Experimental Investigation of Blade-To-Blade Pressure Distribution in Contra-Rotating Axial Flow Pump

Cao, Linlin,Watanabe, Satoshi,Honda, Hironori,Yoshimura, Hiroaki,Furukawa, Akinori Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.4

As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.

Low Speed Design of Rear Rotor in Contra-Rotating Axial Flow Pump

Linlin Cao,Satoshi Watanabe,Simpei Momosaki,Toshiki Imanishi,Akinori Furukawa 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.2

The application of contra-rotating rotors for higher specific speed pump has been proposed in our studies, which is in principle effective for reducing the rotational speed and/or the pump size under the same specification of conventional axial flow pump. In the previous experiments of our prototype, the cavitation inception at the tip region of the rear rotor rather than that of the front rotor and the strong potential interaction from the suction surface of the rear rotor blade to the pressure surface of the front one were observed, indicating the possibility to further improve the pump performance by optimizing rotational speed combination between the two rotors. The present research aims at the design of rear rotor with lower rotational speed. Considering the fact that the incoming flow velocity defects at the tip region of the rear rotor, an integrated inflow model of 'forced vortex' and 'free vortex' is employed. The variation of maximum camber location from hub to tip as well as other related considerations are also taken into account for further performance improvement. The ideas cited above are separately or comprehensively applied in the design of three types of rear rotor, which are subsequently simulated in ANSYS CFX to evaluate the related pump performance and therefore the whole low speed design idea. Finally, the experimental validation is carried out on one type to offer further proofs for the availability of the whole design method.

Low Speed Design of Rear Rotor in Contra-Rotating Axial Flow Pump

Cao, Linlin,Watanabe, Satoshi,Momosaki, Simpei,Imanishi, Toshiki,Furukawa, Akinori Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.2

The application of contra-rotating rotors for higher specific speed pump has been proposed in our studies, which is in principle effective for reducing the rotational speed and/or the pump size under the same specification of conventional axial flow pump. In the previous experiments of our prototype, the cavitation inception at the tip region of the rear rotor rather than that of the front rotor and the strong potential interaction from the suction surface of the rear rotor blade to the pressure surface of the front one were observed, indicating the possibility to further improve the pump performance by optimizing rotational speed combination between the two rotors. The present research aims at the design of rear rotor with lower rotational speed. Considering the fact that the incoming flow velocity defects at the tip region of the rear rotor, an integrated inflow model of 'forced vortex' and 'free vortex' is employed. The variation of maximum camber location from hub to tip as well as other related considerations are also taken into account for further performance improvement. The ideas cited above are separately or comprehensively applied in the design of three types of rear rotor, which are subsequently simulated in ANSYS CFX to evaluate the related pump performance and therefore the whole low speed design idea. Finally, the experimental validation is carried out on one type to offer further proofs for the availability of the whole design method.

Experimental Investigation of Blade-To-Blade Pressure Distribution in Contra-Rotating Axial Flow Pump

Linlin Cao,Satoshi Watanabe,Hironori Honda,Hiroaki Yoshimura,Akinori Furukawa 한국유체기계학회 2014 International journal of fluid machinery and syste Vol.7 No.4

As a high specific speed pump, the contra-rotating axial flow pump with two rotors rotating reversely has been proved with higher hydraulic and cavitation performance, while in our previous researches, the potential interaction between two blade rows was distinctly observed for our prototype rotors designed with equal rotational speed for both front and rear rotors. Based on the theoretical and experimental evidences, a rotational speed optimization methodology was proposed and applied in the design of a new combination of contra-rotating rotors, primarily in expectation of the optimized blade pressure distributions as well as pertinently improved hydraulic performances including cavitation performance. In the present study, given one stationary and two rotating frames in the contra-rotating rotors case, a pressure measurement concept taking account of the revolutions of both front and rear rotors simultaneously was adopted. The casing wall pressure data sampled in time domain was successfully transferred into space domain, by which the ensemble averaged blade-to-blade pressure distributions at the blade tip of two contra-rotating rotors under different operation conditions were studied. It could be seen that the rotor pair with the optimized rotational speed combination as well as work division, shows more reasonable blade-to-blade pressure distribution and well weakened potential interaction. Moreover, combining the loading curves estimated by the measured casing wall pressure, the cavitation performance of the rotor pairs with new rotational speed combination were proved to be superior to those of the prototype pairs.

Ion Exchange Synthesis of Bi2MoO6/BiOI Heterojunctions for Photocatalytic Degradation and Photoelectrochemical Water Splitting

Linlin Fan,Bo Wei,Lingling Xu,Yang Liu,Wanlu Cao,Ning Ma,Hong Gao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.8

In this study, flower-like Bi2MoO6/BiOI heterostructure photocatalysts were synthesized via an anion exchange method using BiOI as precursor. The composition of Bi2MoO6/BiOI can be easily controlled by adjusting the MoO2- 4 /I- molar ratio. Photocatalytic activity studies based on the degradation of Rhodamine B (RhB) show that Bi2MoO6/BiOI = 50% photocatalyst exhibited the best performance under visible light excitation. The radical scavengers test demonstrated that holes was the main reactive species for the degradation of RhB, and O2- also took part in the photodecomposition process. Photoelectrochemical measurement reveals that the Bi2MoO6/ BiOI = 50% exhibit enhanced carrier densities, charge separation and photocurrent compared with the original Bi2MoO6 and BiOI. Our results show that bismuth-based heterojunctions fabricated through the anion exchange method could be a cost-effective approach to improve the photocatalytic activity and photoelectrochemical performance of BiOI.

Effect of meridional shape on performance of axial-flow fan

Xin Chen,Linlin Cao,Peng Yan,Peng Wu,Dazhuan Wu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

In this study, the effect of impeller meridional shape on the performance of axial-flow fan is investigated by CFD method. Three axialflow fan impellers with different meridional shapes are designed. The blade angle, blade stacking condition and other structure factors of the impellers are all remained consistent. The performance curves of the three impellers are calculated and compared. In almost all the interested flowrate range, the impeller W3 with an inverted-isosceles-trapezoid meridional shape and the longer blade camber achieves both the higher pressure rise and the higher efficiency than the other two impellers. A two-stage axial-flow fan designed on basis of W3 is manufactured and tested. Test results show good agreement with the calculated performance curves. Further, analyses of the CFD results are conducted to reveal the reasons for the different performance. A newly-defined Local Euler head (LEH) is introduced to represent the distribution of the major Euler work in the axial-flow fan. And the LEH distributions in the three impellers are obtained. W3 achieves the highest LEH at blade Trailing edge (TE), because it could perform the most Euler work to the fluid with the longest blade camber. Then losses in the impellers are analyzed by means of the entropy generation. Among the losses in impeller, the tip leakage loss and endwall friction loss are dominated at design flowrate. The generation condition of the tip leakage loss shows significant differences among the three impellers. And the whole power loss in impeller of W3 is slightly higher than those of the other two models. However, the power loss difference among the three impellers is negligible. And due to the highest shaft power, the efficiency loss of W3 is the lowest of all.

Effect of obstacle position on attached cavitation control through response surface methodology

Bangxiang Che,Linlin Cao,Ning Chu,Dmitriy Likhachev,Dazhuan Wu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

The span-wise obstacle on the suction surface of a hydrofoil has been verified to be an effective passive control method for cloud cavitation. The position of obstacle significantly influences the performance of cavitation control. In this research, we investigated the effect of obstacle position on attached cavitation control on the suction surface of a NACA0015 hydrofoil through response surface methodology. The cavitation types covered from sheet cavitation to partial and transitional cavity oscillations. We derived regression equations and built response surfaces to illustrate the quantitative relationship between individual factors (obstacle position, cavitation number, and angle of attack) and cavitation dynamic response parameters (cavity length, acoustic intensity, and energy flux). Sheet cavitation was effectively suppressed because the obstacle increased the pressure at the near-wall region. However, the obstacle would induce a shear cavitation when its position was too close to the leading edge of the hydrofoil. Under partial cavity oscillation conditions, the obstacle was consistently performed well in cloud cavitation control. The cavitation dynamic response parameters significantly decreased. Under transitional cavity oscillation conditions, the obstacle cannot suppress the cavitation because the transitional cavity oscillation was likely a system-inherent instability. This research is beneficial for a comprehensive understanding of cavitation control mechanism using an obstacle and for further industrial application of obstacle in hydraulic machinery to control cavitation.

Effects of non-uniform inflow on the spatial and temporal distribution of impeller excitation in axial flow pumps in water tunnels

Jiansheng Zhang,Linlin Cao,Jian Cui,Haikui Ren,Yun Wang,Dazhuan Wu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.10

The effect of non-uniform inflow on the spatial and temporal distribution of impeller excitation is investigated. The experiments are first conducted to verify the hydraulic performance of the axial flow pump and to provide a reference for the accuracy of the numerical simulations. Subsequently, the effect of non-uniform inflow on the spatial and temporal distribution of the flow field and impeller load is investigated. The results indicate that the non-uniform inflow modifies the velocity distribution at the impeller inlet, resulting in alterations in the attack angle and subsequently affecting the radial and circumferential distribution of the impeller load. The extreme difference in the head between the different blades can reach up to 36 % of the total head. Furthermore, velocity pulsation and attack pulsation exhibit more pronounced fluctuations in the low-speed region, and there exists a strong correlation between the amplitude of unsteady forces and the magnitude of the impeller load.

Serum calcium is a novel parameter to assess metabolic syndrome in endometrial carcinoma

Yanying Lin,Jingyi Zhou,Linlin Cao,Juan Hao,Lijun Zhao,Jianliu Wang,Qi Xu 대한부인종양학회 2019 Journal of Gynecologic Oncology Vol.30 No.1

Objectives: To investigate the distribution of serum calcium and the relationship between serum calcium and serum metabolic parameters in endometrial carcinoma (EC) patients. Methods: Retrospective assessment of patients diagnosed with endometrial cancer from Peking University People's Hospital from 2004 to 2009. Clinical characteristics as well as pretreatment serum calcium, albumin, fasting plasma glucose (FPG), serum triglycerides (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and total cholesterol (TC) value were extracted from patient records. Serum calcium was corrected for albumin. Unpaired t test and analysis of covariance were used to compare serum calcium among categorical variables. Simple correlation analyses and partial correlation analyses were used to assess the associations between serum calcium and continuous variables. Results: Two-hundred twenty patients were included in this study. After adjusting for confounders, postmenopausal patients had higher total serum calcium (p=0.002) and albumin-corrected serum calcium (p=0.012) than premenopausal patients, endometrioid endometrial carcinoma (EEC) patients had higher total serum calcium than nonendometrioid endometrial carcinoma (NEEC) patients (p=0.037). Significant positive correlations were found between total serum calcium and FPG (p=0.017), TG (p=0.043), HDL (p=0.042), LDL (p<0.001), and TC (p<0.001) after adjusting for multiple variables, and the corrected serum calcium showed no significant correlation with metabolic parameters. Conclusion: Total serum calcium might be a more sensitive parameter for metabolic syndrome in endometrioid endometrial cancer patients than lipids.

The Interlaminar Mechanical and Impact Properties of Fibre Metal Laminates Reinforced with Graphene

Fanglin Cong,Shuo Wang,Linlin,Meng Cao,Zehui Jia,Zhiqiang Zhou,Xu Cui 한국섬유공학회 2022 Fibers and polymers Vol.23 No.5

Glass fibre aluminium laminate (Glare) is widely used in various fields because of its excellent performance. However, its properties can be further enhanced by adding nanofillers, such as graphene, to the matrix. Graphene is a costeffectivetoughening agent because of its excellent specific strength, economy and good compatibility. The interlaminarmechanical and dynamic impact properties of Glare were improved by uniformly dispersed graphene (0, 0.2, 0.3, 0.5 and1.0 wt%). The interlaminar mechanical properties (short beam shear and single lap test) of the graphene-modified (0.5 wt%)Glare were increased by 42.24 % and 25.65 %, respectively, compared with the pure epoxy resin matrix. At a graphenecontent of 1.0 wt%, the Charpy impact energy and strength increased by 163.58 % and 126.33 %, respectively, and reachedthe maximum value. The microscopic images and schematic diagrams illustrated the toughening mechanism of graphene,including the enhancement of the aluminium/resin and fibre/resin interfaces and the performance of the resin matrix. Thetoughening of the resin matrix was achieved through the formation of a mechanical linkage between the graphene and thematrix, which indicated that more time and energy would be required to destroy it.