Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

Numerical Design and Study of a MEMS-Based Micro Turbine

2005 ◽  
Author(s):  
Tatsuo Onishi ◽  
Ste´phane Burguburu ◽  
Olivier Dessornes ◽  
Yves Ribaud
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Skin Friction ◽  
Large Scale ◽  
Low Reynolds Number ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Low Reynolds ◽  
Micro Turbine

A full three dimensional Navier-Stokes solver elsA developed by ONERA is used to design and study the aerothermodynamics of a MEMS-based micro turbine. This work is performed in the framework of micro turbomachinery project at ONERA. A few millimeter scale micro turbine is operated in a low Reynolds number regime (Re = 5,000∼50,000), which implies a more important influence of skin friction and heat transfer than the conventional large-scale gas turbine. The 2D geometry constraints due to the limitation of fabrication technology also distinguish the aerothermodynamic characteristics of a micro turbine from that of conventional turbomachinery. Thus, for the foundation of aerothermodynamic design of micro turbomachinery, understanding of low Reynolds number effects on the performance is required and then the design of the turbine geometry can be optimized. In this study, aero-thermodynamic effects at low Reynolds number and different stator/rotor configurations are examined with a prescribed wall temperature. Losses due to heat transfer to walls and skin friction are estimated and their effects on the operating performance are discussed. Power delivery to turbine blades is checked and found satisfactory to give the objective design value of more than 100W. The effects of turbine exhaust geometry and the number of blades on turbine performance are also discussed.

Heat Transfer Performance of Internal Cooling Turbine Blades Using Cutted-Root Rib Design

2020 ◽  
Author(s):  
Cong-Truong Dinh ◽  
Tai-Duy Vu ◽  
Tan-Hung Dinh ◽  
Phi-Minh Nguyen
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Heat Transfer Performance ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Transfer Performance ◽  
External Cooling

Abstract In gas turbines, the turbine blades are always working in the highly temperature overhead the permissible metal temperatures. To safe operation, the turbine blades are needed to cool. Many researchs in turbine cooling technology can be categorized as internal and external cooling. This paper presents an investigation of cutted-root rib design, where a part of rib was truncated below to create an extra-passage in the root rib applied in the internal cooling turbine blades of jet engine using three-dimensional Reynolds-averaged Navier-Stokes with the SST model. The object of this investigation is to reduce the vortex occurring near the rib for improving the performance of heat transfer, such as the Nusselt number and thermal performance factor. To investigate the heat transfer performance and fluid flow characteristics of internal cooling turbine blades, a parametric study of the cutted-root rib was performed using various geometric parameters related to the height and shapes of the extra-passage. The cutted-root rib geometry is designed in ANSYS DesignModeler, and then meshed by using ICEM-CFD, analysed and post-processed using Ansys-CFX. The numerical results showed that all heat transfer parameter with the cutted-root rib design was greater than the original case without cutted-root rib.

Optimized Chaotic Heat Exchanger Configurations for Process Industry: A Numerical Study

2013 ◽  
Author(s):  
Akram Ghanem ◽  
Thierry Lemenand ◽  
Dominique Della Valle ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Process Intensification ◽  
Point Of View ◽  
Square Duct ◽  
Square Channel ◽  
Duct Geometry

A numerical investigation of chaotic laminar flow and heat transfer in isothermal-wall square-channel configurations is presented. The computations, based on a finite-volume method with the SIMPLEC algorithm, are conducted in terms of Péclet numbers ranging from 7 to 7×105. The geometries, based on the split-and-recombine (SAR) principle, are first proposed for micromixing purposes, and are then optimized and scaled up to three-dimensional minichannels with 3-mm sides that are capable of handling industrial fluid manipulation processes. The aim is to assess the feasibility of this mass- and heat-transfer technique for out-of-laboratory commercial applications and to compare different configurations from a process intensification point of view. The effects of the geometry on heat transfer and flow characteristics are examined. Results show that the flux recombination phenomenon mimicking the baker’s transform in the SAR-1 and SAR-2 configurations produces chaotic structures and promotes mass transfer. This phenomenon also accounts for higher convective heat transfer exemplified by increased values of the Nusselt number compared to the chaotic continuous-flow configuration and the baseline plain square-duct geometry. Energy expenditures are explored and the overall heat transfer enhancement factor for equal pumping power is calculated. The SAR-2 configuration reveals superior heat-transfer characteristics, enhancing the global gain by up to 17-fold over the plain duct heat exchanger.

Numerical Study on Supersonic Combustor with an Allotype Cavity

2014 ◽  
Vol 694 ◽  
pp. 187-192
Author(s):  
Jin Xiang Wu ◽  
Jian Sun ◽  
Xiang Gou ◽  
Lian Sheng Liu
Keyword(s):  
Alternative Model ◽  
Numerical Study ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Experimental Result ◽  
Navier Stokes ◽  
Cold Flow ◽  
Hypersonic Inlet ◽  
Good Agreement

The three-dimensional coupled explicit Reynolds Averaged Navier–Stokes (RANS) equations and the two equation shear-stress transport k-w (SST k-w) model has been employed to numerically simulate the cold flow field in a special-shaped cavity-based supersonic combustor. In a cross-section shaped rectangular, hypersonic inlet with airflow at Mach 2.0 chamber, shock structures and flow characteristics of a herringbone-shaped boss and a herringbone-shaped cavity models were discussed, respectively. The results indicate: Firstly, according to the similarities of bevel-cutting shock characteristics between the boss case and the cavity case, the boss structure can serve as an ideal alternative model for shear-layer. Secondly, the eddies within cavity are composed of herringbone-spanwise vortexes, columnar vortices in the front and main-spanwise vortexes in the rear, featuring tilting, twisting and stretching. Thirdly, the simulated bottom-flow of cavity is in good agreement with experimental result, while the reverse flow-entrainment resulting from herringbone geometry and pressure gradient. However, the herringbone-shaped cavity has a better performance in fuel-mixing.

scholarly journals Calculation of Convective Heat Transfer in Square-Sectioned Gas Turbine Blade Cooling Channels

1998 ◽  
Author(s):  
Arash Saidi ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Cross Sections ◽  
Turbine Blades ◽  
Solution Procedure ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Turbine Blade Cooling ◽  
Cooling Channels ◽  
Energy Equations

Internal cooling channels are commonly used to reduce the thermal loads on the gas turbine blades to improve overall efficiency. In this study a numerical investigation has been carried out to provide a validated and consistent method to deal with the prediction of the fluid flow and the heat transfer of such channels with square cross sections. The rotation modified Navier-Stokes and energy equations together with a low-Re number version of the k-ε turbulence model are solved with appropriate boundary conditions. The solution procedure is based on a numerical method using a collocated grid, and the pressure-velocity coupling is handled by the SIMPLEC algorithm. The computations are performed with the assumption of fully developed periodic conditions. The calculations are carried out for smooth ducts with and without rotation and effects of rotation on the heat transfer are described. Similar numerical calculations have carried out for channels with rib-roughened walls. The obtained results are compared with available experimental data and empirical correlations for the heat transfer rate and the friction factor. Some details of the flow and heat transfer fields are also presented.

Potential Flow Field Generated by Downstream Moving Bars and Propagated on a Turbine Blade at Low Reynolds Number

2011 ◽  
Author(s):  
Ve´ronique Penin ◽  
Pascale Kulisa ◽  
Franc¸ois Bario
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Numerical Study ◽  
Three Dimensional ◽  
Potential Effect ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Wake Interaction ◽  
Rotor Stator Interaction ◽  
The Stability

During the last few decades, the size and weight of turbo-machinery have been continuously reduced. However, by decreasing the distance between rows, rotor-stator interaction is strengthened. Two interactions now have the same magnitude: wake interaction and potential effect. Studying this effect is essential to understand rotor-stator interactions. Indeed, this phenomenon influences the whole flow, including the boundary layer of the upstream and downstream blades, ergo the stability of the flow and the efficiency of the machine. A large scale turbine cascade followed by a specially designed rotating cylinder system is used. Synchronised velocity LDA measurements on the vane profile show the flow and boundary layer behavior due to the moving bars. To help the general understanding and to corroborate our experimental results, numerical investigations are carried out with an unsteady three dimensional Navier-Stokes code. Moreover, the numerical study informs about the potential disturbance to the whole flow of the cascade.

Numerical Study of Turbulent Flow and Convective Heat Transfer Characteristics in Helical Rectangular Ducts

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Yunfei Xing ◽  
Fengquan Zhong ◽  
Xinyu Zhang
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Axial Direction ◽  
Outer Wall ◽  
Centrifugal Effect

Three-dimensional turbulent forced convective heat transfer and its flow characteristics in helical rectangular ducts are simulated using SST k–ω turbulence model. The velocity field and temperature field at different axial locations along the axial direction are analyzed for different inlet Reynolds numbers, different curvatures, and torsions. The causes of heat transfer differences between the inner and outer wall of the helical rectangular ducts are discussed as well as the differences between helical and straight duct. A secondary flow is generated due to the centrifugal effect between the inner and outer walls. For the present study, the flow and thermal field become periodic after the first turn. It is found that Reynolds number can enhance the overall heat transfer. Instead, torsion and curvature change the overall heat transfer slightly. But the aspect ratio of the rectangular cross section can significantly affect heat transfer coefficient.

Numerical study of transonic cavity flows using large-eddy and detached-eddy simulation

2007 ◽  
Vol 111 (1117) ◽  
pp. 153-164 ◽  
Author(s):  
P. Nayyar ◽  
G. N. Barakos ◽  
K. J. Badcock
Keyword(s):  
Energy Content ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
Promising Alternative ◽  
Eddy Simulation ◽  
Massively Separated Flows ◽  
Large Eddy

Numerical analysis of the flow in weapon bays modelled as open rectangular cavities of length-to-depth (L/D) ratio of 5 and width-to-depth (W/D) ratio of 1 with doors-on and doors-off is presented. Flow conditions correspond to Mach and Reynolds numbers (based on cavity length) of 0·85 and 6·783m respectively. Results from unsteady Reynolds-averaged Navier-Stokes (URANS), large-eddy simulation (LES) and detached-eddy simulation (DES) are compared with the simulation methods demonstrating the best prediction of this complex flow. It was found that URANS was not able to predict the change of flow characteristics between the doors-on and doors-off configurations. In addition, the energy content of the cavity flow modes was much better resolved with DES and LES. Further, the DES was found to be quite capable for this problem giving accurate results (within 3dB of) experiments and appears to be a promising alternative to LES for modelling massively separated flows.

Steady and Unsteady Modeling for Heat Transfer Predictions of High Pressure Turbine Blade Internal Cooling

2012 ◽  
Author(s):  
Rémy Fransen ◽  
Nicolas Gourdain ◽  
Laurent Y. M. Gicquel
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Cooling System ◽  
Transfer Problem ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Wall Region ◽  
Internal Cooling ◽  
Computational Domain ◽  
Complex Flow

This work focuses on numerical simulations of flows in blade internal cooling system. Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS) approaches are compared in a typical blade cooling related problem. The case is a straight rib-roughened channel with high blockage ratio, computed and compared for both a periodic and full spatial domains. The configuration was measured at the Von Karman Institute (VKI) using Particle Image Velocimetry (PIV) in near gas turbine operating conditions. Results show that RANS models used fail to predict the full evolution of the flow within the channels where massive separation and large scale unsteady features are evidenced. In contrast LES succeeds in reproducing these complex flow motions and both mean and fluctuating components are clearly improved in the channels and in the near wall region. Periodic computations are gauged against the spatial computational domain and results on the heat transfer problem are addressed.

A Numerical Study on the Influence of Grooves on Heat Transfer Performance of Wet Clutch

2012 ◽  
Vol 249-250 ◽  
pp. 517-522 ◽  
Author(s):  
Yu Long Lei ◽  
Jie Tao Wen ◽  
Xing Zhong Li ◽  
Cheng Yang
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Three Dimensional ◽  
Friction Material ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Linear Distribution ◽  
Exchange Performance ◽  
Wet Clutch ◽  
Oil Flow

In order to evaluate the efficacy of grooves on cooling performance of wet clutch, a numerical analysis based on the computational fluid dynamics (CFD) code FLUENT is presented in this study. This analysis is based on the numerical solution of the three-dimensional Navier-Stokes equation, coupled with the energy equation in the flow and the heat conduction equations in the friction material and the core disk. The turbulence characteristics were predicted using RNGk-ε model. The flow field and temperature distributions in radial grooves are obtained. It is shown that radial grooves possess the highest heat exchange performance at the entrance and is not linear distribution in the radial direction and cooling oil flow has a little effect on the highest temperature of friction plate. With the developed analysis method, it is possible to easily and quickly investigate the heat transfer behaviour of wet cluth with groove patterns.

Sign in / Sign up

Export Citation Format

Share Document