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Multiphase pumps are core equipment for offshore plant industry. They are utilized in diverse areas. According to a report about the tendency of multiphase pumps for offshore plant, a helico-axial pump is the most preferred. A helico-axial pump with advanced technologies is widely known to have large handling capacity and operability even at high GVF ranges. However, its disadvantage is that its mechanical efficiency is lower than other multiphase pumps. Because of this, a numerical optimization was performed in this study to enhance the hydraulic performance of multiphase pumps. Before numerical optimization, reliability verification of numerical analysis for single-phase and multiphase flow was carried out. To perform a single objective optimization for high efficiency, design variables and ranges were selected. The single objective optimization was conducted for both impeller and diffuser. The objective function was evaluated at design points using Latin-hypercube sampling, one experiment technique, in design ranges. The performance of the experiment sets was evaluated using advanced computational fluid dynamics. After that, the response surface of a second-order polynomial function which was produced based on the performance evaluation results was used to find the optimal point. The results showed remarkable increases in a higher performance level than the base model. The reason for performance improvement was analyzed through comparison of the internal flow field. Additionally, numerical results were compared to results of performance evaluation through experiment.

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This research aimed to systematically maximize hydraulic efficiency and suction specific speed for mixed-flow pump using a commercial CFD packages and optimization tool. First, mixed-flow pump was initially designed according to the traditional design method, and then the blade shape was redesigned by focusing on the hydraulic efficiency. Second, the efficiency-oriented optimum design was selected as the reference model. The objective was to improve the suction specific speed under the specific condition of the mixed-flow pump through the multi-objective optimization technique. The incidence angles and meridional plane were optimized through a systematic optimization process, namely, central composite method and response surface approximation. The optimization results indicated that the suction specific speed values of the reference and optimum model were 88.13 and 289.65, respectively. Furthermore, the hydraulic efficiency was kept within ± 1% compared to the reference model as the constraint condition. The hydraulic efficiency of the reference and optimum model were 91.44% and 90.40%, respectively. The reasons for the improved efficiency and suction performance were investigated through internal flow field analysis. Finally, the reliability of the optimization was demonstrated by comparing the numerical and experimental results. ARTICLE HISTORY

A 58-year-old female presented with ocular pain and decreased visual acuity in both eye. She had received periocular acupuncture therapy 4 days earlier. Dilated fundoscopy revealed vitreous hemorrhage. B-scan ultrasonography revealed vitreous opacity. Thus, at the request of the patient, vitrectomy was performed in only the right eye, and did not performed in the left eye. Intraoperatively, we identified retinal laceration in the temporal and inferior retina. In the left eye, the sites of retinal hemorrhage were observed in the temporal and inferior retina in the fundus examination, and a barrier laser photocoagulation was performed around the lesion. At the three-month postoperative follow-up, the patient's visual acuity was 0.5 in the right eye without macular edema. In the left eye, visual acuity was 0.01 with macular edema observed on optical coherence tomography. Conclusions: Authors present a case of a patient with vitreous hemorrhage and ocular perforations caused by periocular acupuncture therapy in both eye, able to compare the results of eyes that performed vitrectomy and that did not performed vitrectomy in a same patient. The recovery of visual acuity in eye that performed vitrectomy was better than eye that did not performed vitrectomy. Therefore, we consider performing vitrectomy in patients with eye perforation.