Multiple impinging jet air-assisted atomization

Abstract

The growth of the aviation sector triggered the search for alternative fuels and continued improvements in the combustion process. This work addresses the technological challenges associated with spray systems and the concern of mixing biofuels with fossil fuels to produce alternative and more ecological fuels for aviation. This work proposes a new injector design based on sprays produced from the simultaneous impact of multiple jets, using an additional jet of air to assist the atomization process. The results evidence the ability to control the average drop size through the air-mass flow rate. Depending on the air-mass flow rate there is a transition between atomization by hydrodynamic breakup of the liquid sheet formed on the impact point, to an aerodynamic breakup mechanism, as found in the atomization of inclined jets under cross-flow conditions. The aerodynamic shear breakup deteriorates the atomization performance, but within the same order of magnitude. Finally, our experiments show that mixing a biofuel with a fossil fuel does not significantly alter the spray characteristics, regarded as a step further in developing alternative and more ecological fuels for aero-engines.

Influence of Energy Exchange Between Air and Liquid Streams on Spray Characteristics and Atomization Efficiency of Water-Air Impinging Jets

“…For example, it is a fact that, at part load, the atomization quality of twin impinging liquid jet atomizers can drop and one proposed method to remedy this is to use an additional gas jet (Inoue et al 2013, Pizziol et al 2018, Xia et al 2017, 2018. This paper links the origin of the behavior of the atomization characteristics and the resulting atomization efficiency to the measured energy exchange between the air and liquid streams in the near nozzle region for the first time.…”

“…A number of experimental and computational studies on impinging liquid and air jet atomizers were conducted in the past (Boden et al 1999;Ashgriz 2011;Avulapati and Venkata 2013;Inoue et al 2013;Prabhakaran and Basavanahalli 2013;Delgado 2014, Xia et al 2017;Xia et al 2018a;Xia et al 2018b;Pizziol et al 2018). Avulapati and Ravikrishna (2013) used Particle/Droplet Imaging Analysis (PDIA) to characterize the sprays.…”

“…Avulapati and Ravikrishna (2105) evaluated the performance of such configuration for the atomization of pure plant oils and showed that airassist atomizers deliver same level of atomization as conventional Diesel fuel type pressure injectors. Pizziol et al (2018) studied twin and multiple impinging jets air assisted atomization using laser diffraction to measure the line of sight averaged SMD along a section of the sprays.…”

“…Recently, Pizziol et al (2018) introduced another formalism for the atomization efficiency that relates the final volumetric surface energy of the droplets to the sum of the kinetic energy components of the air jet and the liquid jets. This led to the correlation of Eq.…”

“…This can be worse for non-axisymmetric sprays, generated by the impingement of an air stream on liquid streams at an angle (e.g. Lefebvre 1992, Xia et al 2017, Avulapati and Ravikrishna 2013, Pizziol et al 2018). Avulapati and Ravikrishna (2013) used local mean diameters and Pizziol et al (2018) used line of sight average droplet size measurements limited to only a small fraction of the sprays.…”