Reducing Bottlenecks in the CAD-to-Mesh-to-Solution Cycle Time to Allow CFD to Participate in Design

2000 ◽  
Vol 123 (3) ◽  
pp. 552-557 ◽  
Author(s):  
W. N. Dawes ◽  
P. C. Dhanasekaran ◽  
A. A. J. Demargne ◽  
W. P. Kellar ◽  
A. M. Savill
Keyword(s):  
Flow Field ◽  
Cycle Time ◽  
Cooling System ◽  
Flow Simulation ◽  
Point Of View ◽  
Internal Cooling ◽  
Blade Row

As CFD has matured to the point that it is capable of reliable and accurate flow simulation, attention is now firmly fixed on how best to deploy that CFD as part of a process to improve actual products. This “process” consists of capturing and controlling the geometry of a suitable portion of an aeroengine (e.g., a blade row, or an internal cooling system or a fan-plus-nacelle), building a mesh system, solving the flow and responding to an appropriately visualized flow field by changing or accepting the geometry. This paper looks at that process from the point of view of identifying any bottlenecks and argues that current research should be directed at the CAD-to-mesh-to-solution cycle time rather than, as has been traditional, just looking at the solver itself and in isolation. Work aimed at eliminating some of these bottlenecks is described, with a number of practical examples.

Reducing Bottlenecks in the CAD-to-Mesh-to-Solution Cycle Time to Allow CFD to Participate in Design

2000 ◽  
Author(s):  
W. N. Dawes ◽  
P. C. Dhanasekaran ◽  
A. A. J. Demargne ◽  
W. P. Kellar ◽  
A. M. Savill
Keyword(s):  
Flow Field ◽  
Cycle Time ◽  
Cooling System ◽  
Flow Simulation ◽  
Point Of View ◽  
Internal Cooling ◽  
Blade Row

As CFD has matured to the point that it is capable of reliable and accurate flow simulation, attention is now firmly fixed on how best to deploy that CFD as part of a process to improve actual products. This “process” consists of capturing and controlling the geometry of a suitable portion of an aeroengine (eg a blade row, or an internal cooling system or a fan-plus-nacelle), building a mesh system, solving the flow and responding to an appropriately visualized flow field by changing or accepting the geometry. This paper looks at that process from the point of view of identifying any bottlenecks and argues that current research should be directed at the CAD-to-mesh-to-solution cycle time rather than, as has been traditional, just looking at the solver itself and in isolation. Work aimed at eliminating some of these bottlenecks is described, with a number of practical examples.

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.

Application of Conjugate Heat Transfer for Cooling Optimization of a Turbine Airfoil

2009 ◽  
Author(s):  
Grzegorz Nowak ◽  
Włodzimierz Wro´blewski
Keyword(s):  
Heat Transfer ◽  
Conjugate Heat Transfer ◽  
Thermal Field ◽  
Cooling System ◽  
Solid Material ◽  
System Optimization ◽  
Point Of View ◽  
Internal Cooling ◽  
Cooling Channels ◽  
Cooling Air

This paper discusses the problem of airfoil cooling system optimization connected with Conjugate Heat Transfer (CHT) analysis for reliable thermal field prediction within a cooled component. Since the full CHT solution, which involves the main flow, blade material and the coolant flow domains is computationally expensive from the point of view of optimization process, it was decided to reduce the problem by fixing the boundary conditions at the blade surface and solving the task for the interior only (both solid material and coolant). Such assumption, on one hand, makes the problem computationally feasible, and on the other, provides more reliable thermal field prediction than it used to be with the empirical relationships. The analysis involves the optimization of location and size of internal cooling passages within an airfoil. Initially, cooling is provided with circular passages and heat is transported by convection. The task is approached in 3D configuration. Each passage is fed with cooling air of constant parameters at the inlet. In the present study the airfoil profile is taken as aerodynamically optimal. The optimization is done with an evolutionary algorithm within a 30 dimensional design space, composed of space coordinates and radii of cooling channels. The search is realized with a weighted single objective function, which consisted of three objectives formulated on the basis of the airfoil’s thermal field and coolant mass flow.

PIV-Measurement of Secondary Flow in a Rotating Two-Pass Cooling System With an Improved Sequencer Technique

2010 ◽  
Author(s):  
M. Elfert ◽  
M. Schroll ◽  
W. Fo¨rster
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Cooling System ◽  
Flow Direction ◽  
Flow Simulation ◽  
Rotational Flow ◽  
Complex Flow ◽  
Reference Length ◽  
Piv Measurement ◽  
Image Position

The flow field characteristics of a two-pass cooling system with an engine-similar lay-out have been investigated experimentally using the non-intrusive Particle Image Velocimetry (PIV). It consists of a trapezoidal inlet duct, a nearly rectangular outlet duct, and a sharp 180 degree turn. The system has been investigated with smooth and ribbed walls. Ribs are applied on two opposite walls in a symmetric orientation inclined with an angle of 45 degrees to the main flow direction. The applied rib lay-out is well-proved and optimized with respect to heat transfer improvement versus pressure drop penalty. The system rotates about an axis orthogonal to its centreline. The configuration was analyzed with the planar two-component PIV technique (2C PIV), which is capable of obtaining complete maps of the instantaneous as well as the averaged flow field even at high levels of turbulence, which are typically found in sharp turns, in ribbed ducts and, especially, in rotating ducts. In the past, slip between motor and channel rotation causes additional not negligible uncertainties during PIV measurements due to unstable image position. These were caused by the working principle of the standard programmable sequencer unit used in combination with unsteady variations of the rotation speed. Therefore, a new sequencer was developed using FPGA-based hardware and software components from National Instruments which revealed a significant increase of the stability of the image position. Furthermore, general enhancements of the operability of the PIV system were achieved. The presented investigations of the secondary flow were conducted in stationary and, with the new sequencer technique applied, in rotating mode. Especially in the bend region vortices with high local turbulence were found. The ribs also change the fluid motion as desired by generating additional vortices impinging the leading edge of the first pass. The flow is turbulent and isothermal, no buoyancy forces are active. The flow was investigated at Reynolds number of Re = 50,000, based on the reference length d (see Fig. 3). The rotation number is Ro = 0 (non-rotating) and 0.1. Engine relevant rotation numbers are in order of 0.1 and higher. A reconstruction of some test rig components, especially the model mounting, has become necessary to reach higher values of the rotational speed compared to previous investigations like in Elfert [2008]. This investigation is aimed to analyze the complex flow phenomena caused by the interaction of several vortices, generated by rotation, flow turning or inclined wall ribs. The flow maps obtained with PIV are of good quality and high spatial resolution and therefore provide a test case for the development and validation of numerical flow simulation tools with special regard to prediction of flow turbulence under rotational flow regime as typical for turbomachinery. Future work will include the investigation of buoyancy effects to the rotational flow. This implicates wall heating which result from the heater glass in order to provide transparent models.

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.

Thermodynamic Aspects of Designing the New Siemens High Pressure Steam Turbine With Overload Valve for Supercritical Applications

2006 ◽  
Author(s):  
Frank Deidewig ◽  
Michael Wechsung
Keyword(s):  
High Pressure ◽  
Mass Flow ◽  
Cooling System ◽  
Point Of View ◽  
Internal Cooling ◽  
High Pressure Turbine ◽  
Axial Thrust ◽  
High Efficient ◽  
Main Steam ◽  
The Impact

Huge coal fueled power plants in the 1000MWel class are requiring high efficient steam turbines which can handle supercritical steam conditions up to 300bar and 600°C. Besides these boundary conditions, the capability for stabilising the grid fluctuations is also one key requirement. Siemens is focussing on this topic by using the so-called overload valve(s), which enhance the maximum amount of main steam mass flow entering the high-pressure turbine by use of additional valve(s). Using this technique, a power increase in the range of up to 20% is theoretically achievable. Siemens PG has collected a lot of positive service experiences throughout the past decades with this technique, and therefore this principle is being well established in the field. The connection between the additional steam mass flow passing through the overload valve and the standard blading path is somewhat downstream from the first stage. These connecting points can be varied (for this current turbine design) — if necessary — between the third and fifth stage after the turbine inlet. From an economic point of view, the approach of extending the power range via overload valves is even better than throttling the whole machine during standard operating condition and opening the valves fully at certain peak load requirements. Historically based, Siemens designs and manufactures reaction stages, ‘reaction turbines’, which must be thrust compensated via a separate piston to equalize and reduce the overall axial thrust down to a small number. Increasing the main steam temperatures up to the previously mentioned levels makes the internal cooling device of this thrust equilibrium piston a major key point for the whole turbine. No external cooling pipe-work or special materials are required. In Figure 1, a longitudinal cross-section 3D-view of the newly designed high-pressure turbine is drawn. The outer casing — at the steam inlet regime — is cast steel of 10% chromium content with significantly reduced wall thickness, whereas the outer casing at the hp-exhaust is a 1% chromium steel. The thrust-balancing piston on the shaft can be identified on the right hand side near the steam inlet channel. As noted further on, the steam outlet channels are both connected to the lower part of the turbine, whereas the inlet chambers are located at 3 o’clock and 9 o’clock, respectively. The outer casing has no horizontal splitting line; the turbine is being built as a barrel-design. This paper deals with the described turbine regarding the major design criteria from the thermodynamic point of view. Based on several calculations, the following design topics were covered: • Developing a turbine-internal cooling system for the thrust equilibrium/balancing piston as well as for the inner and outer casing. • Evaluation of staged piston with new internal cooling system adjusted for the impact on heat rate. • Quantification of all related mass flows, temperatures and pressures. • Axial thrust calculation to determine the required diameters of the staged piston. • General remarks concerning efficiency behaviour of hp-turbines with different geometrical designs.

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.

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.

Convective Cooling Optimization of a Blade for a Supercritical Steam Turbine

2011 ◽  
Author(s):  
Grzegorz Nowak ◽  
Włodzimierz Wro´blewski ◽  
Iwona Nowak
Keyword(s):  
Conjugate Heat Transfer ◽  
Thermal Field ◽  
Cooling System ◽  
Solid Material ◽  
System Optimization ◽  
Point Of View ◽  
Search Problem ◽  
Internal Cooling ◽  
Empirical Relationships ◽  
Blade Cooling

This paper discusses the problem of blade cooling system optimization connected with Conjugate Heat Transfer (CHT) analysis for reliable thermal field prediction within a steam cooled component. Since the full CHT solution, which involves the main flow, blade material and the coolant flow domains is computationally expensive from the point of view of optimization process, it was decided to reduce the problem by fixing the boundary conditions at the blade surface and solving the task for the interior only (both solid material and coolant). Such assumption, on one hand, makes the problem computationally feasible, and on the other, provides more reliable thermal field prediction than it used to be with the empirical relationships. The analysis involves shape optimization of internal cooling passages within an airfoil. The cooling passages are modeled with a set of four Bezier splines joined together to compose a closed contour. Each passage is fed with cooling steam of constant parameters at the inlet. In the present study the airfoil profile is taken as aerodynamically optimal. The search problem is solved with evolutionary algorithm and the final configuration is to be found among the Pareto optimal cooling candidates.

scholarly journals Three-Dimensional Analysis of a Multistage Compressor Flow Field

1998 ◽  
Author(s):  
Wolfgang Elmendorf ◽  
Frank Mildner ◽  
Ralf Röper ◽  
Uwe Krüger ◽  
Michael Kluck
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Flow Simulation ◽  
Test Facility ◽  
Navier Stokes ◽  
Air Supply ◽  
Blade Row ◽  
Cooling Air

A 3D-Navier-Stokes solver was used to analyse the complete flow field of the 15-stage axial compressor of Siemens model V84.3A advanced gas turbine. The paper presents the flow simulation including modelling of rotor tip clearances and bleeds for turbine cooling air supply. All computations were performed for coupled blade rows to account for the time averaged impact of interaction effects arising from adjacent airfoil rows. The evaluation of such two-blade-row calculations allows the update of the inlet boundary conditions for the following downstream two-blade-row combination. Successive computations from inlet guide vanes to exit stator thus yield the flow field of the whole compressor. The main objective is the analysis of the numerical results. Special attention is given to the front stage, stage matching, endwall flow effects, tip leakage and the cooling air extractions. The comparison to experimental data of the full load gas turbine test facility generally shows a good agreement. The results demonstrate the reliability and power of a modern CFD tool to perform advanced design studies, geometry modifications and calibration of fast 2D-Codes more efficiently and less expensively than performing any physical experiments.

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