Jan Jedelský

HVAC automotive vents evaluation and their performance

Car passengers’ comfort is increasingly important, not only from good feelings or travel comfort point of view, but also from the transportation safety perspective, where the drivers thermal comfort is of crucial importance. The main components affecting optimal comfort are HVAC vents. This article focuses on the performance assessment of a side dashboard car vent with adjustable horizontal vanes that allow changing the air jet direction vertically along with a complete shut-off. A new measuring methodology is presented here; it simulates real and complete ventilation system conditions using a simple laboratory piece of equipment with a single vent mounted. The flow pattern as generated by the vent jet was first studied with smoke visualization, then using a two-wire constant-temperature anemometer probe. Jet orientations and boundaries were identified for particular vent settings, which are fundamental in the assessment of vent performance. The average air speed and turbulence intensity were determined. Results show that the actual jet direction differs substantially from the direction that was set by the vanes and that further research may lead to a new and improved design of automatic control of a zonal ventilation system and contribute to more accurate control of passengers’ comfort.

Impact of alternative fuel rheology on spraying process of small pressure-swirl atomizer

A systematic investigation was made to analyse the atomizing performance of a small pressure-swirl atomizer with different crude-oil based fuels and water. The atomizer performance is characterized in terms of discharge coefficient, droplet Sauter mean diameter and nozzle efficiency. Phase-Doppler anemometry was used to measure droplets sizes and velocities and to determine the mean structure of the developed spray. A strong dependence of liquid viscosity on the mass flow rate through the atomizer as well as on the spray quality was found and discussed in comparison with relevant literature.

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.