Schlieren image velocimetry is based on light de ection through ow heterogeneities and image crosscorrelations. This is a low-cost and relatively low complexity technique that allows measurement of the droplet velocity eld in a large region of a spray. A Z-type Toepler schlieren system with a high-speed camera was used to determine mean vertical and horizontal droplet velocities, as well as the cone angles of sprays produced by a pressure swirl injector with characteristic geometric constant K = 2. Different LEDs and digital lters were evaluated for edge detection and improvement of image contrast. Open software was adopted for digital image processing and velocimetry. Interrogation windows and overlaps of different sizes were tested to obtain an appropriate correlation for determination of the velocity eld.The digital images were obtained with 5×10 3 fps and a resolution of 2.77 pixels/mm. Since the swirl sprays analysed presented instabilities, a number of 100 cross-correlations of images was required to reduce mean velocity uctuations. Injection pressures varied from 0.05 to 7 bar and mass ow rates varied from 1.389 to 13.89 g/s, using water as test uid. The wideband warm white LED with Laplacian or high-pass lters provided velocity data for a larger range of injection pressures. Mean axial velocities varied from 3.3 to 11.3 m/s, approximately, with mean horizontal velocities varying from around 0.17 to 3.3 m/s for pressures from 0.05 to 3.22 bar. The velocity data were compared to microscopic shadowgraphy results, showing a good agreement. Spray cone angles ranged from about 32.5 o to 69.5 o , for injection pressures from 0.05 to 7 bar, and results of triangulation with a blue LED were closer to semiempirical data.

Gelled propellants are an interesting option for rockets and missiles propulsion systems, since they combine high performance with facility of handling and storage. These characteristics are due to the shear thinning non-Newtonian behavior of gels. High shear rates can lead to extensive liquefaction of gelled fluids. This liquefaction offers the possibility to develop engines that can be throttled like liquid propellant engines. Impinging jet injectors are commonly used in propulsion systems applications since they can be easily manufactured and can provide good atomization and mixing characteristics within a short distance. Green propellants represent a low toxicity and high performance alternative to the conventional hazardous propellants. This work compares analytical solutions with images of the sheet shapes formed by the impingement of two round jets of water, liquid hydrated ethanol and gelled hydrated ethanol. Breakup lengths and maximum widths of the sheet shapes are determined as function of the Reynolds number. The analytical plotted sheet shapes have shown good agreement with experimental data for water and liquid hydrated ethanol, but not for gelled hydrated ethanol. The aspect ratio was approximately constant, around 2, for water and liquid hydrated ethanol, while for gelled hydrated ethanol the breakup length increased exponentially and the aspect ratio increased linearly with Reynolds number.

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