The Role of Secondary Flows and Separation in Convective Heat Transfer in a Rotating Radial Vane Brake Disc

2021 ◽  
Author(s):  
Michael. D Atkins ◽  
F.W. Kienhofer ◽  
Tian Jian Lu ◽  
Se-Myong Chang ◽  
Tongbeum Kim
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Suction Side ◽  
Secondary Flows ◽  
Brake Disc ◽  
Rotating Speed ◽  
Flow Mixing ◽  
End Wall ◽  
First Time

Abstract This study presents, for the first time, distributions of local internal temperature and convective heat transfer in a rotating radial vane brake disc and explains mechanisms in conjunction with secondary flows and flow separation within its ventilated coolant passages. In particular, variations of radial, circumferential (vane-to-vane) and axial (inboard-to-outboard) heat transfer on internal end-wall surfaces, and their alteration due to varying number of radial vanes and rotating speed are experimentally detailed. It has been demonstrated that conventional ventilated radial brake discs where the air inflow is drawn from the inboard face are likely to suffer substantial axial variations of temperature and heat transfer between the inboard and outboard discs, which possibly exacerbates thermal distortion (i.e., coning). Further, for a typical number of vanes (i.e., 36 vanes) used on automobiles, internal thermal distributions are highly non-uniform. However, the thermal end-wall uniformity improves considerably as the number of vanes is increased to say 72 vanes. Specifically, as the number of vanes is increased, secondary flow mixing enhances overall convective heat transfer and improves thermal uniformity. In contrast, separation causes large end-wall thermal non-uniformities in radial and circumferential distributions between the pressure side and the suction side of radial vanes. This effect nonetheless also decreases as the number of vanes is increased.

Convective Heat Transfer in a Rotating Hollow Cylinder with an End Wall

2020 ◽  
Vol 46 (7) ◽  
pp. 703-706
Author(s):  
V. A. Arkhipov ◽  
O. V. Matvienko ◽  
A. S. Zhukov ◽  
N. N. Zolotorev
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Hollow Cylinder ◽  
Convective Heat ◽  
Rotating Hollow Cylinder ◽  
End Wall

Two-Dimensional Heat Transfer Distribution of a Rotating Ribbed Channel at Different Reynolds Numbers

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Ignacio Mayo ◽  
Tony Arts ◽  
Ahmed El-Habib ◽  
Benjamin Parres
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotation Number ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Flux Boundary Condition

The convective heat transfer distribution in a rib-roughened rotating internal cooling channel was measured for different rotation and Reynolds numbers, representative of engine operating conditions. The test section consisted of a channel of aspect ratio equal to 0.9 with one wall equipped with eight ribs perpendicular to the main flow direction. The pitch to rib height ratio was 10 and the rib blockage was 10%. The test rig was designed to provide a uniform heat flux boundary condition over the ribbed wall, minimizing the heat transfer losses and allowing temperature measurements at significant rotation rates. Steady-state liquid crystal thermography (LCT) was employed to quantify a detailed 2D distribution of the wall temperature, allowing the determination of the convective heat transfer coefficient along the area between the sixth and eighth rib. The channel and all the required instrumentation were mounted on a large rotating disk, providing the same spatial resolution and measurement accuracy as in a stationary rig. The assembly was able to rotate both in clockwise and counterclockwise directions, so that the investigated wall was acting either as leading or trailing side, respectively. The tested Reynolds number values (based on the hydraulic diameter of the channel) were 15,000, 20,000, 30,000, and 40,000. The maximum rotation number values were ranging between 0.12 (Re = 40,000) and 0.30 (Re = 15,000). Turbulence profiles and secondary flows modified by rotation have shown their impact not only on the average value of the heat transfer coefficient but also on its distribution. On the trailing side, the heat transfer distribution flattens as the rotation number increases, while its averaged value increases due to the turbulence enhancement and secondary flows induced by the rotation. On the leading side, the secondary flows counteract the turbulence reduction and the overall heat transfer coefficient exhibits a limited decrease. In the latter case, the secondary flows are responsible for high heat transfer gradients on the investigated area.

Experimental Investigation of Convective Heat Transfer of Supercritical Pressure Hydrocarbon Fuel in a Horizontal Section of a Rotating U-Duct

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Zelong Lu ◽  
Yinhai Zhu ◽  
Yuxuan Guo ◽  
Peixue Jiang
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotational Speed ◽  
Convective Heat Transfer Coefficient ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Secondary Flows ◽  
Horizontal Section ◽  
Static Conditions

Abstract The experimental and numerical investigations of the heat transfer of supercritical pressure n-decane flowing through a pipe at various rotational speeds, mass flow rates, heat fluxes, and pressures, are presented. This pipe is 2 mm in diameter, 200 mm in length, with a radius of 0.328 m, and is parallel to the rotating axis. The wall temperature was measured at four positions around the periphery of the pipe at each of the five selected cross section along the pipe's length. Maximum convective heat transfer was observed at the outer edge of the horizontal section, while its corresponding minimum was observed at the inner edge. The heat transfers at the two sides of the channel were observed to be similar. The density and pressure differences between the outer and inner edges increased at increasing rotating speeds. However, the temperature difference between the outer and inner edges decreased with increased rotational speed mainly because of the increase of secondary flows in the section. The section's average convective heat transfer coefficient increased with an increase in the rotational speed, and its value at 1000 rpm was approximately twice than that at static conditions. The phenomenon of oscillation was observed near the exit of the horizontal section, and was caused by the flow and considerable property changes near the pseudo critical temperature. A computational fluid dynamics (CFD) model was developed using the real gas thermal properties and was coupled with the heat transferred owing to fuel flow. The predicted fuel and wall temperatures were in good agreement with the experimental data. A new local Nusselt number correlation of the heat transfer of n-decane in a rotating horizontal section was proposed.

scholarly journals Конвективный теплообмен во вращающемся полом цилиндре с торцевой стенкой

2020 ◽  
Vol 46 (14) ◽  
pp. 29
Author(s):  
В.А. Архипов ◽  
О.В. Матвиенко ◽  
А.С. Жуков ◽  
Н.Н. Золоторёв
Keyword(s):  
Heat Transfer ◽  
Angular Velocity ◽  
Flow Field ◽  
Convective Heat Transfer ◽  
Hollow Cylinder ◽  
Convective Heat ◽  
Axis Of Symmetry ◽  
End Wall

The method and results of calculating the flow field and convective heat transfer in a hollow cylinder with end wall rotating around the axis of symmetry with varying angular velocity and height of the cylinder are presented

Study of the Convective Heat Transfer in a Rotating Coolant Channel

1989 ◽  
Vol 111 (1) ◽  
pp. 43-50 ◽  
Author(s):  
J. Guidez
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Test Section ◽  
Suction Side ◽  
Turbine Rotor ◽  
Internal Cavity ◽  
Transfer Coefficients ◽  
Orthogonal Axis ◽  
Friction Forces

An experimental and theoretical study of convective heat transfer in a rotating coolant channel was inspired by the potential application to cooled turbine rotor blades. The flow that circulates into the internal cavity of the blade is subjected to Coriolis and centrifugal forces, in addition to pressure and friction forces. In this study, the channel is a rectangular-sectioned duct that rotates around an orthogonal axis. The experimental rig is composed of a vacuum enclosure, which includes an electric furnace, and the test section, heated by radiative flux. The temperatures of the wall test section are measured with thermocouples and the infrared pyrometer technique still under development. The convective heat transfer coefficients are determined with transient or steady-state techniques. It is shown that Coriolis acceleration has a beneficial influence on mean heat transfer. Locally, along the pressure side, the transfer increases strongly and on the contrary along the suction side, it decreases slightly. These effects are analyzed theoretically with a Navier-Stokes three dimensional (with mixing length model of turbulence) and explained by the influence of Coriolis force, which induces a secondary flow and distorts the velocity and temperature profiles. Experimental and theoretical results are presented and discussed.

Effect of Incidence on Wall Heating Rates and Aerodynamics on a Film-Cooled Transonic Turbine Blade

1991 ◽  
Vol 113 (3) ◽  
pp. 493-501 ◽  
Author(s):  
C. Camci ◽  
T. Arts
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Convective Heat Transfer ◽  
Stagnation Point ◽  
Short Duration ◽  
Convective Heat ◽  
Film Cooling ◽  
Free Stream ◽  
Suction Side ◽  
Pressure Side

This study investigates the influence of incidence on convective heat transfer to highly curved surfaces of a film-cooled turbine rotor blade. A computational study of free-stream inviscid aerodynamics without cooling at various incidences is followed by well-documented measured heat transfer data sets. The heat transfer experiments are discussed for cases with and without film cooling, performed under realistic gas turbine flow conditions in the short-duration heat transfer facility of the von Karman Institute for Fluid Dynamics. The precise location of the stagnation point and the iso-Mach number contours in the passage for each incidence (−10, 0, 10, +15 deg) are presented for a nominal exit Mach number of 0.94. The free-stream mass flow rate was kept constant for each experiment at different incidence levels. Three rows of compound angled discrete cooling holes are located near the leading edge in a showerhead configuration. Two rows of staggered discrete cooling holes are located on the suction side and a single row of cooling holes is located on the pressure side. The short-duration measurements of quantitative wall heat fluxes on nearly isothermal blade surfaces both in the presence and absence of coolant ejection are presented. The study indicated that the change of the position of the stagnation point strongly altered the aerodynamic behavior and convective heat transfer to the blade in approximately the first 30 percent of both the pressure side and the suction side in the presence and absence of film cooling. The immediate vicinity of the stagnation point was not significantly affected by changing incidence without cooling. Transitional behavior both on the suction surface and on the pressure surface was significantly influenced by the changes in approaching flow direction. Flow separation associated with incidence variations was also observed. Extremely low levels of the convective heat transfer coefficients were experienced near the regions where small separation bubbles are located.

Effect of Incidence on Wall Heating Rates and Aerodynamics on a Film Cooled Transonic Turbine Blade

1990 ◽  
Author(s):  
Cengiz Camci ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Convective Heat Transfer ◽  
Stagnation Point ◽  
Short Duration ◽  
Convective Heat ◽  
Film Cooling ◽  
Free Stream ◽  
Suction Side ◽  
Pressure Side

This study investigates the influence of incidence on convective heat transfer to highly curved surfaces of a film cooled turbine rotor blade. A computational study of free stream inviscid aerodynamics without cooling at various incidences is followed by well documented measured heat transfer data sets. The heat transfer experiments are discussed for cases with and without film cooling, performed under realistic gas turbine flow conditions in the short duration heat transfer facility of the von Karman Institute for Fluid Dynamics. The precise location of the stagnation point and the iso-Mach number contours in the passage for each incidence (−10°, 0°, 10°, +10°) are presented for a nominal exit Mach number of 0.94. The free stream mass flow rate was kept constant for each experiment at different incidence levels. Three rows of compound angled discrete cooling holes are located near the leading edge in a shower-head configuration. Two rows of staggered discrete cooling holes are located on the suction side and a single row of cooling holes is located on the pressure side. The short duration measurements of quantitative wall heat fluxes on nearly isothermal blade surfaces both in the presence and absence of coolant ejection are presented. The study indicated that the change of the position of the stagnation point strongly altered the aerodynamic behaviour and convective heat transfer to the blade in approximately the first 30 % of both the pressure side and the suction side in the presence and absence of film cooling. The immediate vicinity of the stagnation point was not significantly affected by changing incidence without cooling. Transitional behaviour both on the suction surface and on the pressure surface was significantly influenced by the changes in approching flow direction. Flow separation associated with incidence variations was also observed. Extremely low levels of convective heat transfer coefficients were experienced near the regions where small separation bubbles are located.

Heat Transfer Enhancement and Turbulent Flow in a Rectangular Channel Using Perforated Ribs With Inclined Holes

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Jian Liu ◽  
Safeer Hussain ◽  
Wei Wang ◽  
Lei Wang ◽  
Gongnan Xie ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Cross Section ◽  
Convective Heat ◽  
Rectangular Cross Section ◽  
Rectangular Channel ◽  
Secondary Flows ◽  
Internal Cooling ◽  
Detached Eddy Simulation ◽  
Inclined Angle

In internal cooling passages in a turbine blade, rib structures are widely applied to augment convective heat transfer by the coolant passing through over the ribbed surfaces. This study concentrates on perforated 90 deg ribs with inclined holes in a cooling duct with rectangular cross section, aiming at improving the perforated holes with additional secondary flows caused by inclined hole arrangements. Two sets of perforated ribs are used in the experiments with the inclined angle of the holes changing from 0 deg to 45 deg and the cross section are, respectively, circular and square. Steady-state liquid crystal thermography (LCT) is applied to measure the ribbed surface temperature and obtain corresponding convective heat transfer coefficients (HTCs). Two turbulence models, i.e., the k–ω shear stress transportation (SST) model and the detached eddy simulation (DES) model, are used in the numerical studies to simulate the flow fields. All the inclined cases have slightly larger overall averaged Nusselt number (Nu) than with straight cases. The enhancement ratio is approximately 1.85–4.94%. The averaged Nu in the half portion against the inclined direction is enlarged for the inclined hole cases. The inclined hole cases usually have smaller averaged Nu in the half portion along the inclined direction. For the straight hole case and small inclined angle case, the penetrated flows mix with the mainstream flows at the perforated regions. When the inclined angle is larger, the penetrated flows are pushed to the inclined direction and mixing with the approaching flows occurs just at the side of the inclined direction.

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