In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic （where mastic is a kind of fine mixture composed of asphalt binder mixed with fi...In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic （where mastic is a kind of fine mixture composed of asphalt binder mixed with fines and fine aggregates） and air voids, based on three-dimensional （3D） heterogeneous specimen, X-ray computerized tomography （X-ray CT） was used to scan the asphalt specimens to obtain the real internal microstrnctures of asphalt mixture. CT images were reconstructed to build up 3D digital specimen, and the viscoelastic properties of mastic were described with Burgers model The uniaxial creep numerical simulations of three different levels of aggregate gradation were conducted. The simulation results agree well with the experimental results. The numerical simulation of asphalt mixture incorporated with real 3D microstructure based on finite element method is a promising application to conduct research of asphalt concrete. Additionally, this method can increase the mechanistic understanding of global viscoelastic properties of asphalt mixtures by linking the real 3D microstructure.展开更多
This paper focuses on the investigation of an aft mixing chamber diaphragm in a hybrid rocket motor. Both numerical and ex- perimental researches are carried out to study its effects on the motor performances. The hyb...This paper focuses on the investigation of an aft mixing chamber diaphragm in a hybrid rocket motor. Both numerical and ex- perimental researches are carried out to study its effects on the motor performances. The hybrid rocket motor with star fuel grain is utilized. The 90% hydrogen peroxide （HP） oxidizer and hydroxyl terminated polybutadiene （HTPB） based fuel are adopted as propellants. The diaphragm configuration settled in the aft mixing chamber includes four circular-holes with a uni- form circumferential distribution. For both motors with and without the diaphragm, three-dimensional numerical simulations with gaseous combustions considered are carried out to study the flow field characteristics and motor performances. The com- parison results show that the diaphragm can improve the mixing of the oxidizer and fuel. It has evident effect on increasing the motor efflciencies. Two firing experiments are conducted with full scale motors to investigate the effects of the diaphragm. The diaphragm used in the test is composed of a central steel framework and a closed thermal insulation layer. With the dia- phragm employed, the combustion efficiency increases from 93.9% to 97.34% and the specific impulse efficiency increases from 80.77% to 87.28%, which verifies the positive effect of the diaphragm. Both numerical and experimental studies indicate that the scheme of the aft mixing chamber diaphragm proposed in the paper can improve the efficiencies of the hybrid rocket motor obviously.展开更多
基金Project(51038004) supported by the National Natural Science Foundation of China
文摘In order to verify the validity of finite element numerical simulation method for asphalt mixture, which consists of aggregates, mastic （where mastic is a kind of fine mixture composed of asphalt binder mixed with fines and fine aggregates） and air voids, based on three-dimensional （3D） heterogeneous specimen, X-ray computerized tomography （X-ray CT） was used to scan the asphalt specimens to obtain the real internal microstrnctures of asphalt mixture. CT images were reconstructed to build up 3D digital specimen, and the viscoelastic properties of mastic were described with Burgers model The uniaxial creep numerical simulations of three different levels of aggregate gradation were conducted. The simulation results agree well with the experimental results. The numerical simulation of asphalt mixture incorporated with real 3D microstructure based on finite element method is a promising application to conduct research of asphalt concrete. Additionally, this method can increase the mechanistic understanding of global viscoelastic properties of asphalt mixtures by linking the real 3D microstructure.
文摘This paper focuses on the investigation of an aft mixing chamber diaphragm in a hybrid rocket motor. Both numerical and ex- perimental researches are carried out to study its effects on the motor performances. The hybrid rocket motor with star fuel grain is utilized. The 90% hydrogen peroxide （HP） oxidizer and hydroxyl terminated polybutadiene （HTPB） based fuel are adopted as propellants. The diaphragm configuration settled in the aft mixing chamber includes four circular-holes with a uni- form circumferential distribution. For both motors with and without the diaphragm, three-dimensional numerical simulations with gaseous combustions considered are carried out to study the flow field characteristics and motor performances. The com- parison results show that the diaphragm can improve the mixing of the oxidizer and fuel. It has evident effect on increasing the motor efflciencies. Two firing experiments are conducted with full scale motors to investigate the effects of the diaphragm. The diaphragm used in the test is composed of a central steel framework and a closed thermal insulation layer. With the dia- phragm employed, the combustion efficiency increases from 93.9% to 97.34% and the specific impulse efficiency increases from 80.77% to 87.28%, which verifies the positive effect of the diaphragm. Both numerical and experimental studies indicate that the scheme of the aft mixing chamber diaphragm proposed in the paper can improve the efficiencies of the hybrid rocket motor obviously.
