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Exergy-based Energy Efficiency Evaluation Model for Machine Tools Considering Thermal Stability
Ben-jie Li,Huajun Cao,Bernard Hon,Lei Liu,Xi Gao 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.2
Machine tools, as the extensively used basic equipment of manufacturing industry, are characterized by intensive and inefficient energy consumption. With the launch and implementation of ISO 14955-1, energy efficiency has become an important criterion for machine tool evaluation. However, most ongoing research on energy efficiency evaluation of machine tools emphasizes on workpiece material removal energy efficiency and rarely considers energy consumption needed to ensure machining accuracy and accuracy consistency, especially energy consumption for thermal stability control of machine tools. In light of this, an exergy analysis based approach is presented to assess the comprehensive energy efficiency of machine tools, including energy consumption for material removal and thermal stability control. The key performance indexes of exergy efficiency, exergy destruction, and specific exergy consumption are analyzed. The feasibility of the proposed approach was demonstrated by a case study, in which the comprehensive energy efficiency of a machine tool was found to be 21.57% instead of 14.38% of material removal energy efficiency. The proposed method is more effective to evaluate the comprehensive energy efficiency, to support designers to design high-efficient machine tool and users to operate machine tool for green and precision machining.
( Gang Zhou ),( Long Jie Li ),( Qing Shan Shi ),( You Sheng Ouyang ),( Yi Ben Chen ),( Wen Feng Hu ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.12
Citrobacter sp. is a cause of significant opportunistic nosocomial infection and is frequently found in human and animal feces, soil, and sewage water, and even in industrial waste or putrefaction. Biofilm formation is an important virulence trait of Citrobacter sp. pathogens but the process and characteristics of this formation are unclear. Therefore, we employed in vitro assays to study the nutritional and environmental parameters that might influence biofilm formation of C. werkmanii BF-6 using 96-well microtiter plates. In addition, we detected the relative transcript levels of biofilm formation genes by RT-PCR. Our results indicated that the capacity of C. werkmanii BF-6 to form biofilms was affected by culture temperature, media, time, pH, and the osmotic agents glucose, sucrose, NaCl, and KCl. Confocal laser scanning microscopy results illustrated that the structure of biofilms and extracellular polysaccharide was influenced by 100 mM NaCl or 100 mM KCl. In addition, nine biofilm formation genes (bsmA, bssR, bssS, csgD, csgE, csgF, mrkA, mrkB, and mrkE) were found to contribute to planktonic and biofilm growth. Our data suggest that biofilm formation by C. werkmanii BF-6 is affected by nutritional and environmental factors, which could pave the way to the prevention and elimination of biofilm formation using proper strategies.
Xiao Yang,Huajun Cao,Yong-peng Chen,Li-Bin Zhu,Ben-jie Li 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.2
High-speed dry hobbing is the dominating green technique for gear hobbing owing to its high productivity and environmental friendliness. However, a large amount of cutting heat is generated during the machining process due to the absence of metalworking fluids and the adoption of high cutting speed. A better understanding of chip heat-carrying capacity for high-speed dry hobbing is quite necessary when aiming to reduce the influence of cutting heat on machining precision. In this paper, an analytical model is established to quantitatively determine the chip heat-carrying capacity of high-speed dry hobbing. According to the progressive heat transfer characteristic of high-speed dry hobbing, cutting heat generation and transmission are analyzed. 3D chip geometry is numerically calculated by modeling the complex hob geometry and the interrelated kinematic relations of high-speed dry hobbing. Based on the 3D chip geometry and the specific cutting energy, chip heat-carrying capacity model is developed considering three heat sources. In this model, chip heat partition is experimentally determined by calorimetric method. With the help of the developed model, chip heat-carrying quantity and chip heat-carrying efficiency are discussed by investigating their influence factors (hob rotation speed, axial feed, feed method, chip removal time and hob geometry).