علوم وتكنولوجيا

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Browsing علوم وتكنولوجيا by Subject "Airblast"

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    Effects of co- and counter-swirl on the droplet characteristics in a spray flame
    (ELSEVIER, 2008) Hadef, R; Lenze, B
    This paper reports measurements of droplet characteristics and flow field in a spray flame with inner and outer swirling air streams. The spatial distribution of droplet characteristics produced by the burner’s airblast atomizer was measured using dual-phase Doppler anemometry (PDA). The spray flame was operated near the lean blow-out limit at two flow conditions: co-swirling (flow rotation in the same direction) and counter-swirling (flow rotation in opposite directions). In both cases, the flame exhibited a U-shaped form and was marked by a large central recirculation zone. Based on the measurements of the droplet velocity components, differences between both configurations appeared for the counter-rotational setup mainly in the near burner region, where the decrease of total swirl causes deeper penetration of the droplets from the inner duct into the combustion chamber, resulting in a much more homogeneous distribution than the other one. The droplet size in terms of the Sauter mean diameter (SMD) shows little variation in the change of the direction swirl condition. Application of counter-swirl results in more turbulent droplet motion.
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    Measurements of droplets characteristics in a swirl-stabilized spray flame
    (ELSEVIER, 2005) Hadef, R; Lenze, B
    Experiments have been performed in a kerosene airblast atomized spray flame where the fuel supply is sandwiched between two coswirling air streams. A phase-Doppler particle sizing system was used to measure fuel droplet size, velocity and turbulent kinetic energy of droplets and gas as well as the fuel volume flux within the combustor for two values of air preheat temperature, 200 C and 400 C. The results reveal that a small liquid fuel exists in the centre of the combustor and due to larger droplets with the swirl effect; the droplets characteristics (velocity and turbulent kinetic energy) did not follow the gas ones. Based upon these measurements, an optimum swirl number will exist with every atomization and burner arrangement of a liquid-fuelled flame associated and will be different from that associated with the corresponding gas-fuelled flame. The investigated atomizer shows a marked influence of the inlet air temperature on the measured droplet size which may be attributed to the design of the internal airflow, promoting prompt atomization at the dominant atomization mode.