Impacts of flash boiling plume interactions on atomization evaluated using two-dimensional optical slit nozzles

Flash boiling atomization is a promising approach for liquid fuel energy conversion purposes, especially for alternative fuels and zero-carbon fuels. However, the fundamental mechanisms of flash boiling atomization is quite different from typical sub-cooled atomization both in the primary breakup mechanisms and plume interference principles. This work aims to investigate the spray plume interaction impacts under flash boiling injection schemes. To reduce the complexity in handling the dense spray regime for practical spray injectors, twodimensional slit nozzles created by quartz blocks and thin channels are employed. Divergent, straight, and converge nozzles are designed and examined to evaluate the impact of nozzle design under the same thermodynamic conditions. Nozzles with a 2D expansion cavity are also tested to further reduce the optical depth in the observation direction. Various optical diagnostics methods including backlit measurement, phase Doppler interferometry, and the optical flow method are used to investigate different characteristics of the resultant superheat flows from different perspective. The experimental investigations reveal the interference mechanism of the two-plume nozzle with the increment of fuel temperature, as well as its impacts on atomization efficiency from the perspective of droplet sizes.