Understanding the behavior of sprays and how they form, spread, and interact with their environment is critical across a wide range of industries. These include fuel injection, agriculture, pharmaceuticals, and chemical processing.
While these principles may be well known to professionals working in spray technology or fluid dynamics, this overview is intended to support engineers, researchers, and technical stakeholders who may be new to the field. Laser Sheet Imaging (LSI) provides a precise and non-intrusive method for visualizing and analyzing spray structures in high detail.
One spray pattern of particular interest is the hydraulic full cone spray. It is frequently generated by industrial nozzles due to its widespread use and critical role in achieving uniform coverage, efficient atomization, and consistent delivery across applications. Along with the flat-fan spray, the hydraulic full cone spray is among the most commonly used spray patterns in industrial practice. Given its prevalence and importance across industries, we will use it as the subject of our characterization and testing.
Laser Sheet Imaging (LSI) is a non-intrusive optical method used to visualize and analyze the distribution of particles or droplets in a spray. The methodology involves projecting a thin sheet of laser light through the spray, where it interacts with transparent or refractive droplets. As the light scatters off these droplets, a camera captures the resulting intensity pattern, forming the basis for detailed spray analysis.
Here’s how it works:
In conclusion, Laser Sheet Imaging (LSI) provides a planar snapshot of a spray’s internal structure. It allows researchers and engineers to observe features such as droplet density, spray boundaries, and flow patterns. By analyzing the resulting distribution, they can simulate spray overlaps. This is especially important in applications like spray coating, fuel injection, and agricultural spraying, where uniform coverage and controlled overlap are critical for both performance and efficiency.
A full cone nozzle was operated at a pressure of 20 psi, with the measurement plane positioned 20 inches downstream from the nozzle orifice. A thin laser sheet was projected perpendicularly through the spray at this location, illuminating a planar cross-section of the spray volume.
A camera was positioned 45 degrees above the laser plane and downstream from the laser source. This angled setup allowed it to capture the scattered light intensity from the droplets. A total of 500 successive images were recorded. These were then averaged to produce a single two-dimensional image representing the spatial distribution of droplets within the illuminated plane.
The 3D visualization of the spray data illustrates intensity as a function of position, offering a volumetric view of droplet concentration across the spray field. The results show that spray concentration is highest at the centerline of the nozzle and diminishes toward the outer edges. The data exhibits an exponential decrease in intensity from the center to the periphery, highlighting a significant difference in scale between the dense core and the outer spray regions. This contrast demonstrates how a full cone spray can quickly lose it's effectiveness over distance.
To further analyze the spatial distribution, the 2D spray data, visualized in 3D, was collapsed into a single dimension by summing intensity values along the vertical (y) direction at each horizontal position. This process effectively reduces the volumetric dataset into a single horizontal profile, illustrating how droplet concentration varies across the width of the spray. The resulting histogram reveals the overall shape and symmetry of the spray pattern, making it easier to interpret centerline intensity and the rate of falloff toward the edges. This 1D profile also serves as a bridge to traditional patternator methods, which rely on physical droplet collection along a linear axis. In practice, full cone nozzles often produce a distribution that closely resembles a normal (Gaussian) curve, as shown below.
The symmetry of full-cone sprays makes them well-suited for predictable overlap in multi-nozzle systems. A common design guideline is to space nozzles at one-third of their spray width. This ensures that adjacent sprays overlap sufficiently to achieve uniform coverage without excessive redundancy or gaps. Such overlap considerations are especially important in applications like agricultural spraying and surface coating. Additional analysis can be performed by duplicating and shifting the one dimensional profile to simulate adjacent sprays. By comparing the combined profile to a uniform distribution, one can compute a coefficient of variation—assuming ideal conditions without plume interaction or droplet interference. However, this level of analysis will not be discussed here.
The study demonstrates how Laser Sheet Imaging offers a powerful, non-intrusive technique for detailed visualization and analysis of full cone spray patterns. By capturing the spatial distribution of droplets within a laser-illuminated plane, LSI enables quantitative insights into spray structure, concentration gradients, and symmetry. The ability to reduce 2D spray data into meaningful single dimensional profiles facilitates comparison with traditional methods and supports design considerations for nozzle placement and spray overlap.
Overall, LSI provides engineers and researchers with a robust tool to optimize spray performance across a variety of industrial applications, improving uniformity, efficiency, and control in processes that depend on precise spray behavior.