In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characte...In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characteristics of the working processes in the TRPE, corresponding differential equations were established and then simplified by period features of the TRPE. Finally, the major boundary conditions were figured out. The changing trends of mass, pressure and temperature of working fuel in the working chamber during a complete engine cycle were presented. The simulation results are consistent with the trends of an actual working cycle in the TRPE, which indicates that the method of simulation is feasible. As the pressure in the working chamber is calculated, all the performance parameters of the TRPE can be obtained. The major performance indicators, such as the indicated mean effective pressure, power to weight ratio and the volume power, are also acquired. Compared with three different types of conventional engines, the TRPE has a bigger utilization ratio of cylinder volume, a higher power to weight ratio and a more compact structure. This indicates that TRPE is superior to conventional engines.展开更多
Monodispersed MgO microspheres were successfully synthesized by a simple solvothermal method using PEG-400 as solvent. The samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). Th...Monodispersed MgO microspheres were successfully synthesized by a simple solvothermal method using PEG-400 as solvent. The samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The results reveal that the precusor was monoclinic Mg5(CO3)4(OH)2·4H2O and composed of nanosheets with the thickness of about 250 nm. By calcining the precusor at 500 °C for 5 min, cubic MgO with similar morphology was obtained. According to the SEM images, it is found that the volume ratio of PEG-400 to deionized water is considered as a crucial factor in the evolution of the morphology. Based on the SEM images obtained under different experimental conditions, a possible growth mechanism which involves self-assembly process was proposed. The thermal decomposition process of MgO precusor was studied by thermogravimetry-differential thermogravimetry(TG-DTG) at different heating rates in air. Thermal analysis kinetics results show that the most probale mechanism models of MgO precusor are An and D3, respectively. In addition, isothermal prediction was studied to quantitatively characterize the thermal decomposition process.展开更多
An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehen...An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.展开更多
In order to explain the oscillation heat transfer dynamics of closed loop oscillation heat pipe (CLOHP) with two liquid slugs,analysis on the forces and heat transfer process of the partial gas-liquid phase system inv...In order to explain the oscillation heat transfer dynamics of closed loop oscillation heat pipe (CLOHP) with two liquid slugs,analysis on the forces and heat transfer process of the partial gas-liquid phase system involving multiple parameters was carried out,and a new type oscillation heat transfer dynamic model of the CLOHP was set up based on conservation laws of mass,momentum and energy.Application results indicate that its oscillation heat transfer dynamics features depend largely on the filling rate,pipe diameter and difference in temperature.Besides,oscillation intensity and transfer performance can be improved to a large extent by increasing the temperature difference properly and enlarging the pipe diameter within a certain range under a certain filling rate.展开更多
基金Project(7131109)supported by the National Defense Pre-research Foundation of ChinaProject(51175500)supported by the National Natural Science Foundation of China
文摘In order to study the major performance indicators of the twin-rotor piston engine(TRPE), Matlab/simulink was used to simulate the mathematical models of its thermodynamic processes. With consideration of the characteristics of the working processes in the TRPE, corresponding differential equations were established and then simplified by period features of the TRPE. Finally, the major boundary conditions were figured out. The changing trends of mass, pressure and temperature of working fuel in the working chamber during a complete engine cycle were presented. The simulation results are consistent with the trends of an actual working cycle in the TRPE, which indicates that the method of simulation is feasible. As the pressure in the working chamber is calculated, all the performance parameters of the TRPE can be obtained. The major performance indicators, such as the indicated mean effective pressure, power to weight ratio and the volume power, are also acquired. Compared with three different types of conventional engines, the TRPE has a bigger utilization ratio of cylinder volume, a higher power to weight ratio and a more compact structure. This indicates that TRPE is superior to conventional engines.
基金Project(CL11034)supported by the Training Program of Innovation and Entrepreneurship for Undergraduates of ChinaProject(CSUZC2013033)supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,ChinaProject(201210533003)supported by National Training Programs of Innovation and Entrepreneurship for Undergraduates,China
文摘Monodispersed MgO microspheres were successfully synthesized by a simple solvothermal method using PEG-400 as solvent. The samples were characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The results reveal that the precusor was monoclinic Mg5(CO3)4(OH)2·4H2O and composed of nanosheets with the thickness of about 250 nm. By calcining the precusor at 500 °C for 5 min, cubic MgO with similar morphology was obtained. According to the SEM images, it is found that the volume ratio of PEG-400 to deionized water is considered as a crucial factor in the evolution of the morphology. Based on the SEM images obtained under different experimental conditions, a possible growth mechanism which involves self-assembly process was proposed. The thermal decomposition process of MgO precusor was studied by thermogravimetry-differential thermogravimetry(TG-DTG) at different heating rates in air. Thermal analysis kinetics results show that the most probale mechanism models of MgO precusor are An and D3, respectively. In addition, isothermal prediction was studied to quantitatively characterize the thermal decomposition process.
基金Project(NR2013K04) supported by Beijing Key Lab of Heating,Gas Supply,Ventilating and Air Conditioning Engineering,ChinaProject(20130909) supported by the Higher School Science and Technology Development Fund of Tianjin,China
文摘An ejector of low NO~ burner was designed for a gas instantaneous water heater in this work. The flowing and mixing process of the ejector was investigated by computational fluid dynamics （CFD） approach. A comprehensive study was conducted to understand the effects of the geometrical parameters on the static pressure of air and methane, and mole fraction uniformity of methane at the outlet of ejector. The distribution chamber was applied to balance the pressure and improve the mixing process of methane and air in front of the fire hole. A distribution orifice plate with seven distribution orifices was introduced at the outlet of the ejector to improve the flow organization. It is found that the nozzle exit position of 5 mm and nozzle diameter d 〉1.3 mm should be used to improve the flow organization and realize the well premixed combustion for this designed ejector.
基金Project(531107040300)supported by the Fundamental Research Funds for the Central Universities in ChinaProject(51176045)supported by the National Natural Science Foundation of China
文摘In order to explain the oscillation heat transfer dynamics of closed loop oscillation heat pipe (CLOHP) with two liquid slugs,analysis on the forces and heat transfer process of the partial gas-liquid phase system involving multiple parameters was carried out,and a new type oscillation heat transfer dynamic model of the CLOHP was set up based on conservation laws of mass,momentum and energy.Application results indicate that its oscillation heat transfer dynamics features depend largely on the filling rate,pipe diameter and difference in temperature.Besides,oscillation intensity and transfer performance can be improved to a large extent by increasing the temperature difference properly and enlarging the pipe diameter within a certain range under a certain filling rate.
