Simultaneous measurements of time-resolved velocity and temperature have been obtained by laser-Doppler anemometry and numerically compensated fine-wire thermocouples in the near wake of a premixed flame stabilized on a disk baffle located on the axis, and at the exit, of a confining pipe. The diameter of the disk was 0.056 m, the diameter of the pipe was 0.080 m, the volumetric equivalence ratio with natural gas as the fuel was 0.79 and the Reynolds number, based on pipe diameter and upstream pipe bulk velocity of 9 m/s, was 46 800. The purpose of the measurements is to quantify the relative magnitudes of terms involving the mean pressure gradient and Reynolds stresses in the balance of turbulent kinetic energy and heat flux in a strongly sheared, high-Reynolds-number, reacting flow. The latter term has been associated with non-gradient diffusion in other flows. Source terms involving the mean pressure gradient are large in the conservation of turbulent heat flux but not in the conservation of Reynolds stress. The ‘thin-flame’ model of burning suggests that the sign and magnitude of the heat flux is closely related to the conditioned mean velocities. The mean axial velocity of the reactants is larger (by up to 0.27 of the reference velocity) than that of the products on the low-velocity side of the shear layer that surrounds the recirculation bubble but the reverse is true on the high-velocity side. These observations are related to the sign of the axial pressure gradient, which is associated with the streamline curvature, and the consequent preferential acceleration of the low-density products. Generally, the Reynolds stresses of the products are higher than those of the reactants and, in contrast to previously reported measurements, the contribution to the unconditioned stresses by the difference in the mean velocity between products and reactants, the so-called ‘intermittent’ contribution, is small. This is a consequence of the high Reynolds number of our flow.

The interaction of turbulence and pressure gradients in a baffle-stabilized premixed flame

In certain regions of turbine aerofoils, cooling system designers need to cool the blades with convection systems that provide high heat transfer coefficients. The present research has investigated a circular cooling passage with tangential injection suitable for a blade leading edge. The heat transfer coefficients are measured using the conventional transient heat transfer, liquid crystal technique. The results are compared to the data from steady state experiments performed by Hedlund et al. [1]. The cooling system performance is compared in detail to average data from earlier tangential injection experiments and to local heat transfer coefficient expected from a normal impingement system. The vortex flow field was also studied by numerical prediction and near-wall velocity measurements. The investigation of the flow structure has led to understanding of flow mechanisms responsible for the high heat transfer coefficient. The vortex flow field was also investigated using computational fluid dynamics and with hot wire anemometry. The latter near wall measurements were combined with the law of the wall and Colburn analogy to validate the flow and heat transfer measurements.© 2006 ASME

Measurement of Heat Transfer Coefficient Distributions and Flow Field in a Model of a Turbine Blade Cooling Passage With Tangential Injection

A comparative study of heat transfer characteristics of wall-bounded jets using different turbulence models

Transferts de chaleur et de quantité de mouvement dans les jets pariétaux plans turbulents

A numerical study of a plane wall jet with heat transfer

Extensive single-point turbulence measurements made in a heated wall jet on a convex wall, and in an equivalent plane flow, show that the turbulence structure and the transfer of heat and momentum are affected by wall curvature. In the curved wall jet the points of zero shear stress and zero streamwise heat flux are displaced further from the point of maximum velocity, the Stanton number for heat transfer from the surface is reduced more than the skin-friction coefficient, and temperature profiles in the inner layer depart from the flat-flow wall law. The shear stress, turbulent intensities and turbulent heat fluxes are reduced by stabilizing curvature in the inner layer and increased by destabilizing curvature in the outer flow. The largest changes occur in the triple products, which are nearly doubled by destabilizing curvature.

C. A. Verriopoulos

Papers

Turbulent flow with heat transfer in plane and curved wall jets