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Silica nanoparticles as a high-performance filtrate reducer for foam fluid in porous media
Qichao Lv,Zhaomin Li,Binfei Li,Dashan Shi,Chao Zhang,Binglin Li 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.45 No.-
During the fracturing operations for oils and gases, not only the oil and gas reservoirs, but also the nearbycivil aquifers are often polluted by the invasion of fracturing fluid filtrates. In this study, we investigatedthe potential of silica nanoparticles as a high-performance filtrate reducer for a foam fluid in a porousmedia. First, the three factors affecting filtration reduction using nanoparticles, i.e., surface rheology,foam slipping, and foam stability, were described. Then, the foam filtration through a porous media inthe core was measured using a dynamic fluid-loss device, and the effects of foam quality, pressure drop,and core permeability on the performance of the filtrate reducer were evaluated. The difficulty ofbubbles flowing from a throat to a pore in a porous media was described by resistance gradientcoefficient Cf, which is a combination of surface tension and viscoelastic modulus and increases byadding nanoparticles. Nanoparticles improve the roughness of the SiO2/sodium dodecyl benzenesulfonate foam film surface, thus increasing the slipping resistance Fslip when foams flowon the wall of athroat in a porous media. For the foams in a porous media, the diffusion of bubbles decreased in thepresence of nanoparticles, and the growth rate of gas bubble size also decreased, thus increasing thefoam resistance to gas channeling. The results of core filtration tests indicate that the fluid-loss-controlproperties increased with foam quality ranging from 0 to 85%, and the negative effects of pressure dropand permeability increase to foam filtration were weakened by adding SiO2 nanoparticles. Thus, silicananoparticles can be used as a high-performance filtrate reducer for a foam fluid in a porous media.
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Hybrid DC circuit breaker with reduced fault isolation time and current limiting capability
Qichao Chen,Bingkun Li,Laicheng Yin,Junyuan Zheng,Zhaoyu Duan,Yiqi Liu 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.1
DC circuit breakers (DCCBs) are key pieces of equipment to ensure the safe and stable operation of DC grids. However, current DCCB schemes generally have problems such as a slow fault clearing speed and a poor current limiting effect. This paper proposes a current-limited hybrid DC circuit breaker (CLHCB) that limits fault current and has fast fault isolation, which reduces the capacity requirements. The current limiting inductor in the fault current limiter (FCL) provides the current limiting capability. In addition, the energy dissipation circuit (EDC) is in parallel to reduce the energy dissipation in metal oxide arresters (MOAs) and to decrease the fault isolation time (FIT), which can reduce the thermal effects of MOAs and improve their reliability. Simulation results verify the working principle and advantages of the proposed CLHCB. When compared to an ABB HCB under the same simulation parameters, the CLHCB enables fault current limiting and faster fault isolation. Finally, experiments have verified the effectiveness of the proposed CLHCB.
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Yiqi Liu,Qichao Chen,Ningning Li,Bing Xie,Jianze Wang,Yanchao Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1
In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.
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Effect Factor Analysis of Spraying Quality for Agricultural Chemicals
Wenfeng Sun,Qichao Li,Yongcun Fan,Yanhua Wan,Teng Wang,Baozhong Cong 보안공학연구지원센터 2015 International Journal of u- and e- Service, Scienc Vol.8 No.11
As one of the most important parts of the agricultural work, agricultural chemicals spray is to protect the plants from weeds, pest and bacteria. With development of high efficient agricultural chemicals, the consumption of agricultural chemicals should be controlled within a couple of liter per hectare in theory. But it’s very hard to realize effective use of agricultural chemicals in fact. In this paper, the most effect factors of spray quality such as droplets size, environment temperature, droplets density, nozzle type and spray method were analyzed in agricultural chemicals spray operation. Droplet size effects drift and uniformity of droplet distribution directly. Environment temperature effects drift and uniformity of droplet distribution greatly. Character of nozzle affects spraying quality directly. All research of the paper can offer valuable reference to appropriate application of agricultural chemicals.
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Shuo Yuan,Qichao Wu,Lei Zang,Ning Fan,Peng Du,Aobo Wang,Tianyi Wang,Fangda Si,Jian Li,Xiaochuan Kong 대한척추신경외과학회 2022 Neurospine Vol.19 No.3
Objective: Posterior apophyseal ring fracture (PARF) is an uncommon disorder that is usually accompanied by lumbar disc herniation (LDH). The aim of this study to describe the 8-year experience of performing minimally invasive treatment of PARF, giving particular attention to surgical technique and clinical outcome. Methods: We reviewed 1,324 consecutive patients with LDH seen in our department between 2013 and 2020. Forty-eight patients (3.63%) were enrolled who were diagnosed with PARF associated with LDH and underwent transforminal endoscopic lumbar discectomy (TELD). Mean duration of the final postoperative follow-up was 5.1 years. The control group was comprised of 50 patients diagnosed with LDH without PARF at the same facility. Data on clinical outcomes were analyzed. Results: The mean operation time in the PARF group was 105.4 minutes, which was longer than the mean operation time of the control group (83.9 minutes) (p = 0.001). Surgical complications, including dural tears (6.3%) and surgical instrument rupture (4.2%) were more common in the PARF group (p = 0.025). However, there was no significant difference in the proportion of excellent and good results and recurrence rates between the LDH patients with and those without PARF, respectively. Conclusion: TELD is a safe and effective minimally invasive approach for the treatment of PARF. However, minimally invasive techniques may require longer operation time and steeper learning curve for inexperienced surgeons. The separation and removal of bone fragments, a key step in the procedure, requires patience and care to prevent rupture, residual surgical instruments, and leakage of cerebrospinal fluid.
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Liu, Yiqi,Chen, Qichao,Li, Ningning,Xie, Bing,Wang, Jianze,Ji, Yanchao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1
In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.
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MMC‑modified sub‑module structure with double reverse blocking IGBTs
Yiqi Liu,Zhaoyu Duan,Qichao Chen,Bingkun Li,Mingfei Ban,Zhenjie Li 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.3
In high-voltage direct current (HVDC) systems, among the voltage source converters (VSCs), the modular multilevel converter (MMC) is a popular choice for power transmission. Unfortunately, the conventional half-bridge sub-module (SM) cannot deal with DC faults by itself. Thus, improved SM topologies enabling DC fault ride-through are significant. With this in mind, an MMC-modified SM structure is presented with double reverse blocking IGBTs (DRBSM). When all of the IGBTs in an MMC are blocked, the DRBSM can insert two capacitors in series to the fault circuit to rapidly overcome the DC fault. First, the DRBSM topology and working principle are analyzed. Second, the DRBSM control strategy is illustrated. Third, the device withstand voltage, DC fault ride-through, cost, and loss performance of the DRBSM are presented in detail. Finally, according to simulation results, the DRBSM fault ride-through speed is shown to be as fast as the full-bridge SM, and faster than the clamp double SM. In addition, experimental results validate the feasibility of the proposed DRBSM structure.
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Effects of inlet working condition and heat load on supercritical CO2 compressor performance
Pei Jinze,Zhao Yuanyang,Zhao Mingran,Liu Guangbin,Yang Qichao,Li Liansheng 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8
The supercritical carbon dioxide (sCO2) Brayton power cycle is more effective than the conventional power cycle and is more widely applicable to heat sources. The inlet working conditions of the compressor have a higher influence on their operating performance because the thermophysical properties of the CO2 vary dramatically close to the critical point. The flow in the sCO2 compressor is simulated and the compressor performance is analyzed. The results show that the sCO2 centrifugal compressor operates outside of its intended parameters due to the change in inlet temperature. The sCO2 compressor requires more power as the inlet temperature increases. The compressor power is 582 kW when the inlet temperature is at 304 K. But the power is doubled when the inlet temperature increases to 314 K, and the change in the isentropic efficiency is within 5%. The increase in the inlet temperature significantly reduces the risk of condensation in centrifugal compressors. When the heat load of the sCO2 power system changes, the inlet pressure to the turbine can be kept constant by regulating the rotational speed of compressors. With the increase in rotational speed, the incidence loss and condensation risk increase
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