# CFD and Experimental Comparison for Micro-Pump Performance in Space Applications: A Case Study
## 1 Introduction  
Centrifugal pumps are critical components in various industries, including water distribution and aerospace propulsion, where the drive to maximize efficiency and reliability while minimizing costs and environmental impact is increasingly important. Addressing these challenges requires a multidisciplinary approach that integrates advanced numerical analyses, experimental validations, and innovative optimization techniques. Recent research has provided valuable insights into improving pump performance by optimizing key components, such as the impeller and diffuser. [PERSON] et al. [1] demonstrated that a 7-blade impeller configuration reduces hydraulic losses by minimizing secondary flows, resulting in a performance improvement of approximately 3.2% in total head compared to 5- or 6-blade configurations. However, further increases in blade count were shown to offer diminishing returns due to increased blockage and reduced flow passages. Adjustments in blade angles have also been shown to enhance hydraulic performance by improving flow guidance and reducing incidence losses at the blade leading edge [2]. Complementing geometric optimization, recent studies have emphasized the importance of accurate turbulence modeling in predicting complex flow features in pumps. [PERSON] et al. [3] found that the SST k-omega turbulence model, especially when coupled with low-Reynolds number corrections, effectively predicts vortex core positions and flow separation in centrifugal pump diffusers. Further advancements in low-specific-speed centrifugal pumps have focused on expanding the high-efficiency operating range. Optimizing blade outlet width, angle, and wrap angle resulted in a 4.18% improvement in hydraulic efficiency [4], while research into side clearance effects demonstrated reduced pump head and efficiency due to the formation of secondary flow vortices, especially in semi-open impeller designs [5]. [PERSON] et al. [6] optimized the hub contour of a high-loading centrifugal compressor using particle swarm optimization. CFD and experiments showed a 0.78% efficiency gain and improved stall margin, mainly due to better flow uniformity and reduced losses in the diffuser. [PERSON] et al. [7] evaluated a novel impeller design in double-suction pumps using CFD and experiments. The new configuration enhanced efficiency, improved flow symmetry, and reduced shaft loading, offering better hydraulic performance and energy savings. Studies on cavitation and volute tongue geometry have demonstrated that targeted design modifications can significantly reduce radial forces and enhance overall pump performance. [PERSON] et al. [8] validated CFD simulations of cavitation onset and cavitation sheet formation, showing good agreement with experimental results. In parallel, [PERSON] et al. [9] examined the influence of volute tongue configurations using CFD and found that shorter tongues and larger cutwater gaps minimized radial forces. Notably, a tongue angle 5\({}^{\circ}\) smaller than the impeller's outlet velocity angle reduced radial forces by approximately 40% at the design point. Beyond external flow structures, internal components such as balance holes have also proven critical in maintaining operational stability. Research has shown that internal leakages and the strategic inclusion of balance holes can significantly reduce axial thrust, thus enhancing pump longevity and performance [10]. As an alternative approach to managing axial loads, the use of double-suction pump configurations has also been proposed [11]. Efficiency improvements have extended to pumps operating in reverse mode, where specific geometric refinements were introduced to optimize performance. Modifications such as rounding the blades' leading edges and refining the hub/shroud interface led to measurable efficiency gains. Tests on these altered impellers revealed a maximum efficiency of 24.57% when functioning as a pump, and 22.02% in hydro turbine generator mode [12]. Advancements in diffuser design have similarly contributed to hydraulic performance.