Schlieren Visualization of Shaping Air During Operation of an Electrostatic Rotary Bell Sprayer: Impact of Shaping Air on Droplet Atomization and Transport

Electrostatic rotary bell sprayers (ERBSs) are widely used in the automotive industry. In ERBS, atomization is facilitated using centrifugal forces which disintegrate the paint film inside the cup into droplets at the cup edge. The droplets are then transported by the flow of a shaping air (SA) and electrostatic forces to a target surface; the characteristics of these droplets dramatically influence the quality of a painted surface and the painting transfer efficiency. In the current paper, a novel Schlieren-based visualization of the shaping air in the absence of paint droplets was performed during a qualitative investigation to delineate shaping air flow behavior and its interaction with droplets and droplet transport. An infrared thermographic flow visualization (IRFV) method and droplet size measurement were used to complement the Schlieren data for providing insight into shaping air-droplet interactions. The results demonstrated the impact of different operating conditions on the SA flow pattern, and the influence SA has on the secondary atomization and transport of droplets. Hence, these experimental methods combine with a useful tool for optimizing SA configurations that improve spray quality, droplet transport, and the efficiency of ERBS operations

Spatial Positioning and Operating Parameters of a Rotary Bell Sprayer: 3D Mapping of Droplet Size Distributions

In this study, we evaluated the fundamental physical behavior during droplet formation and flow from a rotary bell spray in the absence of an electrostatic field. The impact of a wide range of operating parameters of the rotary bell sprayer, such as flow rates, rotational speeds, and spatial positioning, on droplet sizes and size distributions using a three-dimensional (3-D) mapping was studied. The results showed that increasing the rotational speed caused the Sauter mean diameter of the droplets to decrease while increasing flow rate increased the droplet sizes. The rotational speed effect, however, was dominant compared to the effect of flow rate. An increase in droplet size radially away from the cup was noted in the vicinity of the cup, nevertheless, as the lateral distances from the cup and rotational speed were increased, the droplet sizes within the flow field became more uniform. This result is of importance for painting industries, which are looking for optimal target distances for uniform painting appearance. Furthermore, the theoretical formulation was validated with experimental data, which provides a wider range of applicability in terms of environment and parameters that could be tested. This work also provides an abundance of measurements, which can serve as a database for the validation of future droplet disintegration simulations

Study of Near-Cup Droplet Breakup of an Automative Electrostatic Rotary Bell (ESRB) Atomizer Using High-Speed Shadowgraph Imaging

Electrostatic Rotary bell (ESRB) atomizers are used as the dominant means of paint application by the automotive industry. They utilize the high rotational speed of a cup to induce primary atomization of a liquid along with shaping air to provide secondary atomization and transport. In order to better understand the fluid breakup mechanisms involved in this process, high-speed shadowgraph imaging was used to visualize the edge of a serrated rotary bell at speeds varying between 5000 and 12,000 RPM and with a water flow rate of 250 ccm. A multi-step image processing algorithm was developed to differentiate between ligaments and droplets during the primary atomization process. The results from this experiment showed that higher bell speeds resulted in a 26.8% reduction in ligament and 22.3% reduction in droplet Sauter Mean Diameters (SMD). Additionally, the ligament (ranging from 40 to 400 μm) diameters formed bimodal distributions, while the droplet (ranging from 40 to 300 μm) diameters formed a normal distribution. Velocities were also measured using particle tracking velocimetry, in which size-dependent velocities could then be computed. Droplet velocities were affected more by rotational speed than droplet SMD, while ligaments were affected by other factors than the rotational speed and ligament SMD

Schlieren Visualization of Shaping Air during Operation of an Electrostatic Rotary Bell Sprayer: Impact of Shaping Air on Droplet Atomization and Transport

Electrostatic rotary bell sprayers (ERBSs) are widely used in the automotive industry. In ERBS, atomization is facilitated using centrifugal forces which disintegrate the paint film inside the cup into droplets at the cup edge. The droplets are then transported by the flow of a shaping air (SA) and electrostatic forces to a target surface; the characteristics of these droplets dramatically influence the quality of a painted surface and the painting transfer efficiency. In the current paper, a novel Schlieren-based visualization of the shaping air in the absence of paint droplets was performed during a qualitative investigation to delineate shaping air flow behavior and its interaction with droplets and droplet transport. An infrared thermographic flow visualization (IRFV) method and droplet size measurement were used to complement the Schlieren data for providing insight into shaping air-droplet interactions. The results demonstrated the impact of different operating conditions on the SA flow pattern, and the influence SA has on the secondary atomization and transport of droplets. Hence, these experimental methods combine with a useful tool for optimizing SA configurations that improve spray quality, droplet transport, and the efficiency of ERBS operations

Spatial Positioning and Operating Parameters of a Rotary Bell Sprayer: 3D Mapping of Droplet Size Distributions

In this study, we evaluated the fundamental physical behavior during droplet formation and flow from a rotary bell spray in the absence of an electrostatic field. The impact of a wide range of operating parameters of the rotary bell sprayer, such as flow rates, rotational speeds, and spatial positioning, on droplet sizes and size distributions using a three-dimensional (3-D) mapping was studied. The results showed that increasing the rotational speed caused the Sauter mean diameter of the droplets to decrease while increasing flow rate increased the droplet sizes. The rotational speed effect, however, was dominant compared to the effect of flow rate. An increase in droplet size radially away from the cup was noted in the vicinity of the cup, nevertheless, as the lateral distances from the cup and rotational speed were increased, the droplet sizes within the flow field became more uniform. This result is of importance for painting industries, which are looking for optimal target distances for uniform painting appearance. Furthermore, the theoretical formulation was validated with experimental data, which provides a wider range of applicability in terms of environment and parameters that could be tested. This work also provides an abundance of measurements, which can serve as a database for the validation of future droplet disintegration simulations

AN AHP-BASED DECISION MAKING MODEL EVALUATING THE USE OF AUGMENTED REALITY FOR BUILDING MAINTENANCE SYSTEM

This study aims to evaluate the efficacy of integrating augmented reality technology, along with promising techniques, into the building maintenance system. The goal is to investigate whether augmented reality devices may improve the support given to personnel during facility maintenance procedures. The present research offers a decision-making tool intended to assist researchers and managers in assessing and choosing an augmented reality device that has important characteristics to enhance building maintenance procedures. A decision-making process was used to identify the optimal option from three augmented reality tools: handheld devices, head-mounted displays, and projectors. A set of six main criteria was established to evaluate the three augmented reality options. The analytical hierarchy process approach was used as the decision-making tool by prioritizing a set of primary and sub-criteria among many choices. A four-tier hierarchy has been established to identify the aspects that hold greater significance for decision-makers when choosing the augmented reality tool. The prioritization of the options utilized in this study was determined by considering the comments of the stakeholders while conducting a method analysis. The findings indicate that the handheld device is the most preferred augmented reality technology for facilitating building maintenance tasks, with a ranking score of 0.5031. The second alternative demonstrated an acceptable result of 0.3166, while the projector obtained the third position with a score of 0.1803. Moreover, the primary criterion analysis revealed that reliability emerged as the most influential factor pertaining to the target, with a rank of 0.3881. In terms of the sub-criteria, stakeholders in the decision-making process assigned greater importance to data format, handle, feedback, software system integration cost, augmented reality tools or equipment, and system maintenance

Study of Near-Cup Droplet Breakup of an Automotive Electrostatic Rotary Bell (ESRB) Atomizer Using High-Speed Shadowgraph Imaging

Electrostatic Rotary bell (ESRB) atomizers are used as the dominant means of paint application by the automotive industry. They utilize the high rotational speed of a cup to induce primary atomization of a liquid along with shaping air to provide secondary atomization and transport. In order to better understand the fluid breakup mechanisms involved in this process, high-speed shadowgraph imaging was used to visualize the edge of a serrated rotary bell at speeds varying between 5000 and 12,000 RPM and with a water flow rate of 250 ccm. A multi-step image processing algorithm was developed to differentiate between ligaments and droplets during the primary atomization process. The results from this experiment showed that higher bell speeds resulted in a 26.8% reduction in ligament and 22.3% reduction in droplet Sauter Mean Diameters (SMD). Additionally, the ligament (ranging from 40 to 400 μm) diameters formed bimodal distributions, while the droplet (ranging from 40 to 300 μm) diameters formed a normal distribution. Velocities were also measured using particle tracking velocimetry, in which size-dependent velocities could then be computed. Droplet velocities were affected more by rotational speed than droplet SMD, while ligaments were affected by other factors than the rotational speed and ligament SMD