Papers by Author: Hong Sun

Abstract: Rock tunnel boring machine is one of the main machineries and equipments for underground engineering, and the failure of its disc cutter is the main failure form of this machinery. The experiment on the failure and wear of the disc cutter is difficult. In this paper, a rock hob test-bed is designed, and the hydraulic-driven system of its disc cutter of rock hob test-bed is simulated; the effect of load and flow rate of hydraulic oil in this hydraulic system on characteristics of this disc cutter system is analyzed. The results show that the vertical movement speed of disc cutter is directly proportional to the flow rate; the effect of the load on this speed and the vertical pressure can be ignored; the delay time of the movement of the disc cutter to the flow rate of hydraulic oil is proportional to the load. These results are very helpful to the structure optimization of disc cutter system of rock tunnel boring machine and the improvement of working efficiency.

Abstract: The effects of temperature on electricity performance and microbial activity were investigated in single-chamber microbial fuel cell with proton exchange membrane (S-PEM-MFC) using glucose as substrate with phosphate buffer solution(PBS). The results showed that S-PEM-MFC able to adapt to a wide temperature range of 11, 18, 25, 30 and 35°C. The open circuit voltage, polarization, power density and microbial activity of S-PEM-MFC were increased with increasing temperature from 11 to 30°C. The maximum power density were 193.8mW∙m-3 at 30°C. Compared to 30°C, the battery open circuit voltage increased by only 4.8% at 35°C, while the polarization and power density is almost the same. These results demonstrate that according to the principle of economy which 30°C should be the optimal operating temperature of S-PEM-MFC.

Abstract: Electrochemical impedance (EI) plays a very important role on the characteristics of proton exchange membrane (PEM) fuel cell. In this paper, the effects of the cell temperature and the humidification temperature on the electrochemical impedance are analyzed by the equivalent circuit. The results show: when the cell temperature is higher than the gas humidification temperature, ohms impedance and Faraday impedance increase markedly, and electric double layer in the PEM fuel cell inclines to the specialty of capacitive reactance; the more than the cell temperature the gas humidification temperatures is, the more the extent of specialty of capacitive reactance the electric double layer shows. These results are very helpful to understand the operating principle of PEM fuel cell and improve its performance.

Abstract: Hob plays an important role in the efficiency of Tunnel Boring machine (TBM). In this paper, a rock hob test-bed is designed and developed by the software of SolidWorks, and analysis of force and deformation of the test-bed is carried by the finite element method.The new rock hob test-bed includes the framework、moving workbench and its hydraulic system、hob saddle system and its hydraulic system, and measurement and control system. The improvement methods of the structure to decrease the maximum stress are showed in this paper. The research shows that the structural design of the rock hob test-bed is reasonable; its function meets experimental requirements of rock cutting; in the case of maximum load, the stress and deformation of the rock hob test-bed are less than their allowable value of materials. The research results are very helpful to understand the working mechanism and improving the structure design of the cutter-head of TBM.

Abstract: With the development of Micro-electro-mechanical systems (MEMS) and Nano-electro-mechanical systems (NEMS), dimension of their parts is required to nanometer scale, and the characteristics of machined-surface of nano-scale parts affect strongly its application. Surface relaxation plays an important role to the characteristics of the machined-surface. In this paper, machined-surface of monocrystal copper used as the specimen of surface relaxation, and its surface relaxation process is simulated. The influences of surface relaxation on surface energy, atom array, surface roughness, surfaces hardness and surface residual stress of the monocrystal copper are analyzed. Results show that surface energy and surface hardness decrease due to relaxation; work-hardening can’t be completely eliminated by the relaxation; compression residual stress of the machined surface is changed gradually to tensile stress during the relaxation. These research results are very helpful to the application of nano-machined parts.

Abstract: SiC ceramics have been widely used in a variety of areas due to the excellent physical and chemical properties. However, the process of SiC ceramics is difficult and high-cost, molecular simulation is an effective and feasible method to study the nano-process of SiC ceramics. In this paper, a molecular model is presented to simulate the stress and energy in the nano-cutting of SiC ceramics. The influences of the cutting depth and cutting speed on the kinetic energy and potential are analyzed. The results show that potential energy increases with the decrease of the cutting depth. Kinetic energy increases with the increase of the cutting speed. The results are very helpful for improvement the level of ultra-precision processing and nano-processing of brittle ceramics.

Abstract: Electricity can be generated during the wastewater treatment by microbial fuel cell (MFC). Effect of the anode pretreatment method, anode modification and electronic media in anolyte on electricity generation of a single chamber microbial fuel cell (SCMFC) with an air cathode was investigated by performance measurement of the MFC during one cycle of generating electricity. Results show that the discharge time of MFCs with stainless steel anode pretreated by NH4Cl and HCl is longer than that with anode pretreated by the distilled water and NaOH; the performance of MFC with anode pretreated by NH4Cl is the best; comparison with stainless steel anode and adhere activated carbon, the current of MFC with the stainless steel anode adhere the carbon fiber is the maximum and its Coulombic efficiency is the highest; The electricity generation characteristics of the MFC with the anode adhered carbon fiber and pretreated by NH4Cl and the anolyte added the electronic media is the best. The action of the electronic medium and the NH4Cl on the MFC is synergism. It's of great significance that the research results improve the performance of MFC by anode pretreatment.

Abstract: Rock tunnel boring machine is one of the main machineries and equipments for underground engineering ,and the failure of tool systems is the main failure form of this machinery. Rock hob test-bed is the only testing equipment for tool failure and wear. In this paper, the hydraulic-driven system of the rock hob test bench is designed and simulated, and the effect of load and flow rate of hydraulic oil in this hydraulic system on characteristics of this test-bad is analyzed. The results show that the horizontal movement speed of test bench is directly proportional to the flow rate, but the effect of the load on this speed can be ignored; the delay of the movement of the test bench are proportional to the load. These results are very helpful to the structure optimization of tool system and the improvement of working efficiency.

Abstract: Cathode catalyst layer plays an important role in PEMFC. Electrochemical reaction in cathode catalyst layer is a control process for the performance in PEMFC. In this paper, oxygen reduction reaction (ORR) is studied by molecular simulations based on a series pathway which consist of four steps. We calculated the free energy of four steps respectively by molecular simulations. Comparing free energy of our steps, we found that the fourth step can release more energy than the other steps. At the same time, we found that the energy released in ORR is decreased with the increase of temperature. The process of the first step in the series pathway release less energy than that of other steps. The results are very helpful for optimization of construction in the cathode and improving performance of PEM fuel cell.

Abstract: A two-phase flow, multi-component model has been optimized for a PEM (Proton Exchange Membrane) Fuel Cell. The modeling domain consists of the membrane, two catalyst layers, two diffusion layers, and two channels. Both liquid and gas phases are considered in the entire cathode and anode, including the channel, the diffusion layer and the catalyst layer. The Gravity effect on liquid water was considered in channels. Typical two-phase flow distributions in the cathode gas channel, gas diffuser and catalyst layer are presented. Source term and porosity term were optimized. Based on the simulation results, it is found that two-phase flow characteristics in the cathode depend on the current density, operating temperature, and cathode and anode humidification temperatures. Water mass fraction for the fuel cell with anode upward is higher than that the case with cathode-upward. Liquid water with the case of cathode-upward blocks pores in the gas diffuser layer leading to increasing the concentration polarization. Gravity of liquid water exerts the effect on the water mass fraction in the cathode.