Blade Trailing Edge Heat Transfer

1980 ◽  
Author(s):  
A. Brown ◽  
B. Mandjikas ◽  
J. M. Mudyiwa
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Internal Heat ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Trailing Edge ◽  
Pillar Diameter ◽  
Trailing Edges ◽  
Pillar Arrays ◽  
Internal Heat Transfer

In this article measurements of heat transfer, pressure loss, and friction factor inside simulated trailing edges of turbine blades are presented. The trailing edges considered are vented and the internal heat transfer surfaces are extended by means of staggered arrays of pillars interconnecting the blade pressure and suction surfaces. A number of pillar arrays and trailing edge configurations are considered, namely pillar pitch to diameter ratios nominally of 2, 3, and 4 and trailing edge included angles of 0, 10, 15, and 20 deg. The range of Reynolds numbers covered based on pillar diameter and maximum velocity through a row of pillars is from 104 to 2 × 105.

Heat Transfer in a Vane Trailing Edge Passage With Conical Pins and Pin-Turbulator Integrated Configurations

2014 ◽  
Author(s):  
J. Kruekels ◽  
S. Naik ◽  
A. Lerch ◽  
A. Sedlov
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Heat Transfer Coefficients ◽  
Trailing Edges ◽  
Converging Channel ◽  
Internal Heat Transfer

The trailing edge sections of gas turbine vanes and blades are generally subjected to extremely high heat loads due to the combined effects of high external accelerating Mach numbers and gas temperatures. In order to maintain the metal temperatures of these trailing edges to a level, which fulfills the mechanical integrity of the parts, highly efficient cooling of the trailing edges is required without increasing the coolant consumption, as the latter has a detrimental effect on the overall gas turbine performance. In this paper the characteristics of the heat transfer and pressure drop of two novel integrated pin bank configurations were investigated. These include a pin bank with conical pins and a pin bank consisting of cylindrical pins and intersecting broken turbulators. As baseline case, a pin bank with cylindrical pins was studied as well. All investigations were done in a converging channel in order to be consistent with the real part. The heat transfer and pressure drop of all the pin banks were investigated initially with the use of numerical predictions and subsequently in a scaled experimental wind tunnel. The experimental study was conducted for a range of operational Reynolds numbers. The TLC (thermochromic liquid crystal) method was used to measure the detailed heat transfer coefficients in scaled Perspex models representing the various pin bank configurations. Pressure taps were located at several positions within the test sections. Both local and average heat transfer coefficients and pressure loss coefficients were determined. The measured and predicted results showed that the local internal heat transfer coefficient increases in the flow direction. This was due to the flow acceleration in the converging channel. Furthermore, both the broken ribs and the conical pin banks resulted in higher heat transfer coefficients compared with the baseline cylindrical pins. The conical pins produced the highest average internal heat transfer coefficients in contrast to the pins with the broken ribs, though this was also associated with a higher pressure drop.

Novel Turbulators to Enhance Turbine Blade Internal Heat Transfer Rates

2015 ◽  
Author(s):  
Venkata Naga Ramakumar Bommisetty ◽  
Sridhar Murari ◽  
Jong S. Liu ◽  
Malak F. Malak
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Thermal Load ◽  
Turbine Blades ◽  
Internal Heat ◽  
Current Paper ◽  
Transfer Rates ◽  
Internal Heat Transfer

Turbine blades are driven by hot gases from the combustor. The heat transfer from the hot gases produces substantial thermal load and can affect the performance of the turbine blades. In previous designs, cavities inside the blades were created to pass the coolant. Such cooling designs helped to increase the thermal performance of the blades by taking away the turbine blades’ heat. The cooling effect was further enhanced by increasing the turbulence in the flow of coolant. To increase the turbulence in the cavities, various turbulator designs were proposed. However, most of the designs have also introduced wake area while increasing the turbulence. This reduces the heat exchange between the coolant and the blade. The current paper discusses new designs of tabulators for turbine blades that increase the heat transfer rates of the cooling surface by increasing the turbulence of the coolant flow while minimizing the wake area.

Experimental Study of Internal Heat Transfer Coefficients in a Rectangular, Ribbed Channel Using a Non-Invasive, Non-Destructive, Transient Inverse Method

2008 ◽  
Author(s):  
Peter Heidrich ◽  
Jens von Wolfersdorf ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Measurement Method ◽  
Inverse Method ◽  
Turbine Blades ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Non Invasive ◽  
Non Destructive ◽  
Internal Heat Transfer

This paper describes a non-invasive, non-destructive inverse measurement method that allows one to determine heat transfer coefficients in internal passages of real turbine blades experimentally. For this purpose, a test rig with a fast responding heater was designed to fulfill the requirement of a sudden increase in the air temperature within the internal cooling passages. The outer surface temperatures of the specimen were measured using an infrared camera. To suggest the spatial distribution of the internal heat transfer coefficients from the transient characteristics of the outside surface temperature the inverse heat transfer problem was solved. Differing from former studies which made a thin wall assumption, the conduction inside a finite wall was modelled. Based on a one-dimensional forward solution the best fitting optimization method, the Levenberg-Marquardt algorithm, was chosen. This was verified with artificial data including random noise with positive results. Experimental data were measured for a rectangular H/W = 1:4 aspect ratio channel made of stainless steel with parallel 90° and 45° ribs at Reynolds numbers from 25,000 to 80,000. Results of 90° ribs were compared with simultaneously acquired data using the transient liquid crystal technique. Furthermore the influence of Reynolds number on pitch averaged heat transfer results were evaluated for both rib configurations. These results based on infrared data were compared with earlier studies. It is concluded that the presented experimental measurement method using the transient inverse method could be used to quantitatively determine heat transfer coefficients in internal passages of real turbine blades.

An LES Insight Into Convective Mechanism of Heat Transfer in a Wall-Bounded Pin Matrix

2010 ◽  
Author(s):  
Giovanni Delibra ◽  
Domenico Borello ◽  
Kemal Hanjalic ◽  
Franco Rispoli
Keyword(s):  
Heat Transfer ◽  
Turbulent Transport ◽  
Turbine Blades ◽  
Maximum Velocity ◽  
Reynolds Numbers ◽  
Internal Cooling ◽  
Gas Turbine Blades ◽  
The Matrix ◽  
Staggered Arrangement ◽  
Set Up

We report on an LES (large-eddy-simulations) study of flow and heat transfer in a longitudinal periodic segment of a matrix of cylindrical rods in a staggered arrangement bounded by two parallel heated walls. The configuration replicates the set-up investigated experimentally by Ames et al. (ASME Turbo Expo, GT2007-27432) and mimics the situation encountered in internal cooling of gas-turbine blades. LES have been performed using the in-house finite-volume computational code T-FlowS. Considered are two Reynolds numbers, 10000 and 30000, based on the rod diameter and maximum velocity in the matrix. The unstructured grid contained around 5 and 15 million cells for the two Re numbers respectively. After validating the simulations with respect to the available experimental data, the paper discusses the characteristic vortex and plume structures, streamline and heatline patterns and their evolution along the pin matrix, around individual pins and at the pin-endwall junctions. It is concluded that the convection by organized vertical structures originated from vortex shedding govern the thermal field and play the key role in endwall heat transfer, exceeding by far the stochastic turbulent transport.

scholarly journals The Role of Vortex Shedding in the Trailing Edge Loss of Transonic Turbine Blades

2018 ◽  
Author(s):  
A. P. Melzer ◽  
G. Pullan
Keyword(s):  
Vortex Shedding ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Variable Density ◽  
Experimental Program ◽  
Rapid Testing ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Transonic Turbine

The loss of Square, Round, and Elliptical turbine trailing edge geometries, and the mechanisms responsible, is assessed using a two-part experimental program. In the first part, a single blade experiment, in a channel with contoured walls, allowed rapid testing of a range of trailing edge sizes and shapes. In the second part, turbine blade cascades with a sub-set of sizes of the trailing edge geometries tested in part one were evaluated in a closed-loop variable density facility, at exit Mach numbers from 0.40 to 0.97, and exit Reynolds numbers from 1.5 x105 to 2.5 x106. Throughout the test campaign, detailed instantaneous Schlieren images of the trailing edge flows have been obtained to identify the underlying unsteady mechanisms in the base region. The experiments reveal the importance of suppressing transonic vortex shedding, and quantify the influence of this mechanism on loss. The state and thickness of the blade boundary layers immediately upstream of the trailing edge are of critical importance in determining the onset of transonic vortex shedding. Elliptical trailing edge geometries have also been found to be effective at suppressing transonic vortex shedding. For trailing edges that exhibit transonic vortex shedding, a mechanism is identified whereby reflected shed shockwaves encourage or discourage vortex shedding depending on the phase with which the shocks return to the trailing edge, capable of modifying the loss generated.

scholarly journals The Role of Vortex Shedding in the Trailing Edge Loss of Transonic Turbine Blades

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
A. P. Melzer ◽  
G. Pullan
Keyword(s):  
Vortex Shedding ◽  
Turbine Blades ◽  
Reynolds Numbers ◽  
Variable Density ◽  
Experimental Program ◽  
Rapid Testing ◽  
Trailing Edge ◽  
Trailing Edges ◽  
Transonic Turbine

The loss of square, round, and elliptical turbine trailing edge geometries, and the mechanisms responsible, is assessed using a two-part experimental program. In the first part, a single blade experiment, in a channel with contoured walls, allowed rapid testing of a range of trailing edge sizes and shapes. In the second part, turbine blade cascades with a subset of sizes of the trailing edge geometries tested in part one were evaluated in a closed-loop variable density facility, at exit Mach numbers from 0.40 to 0.97, and exit Reynolds numbers from 1.5 × 105 to 2.5 × 106. Throughout the test campaign, detailed instantaneous Schlieren images of the trailing edge flows have been obtained to identify the underlying unsteady mechanisms in the base region. The experiments reveal the importance of suppressing transonic vortex shedding, and quantify the influence of this mechanism on loss. The state and thickness of the blade boundary layers immediately upstream of the trailing edge are of critical importance in determining the onset of transonic vortex shedding. Elliptical trailing edge geometries have also been found to be effective at suppressing transonic vortex shedding. For trailing edges that exhibit transonic vortex shedding, a mechanism is identified whereby reflected shed shockwaves encourage or discourage vortex shedding depending on the phase with which the shocks return to the trailing edge, capable of modifying the loss generated.

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