A spray is a dynamic collection of drops dispersed in a gas. Various experimental techniques have been developed to study these parameters. MRI is a new promising technique to study sprays: it does not require optical transparency, unlike most other techniques, and its non-invasive nature does not interfere with sample. Studying sprays with MRI has its own challenges. One of them is related to resolution vs time: sample speed changes from approx. 1 m/s to 25 m/s over 1-cm length. We are interested in measuring velocity inside the nozzle and in the near-nozzle regions. In the previous measurements, velocity mapping inside the orifice was shown to be incorrect, most likely due to the sample’s acceleration issue during our characteristic measurement time. Therefore, we need to reduce the characteristic measurement time.
In the motion-sensitized SPRITE, two stages occur at the same time: motion-encoding stage and detection stage. If we separate the motion-encoding and detection, we can use a shorter detection technique. In this work, we use a Time-of-Flight (TOF) approach for preparation and a ramped SPI sequence for detection. In the TOF approach, a portion of the liquid is excited before the nozzle, and its movement is observed by changing a time delay between the excitation and the detection. By combining the TOF with a tagging sequence, it is possible to track the motion of the liquid. The tagging sequence consists of RF pulses to modulate nuclear magnetization in a striped pattern. The motion of the liquid inside the nozzle can then be tracked quite readily, as the movement of the material is reflected by the deformation of the strips between excitation and the detection stages.