###### Abstract  
To address the frequent cleaning requirements of casting molds in bridge tower construction, a wall-climbing cleaning robot based on negative pressure adsorption is designed to safely and efficiently replace manual labor for cleaning tasks. The primary focus of this paper is the establishment of a theoretical model for negative pressure adsorption, along with an analysis of potential adhesion hazards. Initially, the robot's chassis was designed, followed by the development of a theoretical model for the rotational-flow suction unit that incorporates two critical parameters: the number of blades and their thickness. This model was validated through computational fluid dynamics (CFD) and experimental methods. The findings indicate that, with fewer blades, an increase in blade quantity significantly improves the distribution of nonlinear velocity in the z-plane, resulting in a substantial enhancement of suction force up to a certain limit. As the number of blades increases, the thickness of the blades primarily influences the volume of air within the rotating domain, thereby affecting the suction force; thinner blades are preferable. Moreover, this study reveals that square suction units provide greater suction force compared to circular ones, attributable to their superior negative pressure effect and larger adsorption area. The most critical adhesion risk identified is leakage at the edges of the suction unit. s +
Footnote †: journal: Applied sciences  
article  
[color=gray!20,][color=gray!20,][color=gray! Negative pressure adsorption is more commonly used in the development of wall-climbing robots. Its fundamental principle is that the internal air pressure of the suction unit is lower than the external atmospheric pressure, utilizing the pressure differential to achieve adhesion. The first wall-climbing robot [25] employed a fan to extract air from the adsorption device, creating a negative pressure environment to enable the adhesion function. Subsequently, the optimization of adhesion performance in negative pressure adsorption wall-climbing robots has primarily focused on two aspects: the use of multiple suction cups [26; 27] and the enhancement of sealing properties [28; 29]. The optimization approaches mentioned above primarily focus on traditional adsorption units. While adhesion performance has been significantly improved, drawbacks such as complex structures and high power consumption have emerged. Furthermore, the requirement for traditional adsorption units to maintain close contact with the working surface for effective adhesion limits the widespread application of wall-climbing robots. [PERSON] and [PERSON] introduced a novel electrically activated sucker [30], which utilizes a motor to drive blades that create a rotating airflow within the suction unit, generating a cup-shaped negative pressure distribution and consequently producing suction force. The rotating airflow effectively obstructs the circulation of air at the edges of the suction unit, solving the traditional vacuum leakage problem. This enables the electromechanical suction cup to adhere to rough, uneven, and even gap-ridden surfaces. [PERSON] [31] applied the electromechanical suction cup to wall-climbing robots, incorporating a square adsorption chamber and designing a flexible skirt structure to improve adhesion performance. This wall-climbing robot is capable of traversing rough walls and easily navigating larger recesses and protrusions. [PERSON] [32] examined the effect of blade height on the performance of the electromechanical suction unit, finding that an increase in blade height significantly increases the maximum suction force and reduces the rate of decline in suction force with changing gaps. However, this improvement diminishes with further increases in blade height. Furthermore, experiments and CFD analyses indicated that the relationship between power consumption and suction force is primarily determined by the gap size rather than the blade height.