A spray nozzle’s liquid jet tears apart into droplets through a process called primary breakup, and no one has been able to measure exactly how that happens—until now. This matters because spray atomization is everywhere: in asthma inhalers, jet engines, crop sprayers, and industrial combustion systems. The first step—primary breakup—sets the size and speed of every droplet that follows, yet it remains the least understood part of the process. Existing tools cannot capture the fluid velocity and acceleration at the liquid-gas interface where breakup begins. The PRIME team has built a new set of diagnostics that can: pulse-burst ballistic imaging combined with wavelet-based optical flow, plus two-photon laser-induced fluorescence. They will also construct two custom spray facilities with transparent nozzles to image flow inside the nozzle itself. If successful, the research will produce the first direct measurements of primary breakup dynamics. It will generate a comprehensive database for validating computational spray models. That could lead to more efficient fuel injectors, better medical aerosol delivery, and cleaner industrial processes. The project is fundamental fluid mechanics, but its tools and data are designed for long-term use by the wider spray community.
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Efficient spray atomization plays a critical role within society, ranging from effective medical treatment to cleaner propulsion systems. Primary breakup - the process of disintegrating a liquid stream into large (primary) drops - is the consequential first step of atomization, but is also the least understood for atomizing sprays. This long-standing problem exists due to a lack of experimental tools that can measure the fundamental fluid dynamics that govern the primary breakup processes at liquid-gas interfaces (LGI) at the core of the spray. PRIME is uniquely designed to address this problem. We have developed a unique set of advanced diagnostic tools that provide the exclusive capability to measure fluid velocity and acceleration at LGIs of the liquid jet and primary drops. These tools are a unique combination of pulse-burst Ballistic Imaging combined with wavelet-based Optical Flow (wOF). In PRIME, we establish our proof-of-concept tools, and develop wOF for original applications with two-photon laser induced fluorescence, to provide ground-breaking measurements that help resolve unanswered questions of primary breakup. Two spray facilities will be developed in PRIME, which provide a unique platform to apply our diagnostics for new fundamental knowledge for a range of sprays from basic to technically-relevant complex sprays. These facilities will include custom-built transparent nozzles to perform imaging measurements inside the spray nozzle. Advanced diagnostics will be combined with a suite of established imaging diagnostics (shadowgraphy, schlieren, micro-PIV) to correlate the primary breakup flow dynamics with its corresponding breakup genesis occurring inside the spray nozzle. PRIME will provide substantial breakthroughs in knowledge, and will generate a comprehensive spray database designed for the development and validation of computational models for the wider spray community. As such, PRIME is intended for long term success.
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