Matouš Zaremba

Comparison of twin-fluid atomizers using a phase Doppler analyser

The quality of atomization is crucial in combustion processes, especially in cases of highly viscous fuels. Twin-fluid atomizers have been developed for atomizing heavy and waste fuels and they have undergone significant development in the last decades. Nevertheless, in order to design an atomizer for a given industrial application, a comparison of different atomizers at similar operating conditions is required. This paper focuses on the description and comparison of two internally mixed twin-fluid atomizers at the same operating regime. The Y-jet and the Inverse-effervescent atomizers were examined. The phase-Doppler analyzer was used to measure the velocity and size of droplets in a radial profile in the spray. Data were sorted out into classes with respect to the droplet size and the motion analysis was done for both atomizers.

Study of airflow during respiratory cycle in semi-realistic model of human tracheobronchial tree

This article deals with study of airflow under breathing process, which is characteristic by unsteady behavior. Simulations provided by computational fluid dynamics (CFD) was compared with experiments performed on similar geometry of human upper airways. This geometry was represented by mouth cavity of realistic shape connected to an idealized tracheobronchial tree up to fourth generation of branching. Commercial CFD software Star-CCM+ was used to calculate airflow inside investigated geometry and method of Reynolds averaging of Navier-Stokes equations was used for subscribing the turbulent behavior through model geometry. Conditions corresponding to resting state were considered. Comparisons with experiments were provided on several points through trachea and bronchial tree and results with respect to inspiratory and respiratory part of breathing cycle was discussed.

Influence of Working Parameters and Primary Breakup Conditions on the Quality of Twin-Fluid Atomizers Spray Quality

In this study we investigated four twin-fluid atomizers with different internal mixing mechanisms: Y-jet, outside in gas (OIG), outside in liquid (OIL) and CFT atomizers. The main goal was to relate the measured droplet sizes, characterized by the Sauter mean diameter (ID32), to the corresponding working regimes of atomizers and primary breakup conditions characterized by the criterion Dmax, estimated from critical Weber number of the primary breakup. For the OIL, OIG and CFT atomizers, the common relation of the primary breakup characteristics and normalized droplet sizes (ID32/Dmax) was found. As the Y-jet atomizer showed a different trend, which was related to the considerably lower Weber numbers of the near-nozzle flow, a change in the normalization criterion was necessary to obtain similar results as for other tested atomizers. The main benefit of presented results is the potential to predict spray droplet sizes entirely from primary breakup characteristics regardless of the atomizer’s design or the atomized liquid.