Heat Transfer in Rotating Serpentine Passages With Trips Skewed to the Flow

Abstract

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass, heat transfer model with both radially inward and outward flow. Trip strips. skewed at 45 degrees to the flow direction, were machined on the leading and trailing surfaces of the radial coolant passages. A n analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages:coolant-to-wall temperature ratio, rotation number. Reynolds number and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation and huoyancy. decreased to as low as 40 percenl of the value wthout rotation. However, the maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels previously obtained with the smooth wall model. It was concluded that (1) both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips. (2) the effects of rotation are markedly different depending upon the flow direction and (3) the heat transfer with skewed trip strips i s less sensitivity to buoyancy than the heat transfer in motleis with either smooth walls or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and peometry-specific tests will be required for accurate design information.

Effects of Centrifugal Buoyancy and Reynolds Number on Turbulent Heat Transfer in a Two‐Pass Angled‐RIB‐Roughened Channel with Sharp 180∘ Turns Investigated by Using Large Eddy Simulation

“…On the pressure surface (triangle symbols), the buoyancy effect on Nu area is larger than that on the suction surface (square symbols), and Nu area of the aiding contribution cases (solid lines) is larger than those of the opposing contribution cases (broken lines). This tendency is supported by the experimental results of the rib-roughened channel [14], Pressure surface (triangle) Figure 9: Buoyancy effect on area-averaged Nusselt number at developed region in straight passes (Averaging area was between 5th and 6th ribs from straight pass entrance. Open, filled, half-filled, and concentric symbols are for (Re * , Ro * , smooth/rib) = (3500, 2, smooth), (1000, 1, rib), (3000, 1, rib), and (4000, 2, rib), resp.…”

“…although the entrance condition for the first straight pass in [14] was not disturbed by the upstream sharp turn. The aiding contribution on the pressure surface for the increase of Gr m,q /Re m 2 differs depending on rib existence, Re * , and Ro * .…”

“…In the figure, the time-averaged temperature is also shown as the color contour on the isosurface of Q. The value of Q is calculated by (14) for incompressible fluids, and it is often used to identify vortices because the positive value of Q means that the vorticity exceeds the strain,…”

“…For the rotating condition, however, both the flow velocity and wall temperature measurements become very difficult because of the following two reasons: the high centrifugal force preventing the data acquisition system from normal operation and the difficulty in transferring data from the rotating system to the stationary system. Nevertheless, some researchers have performed experiments in the rotating condition by measuring the wall temperature distribution using thermocouples for the smooth [10][11][12] and rib-roughened [13][14][15] wall two-pass channels with the 180 • sharp turn. Liou et al [16] conducted the flow velocity measurement of a rotating two-pass smooth channel with the 180…”

Formation of vertex flow in the rotating channel and influence of operation factors on its intensity

“…Вагнер [7,4] и Б. Джонсон [3] провели экс-периментальные исследования влияния плавучести и силы Кориолиса на теплопередачу в многоходо-вом внутреннем охлаждающем канале с гладкими стенками, наклонными и нормальными ребрами. По-лученные результаты показали сильное влияние пла-вучести и силы Кориолиса на структуру потока и рас-пределение коэффициента теплопередачи.…”