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- 저자 : Chengtao Yu (검색결과 5 건)
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Chengtao Yu,Yuemei Sun,Hongchang Wang,Fan Shi,Yu Chen,Wentao Shan 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10
In this paper, a radial and axial integrated auxiliary bearing (RAIAB) device which can eliminate all radial and axial protective clearances after the rotor dropping is proposed to improve the reliability of the active magnetic bearing systems. In the proposed RAIAB, a strategy that the rotor end and the inner bushing are machined into conical surface is adopted so that the radial and axial clearances between the rotor and the inner bushing can be eliminated simultaneously when the inner bushing moves along the axial direction. In order to research the influence of the conical degree of the inner bushing on the performance of the RAIAB, the preliminary prototype experimental rig is developed and the cases of a 5 degree of freedom AMB rotor dropping on RAIABs at maximum speed of 30000 rpm are tested. The experimental results show that the RAIAB installed with a 30-conical degree inner bushing can successfully eliminate all protective clearances after the AMB rotor drops. However, the RAIAB installed with a 45-conical degree inner bushing is not able to eliminate clearance when the dropping speed of the rotor exceeds 18000 rpm.
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Study on the added mass effect in squeeze-film dampers
Hongchang Wang,Wentao Shan,Chengtao Yu 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.6
Squeeze-film dampers (SFD) are used as indispensable bearings in many rotating machines to suppress lateral vibration and enhance stability. The kinetic energy of the damping fluid is sometimes greater than that of SFD’s journal. Therefore, the influence of the damping fluid must be considered in establishing a dynamic model of a rotor–bearing system. A concept that involves the added mass of the damping fluid is proposed in this work, and the calculation formula is derived based on laminar flow theory and the mean-square speed of the fluid. The unbalance responses of a rotor–bearing system are solved by numerical iteration and with the transfer matrix method. The results calculated with and without added mass are compared. Experimental results indicate that introducing the added mass of the damping fluid into a dynamic model is effective.
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Yili Zhu,Yanhong Zhang,Chengtao Yu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6
A new-type active touchdown bearing (TDB) system integrated with a centering device to eliminate the protective clearance after rotor drop in an active magnetic bearing (AMB) system is proposed. A rotor dynamic model is established on the basis of rigid rotor theory. A collision model between the support base and outer race of the ball bearing and a real-time ball bearing elastic supporting force model are established on the basis of Hertz contact theory. The dynamic model of the new-type TDB is established on the basis of vibration theory. Using these established theoretical models, the dynamic responses after rotor drops onto the new-type TDB are simulated and compared with the responses after rotor drops onto traditional TDB. Relevant experiments are conducted on an AMB test platform to verify the simulation results. The results show that the proposed new-type TDB can rapidly eliminate the protective clearance after rotor drop and can thus effectively reduce the following rotor vibrations and impacts.
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Wang Yinghui,Zhang Yanan,Wang Jiangfeng,Kang Chengtao,Hu Gengwang,Guo Yi,Chen Jie,Yang Lijun,Wang Yu 한국응용곤충학회 2023 Journal of Asia-Pacific Entomology Vol.26 No.4
The black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), isomnivorous andwidely distributed in the world. Black soldier flies usually colonize corpse at a relatively late stage and have a longer developmental time compared to other flies. It can serve as a good supplementary indicator for estimating a longer minimum postmortem interval (PMI min ) in forensic investigations. In this paper, the development of H. illucens was investigated at six constant temperatures between 19 and 34 ◦ C. Under temperatures of 19, 22, 25, 28, 31, and 34 ◦ C, the mean developmental time from eggs to adults was 90.96, 58.29, 54.61, 42.33, 32.33 and 34.52 days, respectively. Developmental time and accumulated degree days results were used to construct thermal sum mation model and isomorphen diagram. The calculated values of lower developmental thresholds and thermal summation constant estimated by a linear model were 11.88 ◦ C and 650.89 degree days, respectively. Through a nonlinear model, the upper lethal developmental threshold temperature, intrinsic optimum temperature and lower developmental thresholds were estimated to be 35.18, 20.50 and 13.17 ◦ C, respectively. A growth curve, an equation and isomegalen diagram based on them show the relationship between developmental time and larval body length. The larval body length increased with increased developmental time and eventually pla teaued, revealing an S-shape growth curve. These results provide important basic developmental data for H. illucens, which can be used to estimate the PMI min .
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Li Liangliang,Zhang Yanan,Chen Yang,Guo Yi,Wang Yinghui,Hu Gengwang,Kang Chengtao,Jiangfeng Wang,Wang Yu 한국응용곤충학회 2023 Journal of Asia-Pacific Entomology Vol.26 No.2
Sarcophaga peregrina Robineau-Desvoidy, 1830 (Diptera: Sarcophagidae) is a widely distributed species in the Palearctic, Oriental and Australian regions. Numerous studies and case reports have confirmed the value of this species in forensic investigations, but methods for estimating the age of the intrapuparial period of this species are lacking. In this study, S. peregrina pupae were sampled at 16 ◦ C, 19 ◦ C, 22 ◦ C, 25 ◦ C, 28 ◦ C, 31 ◦ C, and 34 ◦ C. Morphological changes within the puparium were observed under a stereomicroscope. The results of the study showed that S. peregrina could complete its intrapuparial development at each of the seven tested constant temperatures. As the temperature increased, the average minimum duration of the intrapuparial period of S. peregrina decreased from 706.7 ± 28.1 h at 16 ◦ C to 170.7 ± 4.6 h at 34 ◦ C. The intrapuparial morphological changes of S. peregrina can be divided into 12 sub-stages. While some structures such as the compound eyes, mouthparts, antennae, thorax, legs, wings, and abdomen can be used individually to estimate intrapuparial age, we observed all these structures with local magnification photographs and classified the developmental process of these structures into 6–11 stages. The time range for the appearance of each sub-stage or structure was recorded in detail. The results of this study provide important basic data for estimating the minimum postmortem interval using the intrapuparial morphology of S. peregrina.
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