The difference in film cooling effectiveness of three shaped holes is hereby explained by their vortical structures. Highlighted, in particular, are the competing effects of two pairs of vortices present in jets: the so-called kidney-shaped pair of vortices and a newly found anti-kidney pair. Three shaped holes investigated were referred to as TP2, TP3, and TP4. Except for the difference of how the hole area is increased, they are essentially the same. At the higher blowing ratio, the film cooling effectiveness of TP4 was found to be far superior to those of either TP2 and TP3. By flow visualization in water, the cause of these differences was investigated and found to be explainable on the basis of different vortical structures. In particular, for TP4 with a better film cooling effectiveness, the kidney- and anti-kidney pairs were found to cancel each other, leading to the improved jet attachment.

This paper deals with fundamental research on heat transfer characteristics inside a cooling configuration designed for an ultra-high temperature turbine nozzle. The cooling configuration adopted in this study integrates impingement cooling and pin cooling devices into one body, aiming at the enhancement of the effective area for the impingement cooling. A large-scaled test model of this cooling system is constructed to measure its internal heat transfer distribution, where a number of pins are sandwiched between an impingement plate and a target plate. The target plate are provided with several air discharging holes. A focus of this study is on how the heat transfer characteristics depend on the effect of stand-off distance: a distance between these two plates. Ratios of the stand-off distance to the impingement hole diameter varies from 0.75 to 2.00. A transient measurement technique using narrow-banded thermochromatic liquid crystal (TLC) is employed to determine the heat transfer characteristics of the model. Numerical investigations using a commercial CFD code are also executed and those results are compared with the experimental data. It is accordingly found that the numerical results almost match the measurements. It is also shown that the addition of pins to the conventional impingement cooling system can produce about 50% increase in the effective cooling area.

A fluid-solid conjugate solver has been newly developed and applied to an actual engine disk system. Most of the currently available conjugate solvers lack the special thermal modeling for turbomachinery disk system applications. In the present new code, these special models are implemented to expand the applicability of the conjugate method and to reduce the required computational resources. Most of the conjugate analysis work so far were limited to the axisymmetric framework. However, the actual disk system includes several non-axisymmetric components which inevitably affect the local heat transfer phenomena. This paper presents 3D conjugate analysis of a single stage high pressure turbine rotor-stator disk system to assess these three-dimensional effects. The predicted temperatures shows good agreement with measured data. The calculated results revealed the three-dimensional analysis is crucial to predict the correct heat transfer field which is especially important in transient situations.

Heat transfer characteristics of a three-pass serpentine flow passage with rotation is experimentally studied. The walls of the square flow passage are plated with thin stainless-steel foils through which electrical current is applied to generate heat. The local heat transfer performance on the four side walls of the three straight flow passages and two turning elbows are determined for both stationary and rotating cases. The through flow Reynolds, Rayleigh (centrifugal type) and Rotation numbers are varied. It is revealed that three-dimensional flow structures cause the heat transfer rate at the bends to be substantially higher than at the straight flow passages. This mechanism is revealed by means of a flow visualization experiment for non-rotating case. Along the first straight flow passage, the heat transfer rate is increased on the trailing surface but is reduced on the leading surface, due to the action of secondary streams induced by the Coriolis force. At low Reynolds numbers, the local heat transfer performance is primarily a function of buoyancy-force. In the higher Reynolds number range, however, the circumferential average Nusselt number is only a weak function of the Rayleigh and Rotation numbers.

Detailed studies are conducted on film effectiveness of discrete cooling holes around the leading edge of a blunt body that is subjected to periodically incoming wakes as well as free-stream turbulence with various levels of intensity. The cooling holes have a configuration similar to that of typical turbine blades except for the spanwise inclination angle. Secondary air is heated so that the temperature difference between the mainstream and secondary air is about 20 K. In this case, the air density ratio of the mainstream and secondary air becomes less than unity, therefore the flow condition encountered in an actual aero-engine cannot be simulated in terms of the density ratio. A spoke-wheel type wake generator is used in this study. In addition, three types of turbulence grids are used to elevate the free-stream turbulence intensity. We adopt three blowing ratios of the secondary air to the mainstream. For each of the blowing ratios, wall temperatures around the surface of the test model are measured by thermocouples situated inside the model. The temperature is visualized using liquid crystals in order to obtain qualitative information of film effectiveness distribution. / Vol. 119, APRIL 1997Transactions of the ASME Copyright © 1997 by ASME Downloaded From: http://turbomachinery.asmedigitalcollection.asme.org/ on 05/13/2015 Terms of Use: http://asme.org/terms Subscripts oo, 2 = mainstream, secondary air 15, 40 = first row, second row