Gansu Academy of Machinery Science

Serum-free suspension culture technology for animal cells involves the division and proliferation of cells in serum-free medium as single cells or cell clusters within shaking flasks or bioreactors. This approach enables large-scale cell culture, enhances the yield and quality of biopharmaceuticals, reduces costs, and broadens the applications of animal cells. Serum-free suspension culture of adherent cells (e.g., Madin–Darby canine kidney (MDCK), Chinese hamster ovary (CHO), Vero, baby hamster kidney (BHK-21), and human embryonic kidney (HEK293) cells) has been successfully achieved through direct or indirect adaptation, medium optimization, and genetic engineering. Additionally, novel suspension cell lines, such as duck embryonic stem (EB66) and human retinoblastoma (PER.C6) cells, have been developed as potential new substrates for biopharmaceutical production. This review examines animal cell suspension culture technology and its applications in viral vaccines, recombinant proteins, and monoclonal antibodies, providing insights into the development and utilization of this important technology.

A technique integrating numerical simulations with experimental observations was hereby employed to elucidate the flow instability mechanisms during transient processes in pump-turbines, and a reversible pump-turbine was investigated for in-depth insights. Concurrently, the coupling phenomena between vortex rope and cavitation under transient conditions were systematically analysed. The results indicate that rotational and pressure gradients predominantly drive the vortex rope evolution, thereby exerting a substantial influence on cavitation development. The formation and collapse of low-pressure cavities disrupt the vortex structures while intensifying the flow instability. High tangential momentum as well as shear layers contribute to forming alternating vortex structures. Cavitation bubbles are either entrained by the vortex rope or diffuse outward, resulting in pronounced fluctuations in cavity volume. As the vortex structure evolves, it gradually transitions downstream into a more stable, axisymmetric configuration. Pressure fluctuation analysis reveals that low-frequency oscillations within the straight conical section are predominantly induced by vortex rope rotation and cavitation collapse. In the elbow region, localized pressure amplification arises from vortex-wall interactions, while the axial non-uniformity of vortex ropes and cavity distribution governs the spatial variability of pressure pulsations. Collectively, this study establishes a theoretical basis for understanding the coupling between vortex ropes and cavitation. It further offers practical guidance for controlling vortex dynamics and mitigating cavitation in engineering applications.

While prior investigations into the reporting of health economics (HE) have predominantly focused on guideline analyses at singular institutional or national levels, this study extends its scope to encompass diverse guidance documents issued transnationally across multiple institutions. Specifically, we evaluated the reporting of HE evidence in international clinical practice guidelines (CPGs) and expert consensus statements published between 2021 and 2023. The findings aim to inform the future revisions and development of such documents. A systematic PubMed search identified relevant CPGs and expert consensus statements within a specified period. Two independent researchers screened the literature, extracted economic evidence integrated into these documents, and employed descriptive analysis to summarize the reporting characteristics. Of the 8931 screened publications, 3119 (34.9%) reported HE evidence. Among these 3119 publications, 237 (7.6%) incorporated HE evidence in formulating recommendations, 220 (7.1%) utilized HE evidence for evidence grading, and 2581 (82.8%) referenced HE evidence in explanatory notes accompanying the recommendations. Current CPGs and expert consensus statements exhibit low rates of HE evidence reporting, indicating that most international guideline developers have overlooked their applications. HE evidence-through cost-effectiveness and cost-utility analyses-can optimize medical resource allocation, support clinicians in patient-centered economic decision-making, and enhance health outcomes. Future guideline development should prioritize HE evidence integration to advance the scientific rigor and clinical applicability of the recommendations.

To reveal the distortion and vibration-inducing mechanisms of the impeller tip gap flow in pump-turbines under S-shaped characteristic conditions, this study investigates a pumped storage power unit using numerical simulation. The results show that the gap flow evolves from a relatively ordered state into a multi-scale turbulent structure, driven by coupled mechanisms such as shear instability, momentum accumulation, and centrifugal tearing, leading to non-uniform flow disturbances. Within the axial gap, jet–rotation interaction induces a strong shear layer, resulting in enhanced velocity peaks and vortex structure reconstruction, which ultimately causes global flow instability. The excitation mechanism of pressure pulsation in the gap region undergoes a staged transition: initially dominated by main flow disturbances, then shifting to a self-excited dominant frequency at 2.3 fn, and finally evolving into a bidirectional coupling between the main flow and the gap flow. At specific stages, the dominant gap frequency resonates with the rotor's structural modal frequency, posing a potential risk of resonance-induced failure. These findings provide a theoretical basis for understanding internal flow instability and vibration coupling mechanisms in pump-turbines under S-characteristic conditions, and offer valuable insights for future structural optimization and vibration control strategies.

The Hydraulic Pressure Recovery Turbine (HPRT) is a liquid pressure recovery device that plays a crucial role in enhancing efficiency, reducing costs, conserving energy, and achieving emissions reduction in process industries. To improve the hydraulic performance of the HPRT, this study employs non-smooth surface microstructures in the blade design for drag reduction, based on its energy dissipation characteristics. The effects of different microstructural units on hydraulic performance and their drag reduction mechanisms are explored. The results show that, under low-flow conditions, the hydraulic performance of the microstructures decreases. However, under design and high-flow conditions, efficiency improves significantly compared to the original model. Among the microstructures, the V-shaped microstructure demonstrates the most notable effect, with a roughly 2% increase in efficiency under design conditions. The mechanisms underlying the microstructures' effects are primarily reflected in two aspects: first, they suppress the formation of separation vortices on the pressure surface of the blades, reducing energy losses within the impeller; second, the microstructures generate secondary vortices that oppose the flow direction in the near-wall region. These vortices interact with the main flow, facilitating momentum transfer and broadening the low-speed flow region near the wall. This reduces the velocity gradient, thereby decreasing Reynolds stress and viscous resistance. Additionally, the reverse vortices within the microstructures function like “rolling bearings,” converting sliding friction into rolling friction, further reducing frictional resistance.

Abstract This paper investigates the influence of cascade density on energy dissipation in the impeller of a multi-blade axial-flow pump. Three-dimensional transient numerical simulations were conducted using the SST k-ω turbulence model for impeller schemes with different cascade density, corresponding to different blade chord length and pitch. Entropy production theory was applied to locate the regions with high energy loss in the impeller. The relationships between local entropy generation, energy loss, and unsteady flow were analyzed for different cascade density. The results indicate that impeller entropy output of the multi-blade axial-flow pump is highly consistent with the head loss during testing. Turbulence dissipation accounts for more than 50% of the total energy loss, followed by wall friction, while direct dissipation is the smallest contributor. The relative loss of the impeller can be minimized by decreasing the number of blades or increasing the blade chord length. By comparing energy dissipation in blade rotation with different chord length and pitch, it is found that turbulent dissipation ability can be controlled more effectively by changing chord length, while the ability of direct dissipation can be controlled more effectively by changing the pitch.