## 1 Introduction  
The major characteristics of an axial flow fan are high efficiency, low noise, and large flow rate. As a result, usually, axial-flow fans are installed for the purpose of heat dissipation in large-sized equipment to meet the needs of a spacious working environment and the wide-spread airstream. Nowadays, an axial flow fan is used extensively in the lower-resistance system for the purpose of ventilation, and its large flow rate has additional benefits, causing convection in the spacious environment. Because more heat transformation is necessary in a large area, the characteristic of convection in a large area is the reason why families always utilize an axial-flow fan (stand fan) in the living area.  
To improve the axial-flow fan's performance, previous experimental investigations [1] have identified several important factors, such as the blade profile, blade setting angle, and tip clearance. In 1992, [PERSON] and [PERSON] [2] conducted an extensive experiment to evaluate the effect of tip clearance on the performance of the axial-flow fan. Their conclusion indicates that the tip clearance effects are dependent on the rotor type and its size, as well as the blade shape and number. Hence, it was well demonstrated that the performance characteristics can be improved by choosing the appropriate blade parameters and reducing tip clearance.  
In 2002, a small centrifugal fan was successfully generated for the thermal management of laptop computers by utilizing an integrated scheme, which consists of fan design, mockup manufacture, experimental verification, and numerical simulation. A good agreement between numerical simulation and test results successfully indicates great potential to reduce the expensive experimental work by using CFD (computational fluid dynamics) tools [3]. Recently, [PERSON] and [PERSON] [4; 5; 6] utilized an inverse cascade method to design the performances of centrifugal and axial flow fans. In this study, CFD simulations and experimental measurements are utilized to perform flow visualization, torque calculation, efficiency estimation, and noise analysis.  
In 2014, [PERSON] and [PERSON] [7] used the CFD software Fluent to create the model of a fan and carry out a numerical simulation and flow field visualization. The results showed that the unique inhale-return phenomenon happens for an inappropriate housing. Several key parameters, such as fan guard, housing ring, inlet-to-outlet area ratio, and blockage height, are evaluated to find out the criterion necessary to avoid the inhale-return flow. Consequently, the study finds that the fan guard changes the airflow to a wider distribution with a lower velocity.  
Consequently, through a literature survey about fan design, it is clear that the reliable CFD tool and key design parameters on the axial-flow fan are well established and identified. However, this dependable approach has not been applied on the stand fan, which is an essential appliance in every family. This implies that the stand fan should be investigated and analyzed in a systematical manner to improve its aerodynamic performance and flow characteristics to meet the ventilation demand. Therefore, this study chooses a commonly used 14\" stand fan to demonstrate this comprehensive investigation. At first, the design parameters of the rotor and protective cover of the stand fan are systematically examined via a numerical tool to identify the corresponding influence on fan performance. With the aid of a comprehensive parametric study, the optimal fan design is obtained. Furthermore, a mockup of the optimal fan design is fabricated via the CNC technology to test the fan performance. Later, the numerically calculated flow rate and energy efficiency are validated by comparing them with the experimental measurements. Thus, this research intends to establish a reliable and systematic scheme to design the stand fan. Also, the corresponding performance influences caused by those important parameters will be analyzed to serve as the design reference for the stand fan.