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Numerical study of Coanda effect with swirl number and design parameters in Airblast nozzle
Milad Khaleghi Kasbi,Reza Alidoost Dafsari,Jupyong Kim,Jeekeun Lee 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Coanda effect consists of the tendency of an airflow jet to adhere to nearby solid boundaries. This common class of phenomena, which may be observed in both fluid and gas, is named the Coanda effect. In this paper, interest in the detailed behavior of Coanda effect in Airblast nozzle. The purpose is to examine the effect of various geometric factors and swirl number on the generation of Coanda effect in Airblast nozzle. It has been discovered that the formation wall-attached jet in an Airblast nozzle is controlled by both the Reynolds number and the swirl number.
On the Coanda formation and spray structure of a pre-filming airblast nozzle: an experimental study
Reza Alidoost Dafsari,Milad Khaleghi Kasbi,Jupyong Kim,Jeekeun Lee 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Pre-filming airblast nozzles are the most common fuel injectors in the combustion section of gas turbines in aviation applications. Owing to their multi-swirler structure, they can provide stable spray with fine droplets for ultimately enhanced combustion quality. However, their complex geometry requires sophisticated study and analysis to understand the physics of the flow. The geometry of swirlers controls the swirl strength of the flow issuing from each swirler and consequently, the formation of a swirling spray with regions of recirculation and various size vortices. Despite the essential nature of swirling motion, a higher swirl intensity can potentially lead to the formation of Coanda effect in which the spray flows radially. The formation of Coanda is of the most dangerous challenges in the combustor as it attributes to unstable spray and the occurrence of flashbacks. The geometry of the atomizer and injection condition can contribute to the formation of Coanda. In this study, 4 nozzles with various geometry with individual exit shapes and recess length were tested under various injection conditions to map a correlation for Coanda formation. The experimental approach used laser diagnostic techniques. The results show a great impact of swirl intensity, pressure drop, and air-to-liquid mass flow ratio (ALR) on the Coanda formation.
Reza Alidoost Dafsari,Milad Khaleghi Kasbi,Jupyong Kim,Jeekeun Lee 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The atomization characteristics of nozzles are affected by various parameters such as the internal geometry and the injection condition. Pre-filming airblast nozzles are of the most complicated geometries - wing to the existence of multiple swirlers - that makes them of prime interests of study in the aerodynamic and multiphase field. Despite numerous attempts to understand the physics of flow in this subject, the breakup structure of this atomizer type remains a challenge. The droplet size and the spray structure both governed by the inlet geometry and swirl intensity have major impacts on the combustion quality and stability. To investigate the effect of nozzle geometry on the spray spatial characteristics, 4 nozzles with various geometries were parametrically tested using laser diagnostic experimental methods, namely Phase Doppler Particle Anemometry (PDPA), Particle Image Velocimetry (PIV), and Mie scattering Technique. The results showed a great impact of the internal geometry and injection condition on the size, and velocity distribution of the spray.