SPRAY IN CROSS FLOW OF A ROTARY ATOMIZER

Abstract

This paper presents an experimental investigation of fuel sprays generated by a rotary atomizer exposed to a cross flow of air. The effects of two variables, the rotational speed and cross-flow velocity, on the droplet sizes were studied. The rotary atomizer was driven at speeds up to 15,000 rpm with a fuel flow rate of 15 kg/h and cross flow from 10 to 150 m/s. For any given rotational speed, the fuel droplet sizes decreased as the air cross flow increased, reaching an almost constant value of about 8 μm at 150 m/s cross-flow velocity. At cross-flow velocities less than about 50 m/s, the fuel droplet sizes decreased as the rotational speed increased. However, at a cross-flow velocity greater than 100 m/s, the fuel droplet sizes did not changed significantly as the rotational speed increased. Of the two variables studied, each influenced the droplet size differently in a certain cross-flow velocity region. The rotational speed influenced the droplet size at relatively low cross-flow velocity. By exceeding a cross-flow velocity of 75 m/s, the dynamic effect of high-speed cross flow became dominant. This effect can be generalized to the Weber number based on the orifice diameter and the non-dimensional droplet size. In this correlation, the following three distinct spray regimes were identified according to the Weber number based on orifice diameter: rotation dominant, intermediate, and cross flow dominant.