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- 저자 : Zheng Xinqian (검색결과 5 건)
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Changes in distribution and morphology of Tamarix ramosissima nebkhas in an oasis-desert ecotone
Chaofan Li,Fan Yang,Xinqian Zheng,Zhangyong Han,Honglin Pan,Chenglong Zhou,Chunrong Ji 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.5
In the oasis-desert ecotone, nebkhas are of great importance for blocking the intrusion of shifting sand and maintaining the ecological security of oases. The morphological characteristics of nebkhas have been widely researched. However, their spatial distribution and morphological variation with the environment remain unclear. In this paper, we systematically analyzed the spatial distribution pattern, morphological changes, and potential indicative significance of Tamarix ramosissima nebkhas (that is, nebkhas formed around T. ramosissima) in a typical oasis-desert ecotone in Northwest China. Our results showed that the intensity of aeolian activities increased from the inside to the outside of the ecotone, and only T. ramosissima shrubs with high tolerance to aeolian activities could survive. Moreover, from the inside to the outside of the ecotone, the density of the T. ramosissima nebkhas decreased, their size increased, and spatial distribution shifted from aggregation to random. The T. ramosissima shrub can trap aeolian transport and protect nebkhas, leading to sand accumulation in the space between, and leeward edges of, the shrubs. Wind erosion mainly occurs to the windward side and along the sides of the nebkhas. Further, the protective effect of the shrub gradually increased with its growth in a year, resulting in the gradually changed of nebkha surface from wind erosion to sand accumulation, and the nebkha volume showed a fluctuating state of first decreasing and then increasing. This indicates that wind erosion and sand accumulation on the nebkha surface were closely related to the growth cycle of the shrub. In addition, nebkhas exhibited a spatial pattern of growth, inside of the ecotone, to degradation, outside of the ecotone. These results indicate that we should focus on the outside of the ecotone to ensure the ecological stability of oases.
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Study of Mechanism of Counter-rotating Turbine Increasing Two-Stage Turbine System Efficiency
Liu, Yanbin,Zhuge, Weilin,Zheng, Xinqian,Zhang, Yangjun,Zhang, Shuyong,Zhang, Junyue Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.3
Two-stage turbocharging is an important way to raise engine power density, to realize energy saving and emission reducing. At present, turbine matching of two-stage turbocharger is based on MAP of turbine. The matching method does not take the effect of turbines' interaction into consideration, assuming that flow at high pressure turbine outlet and low pressure turbine inlet is uniform. Actually, there is swirl flow at outlet of high pressure turbine, and the swirl flow will influence performance of low pressure turbine which influencing performance of engine further. Three-dimension models of turbines with two-stage turbocharger were built in this paper. Based on the turbine models, mechanism of swirl flow at high pressure turbine outlet influencing low pressure turbine performance was studied and a two-stage radial counter-rotation turbine system was raised. Mechanisms of the influence of counter-rotation turbine system acting on low-pressure turbine were studied using simulation method. The research result proved that in condition of small turbine flow rate corresponding to engine low-speed working condition, counter-rotation turbine system can effectively decrease the influence of swirl flow at high pressure turbine outlet imposing on low pressure turbine and increases efficiency of the low-pressure turbine, furthermore increases the low-speed performance of the engine.
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Adaptive flow optimization of a turbocharger compressor to improve engine low speed performance
Yangjun Zhang,Chenfang Wang,Zheng Xinqian,Weilin Zhuge,Yulin Wu,Jianzhong Xu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6
To improve the engine overall performance, an adaptive flow optimization procedure is proposed in this paper to synthesize turbocharger compressor optimum designs. Two objective functions are involved in the adaptive optimization. They are the traditional compressor design and the compressor design with consideration of improving engine overall performance. The two-step decomposition approach is chosen to generate optimum designs. The optimized designs not only satisfy turbomachinery and engine constraints but also have optimum objective function values in the two fields. Performance sensitivity analysis of compressor main design variables is performed for the flow optimization design process. A centrifugal compressor is redesigned for a turbocharged gasoline engine, as an example, based on the adaptive flow optimization process. The calculating results show a more than 5% increase of isentropic efficiency in comparison with the base line compressor, resulting in a more than 19% increase of engine torque at low speed conditions.
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Binyang Song,Weilin Zhuge,Rongchao Zhao,Xinqian Zheng,Yangjun Zhang,Yong Yin,Yanting Zhao 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.6
A Brayton cycle waste heat recovery (WHR) system for turbocharged diesel engines was proposed and the performance of a diesel engine integrated with the proposed system was investigated. The waste heat recovery system is integrated with the turbocharging system of diesel engines, using the turbocharger compressor as the Brayton cycle compressor. The engine cycle simulation code GT-Suite 7.0was used to investigate the performance of a diesel engine integrated with the WHR system. A Brayton cycle turbine was designed and its performance was simulated with a through-flow model. The turbocharging system of the original engine was modified and the energy flow distribution between the diesel cycle and the Brayton cycle was optimized. Results show that the fuel economy of the diesel engine can be improved by 2.6% at high engine speed and 4.6% at low engine speed under engine full load operating conditions when equipped with the Brayton cycle WHR system. The influence of turbocharger parameters on the WHR engine performance was invesgated.
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Study of Mechanism of Counter-rotating Turbine Increasing Two-Stage Turbine System Efficiency
Yanbin Liu,Yangjun Zhang,Weilin Zhuge,Xinqian Zheng,Shuyong Zhang,Junyue Zhang 한국유체기계학회 2013 International journal of fluid machinery and syste Vol.6 No.3
Two-stage turbocharging is an important way to raise engine power density, to realize energy saving and emission reducing. At present, turbine matching of two- stage turbocharger is based on MAP of turbine. The matching method does not take the effect of turbines' interaction into consideration, assuming that flow at high pressure turbine outlet and low pressure turbine inlet is uniform. Actually, there is swirl flow at outlet of high pressure turbine, and the swirl flow will influence performance of low pressure turbine which influencing performance of engine further. Three-dimension models of turbines with two-stage turbocharger were built in this paper. Based on the turbine models, mechanism of swirl flow at high pressure turbine outlet influencing low pressure turbine performance was studied and a two-stage radial counter-rotation turbine system was raised. Mechanisms of the influence of counter-rotation turbine system acting on low-pressure turbine were studied using simulation method. The research result proved that in condition of small turbine flow rate corresponding to engine low-speed working condition, counter-rotation turbine system can effectively decrease the influence of swirl flow at high pressure turbine outlet imposing on low pressure turbine and increases efficiency of the low-pressure turbine, furthermore increases the low-speed performance of the engine.
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