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Vizualization and optical measurements of two-phase flows for pressure-swirl atomizer
Janáčková, Lada ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
The present thesis deals with a study of both Simplex and SR versions of the original atomizer used in a combustion chamber of the small turbojet engine. For a better understanding of the spray formation process, a transparent model of both atomizers was manufactured in the scale of 10:1. The spray formation of a pressure swirl atomizer is a complex process of the two-phase flow. The internal and external flow was examined using Laser Doppler Anemometry and a high-speed imaging at inlet pressures of p = 0.5, 1.0 and 1.5 MPa with the use of kerosene and p-Cymene as working liquids. In terms of internal flow, the air core characteristic was performed, and the influence of different SFR values on the air core length and diameter was investigated. The velocity profiles of the internal flow together with their fluctuation components have been further clarified, considering Reynolds number and used liquid. Also, the simple numerical model was developed to estimate the internal flow field by particle tracking. In the case of external flow, the dependence of the inlet pressure on the liquid sheet breakup length and the spray cone angle was investigated.
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Experimental study of spray characteristics and functionality of small pressure-swirl atomizers
Malý, Milan ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
The present master thesis deals with an experimental study of spray characteristics from several small pressure-swirl atomizers used in a combustion chamber of turbojet aircraft engine. For decades, attention has been paid to improvement of their atomization characteristics but still there are possibilities which have not been examined yet. Investigations were carried out using various geometries of the individual elements of atomizer to find their effect on the spray. Measurements were made using a different number of entry ports (2, 3 and 4), various swirl chamber shapes (hemispheric; conical; curved convex and flat conical), and different spill-line orifice designs (axial and off-axis). Emphasis was placed on the assessment of spray stability wherein the fluctuating spray negatively affects the operating characteristics of the combustion chamber. Spray characteristics were probed using Phase Doppler analyser, spray circumferential homogeneity was rated by mechanical patternator and the liquid breakup was imaged by simple laser shadowgraph.
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Internal Flow of Spill-Return Pressure-Swirl Atomizers
Malý, Milan ; Honus,, Stanislav (oponent) ; Lozano, Antonio (oponent) ; Jedelský, Jan (vedoucí práce)
Pressure-swirl (PS) atomizers are used in many applications where a large surface area of droplets is needed, or a surface must be coated with a liquid, e.g. combustion, spray cooling or spray coating. Spray characteristics of PS atomizers are strongly linked to their internal flow. Spill-return (SR) atomizers enhance the construction of classic PS atomizers (Simplex) by addition of a passage through which the liquid can be spilled away. It allows regulation of an injection flow rate by spilling out a portion of the liquid from the swirl chamber, while the liquid pressure remains high. This ensures a good atomization quality over a wide flow rate range. The SR atomizers were rarely investigated and their internal flow has not been studied at all. In this thesis, both experimental and numerical approach is used to describe the internal flow pattern of several different SR atomizers. The results are then correlated with measured spray parameters. It shows that the addition of the spill passage strongly affects the internal flow even when the spill-line is closed. In some cases, the air-core does not form at all and destabilizes the discharged liquid, which results in the unstable spray. Off-axial SL orifices generate and stabilize the air-core, which leads to the regular formation of a liquid sheet and a high-quality spray. Nevertheless, some configurations changed the breakup nature of the liquid sheet and consequently the spray quality. Moreover, the turn-down ratio of the liquid supply rate and spray stability depend on the distance of the SL orifices from the swirl chamber centreline. Finally, an inviscid analysis of the internal flow, originally derived for the Simplex atomizers, was modified and applied to the SR atomizers. Using this approach, a theoretical prediction of the discharge coefficient and the air-core diameter was derived with spill-to-feed ratio (SFR) as the variable. Also, the empirical correlations, originally established for the Simplex type, were transformed to the SR atomizer. This thesis brings a new insight into the understanding of the internal flow of SR atomizers and its results can be directly used by engineers in the design process of the atomizer.
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Internal Flow of Spill-Return Pressure-Swirl Atomizers
Malý, Milan ; Honus,, Stanislav (oponent) ; Lozano, Antonio (oponent) ; Jedelský, Jan (vedoucí práce)
Pressure-swirl (PS) atomizers are used in many applications where a large surface area of droplets is needed, or a surface must be coated with a liquid, e.g. combustion, spray cooling or spray coating. Spray characteristics of PS atomizers are strongly linked to their internal flow. Spill-return (SR) atomizers enhance the construction of classic PS atomizers (Simplex) by addition of a passage through which the liquid can be spilled away. It allows regulation of an injection flow rate by spilling out a portion of the liquid from the swirl chamber, while the liquid pressure remains high. This ensures a good atomization quality over a wide flow rate range. The SR atomizers were rarely investigated and their internal flow has not been studied at all. In this thesis, both experimental and numerical approach is used to describe the internal flow pattern of several different SR atomizers. The results are then correlated with measured spray parameters. It shows that the addition of the spill passage strongly affects the internal flow even when the spill-line is closed. In some cases, the air-core does not form at all and destabilizes the discharged liquid, which results in the unstable spray. Off-axial SL orifices generate and stabilize the air-core, which leads to the regular formation of a liquid sheet and a high-quality spray. Nevertheless, some configurations changed the breakup nature of the liquid sheet and consequently the spray quality. Moreover, the turn-down ratio of the liquid supply rate and spray stability depend on the distance of the SL orifices from the swirl chamber centreline. Finally, an inviscid analysis of the internal flow, originally derived for the Simplex atomizers, was modified and applied to the SR atomizers. Using this approach, a theoretical prediction of the discharge coefficient and the air-core diameter was derived with spill-to-feed ratio (SFR) as the variable. Also, the empirical correlations, originally established for the Simplex type, were transformed to the SR atomizer. This thesis brings a new insight into the understanding of the internal flow of SR atomizers and its results can be directly used by engineers in the design process of the atomizer.
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Vizualization and optical measurements of two-phase flows for pressure-swirl atomizer
Janáčková, Lada ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
The present thesis deals with a study of both Simplex and SR versions of the original atomizer used in a combustion chamber of the small turbojet engine. For a better understanding of the spray formation process, a transparent model of both atomizers was manufactured in the scale of 10:1. The spray formation of a pressure swirl atomizer is a complex process of the two-phase flow. The internal and external flow was examined using Laser Doppler Anemometry and a high-speed imaging at inlet pressures of p = 0.5, 1.0 and 1.5 MPa with the use of kerosene and p-Cymene as working liquids. In terms of internal flow, the air core characteristic was performed, and the influence of different SFR values on the air core length and diameter was investigated. The velocity profiles of the internal flow together with their fluctuation components have been further clarified, considering Reynolds number and used liquid. Also, the simple numerical model was developed to estimate the internal flow field by particle tracking. In the case of external flow, the dependence of the inlet pressure on the liquid sheet breakup length and the spray cone angle was investigated.
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Experimental study of spray characteristics and functionality of small pressure-swirl atomizers
Malý, Milan ; Lízal, František (oponent) ; Jedelský, Jan (vedoucí práce)
The present master thesis deals with an experimental study of spray characteristics from several small pressure-swirl atomizers used in a combustion chamber of turbojet aircraft engine. For decades, attention has been paid to improvement of their atomization characteristics but still there are possibilities which have not been examined yet. Investigations were carried out using various geometries of the individual elements of atomizer to find their effect on the spray. Measurements were made using a different number of entry ports (2, 3 and 4), various swirl chamber shapes (hemispheric; conical; curved convex and flat conical), and different spill-line orifice designs (axial and off-axis). Emphasis was placed on the assessment of spray stability wherein the fluctuating spray negatively affects the operating characteristics of the combustion chamber. Spray characteristics were probed using Phase Doppler analyser, spray circumferential homogeneity was rated by mechanical patternator and the liquid breakup was imaged by simple laser shadowgraph.
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