V. P. Lebedev

Effects of flow turbulence on film cooling efficiency

Abstract Results of experimental investigations on film cooling effectiveness in high-turbulent flow are represented in this paper. The turbulence intensity changed within the range Tu o = 0.2–15% and the injection parameter was 0.1 m m m > 1) the turbulence effect weakens. The experimental data generalization and its comparison with the results of the calculation carried out by asymptotic theory are given.

Effect of flow acceleration and initial turbulence level on velocity fluctuations

The effect of various levels of initial turbulence on the decay of the velocity fluctuations in convergent channels with different contraction ratios has been experimentally investigated. The results of the experiments indicate that the level of turbulence has a strong influence on the longitudinal velocity fluctuations and a weaker effect on the transverse fluctuations. The experimental data demonstrate the inapplicability of the rapid distortion theory and the need for that theory to take into account the energy dissipation, the integral scale and the degree of anisotropy.

Heat transfer in a wall jet at high turbulence of cocurrent stream

Abstract Heat transfer is studied at an extending of a wall jet in a cocurrent stream in wide variation range of injection parameter (m 1) and turbulence level of the stream (Tu0 = 0.2–20%) . A rise in turbulence at m 1 regime, turbulence level has no effect on heat transfer, so that the latter can be estimated according to relationships being valid for low-turbulent jet flows.

An experimental study of the flow stabilization in a channel with a swirled periphery jet

Abstract This paper represents results of experimental study on the coaxial flow mixing in channels with a swirled periphery jet. These experiments were carried out in the long cylindrical tubes and in the vortex chambers with a diaphragmed exit. The main attention was paid to the parameter distribution in the near-axial region of the flow depending on the entrance geometry and flow rate characteristics. The effects of the swirl angle of the periphery jet, a thickness of the edge between coaxial flows, and the concurrency parameter m=ρ s w s /ρ 0 w 0 on the flow stabilization within the field of centrifugal mass forces were analyzed. A character of stabilizing effect of the flows on the mixing processes was determined by a gas temperature change along the channel’s axis and turbulence intensity. Generalizing dependencies were obtained for a relative temperature at the axis both in the swirled and direct flows. Experimental results on the heat flow mixing in vortex chambers are shown here. There are some similarities for transfer processes in the vortex chambers and long tubes. The main difference is that the diaphragmed chamber and boundary layers at the edge walls considerably effect the mixing.

Heat transfer in a channel with a counter-current wall jet injection

Abstract In this work we present the results of an experimental investigation of heat transfer with a counter-current wall jet injection towards a main flow. In the experiments we studied heat transfer from a place of injection to the wall turn and downstream behind the place of injection. The investigation of an aerodynamic structure of a flow showed that the interaction of a jet with a counter-current flow resulted in the formation of a recirculation flow zone, and the heat transfer distribution had the same salient features, characteristic to separation flows. The formation of a new boundary layer behind the recirculation zone occurs under conditions of high-intensity external turbulence and the presence of a main flow velocity gradient. Consideration of these salient features leads to good agreement of the calculated and the experimental data on heat transfer. It has been shown that a velocity increase of the injected jet results in heat transfer increase, both in the area from the place of injection to the jet turn and downstream behind a place of counter injection. It has been established that heat transfer regulation within a broad range of parameters may be carried out by means of a jet injection.

The LDA study of flow gas-dynamics in a vortex chamber

Abstract The experimental data on the turbulent structure of swirling flow in vortex chamber with diaphragm are presented. The data were made with the help of LDA method. The evolution of turbulence intensity in the vortex chamber is shown. The influence of initial conditions of the swirling flow forming on the turbulent properties are considered.

MASS TRANSFER WITH GAS DESORPTION FROM THE SURFACE OF A LIQUID FILM IN THE PRESENCE OF A COCURRENT FLOW

Results of a thcoretical and experimental study of dynamics and mass transfer during desorption of a gas from a liquid film in the presence of a cocurrent air flow are presented. The calculation model is based on solving integral momentum and diffusion relations for the gaseous and liquid phascs. Both laminar and turbulent regimes of the film flow are analyzed. The experimental study of mass transfer was conducted for carbon dioxide desorption from a water film. Criterial relations for mass transfer in the gaseous and liquid phases are obtained. The experiments showed that the heat-transfer coefficients for the case under study are one order of magnitude grcater than those for the flow of a smooth film. Possible mechanisms of such an appreciable intensification of the liquid-film mass transfer in a cocurrent gas flow are discussed.

Mass exchange in gas desorption from finely dispersed liquid particles in a near-wall two-phase jet

This work deals with the experimental investigation of the mass exchange between finely dispersed liquid particles and a gas flow. We investigate mass transfer in the desorption process of a slightly water-soluble carbonic acid gas from the liquid particle surface at wide variations of the rate parameters for both gas and liquid phase. These data may be further used in the analysis of heat and mass transfer processes in near-wall two-phase flows.

Heat transfer in a wall jet propagating in a highly turbulent cocurrent flow

Heat transfer in a jet propagating in a cocurrent flow has been studied over wide ranges of the injection ratio (m=Us/U0<1 and m>1) and flow turbulence (Tu0=0.2–25%). It is shown experimentally that for m<1, a 1% increase in turbulence leads to a 1% increase in heat transfer, and the wall adiabatic temperature and the relative heat-transfer function should be taken into account in heat-transfer calculations. For m>1, the flow turbulence does not affect the heat transfer and the heat production can be calculated using the laws typical of jet flows.