cooling channels, ribs are often used to manipulate the flow field and to benefit from their effect on thermal performance. This paper presents results from an experimental investigation into pressure loss and heat transfer in a smooth and a ribbed leading edge channel of a gas turbine blade internal cooling system. To model the cross section of a realistic leading edge cooling channel both the suction side and the leading edge of the blade profile are designed as curved walls with constant radii. The pressure side as well as the web is approximated by planar walls. For the ribbed channel, 45°-ribs related to the flow direction are placed on the pressure and the suction side with the normalized rib height e/dh = 0.10. Experiments have been carried out for the smooth and the ribbed channel. The flow rate was varied to cover a Reynolds number range from 20,000 to 50,000. The heat transfer has been determined using the transient liquid crystal method. Additional numerical simulations using the SST turbulence model were carried out to analyze the flow field in the channel. The computations were used for further interpretation of the experimental investigations, especially to determine the temperature field and velocity field and therefore the bulk temperature within the test section.

Effects of Boot-Shaped Rib On Heat Transfer Characteristics of Internal Cooling Turbine Blades

2020 ◽  
Author(s):  
Ky-Quang Pham ◽  
Quang-Hai Nguyen ◽  
Tai-Duy Vu ◽  
Cong-Truong Dinh
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Cooling System ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Wall Friction ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Toe Angle

Abstract Gas turbine engine has been widely applied to many heavy industries, such as marine propulsion and aerospace fields. Increasing turbine inlet temperature is one of the major ways to improve the thermal efficiency of gas turbines. Internal cooling for gas turbine cooling system is one of the most commonly used approaches to reduce the temperature of blades by casting various kinds of ribs in serpentine passages to enhance the heat transfer between the coolant and hot surface of gas turbine blades. This paper presents an investigation of boot-shaped rib design to increase the heat transfer performances in the internal cooling turbine blades for gas turbine engines. By varying the design parameter configuration, the airflow is taken with higher momentum, and the minor vortex being at the front rib is relatively removed. The object of this investigation is increasing the reattachment airflow to wall and reducing the vortex occurring near the rib for improving the performances of heat transfer using three-dimensional Reynolds-averaged Navier-Stokes with the SST model. A parametric study of the boot-shaped rib design was performed using various geometric parameters related to the heel-angle, toe-angle, slope-height and rib-width to find their effect on the Nusselt number, temperature on the ribbed wall, friction factor ratio of the channel and thermal performance factor. The numerical results showed that the heat transfer performances are significantly increased with the heel-angle, toe-angle, slope-height, while that remained relatively constant with the rib-width.

Prediction of the Influence of Upstream Wake Passing on Downstream Blade Row External Heat Transfer Coefficient: A New Physically-Based Method

2010 ◽  
Author(s):  
K. S. Chana ◽  
B. R. Haller
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Cooling System ◽  
Guide Vane ◽  
External Heat ◽  
Test Facility ◽  
Internal Cooling ◽  
External Heat Transfer

For gas turbines, accurate prediction of the external heat transfer coefficient on the high pressure (HP) turbine rotor blades is of immense importance, as this component is critical and operates at material limits. Furthermore the external heat load is the governing boundary condition for the design of the internal cooling system of the blade. There is a continuous drive to increase the turbine entry temperature to increase the cycle efficiency, whilst developing blade cooling systems with higher efficiency (i.e. using less cooling air). A new systematic procedure has been developed and validated to predict the external heat transfer to a blade surface. The procedure allows for the unsteady effects caused by the passing of upstream nozzle guide vane (NGV) wakes. The early part of the suction surface was shown to have a pessimistic prediction of external heat transfer coefficient which resulted in unnecessary over-cooling of the blade in this region. The heat transfer aspect is found from the well-known TEXSTAN differential boundary layer method, developed by Mike Crawford at Texas University from the original approach of Spalding & Patankar. The method is validated against the MT1 turbine tested in the QinetiQ Turbine Test Facility. Predictions and comparisons have also been carried out on the VKI turbine stage. The level of agreement with the test data is shown to be good.

scholarly journals Effect of Rotation on a Gas Turbine Blade Internal Cooling System: Experimental Investigation

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Daniele Massini ◽  
Emanuele Burberi ◽  
Carlo Carcasci ◽  
Lorenzo Cocchi ◽  
Bruno Facchini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Leading Edge ◽  
Impinging Jets ◽  
Internal Cooling ◽  
Coefficient Distribution ◽  
Transfer Pattern

A detailed aerothermal characterization of an advanced leading edge (LE) cooling system has been performed by means of experimental measurements. Heat transfer coefficient distribution has been evaluated exploiting a steady-state technique using thermochromic liquid crystals (TLCs), while flow field has been investigated by means of particle image velocimetry (PIV). The geometry key features are the multiple impinging jets and the four rows of coolant extraction holes, and their mass flow rate distribution is representative of real engine working conditions. Tests have been performed in both static and rotating conditions, replicating a typical range of jet Reynolds number (Rej), from 10,000 to 40,000, and rotation number (Roj) up to 0.05. Different crossflow conditions (CR) have been used to simulate the three main blade regions (i.e., tip, mid, and hub). The aerothermal field turned out to be rather complex, but a good agreement between heat transfer coefficient and flow field measurement has been found. In particular, jet bending strongly depends on crossflow intensity, while rotation has a weak effect on both jet velocity core and area-averaged Nusselt number. Rotational effects increase for the lower crossflow tests. Heat transfer pattern shape has been found to be substantially Reynolds independent.

Heat Transfer and Pressure Drop Measurements in a Rib Roughened Leading Edge Cooling Channel

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Norbert Domaschke ◽  
Jens von Wolfersdorf ◽  
Klaus Semmler
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Cooling System ◽  
Leading Edge ◽  
Suction Side ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Number Range ◽  
Ribbed Channel

In order to enhance convective heat transfer in internal cooling channels, ribs are often used to manipulate the flow field and to benefit from their effect on thermal performance. This paper presents results from an experimental investigation into pressure loss and heat transfer in a smooth and a ribbed leading edge channel of a gas turbine blade internal cooling system. To model the cross section of a realistic leading edge cooling channel both the suction side and the leading edge of the blade profile are designed as curved walls with constant radii. The pressure side as well as the web is approximated by planar walls. For the ribbed channel, 45 deg-ribs related to the flow direction are placed on the pressure and the suction side with the normalized rib height e/dh = 0.10. Experiments have been carried out for the smooth and the ribbed channel. The flow rate was varied to cover a Reynolds number range from 20,000 to 50,000. The heat transfer has been determined using the transient liquid crystal method. Additional numerical simulations using the SST turbulence model were carried out to analyze the flow field in the channel. The computations were used for further interpretation of the experimental investigations, especially to determine the temperature field and velocity field and therefore the bulk temperature within the test section.

scholarly journals Heat Transfer From Low Aspect Ratio Pin Fins

2007 ◽  
Author(s):  
Michael E. Lyall ◽  
Alan A. Thrift ◽  
Atul Kohli ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbines ◽  
Channel Height ◽  
Internal Cooling ◽  
Number Range ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Low Aspect Ratio ◽  
Pin Fins

The performance of many engineering devices from power electronics to gas turbines is limited by thermal management. Heat transfer augmentation in internal flows is commonly achieved through the use of pin fins, which increase both surface area and turbulence. The present research is focused on internal cooling of turbine airfoils using a single row of circular pin fins that is oriented perpendicular to the flow. Low aspect ratio pin fins were studied whereby the channel height to pin diameter was unity. A number of spanwise spacings were investigated for a Reynolds number range between 5000 to 30,000. Both pressure drop and spatially-resolved heat transfer measurements were taken. The heat transfer measurements were made on the endwall of the pin fin array using infrared thermography and on the pin surface using discrete thermocouples. The results show that the heat transfer augmentation relative to open channel flow is the highest for smallest spanwise spacings and lowest Reynolds numbers. The results also indicate that the pin fin heat transfer is higher than the endwall heat transfer.

Sign in / Sign up

Export Citation Format

Share Document