Nestability sprejů typu effervescent, porovnání dvou měřících metod a vliv provozních podmínek

Unsteadiness in Effervescent Sprays, A Comparison of Two Measurement Methods and the Influence of Operation Conditions

conference paper

en

Two different methods were used to quantify the unsteadiness of effervescent atomizer generated spray in relation to operational conditions, two-phase flow pattern inside the atomizer mixing chamber and position in spray. The first method is based on measurement of pressure fluctuations in atomizer mixing chamber. This novel method was derived and applied here. Results show that decrease in GLR causes the nozzle to become more unsteady. Steady behaviour under dispersed and annular internal flow and tendency to unsteadiness when the flow shifts from frothy to bubbly can be seen on the two-phase flow maps. The second method, developed by Edvard and Marx, uses a comparison of measured interparticle arrival time distribution with theoretical distribution function modelled as inhomogeneous Poisson process. Not fully identical results with those in previous case in relation to the atomizer operation conditions show the spray unsteadiness development after discharge. Spray is more unsteady at its edge as well as at greater downstream distances, which is consistent with other authors findings.

Dvě různé metody byly použity pro měření nestabilit spreje generovaného tryskou typu effervescent a vyhodnocení vlivu provozních podmínek, režimu dvoufázovéhon toku uvnitř trysky a poloze ve spreji. První metoda je založena na měření tlakových pulzací uvnitř směšovací komory trysky. Tato nová metoda je zde popsána a aplikována. Výsledky ukazují rostoucí nestability spreje při poklesu GLR. Druhá metoda vyvinutá Edvardem a Marxem využívá statistické vyhodnocení intervalu mezi dopadem kapek spreje v měřícím objemu PDA analyzátoru. Ne zcela identické výsledky ukazují na vývin nestabilit po výtoku z trysky. Sprej je více nestabilní na hranách a ve větší vzdálenosti od trysky, což je ve shodě se zjištěním jiných autorů

Two different methods were used to quantify the unsteadiness of effervescent atomizer generated spray in relation to operational conditions, two-phase flow pattern inside the atomizer mixing chamber and position in spray. The first method is based on measurement of pressure fluctuations in atomizer mixing chamber. This novel method was derived and applied here. Results show that decrease in GLR causes the nozzle to become more unsteady. Steady behaviour under dispersed and annular internal flow and tendency to unsteadiness when the flow shifts from frothy to bubbly can be seen on the two-phase flow maps. The second method, developed by Edvard and Marx, uses a comparison of measured interparticle arrival time distribution with theoretical distribution function modelled as inhomogeneous Poisson process. Not fully identical results with those in previous case in relation to the atomizer operation conditions show the spray unsteadiness development after discharge. Spray is more unsteady at its edge as well as at greater downstream distances, which is consistent with other authors findings.

effervescent atomizer, spray quality, spray unsteadiness quantification, measurement method

2005

01.01.2005

International Centre for Heat and Mass Transfer

Ankara, Turkey

1-56700-223-4

Proceedings of International Symposium on Heat and Mass Transfer in Spray Systems

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