Gases separation with turbionaires movements through Coanda Effect.

Balasoiu, Victor ; Ionescu, Dumitru ; Manea, Adriana Sida 等

1. INTRODUCTION

The centrifugation method through vortex consists of in the tangential entering of the gas mixture at one of the fixed cylinder heads, the mixture still revolving and moving after a helical trajectory. Over the action of centrifugal forces will take a richness of the easy component at the center and of the hard component at the periphery of the cylinder.

The vortex tube Ranque--Hilsch adverted through its particular possibility of the separation of one gas in a hot fraction and a cold one.

Afterwards was investigated the possibility of the using of Ranque--Hilsch tube as a gas mixtures separator.

Linderstrom--Lang showed that those divergent results through the variation of some constructive parameters, the length of the vortex tube and the diameter of the orifices, for which the separation is caused only by the centrifugation effect.

2. THE SYNTHESIS STUDY OF VORTEX TUBE

The rotation of the mixture was assured by a wicket gate with 24 tangential blades. The wicket gate is coupled to the cylindrical tube through a convergent nozzle, decreasing the turbulence of the rotational current.

Comparing the concentration curves evolution presented in (Linderstrom--Lang, 1971) and it can be seen that those are different, because, the generation of the two vortexes was different afresh the constructive and functional parameters are also different.

From the analysis of the theoretical and experimental papers over the vortex tube is concluded that it can not give good results because of the small tangential velocities (Ma [less than or equal to] 1).

The separation element presented in this paper, is composed from a wicket gate with multiple kerfs, positioned in the alimentation room, a radial contraction and one cylindrical vortex tube.

The wicket gate is composed of figured blades which stand tangentially on a circumference and between them are formed equal rectangular kerfs.

The achieving of the rotation is made through Coanda Effect.

[FIGURE 1 OMITTED]

The jets generated through Coanda Effect, are the essential elements of a wicket gate.

It was tried the elucidation of the constructive and functional parameters influence of a jet deflected on different surfaces configurations which could be the blades of a wicket gate.

The jets deflecting through Coanda Effect (Bradshaw, 1976), in the conditions imposed by the big turbulence degree is possible if the gas movement along the driving surface is stable and if the jet is maintained attached to the wall on large distances from constructive point of view.

The gases mixture, passing in the interior of the apparatus through the kerfs, through Coanda Effect of deflecting a jet, gets a rotational movement. In the wicket gate room is prescienced the contraction, for supplementary amplifying of the radius velocity of the gas when this moves to the center.

Therefore grows adequate the tangential velocity. The separation element was designed that it can be adapted for different running situations.

The vortex generation installation (Anton et al., 1990) is assigned for verifying the different types of separation elements, using for different experimentations the mixture [N.sub.2]-[O.sub.2] from atmosphere. The open circuit experimental installation has the advantage of the constructive simplicity. In this paper were experimented two separation elements: wicket gate with interior vortex and with exterior vortex without contraction and were realized the best air-dynamics performances, permitting the vortex generation with supersonic velocities until Ma [greater than or equal to] 1.2, adverse the ones known from the literature, where the velocity was subsonic.

The experiments consist in the testing with mixture [N.sub.2]--[O.sub.2] from air of two types of separation elements with and without contraction. Calling the technical of measurements specific to the experimental investigations laboratory, the results are synthetize in diagrams: the concentration difference [DELTA] n = f ([theta]) in function with the downstream flow and the total flow introduced in the separation element. In figure 1 were presented the comparative results, the best ones with this separation element and the ones obtained by (Linderstrom-Lang, 1971) and (Linderrstrom-Lang, 1964).

From those diagrams it is seen that the maximum value realized with the separation element presented in the paper is superior to the maximum value realized by Linderstrom-Lang ([DELTA]n = 0.04 %). It must be remarked that the flow fraction on the two branches has enough advantages for cascades (36 % on one branch and 64 % on the other).

3. CONCLUSIONS

It was developed a theoretical study and an experimental installation which evidenced that the jets deflecting through Coanda Effect is possible and that the gas movement along the driving surface is stable and the jet is maintained attached to the wall on reasonable distances from constructive point of view. The Coanda Effect apears and at pressure ratios which pass over the critical value, recording a current acceleration at supersonic velocities.

It was developed an experimental and theoretical study for establishing a method of generation through Coanda Effect of the supersonic vortexes and decreased turbulence for gases with appropriate molecular mass separations, using the mixture [N.sub.2]-[O.sub.2]. The rotational movement is realized and maintained through Coanda Effect of vortex generation.

The separation element with interior vortex and interior contraction and the separation element with exterior vortex realized the best air-dynamics performances, permitting the vortex generation with supersonic velocities until Ma [greater than or equal to] 1.2, as opposed to the ones known from the literature were the velocity is subsonic.

4. FUTURE WORK In our next experiments we will try to obtain the variations using data acquisition hardware and specialized softwares, improving in this way the precision of measurements.

[FIGURE 2 OMITTED]

5. ACKNOWLEDGEMENTS

The present work has been supported from the National University Research Council Grant CNCSIS--IDEI nr.35/ 2007, CNCSIS- IDEI 34/2007 and Grant CNMP SHATEMPNr 1467/21047/2007.

6. REFERENCES

Anton, I., Ionescu, D., Balasoiu, V., Calin, G.; (1990) Separation element through vortex tube of the binary gases mixtures 1, The Conf. of Hydraulic Machinery and Hydro dynamics, Vol. 1, Fluid Mechanics, Timisoara, nov. 1990. pp. 261-266

Anton, I., Ionescu, D., Balasoiu, V., Calin, G.; (1990) Separation element through vortex tube of the binary gases mixtures 2, The Conf. of Hydraulic Machinery and Hydro dynamics, Vol. 1, Fluid Mechanics, Timisoara, nov. 1990. pp. 267-272

Linderrstrom-Lang, C.U.; (1971). Studies on Transport of Mass and Energy in the Vortex Tube, Risoo Report, No 248 Linderrstrom-Lang, C.U.; (1964). Separation in the Ranque-Hilsch Vortex Tube, J. Heat Mass Transfer, No 7, pp. 1195-1201

Bradshaw, P.; (1976). Experimental fluid mechanics, Pergamon Press, Oxford, 1970