# Optimization of Customized Industrial Pneumatic Nozzle to Reduce Noise Emissions
## 1 Introduction  
Despite the extensive use of mechanical and electronic components, pneumatics continues to play an important role in automation machines owing to certain important advantages. Pneumatic systems are known for their reliability and efficiency. They are relatively simple in design and offer precise control over the motion and force applied, allowing for the accurate positioning and sequencing of the automation devices. Moreover, they are inherently safe to use, versatile, and cost-effective, and they offer excellent responsiveness and high-speed operation. They can quickly start, stop, and change direction, allowing for rapid and precise movements in automated devices. This flexibility is particularly beneficial in applications that require speed and agility, such as packaging, sorting, and assembly lines. Although pneumatic systems tend to produce less noise when compared with other types of automation systems, there is currently a demand for noise reduction for the comfort of operators or compliance with noise regulations. European Directive 2006/42/CE [1] imposes a maximum permitted noise level of 87 dB in work environments. Some European countries, such as Sweden and Denmark, have stricter legislation (85 dB). This study specifically investigated the problem of reducing the noise emitted by the pneumatic nozzles installed on the capsuling machines manufactured by Robino & Galandrino S.p.a. (Canelli, Asti, Italy). Capsuling machines are used in the wine industry in the final stages of the bottling process and are responsible for inserting the capsules into the bottles of wine and sparking wine already encased in a cage. The two main sources of noise in capsuling machines are two operations called ejection and distribution. The ejection operation transfers the caps using air shots generated by the nozzles. It involves separating the stacked caps and successively throwing them into the rotating cylindersthrough four impulsive air shots applied using a self-developed 3D-printed nozzle. The distribution phase inserts the capsule, temporarily held inside the rotating cylinders, onto an already caged bottle by using impulsive air shots; this phase is currently implemented using a commercial nozzle. [PERSON] and [PERSON] attempted to improve its performance and reduce the noise [2]. The present study endeavored to analyze the airflow emitted during the ejection phase by the nozzle, and to design new solutions that focus on improving the nozzle geometry while maintaining the speed and power of the air jets as constant as possible. Noise is a very broad topic and is well understood in terms of its perception, but the study of air jets and their noise-producing capability continues to have some uncertainties [3; 4]. Only a few studies have explored the reduction in this noise. An analytical treatise of this phenomenon is possible; however, simplifications and/or approximations are generally introduced in such analyses. [PERSON] [5] proposed an analytical approach that provided some useful insights for designing and studying new sound-reducing nozzles. The author showed that the acoustic power generated by a supersonic jet is proportional to the area of the jet section multiplied by the eighth power of the velocity. Empirical and experimental approaches have been widely used because they allow for the testing of real and complex geometries and generate practical interpretations [6; 7; 8; 9]. Currently, a third interesting method is widely used: the study of the nozzle using computational fluid dynamics (CFD) simulations [10]. CFD simulations allow for the investigation of the behavior of the fluid flow and its interaction with various objects or boundaries. In CFD simulations, the fluid domain is divided into a grid or mesh of small control volumes or elements. These control volumes are used to discretize the fluid equations into a set of algebraic equations that can be solved numerically. The equations typically include the conservation of mass, momentum, and energy, which govern the fluid flow behavior.