VELOCITY - TEMPERATURE CORRELATIONS IN RECIRCULATING FLAMES WITH AND WITHOUT SWIRL

Simultaneous measurements of temperature and velocity have been perfor med with digitally compensated thermocouples and a laser velocimeter i n swirling and nonswirling recirculating flames stabilized downstream of a baffle. The velocity measurements are used to obtain magnitude es timates of the mean pressure gradients from the conservation equations of momentum in order to analyze the interaction between force fields induced by these gradients and the large density fluctuations typical of practical flames. The results are analysed in terms of the effects of swirl on the rate of turbulent heat transfer in the Favre-averaged form. It is shown that for the two types of flames analyzed the radial heat flux follow conventional scalar velocity concepts, but the axial heat flux show large values in regions of negligible partial derivati ve ($) over bar T/partial derivative x. The evidence is that the inter action between gradients of mean pressure and density fluctuations are important in the conservation of the fluxes, with comparatively large contributions in the swirling flame. Swirl is also shown to induce la rge gradients of the radial mean velocity component, which may influen ce the conservation of the turbulent shear stress ($$) over tilde u''u ''.