Modeling sprays and atomizers

Context

Sprays, aerosols and other atomizers have many industrial applications : from nasal cleansing sprays to car engine injectors, from paint spraying to insulating foams and fire protection. Their simulation is made complex by the multiplicity and finesse of the physical phenomena governing droplet cloud generation. OptiFluides carries out CFD simulations of sprays to help in the development of such devices.

Depending on the application, the characteristics of the aerosol cloud generated must meet certain requirements:

• In the case of nasal cleansing, for example, the aim is to ensure that the spray cleans the entire mucous membrane of the respiratory tract. Vaccines currently being developed also rely on sprays to deliver the active substance to specifically targeted areas. In this case, it is necessary to check that the active substance is actually delivered.
• Droplet size distribution will be an important parameter, particularly for engines, in order to promote the mixing of fuel and oxidizer, and thus achieve better combustion efficiency.
• The shape and angle of the spray cone will be essential for correctly dimensioning a sprinkler system for fire protection or paint applicators.

Objective

Each sprayer must meet the specific requirements of the application for which it is developed. CFD numerical simulation is a powerful tool for validating the conformity of the product developed, often as a complement to experimental testing. By numerically modeling the spray or atomizer, it is possible to quantitatively determine a large number of parameters on the particle cloud generated:

• droplet granulometry,
• spray shape,
• spray cone angle,
• penetration distance,
• droplet speed,
• exchange surface…

In the project presented here, the aim was to determine the influence of the geometry of the spinning chamber on the shape of the droplet cloud.

Simulation and results

The virtual model enables us not only to validate that the product meets the requirements for which it was designed, but also to gain a better understanding of how it operates in different, specific external environments, for which it is not always possible to carry out tests or even measure our parameters of interest correctly. Similarly, the solution to be sprayed may be hazardous, limiting the feasibility of testing. In some cases, a large number of parameters need to be tested, requiring the production of numerous prototypes, with costs rapidly becoming prohibitive.

In all these cases, OptiFluides supports companies wishing to model their spray and atomization processes. During the product design phase, or to better understand your process, numerical simulations are a major asset for the success of your project.

Here’s a video example of spray modeling using ANSYS Fluent software.