Stirred tank mixers play a vital role in a wide range of industrial processes, where efficient mixing of gases, liquids, and solids is essential. Enhancing the performance of these systems is key to achieving greater energy efficiency and reduced costs. This article focuses on three critical dimensions of agitation vessel tank performance: energy consumption, mixing time, and impeller configuration. Minimizing energy use is fundamental for ensuring sustainable and cost-effective operations. Similarly, mixing time directly influences overall efficiency and is closely tied to both impeller design and the rheological properties of the fluid. Research in this area reveals significant potential to shorten mixing durations, thereby increasing throughput. Geometry of impeller, a core design factor, must be tailored to specific applications and plays a central role in determining mixing behavior. Understanding the interplay between fluid flow and impeller structure is essential for designing high-performance, economical mixing systems.

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The characteristics of pulsatile turbulent flow in a 90° pipe bend with a radius ratio of Rc=4 were investigated experimentally. Experiments were conducted with a mean Reynolds number Reta=20000, Womersley numbers of α=10 and 30, and flow ratio of η=0.5. The axial and secondary flow velocities were measured by laser Doppler velocimetry in sections from upstream to downstream of the bend. The periodic changes in their distributions were investigated and the effects of α on their transitions along the bend axis were discussed. For a low α, the flow velocities exhibited periodical changes similar to a steady flow with instantaneous Re. However, with an increase in α, they changed abruptly near the bend exit and became more complex. In particular, the axial velocity distribution at the maximum flow rate exhibited a peculiar change in the latter half of the bend, changing to a depressed shape with two maxima from a triangle, and the secondary flow velocity intensified significantly near the bend exit. Simultaneously, the turbulence intensity increased, and just behind the bend exit, the region with a large value extended to the central region.

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The study clarified the value of application to industrial turbomachinery with respect to multi-materialization using wire arc additive manufacturing (WAAM). First, the tensile strength was investigated by conducting tensile tests on multi-material tensile specimens made of nickel base alloy and stainless steel, which were fabricated using WAAM, under several heat treatment conditions. Then, an axial-flow impeller with multi-material blades made of nickel base alloy and stainless steel was fabricated using WAAM and machining. Furthermore, the fabricated impeller was attached to a centrifugal pump to demonstrate that it can function as an impeller for the pump. It was concluded from these results that the multi-material technology using WAAM is an option for the fabrication of industrial turbomachinery.

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The characteristics of oscillating flow field have always been one of the hot issues in fluid mechanics. However, compared with the study of oscillating disturbance flow superimposed on the stable mainstream, there are relatively few theoretical or experimental studies on the instability of pure oscillating flow. Based on this, this paper uses a peristaltic pump to alter gas pressure gradient and induce reciprocating flow in a vertical U-tube (Rc/D=2.5). The particle image velocimetry (PIV) technology is used to build a visual experimental platform, and the pure oscillating flow field experiments in the U-tube under different oscillation periods are carried out. We modeled the fluid dynamics of the coupled gas-liquid interaction. Analyze the period variation law, the flow field characteristics of Oscillatory Reynolds number (111 ≤ Re δ ≤ 226，Based on Stokes layer thickness), Womersley number (1.69≤Wo≤2.21), transient velocity flow field and vorticity distribution of alternating pipe flow under different oscillation frequencies (0.28-0.49Hz). Experiments show that the interaction of inertial force and viscous force affects the fluid oscillation when the gas-driven liquid flows in a vertical U-tube. The velocity of the flow field changes periodically. The maximum instantaneous velocity of the flow center at different positions is consistent, and the axial velocity has no obvious gradient. The vector peak is affected by the period and phase. when increases, the instability of the liquid flow field intensifies also, and a complex gas-liquid mixed flow multiphase flow mode appears in the U-tube. This research aims to advance understanding and application of unstable pure oscillating flow fields, offering valuable experimental insights for related researchers.

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The hump region is inevitable when the pump turbine operates in the pump mode, which poses a threat to the safe and stable operation of the unit. The prototype pump turbine is selected as the research object and the numerical simulation method is used to analyze the flow characteristics inside the runner and guide vanes. The results show that the relative flow angle irregular fluctuations at the blade leading edge result in the formation of a positive attack angle under low discharge conditions, leading to the occurrence of flow separation. The development of separation vortex causes rotational stall inside the flow channel, blocking the flow passage. In severe cases, backflow vortex forms in the blade outlet leads to water flow back into the runner. The stall vortex also appears in the double row cascade, which not only blocked the water, but also caused the water flow that had already passed through the guide vanes and stay vanes to form a backflow in the other channels. The rotational stall inside the runner and guide vanes deteriorates the flow field, resulting in a significantly increase in hydraulic losses, which is the main reason for the head decrease in the hump region.

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When the multistage pump conveying medium contains impurity particles, the particles will cause the impeller and balance drum clearance wear, resulting in the hydraulic performance of multistage pump is reduced, and the axial balancing ability of balance drum is weakened. In this paper, RNG k-ε turbulence model and DPM discrete phase model are used to simulate the solid-liquid two-phase flow of multistage pump, and the trajectory, distribution and wear of particles under different density and size of solid particles are studied. The results show that the higher the solid particle density and particle size, the lower the pump head and efficiency, and the axial force is suppressed within a certain range, and the axial force decreases first and then increases. With the increase of particle density and particle size, the wear degree of blade working face, guide vane and pressurized water chamber is aggravated, while the wear degree of blade back is weakened. Particles mainly gather in impeller inlet, blade working face, guide vane outlet wall and pressurized water chamber outdoor wall. The lager the particle density and particle size, the heavier the overall wear degree of the balance drum system, mainly the wear of the balance cavity wall and the balance pipe wall. The accumulation of large density particles and large size particles causes serious wear in balance drum clearance and balance pipe bends. The research results can provide theoretical guidance for the stable operation of balance drum system of multistage pump.

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